Well, I also read in the paper that they are not advocating removing date
codes from parts.  That is good, because from my standpoint, they are
indispensable.  Component suppliers can and do periodically change
processes, generally for the better.  Sometimes they change the part
designation by changing the suffix letter on the part, as is common with
memory chips, but more often the part number does not change.  Why?
Because only the largest identifiable customers are notified and everyone
else would continue to order by the old designation and create great
confusion for the distributors.  My point is that many, if not most, process
changes occur without changing the part number in any way.

From my viewpoint as a designer, the solderability issue is the smallest
utility of the date code (I'm not minimizing the solderability issue, just
that there are even more critical issues for ordering by date code).  We
still need the ability to specify parts with stipulations like "no date code
before Sept. 14, 2000" to avoid known die and process changes that make a
part incompatible with a design.  This is particularly important with
recently designed parts, some of which have published errata.  If we
designers had to take it upon ourselves to make a design tolerant of every
die revision of even the major semiconductors on a board, all designs would
be more expensive and some would have to be scrapped entirely since features
that the design depends on may not work on an early die revision.

The manufacturer may say the new part "should" be a drop-in replacement, but
will they guarantee it?  Of course they won't, because it is application
dependent.  As long as that is the case, we need the ability to order by
date code.  I think it should be noted that doing this is not a normal
practice, at least for me, but is only done where there is good reason to
believe there is a problem.  I'm sorry the distributors don't like this and
I appreciate their difficulty in making money on their undeniably thin
margins.  However, continuing their gradual movement toward the paradigm of
"parts is parts" just won't cut it in this industry.  Though I feel their
pain, they need to find another way to improve margins.

Regards,

Seth Goodman
Goodman Associates, LLC
tel 608.833.9933
fax 608.833.9966

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