Our common computer board is basically an epoxy glass cloth double-sided PCB board circuit board, and one side of the board is the component foot soldering surface on the other side.
It can be seen that the solder joints are very regular, and the component legs of these solder joints are called PCB pads. Why are other copper wire patterns not tinned?
Because in addition to solder pads and other parts, the rest of the surface has a wave solder mask. The majority of its surface solder masks are green, and a few are yellow, black, blue, etc. Therefore, solder resist oils are often called green oil in PCB board circuit boards. Its role is to prevent bridging during wave soldering, improve soldering quality and save solder.
It is also a permanent protective layer for printed circuit boards (PCBs). It can prevent moisture, corrosion, mold, and mechanical abrasion.
From the outside, the surface is smooth and bright green solder mask, which is a photo-sensitive heat-cured green oil film for the film.
Not only does the appearance look better, what is important is the high accuracy of its pads, which improves the reliability of solder joints.
PCB board circuit board is not tin on the following situations.
1, PCB circuit board oxidation, PCB board is not on the tin.
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 replace another solder paste try.
4. The problem of battery cells, this is the most common problem, because the battery is generally stainless steel, to be plated with a layer of chromium to tin.
If the plating is oily or poorly plated, it will not be tinted. Try using 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 electric heating table to see whether the battery can be tin.