Gareth Jenkins wrote:
> When spinning SU-8 2100 (at 1000rpm) I consistently get thicker than
> expected layers. According to the datasheets, I should get 260um but I
> get around 400um or more instead.
> I am using silicon as a substrate and everything else is fine - I have
> good adhesion and uniformity.
> It's not a huge issue as I can always increase the speed but it seems
> odd to have such a big variation. My SU-8 is quite old so perhaps I have
> lost some solvent from it?

This is possible. I talked once with the support of our supplier
and he told me that the typical aging effects of SU-8 are thicker
layers and the thickness of the layers isn't as uniform anymore.
The reason is in fact that the solvent evaporates.
Note, this is supposed to happen only *after* the expiry date.

cu
Michi