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February 1997

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Wed, 12 Feb 1997 09:56:05 -0500
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     Doug and Phil,
     
     I agree with what you have both said. It is sometimes difficult or 
     impossible to get certain proprietary data or studies published for 
     the general populace. Also, every single point in a spec cannot be 
     experimentally characterized, nor should it be. However,
     the key requirements in a spec that are main effect variables on the 
     execution, implementation and assessment accuracy of the spec being 
     used should, be and I think are, based on data. It should not be 
     inferred by the technet readership that our industry spec's are 
     determined only by " who screams the loudest " or " who has the 
     fanciest reputation or credentials " at committee meetings. While 
     sometimes these two attributes do affect some of the text of our 
     spec's, I think  that the various committee's infact do settle 
     disputes about requirements with experimental findings if no data are 
     available and committee attendee's make reasonable arguments that 
     certain requirements are too extreme or too lax. Now Phil has also hit 
     another point right on the head. I think it is OK for someone to call 
     and ask for supporting data on a particular point. However, if someone
     thinks a particular requirement is incorrect or should be changed, 
     then THEY NEED TO DO THE PRELIMINARY WORK AT THEIR PLANT TO SHOW WHY
     AND THEN THEY NEED TO PRESENT IT AT THE NEXT COMMITTEE MEETING. It is 
     so easy to make coments and criticisms about spec requirements but not 
     so easy to show in an objective manner why. If it is such a big 
     problem, then there should be no issue getting travel approved to 
     " right the wrong ". For example, I know we had a disagreement 
     regarding steam age time and temperature requirement for solderability 
     testing during the drafting of ANSI J STD-002. This disagreement was 
     discussed at length and finally an experimental round robin test was 
     devised and both parties agreed, PRIOR TO THE RESULTS BEING KNOWN, to 
     " let the data speak ". Both agreed that if the results came out one 
     way, then the group would adopt one sides position. If the results 
     came out another way, then the other side would prevail. Granted, it 
     took a long time to finish the experiment, but it was finished and the 
     associated IPC reports were printed and are forever saved in the IPC 
     library. The speed with which such round robins are executed is up to 
     the testers and the committee's. Experiments can de devised to be 
     completed within six months if there is a will to do it and issue 
     being settled is a big issue.


     Best regards,

        Mark Kwoka
        Harris Semiconductor

______________________________ Reply Separator _________________________________
Subject: Re: ASSY: Reliability, IPC Specs, IPC Task Groups
Author:  [log in to unmask] at smtp
Date:    2/11/97 10:46 AM


Doug, 
     
Good explanation of the processes of spec changes.  Having been a task group 
chairman for many years and a member of many committees, I have found that 
published, non-proprietary, hard data is at best available around year 2050.
 If the task groups waited to make changes based on the full publioshed data,
the IPC specs would still be in the 60's while the suppliers and users were 
working to much later EU, IEEE, company specs and so forth.  The people that 
call and want a copy of the hard data often have never been to a meeting or 
have even submitted comments.  With a very few exceptions the IPC 
specifications have withstood the test of time and have become accepted 
standards  that many people can accept and will produce good reliable 
product.  The 5 to 15 people who are the workers on any spec. usually 
represent a good mix and do not intentionally sand-bag any particular group 
or company and are most often working to improve the industry standards.
     
Phil Hinton 
Hinton "PWB Engineering 
     
     
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