Was soldermask on the board when it was run through electroless 
Nickel/Immersion Gold?  

If so, is the soldermask proven to be compatible with the electroless 
Nickel bath?

If not, there was probably a lot of soldermask curing going on after 
plating which will oxidize nickel through the porous immersion gold.  
Thicker gold and/or an acid cleaner (to remove Nickel oxides) after the 
curing will help. 


Steve Sparkowich
Plating Engr.
[log in to unmask]





VIC BELDAVS <[log in to unmask]> Wrote:
| 
| I sent this message earlier. At the same time, lost contact 
| with Tech  Net.
| I'm not sure if this message got through. If it did, I 
| apologize for the
| duplication.
| 
| We purchase some pc boards with immersion gold over nickel to 
| obtain
| flat pads for better stenciling of solder paste. Our spec is 
| 5-8
| microinches of immersion gold over 150-200 microinches of 
| electroless
| nickel. We have generally been successful. The indications 
| are that
| about one year ago when this was first implemented, the gold 
| plating
| was coming in per the spec.
| 
| At this point, however, we are seeing the gold thickness to 
| be more in
| the range of 2-4 microinches. We are still doing OK except 
| for one batch
| of boards that came in recently. There are solderability 
| problems with
| these boards. This batch is also associated with a solder 
| mask change.
| But we also have other immersion gold boards with the same 
| solder
| mask change and no solderability problems.
| 
| Could it be that 2-4 microinches is at the ragged edge where 
| the gold is
| insufficiently robust to withstand further processing at the 
| fabricator and
| in assembly?
| 
| Does anyone else have similar experiences with immersion gold 
| in the
| 2-4 microinch range?
| 
| Is anyone consistently doing well with about 2-4 microinches 
| of gold?
| 
| Thanking you in advance.
| 
| Vic 
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