Main Reasons for Blackening of The Electroplated Gold Layer in PCB Processing

About the causes and solutions of the blackening of the electroplated gold layer, here are three common causes of problems for reference.

1. Thickness control of electroplated nickel layer

The blackening problem of the electroplated gold layer has a certain relationship with the thickness of the electroplated nickel layer. In fact, the gold layer of PCB electroplating is generally very thin, and many surface problems reflected in gold electroplating are caused by the poor performance of electroplating nickel. Generally, the thin electroplating nickel layer will cause the appearance of the product to be white and black. Therefore, this is the first item to be checked by plant engineering technicians. Generally, the thickness of the nickel layer that needs to be electroplated to about 5UM is sufficient.

2. The potion condition of electroplating nickel cylinder

About the nickel cylinder. If the potion of the nickel tank is not well maintained for a long time and carbon treatment is not carried out in time, the nickel layer plated out will be prone to flake crystals, and the hardness and brittleness of the coating will increase. Seriously, there will be a problem of blackened plating. This is a control point that many people tend to ignore. It is also often an important cause of problems. Therefore, please carefully check the potion condition of your factory production line, make a comparative analysis, and carry out a thorough carbon treatment in time to restore the potion’s activity and the cleanliness of the electroplating solution. It’d be a bigger deal if it wasn’t for carbon processing.

3. Control of gold cylinder
Next is the control of the gold cylinder. Generally, as long as good potion filtration and replenishment are maintained, the pollution degree and stability of the gold tank will be better than that of the nickel tank. But you need to pay attention to check whether the following aspects are good:
(1) Is the addition of gold tank supplements sufficient and excessive?
(2) How is the pH control of the potion?
(3) How about the conductive salt? If there is no problem with the inspection result, use the AA machine to analyze the content of impurities in the solution and maintain the potion status of the margin tank. Finally, don’t forget to check whether the gold cylinder filter cotton core has not been replaced for a long time. If so, it means that your control is not strict. Just replace it as soon as possible.