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Date: | Wed, 08 May 96 08:32:18 cst |
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Ivo -
We are just completing a low residue flux implementation program and
eliminating all rosin fluxes from our manufacturing process. We are a
military/commercial OEM but convincing our customers wasn't easy.
Quite a bit of test effort went into the selection of a low residue
flux that is "cleanable" and "as good as" our former RMA flux. We will
be removing our flux for a period of time then work with our customers
on the next step - implementation of a no clean process. When you talk
to your flux manufacturers you need to point out that you want a
"washable" low residue flux - don't just request a water soluble.
There still seems to be a terminology problem - many people use water
soluble and water removable flux as equivalents. They are not! Many of
the low residue fluxes are modified rosins and not the water soluble
type fluxes that you are familiar with. Throughout our conversion
program I have run into another terminology issue: low residue and no
clean. Low residue is a material characteristic of a flux, no clean is
a manufacturing process choice - these two terms get used
interchangeably also. I would contact Doug Pauls at Contaminated
Studies Labs 317-457-8095 or [log in to unmask] on what typical tests are
being used for rosin-to-low residue flux conversion programs. Good
luck.
Dave Hillman
Rockwell Collins
[log in to unmask]
______________________________ Reply Separator _________________________________
Subject: ASSY non-rosin flux and MIL
Author: [log in to unmask] at ccmgw1
Date: 5/8/96 4:31 AM
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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