Integration Level of Power Electronic Modules The differences between semiconductor modules are not limited to connection technologies. Another differentiating factor is the integration level of additional active and passive components. Based on the level of integration, they can be categorized as follows: standard modules, intelligent power modules (IPMs), and (integrated) subsystems. While IPMs are widely used (especially in Asia), the use of integrated subsystems is only just beginning. Intelligent Power Modules (IPMs) are characterized by the presence of drive circuitry in addition to power semiconductor devices. Many IPM modules also include temperature sensors and current balancing circuits or shunt resistors for current measurement. Typically, intelligent power modules also integrate additional protection and monitoring functions, such as overcurrent and short-circuit protection, driver power supply voltage control, and DC bus voltage measurement. However, most intelligent power modules do not provide electrical isolation for the signal input on the power side. Only a very small number of IPMs include an integrated optocoupler. Another isolation solution is to use a transformer (Semicon's SKiiP® or Infineon's PrimeSTACK™). Typically, smaller-scale IPMs are characterized by their lead frame technology. Perforated copper plates serve as the carrier for power switches and driver ICs. Heat dissipation is achieved through a thin layer of plastic or insulating metal. IPM modules designed for medium to high power applications are characterized by a two-tiered design: power semiconductors at the bottom, and drivers and protection circuitry at the top. The most well-known IPM in the field is Semikron's SKiiP®, which has been on the market for over 10 years. This baseboard-less IPM series has a maximum rated current of 2400A and includes a driver and protection function, plus a current sensor, electrical isolation, and power supply. These modules are mounted on air-cooled or water-cooled coolers and undergo comprehensive testing before shipment. An interesting trend is the upgrade from standard modules to IPMs. Upgrades can be made directly or using adapter boards with driver circuitry (connected via springs). Semikron's SKYPER™ drivers are ideal for this purpose. Integrated Subsystems What all these IPMs have in common is true "intelligence"—the controller that converts the setpoint value into a sequence of drive pulses is not included in the module. Semikron is a core manufacturer of integrated subsystems for converters below 250kW. The SKAI™ module is also an IPM, characterized by its integrated DSP controller, which can perform other communication tasks besides pulse width modulation. These subsystems also include an integrated DC link capacitor, an auxiliary power supply, a precision current sensor, and a liquid cooler. Figure 3 shows the block diagram of the integrated functions. Figure 3: Block diagram showing the integrated functions in the SKAI™ module. New Packaging Trends Current goals in power electronics development are to achieve higher current density, system integration, and higher reliability. At the same time, there is a growing demand for lower costs, standard interfaces, and flexible and modular product families. Figure 4 shows the progress made in module weight and size over the past few years. To illustrate this progress, two modules with the same power rating are shown. Figure 4: Reduction in the size and weight of modern power semiconductors. A further trend observed in this area is the use of spring connections for auxiliary and load connections. Semikron's MiniSKiiP® series is a pioneer in this area. In the MiniSKiiP® module, every auxiliary and load connection to the converter PCB is spring-loaded. New Generation Chips in Use Improvements in semiconductor technology have driven the development of thinner, better-structured semiconductor chips. Over the past few years, this advancement has increased the current density of 1200V IGBT chips from 40 A/cm² to 120 A/cm². However, wafer technology also has its limitations, as illustrated by the fact that for the latest 600V trench IGBTs (70 µm thick), the allowable short-circuit time has decreased from 10 µs to a maximum of 6 µs. This is because the thinner the silicon wafer, the lower its thermal capacity. Higher Operating Temperatures Higher operating temperatures are required in many fields, such as automotive applications where engine compartment temperatures commonly exceed 130°C, and coolant temperatures reach 105°C or even higher. The only way to achieve the higher current densities and higher ambient temperatures required for these applications is to increase the maximum allowable chip temperature. Thanks to advancements in the semiconductor industry, this is now possible. In 2005, the maximum allowable chip temperature for 600 V IGBTs and freewheeling diodes increased by 25°C to 175°C. Currently, the latest generation of 1200 V IGBTs is being tested at Tvj = 175°C. However, higher operating temperatures and current densities also negatively impact reliability, particularly in terms of load cycling capability, leading to solder joint fatigue and bond wire disconnection [1]. One possible solution is to sinter the semiconductor components with the DCB substrate. Due to their lower thermal resistance and high reliability, the sintering process can help further increase current density and operating temperature. The sintering process involves applying high pressure to silver powder at a temperature of approximately 240°C to create a thin interconnect layer between components that provides a reliable connection [2, 3]. Conclusion Power semiconductors contribute to the development of the electronics industry, especially in the alternative energy sector and the electric and hybrid vehicle market, where they have experienced above-average growth rates. Several trends can be observed in the development of power electronic modules, the most important of which are system integration, optimization of cooling systems, increased current density, and reduced costs. The only way to address future challenges related to higher operating temperatures and associated reliability issues is to continue developing and optimizing assembly and connection technologies. 4. Literature [1] U. Scheuermann, U. Hecht: Power Cycling Lifetime of Advanced Power Modules for Different Temperature Swings, PCIM, Nürnberg 2002 [2] U. Scheuermann, P. Wiedl: Low temperature joining technology a high reliability alternative to solder contacts, Workshop on metal ceramics composites for function applications, Wien, 1997 [3] R. Arno, J. Lutz, et al: Double-Sided Low-Temperature Joining Technique for Power Cycling Capability at High Temperature, EPE, Dresden, 2005