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August 1997

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Subject:
From:
"Larry J. Fisher" <[log in to unmask]>
Reply To:
TechNet Mail Forum.
Date:
Fri, 29 Aug 1997 21:11:20 -0400
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Since I have lived through and been part of it, I would like to suggest a
 technological change  that has occurred in the PWB manufacturing industry:
I'm sure other people can offer many others.

1. During that time frame (1988 to the present), aqueous processible, liquid,
photoimageable (LPI) solder masks have grown from a small foothold of the
market in North America to domination of the market. This growth has come at
the expense of solvent processed LPI masks, thermal cure and UV cure masks
and the dry film solder mask types. At this point, by far the majority of
square footage of circuits boards produced in North America are coated with
LPI solder masks. To support this huge growth, there has been a substantial
growth in equipment for applying and processing these masks, such as:

   A. Vertical, double sided screening machines have become the dominant
method for applying these LPI masks, although there has also been growth in
alternative application types, such as spraying, electrostatic spraying and
curtain coating.

   B. Tunnel drying and curing ovens. These support rapid and consistent
drying and curing of the LPI masks.

   C. High powered exposure machines (6, 7 & 8 KW). These provide much
quicker exposure times for the LPI masks, plus less heat buildup, phototool
distortion, phototools sticking to the masks, etc.

     Although there have been other technological changes that have occurred
in PWB manufacturing overthe past 10 years (direct plate systems, liquid,
primary image photoresists, reducers for oxide, etc., I can think of none
that have had the same kind of revolutionary impact on PWB manufacturing as
the aqueous LPI masks. It seems to me they are akin to other revolutionary
types of technologies in the past, such as dry film photoresist, electroless
copper, acid copper sulfate plating copper, SMOBC, etc.

I would be very interested in other people's experiences and opinions and I
can't wait to see the CircuiTree article.

Hope this helps.

Larry Fisher
Dexter Electronic Materials
[log in to unmask]


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