"King of Materials"-Diamond Heat Sink Writes a New Chapter in Thermal Management

As one of my country's strategic emerging products, diamond has been continuously developed and utilized for its "king of materials" characteristics. As a kind of superhard material, diamond not only has superhard mechanical properties, but also has the highest thermal conductivity and excellent thermal conductivity. Optical properties, semiconductor properties and excellent chemical stability, extremely versatile.

1) Semiconductor application: Diamond is an excellent wide-bandgap material with small electron affinity and extremely high hole mobility. It can be used as an ideal material for semiconductor devices such as chips.

2) Application of microelectronic machinery: diamond has the highest thermal conductivity and resistivity, and nano-diamond film is deposited on the surface of electronic component materials to reduce the size of heat dissipation components in the original components, providing the possibility for the production of ultra-large-scale integrated circuits; diamond film The layers protect the insulation and avoid mutual interference between components.

3) Optical application: It has extremely wide spectral band transmission and corrosion resistance, and is also widely used in the optical field, such as far-infrared optical windows, spacecraft windows, laser windows, protective films for lenses, etc.

4) Thermal application: The thermal conductivity of diamond is the highest among the known materials. As a heat sink material with excellent heat dissipation, it is mainly used in laser diodes and arrays, high-speed computer CPU chips, multi-dimensional integrated circuits, and military high-power radar microwaves. High-tech fields such as traveling wave tube thermal support rod, microwave integrated circuit substrate, integrated circuit packaging automatic bonding tool TAB, etc., improve the high temperature stability of the device.

5) Electrochemical application: Boron-doped diamond has a wide electrochemical window, strong electro-oxidative ability, low background current and good chemical stability, and is a good electrode material. It can be used for detection of harmful pollutants, sewage treatment, etc.

6) Medical device application: Diamond's high thermal conductivity, good optical properties, high chemical stability and harmlessness to the human body make it widely used in sensors in medical devices and X-ray targets for CT detection instruments Wait.

It is worth mentioning that diamond has the highest thermal conductivity of any material, making it an excellent choice for thermal management in electronic devices. Once a semiconductor device is fabricated, the chip must be packaged and built into an electrical system or electronic product. The excellent thermal properties of diamond materials - with the highest thermal conductivity and low coefficient of thermal expansion - can be used for thermal management in electronic packaging and power systems.

The thermal conductivity of diamond is five times that of copper. Although copper is a good conductor of heat, copper also conducts electricity. Metals conduct heat and electricity through free electrons. The circuit needs to be electrically isolated from the copper to prevent short circuits. However, diamond has a high dielectric strength.

Diamond, ceramic, glass and other electrical insulators conduct heat through phonons or lattice vibrations. Diamond has a rigid crystal lattice due to extremely strong atomic bonding. The rigid lattice of diamond provides a high vibrational frequency, and therefore a High Debye temperature of 2,220 K, which limits the impedance of phonon-phonon scattering.

The combination of high thermal conductivity and high dielectric strength of diamond heat sinks is very valuable for high power laser diode arrays, RF modules and high power transistors. Beryllium oxide (BeO) substrates are used in certain electronic packaging applications due to their combination of high thermal conductivity and dielectric strength. Diamond heat   sinks replace toxic BeO heatsinks while providing better heat dissipation. Electronic heat sinks and packaging substrates made of diamond are excellent at dissipating heat while also electrically insulating microelectronics from other devices and circuit components. Efficient heat dissipation extends the life of these electronic devices, and the high replacement costs of the devices justify the use of efficient, relatively expensive diamond heat sinks.

The thermal expansion coefficient of CVD diamond (about 1 ppm/°C) is much lower than that of silicon (2.6 ppm/°C), GaAs (5.7 ppm/°C), GaN (3.2 – 5.6 ppm/°C). C) and copper (16.6 ppm/°C). Thermal expansion differences must be considered and modeled early in the design process to prevent stress during thermal cycling from reducing device life and reliability. In some designs, the electronics are sandwiched between two diamond layers to balance the stress.

Thermal properties of diamond and various heat-dissipating materials

CSMH is the first company in China to master the core process of MPCVD to prepare high-quality diamond and achieve mass production, and has created an original high-efficiency and precision machining method of diamond atomic-level surface based on plasma-assisted polishing. The level of tens of microns is reduced to below 1nm, reaching the standard of semiconductor-level applications. High-power semiconductor lasers using diamond heat sinks have been used in optical communications, and are also used in laser diodes, power transistors, and electronic packaging materials.