Summary for rework pcbs with corrosion Discussion
The focus keyphrase, rework PCBs with corrosion, fits this thread about salvaging immersion silver boards that showed corrosion after wave soldering. YL Moon asked whether there is a rework method, a supplier who can perform it, and a test to verify reliability risk after rework. Mark Baker replied that because the boards had already been wave soldered, rework would be difficult. He suggested a cautious surface-cleaning approach: make a 10% fluoboric acid solution, use a medium-bristle brush to scrub the surface, then rinse in DI water and dry immediately, with gloves and eye protection. He specifically avoided recommending full immersion because the component mix was unknown. In a follow-up, YL Moon said excessive flux handling was likely a root cause and that he was gathering lower-risk methods before proceeding. The thread does not provide a supplier or a formal reliability test, only a limited cleaning suggestion and a warning about risk.
March 3, 2015
Q. Hi All, I have PCB boards detected with signs of corrosion. The boards are with Immersion Ag finishing and passed through wave soldering process. Do you know of any rework method that I can use to save those boards and any supplier who performs such rework?
Also, any test that helps to verify the reliability risk after the rework?
Thanks in advance for your time and feedback!
YL Moon
– Penang, Malaysia
March 8, 2015
A. Hello, because the boards have already been through wave soldering it will be difficult to rework them. You could try making up a 10% solution of fluoboric acid, use a medium bristle brush, dip the brush in solution and scrub the surface. Rinse in DI water and dry immediately. Wear gloves and eye protection. I don’t know what type of components that have been wave soldered, so I won’t suggest full immersion.
Mark Baker
Process Engineer – Phoenix, Arizona USA
 | March 10, 2015 Q. Hi Baker, many thanks for the suggestion. The corrosion signs were detected at different locations of the PCBA such as in the vias with mostly at BGA locations. It is known that sometimes corrosion might not happen instantly and it takes time to reveal the sign. Is there any treatment which can help to inhibit the pre-existing corrosion process to progress? Thanks… YL Moon A. Unless you know what the corrosion is, chemical dipping could cause even more problems.
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March 22, 2015
Q. Thanks Geoff.
Sorry for the delayed response as my gmail was down on last 2 weeks and thanks for the input.
i do have the similar concern for the chemical dipping as one of the key root cause of this issue is contributed by the excessive flux that was not properly handled during the process.
Thus, tried to gather as much as possible methods and will approach that with lowest risk.
YL Moon
– Penang, Malaysia