Posts Tagged ‘copper’

What is the thermal conductivity coefficient of copper?

Wednesday, October 9th, 2024

What is the Thermal Conductivity Coefficient?

The thermal conductivity coefficient is a measure of how well a material conducts heat. It’s represented by the symbol k or λ, and it is measured in units of watts per meter-kelvin (W/m·K). It’s defined as the amount of heat that passes through a material 1 meter thick, with a temperature difference of 1 degree (K or °C) between its two sides, in one second, over an area of 1 square meter.

In general, the higher the thermal conductivity coefficient, the better the material is at transferring heat, so in some high power or power supply electronics, thermal conductivity value is important to transfer heat out. Materials with a high k value, like metals such as copper, allow heat to flow through them easily, which is why they are used in applications that require efficient heat dissipation. In contrast, materials with low thermal conductivity coefficients, such as insulators, are used to minimize heat transfer and preserve energy.

The thermal conductivity is only for the heat transfer form with thermal conductivity. When there are other forms of heat transfer, such as radiation, convection, mass transfer and other forms of heat transfer, the composite heat transfer relationship. The composite heat transfer relationship is often referred to as the apparent thermal conductivity, the dominant thermal conductivity, or the effective thermal transmissivity of material. In addition, the thermal conductivity is for homogeneous materials, in the actual situation, there are also porous, multi-layer, multi-structure, anisotropic materials, the thermal conductivity obtained by this material is actually a comprehensive thermal conductivity performance, also known as the average thermal conductivity.

According to Fourier’s law, the thermal conductivity is defined as

Where x is the direction of heat flow.

qx’’ is the heat flux in this direction in W/m2, and another is the temperature gradient in this direction, expressed in K/m.

For an isotropic material, the thermal conductivity is the same in all directions.

What Is the k Value of Copper?

The thermal conductivity of copper is about 401W/m.K. Copper is a transition element, pure copper is a soft metal, when it is cut on the surface, it is red-orange, and its ductility is good, thermal conductivity is relatively high, so it is a more commonly used material in cables and electronic components, can be used as building materials, and it is composed of many kinds of alloys.

What is the thermal conductivity coefficient of copper?

Copper’s high k value meaning it can quickly absorb and distribute heat. That is why copper is used extensively in heat sinks, electrical wiring, and cooling systems. Because of this, it’s highly valued in industries that rely on rapid heat dissipation. Whether in electronics or heavy machinery, the high thermal conductivity of copper ensures that heat does not build up, preventing overheating.

Thermal Conductivity of Common Solid Materials

Here are the thermal conductivity values of some common materials:

Aluminum: 237 W/m·K at 300°C

Copper: 401 W/m·K at 100°C

Iron: 61 W/m·K at 18°C

Steel: 45 W/m·K at 18°C (for carbon steel with 1% carbon)

Silver: 412 W/m·K at 100°C

Graphite: 151 W/m·K at 0°C

These values highlight the differences in heat conduction across materials, with metals like copper and silver being among the most efficient conductors of heat, while materials like steel and graphite have comparatively lower conductivity.

Is Copper a Good Conductor of Heat?

Yes, copper is an exceptionally good conductor of heat. For example, in electronics, copper is often used to cool down processors by transferring heat away quickly, thus ensuring systems run smoothly without overheating. In plumbing, copper pipes help distribute hot water faster, enhancing energy efficiency. From cookware to cooling systems, copper’s outstanding ability to conduct heat makes it indispensable across many fields.

Copper vs. Aluminum PCB: Which is Better?

Both copper and aluminum are excellent conductors of heat in circuit boards manufacturing, but how do they compare? Let’s discuss them from below aspects:

1. Thermal conductivity

First, let’s take a look at the thermal conductivity of aluminum and copper, which is a key indicator of the material’s heat dissipation performance. The higher the thermal conductivity, the better the material’s ability to transfer heat.

Copper: 401W/m.k

Aluminum: 237W/m.k

It can be seen from the data that the thermal conductivity of copper is almost twice that of aluminum, which means that under the same conditions, copper can transfer heat more efficiently. For this reason, copper is often the material of choice in applications that require extremely high thermal performance.

2. Density

Aluminum: Density of about 2.7 g/cm³.

Copper: Density of about 8.96 g/cm³.

Copper is nearly three times as dense as aluminum, which makes copper much heavier than aluminum. In some weight-sensitive applications, such as portable electronic devices, heavy cooling components may affect the portability and user experience of the product. Therefore, in these scenarios, although aluminum is not as conductive as copper, it is still a very popular choice due to its lower weight.

