Posts Tagged ‘SMT’

Monday, December 16th, 2024

What is solder paste inspection? In simple terms, solder paste inspection is the process of inspecting and evaluating the quality, volume, shape, position and other parameters of solder paste printed on PCB. As the key material for connecting electronic components to PCB, the quality of solder paste printing directly determines the quality of soldering, which in turn affects the electrical and mechanical properties of PCBA.

How does solder paste inspection work?

The working principle of SPI solder paste inspection equipment is mainly based on optical principles and laser triangulation technology. The equipment irradiates the soldering surface through a camera and a light source to obtain an image of the solder paste, and then detects and analyzes the shape, size, position, etc. of the solder paste through image processing technology to determine the quality of the solder paste and the welding effect.

Specifically, when the solder paste is scanned by a laser, the laser emits a laser, which is reflected and focused by the lens to irradiate the laser onto the solder paste. Due to the reflection of the solder paste, a part of the laser is reflected back and captured by the camera. By calculating the time difference between laser emission and reception, parameters such as the height and area of the solder paste can be determined.

Specific steps and principles of SPI solder paste detection

Image acquisition: Use a high-definition camera and light source to take pictures of the solder paste on the pad on the PCB surface to collect images.

Image processing: Analyze and calculate the shape, size, position and other parameters of the solder paste through image processing algorithms, and compare them with previous standard data.

Defect detection: Through comparative analysis, it is determined whether the printing has defects, such as solder paste offset, unevenness, less tin or more tin, etc.

Advantages of SPI solder paste detection

Reduce the unqualified rate: The introduction of SPI can effectively reduce the unqualified rate of the original finished PCB by more than 85%, and significantly reduce the cost of rework and scrap by more than 90%.

Improve the pass rate: Used in conjunction with AOI, through real-time feedback and optimization of the SMT patch proofing production line, the production quality can be more stable, and the unstable trial production stage that must be experienced when introducing new products can be greatly shortened.

Make up for the shortcomings of traditional inspection: 3D inspection effectively makes up for the shortcomings of traditional inspection methods, especially for the inspection of micro components.

Reduce bad situations: Through process control, minimize the bad situations of components after the furnace.

Ensure printing quality: It can effectively ensure good solder paste printing quality and greatly reduce the possible defective rate of finished products.

What does solder paste inspection do?

Solder paste inspection has the following main functions:

Ensure welding quality: The amount and shape of solder paste directly affect the welding effect. Through inspection, it can ensure that the amount of solder paste is moderate, avoid short circuits caused by too much solder paste, or problems such as cold soldering and open circuits caused by too little solder paste, thereby improving the reliability of solder joints and the electrical performance of products.

Optimize the production process: Solder paste inspection can promptly detect problems in the solder paste printing process, such as printing position offset, tinning, etc. This helps to adjust and calibrate the printing equipment, make the printing process more accurate and stable, and improve production efficiency.

Ensure product consistency: When mass-producing electronic products, solder paste inspection can ensure that the solder paste state on each circuit board is relatively consistent. This can keep the product’s soldering quality at a stable level, reduce product quality fluctuations, and improve the overall quality and consistency of the product.

How to measure solder paste height?

In SMT (surface mount technology), there are several main methods for measuring solder paste height:

Laser scanning method: Using the principle of laser triangulation, the laser beam scans the solder paste surface and calculates the solder paste height by the angle change of the reflected light.

Microscope method: By adjusting the focal length of the microscope, the focal plane coincides with the solder paste surface, and the height information at this time is measured using the optical system.

Mechanical contact measurement method: Use a measuring instrument with a high-precision probe to contact the solder paste surface through the probe, and convert the displacement into an electrical signal to determine the solder paste height.

What does AOI mean in inspection?

AOI is automatic optical inspection, which uses cameras and optical components to obtain images of the PCB of the object being inspected, and then analyzes these images through image processing algorithms. These algorithms compare the actual image with the pre-set standard image or rules to identify various features on the surface of the object, such as the position, shape, size of the component, and whether the quality of the solder joint meets the requirements.

Principle and process of AOI detection

Image acquisition: The AOI detection system collects image data on the surface of the product through a camera or sensor, including various details, components and connecting parts.

Image processing: The received image data is processed by an image processing algorithm to remove interference, enhance image quality, and extract key information for subsequent analysis.

Defect identification: Using pre-set models and rules, key features in the image are compared and analyzed to identify defects, misalignment or missing problems on the surface of the product.

Alarm and classification: Once an abnormality is found, the AOI system will trigger an alarm mechanism and classify the defect type for subsequent processing and repair.

AOI detection systems are widely used in electronic manufacturing, printing industry and other fields. In electronic assembly production lines, it is used to detect PCB boards, solder joints, component positions, etc. to ensure product quality and reliability.

What is the difference between AOI and SPI?

AOI (Automated Optical Inspection) and SPI (Solder Paste Inspection) have the following main differences in SMT (Surface Mount Technology) processing:

1. Different inspection objects:

AOI mainly inspects components and solder joints during SMT processing, and detects common errors such as component misalignment, reversal, missing, and redundant, as well as defects after soldering such as cold soldering and bridging.

SPI focuses on the quality assessment of solder paste printing. By measuring the volume, area, height and other parameters of solder paste, it evaluates the printing quality of solder paste and ensures the correct printing of solder paste.

2. Different inspection principles:

AOI uses optical principles to analyze images on circuit boards and identifies defects through image processing algorithms. It uses a high-resolution camera to capture images of PCBAs and compares them with preset standard templates.

SPI evaluates the printing quality of solder paste by measuring various parameters of solder paste, and uses 3D imaging technology to capture the three-dimensional shape of solder paste and compares it with standard data.

3. Different detection timing:

AOI usually performs detection after component placement and welding. It can detect multiple welding points at one time after welding. The detection speed is fast and the impact on production efficiency is relatively small.

SPI performs detection immediately after solder paste printing. Since it needs to be detected immediately after solder paste printing, it has a greater impact on production efficiency.

4. Application scenarios and advantages:

AOI is suitable for high-demand SMT processing production lines. It can quickly and accurately detect a variety of defects and ensure the quality stability of circuit boards.

SPI is crucial to ensure the quality of solder paste printing, directly affects the subsequent placement and welding effects of components, and is suitable for production lines that require high-precision solder paste printing.

What are the defects of SPI?

The defects of 3D SPI (Surface Inspection) mainly include the following aspects:

Low laser resolution: The laser resolution of 3D SPI is generally at the level of 10-20um, which may not be ideal for precise circuit board detection.

Repeatability accuracy is affected: Since each sampling can only provide information of one point, the repeatability accuracy of 3D SPI may be affected.

Sensitive to external vibration: External vibration has a great impact on the detection effect of 3D SPI, and additional stabilization measures may be required to ensure the accuracy of the detection.

Light conditions: The equipment relies on the principle of optical imaging for detection, so it has high requirements for the light conditions of the detection environment and needs to work under stable and uniform lighting conditions to ensure image quality and detection accuracy.

Relatively slow speed: Compared with some other detection technologies, 3D SPI may be slower.

How long can solder paste sit before reflow?

Before the reflow process, the solder paste needs to stay for a period of time to adapt to the environment and ensure the reliability and quality of the solder joints. The optimal dwell time is affected by various factors, such as the freshness of the solder paste, recycled solder paste, ambient temperature and humidity.

The length of the dwell time directly affects the viscosity and fluidity of the solder paste, thereby determining the solder joint morphology and reliability. If the dwell time is too short, there may be gaps and cracks in the solder joint, which affects its reliability. If the dwell time is too long, the surface tension of the solder joint will increase, resulting in irregular morphology on the solder joint surface, which affects the power-on performance of the circuit.

In general, the best dwell time is between 4 and 8 hours. It should be noted that too long or too short a dwell time will affect the solder joint morphology and reliability. Therefore, in specific applications, it is necessary to select the best solder paste dwell time according to actual conditions.

In short, solder paste detection, as a key link in PCBA production, plays a vital role in ensuring the quality and performance of electronic products. Its detection methods cover visual inspection, 2D detection, and advanced 3D detection, each with its own advantages and disadvantages and applicable scenarios, and is a key line of defense to ensure the quality and performance of electronic products.

