The unique features of different colored PCBs

In the manufacturing process of PCB (printed circuit board), whether it is additive or subtractive, the copper layer will eventually expose a smooth and unprotected surface. However, pure copper is very easy to oxidize after contact with oxygen in the air. Once oxidized, copper will become a poor conductor of electricity, which will seriously damage the electrical performance of the entire PCB board. To effectively prevent the oxidation of copper, distinguish the soldering part from the non-soldering part of the PCB, and protect the surface of the PCB circuit board, design engineers have carefully developed a special coating-solder mask. This solder mask is evenly applied to the surface of the PCB board to form a protective layer with a certain thickness, thereby isolating the copper from the air. The colors of the solder mask are various, including green, blue, black, etc. Therefore, the PCB boards we finally see are distinguished by different colors such as green board, blue board, black board, etc.

                                             01 Green board features        

1. Visual friendliness: Given the particularity of the PCB board manufacturing process, the quality inspection of many lines still needs to rely on naked-eye observation and identification. Green is less irritating to the eyes, and it is not easy to cause fatigue after long-term observation.
2. Cost-effectiveness: As a mainstream color, green naturally purchases more paint, so the purchase cost is relatively low. In addition, the use of uniform color paint in mass production can significantly reduce the cost of line change.
3. High instrument recognition: In the SMT (surface mount technology) welding process, including tinning, patch, and the final AOI (automatic optical inspection) verification, optical positioning calibration is required. The green background shows a better instrument recognition effect in these processes.

                                         02 Blue board features        

1. Novel and high-end: The blue PCB board gives people a novel and high-end feeling with its unique color.
2. Insufficient hardness: However, the hardness of the blue solder mask is relatively low and it is easy to scratch, which leads to an increase in defective products during the production process of PCB manufacturers.
3. Strong fluidity: The fluidity of the blue solder mask is relatively large, which is prone to problems such as oil accumulation and uneven oil. Therefore, during the production process, the PCB board needs to be placed flat and cannot be placed vertically, which takes up more space.
4. Long baking time: In addition, the baking time of blue PCB boards is long, and they are easy to get dirty, and they are easy to get film prints after packaging.

                                        03 Black board Features        

The surface traces of black PCB are almost completely covered, which makes it very difficult to repair in the later stage. At the same time, the difficulty of hole punching in black PCB is also higher, so the yield rate is relatively low. These factors together lead to the relatively high price of black PCB.

                                      04 White board Features        

1. High-temperature resistance Reflow soldering temperature resistance: usually needs to withstand high temperature of 260°C (peak) without discoloration or peeling.Wave soldering resistance: no warping or cracking for a long time at 250°C.
2. Excellent insulation performance High resistivity (＞10¹²Ω·cm) to prevent circuit short circuits. High voltage resistance: some high-voltage PCBs require voltage resistance of ＞1kV.
3. Strong adhesion Can be firmly attached to different PCB materials such as FR-4, aluminum substrate, ceramic substrate, etc. Verify the adhesion level through the Baige test (ASTM D3359) (usually requires ≥4B).
4. Chemical corrosion resistance Resistant to corrosion by flux, alcohol, isopropyl alcohol (IPA), and acidic/alkaline cleaning agents. Some industrial PCBs need to resist salt spray tests (such as automotive electronics).
5. High hiding power and whiteness White ink need to completely cover the underlying copper foil or substrate color (especially on high-density PCBs). Whiteness is stable and does not turn yellow after long-term use (some contain anti-UV agents).