[H]ard|OCP have been spending a lot of time removing the integrated heatspreader on recent Intel chips to see what effect it has on temperatures under load.  Along the way we picked up tips on 3D printing a delidder and thankfully there was not much death along the way.  One of their findings from this testing was that it can be beneficial to reattach the lid after changing out the thermal interface material and they have published a guide on how to do so.   You will need a variety of tools, from Permatex Red RTV to razor blades, by way of isopropyl alcohol and syringes; as well as a steady hand.  You may have many of the items on hand already and none are exceptionally expensive.

"So we have covered a lot about taking your shiny new Intel CPUs apart lately, affectionately known as "delidding." What we have found in our journey is that "relidding" the processor might be an important part of the process as well. But what if you do not have a fancy tool that will help you put Humpty back together again?"

Here are some more Processor articles from around the web:

Processors