Improvements and developments in semiconductor technology have made it possible to achieve higher current densities, thereby increasing the temperature of the chip. In 2005, the maximum allowable chip temperature of 600V IGBTs and freewheeling diodes increased by 25°C to 175°C and is moving towards 200°C.
Higher operating temperatures and current densities have a negative impact on reliability, especially load cycling capability. To address this, improving installation technology is critical.
A fundamental difference between different power modules is whether they have a substrate. In the substrateless module, the DBC backplane is mounted directly on the heat sink. The substrate, for example made of 3mm thick copper, increases the heat capacity and thermal diffusion under the chip, reducing transients in a time range of approximately 0.1 to 1 s compared to modules with insulated ceramic substrates as the outer plate. Thermal impedance. It must be noted that the large area welding between the insulating ceramic base plate and the substrate significantly reduces the load cycle capability of the assembly. The reason for this phenomenon is because the ceramic substrate and the substrate have significantly different coefficients of thermal expansion. This difference leads to tension and ultimately solder fatigue. Another alternative to copper substrates is substrates made of composite materials such as AlSiC or CuMo, which are used only in traction applications due to their low thermal conductivity and high cost. The low cost of graphite-based composites can be an important substrate material in the future.
In practical applications, the lower thermal diffusivity of the no-floor module can be compensated for by using a thinner thermal coating. This method is possible because there is no air gap between the module and the heat sink in the no-floor module. Efficiency can also be improved by ensuring a symmetrical modular layout. The symmetry of the module layout ensures that the inductors are evenly distributed, and all chips share the same amount of current and switching symmetrically, coupled with the use of planar assembly techniques and low spurious connections, the overvoltage associated with power modules is typically reduced. The switching efficiency is increased by about 15%. Figure 2 shows a comparison of the power modules with or without a substrate.
Figure 2 Comparison of substrate and substrateless modules
Silicon carbide (SiC) is beginning to attack, especially in freewheeling diodes and MOSFETs. It has found many applications in switch mode power supplies. SiC allows a junction temperature of 200 °C. The reliability of the assembly technique and the impact of the materials used (plastics) must be monitored. SiC's switching speed is very fast and provides a well controlled and defined output. When used with the latest generation of IGBT products, the efficiency of the system will increase by 20% to 30%. However, it is still very expensive and needs further development before it is widely used.
Therefore, power semiconductors are very important in the electronics industry for power transmission and conversion. The emerging markets for power semiconductors are the alternative energy sector and the automotive industry. The most important trends in the development of labeled power semiconductors are improvements in cooling technology, higher current densities, and integrated driver electronics. In terms of reliability costs, higher operating temperatures and better cooling are only possible. The only way to solve this problem is to develop new concepts of installation and assembly.
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Product Name: Iron Powder reduced
Search number: [CAS 7439-89-6
Molecular formula: Fe
Molecular weight: 55.845
Properties: Black amorphous powder. Soluble in dilute acid, insoluble in concentrated acid, dilute alkali solution exposed in the air and ether.
Or in case of water is easily oxidized.
Uses: powder metallurgy products reduced iron powder. Chemical reduction iron powder, mainly used in chemical catalyst, precious metal reduction, alloy addition, copper replacement.
Iron Powder
Iron Powder,Chemical Reducer Iron Powder,Iron Compounds,Low Silicon Iron Powder
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