Archive for August, 2016

Generally there are two methods to do PCB outline, routing and punching.

Routing is suit for those simple boards with simple outline. But it is easy to cause burr on the edge. Also, if don’t make the tooling holes well, the boards may be easy moving while routing, which cause to the outline crooked.-

So, If you need the outline more precision and nice, the best way is to custom a tool for punching, in such way, the outline shape is very exact and no so much burr on the edge. It is used for those boards in big panel with small boards, special outline as well as high precision boards. Punching also can speed up the production lead time.  But for such way the cost is expensive than routing.

FR1 is basically the same as FR2. FR1 has a higher TG of 130^oC instead of 105^oC for FR2. Some laminate manufacturers who produce FR1 may not produce FR2 since the cost and usage are similar and it is not cost effective for having both.

FR3 is also basically FR2. But instead of phenolic resin it uses an epoxy resin binder.

FR4 (FR = Flame Retardent )is a glass fiber epoxy laminate. It is the most commonly used PCB material. 1.60 mm (0.062inch). FR4 uses 8 layers glass fiber material. The maximum ambient temperature is between 120^o and 130^oC, depending on thickness.

In China FR4 is the most widely used PCB base material, next is FR1 then FR2. But FR1 and FR2 are usually used for 1-layer PCBs because they are not good for passing through holes. FR3 is not recommended to building multi-layer PCBs. FR4 is the best selection. FR4 is widely used because it is good to make from one- layer to multi-layer PCBs. With only FR4, PCB companies can make all kinds of PCBs, which leaves the management and quality control much easier, and eventually it can reduce the cost!

Form the analysis above it is obvious that FR4 is the best selection to make PCBs in market. Some materials may be cheaper but it can only be used to make one-layer boards, and the reliability of the boards made by these materials is not good. So they are only used for one-layer and very simple boards.

Of course PCB can make no solder mask on both side, just make sure the solder mask layer (GTS& GBS) on your Gerber file is empty, or let us know you don’t want to make solder mask while quoting or before production, then we won’t make solder mask on both side, just print the circuits as you want.

It’s okay to make different solder mask on top or bottom side only. Such as 50um on top side and 20um on bottom side. For 2 OZ board, the area without trace, solder mask thickness can be 40-50um, and after three or four times printing, developing, drying, the thickness of solder mask over copper trace can also reach up to 40-50um.

The Gerber format is an open 2D binary vector image file format. It is the standard file used by printed circuit board (PCB) industry software to describe the printed circuit board images: copper layers, solder mask, legend, etc.

Gerber files should be inside a .rar or.zip archive with standard file extensions:
Extension                       Layer

• pcbname.GTL                 Top Copper
• pcbname.GTS                 Top Soldermask
• pcbname.GTO                 Top Silkscreen

• pcbname.GBL                 Bottom copper

• pcbname.GBS                 Bottom Soldermask:
• pcbname.GBO                 Bottom Silkscreen:
• pcbname.TXT                  Drills
• pcbname.GML/GKO        *Board Outline:
• 4 layer board also need
• pcbname.GL2                   Inner Layer2
• pcbname.GL3                   Inner Layer3

Notes: Gerber file must be RS-274X format.  Drill file(pcbname.TXT) should be Excellon format.
PCB Outline is required.

Gerber file is used for manufacturing process.

Yes, we can make groove on Ceramic PCB. But the technology to make groove is different from FR4 PCB, MCPCB.

As you know, FR4 PCB, MCPCB, the substrate is rigid, so we can rout to get the groove, but ceramic PCB is fragile, so we can not use rout on the Ceramic substrate. Normally, we use laser cutting to make the holes on Ceramic PCB, you may think we should use layer cutting, but it is not available, because if use laser, then it will be cutting through. So to make a tool is necessary, that’s correct, we make a tool to form the groove at the substrate stage.

DCB is abbreviation of Direct Bonding Copper. It is an electrical composites with high thermal conductivity and high dielectric strength. Which formed by the copper foil and the ceramic substrate suffering high temperature melting and diffusion process in an inert gas. In power electronics industry, the DCB promoted module package chip interconnect technology development and stimulate power electronics products towards on high power density, multi-set, high-performance low-cost.

The advantage of DCB PCB:

• the copper foil and ceramic can be bonded directly, which have good thermal conductivity, usually thermal conductivity of aluminum -DBC is 24 ~ 28 W / (m K), AlN-DBC is 170 ~ 220 W / (m · K).
• The stability of ceramic substrate makes DCB has a very excellent insulation properties under various conditions.
• Coefficient of thermal expansion close to the silicon enables semiconductor chip which soldered on board to avoid the stress caused by temperature changes, therefore can greatly extend the life of semiconductor products.
• Can process all types of graphics and lines like PCB, and strong current conducting capabilities make it easy to achieve board-on-chip interconnection function, the maximum carrying capacity will be up to 100 amps / millimeter.

The application of DCB

• Energy-saving control of appliances.
• Energy-saving control of industrial electrical.
• The transportation of wind, solar and other new energy.
• New type solar panels.

Parameters of DCB

The flatness tolerance value of DCB

Parameters of ceramic substrate

X-out board means that the boards are not qualified. The trace may damage during the production. Normally we will do some obvious mark to distinguish the X-out board.

When we make the boards in panel, it will be easy to have X-out board, and what’s more, when we panel several pieces board in a panel, there will be more pieces for X-out board.

Some of the SMT manufacture didn’t accept the X-out board, since it will influence the production efficiency.

But this kind of circuit board and can’t absolutely avoid in the process, so even the plate number, the more the number of circuit board factory scrap will be, the more relative costs will increase.

So circuit board manufacturers hope that the less number of plate, the better, because it can avoid the loss of X – board, the sheep wool or out, of course, if the board factory has been unable to overcome the loss of X – board, the final price will respond to the customer.