Is The Substrate Color Really Important In PCB Design?
Many people like to judge the quality of the motherboard according to the color of the PCB substrate. In fact, the color and performance of the motherboard are not directly related. The color of the surface of the PCB is actually the color of a solder resist (also known as solder resist). Its function is to prevent the solder from being wrongly soldered during the soldering process. At the same time, it has another function, which is to prevent the soldered components from being Line oxidation and corrosion during use reduce the failure rate.
Under normal circumstances, the PCB boards of large companies such as Huawei and ZTE are generally green, because the green technology is the most mature and simple. In extreme cases, there will be red, white, blue, yellow, matt colors, and in extreme cases, black, purple, chrysanthemum, bright green, etc. Under normal circumstances, white is the production of lighting products must be used To the white PCB board, the other colors are mostly product grading system, different companies are different, some use red to indicate the experiment board, some use blue to indicate the key board, and some use black to indicate the computer. Internal plate. Each has its own rules and is not detailed.
The most common color of PCB boards is green, which is green board, also called green oil. Green solder resist inks are the oldest, cheapest and most popular. Generally speaking, the board-level products of the whole electronics have to go through the board making process and the patching process. In the process of making the board, there are several processes that go through the yellow light room, and the green color in the yellow light room is better, but this is not the case. Main. In SMT soldering, it is necessary to go through the tin and the post and the final AOI check. These processes are all optically calibrated and calibrated. The green background color is better for the instrument.
Other common ones are red, yellow, green, blue and black. Due to the problem of the process, many lines of inspection are still dependent on the workers' eyes (of course, most of them are now tested with flying probes). It’s a very tiring job to keep watching the board with strong light, and green is the least hurting eye. So most of them use green.
Blue and black are made of cobalt and carbon, respectively, and have a certain conductivity, so there is a risk of short circuit. The green PCB is more environmentally friendly, and does not release toxic gases when used in a high temperature environment.
In fact, the color is too deep, which will often improve the difficulty of inspection and maintenance of the motherboard. Take the earliest black PCB substrate as an example. In the process of washing the PCB, black is the most likely to cause chromatic aberration. If the raw materials used in the PCB factory and the self-made process are slightly deviated, the PCB defect rate will increase due to the color difference. Since the black PCB's circuit traces are difficult to identify, it will increase the difficulty of later maintenance and debugging. Generally, motherboard manufacturers will not easily use black PCBs. Therefore, we have seen that even the products with extremely high quality requirements such as military and industrial products use only green PCB substrates.
So what is the effect of solder mask ink color on the board? The ink has no effect on the finished product, but it has a great influence on the semi-finished product, mainly affecting the difficulty of semi-finished product production. In addition, some people say that color still has an effect on the PCB. Indeed, if there are matt green, sun green, dark green, light green, etc. in the green, the color is a little different, the color is too light, it is easy to see the plug. After the hole process, the appearance of the board is not good, the color is too deep, then some manufacturers' inks are not good enough, the ratio of resin and dye is problematic, there will be problems such as bubbles, and the ink will be dropped in the final curing. The problem of ink ratio can be seen in slight changes in color, which is not felt without years of experience. (This problem is a bit complicated. Some inks are used in contrast to different machines. There are electrostatic spraying, spraying, screen printing, ink is different, the ratio is different, the color is a little different, and the wrong one will be a little small. The problem, but in fact, for the finished board, these are the appearance problems, and have no effect on the product itself)
Although the color of the ink has no effect on the plate, the effect of the thickness of the ink on the impedance is very large, especially the water-gold plate. The thickness of the plate is very strict. According to experience, the red ink, bubble, thickness Better control, the first is that the price of ink is more expensive, there is indeed a good thing. The second is that this color can cover some defects on the line, and the green color will be more obvious. The third is the imaging link. I have been to several large PCB manufacturers. Red and yellow seem to be more stable, green is not necessarily, and white is the most difficult to control. In this way, there are many other small details, maybe 4 I can't touch it in 5 years. I may have just encountered it when I got to work. After I came across it, there is basically no solution. It is inexplicable and inexplicably good. This is a very interesting thing in the soldering process of the entire PCB.
In summary, color has no influence on the performance of the motherboard, and it does not play a very important decisive role in PCB design. However, in the design of pcb, strictly control every detail in each link is a piece. Whether the PCB board is a good premise. We know that different color PCB motherboards are more for the product's selling phase. Therefore, users are not recommended to use the PCB color as a reference factor for the optional motherboard.