Baseplate grooves

As most of today's PC enthusiasts use high-viscosity thermal compounds, the contact surface of Noctua coolers is optimised for use with this type of paste. The micro-grooves at the contact surface ensure that high-viscosity thermal compounds are dispersed to a uniform thin layer across the whole contact area and that no air pockets remain between the cooler and the CPU. 

With a polished, mirror like surface, the risk of uneven dispersion is much higher. As too thick layers of thermal paste and air pockets drastically deteriorate heat transmission, the micro-grooves are of vital importance to the overall cooling performance of Noctua coolers when used with today's high-viscosity thermal pastes.

Convex baseplate

As the Integrated Heat Spreaders (IHS) of today’s CPUs are slightly concave, the cooler’s contact surface has been deliberately designed to be slightly convex in order to ensure optimal contact. This way, more contact pressure will be applied at the centre of the IHS directly above the DIE, which results in better heat transfer and improved overall performance. 

NH-D15 G2 with convexity options

Not all CPUs are created equal and can differ in flatness of their heat-spreaders, but also their die configuration and location. Therefore, the NH-D15 G2 comes in a standard convexity (as explained in this article) version (NH-D15 G2), a low base convexity (NH-D15 G2 LBC) and a high base convexity (NH-D15 G2 HBC) version.

To find out which version is the best choice for your use case, please read this FAQ entry.