Application Of Diamond in New Electronic Packaging Substrates

Modern microelectronics technology is developing rapidly, and electronic systems and equipment are developing in the direction of large-scale integration, miniaturization, high efficiency, and high reliability. The increase in the integration of electronic systems will lead to increased power density, as well as increased heat generated by electronic components and the overall operation of the system. Therefore, effective packaging must solve the heat dissipation problem of electronic systems.

Good device heat dissipation depends on optimized heat dissipation structure design, packaging material selection (thermal interface material and heat dissipation substrate), and packaging manufacturing process. Among them, the selection of the substrate material is a key link, which directly affects the cost, performance and reliability of the device. Generally speaking, the application of electronic packaging materials needs to consider two basic performance requirements. The first is high thermal conductivity to achieve rapid heat transfer and ensure that the chip can work stably under ideal temperature conditions; at the same time, the packaging material needs to be reliable. Adjustable thermal expansion coefficient, so as to keep matching with the chip and all levels of packaging materials, and reduce the adverse effects of thermal stress. The development track of electronic packaging materials is the continuous improvement and optimization of these two properties.

 

Of course, new packaging substrate materials also need to consider other properties, such as high resistivity, low dielectric constant, dielectric loss, good thermal matching with silicon and gallium arsenide, high surface flatness, good mechanical properties and Ease of industrial production and other characteristics, so the selection of new packaging substrate materials is a hot spot for research and development in various countries. At present, several commonly used packaging substrates include Al2O3 ceramics, SiC ceramics, AlN and other materials.

 

As early as 1929, German Siemens company successfully developed Al2O3 ceramics, but the thermal expansion coefficient and dielectric constant of Al2O3 are higher than those of Si single crystals, and the thermal conductivity is not high enough, so Al2O3 ceramic substrates are not suitable for high frequency, large Power, used in VLSI.

 

Following this, high thermal conductivity ceramic substrate materials SiC, AlN, SI3N4, and diamond gradually entered the market.

The thermal conductivity of SiC ceramics is very high, and the higher the purity of SiC crystallization, the higher the thermal conductivity; the biggest disadvantage of SiC is that the dielectric constant is too high and the dielectric strength is low, so it limits its high-frequency applications and is only suitable for low density packaging.

 

AlN material has excellent dielectric properties and stable chemical properties, especially its thermal expansion coefficient matches that of silicon, so that it can be used as a semiconductor packaging substrate material with great development prospects. However, the thermal conductivity is low, and as semiconductor packaging has higher and higher requirements for heat dissipation, AlN materials also have a certain development bottleneck.

 

In the end, diamond stood out. Diamond has very good comprehensive thermophysical properties. Its thermal conductivity at room temperature is 700-2200W/(m·K), and its thermal expansion coefficient is 0.8×10-6/K. It has great potential in semiconductors, optics, etc. Many excellent properties, but a single diamond is not easy to make into packaging materials, and the cost is high.

 

According to the mixing rule, the diamond/metal matrix composite prepared by adding diamond particles into Ag, Cu, Al and other high thermal conductivity metal matrix is expected to become a new type of electronic packaging material with both low thermal expansion coefficient and high thermal conductivity. Based on the excellent electrical conductivity and high thermal conductivity of copper, a diamond/copper composite material was developed as a substrate material for electronic packaging, and it was confirmed that the diamond/copper composite material has good plating and solderability, which meets the Electronic packaging substrate materials require low thermal expansion coefficient and high thermal conductivity, and compared with Mo/Cu alloys, they have lower density and lighter weight.

 

Therefore, diamond/copper composites with diamond as the reinforcing phase and copper as the matrix material Materials can be used for chip packaging, which can improve the performance of electronic equipment systems and help reduce the weight of equipment.

With the continuous improvement of technical problems in materials, devices, etc., diamond has become a substrate material with high thermal conductivity and good heat dissipation. It has broad application prospects in higher temperature environments. The best semiconductor material for power density devices, its huge potential attracts more and more researchers to devote themselves to it. The potential of diamond will be gradually developed to meet the needs of the future semiconductor industry and occupy a place in semiconductor electronic packaging materials.