In a message dated 02/24/2000 11:34:11 AM US Eastern Standard Time,
[log in to unmask] writes:

> Doug
>
>  I thought that one would get you to rise to the bait :-) Am surprised
Graham
>  hasn't reacted, either.

Brian, don't visit Indiana.  Hoosier-baiting is punishable here.  And Graham
has more restraint than I do.

>
>  Seriously, I consider this an important problem as very few assemblers
test the
>  bare boards they receive, let alone the components. I consider that there
are
>  also many other ignored parameters, some of which I brought up during
various
>  IPC and ISO WG meetings, to be shot down - for the most part - in flames.

Yup.  Manufacturing quality hardware is not a simple proposition.  Lots of
things to consider.

>
>  Unfortunately, I do not have an answer to all these problems. I'm a great
one
>  for actually putting the test patterns on the real PCBs, as close to
critical
>  components as possible, but even that is less-than-ideal :-(

That would be nice, but with the increased drive towards miniaturization, the
real estate on a PWA is too valuable for SIR test patterns.  A better
approach, I think, is to have test boards which mimic the hardware to be
examined, but are designed for evaluation testing.  I designed such a board,
which I call the Umpire (note the evil spam masquerading as a technical
answer here), when many of my clients had problems with the currently
available process qualification vehicles.

>
>  If the truth be told, I honestly believe that we should forget all we have
 in
>  the way of ECMR and SIR standards and start again with a totally clean
slate,
>  beginning with the basic definitions which have become so distorted as to
be
>  misleading. There are FAR too many legacies from test methods and
standards
> that date from 30, 40 or more years. Not only did we not have an
understanding of
>  what it was all about, then, we didn't have sufficiently good instruments
> and  even most of those available today leave a lot to be desired. I have
never
> seen  an in-depth scientific analysis of all the mechanisms that can
influence the
>  results.

Oh, no arguments here, but I would favor more figuring out what our history
teaches us, rather than throw the baby out with the bathwater, as it were.

>  From time-to-time, I've brought up some practical observations,  over
>  the past 20 years, some of which have created discussion and others,
> yourself likewise, have done the same. Furthermore, we need to address
present issues,
> let alone future ones. Who, e.g., has done anything about SIR on HDISs with
>  track spacings down to 25 um?

Oh, there are companies who are looking at such things, but they keep their
cards very close to their chest.  I'm sure you can see why.

>
>  Advocatus diaboli sum (and probably in dome canis est, by your lights!).
>

Gosh, what I'd give for your education level.............

Doug

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