| Summary: | 碩士 === 國立交通大學 === 材料科學與工程學系所 === 106 === Direct bonded copper (DBC) substrates have been widely used in power electronics and insulated gate bipolar transistors (IGBT) modules. However, poor thermal cycling reliability of DBC substrates restrict its applications. Direct bonded aluminum (DBA) substrates have been developed to replace DBC substrates due to its superior reliability. Previous studies used the silicon, germanium, silver, and copper as the interlayer to prepare DBA substrates. In this study, the Ni was selected and various thickness of nickel (100 nm、300 nm、500 nm) has been deposited on the Al2O3 substrate as the interlayer to join Al substrate by electron-beam evaporation. The specimens were then annealed at Al-Ni eutectic temperature (640℃) in argon atmosphere, the eutectic liquid phase formed at Al/Al2O3 interface to obtain better wettability. The purpose of present study is to analyze the microstructure of Al/Al2O3 contact by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Furthermore, scanning acoustic tomography (SAT) is used to reveal the voids distribution of Al/Al2O3 bonding layer for the purpose of evaluating the quality of DBA substrate. After joining of Al to Al2O3 with various thickness of nickel interlayers, Al3Ni phase were observed in the aluminum layer. The interfacial strength of Al/Al2O3 interfaces was measured by the shear strength test. The thermal conductivity of the sandwich (Al2O3/Al/Al2O3) specimens were measured by laser flash method. The resistivity of the aluminum layer with Al3Ni which was measured by four point probe. The results indicated that the interfacial strength of Al/Al2O3 interfaces and thermal conductivity of DBA substrates increased with the thickness of nickel interlayer increasing. The best thermal conductivity and shear strength of DBA specimens with 500 nm nickel interlayer was about 37 Wm-1K-1 and 31.5 MPa, respectively. In addition, comparing with the initial aluminum foil, the resistivity of aluminum layer with Al3Ni which was formed after Al/Al2O3 joint decreased insufficiently.
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