Polycrystalline diamond heat sink

This is far from the only similar material to exist, but this one has the highest thermal conductivity of anything :   2,200W/m.K (Wm-1K-1, written otherwise), around 5x compared with copper which scores ~400W/m.K and insulating thermal conductos like aluminium nitride and (toxic) beryllium oxide which score 200 to 300.

It is called Diamond heat sink.The diamond thermal material engineered to offer industrial users thermal conductivity in excess of 2200W/m.K. It provides the unprecedented ability to rapidly cool electronic devices with power densities that exceed 1kW/cm2, increasing electronic device productivity and reliability.

This is a CVD material, engineered to have largely isotropic thermal conductivity: kcross-plane/kin-plane = ~1.0).

Bulk resistivity is 1013Ωm and surface resistivity is 1011Ωm.

Laser-cut blanks in standard thicknesses can be made to meet specific customer requirements, with sputtered thin film metallisation to make it wire bondable or solderable.

Thickness are available from 100μm to 2mm, with diameters up to 140mm.

Unlike metals, heat conduction is dominated by phonon lattice vibrations, and some of its characteristics are quite non-linear.

For example, thermal conductivity is 2,200W/m.K at 293K, but 1,620W/m.K at 425K (152°C). It actually peaks at pver 7,000W/m.K somewhere between 100 and 150K. Other Diamond materials, have a far less peaky thermal conductivity curve, although TM220 always has the highest thermal conductivity at any given temperature.

The coefficient of thermal expansion is also non-linear, increasing with temperature. It as: 1.07ppm at 300K, 1.81ppm at 400K and 2.45ppm at 500K.

Applications are foreseen in gallium nitride (GaN) based RF and MMICs (monolithic microwave integrated circuits) for phase array radar, satellites, other space, 5G base stations and the success of terabit rate optoelectronics networks for both metro and long-haul content delivery is predicated on high efficiency thermal management.

UNICS-CVD-diamond-thermal-graphHeat spreading

Effective heat removal from hot small things is a game of heat spreading, with a material of high thermal conductive immediately adjacent to the hot part to give heat the easiest path out.

This spreader is shaped to offer a wider area on its output side to ease the heat’s path across the next thermal transition.

Given that the very best spreader tend to be expensive, the thermal path tends to be arranged in a cascade of layers of increasing area and decreasing cost, ending with bulky aluminium to finally conduct or radiate the heat into the equipment’s environment.

UNICS-CVD-diamond-heat-flowThe materials have to be chosen to have compatible thermal expansion through the cascade.