Analysis of the causes of pinholes in the copper plating layer in the copper plating process of printed circuit boards

This article discusses the causes of pinholes in the copper plating layer in the copper plating process of printed circuit boards, and proposes ways to find pinholes in the copper plating layer for reference.

1.Possible causes of pinholes in the copper plating layer:

The chloride ion in the plating solution is too low, the air stirring is uneven, there are granular impurities in the plating solution, there is organic pollution in the plating solution, and there is pollution on the board surface.

2.Ways to find pinholes in the copper plating layer:

3.Uneven air stirring:

To analyze the causes of pinholes in the copper plating layer, first check whether the air stirring system is normal; if the stirring is uneven, it will affect the filtering effect of the filtration system. You can use a bare board for trial plating. After strengthening the filtration, if there are no pinholes in the copper plating layer of the bare board for trial plating, it indicates that it is caused by uneven air stirring, and the air stirring should be strengthened to solve it; if there are still pinholes in the copper plating layer, you can check from other aspects.

3.The chloride ion in the plating solution is too low:

The second aspect of analyzing the cause of pinholes in the copper plating layer is to check the chloride ion in the plating solution and analyze the concentration of chloride ions in the plating solution; chloride ions are activators for phosphor copper anodes, which can help phosphor copper anodes dissolve normally. When the concentration of chloride ions is lower than 20 mg/L, a striped rough plating layer will be produced, and pinholes and scorching will occur. If the chloride ion is too low, it can be solved by adding hydrochloric acid, and try plating with a bare board. If there are still pinholes in the copper plating of the bare board, check from other aspects.

4.There are granular suspended matter in the plating solution:

Observe the shape of the pinholes. If they are irregular, it indicates that there are granular suspended matter; first, strengthen the filtration, and then try plating with a bare board. If there are no pinholes in the copper plating, it indicates that the plating solution is too dirty; if there are still irregular pinholes in the copper plating, it indicates that it is caused by granular matter brought by the previous process. If no pinholes are found after electroplating on the bare board, electroplating with a drilled board to see if there are pinholes.

5.Organic contamination in the plating solution:

Observe the shape of the pinholes. If they are round, it indicates that they are caused by organic pollutants. First, use carbon treatment and test plating with a bare board. If there are no pinholes in the copper plating layer in the bare board, it indicates that there is organic contamination in the plating solution, which may be caused by copper brightener and other reagents. If there are still pinholes in the copper plating layer in the bare board, it indicates that it is caused by the previous process. You can use a bare board to print only the circuit diagram for test plating. If there are no pinholes in the copper plating layer, it indicates that it is caused by ink and developer residues. If there are no pinholes in the copper plating layer, you can check other processes.

6.Pinholes will also occur if the surface treatment of the circuit board is not clean. After the circuit board is treated with dilute sulfuric acid and degreasing solution, the circuit board is electroplated. If no pinholes are found, check whether the brush machine will cause pollution. If there are still contaminations, check other processes.

There are many reasons for the pinholes in the copper plating layer of the printed circuit board. The above points are for your reference and hope to be helpful.