Soldering Defects

Soldering defects are issues that arise when joints do not meet the expected quality standards. These defects can impact the functionality, reliability, and longevity of a product.

Some typical issues include software design flaws, overheating, incorrect component placement, and power supply issues. Every manufacturer should be aware of these potential pitfalls to ensure reliable and efficient PCB assembly.

A Comprehensive Analysis of Soldering Defects

Why Soldering Defects Occur?

Soldering defects can occur during the assembly process, potentially leading to wasted resources, damaged reputation, product malfunctions, and most critically, loss of time—frustrating both manufacturers and clients. However, by understanding common PCB failure causes, you can address them quickly and effectively.

‌‌Poor Solderability of Holes Vias

Poor solderability of holes can lead to soldering defects, affecting the parameters of components in the circuit and causing unstable connections between components and inner layers in multilayer boards. This can result in the failure of the entire circuit.

Soldering Temperature

The soldering temperature, whether too high or too low, and inadequate surface cleanliness can affect the soldering quality. When the temperature is too high, the solder spreads quickly and is prone to oxidation, leading to defects. When the temperature is too low, the solder may not fully melt, resulting in weak joints.

Flux Issues

The quality and application of flux also impact soldering quality. Insufficient or poor-quality flux can cause poor wetting, resulting in weak and dull solder joints. Excessive flux may lead to overheating, causing rough joint surfaces.

Solder Issues

The quality and fluidity of the solder directly affect the soldering outcome. Poor-quality solder or solder with low fluidity can lead to weak and dull joints, or defects where the solder covers less than 80% of the pad.

PCB Design Issues

Poor PCB design can also result in soldering defects. For example, excessively long traces can increase impedance and noise, affecting soldering quality. Components generating heat without proper heat dissipation can also lead to soldering issues.

Operational Issues During Soldering

Problems such as insufficient soldering time, improper temperature control, or loose component leads during soldering can all result in defects.

How many types of soldering defects are there?

There are several types of soldering defects that can occur during the PCB assembly process. Here is a list of common soldering defects:

Cold Joints
Bridging
Insufficient Solder
Solder Balls
Voids
Cracked Joints
Non-wetting
Tombstoning
Pin Holes or Blow Holes
Oxidation Defects
De-wetting
Component Misalignment
Solder Splashes
Excessive Solder

How Do You Troubleshoot Soldering? -One by One

Cold Joints

Cold joints occur when the solder doesn’t heat properly, resulting in weak, dull, and rough connections. To prevent this, use a soldering iron with adequate power and maintain the correct soldering temperature (typically between 350°C to 400°C for leaded solder). Ensure that both the pad and component lead are evenly heated before applying solder. The solder should flow smoothly around the joint. Using a clean, well-tinned soldering iron tip ensures efficient heat transfer. Additionally, avoid moving the joint before the solder has fully solidified.

Bridging

Bridging happens when excess solder connects adjacent leads, creating shorts. To avoid this, apply an appropriate amount of solder paste using a stencil with the right thickness. Use a fine-tipped soldering iron or a hot air rework tool to apply heat precisely. If bridging occurs, use a desoldering braid or a vacuum desoldering tool to remove excess solder. Practice steady hand movements when applying solder manually and avoid dragging the soldering tip across pads.

Insufficient Solder

Insufficient solder leads to weak joints that can easily break. To fix this, ensure that enough solder paste is applied during the assembly process. Check that the soldering tip transfers enough heat to allow solder to flow adequately across the pad and component lead. If needed, reflow the joint by reheating and adding a small amount of solder to improve coverage and strength.

Solder Balls

Solder balls are tiny spherical particles that can detach and create shorts. To prevent this, maintain a proper reflow profile that allows gradual heating and cooling. Ensure that the solder paste is of high quality and free from contamination. Clean the PCB surface thoroughly to remove dust and oil. Control the application of solder paste to prevent excessive paste that could splatter during heating.

Voids

Voids are gaps in the solder joint caused by trapped gas or flux residue. To minimize voids, pre-bake PCBs to remove moisture that can turn into steam during soldering. Use high-quality, low-residue flux and ensure even application. Adjust the reflow profile to give enough time for gases to escape before the solder solidifies. This reduces the chances of void formation.

Cracked Joints

Cracked joints can form due to rapid cooling or mechanical stress. Allow the solder joint to cool naturally without sudden air exposure. Ensure the PCB is not moved or subjected to vibrations while the solder is cooling. Choose solder materials with good thermal expansion properties to withstand temperature changes. For wave soldering, ensure that components are secure on the PCB before the process starts.

Non-wetting

Non-wetting occurs when the solder does not adhere properly to the pad or lead. This issue is often due to surface contamination or oxidation. Clean the board thoroughly with isopropyl alcohol or a PCB cleaner to remove oils, oxidation, or other contaminants. Use high-quality flux that promotes wetting and re-tin oxidized component leads before soldering. Ensure that the soldering temperature is within the recommended range for proper flow and adhesion.

Tombstoning

Tombstoning happens when one side of a component lifts off the PCB due to uneven heating. This can be addressed by ensuring an even reflow profile where both sides of the component are heated simultaneously. Verify that the solder paste deposit is balanced on each pad to prevent uneven solder melting. Additionally, using smaller components with balanced thermal mass can help prevent tombstoning.

Pin Holes or Blow Holes

Solution: Pin holes or blow holes result from gas escaping during soldering. To reduce this, pre-bake PCBs at a low temperature (e.g., 100°C for one hour) to remove moisture. Use flux that contains fewer volatile components. Optimize the reflow profile to allow flux and trapped gases to escape before the solder solidifies. Ensure that the soldering environment has low humidity to further minimize gas formation.

Oxidation Defects

Oxidation occurs when solder joints are exposed to air for too long before the soldering process. To prevent oxidation, apply flux shortly before soldering to create a barrier against air. Use a nitrogen atmosphere in reflow ovens to reduce oxidation. Regularly clean the soldering tip and apply fresh solder to prevent oxidation on the tip itself.

De-wetting

De-wetting occurs when the solder initially wets the pad but retracts, leaving an uneven surface. This can be caused by contamination or poor-quality solder. Ensure the soldering surface is free from contaminants and oxides by cleaning it with an appropriate cleaner. Use high-quality solder and maintain an optimal soldering temperature to allow proper wetting without over-stressing the solder.

Component Misalignment

Misaligned components can lead to poor connections and defects. Use automated pick-and-place machines for accurate component positioning. Check component alignment manually before reflow if placing by hand. During reflow, use alignment aids or fixtures to ensure components stay in place. Verify that the solder paste stencil and reflow settings are precise for even solder distribution.

Solder Splashes

Solder splashes are small splatters of solder that can lead to shorts or contamination. To prevent this, maintain a consistent reflow profile and avoid sudden movements during the soldering process. Check that solder paste is applied evenly, without excess. Ensure that the soldering environment is stable and free of vibrations.

Excessive Solder

Excessive solder can create thick joints or bridges between pads. Apply solder paste using a stencil with an appropriate aperture size for precise control. Train operators to apply the right amount of solder during manual soldering. Use a fine-tipped soldering iron for better control and to prevent large, excessive solder deposits.

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What is high frequency PCB?

high frequency PCB communication circuits refer to printed circuit board circuits that operate in a higher frequency range, usually between hundreds of MHz and tens of GHz. Compared with traditional low-frequency PCB circuits, high frequency PCB communication circuits have the following significant characteristics:

What is a high frequency pcb communication circuits?

1. High-speed signal transmission: high frequency PCB communication circuits can support high-speed data transmission and meet the needs of modern communication systems for large data volumes and high bandwidth.

2. Low signal loss: At high frequencies, signal transmission loss will increase significantly. Therefore, high frequency PCB communication circuits require special materials and design techniques to reduce signal loss and improve signal transmission quality.

3. Good electromagnetic compatibility: high frequency signals are prone to electromagnetic interference and affect surrounding electronic equipment. high frequency PCB communication circuits need to have good electromagnetic compatibility to ensure their stable operation in complex electromagnetic environments.

