CASE CLOSED. found a video in which someone shows the pcb for a very short time. they are like regular omron ones which have a removable cap.
this is good to mod it like this: http://www.silentpcreview.com/forums/viewtopi...0f43f2f9f3

already did that on other mice, its really nice. everyone should use it on the mico, it reduces force needed to push the buttons significantly. mind the warranty though, but on the other hand also mind RSI...

Omron D2F-01F Pre-2005.
Omron D2FC-F-7N Post-2005

Changed mid year iirc.

thanks, this is good to know