Rudy, I don't know if telling what solder mask we use is a good idea, but it's well known to most equipment makers. Now, referring to BGA SMD questio by Horak this day, I would like to involve your answer in the BGA soldering issue.
Question: you say that it could be a tricky thing to get rid of ALL residues after developing, baking and the other steps following SMD. IF you don't get all remnants away, where will they be then? Baked into Nickel plating and the following HASL or Au or Pd or whatever you use? Can such interstitial contaminations cause fragile, superthin, hardly observable layers between ball solder and pad (Nickel)?

Ingemar Hernefjord
Ericsson Microwave Systems



-----Original Message-----
From: <Rudy Sedlak> [mailto:[log in to unmask]]
Sent: den 7 september 2000 00:05
To: [log in to unmask]
Subject: Re: [TN] HASL Dewetting...II, The Beast Lives


Steve:

Remember the process a PCB goes through prior to HASL....

Develop of soldermask
BAKE to set soldermask
Clean up of oxides caused by baking (usually microetch)
Flux
HASL

If you do not take ALL soldermask residue off during developing, that BAKE
puts it on almost permenantly.

And taking all the soldermask residue off during developing means turning the
solution over to keep mask contaminants in the developer solution low, and
GOOD rinsing.

Yeah, sure cleaners exist that will remove these residues after bake, but
properly done (and we all do things properly, at all times, don't we?) you
should not need it.

Rudy Sedlak
RD Chemical Company

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