4. Miniaturization and lightweight: As electronic equipment continues to be miniaturized and lightweight, high frequency PCB communication circuits also need to develop in the direction of miniaturization and lightweight. This requires the use of high-density integration technology and advanced manufacturing processes to reduce the size and weight of circuit boards.

How do you make high frequency PCB?

Making a high frequency PCB (printed circuit board) involves several key steps to ensure the stability and reliability of signal transmission, taking into account the characteristics of high frequency signals.

1. ‌Material selection and preparation‌:

Choose a substrate material with low dielectric constant and low dielectric loss to ensure the stability and reliability of signal transmission.

The substrate material requires a conductive layer with good electrical conductivity and corrosion resistance.

Auxiliary materials such as membrane materials, filling materials, etc. also need to be carefully selected and prepared.

2. ‌Design, drawing production, etching, and laminating‌:

Carry out circuit design and layout planning based on design requirements and signal transmission characteristics.

Make PCB drawings and convert circuit layout and connection lines into circuit diagrams on the drawings.

The circuit diagram on the drawing is transferred to the substrate through photolithography technology and etched to form a conductive layer.

The film sticking process attaches the protective layer and copper clad layer to the conductive layer to protect the circuit and improve the mechanical strength.

3. ‌Welding and assembly process‌:

Surface mount technology is widely used in high frequency PCB welding, and SMT components are accurately welded to PCBs through methods such as hot air or reflow soldering.

Manual soldering technology also plays an important role in the assembly of high frequency PCBs. Plug-in components and connecting lines are connected by manual soldering.

4. ‌Special considerations for high frequency PCBs‌:

high frequency circuit design requires the adoption of special design principles and strategies, such as transmission line theory and matching, short and straight wiring strategies, impedance control and matching, decoupling and bypass, etc., to ensure signal quality and system reliability.

Adopt strategies such as multi-layer board design, straight wiring, shortening signal leads, reducing inter-layer alternation, being wary of crosstalk, increasing decoupling capacitors, isolating digital and analog ground wires, avoiding loops, ensuring impedance matching, and preventing ground bounce to improve Performance and reliability of high frequency circuits.

Through the above steps, a high-quality PCB that meets high frequency signal transmission requirements can be produced to ensure stable signal transmission and reliable operation of the system.

What are some important considerations when designing a PCB layout for high frequency circuits?

Designing high frequency PCB communication circuits faces many challenges and requires comprehensive consideration of circuit performance, electromagnetic compatibility, reliability and other aspects. Here are some of the major design challenges:

1. Signal integrity: At high frequencies, signal transmission will be affected by reflection, crosstalk, attenuation and other factors, leading to signal integrity problems.

2. Electromagnetic compatibility: As mentioned before, high frequency signals are prone to electromagnetic interference, so high frequency PCB communication circuits need to have good electromagnetic compatibility.

3. Thermal management: high frequency PCB communication circuits will generate a large amount of heat when working. If the heat cannot be dissipated in a timely and effective manner, the performance of the circuit will be reduced or even damaged.

4. Reliability: high frequency PCB communication circuits usually work in harsh environments, such as high temperature, high humidity, vibration, etc.

What is the highest frequency used for communication?

The highest frequency used for communication is 450GHz. ‌

This frequency range was finally approved at the 2019 World Radiocommunication Conference (WRC-19) and involves the 275 GHz-296 GHz, 306 GHz-313 GHz, 318 GHz-333 GHz and 356 GHz-450 GHz frequency bands, for a total of 137 GHz Bandwidth resources.

These frequency bands are used without restrictions for fixed and land mobile service applications. This is the first time that ITU has clarified the spectrum resources available for terrestrial active radio service applications in the terahertz frequency band above 275 GHz, and raised the upper limit of available spectrum resources for active services to 450 GHz, providing basic resource guarantee for the development and application of the global terahertz communication industry. .

Which frequency is best for communication?

For WiFi communication, choosing which frequency band is best depends on the user’s specific needs and network environment.

The 2.4GHz frequency band is suitable for use in home and office environments because of its strong signal penetration and low interference, especially when wide coverage and signal stability are required.

Because of its high-speed transmission capabilities, the 5GHz band is suitable for scenarios that require large traffic transmission, such as high-definition videos and online games, because it provides faster network speeds and more stable transmission rates.

In satellite communications, different frequency bands have their own advantages and applicable scenarios.

Although the C-band has low frequency and low gain, its rain attenuation is much smaller than that of the Ku-band and even smaller than the Ka-band. It is suitable for businesses that have strict requirements on communication quality, such as television and radio.

The Ku band has high frequency, high gain, small antenna size, and is easy to install. It is especially suitable for mobile emergency communication services such as communication in motion and communication in silence, and satellite news collection SNG and DTH services.

When selecting the wireless communication frequency band bandwidth.

The 20MHz frequency band bandwidth is suitable for small to medium-sized wireless networks due to its stable signal and wide coverage.

Although the data transmission rate of the 40MHz band bandwidth is relatively high, the signal penetration capability is weak and is suitable for dense environments or application scenarios that require higher transmission rates.

What are examples of high frequency equipment?

high frequency PCB communication circuits are widely used in various fields. The following are some of the main application fields:

1. Wireless communication: high frequency PCB communication circuits are the core components of wireless communication systems, such as mobile phones, base stations, satellite communications, etc.

2. Radar system: high frequency PCB communication circuits are also widely used in radar systems, such as radar antennas, signal processing, transmitters and receivers, etc.

3. Satellite communications: Satellite communications require the use of high frequency PCB communication circuits to transmit and receive signals.

4. High-speed data transmission: In the field of high-speed data transmission, high frequency PCB communication circuits can achieve data transmission rates of tens of Gbps per second to meet the needs of large data volume and high bandwidth.

In short, high frequency PCB communication circuits are an important part of modern communication technology and have broad application prospects and development potential. With the continuous advancement of technology.

What Is the Clearance Rule for PCB?

PCB design follows strict clearance rules to ensure that components work as expected. Clearance refers to the minimum space required between elements on the board to prevent interference, short circuits, or damage during soldering and operation.

What is the body to body clearance for smt parts？

The general clearance rules for PCBs depend on factors such as voltage, current, and operational environment. For standard PCBs, a common clearance rule is 0.1 mm to 0.2 mm between components, though this can vary based on specific needs. It’s essential to consult design guidelines from the PCB manufacturer, as they may provide specific instructions based on their capabilities.

How Close Can Components Be on a PCB?

Component spacing is one of the most crucial elements in PCB design. The minimum distance between SMT parts, or body-to-body clearance, is influenced by several factors, including component size, heat dissipation, and soldering methods.

For standard designs, a minimum body-to-body clearance of 0.2 mm to 0.5 mm is typical for most SMT components. This spacing ensures proper airflow, heat dissipation, and avoids accidental shorts during soldering. Smaller devices may require tighter clearances, but you should always account for potential manufacturing limitations and performance requirements.

Maintaining adequate clearance also helps with inspection and rework. If components are too close together, it becomes challenging to check for soldering defects or make repairs, increasing costs and time for revisions.

What Is the Spacing Between SMD Pads?

Surface Mount Devices (SMD) pads are small metal areas on the PCB where components are soldered. The pad spacing plays a critical role in ensuring good electrical contact while avoiding issues like bridging, where solder connects unintended pads, causing shorts.

The spacing between SMD pads is often defined by the component’s package type.

For example:

– For a 0603 package, the typical pad spacing might be around 0.8 mm.

– For a larger 1206 package, it could be around 1.5 mm or more.

In addition to pad spacing, the size of the pad must be carefully chosen to ensure that it supports the component correctly without causing issues during soldering. If the pads are too close, there is a higher chance of bridging, especially when using automated processes like reflow soldering. On the other hand, too much spacing could lead to poor contact, reducing the reliability of the connection.

What Is the Difference Between SMT and SMD Components?

SMT (Surface Mount Technology) refers to the process of mounting components directly onto the surface of a PCB. SMD (Surface Mount Device) is the term for the components themselves.

In essence:

SMT: The technology and process of assembling components on a PCB.

SMD: The individual components that are placed using SMT techniques.

The two terms are often used interchangeably, but it’s helpful to remember that SMT refers to the process, while SMD refers to the devices used in that process.

