May I get an e-copy of the paper you refered to as well. I also work for a
military supplier, but we clean everything. I would like to get further
info on no-clean.
Gordon Davis
Application Engineer
Rockwell Collins
David Douthit <[log in to unmask]>@ipc.org> on 06/20/2002 09:10:13 PM
Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
to David Douthit <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
To: [log in to unmask]
cc:
Subject: Re: [TN] Cleaning of Military PWAs That Have Been Soldered
withNo-CleanFlux
You have landed in a very nasty area. You are correct to be concerned about
contamination issues.
Even if the residues from the flux do not create migration/leakage current
problems they may
collect other airborne contaminates that can cause problems.
Process, shipping, and storage control are critical to the reliability of
the circuitry.
If you wish I have a paper I presented in May of 2001 titled
"Avionics Systems, Reliability, and Harsh Environments"
that I could e-mail you. The information in the paper will
give you a good idea of what type of airborne contamination
issues you may have to deal with.
David A. Douthit
Manager
LoCan LLC
Bogert wrote: 6/20/2002 Folks is anyone manufacturing military PWAs using
no-clean flux and not cleaning the PWAs prior to shipment? If so, what is
your reliability experience with this process? We are considering a
military application (Class 2) where mixed technology (SMT and PTH) PWAs
will be soldered using no-clean flux and then not conformal coated
(assuming the uncoated PWAs can pass our temperature/humidity qualification
testing). Although the no-clean flux we will use should be benign (we are
having SIR testing performed to confirm this and Omegameter testing), I am
concerned that contamination may be introduced by other shop processes such
as mechanical assembly, testing, etc., even if one uses gloves or fingere
cots during handling. One could argue that after shipment, since the PWAs
are not conformal coated, you can introduce contamination in the field and
therefore, why not not clean prior to shipment. We may be performing board
testing (boundry scan, bed-of-nails, etc) on PWAs that have been soldered
using no-clean flux. I understand that certain noclean flux can impede
this testing, and also, may cause problems in event we need to conformal
coat the PWAs. Any comments on this subject will be appreciated.
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