Hi Marco,

If this is problem that occurs only with your contact films and not your
plotted films, then I would look first at your contact printing process.
It possible that it is rooted in your film (since this is a different film
than the plotter film), but I'd  look first at the contacting process.

It is quite possible that the film is getting distorted in the exposure
step, as Paul suggested.  In general, I recommend that you use a contact
frame designed for film-to-film contacting, such as those used in the
graphic arts (printing) industry.  Trying to use a resist printer (which
was designed for thicker panels and larger volume air evacuation) often
results in dimensional stability problems.  Also, some designs of contact
printer work better than others.  Many newer designs put high emphasis on
rapid air evacuation to give short vacuum drawdown times.  They do this by
various methods of applying pressure to push the air out.  Some of these
can produce machanical distortion of the film at the same time.  Some work
fine.

I suggest the following:

1.  Be sure your contacting film is equlibrated the same way your plotting
film is.

2.  Use a stiff, black, matted, plastic backup sheet behind your film when
you expose it.  This will tend to protect the film from mechanical
distortions.  These are available commercially in the U.S. through graphic
arts suppliers.  I am uncertain about availability in Japan.

3.  Use adequate drawdown time to insure complete air evacuation.  One to
two minutes may be required on some contact frames.  Run a test to
determine what your frame needs.

4.  In order to separate size changes that occur during exposure verus
those that occur during processing, it is possible to expose a piece of
film, apply developer to the areas that contain the fiducials with a cotton
swab, then fix the fiduals by applying fixer with a cotton swab.  Now turn
on the lights and carefully rinse the processed areas with another cotton
swab containing water.  Allow the film to dry before measuring it.


If you still can't find the cause of your size change, send me a note
directly with the details of your process (type of contact frame, type of
film, process steps, etc.) and we'll spend some time tracking it down.

Best regards,

Bob Seyfert
DuPont Electronics



At 09:04 AM 5/23/98 +0800, you wrote:
>Hi John,
>Sorry guys if I misunderstood.  We do have a glass base over which the
>films are laid and then this is covered by a rubber covering before vacuum
>and exposure.
>I have always checked the film dimension after developing; I haven't really
>checked the dimensions of the film after exposure since only a latent image
>is seen (we're using silver halide for our contacts), but I'll try.  We do
>use overcoats over our films (PPF) but this is applied later during the
>process.
>
>
>John Waite wrote,
>>
>> Hi Marco,
>>     What Paul is referring to is if the drawer has a glass base, and the
>top side has a mylar.
>> It sounds like you have a "glass pac" style tooling.  AT what point do
>you see the "distortion".
>> Is is off the diazo developer or during exposure, or after transfer of
>the phototool to imaging
>> area.  Also, are you using a covercoat over your diazo (IE- APF,PPF,
>etc).  Sorry about my
>> misinterpretation.  I thought you were using 1st generation silvers.
>JOHN WAITE
>
>>
>> Marco Biagtan wrote:
>>
>> > Hi Paul,
>> > I'm sorry but I don't quite understand what you mean about the single
>sided
>> > glass exposure frame.  The flexible membrane of our exposure machine
>has a
>> > thin glass frame on top of it as well as a thick glass frame where we
>lay
>> > our films.  Is this the same?
>> >
>> > Anyway, thanks a lot for the suggestion.  This is the first time I've
>heard
>> > of this and it might just be what I'm looking for.
>> >
>> > Marco Biagtan
>> > NEC Components Phils. Inc.
>> > Process Engineer
>> >
>> > Paul Gould wrote:
>> >
>> > > Marco,
>> > > Just had another thought if it is only your contacts. If you are
>using a
>> > > single sided glass exposure frame with a flexible membrane over the
>top,
>> > > your copy film will be in contact with the membrane and will tend to
>get
>> > > mechanically stretched. This would result in an apparent shrinkage
>after
>> > > exposure. If this is a possibility, put a sheet of black card on top
>of
>> > > the film before closing the lid and pulling the vacuum.
>> > > Hope this helps.
>> > > Paul Gould
>> > > [log in to unmask]
>> > > Teknacron Circuits Ltd
>> > > Fax: 1983 865141
>> > > Tel: 1983 866531

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