There are as many as 20 processes in the design and manufacture of PCB. The problem of insufficient solder on the circuit board may lead to such problems as sand hole, broken line, line dog tooth, open circuit, young line of line sand hole; When the insufficient solder, the pore is not copper; The quality of tin removal is not clean (the number of times to return tin will affect the tin removal of the coating), so it is necessary to reweld or even abandon the previous work, and need to be remade when the tin is not good enough. Therefore, in the PCB industry, it is important to understand the causes of poor solder paste.
The appearance of solder paste defects is generally related to the cleanliness of the surface of the PCB empty plate. If there is no pollution, there will be basically no tin paste defects. Second, the soldering flux and temperature of the solder paste itself are poor.
Then the common printed circuit board tin paste defects are mainly reflected in the following points:
1. The composition of the bath solution is misaligned, the current density is too small, and the electroplating time is too short.
2. The anode is too few and unevenly distributed.
3. A small or excessive amount of tin polish.
4. The anode is too long, the current density is too large, the density of local wire is too thin, and the light agent is out of balance.
5. There is residual film or organic matter in the part before plating. 6. The current density is too high, the plating bath filtration is insufficient.
Then we summarize the improvement and prevention of the adverse situation of PCB plate：
1. The composition of the liquid is added in time to increase the current density and prolong the electroplating time.
2. Check anode consumption at random. Add anode with reasonable consumption.
3. Hirschner trough analysis adjusts the content of light agent.
4. Adjust the distribution of anode, reduce the current density, design the wiring or splicing board reasonably, adjust the light agent.
5. Strengthen the pretreatment of plating.
6. Reduce current density and regularly maintain or degrade the filter system.
7. Strictly control storage process storage time and environmental conditions,pcb manufacturing process strict operation.
8. Use solvent to wash sundries, if it is silicone oil, then you need to use a special cleaning solvent for washing .
9.Controlling the temperature of PCB welding at 55-80 ℃ and ensuring sufficient preheating time.
10. Use the flux correctly.