Expectations for the popularization of renewable energy such as solar and wind power, and for power electronics technologies enabling the efficient use of these energy sources have become extremely high., with the purpose of achieving a sustainable society In order to meet these expectations, Fuji Electric has been developing environment friendly power semiconductors with high energy conversion efficiency and low noise generation. Power semiconductors are utilized in numerous fields such as energy production, automobiles, industrial machinery, social infrastructure, and home electric appliances. In this special issue we present the latest technologies and products in power semiconductors, which are key devices of power electronics technologies.

Fuji Electric is expanding its energy-related businesses, which comprise "energy creation" for producing eco-friendly clean energy, "energy conservation" for realizing efficient use of energy, and "energy management" for connecting energy in an optimal style. The core of these businesses is power electronics and power semiconductors.
In regard to power semiconductors, this paper describes the current situation and outlook for power module products such as low-capacity IPMs for inverter air conditioners, 1,700V RB-IGBTs for multi-level power converters, direct cooling IGBT modules for automobiles, and All-Sic power module, and the component technologies to support these products, as well as 4th generation in-vehicle IPS devices and other power-discrete semiconductors, and power ICs such as LLC current resonant control ICs.

In a general trend to use highly efficient power converters, we are also observing a shift from conventional two-level converters toward multilevel converters of higher efficiency, in such applications as uninterruptible power supply (UPS) units and power conditioning system (PCS) units for solar power generation. Ahead of any other company, Fuji Electric has developed 1,700 V reverse-blocking insulated gate bipolar transistors (RB-IGBTs), used as bidirectional switches in multilevel converter circuits. For the 1,700 V device, we employed a hybrid isolation process that combines thermal diff usion and V-groove etching. When RB-IGBTs were used as neutral point clamping devices at a typical switching frequency for high-power inverters (up to 500 Hz), the decrease in conduction loss resulted in a reduction of energy loss by 18% in three-level inverters.

Next-generation power semiconductors such as silicon carbide (SiC) devices have the following superior features: high voltage tolerance, low loss and the capacity for high-frequency/high-temperature operation. In order to bring out the maximum potential of these features, we have developed a novel power module structure using copper pins to connect devices and using epoxy resin as a sealant. Through this structure, temperature cycle tolerance have been improved, and by using silver sintered materials, the high reliability of operation at 200 °C was verified. Moreover, by fully utilizing the features of the new structure, it is possible to design low-inductance SIC modules. By using prototype all-SiC modules, we achieved significant size reduction and effi ciency improvement of power conditioners for solar power generation.

With the expansion in use of renewable energy, the uses of insulated gate bipolar transistor (IGBT) module products have diversifi ed and there is a demand for higher reliability. Ensuring the quality and reliability of products requires specification of failure/degradation modes and reliability design based on failure mechanisms. To achieve high reliability, Fuji Electric is creating designs for thermal fatigue lifetime based on simulation of actual device, insulation lifetime through electric field simulation, and ultra-low temperature operation assurance. In addition, to achieve longer product life, we have developed ultrasonic welding of terminal and Sn-Sb soldering as packaging technologies. Furthermore, to ensure good heat dissipation under the conditions of use, we have investigated thermal grease.

To meet the various demands for insulated gate bipolar transistor (IGBT) module design such as miniaturization, high effi ciency, and low noise, the importance of preanalysis through simulation has increased. Heretofore, Fuji Electric has performed device and thermal simulations separately for each component of IGBT module; now we have linked these simulations with a circuit simulation as a base, and established an integrated simulation that enables analysis of the IGBT module as a whole. Through this we have improved the accuracy of simulations from approximately 40% to 10% for electrical properties and from approximately 10% to 5% for thermal properties, as compared to previous simulations.

In addition to the conventional “P630 package” that uses alumina insulating substrate, we have developed the high heat dissipation type “P630 package” that uses aluminum nitride. This new package reduces thermal resistance by more than 30% compared to the previous package and can suppress ΔT_j-c under high load conditions. In addition, by reassessing the use of insulating substrate solder materials, we have greatly improved ΔT power cycle capacity compared to the previous generation of intelligent power modules (IPMs) that used aluminum nitride and lead solder. The mechanical and electronic features and external form are the same as the conventional package, and the package is capable of various uses corresponding to load conditions and heat dissipation system design.

