Eiji Mochizuki

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.

All lead free IGBT module with excellent reliability

The subject of lead free solder application of IGBT module is reliability of solder under the insulated substrate in temperature cycling test. This paper presents all lead free IGBT modules with excellent reliability. This was achieved by optimizing of the thermal expansion coefficient of insulated substrate and using Sn-Ag-In solder.

Novel IGBT module design, material and reliability technology for 175°C continuous operation

One solution for increasing output power in general purpose inverters is raising the operation temperature of Insulated Gate Bipolar Transistor (IGBT) modules by junction max temperature (Tjmax) =175°C against conventional Tjmax=150°C. However, the main problem for Tjmax=175°C operation is decreased the power cycling (P/C) capability caused by higher temperature. In this paper, we investigated the failure mechanisms of P/C test at Tjmax=175°C. From these detailed investigations, the failure modes of IGBT module are dominated by three joint parts under three categorized temperature regions. By using these results, we have developed three new technologies to achieve higher P/C capability: (a) New Al alloy bonding wire with higher fatigue capability, (b) High strength solder at high temperature, (c) New die electrode metallization with higher strength under high temperature and lower thermal stress between Si die and Al wire. With these technologies, our new IGBT module has the excellent P/C capability of continuous operation at Tjmax=175°C and longer lifetime compared with the conventional one.

Investigations of all lead free IGBT module structure with low thermal resistance and high reliability

This paper presents all lead free IGBT module structure with low thermal resistance and high reliability. Using thick copper foil alumina DCB, Sn/Ag/In solder, and copper base, we have achieved low thermal resistance as same as the current aluminum nitride (AlN) IGBT module structure. In addition to low thermal resistance, this new structure shows excellent temperature cycling capability of 3000 cycles

Influence of Cooling Rates on Reliability of Solder Joints Using Sn–13wt.% Sb Binary Alloy for Power Semiconductor Modules

Power semiconductor devices for electric power conversion are operated at high temperatures and must exhibit high reliability. Therefore, high heat resistance and long fatigue lifetimes are necessary for the solder joints in these devices. In this paper, we discuss how the thermal cycling lifetimes of solder joints using Sn-13wt.% Sb binary alloys with supersaturated antimony are affected by the cooling rates. These alloys exhibit good high temperature properties and mechanical properties. We conducted tensile tests and low-cycle fatigue tests to investigate the influence of the cooling rates on the reliability of solder joints using Sn-13wt.% Sb alloy. Our study clarified that the tensile strength of the Sn-13wt.% Sb alloy deteriorates and the low-cycle fatigue lifetime increases as the cooling rate becomes slow. Furthermore, the size of the SbSn intermetallic compounds (SbSn IMCs) precipitated in the

Higher thermal cycling reliability of power semiconductor module for power converters

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Next-generation IGBT module structure for hybrid vehicle with high cooling performance and high temperature operation

-Sn matrix tends to become coarse with the slowing cooling rate. From these results, we infer that the mechanism of extending the fatigue lifetime by slowing the cooling rate is that coarsened hard SbSn IMCs act as obstructions to solder crack propagation and the path of the crack propagation is lengthened. It became clear that the lifetime of Sn-13wt.% Sb binary alloy can be prolonged by controlling the cooling rate. We conclude that the strengthening mechanism of Sn-13wt.% Sb binary alloys is described by the strengthening model of a particle-dispersed composite material.

Improving reliability of IGBT surface electrode for 200 °C operation

Power semiconductor devices for electric power conversion must be highly efficient, compact, and with large capacity. Therefore, highly thermo stability and long fatigue lifetime are necessary for the joint materials of these devices. In this paper, we discuss the joint reliability obtained by applying the supersaturated Sn-13wt. % Sb binary alloy. Through this process, the joint materials achieve a thermo stable up to 175 °C or more. Thus, they can be used in wide-bandgap semiconductors to join the ceramic substrate with the heat sink. Finally, we examine the new material properties (tensile and low cycling fatigue). The thermal cycling lifetime of supersaturated Sn-Sb joints is significantly affected by the materials microstructure; when its crystal grains are large, the material has a longer lifetime. Consequently, in SbSn compounds, which crystallize in the β-Sn matrix, solder crack propagation can be prevented when the compound is large enough; there is a mechanism that suppresses the propagation speed of the crack. In addition, the supersaturated Sn-13wt. %Sb binary alloy is also resistant up to 150 °C, above the higher temperature at which the joints are exposed to. Therefore, this application can ensure high reliability for the high temperature operating devices, which operate at 175 °C temperature or higher.

SOLDERING METHOD AND METHOD OF MANUFACTURING SEMICONDUCTOR DEVICE INCLUDING SOLDERING METHOD

We developed a new technology for the Fuji 4th generation power module for hybrid vehicle application. It achieved a 30-% volume reduction, and a 33-% weight reduction compared to the 3rd generation. Requirement trends for the power module for hybrid vehicles are high energy-efficient, downsizing, lightweight and higher reliability. To achieve these requirements, IGBT module needs low thermal resistance and high operating temperature. We developed new technologies, 1) New cooling structure with high cooling performance. 2) The Tjmax.=175°C continuous operation with automotive required quality.

Semiconductor device with lead frame including conductor plates arranged three-dimensionally

The surface barrier effect due to nickel (Ni) film on aluminum (Al) surface electrode of insulated gate bipolar transistor (IGBT) via power cycling (P/C) test at the maximal junction temperature (Tjmax) of 200°C and thermal cycling (T/C) test in the -55°C to 200°C range has been carefully investigated. The difference of coefficient of thermal expansion (CTE) between Al and Ni and the stiffness of Ni played a key role to prevent mass transfer phenomena such as a migration of Al grain boundaries. We show that long P/C and T/C lifetime under high temperature operating condition can be achieved with the conventional IGBT module using our technique.