How to remove the heat sinker on Xilinx FPGA chip?

Hi,
I need to measure the tiny EM leakage from cells of the FPGA chip. So I have to locate the EM probe to the surface of the chip as close as possible. However, the heatsinker covers the surface of the chip .
Can you please give me some guidances to remove the heat sinker on the FPGA ? Or is there any official guidance to do this work from XILINX ? I checked by google, however haven´t find.

Thanks very much!

Eric,

Can you provide a photo of tha
t heatsink? How is it mounted?

Well, I've already done it. I don't know the type of the heatsink. It's deployed on a type II (hat shape) lid. I just used a blade to leverage the heatsink off from a corner of it. It seems not difficulty. The adhesive is soft due to the hot weather here. So, it was removed just easily.

Thanks!!

Once I had to recover a very large QFP with a heatsink (I don't know the purpose of the chip). Heatsink was mounted with thermal adhesive to the chip package and with some kind of rivets to the pcb. First i have bored out the rivets with a drill. The thermal adhesive was very strong, so i couldn't pry the heatsink off without risking damage to the chip. In fact it wasn;t plastic at all. I've cut away a large portion of the heatsink with dremel tool and then peeled off the rest (gently) until no metal was left. The remaining adhesive appeared to be completly immune to IPA and turpentine. As pure lab-grade acethone is kind of hard to get in Poland sometimes (semi-controlled substance, may be used for producing certain kinds of illegal substances) i used an ordinary 'nitro' paint thinner. Worked like a charm, the chip was intact apart from signature on top of it being gone.