Chris
I agree with Father Doug. How long is a piece of string? I can think of
cases where 1.5 ug/cm2 eq. NaCl (the more modern figure, roughly the
same as Doug's) is grossly insufficient and others where it is gross
overkill. Would you apply the same standards to a satellite, a submarine
repeater, a personal computer and a Gameboy?
At the best, ionic contamination testing is a yardstick to ensure your
process remains constant. If the results drift up or down, then you know
something is happening, which may have undesirable effects on the
reliability.
Also, ionic contamination is not the be all and end all of ensuring
reliability. I've seen many failures of electronics assemblies because
of non-ionic contamination. There is no easy way of measuring the
latter, or gauging its effect on reliability.
There is only one way of determining reliability: build some assemblies
and test them under real worst-case working conditions for the number of
years you need them to operate. When you have done this, you can
establish your manufacturing protocol. Of course, this is not practical,
so one tends to err on the safe side (over-engineering) and one tries to
do accelerated testing, which often bears little correlation to real
life. However, if one logs carefully all failed assemblies that come in
for repair and diagnoses the fault mechanism, it is often possible to
slowly improve the process, possibly even reducing costs.
Brian
Christophe CROCOMBETTE wrote:
>
> Hi folks,
>
> Does anyone know if a standard related to the cleaning of electronic boards and connectors has been issued by any standard organization (IPC, ...) ?
>
> If anyone has an internal procedure from his/her own company, I would be interested in getting some inputs
>
> Thanks
>
> Chris
>
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