Suzanne:
There are several papers by Lotters, J.C. using photo patternable PDMS.
Lotters
uses a Methacrylic PDMS copolymer from ABCR (German chemical company). The
equivalent material is available from Gelest and United Chemical
Technologies in the US. The initiator is available from Aldrich chemical.
One problem with the initiator is that it has a low response to the I-line
(365nm) . The copolymer is still a liquid when exposed so that unless a
plastic sheet is covering the polymer, your masks could get coated. Lotters
uses a plastic sheet also as an oxygen barrier. Oxygen inhibits the free
radical polymerization.
The control of the exposed line width, depending on your requirements, is a
problem due to the long exposure time required in a mask aligner. The lines
are not necessarily well defined. A germicidal fluorescent light has a peak
output around 250 nM which is almost the same as the initiator peak UV
absorption point. The use of a germicidal lamp as an exposure tool has
not been tried as far as I know. A disadvantage of the gerimicidal lamp is
mask alignment, it is not collimated, and some or most of the wavelength
advantage could be lost due to absorption of the mask material.
If you are using the copolymer for its mechanical properties there has been
a problem with repeatability of the Young,s or shear modulus. This is
probably due to the exposure conditions, including the oxygen barrier.
In a recent issue of Chip Scale Review magazine Dow Corning had a two page
insert on their photo patternable PDMS for wafer scale packaging.
Unfortunately, the insert did not have a product name for the PDMS and
getting a sample has so far been a problem.
Companies do make photo patternable PCB board coatings. They tend to be
either gels ( as from dow corning), or the scratch resistant type.
allen kine
University of California,Irvine
[email protected]
At 09:58 AM 8/20/02 -0700, you wrote:
>Hello Bo,
>I just started looking for the same information, this is all I've found so
>far: http://www.ucop.edu/research/micro/98_99/98_144.pdf.
>Suzanne
>
>-----Original Message-----
>From: [email protected] [mailto:[email protected]]On
>Behalf Of Bo He
>Sent: Monday, August 19, 2002 12:04 PM
>To: [email protected]
>Subject: [mems-talk] Patternable PDMS
>
>
>Dear MEMS expert:
>
> Are there any articles about how to pattern PDMS by conventional
>photolithography? Any input is highly appreciated.
>
>
>
>Bo
>
>
>
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