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February 2000

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Subject:
From:
"Carano,Michael" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 11 Feb 2000 11:12:46 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (86 lines)
Stephen,

Is it possible that the mask is over cured? Maybe somewhat embrittled? The
problem seems like more of an adhesion problem as you suggested. If the mask
in undercured, a thermal bump should give the mask some additional
crosslinking.
If the mask is a two part system, the shop may have had some component
mixing problems or the mask pot life was nearing its end.

Good luck,

Mike Carano

        -----Original Message-----
        From:   Stephen R. Gregory [SMTP:[log in to unmask]]
        Sent:   Friday, February 11, 2000 8:12 AM
        To:     [log in to unmask]
        Subject:        [TN] Solder mask failing tape test..

        Mornin' all!!

        This morning I got a email from one of our buyers telling me that
one of the
        boards at one of our fab shops is being held-up because it doesn't
pass their
        solder mask tape test. My buyer said that they told him that the
mask is only
        coming off the via's, and it was because of uncured mask. The mask
is a LPI
        and the via's aren't meant to be tented. Also the board doesn't go
through
        wave solder as the only through-hole is hand soldered because it
goes up
        through the board from the bottomside.

        My buyer is asking me if we should accept the boards. I have a few
concerns.
        One thing is that if there is uncured mask at the via's, what
guarantees are
        there that there isn't more at other places on the board? Shouldn't
uncured
        mask be a simple thing to fix by either baking the PCB (if it's a
thermal
        cure), or exposing it to more UV (if it's a UV cure)?

        Further still, does uncured mask come off in a tape test? Or is mask
coming
        off from a tape test more an indication of an adhesion problem from
        contamination?

        Thanks in advance for all replies,

        -Steve Gregory-

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