Ju Sheng Ma

Fabrication and Properties of Lead-Free Sn-Ag-Cu-Ga Solder Alloy

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.

Dielectric Properties of LTCC System of Al2O3 and Borosilicate Glass

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.

Preparation and Sintering Behavior of Au Conductor Pastes for LTCC Substrate

Fine Au powders with spherical morphology and good dispersivity were produced. The average particle size is 1~2m. The influences of constituents on the rheology of organic vehicles were investigated by orthogonal design method. Consequently, the compatible Au thick film pastes for LTCC substrate have been prepared. SEM was carried out to study the sintering behaviors and microstructures of the buried pastes with LTCC substrate. These pastes have high electrical conductivity (less than 3m/sq.), reliable wire bond strength (greater than 9 grams, 25m Au wire) and fine line printability (as small as 80m). The via filling technology was also discussed in this paper.

Interface Reaction Thermodynamics of AgCuTi Brazing Filler Metal and Alumina Ceramic

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.

Preparation of Green Tapes for LTCC/Cu Multilayer Substrates

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.

New Material of Ni-Ti Alloy for Chip Tantalum Capacitor Fuse

With the wide application of SMT, mass chip components have been applied including tantalum capacitor. A fuse buried in a capacitor can protect the whole system of merit. In the paper a titanium nickel alloy with vanadium addition has been developed as a fuse material. Several alloy wires with different diameters have been used in the fusing experiment. The influencing factor have been discussed that a few factors including diameter, chucking and so on affect the fusing current. Analyses on the fuse wires have been investigated with SEM, XRF and XRD to measure the composition of alloy wires.

Properties of Electroless Nickel Composite Plating Film

The composite materials have been widely applied with fine reputations because the new materials have better physical properties and functions than the base materials. Especially in the fields in which the surface properties are important, the surface modification by this surface treatment technology is very significant.

Study on Thermal Shock Resistance of Insulated Metal Substrate

Anodizing technique was applied to prepare insulated metal substrates (IMS) for BGA packaging. “Ideal” IMS used anodic film of aluminum as the insulating layer instead of epoxy, which led to higher thermal conductivity. But the thermal shock resistance of IMS is poor because of the great difference of thermal expansion coefficient between aluminum and its anodic film. In this study, different anodizing processes of aluminum were analyzed. The parameters, which can affect the thermal shock resistance of IMS, especially the surface temperature of Al substrate, were studied. The anodic film obtained with the optimized parameters of anodizing process had excellent performance, such as the resistivity was over 1013Ω·cm, the breakdown voltage was higher than 600V, and the most important thing was that it could resist thermal shocks between room temperature and 300°C. Then BGA packaging was successfully performed based on this IMS.

Influence on Optical Properties of the New-Type Rear Projection Screen by the Content of Additive TiO2 Nano-Particle

Adding nano-particles with high refractive index can greatly improve the optical properties of the PMMA-based composites, which were developed as the new-type rear projection screen. In this paper, the influence on the optical properties, such as gain and view angle, by the content of additive TiO2 nano-particle was studied. Curves of optical properties versus content of nano-particle were obtained and the rational factors were found. Finally the reasons were discussed from the nanostructure point of view and the scattering principle.