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August 2001

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Subject:
From:
"Marsico, James" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 15 Aug 2001 06:52:39 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (106 lines)
The process is standard SMT with convection reflow using water soluble flux
and a very aggressive in-line aqueous cleaner.  The solder balls seem to be
stuck under the chip components.  They are very difficult to see,  you have
to actually tilt the board sideways and look under the components.

Jim Marsico
Senior Engineer
Production Engineering
EDO Electronics Systems Group
[log in to unmask] <mailto:[log in to unmask]>
631-595-5879



        -----Original Message-----
        From:   Lush, Dorothy [SMTP:[log in to unmask]]
<mailto:[SMTP:[log in to unmask]]>
        Sent:   Tuesday, August 14, 2001 5:06 PM
        To:     'TechNet E-Mail Forum.'; 'Marsico, James'
        Subject:        RE: solder balls

        I like Loan's answer because solderballs normally form in the middle
along
        the side of the chip component and not underneath. The normal
solderball is
        formed when solder follows the flux under the component during
reflow then
        is "squeezed" out to the side when the molten solder solidifies,
shrinks and
        pulls the chip flush to the board surface. I could see the pulling
down
        action stopped by, say, epoxy or soldermask non-existence or over
presence.
        Are these balls being formed during SMD or solderwave do you think?
An
        aqueous SMT paste process usually will wash this ball away. No-clean
paste
        requires not forming them in the first place (and only allowing them
to stay
        if they are imbedded in flux and less than a certain size, etc.) by
        controlling stencil aperature, solder printing(x-y and z(volume)),
solder
        choice and oven profile. Is this an aqueous or no-clean solder
paste/process
        we are talking about?

        Dorothy Lush
        Manufacturing Engineer

        > ----------
        > From:         Marsico, James[SMTP:[log in to unmask]]
<mailto:[SMTP:[log in to unmask]]>
        > Reply To:     TechNet E-Mail Forum.;Marsico, James
        > Sent:         Tuesday, August 14, 2001 12:34 PM
        > To:   [log in to unmask] <mailto:[log in to unmask]>
        > Subject:      soldr balls
        >
        > Here's a relatively basic SMT question, but we've haven't
experienced this
        > before.  We're seeing solder balls under (way under, in the
center) chip
        > components.  Any recommendations?
        >
        > Jim Marsico
        > Senior Engineer
        > Production Engineering
        > EDO Electronics Systems Group
        > [log in to unmask] <mailto:[log in to unmask]>
<mailto:[log in to unmask] <mailto:[log in to unmask]> >
        > 631-595-5879
        >
        >
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