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April 2000

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Subject:
From:
"Wang, William (Suzhou Laminate)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 6 Apr 2000 11:31:00 -0700
Content-Type:
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     I work for a copper clad laminate manufacturer. One of our customer
(PCB shop) has wicking problem for plated through hole. They said they found
"laminate void in glass fabric " by microsection. (They mean the glass yarns
are not wetted by epoxy resin, not void in resin after lamination. Usually
wicking is related to rough drill or over desmear process). I made
microsection by myself and make real good polish. After that I believe the
so called "laminate void in glass fabric" is the result of poor polishing
i.e. scratches. (My microsection can see a single yarn but their
microsection can't). I attached some detail dimension for your reference:
    Glass yarns diameter: 1080 (5 microns), 7628 (9 microns)
    Extect abrasive paper P1200 grit: grit size 10 to 20 microns, average 15
microns
    Multipolish Al2O3: 0.05 microns
    Specification for laminate void is < 3 mil. (IPC-4101 & MIL-PRF-5510 F).
Our product is 5 mil laminate so the "laminate void will be far less than 3
mil.)
    My customer show us a article dated at August 1982 by PC FAB, "Laminate
Porosity Causes". But the pictures are too blur after copy many times. The
authors are J.F. Nejedlik and A.M. DeSantis.
    My questions are as follows:
    1. Anyone has the experience of "wicking" or "blow hole" due to the
wetting problem of glass fabric?
    2. Is microsection technic with 100 X to 200 X magnification capable of
tell the wetting condition of single yarn of glass fabric?
    Any inputs will be greatly appreciated!!!

    William Wang

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