|Ask the Experts|
September 23, 2019
Gold Edge Contact Rework
I am replating gold edge contact that need repair. After completing the bench-top replating process the board meets the required thickness specifications and passes a peel test.
However, the electroplating process leaves slight dark residue on the gold contacts. Is this acceptable? Can it easily be removed?
|Expert Panel Responses|
This is a great question. Most people use a pencil eraser to 'polish' the gold surface. It doesn't make it look perfect, but it does a good job of getting rid of the black spots and inconsistencies. Just be aware of the composition of the eraser, as it can leave contaminates behind, as well as being overly abrasive.
PinkPearl works, but I'm sure there are better available. Also dark tarnishing after replating is often a sign of too high of DC voltage through the plating process. Try backing off a few volt or a two and see if it alleviates the tarnishing.
IPC Training Coordinator
Adco Circuits Inc.
The "residue" might actually be a surface condition caused by the platingc onditions, usually by plating too quickly (too high current density). If this is the case, it is often possible to gently polish the contact using a soft pencil eraser (don't use an abrasive eraser meant for ink!).
Gently rub the contact to burnish the area. After this process, wipe the contact with alcohol to remove any organic residues, and re-test the thickness.
First we need to understand the nature of the residues. Are they a product of process control, equipment performance, board prep/cleanliness? The equipment vendor or application engineer will be able to assist you better with this issue.
Senior Manufacturing Engineer
If you are doing the plating correctly, you will be using a number of different chemicals to prep the location. a solution for Stripping the solder down to the copper, nickle plating solution, gold plating solution. Poor cleaning between each operation can leave residues behind. it will also affect porosity of the gold, possibly causing failures down the road.Alan Woodford, NeoTech
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