ENIG Plating - What happened here? Errornious finishing; What do experts say?

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Syn

Well-known member
Joined
Jun 7, 2018
Messages
56
I came across a lot of errorneous platings on ENIG processed boards, however, i have no idea what exactly went wrong and if i can expect more yield from some of the errors given. Here is a picture i uploaded before:
404.jpg

I will make more pictures on different errors, soon.

Can someone explain what went wrong in the plating process so i can understand what errors would (most likely) give better results for gold yield?

Thanks
 
I am sorry for the picture quality, i will try to improve it, especially the colors are far of from reality for some of the details.
 
To be frank, on some of the pieces it looks more like the base material has corroded because of external factors giving that look, rather than the plating being wrong.

On a couple of them it's dubious but there are cases of much older pieces of equipment having the gold hand applied rather than machine applied which leads to inaccuracies in the thickness. It's not something that's particularly common these days.
 
ENIG is self-regulating, it shuts down when the surface is thick enough to be solid. To get a thick gold flash should be really rare but putting a gold flash over an irregular surface is no problem, it's still thin though.

It looks more like the gold has plated on something left at the edge of the board, tape residues for example.

Göran
 
@anachronism
Yes it may be, but can you tell which pieces you mean?
These i have in mind also have the plating but look much browner, i believe this is due the very big surface; this would also imply a bigger area for the gold to settle.

@g_axelsson
I have read about the self regulating process, but what happens when the surface is different from the Ni layer, Cu or CuNi alloy for example?
 
I don't know what would happen, but the immersion gold would cement on any base metal surface until it is covered. My guess is that there are levelling chemicals added to create a smooth surface that would create a similar smooth surface on other base metals than nickel.

Göran
 
The three on the center left;
I have found parts with same design edges but normal gold plating in the middle of the board and figured by colour, they also resemble heated up traces, so it could be formed during machining instead of an plating error or maybe oxidation due to swashing (stacking layers?) :?: :!:
 
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