Our common computer boards are basically double-sided PCB boards based on epoxy resin glass cloth. One side is for inserting components and the other side is for component pin soldering. It can be seen that the solder joints are very regular. The discrete soldering surface of the component foot is called the PCB board pad. Why are other copper wire patterns not tinned?

　　Because in addition to the soldering pads and other parts, the surface of the remaining parts has a layer of solder mask that is resistant to wave soldering. Most of the solder mask on the surface is green, and a few use yellow, black, blue, etc. Therefore, solder mask oil is often called green oil in the PCB circuit board industry. Its function is to prevent bridging during wave soldering, improve soldering quality and save solder.

It is also a permanent protective layer for PCB printed boards, which can prevent moisture, corrosion, mildew and mechanical scratches.

　　 Viewed from the outside, the surface is smooth and bright green solder mask, which is photosensitive and thermally cured green oil for the film on the board.

　　 not only looks good, but it is also important that its pads are more accurate, which improves the reliability of solder joints.

　　 PCB board circuit board does not have the following situations.

　　 1. The PCB circuit board is oxidized, and the PCB board is not tinned.

　　2. The temperature of the furnace is too low, or the speed is too fast, and the tin does not melt.

　　 3. The solder paste problem, you can try another solder paste.

　　4. The battery problem, this is the most common problem, because the battery is generally stainless steel, and it needs to be plated with a layer of chromium to be tinned.

　　 If the plating layer is oily or the plating is not good, it will not be tinned. You can try to solder with a soldering iron. Or put some solder paste on the battery, and then use a desoldering station or electric heating station to heat it to see if the battery can be tinned.