Just a random possibility thought here, based on a few comments in the thread... My skills in soldering are only very basic, so don't take this as even feasable.
So this whole idea is pretty much only for the CPU's that do NOT have thier IHS's laser soldered to the chip.
The problem I see is being able to heat both the IHS and heatsink to required temp to achieve optimal solder bond; then also being able to apply the solder and squash the two components together.
So rather than using a soldering iron or blow torch that some have suggested, what about heating the whole thing in an oven; would that work?
- take one IHS removed from CPU place on oven tray along with the heatsink
- place components in oven on xxxÂ°C (max?)
- while that is baking file down some solder (Not sure if this would be the best method...)
- sprinkle layer of solder on warmed IHS and place heatsink on top
- (add weight on top of heatsink ?)
- Bake for time x till solder melts, remove from oven & let cool.