In order to take the full advantage of the high-temperature SiC and GaN operating devices, package materials able to withstand high-temperature storage and large thermal cycles have been investigated. The temperature under consideration here are higher than 200 °C. Such temperatures are required for several potential applications such as down-hole oil and gas industry for well logging, aircrafts, automotive, and space exploration. This review focuses on the reliability of a selection of potential components or materials used in the package assembly as the substrates, the die attaches, the interconnections, and the encapsulation materials. It reveals that, substrates with low coefficient of thermal expansion (CTE) conductors or with higher fracture resistant ceramics are potential candidates for high temperatures. Die attaches and interconnections reliable solutions are also available with the use of compatible metallization schemes. At this level, the reliability can also be improved by reducing the CTE mismatch between assembled materials. The encapsulation remains the most limiting packaging component since hard materials present thermomechanical reliability issues, while soft materials have low degradation temperatures. The review allows identifying reliable components and materials for high-temperature wide bandgap semiconductors and is expected to be very useful for researchers working for the development on high-temperature electronics.

Survey of High-Temperature Reliability of Power Electronics Packaging Components

In this paper, a high-temperature, high-frequency, wire-bond-based multichip phase-leg module was designed, fabricated, and fully tested. Using paralleled Silicon Carbide (SiC) MOSFETs, the module was rated at 1200 V and 60 A, and was designed for a 25-kW three-phase inverter operating at a switching frequency of 70 kHz, and in a harsh environment up to 200 °C, for aircraft applications. To this end, the temperature-dependent characteristics of the SiC MOSFET were first evaluated. The results demonstrated the superiority of the SiC MOSFET in both static and switching performances compared to Si devices, but meanwhile did reveal the design tradeoff in terms of the device's gate oxide stability. Various high-temperature packaging materials were then extensively surveyed and carefully selected for the module to sustain the harsh environment. The electrical layout of the module was also optimized using a modeling and simulation approach, in order to minimize the device parasitic ringing during high-speed switching. Finally, the static and switching performances of the fabricated module were tested, and the 200 °C continuous operation of the SiC MOSFETs was verified.

A 1200-V, 60-A SiC MOSFET Multichip Phase-Leg Module for High-Temperature, High-Frequency Applications

Characterization and Modeling of High-Switching-Speed Behavior of SiC Active Devices

Soldering has been the main die attach technology for several decades. Recently, in order to meet the high temperature electronic requirements (high temperature-operating SiC and GaN devices) as well as the health recommendations (replacing the toxic lead present in common solder alloys with lead-free alternatives), several new attach technologies have been developed. Among others, the sintering of nano-silver particles seems to be one of the most interesting choices, and has been extensively investigated during recent years. The emergence of this technology is mainly due to the desired high electrical and high thermal conductivities of the sintered joint, its low elastic modulus offering a good thermo-mechanical reliability, its low process temperature, and its high operating temperature. In this paper, a review of parameters affecting the initial shear strength of the sintered silver joint will be summarized as well as the high temperature long-term reliability issues. The sintering cycle (bonding pressure, bonding temperature, sintering dwell time, heating rate, and the sintering atmosphere), the joint size, and the attached materials properties (nature, roughness), are found to closely affect the initially measured shear strength of the joint. The long-term reliability of the joint has been shown to suffer initially from three phenomena: the silver electro-migration, the decrease of shear strength under harsh thermo-mechanical stresses, and the swelling of the sintered layer. While the latter phenomenon is observed during the storage at temperatures above 350°C, the electro-migration and thermo-mechanical stresses can influence the package reliability at temperatures as low as 250°C. However, some suggested precautions during the module fabrication can lead to the minimizing of the effects of these phenomena and the achievem a more reliable joint.

Review on Joint Shear Strength of Nano-Silver Paste and Its Long-Term High Temperature Reliability

Enhanced material properties of silicon carbide (SiC) offer improved performance capabilities for power electronic devices compared to traditional silicon (Si) components. This paper reports on the experimental characterization of a 1200-V, 800-A all-SiC dual power module that incorporates twenty 80-A SiC MOSFETs and twenty 50-A SiC junction barrier Schottky diodes. Forward and reverse conduction characteristics were measured at multiple gate voltages, current sharing was examined between the MOSFETs, and switching energies were calculated for various currents. Additionally, this module has operated in a full-bridge circuit with a peak loading of 900 Adc, a 600 Vdc bus, and a junction temperatures of 153°C. From the experimental data, a model of the module was created and used in a dc-ac inverter simulation study to demonstrate the possible benefits of SiC compared to Si technology. The use of an all-SiC module was shown to reduce inverter losses by 40% or more for most operating conditions. Furthermore, for similar output current levels, the all-SiC module can operate at switching frequencies four times higher than that of the Si module. This advanced dual power module demonstrates the ability to produce a high-current high-power switch using SiC technology.

Evaluation of a 1200-V, 800-A All-SiC Dual Module

In order to take full advantage of SiC, a high-temperature wirebond package for multichip phase-leg power module using SiC devices was designed, developed, fabricated, and tested. The details of the material comparison and selection are described, thus culminating a feasible solution for high-temperature operation. A thermal cycling test with large temperature excursion (from -55°C to 250°C) was carried out to evaluate the thermomechanical reliability of the package. During the test, the substrate failed before other parts in 20 cycles. A sealing edge approach was proposed to improve the thermal reliability of the substrate. With the strengthening of the sealing material, the substrate, die-attachment, and wirebond assemblies exhibited satisfactoriness in the thermomechanical reliability tests. In order to evaluate the high-temperature operation ability of designed package, one prototype module was designed and fabricated. The high-temperature continuous power test shows that the package presented in this paper can perform well at 250°C junction temperature.

SiC Wirebond Multichip Phase-Leg Module Packaging Design and Testing for Harsh Environment

In order to take full advantage of SiC, a high temperature wirebond package for multi-chip phase-leg power module using SiC devices was designed, developed, fabricated and tested. The details of the material selection and thermo-mechanical reliability evaluation are described. High temperature power test shows that the package presented in this paper can perform well at the high junction temperature.

SiC Wirebond Multi-Chip Phase-Leg Module Packaging Design and Testing for Harsh Environment

This paper describes a wireless-bond interconnect technique, termed Dimple-Array Interconnect (DAI) technique for packaging power devices. Electrical connections onto the devices are established by soldering arrays of dimples pre-formed on a metal sheet. Preliminary experimental and analytical results demonstrated potential advantages of this technique such as reduced parasitic noises, improved heat dissipation, as well as lowered processing complexity, compared to the conventional wire bonding technology in power module manufacturing. Thermomechanical analysis using thermal cycling test and FEM were also performed to evaluate the reliability characteristics of this interconnect technique for power devices.

http://www.initkms.ru/umk/etf/d/A_dimple-array_interconnect_technique_for_power_semiconductor_devices_(Wen_S.S.,_Huff_D.,_Lu_G.-Q.).pdf

Daniel Huff

Papers

SiC Wirebond Multichip Phase-Leg Module Packaging Design and Testing for Harsh Environment

SiC Wirebond Multi-Chip Phase-Leg Module Packaging Design and Testing for Harsh Environment

A Dimple-Array Interconnect Technique for Power Semiconductor Devices

250 °C SiC Power Module Package Design