Why is the Double side PCB pad not tinned?

Why is the Double side PCB pad not tinned?

Our common computer boards are basically epoxy resin glass cloth-based double-sided PCB circuit boards, one of which is for inserting components and the other is for component pin soldering.

It can be seen that the solder joints are very regular. The discrete soldering surfaces of the component legs of these solder joints are called PCB pads. Why are other copper conductor 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 phenomenon during wave soldering, improve soldering quality and save solder.

It is also the permanent protective layer of the PCB board, 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 on the film.

Not only does the appearance look better, but it is also important that the pads are more accurate, which improves the reliability of the solder joints.

PCB board circuit board does not have tin on 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 cell,

    Then use the desoldering station or electric heating station to heat to see if the battery can be tinned.