Bogert, family name or what? You didn't sign your mail, nor did tell what you are.
Anyway, as David said it's seemingly a nasty area. I think personally that cleaning or not must be preceeded by a discussion about application. Many so called MIL toys live a boring life in an office somewhere, never see sea and salt, never hear the sound of pinging dust particles, no thunder, no sauna, no vibrations, no violent hands from field repair etc. Just same temperature, same humidity and same boring humming form cooler fan in a sleepy military office. Why should such boards be cleaned?
And you have those boards living quite an opposite life, e.g. in a rotating radar crossing the seas year round, or bumping on a gun, forgotten in a rotten, humid storage room and similar reality conditions. We would never deliver boards for that later use without cleaning! Especially not when you expect the boards to do their job at any time for one, two or three decades!
Regards
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: Bogert [mailto:[log in to unmask]]
Sent: den 21 juni 2002 01:18
To: [log in to unmask]
Subject: [TN] Cleaning of Military PWAs That Have Been Soldered with No-Clean Flux
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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