Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Black pad defect on gold plated boards

#25534

Black pad defect on gold plated boards | 21 August, 2003

I have some finished boards that I have concluded have "black pad" defect. Outside of the black crap on some of the solder joints, if the boards are electrically functional, are they reliable? Any opinions would be appreciated as I dont want to throw out 20 grand.

reply »

Justin Medernach

#25549

Black pad defect on gold plated boards | 21 August, 2003

Do some push / pull testing. Typically with black pad, you can flick the components right off the board. If you have this, the boards are about as reliable as a Yugo. If you get decent push / pull results, odds are you don't have black pad and you don't have much to worry about. Usually, you don't find black pad through visual inspection, you find it because a Tantalum cap, or any other higher profile device just kind of "popped right off the board."

Regards, Justin

reply »

#25552

Black pad defect on gold plated boards | 21 August, 2003

You have one option: Take the boards to the fabricator that build the board and ask him for $20k.

reply »

#25559

Black pad defect on gold plated boards | 21 August, 2003

Well, for some reason the board house will pay for the boards but has some issue with paying for the parts on them. Why am I not supprised?

Perhaps I have mis-diagnosed the problem. We have found two different board p/n's with the same type of defect. Both from the same supplier. One production lot (processed at the same time) had two date codes, only on date code displayed the probelm and it was on every board with that date. If black pad is caused by oxidation of the nickel before the gold plating, it would seem the severity would be dependent on the severity of the oxidation. Our supplier outsources the gold plating so It would seem pretty possible the boards sat around awhile before gold plating. The defect looks like black goo mixed into the joints and once removed the pads do not take solder well if at all. I can not flick parts off the board though. The first time it occured we thought it must have been contaminated some how in our facility. We cleaned up the joints as best we could and shipped it since it was just a prototype. Electrically, the boards worked fine but the engineer removed an so-8 to try another part and the pads would not accept solder. I can not imagine that this is not some kind of plating probelm. We sent some of the first batch back to the supplier and they claimed it was surface contamination and that the plating was fine. We use boards from a number of houses with this type of plating and I have never had a problem in the 4 to 5 years we have used it. Also the problem batches of boards were run 2 to 3 weeks from each other, not at the same time.

Any help deeply appreciated.

reply »

#25560

Black pad defect on gold plated boards | 21 August, 2003

Well after reading all kinds of stuff about this I still question if it is my current problem BUT, how common is this??? I dont want to be afraid of the boogie man but it seems like a lot of folks are having problems with black pad. I have used imersion gold for years with not one single issue until now. Is imersion silver a better choice? I am no metalurgist but I have gold and silver stuff in my house, the gold is gold and the silver has turned black. Is imersion gold something everyone is staying away from and I have just been lucky so far?

reply »

#25567

Black pad defect on gold plated boards | 22 August, 2003

Ask your supplier for a corrective active and failure analysis of the boards. In parallel, send the boards to a failure analysis laboratory to determine the material on your gold pads.

Take your work to another supplier.

reply »

Boundary Scan

PCB Assembly Equipment Auctions