Diamond Heat Sink - Heat Dissipation Magic for IGBT Power Modules in New Energy Vehicles

In the booming development of new energy vehicles, the performance and reliability of IGBT (Insulated Gate Bipolar Transistor) power module, as the core component of motor drive in new energy vehicles, are crucial. Diamond, known as the “king of hardness”, is gradually showing great potential in the field of heat dissipation of IGBT power modules in new energy vehicles.

IGBT's core position in new energy vehicles

1. Definition and basic structure:

Definition: IGBT is a composite fully-controlled voltage-driven power semiconductor device composed of BJT (bipolar triode) and MOS (insulated gate field effect tube). It combines the advantages of high input impedance, simple control and fast switching speed of MOSFET and the advantages of low on-state voltage drop and high current density of BJT, which can realize the switching control of high current and high voltage.

Structure: It is mainly composed of three parts. First, the metal oxide semiconductor oxide layer (MOS), which is the core part of the IGBT, can be controlled by the control circuit to control its current and voltage and other parameters; second is a bipolar transistor (BJT), consisting of two bipolar transistors, capable of generating high power; third is the insulating layer, which plays a role in protecting the IGBT components from the external environment erosion and damage.

2. The principle of operation

When a positive voltage above the threshold voltage is added between the gate - emitter of the IGBT, a reverse-type layer (channel) is formed on the P layer directly below the gate electrode, and electrons begin to be injected from the N - layer under the emitter electrode. The electrons act as minority carriers in the P+N-P transistor and begin to flow into the holes from the collector substrate P+ layer for conductivity modulation (bipolar operation), which reduces the saturation voltage between the collector-emitter and causes the IGBT to turn on. When a negative bias is applied to the gate or the gate voltage is lower than the threshold, the channel is disabled, no holes are injected into the N-region, and the IGBT turns off.

Importance of Heat Dissipation in IGBT Power Modules

IGBT power module in the working process will produce a large amount of heat, if you can not timely and efficiently to disseminate this heat, will have a serious impact on its performance and life. Specifically manifested as:

1. Performance degradation: excessive temperature will lead to an increase in the on-resistance of the IGBT and an increase in switching losses, thus reducing its efficiency and output power. At the same time, high temperature will also affect the electrical characteristics of the IGBT, such as threshold voltage, saturation voltage drop, etc., so that the control accuracy of the inverter decreases.

2. Shorter life: working in a high temperature environment for a long time will accelerate the aging and damage of the internal materials of the IGBT power module, such as thermal fatigue of the semiconductor chip and thermal expansion of the packaging materials. All of these will lead to a reduction in the reliability of the IGBT and shorten its life.

Therefore, in order to ensure the normal operation and long-term reliability of IGBT power modules, effective heat dissipation measures must be taken.

Unique properties of diamond

As a super-hard material, diamond has many unique properties that give it a great advantage in IGBT power module heat dissipation.

1. High thermal conductivity: Diamond has the highest thermal conductivity of any known natural material, reaching about 2000 W/m・K, which is 4-5 times higher than that of copper and silver. This high thermal conductivity enables diamond to quickly conduct the heat generated by the IGBT power module, effectively reducing the module temperature.

2. Low Coefficient of Thermal Expansion: Diamond has a low coefficient of thermal expansion, which means that the dimensions of diamond change relatively little when the temperature changes. In IGBT power modules, when diamond is used in combination with other materials (e.g., metal packaging materials, semiconductor chips, etc.), the low coefficient of thermal expansion reduces the thermal and mechanical stresses due to temperature changes, and improves the stability and reliability of the heat dissipation system.

3. Good thermal stability: diamond has excellent properties such as high temperature resistance, corrosion resistance, anti-irradiation, etc., and can still maintain good structural and performance stability in high temperature environments. the IGBT power module will generate high temperatures during operation, and diamond's thermal stability ensures that it will continue to effectively play the role of heat dissipation at high temperatures, and will not be degraded or structurally damaged due to the rise in temperature.

4. Phonon Transport Advantage: In diamond, heat is mainly transported by phonons (lattice vibrations). The stability and hardness of the diamond crystal structure allows phonons to propagate through the lattice with very little damping, thus allowing heat to be transported at a very high rate. Compared with the way heat is conducted through free electrons in metallic materials, the phonon thermal conductivity mechanism of diamond has better stability and efficiency at high temperatures and high power conditions, and is able to adapt to the complex thermal environments in which IGBT power modules operate.

CSMH uses the MPCVD method to prepare large-sized and high-quality diamonds, and currently has mature products such as diamond heat sinks, diamond wafers, diamond windows, diamond hetero junction integrated composite substrates, etc. Among them, the thermal conductivity of diamond heat sinks is 1000-2200W/(m.k), and the surface roughness of diamond wafer Ra<1nm. lt has been applied in aerospace, high-power semiconductor lasers, optical communication, chip heat dissipation, nuclear fusion and other fields.