Hi, We are making very thick SU-8-25 samples using a metal mold (several mm thick). The softbake goes fine, but when the sample is exposed to UV a thin film layer forms on top of the evaporated sample. Tests have confirmed that this layer is crosslinked, but no heat has been applied. It is believed the UV lamp does not provide enough heat to start the crosslinlinking process. The remaining SU-8 under the film does not crosslink when exposed to heat, indicating that it is not receiving any UV radiation. What is the maximum depth that UV radiation can penetrate SU8-25? Various literature sources say layers of SU-8 ranging from 200 - 700 microns are possible using a conventional spin coater, but are these figures due to limitations in the spin coating process or in the UV absorption of the SU-8? I would appreciate any thoughts/comments. Thank you Jason McCallum email: Jason.McCallum@CRT.Xerox.com