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Date: | Wed, 08 May 96 10:59:42 +0100 |
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Thinking obout the environment and all, a solder paste that can be cleaned
after reflow using (DEMI)water is a beautiful thing. However, when i'm
thinking about using it, questions bubble up...
Water-washable fluxes in solder pastes are always? non-rosin (for example
organic acids). Because my fab produces many militairy PB's, this is
unaccceptable. Only R and RMA are conform the the good old MIL-STD-2000.
(Or you may only solder sealed devices etc. and still meet some conditions)
OK, flux activity of these paste are higher, but the modern OA flux-types are
comparable with RMA?
An other problem is that "Flux residue or foreign material" is a defect
(acc. to the 2000). Cleaning SMT, even with low residue/no clean flux becomes
very difficult that way. Especially when i consider that ionic contamination
test equipment for THT is not adequate for SMT. And when coating the PB's,
the less residue the better. Mixed THT/SMT products are also food for
thought.
Can someone help me see the light? Any statement, suggestion or experiences
using "aqua" pastes and cleaning/coating them after reflow FOR MILITAIRY USE
are welcome! (MIL-STD-2000 is still our guideline)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ivo de Rooij Process Engineer SMT/THT
Fokker Elmo BV (Fokker Aviation) [log in to unmask]
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