3. Cost

The prices of aluminum materials are low, and processing costs are relatively low. At the same time, aluminum is easy to process into a variety of shapes, which makes aluminum very cost-effective in the manufacturing process. However, the cost of copper is much higher and the manufacturing process is more complex, so the overall cost is much higher than aluminum.

4. Corrosion resistance

Aluminum and copper also have significant differences in corrosion resistance. Aluminum has good oxidation resistance, and the aluminum oxide layer formed on the surface can effectively protect the internal material from further corrosion. However, the corrosion resistance of copper is relatively poor, and it is easy to generate patina (carbonate of copper) in humid environments, which not only affects the appearance but also reduces the heat dissipation performance.

Why Does Copper Have the Highest Thermal and Electrical Conductivity?

Copper has very good conductivity because it has a large number of freely moving electrons in its interior. When a voltage is added to both ends of a metal, the positive electrode piles up positive charges, and the negative electrode piles up negative charges, because the same charges attract each other and the dissimilar charges repel each other, forcing the electrons to move in a directional way, thus forming a current. In addition, copper has a very low resistivity of only 1.68×10^-8Ω·m, second only to silver, and is the second most widely used conductive material.

Copper’s good thermal conductivity is also related to its internal free electrons. Metal nuclei have a weak ability to bind electrons, allowing free electrons to move freely within the metal and transfer heat rapidly. When one end of a metal is heated, the electrons of atoms or molecules at that end absorb energy and begin to vibrate. These vibrations are passed on to the electrons of neighboring atoms or molecules, forming a heat flow ‌4. Copper is metal-bonded in a way that makes it easier for its electrons to transfer energy inside the metal, and thus heat faster.

Here is the end of this blog sharing, if you have other questions about copper material, welcome to e-mail us: sales@bestpcbs.com.

Why is copper used in printed circuit boards?

The main reason for using copper in printed circuit boards is that copper has good conductivity, which can greatly improve the conductivity of the circuit board and ensure that the connection between various components is more stable and reliable.

‌In addition, copper foil itself has high mechanical strength and stability, which can effectively prevent the printed circuit board from being damaged or deformed by the external environment.

In terms of high-frequency signal transmission, copper plating can effectively improve the conductor characteristics and impedance matching characteristics of the circuit board, protect the circuit board from oxidation or corrosion, thereby extending the service life of the circuit board and ensuring its stability and reliability.

Copper plating can reduce the voltage drop in the circuit, thereby improving the efficiency of power supply. In addition, copper plating can also enhance the mechanical strength of the PCB, so that it will not deform as much as possible during the welding process, improve the yield rate in the production process, and reduce circuit failures caused by deformation.

However, copper plating also has its disadvantages. For example, when soldering or repairing PCB samples, it may cause difficulty in replacing devices due to excessive heat dissipation, especially in the case of large devices. In addition, in RF circuits, copper plating may cause impedance mutation of the antenna, seriously affecting signal transmission.

How thick is the copper on a printed circuit board?

The thickness of copper foil on a printed circuit board is usually between 18μm and 70μm, but the specific thickness depends on the purpose of the circuit board, the voltage and current of the signal.

The most commonly used copper foil thickness is 35μm, because the copper foil thickness of 35μm is suitable for most application scenarios. However, for applications that need to carry higher power or higher current, such as high-power LED lights, power supply circuits, etc., 2OZ (about 70μm) or thicker copper foil may be selected to ensure the performance of the circuit board and the reliability and stability of electronic products.

In addition, the copper thickness of the circuit board is also affected by the thickness of its substrate. For example, the composite copper foil thickness on a substrate less than 1mm thick is about 18μm, while a copper foil thickness of 55μm may be used on a substrate greater than 5mm.

How do you choose PCB copper thickness?

When choosing PCB copper thickness, you need to consider multiple factors to ensure the performance, cost and production feasibility of the circuit board.

‌Application scenarios of circuit boards‌: For applications that need to carry high power or high current, you may need to choose thicker copper foil to ensure the stability and reliability of the circuit board‌. For general signal transmission, 1oz copper thickness is usually sufficient‌.

‌Number of layers and design of circuit boards‌: The inner layer of multilayer boards generally uses 1/2oz and 1/3oz copper thickness, while the outer layer uses 1oz or 1/2oz copper thickness‌.

‌Cost and process requirements‌: The thicker the copper foil, the higher the production cost. Therefore, it is necessary to consider cost factors while ensuring performance‌.

‌Special requirements‌: In some special application scenarios, such as when the circuit board needs to dissipate heat, copper foil with higher thermal conductivity should be selected to enhance the heat dissipation capacity of the circuit board‌.

