We have fabricated an MEMS Rogowski coil current sensor with TSV structural wiring for overcurrent detection in power devices (device size: 10 × 10 × 0.3 mm³). The device is composed of a Rogowski coil consisting of a TSV structure current terminal with multi-TSV (11 × 11) for conducting current up and down the device, and a TSV structure wiring for detecting the current flowing through the current terminal. This device has a 137 turn spiral current sensing coil (via diameter: 100 μm). When the TSV current terminal was energized with a device using a high resistivity silicon substrate (>10,000 Ωcm), stable current detection was achieved.

The increasing demand for electric cars, which is part of the rapid progress toward a decarbonized society, has created the need for a reduction in the size and weight of high-output drive systems. Miniaturization requires a power module that efficiently dissipates the heat generated from power semiconductors. We have developed a direct water and double side cooled power module that efficiently transfers heat from both sides of the power semiconductor without passing through thermal grease. In doing so, the power density of the inverter was increased 1.6 times. In this report, in order to realize a power module structure that can be immersed in cooling water, the authors report on a bonding mounting technology that reliably attaches both sides of a power semiconductor to an aluminum CAN-shaped metal case. The developed technology has achieved approximately twice the reliability of conventional products and has been adopted in vehicles around the world.

Although progress has been made on algorithms to automate sensory inspection based on machine learning, there are several problems yet to be overcome. We have developed an on-line hammering sound inspection system for an automobile product. Since an upper limit is set on the inspection time (per part), a support vector machine method, which is able to compute quickly, is applied to the on-line inspection. The experimental results show that the accuracy of inspection reaches 99.8% within the specified processing time. This paper reports on the implementation of the hammering sound sampling process, the inspection model training process, and the instrumentation of inspection system.

We have developed a maintenance-free ultra-thin high withstand-voltage power source with a polarity inversion function for mounting on industrial equipment. To realize such a power source, we have developed a new process using Sn-3.0Ag-0.5Cu solder for joining low expansion coefficient flexible printed circuits (FPC) and the bare chips of switching devices. In this new joining process, we investigated the effects on the solder joining capability of highly volatile flux and of surface cleanliness with Sn-3.0Ag-0.5Cu solder on the FPC. We also developed a highly reliable solder joining process for fine and narrow gaps between the FPC and the bare chips. Based on this process, we experimentally manufactured an ultra-thin power source, and confirmed its high-withstand characteristics and its high-reliability.

Three-dimensional thermal fluid simulation is useful in research and development, improving the efficiency of power module thermal designs for front-loading development of power electronic systems. This paper reports on three-dimensional thermal fluid simulation modeling based on thermal transient measurement results and fatigue analysis for an structurally asymmetric, double-sided cooling, 2-in-1 power module with IGBT (Insulated Gate Bipolar Transistor) and FWD (Free Wheeling Diode). The model parameters are calibrated by structure functions extracted from measurement results of the IGBT embedded in the device under test. As an example of the fatigue analysis, solder delamination as a result of solder fatigue is evaluated using the calibrated model.

To improve the load characteristics of lithium-ion secondary batteries, a carbon material is used as the conductive additive in the positive as well as negative electrodes. To increase the capacity of the secondary battery, it is necessary to increase the capacity of the active anode material. Hence, studies on the use of silicon for the anode have been performed in various fields. In this context, we establish that the application of exfoliated graphene as the conductive additive is effective in improving the charge/discharge cycle characteristics compared to commonly used carbon materials, such as Ketjenblack and graphite. Exfoliated synthetic graphene produced using a biaxial, independently controlled three-dimensional rotary ball mill has a unique shape. In order to uniformly disperse it in the electrode, while maintaining a flake shape thinner than graphene, we developed a dispersion technology using a wet process that utilizes a homogenizer and a jet mill. Although the resistance component of the electrode synthesized by mixing exfoliated graphene with powdered silicon is greater than that of the other carbon materials, it is considered advantageous as a conductive additive because it ensures physical contact with the active material, even when the anode matrix disintegrates due to the rapid volume changes in silicon caused by repeated charge/discharge cycles.

Physical contact optical connectors (PC) maintain long-term stability by keeping the contact of the optical fiber even if temperature fluctuations cause microscopic deformation of the ferrule endface. With multicore fibers (MCF), it is necessary to reexamine how to maintain the stable PC connection, because they have cores in addition to the center. We ran a finite element analysis of the microscopic deformations of ferrule endfaces on 4-core MCFs with standard outer diameters. From the microscopic deformation analysis of optical connectors with apex offset and fiber withdrawal under IEC61755-3-1 and IEC61753-1 Category OP+^HD conditions, all endface conditions were confirmed. For ferrule endface conditions with the standard outer diameter 4-core MCF mentioned above, with a radius of curvature 15 mm or more, it was confirmed that the connection is stable under standard conditions.