Yoshinari Ikeda

Full SiC power module with advanced structure and its solar inverter application

This paper describes advanced power module structure for high power and high frequency application with solar inverter system. This advanced power modules is applied full SiC semiconductor which has SiC MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) and SiC SBD (Schottky Barrier Diode). This full SiC power module structure realizes high reliability with low thermal impedance by using these new three technology, i) power circuit board which has copper pins connected to power devices, ii) advanced ceramic insulated substrate that enables high heat dissipation is utilized to reduce thermal impedance and iii) full molded package achieves high temperature operation and high reliability. The power cycling test at high temperature (200deg.C), electrical characteristics and inverter system efficiency of this full SiC power module were evaluated and compared with conventional Si power module. The results showed that the power cycling lifetime has x50 capability, electrical characteristics has low loss and low turn-off surge voltage, and 99.0% of efficiency at solar inverter system.

Investigation on wirebond-less power module structure with high-density packaging and high reliability

A newly developed module with wirebond-less structure is investigated. This structure has multi-pin attached interconnection structure implanted into power circuit board with connecting line between chips and other elements inside the power module. Additionally, heat-spreader-like copper blocks bonded to ceramic insulated substrates performing high thermal conductivity, enable to realize high current capability operations effectively. Moreover, full molded resin package performs higher reliability comparing with the conventional module, shows the package structure is one of the potential candidates of power module for the high power applications including Wide Band Gap (WBG) devices.

Ultra compact and high reliable SiC MOSFET power module with 200°C operating capability

Aluminium wirebond-less power module structure was investigated and presented in ISPSD 2011 [1]. The features of this structure are high-density packaging with Copper pins connection and power circuit board, low thermal resistance with thick Copper block on Silicon Nitride ceramic substrate and high reliability with epoxy resin moulding. This paper introduces Silicon Carbide MOSFET power module with this developed structure. High temperature operating capability up to 200°C is achieved with newly developed epoxy resin and Silver sintering technology. Low internal inductance is designed by laminating current paths to take an advantage of developed structure. SiC MOSFET 100A/1200V module was designed. Loss evaluation with this SiC module shows superior performance with SiC devices and also with developed structure.

Direct liquid cooling module with high reliability solder joining technology for automotive applications

We developed the direct-liquid-cooling IGBT module which enabled downsizing of a power control unit for HEV system and high reliability simultaneously. This module eliminates thermal grease by unifying a ceramic substrate and a heat sink. It contributes this module realized the reduction of thermal resistance 30 % compared to the conventional indirect liquid cooling type. High thermal conductive Si3N4 ceramics for the substrate and lightweight aluminum heat sink that are suitable for automotive use demand are applied. The technological challenge of this module is to overcome the decrease of the reliability of the joint by large CTE mismatch between substrate and heat sink. We developed the Sn-Sb based solder material which can attain high reliability for automotive use with large CTE mismatch components. And IGBT module with this new solder is applied to HEV.

All-SiC power module for photovoltaic Power Conditioner System

We developed the All-SiC power module for photovoltaic Power Conditioner System (PCS). The All-SiC module has SiC-MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and SiC-SBD (Schottky Barrier Diode) which are sandwiched between SiN (Silicon Nitride) substrate and power circuit board. Thick copper block which is attached SiN substrate enhances low thermal resistance and Cu pin which is connected power circuit board to semiconductor realizes high power density. Therefore, this new structural design achieves compact size of the All-SiC module. Module downsizing dramatically effects for module inductance property. Low inductance design enables high frequency switching with lower noise and lower switching loss. Furthermore, the developed epoxy resin structure is more reliable at high temperature than the conventional structure. At the result of the All-SiC development which is installed 20 kW photovoltaic PCS, 1/4 of volume downsizing and 99.0% of efficiency is achieved.

Ultra compact, low thermal impedance and high reliability module structure with SiC Schottky Barrier Diodes

An advanced module structure for taking advantage of superior characteristics of Silicon Carbide (SiC) device was researched and developed. This structure can realize about four times of power rating density and one half of thermal impedance compared to that of conventional structure. Also, this structure achieved to have higher reliability by applying epoxy molding structure and copper pin connection to conduct current to/from power chips instead of aluminum bonding wire.

Characteristics of the Power Electronics Equipments applying the SiC power devices

Power Electronics Equipments applying superior characteristics Silicon Carbide (SiC) power semiconductors have been researching and developing. Applying the hybrid modules using Si-IGBT and SiC-SBD (Schottky Barrier Diode) to the motor drive inverter enables reduction of the loss 25% of the inverter part. Moreover applying the All-SiC modules using SiC-MOSFET and SiC-SBD to the solar inverter enables to be the efficiency of the main circuit unit 99%, and to be the volume of the equipment 25% to conventional one.

A study on the reliability of the chip surface solder joint

The solder joint reliability of IGBT chip surface interconnection with a lead-frame structure is described in the power cycling (P/C) capability which is greatly improved due to a chip surface cooling effect in comparison with aluminum wire interconnection. The lead-frame is joined on a Ni and Au plated chip surface with Sn-Ag or Sn-Sb system solders. The P/C capability obtained with the Sn-Sb system solder is three times larger than that with the Sn-Ag system solder. Such a good performance comes from the solid solution hardening property of Sn-Sb system solder.

High accuracy partial discharge location in power module using multiple loop sensors

Existence of partial discharge (PD) is one of the key issues in high-voltage power module. Thus, identifying a PD location in a power module leads to a higher voltage operation of a power module. An attempt is made to identify PD location in an IGBT power module by measuring electromagnetic wave (EMW) detected by multiple loop sensors. In this paper, a novel technique for identification of PD source is proposed by utilizing the polarity reversal of the first rising part of detected EMW signals and Time of Flight (TOF) method with four loop sensors. As the result, it is found that the method utilizing the polarity reversal of EM waveform allows PD location with accuracy of 1 mm. And it is found that TOF method with sampling frequency of 80 GS/s allows PD location with accuracy of 1 mm.

Basic study on partial discharge location in power module

This paper deals with partial discharge (PD) location in a power module by measuring electromagnetic (EM) wave of PD using four loop sensors. As the distance between the sensor and PD source decreases, the peak to peak magnitude of the first wave of detected EM wave was found to increase using four sensors array. An attempt is made to locate PD source using output electromagnetic waves detected four loop sensors by the time of flight method. As a result, the present method is found to allow PD location with location identification error of 5 mm.