SMT has advantages over older methods like through-hole mounting, including reduced size and weight, faster production, and the ability to place components on both sides of the PCB. SMD components are designed specifically to benefit from these advantages, often smaller and lighter than their through-hole counterparts.

How Close Can PCB Traces Be?

PCB traces are the conductive pathways that connect components on the board. Proper spacing between these traces is critical to avoid electrical interference, arcing, or short circuits.

The minimum trace clearance depends on the operating voltage and current. For low-voltage circuits, traces can be closer together, but higher-voltage designs require more significant separation to avoid electrical breakdown.

For example:

– For a PCB operating at less than 100V, a typical trace clearance might be around 0.2 mm to 0.5 mm.

– For high-voltage designs (e.g., 600V), trace spacing might need to increase to 3 mm or more.

It’s essential to follow the manufacturer’s recommendations and industry standards like IPC-2221 when determining trace clearance. Additionally, wider spacing can improve performance, particularly in high-frequency circuits where issues like crosstalk become more prominent.

What Is the Edge Clearance of a PCB?

Edge clearance refers to the distance between components or traces and the outer edges of the PCB. Ensuring adequate clearance near the edges prevents damage during manufacturing and assembly. It also allows room for board routing, where mechanical tooling may cut the board from a larger panel.

The general rule for edge clearance is to keep components at least 1 mm to 2 mm away from the PCB’s edge. This gives enough room for mechanical handling, ensures that traces aren’t damaged during cutting, and reduces the risk of short circuits due to edge contact.

In designs that incorporate connectors or other mechanical features near the board’s edge, additional clearance may be necessary to accommodate mounting holes or alignment features.

Additional Considerations for SMT Clearance and Spacing

In addition to the factors already covered, there are several other considerations when designing SMT PCBs:

1. Thermal Considerations: Proper body-to-body clearance helps ensure that heat can dissipate effectively. Crowding components too closely together can lead to hot spots, reducing the life of the board and its components.

2. Automated Assembly: If you’re using automated pick-and-place machines for assembly, sufficient clearance is needed for accurate placement. Overly tight layouts can lead to assembly errors or slower production times.

3. Manufacturability: PCB fabricators have limitations on how closely they can place components, traces, and vias. These limitations vary from one manufacturer to another, so it’s essential to consult with them early in the design process to avoid issues during production.

4. Inspection and Rework: Allowing enough space between components simplifies inspection and rework. If something goes wrong during assembly, having accessible components makes repairs quicker and more cost-effective.

Practical Tips for Ensuring Proper Clearance Between PCBs

Use Design Guidelines: Always reference your PCB manufacturer’s design rules. These will give you specific guidance on spacing, trace widths, and clearances based on their capabilities.

Optimize Component Placement: Group similar components together when possible. For instance, resistors and capacitors can often be placed closer together than components that require heat dissipation.

Account for Heat Dissipation: Keep heat-generating components like power ICs and transformers farther apart from sensitive components like sensors. This minimizes heat transfer and reduces the chance of thermal stress.

Perform Electrical Testing: Simulate your design using PCB software to check for potential clearance violations, especially around high-voltage areas and traces that could experience crosstalk.

Test with Prototypes: Before full production, build a prototype to test clearance in real-world conditions. This will allow you to identify any spacing issues and resolve them before scaling production.

Conclusion:

Achieving proper body-to-body clearance for SMT parts is critical for the performance and longevity of your PCB. By following the established guidelines for component spacing, pad placement, trace clearance, and edge spacing, you can ensure that your design meets both functional and manufacturability requirements. This not only improves the reliability of your board but also reduces the likelihood of costly errors during assembly and operation.

Invest time in careful planning during the design phase to avoid unnecessary revisions later on. Working closely with your PCB manufacturer and utilizing design simulation tools can go a long way in ensuring your final product performs as expected.

In the end, understanding and applying the right clearance rules will result in a robust, reliable, and efficient PCB design that meets the demands of modern electronics.

How to check solder paste?

1. Visual observation:

Under natural light or good lighting conditions, directly observe the appearance characteristics of the solder paste such as color and state with the naked eye. Normal solder paste has uniform color and no obvious particle agglomeration, precipitation, stratification and other phenomena.

2. Viscosity detection:

Viscosity is an important physical performance indicator of solder paste, which has a great influence on printing performance and welding quality. Professional equipment such as rotary viscometer can be used for detection.

In general, the viscosity of solder paste should be within a certain range and meet the product specification requirements. If the viscosity is too high, it may cause printing difficulties and poor demolding; if the viscosity is too low, the solder paste may flow during printing, affecting printing accuracy.

3. Metal content detection:

Metal content directly affects the welding performance of solder paste and the strength of solder joints. Chemical analysis or spectral analysis is usually used for detection.

4. Particle size detection:

The particle size and distribution of metal particles in solder paste will also affect its performance. Laser particle size analyzer and other equipment can be used for detection.

This method determines the particle size distribution of particles by measuring the scattering or diffraction of metal particles on laser. Generally, the particle size distribution of metal particles is required to be concentrated within a certain range, and the proportion of particles that are too large or too small should not be too high.

What is the most common solder paste?

The most common solder paste is rosin solder paste.

‌Rosin solder paste is widely used because of its excellent flux and protective effect, as well as the protective film formed after welding, which has a protective effect on solder joints. Even if cleaning is not required, there will be no corrosion.

In addition, rosin is easy to mix with other ingredients, which can play a role in adjusting viscosity, so that the metal powder in the solder paste is not easy to precipitate and stratify. These characteristics make rosin solder paste the most common type of solder paste.

What are the advantages of solder paste inspection?

Solder paste inspection has many advantages, as follows:

1. Ensure product quality:

Discover problems in advance: By inspecting solder paste before welding, you can find quality problems of the solder paste itself in time, such as uneven composition, inappropriate metal particle size, insufficient flux activity, etc., to ensure the welding quality of electronic products from the source.

Optimize welding process: By testing the viscosity, thixotropy and other performance indicators of solder paste, you can determine whether the solder paste is suitable for the current printing process and welding equipment.

2. Improve production efficiency:

Reduce rework of defective products: Testing solder paste can quickly screen out solder paste that does not meet quality requirements and avoid using these solder pastes in production, thereby reducing defective products caused by solder paste quality problems.

Easy to control the production process: In large-scale production, you can regularly test the solder paste, monitor the quality changes of the solder paste in real time, and detect abnormal conditions in the production process in time.

3. Reduce production costs:

Avoid material waste: By testing the solder paste, you can avoid using problematic solder paste, reduce material waste and unnecessary production costs.

Extend equipment life: Good quality solder paste can reduce wear and corrosion on printing equipment and welding equipment, and reduce equipment maintenance costs and replacement frequency.

4. Meet industry standards and customer requirements:

Meet industry specifications: The electronics industry has strict standards and specifications for welding quality, such as IPC standards. Conducting solder paste inspection can ensure that the quality of solder paste meets the requirements of these standards and specifications and improve the competitiveness of enterprises.

Meet customer needs: In the production process of electronic products, customers usually have clear requirements for welding quality. Through solder paste inspection, improve customer trust and satisfaction with the company and enhance the market competitiveness of the company.

What are the defects of solder paste inspection?

Although solder paste inspection is a key step, it is not without challenges. Some common defects found during SPI include:

Insufficient solder paste: If too little solder paste is used, it will result in fragile joints or poor electrical connections.

Too much solder paste: Too much solder paste can cause bridging between components, causing short circuits.

Misalignment: If the solder paste is not applied accurately, it may not align with the pads on the PCB, causing problems when placing components.

Collapse: In some cases, solder paste may spread too much after application, resulting in poor joint formation.

Solder balls: Small, unwanted solder balls may form around the pad, which may cause electrical shorts.

Do you need flux when using solder paste?

Additional flux is usually not required when using solder paste.

Solder paste itself contains flux ingredients. Solder paste is a paste-like substance made by evenly mixing solder alloy powder and flux. The role of flux in solder paste mainly includes removing oxides on the soldering surface, reducing the surface tension of solder, and promoting solder wetting and diffusion.

During the soldering process, the flux in the solder paste will work at the appropriate temperature to help achieve good soldering results. However, in some special cases, such as soldering some special materials or when there are extremely high requirements for soldering quality, additional flux may be considered, but this is a relatively special application scenario.

