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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