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September 2000

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Subject:
From:
Lou Hart <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 29 Sep 2000 14:50:45 -0400
Content-Type:
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text/plain (76 lines)
Kathie, I'm contending with the same problem now.  

When I was in bare board manufacturing, I made an individuals SPC chart based on one board tested from each lot that came through QA.  I saw Brian suggest separate charts or curves for each board type.  To be sure, this is the "correct" was to do it, but if you're working in a low volume environment, I'm afraid you'd never get enough credible data.  My chart included variation produced by different board types, but we did find it very useful.  I can tell you more off-line, if desired.

Since my earlier work, I've learned about Q-statistics.  Using Q-statistics allows SPC to be done on short runs, or to establish statistical control early in a process.  

If you (or anyone else) want to know my experiences using Statistical Process Adjustment to controlling saponifier concentration in an aqueous cleaning process, contact me off line.

Lou Hart
Compunetix
412-858-6184

----------
From:   Lambert, Katherine A.[SMTP:[log in to unmask]]
Sent:   Friday, September 29, 2000 11:38 AM
To:     [log in to unmask]
Subject:        [TN] SPC activities on Cleaning operations

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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