Suresh
IMHO, your problem is most likely related to the cleanliness of the bare boards and other components, assuming you
have chosen your "no-clean" products sensibly and after due qualification. There is no sure-fire way of detecting the
cause of the problem. A hygroscopic contaminant may be ionic or non-ionic. If the former, then the Omega Meter (or
other instrument) will detect it. If the latter, you can test for ever and still obtain no reliable indication. In reality, you will
possibly find that it is a mixture of both types and possibly a combination with the substrate and its finish. SIR testing or,
better still, ECMR testing will be OK for qualifying your process, but there is no production test available.
I recommend systematic testing by a well-qualified lab (in-house or consultant) who can identify where contaminants are
coming from, what they are and how they can be rendered harmless. Having done that, you will need to make sure that
the same problem cannot be repeated by developing a simple in-house testing procedure. If you do not have the
necessary resources, call in outside help.
Brian
2.7.01 02.56.03, Suresh Parmar <[log in to unmask]> wrote:
>Currently we have a PCA (Printed Circuit Assembly) which is sensitive to
>high humidity. Due to the sensitivity of the circuit we believe the failure
>mode is possibly related to the presence of contamination on the PCA.
>To measure the level of contamination on the PCA and to control the level
>of contamination to industrial standards, can anyone recommend the standard
>that should be referenced, the level of contamination that is common in
>industry and the method of testing.
>The PCA is a double sided SMT assembly using no clean solder paste and no
>clean solder wire for the few through hole components. For this type of
>assembly should I use the Omega Test or the SIR Test or any other test and
>what is the acceptable industrial levels.
>
>Regards
>
>Suresh Parmar
>Manufacturing Engineer
>
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