Lydia:

1) During exposure the catalyst is poisoned by the presence of oxygen.
People use either a nitrogen blanket or a very thin sheet of a UV
transparent plastic on top of the PDMS to block the oxygen.

 2) At 405 nm the catalyst free radical generation rate is very low. Aldrich
chemical has a UV absorbtion curve for DMAP which may be helpful. Also the
UV lamp intensity effects the cure rate.

3) The catalyst mixture and the amount added to the PDMS.

4) You could contact Gelest and ask for their recommendations for a catalyst
that is better at the longer wavelengths.

 I have tried to use UV cured PDMS but equipment limitations resulted in
unsatisfactory results.

I hope you have better luck.

allen




----- Original Message -----
From: "Z.,W.Y.(Lydia)" 
To: "General MEMS discussion" 
Sent: Tuesday, December 23, 2003 1:23 PM
Subject: [mems-talk] Photocurable PDMS


> Dear All,
>
> I read several posts regarding to adding photo initiator(DMAP)to PDMS so
that
> PDMS can become UV sensitive. I failed to repeat it. Highly appreciated if
> anyone can share the recipes in detail. Such as, are Pre-bake, or
post-bake
> reqired? what is the temprature for baking? how long the exposure time?
Can
> the mixture be use instantly after mixing? What color the mixture should
be?
>
> I tried Dow Corning (Sylgard 184) and (Gelest RMS-033). After mixing DMAP,
> Tulene, and PDMS, I degased the mixture and span coat the mixture to
pre-RCA
> cleaned Si wafer. The UV wavelength is 405nm. I exposed up to 1 hour with
> contact printing!!! I develped it in Xylene and IPA dry. Not work!
>
> Merry X'mas and Happy New Year!
>
> Lydia
>
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