IGBT is a new type of semiconductor device. As the mainstream of new power semiconductor devices, IGBT plays a vital role in both traditional fields such as industry, communication, 3C electronics, and strategic emerging industries such as rail transit, new energy, smart grid, and new energy vehicles.
IGBT module is a power device, which has the advantages of low driving power, strong power processing ability and high switching frequency. However, it is also dependent on thermal characteristics. The weakness of power semiconductor modules is overvoltage and overheating. Therefore, its ability to deal with heat will limit its application of high power.
1. Thermal management in IGBT module
IGBT generates a lot of heat due to its high power density. The air gap between the power device and the radiator will produce very large contact thermal resistance, significantly increasing the temperature difference between the two interfaces. In order to ensure the efficient, safe and stable operation of IGBT module, the thermal management technology is also the most important link in the design and application of new products.
The general method used to reduce the Thermal resistance of Interface contact is to fill soft thermal conductive Materials, namely, Thermal Interface Materials (TIM). Reasonable selection of TIM should not only consider its heat conduction capacity, but also take into account the production process, maintenance operation and long-term reliability. The 10℃ rule shows that the device temperature is reduced by 10℃, the reliability is doubled. At present, the IGBT failure phenomenon caused by thermal runaway is the most common. It can be said that the failure reason of most of the IGBT power semiconductor modules is related to heat. The reliability of IGBT has become a hot spot in the industry research.
2.An efficient thermal management method for IGBT module
From the perspective of thermal design, thermal resistance can be reduced from three aspects: packaging material, TIM, and radiator. At present, the main cooling schemes of IGBT are air cooling and liquid cooling. The IGBT is directly installed on the radiator. The heat of IGBT module is directly transferred to the radiator shell through the TIM, and then the heat is taken away by air cooling or liquid cooling forced convection.
IGBT module heat dissipation diagram
In recent years, higher requirements have been put forward for TIM for IGBT: low thermal resistance and long-term reliability. In order to ensure customers' cooling needs for different IGBT modules, we propose multiple options of highly reliable cooling solutions for customers' different application needs.
(1)21-6series Series TIM graphite
Guarantee IGBT module, long-term reliability and no maintenance
The 21-6 series TIM graphite series belongs to low-density graphite and has certain compression performance. Because of its long-term reliability, it has been widely used by customers. 200 for engineers μ The compression-thermal resistance tests of m TIM graphite and 3.3W/m · K conventional Thermal Grease were compared. Under the compression stress of 70 PSI, the thermal resistance of TIM graphite is lower, with better thermal conductivity and long-term high and low temperature resistance. It can greatly reduce the costs incurred by customers for maintenance in the later period.
At the same time, the horizontal thermal diffusion coefficient of TIM graphite reaches 900 mm2/s, and it can be cut into specific shapes for easy installation. At present, it has achieved automatic assembly in terminal customers.
Thermal Resistance vs Compression
(2)21-4series anti-"Pump-out" thermal conductive silicone grease protects IGBT modules, ensuring safe and stable operation
Due to its good surface wettability and low contact thermal resistance, thermal conductive silicone grease was first used as a TIM in IGBT modules. However, due to the influence of thermal expansion and contraction of power devices during long-term operation, according to the previous experience of using traditional thermal conductive silicone grease, there will be some inherent material migration phenomenon, that is, the problem of "pump out", which will cause air gap between IGBT module and radiator, and increase the contact thermal resistance. On the other hand, with the volatilization of small molecular silicone oil, the traditional silicone grease will become dry due to sanding, which will affect the heat dissipation effect, and it is not easy to clean and the thickness is not controllable in the later maintenance. Therefore, the traditional silicone heat dissipation scheme will also cause customers to have doubts about the reliability and performance of IGBT modules.
The "Pump-out" thermal silicone grease series products perfectly solve the problem of traditional thermal silicone grease pumping, and ensure more effective heat dissipation and reliable operation of IGBT modules.
(3)21-7 series thermal conductive phase change materials guarantee IGBT modules and release latent heat as a new choice
Thermal conductive phase change material is a kind of material that changes its shape with temperature. 21-7 series of thermal conductive phase change materials remain solid at room temperature until the working heat of IGBT module equipment "melts" and soaks the entire interface, and its extremely low thermal resistance can effectively export heat. When it is lower than the phase change temperature, it will be converted into solid state again, which can avoid the risk of overflow like thermal silicone grease.
Continuously explore the new formula of thermal interface materials, respond to the new challenges of IGBT module heat conduction, ensure that the equipment has stable thermal performance within its life cycle, and develop a more efficient and reliable overall thermal management solution.
Article source (JONES)
