BTW... we've been using HF flux for well over 5 years and wouldn't think of
changing.

Jim Marsico
Senior Engineer
Production Engineering
EDO Electronics Systems Group
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        -----Original Message-----
        From:   Brian Ellis [SMTP:[log in to unmask]]
        Sent:   Friday, May 18, 2001 2:26 AM
        To:     [log in to unmask]
        Subject:        Re: [TN] Rework Wires and OA Flux

        Doug

        Citric acid is a funny one. It is tribasic (compared with dibasic
for
        most of the other usual N/C activators). Hughes are not the only one
to
        come unstuck with citric: Zeva had a citric acid/glycerol (a triol
or
        tribasic alcohol) W/S flux in the 1970s, long before Hughes. I
believe
        that the problem with citric is that it forms unstable chelates with
        some heavy metals (don't drink lemonades etc. from lead crystal or
        lead-containing pewter vessels!). The later formulations were, I
        believe, with maleic acid (found in green apples), which is dibasic.
Its
        ages since I heard anything about HF fluxes: I thought they had died
a
        natural death.

        I had a really bumper crop of lemons this winter, so my personal
citric
        to maleic ratio has increased enormously :-)

        Brian

        Douglas Pauls wrote:
        >
        > Very interesting, Jim. Do you happen to know who made the HF
series of
        > fluxes? I would like to get data sheets on them.
        >
        > The original HF1189 was based on citric acid (lemon juice) as the
        > activator.  The HF stood for Hughes Flux.  When it first came out,
it was
        > hailed as the greatest thing since sliced bread.  A classic case
of a
        > marketing department gone amuck.  The citric acid can be corrosive
and
        > there were some memorable military failures as a result.  Several
studies
        > were done on the 1189.
        >
        > I believe Kester picked up the 1189 family.  They reformulated the
        > activator away from citric acid toward more benign weak organic
acids and
        > called it HF1189A.  If I recall, the 1189A contains no citric
acid.
        >
        > I suggest you contact Kester for more information.
        >
        > Doug Pauls
        > Rockwell Collins
        >
        >
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