Ken, from our experiences at Circo Craft, the yields for liquid film versus
dry film are at least as good as, and in fact SUPERIOR to that of dry film.
We have several part numbers that MUST be run on liquid film imaging process
due to yield loss using the dry film process. In general we gain about 1 mil
of resolution using liquid compared to dry film. (ie existing production dry
film limit is 4/4, liquid is 3/3). We are aware of the pending introduction
of new dry film technologies aimed at less than 4/4, however it appears as
if this is in response to the current capability of liquid imaging technologies.

The fact is that both processes perform very well! I believe that the
reticence to evolve into liquid imaging is hampered by the magnitude of
capital equipment already invested in the dry film process, coupled with the
investment required in order to introduce a new process such as liquid imaging.

Dave Rooke
Circo Craft - Pointe Claire

- - - - - - - 

>Karl,
>The world is still relying on dry film for inner layer production.  According
>to articles generated in the early 1990's, the inner layer production was
>going to be 80% liquid by 1996.  This has not happened and in fact the
>liquid resist share use has actually diminished since those articles were
>written. The main factor behind this is simple economics.  Typically, liquids
>generate a lower production yield than dry film.  When loss of base
>laminate, production costs, and production time is considered in the yield
>loss, the dollar loss can be staggering. 
>
>Most of the world uses either a 1.3 mil or 1.5 mil dry film for inner layer
>production.  (SE Asia uses 1.0 mil on broader line technology)  The
>reason for this is that yields drop off considerably when resists below
>1.3 mil are used.  This is why the liquids at 0.5 mil are having such a yield
>problem, in general.
>
>1.3 mil dry film is very capable of producing 3 mil lines and spaces with a
>broad process latitude.  Etch rates don't come into play much until the
>dimensions of the lines approach the thickness of the dry film.  For
>instance the photo chemically machined lead frame industry is using 1.0
>mil, 0.8 mil, and 0.6 mil dry film on space dimensions breaking the 1.0 mil
>barrier.  We are even investigating thinner dry film coatings than these for
>this application.  Outside of Japan, dry film is still the resist of choice for
>these fine dimension etched parts.
>
>As far as carinogens, we have had a program in place for several years
>to eliminate carcinogens on our MSDS sheets with our new resists.  I
>doubt that this type of policy is in place outside of the US manufacturers.
>
>If you would like more information call me in California at 714 730 4200.
>Ken Bridges
>Product Manager
>Primary Imaging Photoresist
>Morton Electronic Materials
>
>
>>>> Karl Sauter <[log in to unmask]> 02/19/97 06:29am >>>
>
>Please advise re latest environmental and performance aspects of
>popular photoresists used for etching, primarily for inner layers
>including comparison of standard dry film versus liquid photoresists.
>
>The possible photoresist (resist for etching of inner layers) issues
>include:
>
> 1) The liquid photoresist is thinner (typical thickness ?);
>    a) more prone to handling damage ?
>    b) provides controlled trace width (ex: possible 3-mil trace/space
>       using an otherwise minimum 4-mil trace/space process) ?
>
> 2) Etch rates (aside from isolated lines with solution movement better
>    than for grouped lines);
>    a) standard dry film etch rate range ?
>    b) liquid photoresist etch rate range ?
>
> 3) Potential problem chemicals such as carcinogens;
>    a) does standard dry film contain any at-risk chemicals ?
>    b) does liquid photoresist contain any at-risk chemicals ?
>
>Thank you.
>
>Regards,
>Karl Sauter
>408 276-5499
>Sun Microsystems, Inc.
>
>
--- EOF ---

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