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Subject:
From:
Gary Ferrari <[log in to unmask]>
Date:
Tue, 28 May 1996 10:11:39 -0400
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Nancy;

The best test method I have seen is the one that Bellcore uses. The first
step is to run a first piece sample in manual mode. You should have a real
time plot of the results. Once you have observed the curve flattening out,
you note time for the 90% level. You then use this time for testing the rest
of the lot. You will find, in most cases, that this time is much less than
the ten minutes you were using. However, larger boards may requrie longer
times than ten minutes. You should also note that you must repeat this
process for each product size that you test.

At 10:41 AM 5/23/96 CDT, Yuen, Mike wrote:
>
> ----------
>From: Diehl, Nancy
>To: Yuen, Mike
>Subject: Alphametals Ionograph 500 M Test
>Date: Thursday, May 23, 1996 10:30AM
>
>In the past we have operated the Ionograph tester in manual mode for 10 
>minutes with an accept/reject criteria of 20 ugNaCl/sq.in..  However, we 
>discovered that this is not the proper method, that in fact, it should be 
>operated in automatic mode.  The problem with automatic mode is many tests 
>run for 20 to 60 minutes before detecting a levelling off of contamination. 
> I have studied many test files and find a significant correlation between 
>the contamination measured at 10 min. vs. the final contamination.
>
>With a high degree of confidence, if the contamination level is less than 
>8.5 ugNaCl/sq.in. within the first 10 min. the raw PCB will meet the accept 
>criteria.  I would like the ability to run the equipment in auto mode, 
>observe the contamination level at the 10 min. mark, if less than 8.5 then 
>shut the test down, yet still retain the test record.  I am told this is not 
>possible.  Is there a solution to this?  Can the software be changed to 
>allow for retention of tests terminated prior to the equipment auto mode 
>shutdown?
>
>One recommendation I received was to run in manual mode for 10 min..  If the 
>contamination level is above 8.5, pull a second sample and run in auto mode. 
> This is an unacceptable alternative because 55% of the tests run in 
>automode shut off by 2 minutes.  In manual mode it would run the full 10 
>minutes and not shutdown prior if a levelling off was determined.  So on one 
>hand I am eliminating the long 20-60 minute auto mode tests, but on the 
>other hand running 55% of the tests 8 minutes longer than necessary.
>
>Anyone with answers or suggestions please contact me via e-mail at:
>[log in to unmask] or by phone at (414)751-3573.
>Thank you.
>Nancy Diehl.
>
>
Regards,

Gary Ferrari
Chairman IPC-D-275
Tech Circuits
(203)269-3311
[log in to unmask]



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