Lou
Bad idea!
- Solder mask curing, in practice, is very variable.
- Flux removal, from board type to board type, is very variable
Good idea:
Do systematic tests on every board type and do your SPC on the results
of these, individually. On the instruments I used to make, we had a
separate file for each assembly and the SPC was automatic. Quite often,
we saw clients who had some board types trend up while simultaneously
other types trended down, even though the process was the same. This may
have been due to variations in bare boards, components, air quality or
possibly power voltage and, of course, human variations.
My advice is test all your board types, several times per day, if you
really want to do SPC.
Brian
Lou Hart wrote:
>
> 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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