Sn-Pb solder alloys, widely used in electronic industry, will be restricted because of the toxicity of Pb. That is paramount importance that developing viable alternative lead-free solders for electronic assemblies. Sn-Ag-Cu alloys are better alternative because of its good performance. But they have a melting temperature of 217-225°C that is much higher than that of Sn-Pb eutectic alloy, 183°C. It may be very difficulty to realize industrialization. Sn-Ag-Cu-Ga solder alloys have been studied in this paper, including a series of properties tests, such as melting point, hardness, shear strength and solderability. The best composition of Sn-Ag-Cu-Ga lead-free solder alloy has been obtained.

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In this work, the interface reaction between Al2O3 ceramic and Ag70.5Cu27.5Ti2 brazing filler metal at 845-860°C was investigated. Based on the data of thermodynamics and kinetics, the Gibbs free energies of the main interface reactions in the real brazing system condition were calculated. But the values of normal equilibrium reaction condition and the real interface reaction brazing system were different; and the main influential factor was the brazing temperature, and the system vacuum of brazing condition can lead the change of equilibrium constant (Kα). The results revealed that the high temperature and vacuum active brazing is a non-equilibrium interface reaction especially to titanium alloy, the vacuum and alloy liquid solution are beneficial to the brazing process, and the by-product formation of titanium-oxygen are affected by the diffusion process.

The green tapes of Al 2 O 3 /glass composite were prepared by tape casting process using poly methyl methacrylate (PMMA) as a binder. The results show that the slurry for tape casting exhibits a typical shear thinning behavior. The best pyrolysis procedure was found in nitrogen atmosphere to a maximum temperature of 600°C. The dielectric constants are between 4.6 and 7.3 depending on the glass content. The dissipation factors are about 0.2 % in the frequency range from 1 KHz to 1 MHz. The green tapes using PMMA as a binder can be sintered in nitrogen atmosphere for LTCC/Cu multilayer ceramic substrate.

In this paper, three types of Al2O3 powders with different sizes (1.6μm, 0.7μm, and 0.3μm) were used in a LTCC system of Al2O3 and borosilicate glass (BSG). Al2O3 and BSG are selected on account of their coefficient of thermal expansion (CTE) similar to silicon, which can reduce thermal stress. It was found that the dielectric constant, ε, of substrates drops with the decrease of Al2O3 powder size. ε increases with the increase of Al2O3 content for the sample with 1.6 μm Al2O3 powder, but decreases with the increase of Al2O3 content for the samples with 0.7 μm and 0.3 μm Al2O3 powders. SEM observations revealed that more pores with low permittivity appeared for the samples with smaller Al2O3 powders, resulting in the drop of dielectric constant of the sample finally.