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April 2008

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Wed, 16 Apr 2008 12:59:44 EDT
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As perhaps the only person still around that attended the meetings  resulting 
in the equivalence factors and IPC Cleaning & Contamination Chair  at that 
time, perhaps a few points would facilitate the discussion:
 
1. The Navy set up the ionic testing development program to solve a serious  
failure problem in S.E. Asia. 
It worked.
 
2. In the timeframe when the test was developed and put in place by the  
military, most of the rest of the electronics industry in the US used the mil  
specs since they were free.
 
3. As the IPC set up and adopted Classes 1-3 (basically toys up to  
military/high rel), I asked the committee if we used the mil test result for  Class 3, 
could we use 1.5x that limit for Class 2 and 2-3x for Class 1? 
The response was that with proper cleaning, the mil limit could readily be  
achieved while serving to monitor daily production. So the industry continued 
to  use the (free) mil spec test standard.
 
4. The ionic contamination test was a valuable monitoring tool, since  the 
SIR tests were done on coupons, not on actual assemblies, and took 1-2 weeks  to 
complete. Needless to say, a high volume electronics producer could turn out  
a significant volume of PWAs during that time, often shipping them into the  
field as soon as assembly was completed.
 
5. As noted in my SMT column (offered yesterday) T. O.  Duyck of Northern 
Telecom was charged with implementing water soluble flux for  NT electronics 
production. During that time he observed and reported the  differences in flux 
residue release rates, pointing out that rosin ca 90% of  rosin flux residues 
release from the PWA surface during the 10-15 test time for  ionic test 
equipment, while water soluble flux residues may take up to 2 hrs. to  achieve the same 
level of release. Thus the release rate should be checked to  ensure the flux 
used, time test time and the instrument employed provide  reliable results 
and guidance to the production engineer. 
 
6. In the late 1980's, the materials and acceptance of the no clean or low  
residue or acceptable dirt concept became widely accepted and implemented on 
the  designs of the time. Outsourcing to contract assemblers (both in the US and 
 overseas) became widely practiced, so much of the former 'in-house' cleaning 
 expertise disappeared. 
 
7. This was seen at IPC as the number of company sponsored volunteers  
dwindled. Could we take on projects today to develop an updated ionic test for  pr
ocess monitoring? Find enough participants to conduct statistically sound  round 
robin testing?  

Bill  Kenyon
Global Centre Consulting
3336 Birmingham Drive
Fort Collins, CO  80526
Tel: 970.207.9586   Cell:  970.980.6373




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