Hi
I guess a "soft cure" (75% according to DOW) of BCB would help to improve the
adhesion between BCB and subsequent layer. You will need to eventually
complete BCB cure ("hard cure") after SU-8 patterning. This normally is done
at a baking temperature of 250 degree. If such a high temperature raises
concern for SU-8, the hard cure can also be achieved at a lower temperature,
although with a much longer baking time. www.cyclotone.com has all these tips.

Another possible cause could be SU-8, say under exposure or solvent not fully
evoparated. Try increase exposure dose or the soft bake time/temperature.

Hope these helps.

Xianling Chen
Photonics, TRLabs
Edmonton, Canada

>===== Original Message From "Michael A. Powers"  =====
>Hello,
>
>I have experimented with SU-8 layers patterned on BCB.  The adhesion at the
>SU-8 / BCB interface varies from poor to awful.  Has anyone else tried this
>before?  I've tried AP3000 as an adhesion promoter to no avail.
>
>Thanks,
>-M. A. Powers