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March 1998

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Subject:
From:
Ted Stern <[log in to unmask]>
Reply To:
Date:
Wed, 4 Mar 1998 08:19:44 -0800
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Dear Mr. Patel:

Could you provide additional detail regarding the nature of the problem?
Evaluating SEM/EDX data is tricky, but based upon the information you
provided, possible sources for the elements identified would be:

1) Si - residue from a pumice scrub or silicon based anti-foam;
2) S - potentially from a HAL flux or copper pre-clean product prior to
        HAL;
3) O and C - these elements are present in LPI, in HAL fluids (both
        in the polyol and organic acids), and in the epoxy laminate;
        hence difficult without quantitative data to speculate on
        a source;
4) Ca - most probably from city or "tap" water used for rinsing (hard
        water scale is likely calcium carbonate (CaCO3), which
        would also be a source for carbon and oxygen);
5) Cl - again would be present in city water, but could also be present
        in hydrochloric acid activated HAL fluxs; and
6) Ba - ?????

Good luck!

Regards,
Ted Stern


Ken Patel wrote:
>
> Dear Technetters,
>
> I need all possible help to understand SEM analysis done on my board and to
> find out possible sources of basic elements.
>
> (1) On solder mask area, there was Silicon (Si), Sulfur (S) - is it due to
> LPI solder mask? Also found Oxygen (O) and Carbon (C)- meaning flux residue?
>
> (2) Found Silicon (Si), Chlorine (Cl), Calcium (Ca), Barium (Ba), Oxygen (O)
> and Carbon (C) on epoxy and in a kind of void area- is it from flux?
>
> Is there any book that help me solve above mystery?
>
> re,
> ken patel
>
> ______________________________________________________
> Ken Patel                       Phone:  (408) 490-6804
> 1708 McCarthy Blvd.             Fax:    (408) 490-6859
> Milpitas, CA 95035              Beeper: (888) 769-1808
>

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