L.C. Tsao

Effect of TiO2 nanoparticles on the microstructure and bonding strengths of Sn0.7Cu composite solder BGA packages with immersion Sn surface finish

This study investigated the effects of TiO2 nanoparticles on the interfacial microstructures and bonding strength of Sn0.7Cu (SC) composite solder joints in ball grid array packages with immersion Sn surface finishes. The addition of TiO2 nanoparticles to SC solders resulted in significant changes in the interfacial microstructure. The nanoparticle addition suppressed the growth of the Cu6Sn5 IMC layer, significantly improving shear strength and reliability of solder joints after multiple reflows. The fracture surfaces of the SC solder exhibited a semi-brittle fracture mode with a relatively smooth surface, while those of the SC composite solder showed typical ductile failures with very refined dimpled surfaces.

Direct robust active bonding between Al heat sink and Si substrate

In the study, the direct robust active bonding (DRAB) between Si chip and Al heat sink by using of low melting point Sn-Ag-Ti (SAT) active solder is obtained at 250°C in air. The bonding process was done without flux and without the need for pre-metallization of Al heat sink or a protective atmosphere. The bonded joints were studied using SEM and the distribution of elements using energy-dispersive x-ray (EDX) analysis. The results revealed that SAT active solder Si could be directly bonded with Si and Al, and the bonding strength of Si/Al bonding was 7.9 ±1.1MPa. A new Sn-Ag-Al phase has been formed at the solder/Al interfaces around. Such direct robust active bonding could be useful for 3D-chip and high powder CPU packaging.

Water Tank Simulation of a Continuous Hot-Dip Galvanized Zinc Pot

This work has simulated the flow field in a hot-dip galvanized zinc pot using a water tank simulation. The flow pattern was visualized using laser sheet flow visualization technique. The general flow pattern in the water tank was not sufficiently influenced by the belt speed. The traces of water on the snout side, in the snout region, and close to the surface, where the stabilizing roll and the belt were in contact, were closely examined. The water tank was also investigated numerically. The steady-state CFD solution also indicated that a change in the belt velocity has little influence on the overall flow pattern developed in the tank. The flow patterns obtained via CFD means had a close resemblance with those visualized through laser sheet technique.

Influence of Cu addition on the structures and properties of Ti15SnxCu alloys

ABSTRACT In this study, Ti15SnxCu alloys were synthesised using an argon-arc melting and casting method. The as-cast alloy ingot was heat-treated for 2 h at 1000°C and then quenched in water to investigate the effects of heat treatment on the microstructure and corrosion behaviour of the Ti15SnxCu alloys. In comparison to the heat-treated Ti15Sn alloy, the average size of cellular grains (dG), the lamellar length (λL), and the lamellar thickness (λT) in heat-treated Ti15Sn2Cu alloy were refined by approximately 36, 30, and 36%, respectively. The corrosion behaviour of heat-treated Ti15SnxCu alloys was made nobler by adding 2 wt-% Cu content. The precipitation of large amounts of nobler (Ti, Sn)2Cu nanoparticles hindered grain growth, improved the UTS, 0.2YS, microhardness and good corrosion resistance.

Suppressing effect of 1 wt.% nano-TiO 2 addition into low Ag content Sn-Ag-Cu solder alloy on the intermetallic growth with Cu substrate during isothermal aging

This study investigated the effects of adding 1 wt.% nano-TiO2 particles into low-Ag content Sn0.35Ag0.7Cu (SAC) lead-free solder alloys on the growth of intermetallic compounds (IMC) with Cu substrates during solid-state isothermal aging at temperatures of 125, 150, and 175°C for up to 7 days. The results indicate that the morphology of the Cu6Sn5 phase transformed from scallop-type to layer-type in low-Ag SAC composite solder/Cu joints. The growth rate of these IMCs increased with the aging temperature and time. Kinetics analyses showed that growth of the overall IMC layers was diffusion controlled. The apparent activation energies for the growth of overall IMC layers are calculated to be 50.62 kJ/mol.

Influence of nano-TiO 2 reinforcements on the wettability and interfacial reactions of novel lead-free Sn3.5AgO.5Zn composite solder/Cu solder joints

The influences of intermixing nano-Ti02 particles on the wettability and interfacial reaction of novel lead-free Sn3.5Ago.5Zn composite solder with Cu substrate were investigated. The wettability of the Sn3.5Ag0.5Zn composite solder alloy was measured by the sessile-drop method under a 10−3 Torr vacuum at different temperature up to 30 mins. Scanning electron microscopy (SEM) was used to quantify the interfacial microstructure for each processing condition. The continuous scallop-type Cu6Sn5 IMC layer was still the only original product at the SAZ solder/Cu and SAZ composite solder/Cu interface at temperature 300 °C. However, a new flat-type QisZrig IMC layer was formed at the Cu6Sn5/Cu interface at temperature 325 °C. The addition of nano-Tio2 particles to the SAZ solder effectively improved in wetting property and corresponding suppressed the growth of the IMC layer at the interface.