Subject: | |
From: | |
Date: | Wed, 08 May 96 17:02:58 |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
I agree with the below comments and would add:
The thicker the resist viscosity and coating weight, the greater the
possibility of bubble retention. The lower the temperature, generally
the thicker the viscosity. Fast stirring will fold air into the
system so stir as slowly as possible but long enough for complete
mixing. It's generally best to stand before use to let trapped air
come out over a period of an hour or so. Perhaps more to the point...
Talk to your supplier.
LPISM suppliers have tech support staff to whom problems like this are
bread and butter. Viscosity control is sensible even just before use
in cases where little mixed mask is used per shift (some masks thicken
on storage) but this might not be the whole answer. Part of the job
of formulating LPISM's involves additives to reduce bubbling,
reticulation etc. Your supplier will know about bubbling and should
be able to help. He might even be able to recommend a minor change in
resist (viscosity, thinning solvent etc) to meet your particular
requirements.
Bob Courtney
Coates Circuit Products
______________________________ Reply Separator _________________________________
Subject: FW: Ink preparation mixing bubbles
Author: [log in to unmask] at Internet
Date: 07/05/96 10:56
My experience with bubbling has been that the viscosity of the ink is
most critical.
Mixing will always inject air as does forcing the ink through a screen.
The key factors are; how viscous is the ink (It's hard to get bubbles out
of peanut butter.),
how thick is your coating (thicker coatings are harder to get the bubbles
back out of), and how long do you allow product to sit for de-bubbling
before tack-dry at what temperature.
We had a rash of bubbling problems recently when one of our two suppliers
sent in some thicker than normal ink. We're looking at incoming
inspection for viscosity.
|
|
|