What is the difference between 1 oz and 2 oz copper PCB?

The main difference between 1 oz and 2 oz copper PCB lies in the thickness of the copper foil and the current load it can withstand. ‌

‌Copper foil thickness‌: 1 oz copper thickness refers to 1 ounce of copper per square foot on the circuit board, while 2 oz copper thickness refers to 2 ounces of copper per square foot.

‌Application scenario‌: 1 oz copper thickness PCB is the most common standard and is suitable for most application scenarios. 2 oz copper thickness is suitable for application scenarios that need to carry higher power or higher current.

‌Electrical performance and heat dissipation performance‌: In theory, thicker copper foil can directly reduce the ground resistance by half, and the number of joules of heat generated per unit time during operation will also be reduced accordingly. At the same time, it can more effectively shield the electromagnetic interference between components and wires.

How thick is the copper on a 1 ounce copper PCB?

The copper thickness of 1 ounce copper on a PCB is about 35 microns. ‌

In PCB design and processing, the copper thickness is often expressed in ounces (oz) as a unit. Specifically, the thickness of 1 ounce of copper is about 35 microns, which is equivalent to 1.4 mils. Although this method of expression uses the weight unit ounce, it actually indirectly expresses the average thickness of the copper foil through the weight per unit area.

In the PCB industry, ounces are not only a unit of weight, but also used to express the thickness of copper foil, where 1oz means the thickness of 1 ounce of copper evenly laid on an area of 1 square foot. This method of expression is very common in the fields of electronic engineering and circuit board manufacturing to ensure that the conductivity and current carrying capacity of the circuit board meet the design requirements.

Which metals Cannot be used in printed circuit boards?

In the production of printed circuit boards, some metals are usually not used.

First of all, iron has poor conductivity and cannot meet the requirements of printed circuit boards for good conductive materials. Moreover, iron is easy to rust, which will affect the appearance of the circuit board and may also cause circuit short circuits or poor contact.

Lead is also not suitable for printed circuit boards. On the one hand, lead is a toxic heavy metal. With the improvement of environmental protection requirements, the use of lead-containing materials in the electronics industry is limited, and lead-containing solder in printed circuit boards has gradually been replaced by lead-free solder. On the other hand, lead has poor mechanical properties, low hardness and easy deformation, which may deform or damage the circuit board during manufacturing and use.

Mercury cannot be used in printed circuit boards. Mercury is extremely toxic and has serious harm to the human nervous system, immune system, etc. At the same time, mercury is liquid and volatile at room temperature, difficult to control, easy to cause leakage and pollution, and its conductivity is not ideal.

Although gold has advantages such as good conductivity, corrosion resistance and oxidation resistance, its cost is too high and it is not suitable for large-scale application in printed circuit boards. In addition, gold has low hardness and is easily scratched or worn, affecting the performance and reliability of the circuit board.

What is the major disadvantage of printed circuit boards?

The major disadvantages of printed circuit boards include disposable boards, environmental impact of etching, and compatibility issues. ‌

‌Disposable boards‌: Printed circuit boards are designed with one-time use in mind, which means that if the circuit board needs to be modified after printing, it will not be possible and a new board needs to be created from scratch.

‌Environmental impact of etching‌: The chemicals used in the etching process have a negative impact on the environment. Although the etching process is very effective for circuit board production, it is not environmentally friendly‌.

‌Compatibility issues‌: Before starting to make a circuit board, you need to determine the device you are designing for, which increases the complexity and potential risks of the design‌.

These shortcomings limit the use of printed circuit boards in some applications to a certain extent, especially in scenarios that require high customization or frequent modifications.

In short, copper printed circuit boards occupy an irreplaceable position in the electronics field with their excellent performance. From consumer electronics to communications, automotive electronics, and industrial control, it can be seen everywhere. Copper’s high electrical conductivity, good thermal conductivity, and strong machinability make it a key link connecting the electronic world.

What is the thermal conductivity value for copper?

The thermal conductivity of copper is about 401W/m·K. ‌

The thermal conductivity refers to the heat transferred through 1 square meter of area in 1 second under stable heat transfer conditions, with a temperature difference of 1 degree (K, ℃) on both sides of a 1 meter thick material. The unit is watt/meter·degree (W/(m·K)).

The thermal conductivity is a parameter to measure the thermal conductivity of a material. The larger the value, the better the thermal conductivity. Due to its high thermal conductivity, copper is often used to make radiators, heat conductors and other applications that require efficient heat transfer.

What is the thermal conductivity of copper at 25 C?

