Doug
I thought that one would get you to rise to the bait :-) Am surprised Graham
hasn't reacted, either.
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.
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 :-(
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. 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?
Advocatus diaboli sum (and probably in dome canis est, by your lights!).
Best regards
Brian
[log in to unmask] wrote:
> In a message dated 02/23/2000 3:09:10 AM US Eastern Standard Time,
> [log in to unmask] writes:
>
> >
> > This is the main reason why SIR testing is, in many cases, useless to
> > qualify a flux: you qualify it under lab conditions, totally ignoring
> > the fact that its behavious will alter in practice due to it mixing with
> > external contaminants not present on your test vehicles.
> >
>
> SIR USELESS? Gasp!! Burn the Heretic!!!!!!!!!!
>
> SIR can be useful, even as a lab tool, you just have to use the right
> combination of materials, processes, environment and data interpretation. I
> would agree that we have a long way to go before our existing methods are a
> good and true measure of field performance.
>
> Doug Pauls
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################
|
