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Subject:	Re: Process control for cleaning
From:	Graham Collins <[log in to unmask]>
Reply To:	TechNet E-Mail Forum.
Date:	Mon, 30 Apr 2001 14:10:11 -0400
Content-Type:	text/plain
Parts/Attachments:	text/plain (42 lines)

Lou
First off - you are worried about what you build today, not a "standard" board.  Let's say you have your standard board, but then your pwb vendor does something unusual and ships you some boards with nasty chemicals on them - you won't test them so you will never notice.  If you run a no-clean process - very dangerous.

But more importantly, running the "standard" board through the assembly operation will degrade it over time - we have boards used repeatedly for thermal profile verification and they gradually deteriorate.  So your solder mask would change in characteristics, and thus your results can not be relied upon.

regards

Graham Collins
Process Engineer, Litton Systems Canada, Atlantic Facility
(902) 873-2000 ext 6215

>>> [log in to unmask] 04/30/01 02:35PM >>>
TechNetters, I'm following up on a discussion we had some months back,
regarding use of an Omegameter at the end of a cleaning operation for SPC.

Our production manager asked if we could use a single, standard board, run
it through the solder wave and cleaner, then test it in the omegameter,
doing this at prescribed time intervals for SPC.  Let me make sure I'm
clear:  this standard board would be one unit, that would be used
repeatedly to check the cleaning operation.  Using the single, standard
board would eliminate variablity from handling, board and material
composition, and all the things that affect the omegameter reading.  The
only variables (we speculate) would be in the solder wave and the cleaner,
the latter of which we are wanting to control.

What, if anything, is wrong with this idea?

My understanding is that incompletely cured laminate can release ionic
material.  Could there be any such problem with solder resist?

Lou Hart

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