I'm trying to qualify a new cleaning process for electrical assemblies
prior
to conformal coating (Military boards). The old MIL Specs had as
cleanliness requirement of 2 meg-ohms minimum, is this all I need to do,
verify cleanliness to 2 meg-ohms? What about subjecting the assemblies to
10-day elevated temp/humidity (steady state)? Any recommendations?
*Jim, to your first question, Yes. When changing a cleaning operation, and
not changing fluxes, MIL-STD-2000A only required Appendix C testing, which
was the standard ROSE test. The 2 megohm-cm requirement translates to the
more familiar 10.06 micrograms sodium chloride equivalence per square inch,
whatever that becomes translated to the specific ionic cleanliness tester.
We all know what a crock that test is, but it still exists, especially in
military contracts.
Two questions you should be asking: What data does my customer need to
see? and I just trying to meet contractual requirements or REALLY show that
the change is not detrimental?
If the customer leaves it totally to you, then I suggest that you do both.
The ROSE test, bogus as it may be, is very easy to do and satisfies the
contractually focussed types. As to a longer temperature-humidity
exposure, that is a fairly good idea. What tests to you perform now to
tell you if product is good or bad? Do that same test but extend the test
time about 50% and run on hardware cleaned with the new method. At
Collins, our products go through -55 to 125C cycling to catch infant
mortality types of failures, er...ahhh... not that we EVER see such
failures, mind you....., and when we have a process change, we use the same
environmental screen.
Doug Pauls
Rockwell Collins
---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------
|