What is a solder paste inspection machine?

Solder Paste Inspection (SPI) is a device used to detect solder paste printed on a printed circuit board (PCB).

The main functions include:

1. Solder paste height measurement

Use laser scanning, optical imaging and other technologies to accurately measure the height of solder paste on the PCB pad.

2. Solder paste area measurement

Determine the coverage area of solder paste on the pad. If the solder paste area is too small, a good solder connection may not be guaranteed; if the area is too large, it may overflow the pad, affecting the subsequent assembly process.

3. Volume measurement

Calculate the volume of solder paste based on height and area data. Accurate volume measurement helps ensure consistent solder paste volume for each solder joint, thereby improving the stability of soldering quality.

4. Defect detection

Misprint detection: Detect whether there is solder paste misprint on the PCB pad.

Offset detection: Detect whether the solder paste printing position is offset from the designed pad position.

Shape anomaly detection: Identify whether the shape of the solder paste is abnormal, such as irregular shape, unclear edges, etc. Shape anomalies may be due to problems in the printing process, which will affect the welding quality.

Solder paste inspection machines can detect solder paste quality problems in the printed circuit board production process in a timely manner, improve production efficiency and product quality, and reduce rework and scrap caused by poor soldering.

What is the best temperature for solder paste?

The optimal temperature range for solder paste is 150℃～180℃‌, and the time to maintain this temperature range should be 60～120 seconds to ensure that the solder paste can fully infiltrate the pads and component pins.

This temperature and time range is critical to controlling the quality of reflow soldering, as it involves the effective volatilization of flux and the full infiltration of pads, thereby ensuring the reliability and quality of soldering‌.

Conclusion:

Solder paste inspection is a key step in modern electronic manufacturing to ensure that solder paste is correctly and evenly applied to PCBs. By using advanced SPI machines, defects can be detected early, process control can be improved, and costs can be reduced. Whether using leaded or lead-free solder paste, ensuring the correct amount, alignment, and temperature is critical to forming strong and reliable solder joints.

BEST Technology has a professional solder paste inspection machine. Each PCB board must undergo rigorous testing. Choosing BEST Technology, you will get the highest quality PCB board.

How to remove oxidation from PCB?

The methods for removing oxides from PCBs mainly include physical cleaning, chemical cleaning, and mechanical polishing.

1. ‌Physical cleaning‌:

Use alcohol or diluent to gently wipe the oxidized part until the oxide is removed. This method is suitable for removing the surface oxide layer, but it is not suitable for situations where the metal surface circuit has been damaged.

2. ‌Chemical cleaning‌:

Use specific cleaning agents such as deionized water, isopropyl alcohol, acetone, etc. to effectively remove residues and contamination.

In addition, cleaning and corrosion using acidic solutions or oxidants is also an effective chemical method, but it must be used with caution to avoid damage to the PCB board and other components.

3. ‌Mechanical polishing‌:

Use fine sandpaper or abrasive cloth to carefully polish the oxidized area to restore the conductivity of the metal. This method is suitable for removing thicker oxide layers, but you need to control the strength to avoid damaging the pad surface.

Before any cleaning and repair, be sure to disconnect the PCB power supply to ensure safety. For cases where oxidation has damaged the metal surface circuit, conductive paint needs to be used for repair, but be aware that excessive use of conductive paint may damage the circuit board. In addition, for unused PCBs, they should be stored in sealed bags or protective agents and checked regularly to ensure that they are not oxidized again.

Is silver oxidation permanent?

Silver oxidation is not permanent. ‌

Silver oxidation is caused by the reaction of silver with chemicals such as oxygen and sulfur in the air, resulting in a black silver sulfide film on the silver surface. This oxidation reaction is one of the main reasons for the blackening of PCBs.

However, silver oxidation is not permanent, because the oxide layer can be removed by cleaning and maintenance to restore the gloss of the PCB surface. For example, regular use of professional PCB cleaners or soaking the PCB in diluted detergent water, then gently scrubbing it with a soft brush, and finally rinsing it with clean water and drying it can effectively remove the oxide layer.

In addition, avoiding contact with chemicals, keeping dry, regularly checking and properly storing PCBs are also effective ways to prevent oxidation.

Therefore, although silver oxidation is inevitable, the rate of oxidation can be slowed down through proper care and maintenance.

What is the best way to Deoxidize silver?

The best way to remove silver oxide from PCBs is to use chemical stripping, which involves using a specific chemical solution to treat the silver plating so that it dissolves in the solution to achieve the purpose of removing the oxide.

The effectiveness of this method depends on the selection of appropriate chemical formulas and operating conditions to ensure that the silver layer can be completely stripped while avoiding corrosion to the base metal.

In chemical stripping, different formulas can be used to achieve the removal of the silver layer. For example, one formula includes a mixture of concentrated sulfuric acid and concentrated nitric acid, which is used at a temperature of 80°C until the silver layer is completely stripped.

Another formula includes a mixture of sulfuric acid, nitric acid, silver chloride and potassium cyanide, which is also used at a temperature of 80°C. These formulas need to be selected according to actual conditions, and attention should be paid to safety measures during operation to prevent corrosion of the base metal.

In addition, for the oxidation problem of PCB gold fingers, although it is not exactly the same as the method of removing silver oxide, some cleaning methods are provided, such as using erasers, alcohol cleaning, decontamination paste cleaning, scrubbing board grinding and electroplating treatment, which are also suitable for treating silver oxide, especially when the oxide is relatively mild.

In summary, the best way to remove PCB silver oxide is chemical stripping, which is achieved by selecting appropriate chemical solutions and operating conditions. For more serious oxidation situations, it may be necessary to combine physical and chemical methods for cleaning.

How do you save silver from oxidation?

The methods to prevent PCB silver from oxidation mainly include the following points:

Reasonable storage and packaging ‌: During storage and transportation, PCBs should be stored in a dry, ventilated, dust-free environment to avoid moisture and corrosion. Use appropriate packaging materials, such as moisture-proof bags, foam boxes, etc., to ensure the integrity and quality of the PCB.

‌Surface treatment ‌: During the PCB surface treatment process, surface treatment methods such as gold plating and tin plating can be used to prevent oxidation.

Use anti-oxidation coating ‌: Anti-oxidation coating is an efficient and reliable method to prevent PCB oxidation. It can form a strong, corrosion-resistant protective layer on the surface of the PCB, effectively preventing the PCB from being damaged by oxidation.

Reduce contact with air and moisture‌: Make sure the gold fingers are stored in a dry environment and avoid long-term exposure or immersion in water.

‌Use a protective coating‌: Applying a protective coating on the gold fingers can help prevent oxidation. This can be done using a variety of materials, such as nickel, palladium, or a thin layer of metal‌.

‌Regular cleaning and inspection‌: Regular cleaning of the gold fingers can also help prevent oxidation. This is done using a soft brush and a cleaning solution specifically designed for PCBs‌. Check the status of the gold fingers regularly, and clean and maintain them immediately if any signs of oxidation are found‌.

What is the shelf life of immersion silver PCB?

The shelf life of immersion silver PCB is at least 12 months. ‌This shelf life is determined under proper storage conditions, that is, in a sealed package, with a temperature controlled at 22 degrees plus or minus 4 degrees, and a relative humidity of less than 70%.

Once the circuit board is taken out for use, it must be soldered within 24 hours to ensure that its quality and performance are not affected‌.

The thickness of immersion silver surface treatment is usually between 0.4 and 1 micron, and this treatment is widely used by chip manufacturers for baseline bonding, EMI shielding and metal dome contacts.

Its purpose is to provide a reliable surface treatment, ensuring that the PCB surface will not oxidize and maintain its electrical performance stability for a shelf life of 12 months according to the IPC J-STD-003 standard.

In addition, the shelf life of the circuit board is also affected by its surface treatment process. For example, the vacuum packaging storage period of immersion gold, electro-gold, and tin-spraying boards is 3 months, while the storage period after unpacking for OSP, immersion tin, and immersion silver boards is 48 hours, 72 hours, and 48 hours respectively.

