CrazyPC Opion on Heatsink Lapping

I have always held that a flat heatsink base and CPU surface make the best setup for CPU Cooling. We offer a heatsink lapping option on some of the heatsinks we sell. In the case of Prolimatech we have decided to make this option available despite the position of the manufacturer that it should not be lapped. As it was explained to us the Megahalems base is designed with a curve to it on purpose. This design is intended to offer superior cooling. We agree that unmodified this design will offer good cooling. However, we believe that there are still good reasons to lapp a heatsink and benefits to be gained. If you're interested read further.

When to Lapp?

A heatsink should benefit from lapping in the following circumstances:

• The base is not flat. Heatsink bases may be curved, convex, concave, non-symetrical.
• Poor finish: A base that is not smooth or has many grooves can be a good candidate for lapping.

Flat vs Curved Base

My argument for lapping - Consider a CPU base that is curved so that it is convex or conical. This base will have a pressure point in the raised area that makes contact with the CPU heat spreader. Pressure between heatsink and CPU heat spreader helps with heat transfer. The curved base thus creates a higher pressure area at a specific point of the heatsink. Now take a flat base and mount it using the same pressure as the heatsink that is curved. In fact there are some mods on water blocks that accomplish this by actually bending the blocks using a rubber ring. A flat base will have a greater surface area which is good for cooling but the pressure will be spread out more resulting in less pressure per square inch. Less pressure is not preferred.  This may result in non-optimal cooling performance as it does not cool at a specific point as is the case with a curved base. However, the trick here is that we have not compensated for the decrease in pressure with the flat base. My supposition is that a flat base will provide superior cooling by offering a broader surface area provided that A) sufficient pressure is applied and B) the cooling capacity of the heatsink is not reached due to increased heat load (doubtful).  It's easy enough to increase pressure by putting a thin spacer under a mounting bracket or some such similar method.

In Conclusion, a curved base may provide better cooling by increasing pressure at specific critical points of contact thus giving better cooling. However, I believe that a flat base will ultimately be superior provided the pressure is increased to match.

I welcome a scientific benchmark to validate the benefits of lapped vs non-lapped heatsinks. In fact we would be willing to offer a heatsink to a competent reviewer that is willing to do conduct an analysis. Until then we will continue to offer our lapping service. Buyers should be aware of the pos and cons of lapping and accept the risks as well.

Sincerely,

Nick Curtiss

CrazyPC.com