The thermal conductivity of copper is affected by many factors. On the one hand, temperature is an important influencing factor. Generally speaking, the thermal conductivity of copper decreases with increasing temperature.

At 25℃, the thermal conductivity of copper is about 401W/m.K, and at 100℃, the thermal conductivity of copper is 377W/m・K.

How do you measure thermal conductivity of copper?

The thermal conductivity of copper is usually measured by the steady-state method. ‌

The steady-state method is a classic method for measuring the thermal conductivity of thermal insulation materials. It uses the equilibrium state in which the heat transfer rate is equal to the heat dissipation rate during stable heat transfer.

This method has a simple and clear principle and high accuracy. Although the measurement time is long and the environmental conditions are high, it is suitable for measuring thermal conductivity materials at medium temperatures, especially for low thermal conductivity materials such as rock, plastic, rubber, glass, and thermal insulation materials.

In the steady-state method, commonly used methods include heat flow method, protected heat flow method, and protected hot plate method. The basic principles of these methods are similar, but some standards are formulated for different thermal insulation materials, and the test results are similar.

What metal has the highest thermal conductivity?

Silver has the highest thermal conductivity.

Among metals, silver has a thermal conductivity of 411W/(m·K), which is the highest value among all metals. This property of silver makes it the metal with the best thermal conductivity.

In contrast, copper has a thermal conductivity of 401W/(m·K), which is also very high, but still slightly lower than silver. Other metals such as gold and aluminum have thermal conductivities of 315W/(m·K) and 237W/(m·K), respectively, which are lower than silver and copper. Therefore, from the perspective of thermal conductivity, silver is undoubtedly the metal with the best thermal conductivity.

In addition, although the thermal conductivity of copper is also very high, reaching 401W/(m·K), second only to silver, among pure metals, the thermal conductivity of silver is still the highest. However, in practical applications, copper is widely used because of its good conductivity and relatively low cost.

Which metal is the poorest conductor of heat?

The metal with the worst thermal conductivity is iron. ‌

Among metal materials, the thermal conductivity of iron is 0.163, while that of copper and silver is, and that of aluminum is 0.5. These data indicate that the thermal conductivity of iron is significantly lower than that of other common metals. Therefore, it can be concluded that iron is the metal with the worst thermal conductivity‌.

Why copper has highest thermal conductivity?

Copper has the highest thermal conductivity‌, mainly because of its unique physical and chemical properties. The superior thermal conductivity of copper is mainly attributed to its crystal structure and electronic properties.

Copper is a metal with good electrical and thermal conductivity, which is due to the presence of a large number of free electrons in the crystals of copper. These free electrons can effectively transfer heat when colliding with metal cations in the crystal, making copper extremely thermally conductive.

The thermal conductivity of copper is about 400 W/m·K, which means that copper transfers much more heat per unit time than most other materials. The high thermal conductivity allows copper to quickly transfer heat away, with efficient heat dissipation.

What happens to copper when it is heated?

When copper is heated, its volume increases, its mass remains unchanged, and its density decreases. ‌

When copper is heated, its volume increases due to the property of thermal expansion and contraction. This is because when the copper block is heated, the distance between atoms increases, resulting in an increase in volume. At the same time, the mass of copper is a property of matter, which is only related to the amount of matter contained, and has nothing to do with the position, state, shape, and temperature of the object. Therefore, the mass of copper remains unchanged after heating.

In addition, when copper is heated in the air, if it reacts with oxygen, black copper oxide (CuO) will be generated on the surface. This chemical change will cause the color of copper to change from red to black.

In summary, when copper is heated, not only will its volume increase, its mass remain unchanged, and its density decrease, but it will also react with oxygen to generate copper oxide when heated in the air, resulting in a change in surface color.

Why does copper turn green?

Copper turns green because it is oxidized in the air to form copper rust. The main component of this copper rust is basic copper carbonate, which is green in color. ‌

Copper will be oxidized in the air to form copper rust. This rusting process is the result of a combination of factors, including the reaction of copper with oxygen, water vapor and carbon dioxide in the air.

Specifically, when copper is exposed to oxygen, water and carbon dioxide in humid air for a long time, a chemical reaction will occur to generate basic copper carbonate (Cu2(OH)2CO3), a green inorganic compound, so a green rust layer will form on the copper surface.

This process not only occurs on the surface of copper, but also because the main component of copper rust is basic copper carbonate, the color of copper rust is green, which makes the appearance of copper products appear green.

Copper has become the preferred material for heat conduction in many fields due to its high thermal conductivity, good processing performance and stable thermal conductivity. With the continuous advancement of science and technology, it is believed that copper will continue to play an important role in future development.