The appearance of tin defects on PCB is generally related to the cleanliness of PCB empty board surface. If there is no pollution, there will basically be no tin defects. Second, when tin is applied, the flux itself is bad, temperature, etc. So the common electrical tin defects of printed circuit boards are mainly reflected in the following points:

1, the plate surface coating has particle impurities, or the substrate in the manufacturing process has polished particles left in the line surface.

2. The board surface is covered with grease, impurities and other sundries, or silicone oil residue

3, the surface of the sheet electricity can not be tin, the surface coating has particle impurities.

4, high potential coating rough, burning plate phenomenon, plate surface has flake electricity can not tin.

5, substrate or parts of tin surface oxidation and copper surface dark situation is serious.

6, one side of the coating is complete, one side of the coating is bad, low potential hole edge has obvious bright edge phenomenon.

7, low potential hole has obvious bright edge phenomenon, high potential coating rough, burning plate phenomenon.

8, welding process does not ensure enough temperature or time, or is not the correct use of flux

9, low potential large area tin plating, the board has a slight dark red or red, one side of the coating is complete, one side of the coating is bad.

The reasons for bad circuit board tin are mainly reflected in the following points:

1. Bath liquid composition imbalance, current density is too small, plating time is too short.

2. Too few and unevenly distributed anodes.

3. A small or excessive amount of tin gloss.

4. The anode is too long, the current density is too high, the local wire density is too thin, and the optical agent is maladjusted.

5. Local residual film or organic matter before plating.

6. Current density is too high and plating solution filtration is insufficient.