PCB The circuit board is in the proofing process , Sometimes I find out PCB Blackening of electroplated gold layer . that ,PCB What causes the blackening of electroplated gold layer ?
1、 Thickness control of nickel plating layer
PCB Electroplated gold layer is usually a very thin layer , Reflected in the surface problems of electroplated gold, many are caused by the poor performance of electroplated nickel . Generally, the nickel plating layer is thin , The appearance of the product will be white and black , Therefore, this is the first choice for engineers and technicians to check , It usually needs to be electroplated to 5μ The thickness of the nickel layer can solve the problem of white and black appearance .
2、 Liquid medicine condition of nickel plating cylinder
If the nickel tank potion cannot be well maintained for a long time , No timely carbon treatment , Then the nickel layer electroplated will easily produce flake crystals , Resulting in increased coating hardness 、 Brittleness enhancement , In severe cases, it will produce blackening coating phenomenon . Therefore, engineers and technicians need to carefully check the liquid medicine condition of the production line , Make a comparative analysis , And timely and thorough carbon treatment , So as to restore the activity of liquid medicine and the cleanness of electroplating solution .
3、 Gold cylinder control
As long as you keep good filtration and replenishment of potions , The contamination degree and stability of gold cylinder are better than nickel cylinder , However, engineers and technicians need to check whether the following aspects are good ：
(1) Whether the golden jar supplement is added enough and excessive ;
(2) Potion PH Value control ;
(3) How about the conductive salt .
If the result of the engineer's inspection is no problem , Reuse AA Analyze the impurity content in the solution with the machine , The state of the liquid medicine in the deposit tank . Last , Don't forget to check whether the gold cylinder filter cotton core has not been replaced for a long time ？
The above is the cause PCB Cause analysis of blackening of electroplated gold layer , Have you got it all ？
More content can be seen in official account. ：PCBA Information sharing