Dear Bo,

We had some trouble too at first with this "standard" technique. For us the
problem was that our PDMS layers were too thick. We have an ICP chamber and
we use something like 20 sccm of O2, 250 W ICP power, 100 W RIE power, 50 mT
chamber pressure, for 20 sec. We treat both the PDMS and the silicon.
Immediately after treatment we place the surfaces in contact, and
irreversible bonding instantly occurs. No pressure is needed. We also don't
pre-clean the surfaces, though we do our bonding as soon as possible after
curing the PDMS.

If your PDMS is more than a few millimeters thick, try bonding thinner
layers. Also, you may want to make sure that your PDMS surface is planar. If
you're casting it you can get edge effects you may want to remove.

There are quite a few papers reporting various treatment parameters, for
example Jo and Beebe, "Fabrication of Three-Dimensional Microfluidic Systems
by Stacking Molded Polydimethylsiloxane (PDBS) Layers," SPIE Conference on
Microfluidic Devices and Systems II, SPIE Vol. 3877, pp. 222-229. You might
look through this paper or others like it and check your other parameters. 1
minute is long compared to the treatment times most people seem to be using.

Best regards,
Jordan
--------------------------------------------------------
Jordan M. Berg, Ph.D., P.E.
Associate Professor of Mechanical Engineering
Texas Tech University
Lubbock, TX 79409-1021

[email protected]

> Message: 9
> From: "Bo He" 
> To: [email protected]
> Date: Tue, 09 Apr 2002 23:37:29 -0500
> Subject: [mems-talk] Bonding problem!
> Reply-To: [email protected]
>
> Hi,everyone:
>
>      I am trying to bond PDMS with silicon. I followed the recipe in some
> references: cleaning both surfaces with aceton, alcolhol and N2 dry then
> using oxygen plasma to treat both surfaces for 1 min. But results are
> bad, they cannot be bonded together. Any other recipes I can follow or
> some important steps missed in my operation? Please give me some
> suggestions.