This shows that immersion silver PCBs can maintain a long shelf life if they are not unpacked, but the soldering process needs to be completed as soon as possible before use to ensure their performance.

Conclusion:

Silver oxidation is a natural process, but it does not affect the performance of the PCB. The key to controlling silver oxidation is regular maintenance, proper storage, and quick action when rust occurs. It should be stored properly and coated with a protective coating when necessary.

Usb connector types

Types of USB connectors: different types of connectors with different shapes and directions, USB connectors can be separated into different types:

Type-A port: This is the most common type of USB port, the shape is long and rectangular, and the support is heat-resistant. Computer equipment such as printing machine, keypad, mouse button, driving device, etc. Type-A interface has USB 2.0 and USB 3.0 in different editions, among which USB 3.0 has faster speed, color is usually blue, and USB 2.0 has slow speed, color is black.

Type-B contact: Type-B contact shape is round shape, demand-specific connection. For general use, external equipment such as audio equipment, viewing equipment, etc., such as a 3.5 inch movable screen, stamping machine, display device, etc.Type-B verbal usage scene is relatively small, so this is an unusual sight in daily life.

Usb connector types:Type-A port:Type-B contact

Type-C port: Type-C port is a new type of USB port that has emerged in recent years. Built-in USB 3.1, Type-C interface configuration, mainstream interface type, intelligent handheld computer, flat panel battery, notebook battery, etc. The biggest feature of the Type-C interface is its support and double-sided insertion, making it convenient and convenient to use.

Type-C interface support further improves the speed and power of the power, and provides more advanced usage experience. Previously, when I came here, I was confused as to how to get around the main machine.

Mini USB port Micro USB port

Mini USB port Micro USB port: There are many types of ports for transfer equipment, digital reading machine, digital image machine, metering equipment, etc. Mini USB port ratio Micro USB port size is small, also known as a USB port, Micro USB port is smaller, thinner, supports OTG function, and provides a number of additional power functions. The Micro USB port is convenient and easy to use, and has various types of portability.

What functions does USB have?

Power Delivery of USB Ports
Some USB cables can deliver power as well as transfer data, but most USB cables can do both. Power delivery of USB ports is mainly divided into three categories: fast charging, quick charging, and power only.
USB Data Transfer Speed
USBs come in various sizes and shapes. Also, USB types have multiple speed standards. It is important to know that some USB cables are designed for data transfer only, while some can only deliver power. However, some USB cables can serve both purposes at the same time. Therefore, it is necessary to verify the performance of the cable before purchasing it.
USB Video Transfer
The ability of USB ports to power devices and transfer data between devices is already impressive enough. However, you can decide to integrate USB-C to connect a monitor in place of a VGA cable or HDMI. In addition, USB-C also supports 4K video transmission.

What are the advantages of USB interface?

Standard uniformity. The most common ones are hard disks with IDE interfaces, mouse and keyboards with serial ports, and printers and scanners with parallel ports. However, with USB, all these application peripherals can be connected to personal computers using the same standard. At this time, there are USB hard disks, USB mice, USB printers, etc.
Easy to carry. Most USB devices are known for being “small, light, and thin”, which is very convenient for users to carry large amounts of data with them.
Hot-swappable. That is, when users use external devices, they do not need to shut down and restart the computer, but directly plug in the USB when the computer is working.
Multiple devices can be connected. USB often has multiple interfaces on personal computers, and several devices can be connected at the same time. If a USB HUB with four ports is connected, four USB devices can be connected, and so on. You can connect all the devices to a personal computer at the same time without any problems (up to 127 devices can be connected).

How Do USB Ports Work?

USB is an external bus standard used to regulate the connection and communication between computers and external devices. The USB interface has plug-and-play and hot-swap functions. The USB interface can connect 127 peripherals, such as mice and keyboards. USB was jointly launched by Intel and other companies in 1994 and has successfully replaced serial and parallel ports since 1996. It has become a must-have interface for computers and a large number of smart devices today. For most engineers, the main obstacles to developing USB2.0 interface products are: facing the complex USB2.0 protocol, writing USB device drivers by themselves, and being familiar with microcontroller programming.

Why USB Ports Are Replacing Serial Ports

USB has three major advantages. It is superior to serial ports in several aspects.

Speed
USB ports are able to transfer data at a much faster speed. They work ten times faster than regular parallel ports. Also, they are much faster than serial ports. On average, serial ports offer a data transfer rate of 150kbps. On the other hand, USB ports offer about 12 Mbps. The data transfer rate depends on the type of USB port. For example, USB 2.0 has a maximum data transfer rate of 480 Mbps.

Compatibility
USB ports have replaced serial ports in the past few years. Various industrial devices are equipped with serial ports. This replacement has brought problems. USB ports are generally compatible with most USB devices.

Durability
USB ports are more durable than serial ports. The tiny pins on a serial port can break or bend easily. Whereas USB ports are very sturdy.

Frequently Asked Questions

The USB interface cannot be used. It may be due to a problem with the system. You need to check whether the system service is disabled or reinstall the operating system.

‌BIOS setting problem‌. If USB is disabled in BIOS or CMOS, you need to restore it to the factory default settings.

‌USB driver is not installed or the driver is deleted‌. You need to install the USB universal driver.

‌The front USB cable is not connected properly‌. Try to insert the USB flash drive into the USB interface on the back of the chassis.

‌The USB interface voltage is insufficient. When the mobile hard disk is connected to the front USB interface, it may not be recognized due to insufficient voltage. You should use a hard disk box with an external power supply or replace the power supply.

‌Compatibility issues between the motherboard and the system‌. For example, the compatibility issues between the NF2 motherboard and USB require the installation of the latest dedicated USB2.0 driver and patch.

‌System or BIOS problem‌. When USB is disabled in the BIOS or operating system, you need to enable options related to USB devices.

‌Be careful when plugging and unplugging. Do not unplug during reading and writing, otherwise the chip may be burned.

‌If the USB device is frequently disconnected‌, it may be that the USB cable connection is unstable or there is a problem with the USB port. Try changing the cable or connecting to another USB port.

‌If the USB device cannot be recognized or charged‌, make sure the device is compatible and the cable is intact. Try connecting to another computer or updating the driver.

What is the composition of solder paste?

Solder paste is a complex mixture of multiple components, and its main components include metal powder, flux and solvent.

What is solder paste? What is its function?

The metal powder in solder paste is usually composed of metal alloys such as tin, silver and copper. The particle size and distribution of metal powder have a direct impact on the welding effect. The smaller the particle size, the more uniform the distribution, and the better the welding effect.

At the same time, the composition of the metal alloy also determines the mechanical strength and electrical properties of the solder joint.

Flux is another important component in solder paste. Its main function is to remove oxides on the welding surface and improve the wettability and reliability of welding.

The type and formula of flux directly affect the melting state and solder joint quality during the welding process. Common fluxes include rosin-based flux, organic acid flux and halogen-free flux.

Solvents are used to adjust the viscosity and printing performance of solder paste. Appropriate viscosity can ensure that the solder paste is evenly distributed during the printing process without problems such as drawing and collapse. The evaporation rate of the solvent will also affect the drying time and welding performance of the solder paste.

What is the role of solder paste in SMT patches?

In the SMT (surface mount technology) patch processing process, solder paste plays a vital role. It is not only used to bond components, but also the key to ensure the quality of electrical connections and mechanical strength.

1. Bonding components

One of the main functions of solder paste is to bond components. After the solder paste is accurately printed on the pads of the PCB (printed circuit board), the pins or contact points of the electronic components will be placed on the solder paste. The solder paste melts during the reflow soldering process to form a strong bond, ensuring that the components are stably attached to the PCB.

2. Provide electrical connection

Solder paste melts during the reflow soldering process and forms metal solder joints, which not only bond components but also provide electrical connections. Good electrical connections ensure the effective transmission of electrical signals on the PCB, which is the basis for ensuring the normal operation of electronic equipment.

The solder joints formed by the metal components (such as tin, silver, and copper) in the solder paste after melting have excellent conductivity, ensuring the reliability and stability of electrical connections.

