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From:
"ddhillma" <[log in to unmask]>
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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