A new method for liquid-phase bonding of copper plates to aluminum nitride (AlN) substrates used in high-power modules

A new method for liquid-phase bonding of copper plates to an aluminum nitride (AlN) substrate was developed in this work. A newly developed proprietary interlayer composed of titanium and silver powders was deposited on the AlN substrate using a screen-printing machine. The eutectic reaction between printed silver and copper at 850 °C led to formation of a liquid phase at the joint interface. A total of 42 samples were prepared using seven and six different amounts of silver and titanium, respectively. The microstructures of all samples were analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy, and an ultrasonic flaw detector was used to assess joint integrity. The optimum composition of the Ti–Ag brazing alloy for producing defect-free joints was determined. The formation of a continuous titanium nitride layer was found to be essential for achieving sound joints between the copper plates and AlN substrate

Structural and electrical characterization of electro spray deposited PZT sol-PZT nanopowder composite thick films

In piezoelectric market, infrared detectors, pyroelectric and piezoelectric sensors, microwave devices, actuators, transducers, non-volatile random access memories, and micro electromechanical systems are fabricated using lead zirconate titanate (PZT) based films. These films are deposited by chemical vapor deposition, physical vapor deposition spin coating, screen printing and electrospray deposition (ESD) technique. Among them, ESD is the most preferred method because of its high material efficiency, simplicity of experimental set up, wide choice of precursor and low cost. Therefore, the purpose of this study is to fabricate and characterize the ESD deposited PZT films. In our study, Pb(Zr0.Ti-52(0.48))O-3 (PZT) nano powders (Nanotech Corp. Turkey) and MMC PZT sol (Mitsubishi Corp. Japan) combinations were mixed in various concentrations. Prepared composite PZT slurries were coated with ESD technique. Fabricated PZT thick films were characterized with scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction method (XRD) to evaluate surface and crystal structure of the films. The results show that, MMC sol and PZT nanopowder combinations provide smooth and homogeneous film surface., dense and non-cracked film microstructure was observed using excess PbO during sintering

Thermal expansion of coefficient and working temperature of Sro-ZnO-P2_2O5_5 glasses

The glass forming region in the ternary system SrO-ZnO-P$_2$O$_5$ has been determined. Thermal expansion of coefficient ($alpha$) and working temperature ($T_w$) of SrO-ZnO-P$_2$O$_5$ glasses have been measured. Compositional dependencies of these properties have been investigated. The variations of $alpha$ and $T_w$ were depended on ZnO content. The $alpha$ of the glasses decreased linearly with increasing ZnO content. The $T_w$ of the glasses increased linearly with increasing ZnO content. The features of Zn phosphate glass (${\rm ZnO}/{\rm P}_2{\rm O}_5 < 0.25$), that is low $alpha$, are related to the small oxygen coordination number of the cations (=4). The 50ZnO-10SrO-40P$_2$O$_5$ glass was found to have $T_w$ (520$^circ$C) and it was tailored to match the $alpha$ f PDP glass substrate $85 \times 10^{-7} {}^circ{\rm C}^{-1}$. The glass would be useful in a practical application for PDP glasses

SrO-ZnO-P2_2O5_5系ガラスの熱膨張係数と作業温度

The glass forming region in the ternary system SrO-ZnO-P$_2$O$_5$ has been determined. Thermal expansion of coefficient ($alpha$) and working temperature ($T_w$) of SrO-ZnO-P$_2$O$_5$ glasses have been measured. Compositional dependencies of these properties have been investigated. The variations of $alpha$ and $T_w$ were depended on ZnO content. The $alpha$ of the glasses decreased linearly with increasing ZnO content. The $T_w$ of the glasses increased linearly with increasing ZnO content. The features of Zn phosphate glass (${\rm ZnO}/{\rm P}_2{\rm O}_5 < 0.25$), that is low $alpha$, are related to the small oxygen coordination number of the cations (=4). The 50ZnO-10SrO-40P$_2$O$_5$ glass was found to have $T_w$ (520$^circ$C) and it was tailored to match the $alpha$ f PDP glass substrate $85 \times 10^{-7} {}^circ{\rm C}^{-1}$. The glass would be useful in a practical application for PDP glasses