Lapping Heatsinks - Still a Good Idea?

[Giants_1]

I'm reading on-line discussions about lapping heatsinks and CPUs to get flatter surfaces for better heat conduction.

Curiously, the photos show mirror images (or lack thereof) with progressive sanding. Why not use a straight edge, which I think would reflect flatness better?

Anyone do with with an aftermarket heatsink, eg Hyper 212?

I'm also reading using a figure 8 motion with each grit in some, using only one direction with each grit in others to see the effect of removing scratches from the prior (or baseline) sanding. Thoughts?

Thanks

 

[KeelinTy]

In my opinion, lapping a heatsink wont help much if any. The only time I would suggest lapping a heatsink is when you are delidding. I have an EK Supremacy Evo for my 4790K and the block is curved a little for better mounting pressure. Since I delidded my cpu and im running bare die cooling, I lapped my waterblock for a much flatter base with better contact on the die. I also use Liquid Ultra as my thermal paste even tho its a metal and not a paste. But it helped my temps a lot. With delidding, lapping and CLU, I was able to run my cpu at 5ghz, 1.45v with load temperatures staying below 80c in occt. I believe my max temp was about 75c while running OCCT when before I would reach about 95c before lapping and CLU.

As long as your temps are fine, I wouldnt worry about lapping

 

[Susquehannock]

Yes. Reflection of a straight edge will help show distortions from unlevel surface.

Idea is to get most metal to metal contact with little thermal interface material as possible. Lapping can help significantly if the heatsink surface has rough finish or not flat from the production process. Fortunately things are better now than 15 years ago.