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

From the outside, the green solder mask with smooth and bright appearance is a green oil for film-to-board photosensitive heat curing.

Not only does the appearance look good, but the most important thing is that the accuracy of the pads is high, which improves the reliability of the solder joints.

There are several situations in which the PCB board is not tinned.

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. Solder paste problem, you can try another type of solder paste.

4. The problem of battery, 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 electroplating layer has oil or the electroplating is not good, it will not be tinned. You can try it with a soldering iron to see if it can be soldered. Or put some solder paste on the battery, and then use a desoldering station or an electric heating station to heat it to see if the battery can be tinned.