3. Ensure mechanical strength

The mechanical strength of the solder joints is the key to ensuring the stable operation of electronic components in various environments. The solder joints formed by the solder paste after reflow soldering have sufficient mechanical strength to resist external stresses such as vibration, impact, and thermal expansion and contraction. This not only protects the components and PCB, but also improves the reliability and service life of the entire electronic equipment.

Is solder paste the same as flux?

Solder paste and flux are not the same. ‌

Although both solder paste and flux are materials used in the welding process, their functions and uses are different.

Solder paste is a paste-like viscous body, the main components of which include metal powder, rosin, organic acid, thixotropic agent, and activator, and is used for welding in SMT automatic mounting process.

Flux is a liquid, a mixture with rosin as the main component, which is used to remove oxides on the surface of solder and the base material to be welded, so that the metal surface reaches the necessary cleanliness, prevents the surface from re-oxidation during welding, reduces the surface tension of the solder, and improves welding performance.

In general, although both solder paste and flux are indispensable materials in the welding process, they have obvious differences in form, function, and usage.‌

What is the storage method of solder paste?

The correct storage method can extend the service life of the solder paste and ensure its stable performance.

1. Temperature control

Solder paste should be stored in a low temperature environment, usually 0-10℃. Excessive temperature will cause the solvent in the solder paste to volatilize, affecting its viscosity and printing performance. Avoid direct sunlight and high temperature environment during storage to prevent the solder paste from deteriorating.

2. Humidity control

Humidity has a great impact on solder paste. Excessive humidity will cause the solder paste to absorb moisture, affecting its printing performance and welding quality. The relative humidity of the storage environment should be controlled below 50% to ensure the stability of the solder paste.

3. Sealed storage

The solder paste should be stored in a sealed container to prevent oxygen and moisture from entering the air. The solder paste after opening should be used up as soon as possible, and the unused solder paste should be resealed and stored in a low temperature environment.

How to use solder paste correctly?

1. Reheating treatment

The solder paste stored in a low temperature environment should be reheated before use. The reheating time is usually 4-8 hours. During the reheating process, it should be avoided to be directly exposed to a high temperature environment to prevent the solvent in the solder paste from volatilizing. The solder paste after reheating should be fully stirred to ensure that the metal powder and flux are evenly distributed.

2. Printing process

Solder paste printing is a key process in SMT patch processing. During the printing process, the scraper pressure, printing speed and template opening size should be controlled to ensure that the solder paste is evenly distributed on the pad. The printed solder paste should have a good shape and should not have problems such as drawing and collapse.

3. Solder paste reflow

The solder paste reflow process is the process of melting the solder paste and forming a firm solder joint with the pad and component pin. The temperature curve should be controlled during the reflow soldering process to ensure that the solder paste melts at an appropriate temperature and fully wets the pad and pin. Too high or too low reflow temperature will affect the welding quality.

4. Solder joint detection

The quality of the solder joint is an important indicator for evaluating the welding effect. After the welding is completed, the solder joint detection should be carried out to check the shape, size and wettability of the solder joint. Qualified solder joints should have a smooth and complete surface without defects such as solder balls and cold solder joints.

Conclusion:

Solder paste plays a vital role in SMT patch processing. Its composition, selection, storage and use methods directly affect the welding quality and the performance of the final product. By understanding and mastering the relevant knowledge of solder paste, the quality of SMT patch processing can be effectively improved, and defects and rework rates can be reduced.

BEST Technology has rich experience and strict control standards in the selection and use of solder paste, and can provide customers with high-quality SMT patch processing services. If you have any questions about our products or services, please feel free to contact us. Choose BEST Technology , choose quality assurance.

What is a PCB test?

PCB test is a technique that uses electronic testing instruments to detect the performance and quality of PCB (Printed Circuit Board) circuit boards. It is widely used in the electronics manufacturing industry to help manufacturers improve product quality and production efficiency.

The main purpose of PCB test is to ensure that all parts on the circuit board are properly connected and can still work properly under high voltage environments, while verifying whether the function of the circuit board is normal. Test methods include connectivity testing, withstand voltage testing, and functional testing, while inspection standards involve appearance inspection, size inspection, and performance inspection. In addition, PCB test also involves a series of professional techniques and methods, such as flying probe test, ICT test, FCT test, AOI test, etc., to ensure the electrical performance and structural integrity of the circuit board.

How to Test PCB?

PCB contains different components that affect the overall performance of electronic circuits. Tests are performed to check and optimize the status of these components using computerized machine software, simple electronic test equipment and tools, and even basic manual inspections.

1. Electrical test

2. Hole wall quality

3. Mechanical resistance test

4. Soldering quality

5. Cleanliness inspection, considering weather resistance, humidity and corrosion

6. Lamination, testing the ability of laminates to resist or heat peeling

Environmental testing is particularly necessary for PCBs used in humid environments.

What are the benefits of PCB test?

Error identification: The main benefit of PCB test is that it helps identify problems in PCBs. Whether the problem lies in functionality, manufacturability or other aspects, PCB test can identify problems in PCB design and layout.

Save time: Performing PCB test early helps save time in the long run by allowing designers to identify major issues during the prototyping phase. Comprehensive testing allows designers to quickly and easily identify the root cause of each issue and make adjustments so that they can move to production at a faster pace and reduce product lead times.

Reduce costs: PCB test avoids the waste of producing defective products by testing products using prototypes and small-scale components. By completing comprehensive testing early in the design process, designers can avoid the waste of producing defective PCBs, ensuring that the design is as perfect as possible before going into production.

Reduced returns: When PCB test is performed, the likelihood of selling defective products or products that do not meet performance standards is reduced, reducing the costs associated with refunding customers and handling defective goods.

Improved safety: Defective PCBs can cause fires, which can endanger people nearby. Pre-manufacturing testing also ensures that machines and workers are not damaged or injured due to poor design during the production process.

What are the types of PCB test?

1. In-circuit testing

In-circuit testing (ICT) is the most reliable type of PCB test available today. The high price reflects this – tens of thousands of dollars, although the cost depends on factors such as board and fixture size.

Also known as bed of nails testing, ICT fires and activates individual circuits on a board. In most cases, the test is designed to achieve 100% coverage, but actual coverage will be closer to 85-90%.

The test involves the use of fixed probes, whose layout matches the PCB design. The probes check the integrity of the soldered connections. A bed of nails tester simply pushes the board onto the probe bed to begin testing. Access points are pre-designed on the board to allow the ICT test probes to establish a connection with the circuit.

2. Flying probe testing

Flying probe testing is a tried and tested method that is cheaper than in-circuit testing. It is a non-powered test that checks for shorts, capacitance, inductance, diodes, and other problems.

The flying probe tester works by using needles connected to probes on an xy grid obtained from basic CAD. The ECM program coordinates to match the board and then runs the program connected to these test points.

In some cases, ICT makes flying probe testing unnecessary, but the PCB must be designed to fit the test fixture – which means a higher initial cost. ICT is faster and less error-prone than flying probe testing, and while flying probe testing may be cheaper initially, it may not actually be cost-effective for large orders. Finally, it is important to note that PCB flying probe testing does not power the board.

3. Automated Optical Inspection (AOl)

AOI is a contact-free visual inspection of printed circuit boards. AOI uses a camera and microscope to take photos of the PCB. The software then looks for inconsistencies between these photos and the board schematic. Technicians can thoroughly check each board and find any problems through this procedure.

The board is not powered during AOI, and it may not cover all part types. Due to these deficiencies, it should be used in conjunction with another test technology such as functional testing, flying probe testing, or ICT.

4. X-ray Inspection

As the name suggests, this type of test is essentially an inspection tool. It is also known as AXI. During this testing, X-ray technicians can detect defects early in the production process by carefully inspecting solder connections, internal traces, and barrels. Using X-ray inspection, invisible components can be inspected.

Due to the high density of SMT technology and the difficulty in locating connections in BGA and CSP (chip scale packages), more precise inspection techniques, such as those based on X-ray technology, are needed. Solder joints can be clearly seen in radiographs because they are made of materials with a higher atomic weight than other components on the board.

The main benefit of AXI technology is that it can identify every connection and solder joint, including those hidden by the package. In addition, solder joints can be inspected, highlighting any potential bubbles.

What are the difficulties in PCB test?

