Kathie
In my last life, I made ionic contamination testers with built-in SPC. This was much
appreciated by our clients. We developed the software specifically for the application.
We did a curve fit on the conductivity/time curve and extrapolated the curve to
infinite time and used the curve parameters for the statistical analyses. The important
point is that each board type must have its individual file so that you are always
comparing apples with apples. As you say, with a running average technique, you can
pick up trends which may indicate a process going out of limits before it happens. This
kind of tester is still available, from a third party, now, but it has unfortunately
lost some of the sophistication I put into the software in the transition from DOS to
Windows, which they thought was an advantage: prettiness over technology???.
Brian
"Lambert, Katherine A." wrote:
> Hi folks,
>
> I'm investigating the feasibility of implementing SPC on cleaning operations
> and was wondering what the rest of you are doing, if anything.
>
> What types of SPC activities, if any, are you doing on your cleaning
> operations? Have any of you tried SPC on cleaning operations? If so, what
> kind of results did you have? Did you find it worth while?
>
> What measurements would be useful for monitoring process drift so that you
> can correct the process before it starts producing less than clean boards?
>
> For SPC activities, we've kicked around the possibility of monitoring board
> cleanliness at the end of the cleaning operation, measuring solvent/fluid
> quality, monitoring various machine parameters.
>
> We have two major pieces of cleaning equipment used to clean RMA flux from
> CCAs - a co-solvent vapor degreaser, and a semi-aqueous in-line cleaner. We
> currently do a cleanliness test (Omegameter or Ionograph) on each lot of
> boards. We also record various gage readings on the in-line cleaner on a
> daily basis.
>
> Thanks for any light you can shed on this issue.
>
> Kathie Lambert
> Process Engineer
> Northrop Grumman
> Baltimore, MD
> 410-765-9746
>
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