New technology of military electronics - diamond wafer effectively improves the heat dissipation pro

In aerospace electronics, 65% of the mass of satellites is a refrigeration system, which is undoubtedly quite a headache, so how can this problem be alleviated? After continuous exploration by experts, it was found that the use of diamond chips and high-power diamond diodes and other heat dissipation technologies, the quality of the refrigeration system can be reduced by 90%, the launch cost is greatly reduced (the satellite and its launch cost will be reduced several times), and the diamond film can resist cosmic radiation and significantly improve the solar energy conversion efficiency.

An important application of diamond films in military electronics is the developing multi-chip assembly technology (MCM—multi chip modules). The goal of this technology is to combine many VLSI chips in a three-dimensional form into ultra-small ultra-high-performance devices, packaging technology from two-dimensional to three-dimensional development to form 3D-MCM, smaller size, assembly density, assembly efficiency and performance, more system functions, more I/0 pins, low power consumption, low cost, etc., can effectively reduce the connection distance of the chip, so that the signal delay and electrical performance between the chips are improved; However, with the increase of 3D-MCM integration and the reduction of volume, its power consumption per unit volume continues to increase, which will cause the heat generated by the chip to be too concentrated, resulting in a sharp rise in the junction temperature of the chip, and the heat dissipation of these chips is the key to this technology. The US military conducted feasibility studies on MCM technology, and demonstrated a demonstrative MCM supercomputer using CVD diamond film as a key component at the ADC conference in 1995, in which the diaphragm (10cm×10 cmx0.1cm) has a heat dissipation capacity of 20kw.

Figure 1 (a) cross-sectional view and (b) top view of 3DMCM

At present, there are three ways to dissipate heat in 3D-MCM devices: one is to use a substrate with low thermal resistance; The second is to use strong air cooling or liquid coolant to cool 3D devices; The third is to use thermal vias between the stacked elements to dissipate the internal heat to the surface. Diamond substrate application in multi-chip components can significantly improve the heat dissipation performance of 3D-MCM packaging, significantly better than silicon and aluminum nitride substrates, the use of forced air convection cooling multi-chip components can achieve obvious heat dissipation effect, heat dissipation power up to 120W.

In addition to heat dissipation, in this computer, diamond wafer are also used as encapsulation materials. The requirements of the packaging material are: high resistivity, high thermal conductivity, low dielectric constant, dielectric loss, good thermal matching with silicon and gallium arsenide, high surface flatness, good mechanical properties and easy industrial production. The general packaging materials are Al2O3 ceramics, SiC ceramics, and AlN materials. However, the coefficient of thermal expansion (7.2×10-6/°C) and dielectric constant (9.7) of Al2O3 are high compared with Si single crystals, and the thermal conductivity (15-35W/ (m·K)) is still not high enough, resulting in Al2O3 ceramic substrates not suitable for use in high-frequency and high-power electronic devices. The thermal conductivity of SiC ceramics is very high, and the higher the purity of SiC crystallization, the greater the thermal conductivity. The biggest disadvantage of SiC is that the dielectric constant is too high, and the dielectric strength is low, which limits its high-frequency application and is only suitable for low-density packaging; AlN material has excellent dielectric properties and stable chemical properties, especially its thermal expansion coefficient and silicon are more compatible with other characteristics make it can be used as a promising packaging substrate material, but the thermal conductivity is currently only up to 260W/ (m·K), with the improvement of 3D-MCM integration and the reduction of volume, its power consumption per unit volume continues to increase, AlN materials also have certain development bottlenecks. CVD diamond thermal conductivity can be as high as 2000 W/(m.K), thermal expansion coefficient of about 1.1×10-6/°C, in terms of packaging has the advantages that other materials cannot match.

Figure 2 Properties of diamond and other encapsulation materials

CSMH focus on the research and development and production of diamonds, with MPCVD equipment design capabilities, the first in China to master the core process of MPCVD to prepare high-quality diamonds and achieve mass production, and the original high-efficiency precision processing method of atomic-level surface of diamonds based on plasma-assisted polishing.   Diamond wafer Ra<1nm, diamond hot sink thermal conductivity 1000-2000W/m.k, and GaN on diamond, Diamond on GaN, diamond-based aluminum nitride and other products, to provide you with the most complete diamond thermal management solutions. At present, high-power semiconductor lasers using diamond heat sink have been used in optical communications, and are also used in RF power amplifiers, laser diodes, power transistors, electronic packaging materials and other fields. In the future, we will open up a broader path for diamond research and development and production