Increasing complexity: PCB designs are becoming more complex, with higher component density and smaller size, which makes it more difficult to access test points and increases the risk of undetected defects.

Cost: High-end test equipment such as X-ray inspection systems can be expensive to purchase and maintain. Testing also increases production costs, especially when test failures require rework.

Accuracy: Although the test equipment is designed precisely, errors may still occur due to calibration problems, software errors or human errors.

Conclusion:

PCB test is very important to the quality of the product. It ensures that the PCB, which forms the backbone of all electronic devices, operates normally and meets the required quality standards, effectively avoiding the impact of poor products, improving the quality of the finished product, and preventing problems when the product is used.

BEST Technology has a complete set of PCB test equipment and has very complete testing standards to ensure that each PCB finished product has extremely high quality. Choosing us, you will not need to worry about any PCB quality issues.

What is flux?

Flux: A chemical substance that can help and promote the soldering process in the soldering process, and at the same time has a protective effect and prevents oxidation reactions. Flux can be divided into solid, liquid and gas.

There are mainly several aspects such as “assisting heat conduction”, “removing oxides”, “reducing the surface tension of the material to be soldered”, “removing oil stains on the surface of the material to be soldered, increasing the soldering area”, and “preventing re-oxidation”. Among these aspects, the two most critical functions are: “removing oxides” and “reducing the surface tension of the material to be soldered”.

Do you apply flux before or after soldering?

Use flux before soldering printed circuit boards. ‌

During the soldering process of printed circuit boards, the main purpose of using flux is to improve soldering performance and help the metal avoid the formation of an oxide film that hinders solder wetting when heated, thereby promoting the formation of solder-metal alloys and avoiding the occurrence of cold soldering and false soldering.

Flux can be applied to the printed circuit board before soldering, or it can be used as part of the solder during the soldering process, such as solder paste or solder oil. When tinning the pins of components, rosin should be used as the flux, and if the printed circuit board is already coated with rosin solution, then no additional flux is required during soldering.

After using flux, make sure to wipe off the residual flux at the soldering site after soldering to avoid potential damage to electronic components and circuit boards.

In addition, the preparation work before soldering includes thoroughly cleaning the copper foil surface and then applying rosin water to protect the copper foil and help soldering. This step is performed before soldering to ensure the smooth progress of the soldering process. Therefore, the correct approach is to use flux before soldering printed circuit boards to ensure the quality and reliability of soldering.

How much flux to use when soldering?

When soldering printed circuit boards, the amount of flux used needs to be determined according to the specific soldering method and the type of flux. For wave soldering flux, when using brushing and foaming methods, the specific gravity of the flux should be controlled between 0.82-0.84 (specific gravity of liquid rosin flux stock solution).

During the soldering process, the specific gravity of the flux needs to be measured regularly. If the specific gravity is found to increase, it should be adjusted to the normal range with diluent in time, but the diluent should not be added too much to avoid affecting the soldering quality.

For the quantitative spraying method, the key is that the nozzle can control the spray volume. The nozzle should be cleaned frequently to ensure that the spray hole is not blocked. The spray pressure should be controlled at 0.2-0.3Mpa, the flux pressure should be controlled at 0.4±0.05Mpa, and the spray flow rate should be controlled at 20-35ml/min.

In addition, different types of flux formulas are also different. For example, rosin liquid can be made by mixing rosin blocks and alcohol in a ratio of 1:3. For the flux of printed circuit boards, you can directly use rosin water, and apply the prepared rosin water directly on the surface of the printed circuit board or the solder joints.

When using flux, you should also pay attention to the following points:

Put the bottle cap on immediately after use to prevent the flux from being in contact with air for a long time and causing oxidation reaction or absorbing water vapor in the air to cause the concentration to decrease.

Regularly replace the flux that has been stored for too long, because long-term storage will cause the flux composition to change and the activation performance to deteriorate, affecting the welding quality.

Clean it after welding, because the insulation performance of the flux will drop sharply at high temperature, and the residue may affect the heating components, and in severe cases may cause short circuits.

In summary, the amount of flux used in printed circuit board welding needs to be determined according to the specific welding method and flux type, and pay attention to the use and storage conditions of the flux to ensure welding quality and safety.

What happens if you use too much flux when soldering?

First, the main functions of flux include assisting heat conduction, removing oxides, reducing the surface tension of the material being soldered, removing oil stains on the surface of the material being soldered, increasing the soldering area, and preventing reoxidation.

However, excessive use of flux can lead to corrosion and electromigration. This is because improper use of flux, such as excessive use, can create more favorable conditions for potential chemical corrosion reactions.

In addition, if the flux used is not well controlled, resulting in excessive use of flux, more flux residue will be left, which creates more favorable conditions for potential chemical corrosion reactions.

Therefore, it is very important to control the amount of flux used to avoid negative effects on soldering quality and reliability.

What happens if I don’t use flux?

If flux is not used on printed circuit boards, it may lead to reduced soldering quality, increased soldering difficulty, and affect the performance and reliability of the circuit.

1. Increased soldering difficulty: Without flux, the solder may be difficult to flow to the soldering point, resulting in loose soldering, prone to cold soldering or poor soldering.

2. Reduce welding quality: Without the help of flux, the soldering point may not be smooth enough, with burrs or unevenness, which may affect the normal operation of the circuit.

3. Affect circuit performance and reliability: Flux can reduce the resistance of the soldering point and improve the conductivity of the circuit. Without flux, the resistance of the soldering point may increase, affecting the performance and stability of the circuit.

In addition, the flux can also prevent oxidation to a certain extent, protect the soldering point from the influence of the external environment, thereby improving the life of the circuit. Therefore, in the soldering process of printed circuit boards, it is very important to use the soldering flux correctly.

What is an alternative to soldering flux?

Alternatives to printed circuit board soldering flux include no-clean soldering flux, special solder resist for printed circuit boards, water-based cleaning agents and dry ice cleaning technology. ‌

1. No-clean soldering flux is a new type of soldering flux that does not contain halide activators. It does not need to be cleaned after use, which can save investment in cleaning equipment and cleaning solvents, while reducing the emission of waste gas and wastewater, and the pollution to the environment is also reduced accordingly.

2. The main function of the ‌PCB solder mask‌ is to prevent “wiring” and short circuits during wave soldering and protect the PCB permanently. In addition, it can save solder, reduce the weight of the PCB, and reduce costs.

3. As a new type of cleaning medium, the ‌water-based cleaning agent‌ achieves cleaning through the wetting, dissolution, emulsification, saponification, chelation and other effects of the surfactants, emulsifiers, penetrants, etc.

4. The ‌dry ice cleaning technology‌ uses extremely low-temperature dry ice particles to spray onto the treated object under the action of compressed air, so that the dirt is rapidly frozen to brittleness and burst, and then vaporized to take away the dirt.

These substitutes have their own characteristics and are suitable for different application scenarios and technical requirements. When choosing, specific process requirements and cost-effectiveness must be considered.

What does rosin do when soldering?

In the process of printed circuit board soldering, rosin plays a vital role. It is mainly used as a flux to help the soldering process be smoother and more efficient. The role of rosin is reflected in the following aspects:

‌Removing oxide film‌: Rosin can remove the oxide film formed on the copper surface due to contact with air. These oxide films will prevent the tin from wetting the copper wire, thus affecting the quality of welding.

‌Preventing re-oxidation‌: Rosin can not only remove the oxide film, but also prevent the soldering surface from re-oxidizing during the welding process, which helps to maintain the stability and reliability of the welding point.

‌Isolating air‌: Under high temperature conditions of welding, rosin can isolate the air and prevent oxidation of the metal surface.

In summary, rosin plays an important role in the soldering process of printed circuit boards. Through its fluxing effect, it improves the quality and reliability of soldering and is one of the indispensable materials in electronic manufacturing‌.

Conclusion:

Flux is a key part of the soldering process. Without it, your solder will not flow smoothly through the joint and the solder will not adhere properly to the various components on the circuit board. High-quality flux is necessary to produce good solder joints.

BEST Technology is a professional PCB circuit board manufacturer with many years of experience in PCB circuit board welding. The circuit boards it produces are of extremely high quality. We have the most extensive experience to deal with all aspects of PCB welding issues.

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