I believe everyone is no stranger to circuit boards. HDI PCB circuit boards have many colors, black, white, yellow, green, etc. Maybe many electronic enthusiasts will ask, why are HDI PCB mostly green Woolen cloth? Then let us discuss this issue together!
The green part on HDI PCB is called solder resist, and its composition is resin and pigment. The purpose is protection, insulation, dust prevention, etc. Specifically, the printed circuit board has copper foils on both sides. Copper is not as active as iron, aluminum and magnesium, but it is more reactive with oxygen in water. When oxygen and water vapor in the air come into contact with copper at room temperature, an oxidation reaction occurs. This will oxidize the copper foil and make the printed circuit board non-conductive.
In order to avoid the oxidation reaction of the copper foil and also make the surface of the PCB possible, solder resists have been used. Solder resist prevents it from adhering to unnecessary parts during the soldering process. At the same time, as a permanent protective film, it can protect the circuit pattern from dust, heat, moisture, etc., and maintain insulation.
When printing resist, add green pigment and the substrate will turn green. In other words, the color of solder resist is not only green, but also various colors, such as yellow, black, red, and purple. There are three reasons for using green: protect eyes; low cost; reduce errors; so many customers make green circuit boards according to their own needs, so do you know?
