David,
I would be interested in seeing a copy of the paper you refer to in your
reply. Would you be kind enough to e-mail a copy to me?
Peter Barton
Senior Process Engineer
ACW Technology Limited
Dinas Isaf West
Tonypandy
Mid Glamorgan
CF40 1XX
E-mail [log in to unmask]
===== Original Message from [log in to unmask] (TechNet E-Mail Forum.) at
21/06/02 03:10
>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.
-----------------------------------------------------------------------
Peter Barton
Senior Process Engineer
ACW Technology Ltd
Dinas Isaf West
Tonypandy
Mid Glamorgan. CF40 1XX Wales
Tel: 01443 425200 Fax: 01443 436882
International Tel : +44 1443 425200 Fax : +44 1443 436882
E-mail: [log in to unmask] Website/URL: www.acw.co.uk
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