Solder mask(solder resist) is used to provide media and mechanical shielding during and after the soldering process. Solder masks are used to provide dielectric and mechanical shielding during and after the soldering process. The material of the solder resist can be liquid or dry.
Colors of PCB Solder mask
PCB solder mask can be displayed in different colors including green, white, blue, black, red, yellow, matt, purple, daisy, bright green, matte black, matte green, etc. Under normal circumstances, white is the production of LED lighting these products must be used in white PCB circuit boards, the other The color is mostly because of the product classification system, each company is different, some use red to indicate the experimental board, some use blue to indicate the focus of the board, some use black to indicate the computer board, some use black to indicate the computer board. Some use black to indicate that the board is used for the internal computer.
PCB ink does not affect the finished board. But for in the semi-finished products have a great impact, such as green has a matte Green, sun green, dark green, light green, etc., there is a slight color difference, the color is too light, and it is easy to see the appearance of the board after plugging the hole process is not good. The color is too dark, some circuit board factories use ink quality is not good enough, resin and dye ratio problems, there will be bubbles, and so on. If the ink is not good enough, the resin and dye ratio is not good enough, there will be bubbles and other problems, and the ink will fall off in the final curing.
The role of PCB solder mask
In the printed circuit board (PCB) processing production process, solder-resist ink coating is a very critical process. Soldermask on the PCB board’s main function is to protect the circuit and prevent the conductor. The function is to protect the circuit, prevent conductors and other undesirable tin; prevent electrical shorts between conductors caused by moisture or chemicals; to prevent the PCB board after the process of production and electrical assembly in the bad. Process production and electrical installation in the bad take caused by the circuit breakers; and a variety of harsh environments on the PCB board invasion and so on.
Both sides of the PCB board are copper layers, no solder mask PCB board exposed to the air is easy to be oxidized, and becomes a defective product, but also affects the PCB board’s Electrical performance. Therefore, the PCB circuit board surface must have a layer that can block the PCB and the air oxidation reaction of the protective coating, and this layer of coating is covered with solder paint material solder resist layer. Various colors of solder-resist paint also came into being, forming a colorful PCB circuit board, and solder-resist color has nothing to do with the quality and electrical performance of the PCB.
Why do common PCBs choose to use green solder masks?
(1) from the function, green ink added to the composition has long been fixed, basically, the equipment potion is for green, easy to develop, and not easy to come off. It is not easy to come off.
(2) for the appearance of the inspection, and the copper surface (yellow) contrast is obvious, it is easier to detect scratches offset and other defects. Other miscellaneous colored oils are added to change the color of some of the powder substances. It is a relatively high cost for PCB production. But for the finished product, some colors look more high-end than green color looks high-end. In addition, the PCB quality inspection process in the circuit board factory PCB manual visual inspection, for PCB manufacturers, green is more eye protection, and visual inspection of the staff is also more friendly. For the visual inspection staff is also more friendly.
(3) Green ink can be done with smaller errors, and smaller areas, and can be done with higher precision, green, red, and blue than other colors. Green, red, and blue have higher design accuracy than other colors.
(4) Green ink has better characteristics than other colors. Green ink has better characteristics than other colors, especially green ink has better hole plugging characteristics than other colors. Green ink has better characteristics than other colors, especially the hole-plugging characteristics of green ink.
(5) Green ink is relatively low cost. Due to the production process, green is the mainstream, the most mature process, and the most simple, naturally green ink procurement will also be larger Green ink purchasing volume will be larger, so its purchasing cost relative to other colors will be lower.
(6) PCB processing, and electronics production, including the production of boards and SMT patches, during which there are several processes to go through the yellow room, and the green PCB board in the yellow room. The visual effect of the green PCB in the yellow light room is the best.
(7) In the SMT patch processing, tin, patch, and AOI calibration of these steps, all need optical positioning calibration, and green PCB instrument identification The green color of the base plate is more friendly.
(8) Other solder mask colors, such as blue and black are doped with cobalt and carbon, respectively, because of the weak conductivity, there will be a risk of short circuit. In addition, like black purple, and blue lights, the PCB substrate color is too dark, which will increase the difficulty of inspection and maintenance of the motherboard, and the process is not well controlled.
Soldermask requirements
PCB solder mask must have a good film, its thickness is a standard requirement. At present, most of the board manufacturers are in accordance with the U.S. civilian standards IPC-SM – 840C specification for identification. 840C specification for identification. In this standard, the thickness of solder resist film is not limited to level 1 products; the minimum thickness of solder resist film for level 2 products is 10m; the minimum thickness of level 3 products should be 18m. The flame resistance of the solder mask is usually based on the UL agency’s specifications and must pass the requirements of UL94V-0 (UL94 – Plastics for Use as Components in Appliances and Equipment). UL94V-0 (UL94 – Flammability Tests for Plastics Used as Components in Appliances and Equipment).
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