Rick,
Some areas to check on:
1. LPI tack dry cycle. If you don't have your tack dry
cycle right, the LPI won't be hard enough to keep from
sticking to the artwork. Since you say the undried mask
comes out of holes, the cycle may be too cool or too short.
NOTE: Too hot and too long are bad as well. Don't overdo
this.
1A. Some LPIs don't tack dry effectively and subsequently
stick to the artwork during exposure. Ask the LPI image
operators if the stuff sticks to their artwork. Do it from
a distance to throw off their aim when they start throwing
things at you. This situation can be a real pain for
operators.
2. What LPI are you imaging? If you run more than one, do
both give you this problem?
3. How hot does your exposure unit get during LPI imaging?
Since these require more UV energy to expose, they build up
heat which can cause A/W hazing, sticking, etc.
4. How thick is your LPI coating? Too thick a mask does
not tack dry well, especially curtain coated mask and mask
next to overplated circuitry.
Hope this helps.
Dave Sullivan
Rockwell Collins, Inc.
[log in to unmask]
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Subject: diazo problems during lpi imaging
Author: [log in to unmask] at ccmgw1
Date: 12/16/96 1:29 PM
I am having 2 problems with our diazo artworks during lpi imaging.
After as few as 10 exposures, the film starts to develop a white haze (a
"ghost" circuit image) on the emulsion side. If caught soon enough, it can
be fairly easily wiped off.
The other (more serious) problem is uncured ink from the board's holes
depositing on the artwork. I either need a way to prevent this, or an easy
way of removing it from the film (film cleaner works marginally ok).
Here are the facts: We use Duratool film from Rexham Graphics. We have a
Technilith ammonia developer from James River running at 155 degrees. Our
uv density readings are around 4.6. Our lpi is Dexter Hysol SR8100R
(SR8300). We tack cure the lpi at 188 degrees for 68 minutes.
I'm sure you need more facts (nobody ever gives enough), so lay 'em on me!
Thanks in advance,
Rick
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Subject: diazo problems during lpi imaging
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