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PCB finish

Views: 4038

#87518

PCB finish | 19 January, 2022

Looking for opinions on pic attached of ENIG finish. appears to be over-etched gold, but I am not trained up on PCB fabrication.

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#87521

PCB finish | 20 January, 2022

For me it seems that the board is already assembled & soldered. Before assembling the board had been (poorly) washed (misprint perhaps) and the spots are just melted solder paste. Aren't those solder balls in the grooves between the pads and solder mask?

I might be wrong as the board must be very poorly washed then.

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#87522

PCB finish | 20 January, 2022

Copper gets etched in a photographic manner. ENIG is an additive process. Nickel gets added then gold gets added on top. Therefore it is not a matter of over etching. It is a matter of not enough gold added. The layer of gold ideally is as thin as possible with 100% coverage. And gold gets contaminated easily.

People generally run boards with gold fingers without taping the fingers no more than one time. And gold fingers are a lot thicker.

I think Stivais is right. If you look at the middle pad on the right it looks like solder that had its flux washed out.

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#87523

PCB finish | 20 January, 2022

I agree it looks like that, but no solder has been on this area. We are asking the board house to get their input.

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#87524

PCB finish | 21 January, 2022

"Manual washing" of a misprint board basically is smearing of printed solder paste all over the board. And trying to remove (wipe off) it afterwards. So for me it would not be any surprise that the solder paste ended up on the pads where it was not initially printed.

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#87525

PCB finish | 21 January, 2022

Like I said a lot of people don't tape the gold fingers the first time they run them. After that they make sure the fingers get taped up because solder gets places you don't think it does and once it touches gold, that gold is contaminated.

How do you explain the little bit of solder on the middle pad to the right?

No solder was in that area intentionally. That does not mean that there was never solder in that area.

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#87531

PCB finish | 24 January, 2022

Hi, Mainly concentrate on 2 subjects: 1- Cleaning of Misprinted PCB (always use best neutraliser to remove paste from PCB), 2- Underneath Stencil Cleaning - Use good stencil cleaner (rather than IPA) to wipe your stencil. Because both the above said process having equal contribution to create such defect.

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jseewald

#87546

PCB finish | 28 January, 2022

That is correct. This looks like a board that was printed then wiped but not washed. Solder spheres left out on an unsolderable surface will just sit there like this or coalesce into solder balls. Nothing in the picture indicates an issue with the plating.

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