I wouldn’t do that. I recommend making sure that you’ve got a Hyper 212 quality cooler, good thermal paste between the CPU and the fan, and plenty of Airflow. If your temps are still high, I’d suspect a number of background processes are stressing out your CPU or perhaps even some cpu/ram/motherboard chipset settings in your bios need to be reviewed.
Popping off the lid of your cpu to apply thermal paste for cooling is like nuking a mountain to get rid of a molehill — it might work, but there’s a lot of additional costs and risks involved that make the proposition untenable for not a major benefit when potentially better options are available.