Steve,
Thanks for the input to the standard.
This was a very hotly contested issue with the last revision to the standard
(610C).  In synopsis, concern for PTH reliability was in regard to thermal
shock conditions based upon some old documentation that I'm sure you are
aware of, and input from companies that had experienced failures. The
advancement of standards and allowances for PTH robustness may serve to
cause new concerns and personally I've seen renewed issues concerning PTH
reliability as a performance limitation. It would be useful to run some new
tests using newer PWB technologies and see what the outcome and impact is
today.
I echo your concern for rework of PTH solder connections and even worse vias
that have solder fill. Remember that the consideration to rework is a last
resort and a drastic measure and certainly only one of the options available
for consideration according to the IPC standards.  We should not arbitrarily
rework product without consideration for outcome based upon reliability and
product performance. Other options are available under Disposition.


Mel Parrish
Director of Training
Soldering Technology International
102 Tribble Drive
Madison, AL 35758
256 705 5530
256 705 5538 Fax
[log in to unmask]
www.solderingtech.com

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Sauer, Steven T.
Sent: Monday, May 13, 2002 7:33 AM
To: [log in to unmask]
Subject: Re: [TN] ReA610HoleFill


Jim, Guy, Nancy and others,
I respectfully submit the following:
If the intent for the 50% hole fill allowance (in regard to PTHs with
thermal or conductor planes) is to be limited to class 2 then the exception
should be listed directly under "Acceptable - Class 2" not under "Defect -
Class 3" on page 6-7 and table 6-2 should have a note that flags this
allowance for Class 2.
As we all know, it is impossible to clearly and concisely write with the
English language in such a manner that all readers will properly understand
the meaning or intent of the words that is or are being conveyed.
Having not participated in the IPC-A-610 meetings (as Guy  referred to), I
and others do not have the luxury of understand the intent of certain
requirements -- all that is affored to us is the written words.
In this case, the intent may have been to limit the 50% hole fill
requirement to class 2 but the printed words do not support this beyond the
shadow of a doubt.
I will prepare a Standard Improvement Form for IPC-A-610C and forward to IPC
so the committee can fill more hours with antiquated prose about this
subject.
I on the other hand still believe that 50% hole fill on most class 3
products will not cause a problem in terms of long term reliability even
under extreme conditions as apposed to reworking the solder connection.
This statement is made under the premise that a well defined, developed and
controlled process is utilized.
If there is any objective evidence that 50% hole fill is a problem, I along
with Sir Werner would like to review the data, hardware, photomicrographs,
cross-sections, etc.

Steve Sauer

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