Thermal stability and characteristic properties of pressureless sintered Ag layers formed with Ag nanoparticles for powe
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Thermal stability and characteristic properties of pressureless sintered Ag layers formed with Ag nanoparticles for power device applications Tomofumi Watanabe1, Masafumi Takesue1,* Akio Hirose2 1 2
, Tomoki Matsuda2, Tomokazu Sano2, and
Engineering Department, New Business Promotion Center, Bando Chemical Industries, Ltd, Kobe, Japan Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, Suita, Japan
Received: 1 June 2020
ABSTRACT
Accepted: 14 August 2020
Thermal stability and characteristic properties of the microstructure of sintered Ag layers were examined with morphological, crystallographic and mechanical analyses. The sintered Ag layer was prepared by a pressureless sintering procedure with an Ag paste including Ag nanoparticles having a diameter distribution of 50–300 nm. The microstructure of the sintered Ag had a porosity of 8% and was morphologically and crystallographically dense. Cross-sectional SEM images showed that pores having a diameter of 0.2–1.0 lm were homogenously located in an Ag matrix. The dense microstructure remained intact after storage at 250 °C and for 1000 h. Shear strength of the sintered Ag layers was over 40 MPa and elastic modulus of the sintered Ag layer was 14 GPa before and after the storage tests at 250 °C and for 1000 h.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
1 Introduction Sintered Ag materials are being widely used as dieattachment materials for semiconductor devices in high-power electronics and optoelectronics because of their reliability and high thermal conductivity. The market has exploited sintered Ag materials not only as a Pb-free die-attachment material, but also as a new die-attachment material that can endure high junction temperatures. Conventional Si-based semiconductor dies in high-power electronics are being driven at junction temperatures of 125–175 °C. Junction temperatures of wide bandgap semiconductors
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https://doi.org/10.1007/s10854-020-04265-y
like SiC and GaN replacing Si are expected to exceed 200 °C in the near future [1, 2]. It is generally thought that a conventional die-attachment material such as Pb solder can no longer be useable at the junction temperatures of over 175 °C. According to the increasing junction temperature of semiconductor dies, sintered Ag materials are expected to be exposed to thermal environments exceeding 200 °C or more for long periods of time. In view of the technology and equipment, sintering processes in device production with sintered Ag materials can be divided into two categories: (i) pressure-assisted sintered Ag layers and (ii)
J Mater Sci: Mater Electron
pressureless sintered Ag layers [3–5]. Pressure-assisted process, which has been already applied to the market over the last decade, is generally conducted with Ag pastes including mainly micron-sized Ag particles [5, 6]. On the other hand, pressureless sintering process takes advantages in avoiding the capital invest
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