In recent years, there has been a rapid growth in the market for renewable energy, and the needs for high-capacity insulated gate bipolar transistor（IGBT） modules have expanded quickly. To answer these needs, Fuji Electric has arranged a new line of products that have a 25% higher current rating into 3.3 kV modules. These are 3.3 kV/1.0 kA products of the same package as 3.3 kV/0.8 kA devices, and 3.3 kV/1.5 kA products of the same package as 1.2 kA devices. By reappraising chip configuration and using a symmetric configuration, we can ensure high switching capacity. Also, to improve the heat-dissipation capability, we use an AlN substrate as the insulating substrate, and to ensure reliability, we use an AlSiC base plate as the base material.

Fuji Electric has been engaged design and development of insulated gate bipolar transistor (IGBT) modules for society to achieve energy efficiency in industrial machinery. These modules have a wide range of applications, and we have now developed a lineup of flexible power integrated modules (PIMs) for the purpose of increasing the efficiency and reducing the size and weight of low power devices (up to 50 A). For the IGBT free-wheeling diode (FWD), we have used the 6th generation “V series” and have reduced by 45% in footprint size and by 78% in weight by use of a copper baseless package. As for the pin terminal confi guration, customers can choose between press-fit pins and solder pins according to their needs.

We have developed a compact type intelligent power module (IPM) that achieves greater improvement of energy-saving performance for inverter air conditioners that meet energy-saving regulations, conformable to the annual performance factor (APF) specifi cations. By combining the insulated gate bipolar transistor (IGBT) of the field-stop type trench gate structure with high-speed free-wheeling diodes (FWDs), we have reduced loss during light-load operation, which is an important factor for air conditioners, by about 25%. Moreover, using an insulated metal substrate with high thermal conductivity reduces thermal resistance, thereby suppressing temperature rise by incorporating the effect by the loss-reduction. Moreover, the control circuits incorporate several protective features such as an overcurrent protection function, a temperature sensing function, and a low-voltage protection function.

Car manufacturers are proactively engaged in the development of hybrid vehicles and electric vehicles. To contribute to the miniaturization of in-car inverter units, Fuji Electric is developing insulated gate bipolar transistor (IGBT) modules that use direct water cooling. In addition, to support customers’ inverter developments, we have studied water cooling jacket structure for IGBT modules for use in automotive for realizing both high radiation performance and low pressure loss. Moreover, we have developed application technologies such as reliability design based on driving patterns of vehicles.

There is an increased demand for small, highly reliable, low-cost semiconductor devices in the automotive application. Accordingly, we have developed the 4th generation IPS “F5100 series” by changing the power metal-oxide-semiconductor field-effect transistor (MOSFET) in the output stage from a planar structure into a trench structure, as well as by employing minute circuits for control and protection circuits and applying multi metal layer technology. The product lineup contains 1-channel devices mounted in existing SOP- 8 packages and 2-channel devices of the same package size. These devices have the following four main features: short-circuit protection by functions of detecting overcurrent and overtemperature, low power-supply voltage operation, status signed output and high speed turn-off function for inductive load.

LLC current-resonant circuits have attracted attention as useful circuit systems for achieving a highly efficient, low-noise and thin structure of switching power supply; but there are problems that the power circuit scale becomes larger due to the need to include separate converters for stable operation. Fuji Electric has developed the LLC current-resonant control IC “FA5760N”, which can be used to construct an LLC current-resonant circuit with a single converter and which enables operation on low standby power. A 630 V high voltage driver and a 600 V start-up device are built into one chip. The new product gets rid of the problems with previous LLC current-resonant circuits by using protecting circuits and an intermittent operation mode to avoid the short circuit of the half- bridge circuit. This product is capable of a wide range of applications.

“FA8A00 series” is the 6th generation pulse width modulation (PWM) power supply control IC, which utilizes the newly developed 0.35 μm process technology. The package is a small outline package (SOP) 8-pin and builds in a 500 V-capable startup circuit. Through a newly developed X capacitor discharge function, the discharge resistance which was formerly necessary is reduced and about 20 mW of resistance losses are reduced. Furthermore, by reducing the IC current consumption to 30% of the conventional products, the standby power of a whole power supply is realized 30 mW or less. Moreover, through optimization of frequency reduction properties, the average efficiency realizes 89% or more. This can contribute to energy efficiency and cost reduction of power source systems.