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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

PCB oxidation

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PCB oxidation | 8 June, 2011

Hello, I am having a problem with HASL PCB's after it comes back from the stuffer. To me it looks like oxidation and it causes poor wetting. This leads to a bunch of problems all of which have different symptoms but the cause is this oxidation problem.

I spent considerable effort in trying to find the cause and I have eliminated the PCBA stuffer as the cause. I suspect this is a PCB vendor issue. I asked around my building and someone commented that it could be the quality of the copper trace. I'm thinking it might be the quality of the solder used in the HASL process.... but I do not know.

What do you guys think? I'm about to contact the PCB maker but I am oblivious as to what they may be doing wrong. Note that this problem is a recent problem. We never had this problem before. The PCBA stuffer did not change their process and we tested older boards from the PCB maker and it doesnt have this problem, only the latest boards from them do this....


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PCB oxidation | 9 June, 2011

Does the board look like that before Reflow?

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PCB oxidation | 16 June, 2011

The finish looks like Immersion Tin or Silver.

if its lead free Hot air - could be issue of to high of a Tin Content. find out what brand of Hasl they are using. SL100 Example.

Is this tarnished look only being seen after assembly or have you seen it before assembly to.

I would send the pictures to you board house and see what ideas they have.

If nothing else have them send you some samples of this board with an alternet finish and see if you have the same issues. I would recommend Enig.

Looks to me like a Tin issue.



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PCB oxidation | 17 June, 2011

Your problem is at your board house with the finish. There is not enough tin deposited on the ground plane. Could be the current density too low on the ground plane. If electroless they just didn't process these correctly.

What is the finish supposed to be?

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