As far as my experience.... No....

  SU-8 do not absorb water. I used SU-8 water heater coating material and worked
fine so far. It could absorb water I couldn't notice but I think that also be
negligible.

  sokwon

Michael Larsson  wrote:
  Hi everyone,

Polyimide is a common dielectric material used in micromachined,
planar RF components to reduce coupling between RF signals and lossy
Si substrates. A drawback is the fact that this polymer absorbs water,
causing changes to RF performance with time and environmental
conditions. Does anyone know if the same is true of x-linked SU-8?