Hi Steven,

What is the width (or range of widths) of your microchannels and what
is the intended application - i.e. what fluid(s) do you intent to pass
through it?

You may be able to improve adhesion between the SU-8 layer and the
substrate using chemical treatments or other forms of surface
modifications, however, this is unlikely to survive the transition
from lab prototype to reliable, functioning device. This is especially
true if your microchannels are conveying solvents or chemically
aggressive fluids.

You can ensure robust adhesion between SU-8 and the substrate in
microfluidic applications using mechanical interlocking. The papers
below will help if you pursue this route:

i) "Improved polymer–glass adhesion through micro-mechanical
interlocking", M P Larsson et al 2006 J. Micromech. Microeng. 16
S161-S168

ii) M P Larsson et al 2005 J. Micromech. Microeng. 15 2074-2082

Regards,

Michael


> -----Original Message-----
> From: mems-talk-bounces@memsnet.org on behalf of Steven Yang
> Sent: Fri 1/11/2008 10:10 AM
> To: mems-talk
> Subject: [mems-talk] How to improve SU-8 adhesion?
>
> Hi, all
>
> Asked some questions on SU-8 2050 several days ago, still stuck on it now..
>
> The problem is the peeling off at some SU-8 2050 microchannel
> edge.(SU-8 2050 on PECVD SiO2). Without SiO2 layer, the situation will
> get better with seldom cracking and peeling off. However, on PECVD
> SiO2 it always turns out this problem more or less.
>
> I have increased the temperature and time for dehrydration at 180C for
> 30mins. and exposured for 40s at 7mW/cm2, PEB at 65C, 95C for 5 and 15
> mins respectively (Same as softbake). No much different.
>
> If there is no any further solution based on recipe modification, will
> the HMDS get the thing better? If so, could anyone give some
> suggestion on the HMDS spin procedure? below is what I plan to do.
> 1) dehydrate at 150C for 15mins
> 2) spin HMDS at 7500rpm for 35s
> 3) dehydrate at 150C for another 15mins
> 4) spin SU-8 2050 at 4000rpm for 45s
>
> Any suggestion?