I am quite interested in this problem, too. We had two lots of clad laminate
which suffered from quite a bit of haloing after it was drilled, and I had
it tested for resin content and Tg by DSC. The results were OK. I suspect a
problem with the glass treatment (I don't know what else to suspect), but
don't know how to find out if this is the problem. The supplier is large
(and shall remain unnamed) and is taking their time to give an answer. Any
ideas?

Timothy Reeves
ECD Circuit Board Division
13626 South Freeman Road
Mulino, OR 97042
(503) 829-9108 (800) 228-8198  FAX (503) 829-5482


> ----------
> From:         Wang, William (Suzhou Laminate)
> Sent:         Thursday, April 6, 2000 11:31
> Subject:      Laminate porosity
>
>      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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