During the proofing process of the PCB circuit board, sometimes it is found that the gold plating layer of the PCB is blackened. So, what is the reason for the blackening of the gold plating layer of PCB?
1. Thickness control of electroplating nickel layer
PCB electroplating gold layer is generally a very thin layer, which reflects that many problems on the electroplating gold surface are caused by poor performance of electroplating nickel. Generally, the electroplating nickel layer is thin, which will cause the appearance of the product to be whitish and black. Therefore, this is the first choice for engineers and technicians to check. Generally, it needs to be electroplated to a thickness of nickel layer of about 5u to solve the appearance of whitish and black. The problem.
2. The status of the electroplating nickel cylinder potion
If the nickel tank potion is not well maintained for a long time and carbon treatment is not carried out in time, then the electroplated nickel layer will easily produce flaky crystals, resulting in increased hardness and brittleness of the coating, and in severe cases, black coating will occur. Therefore, engineers and technicians need to carefully check the status of the potion in the production line, conduct comparative analysis, and conduct thorough carbon treatment in time to restore the activity of the potion and the cleanliness of the electroplating solution.
3. Golden cylinder control
As long as the filtration and replenishment of good potions are maintained, the pollution degree and stability of gold tanks will be better than that of nickel tanks, but engineers and technicians need to pay attention to check whether the following aspects are good:
(1) whether the gold tank supplements are sufficient and excessive ;
(2) Control of the PH value of the potion;
(3) What is the condition of the conductive salt?
If the result of the inspection by the engineering and technical personnel is that there is no problem, then use the AA machine to analyze the impurity content in the solution to ensure the state of the potion. Finally, don't forget to check whether the gold cylinder filter cotton core has not been replaced for a long time?
