Search results

1 – 2 of 2
To view the access options for this content please click here
Article
Publication date: 18 February 2019

Fen Peng, Wensheng Liu, Yufeng Huang, Siwei Tang, Chaoping Liang and Yunzhu Ma

The purpose of this study is to develop a monolayer surface coating of stearic acid on Sn-Ag-Cu solder powder to limit oxidation.

Abstract

Purpose

The purpose of this study is to develop a monolayer surface coating of stearic acid on Sn-Ag-Cu solder powder to limit oxidation.

Design/methodology/approach

Stearic acid was adsorbed onto Sn-Ag-Cu solder powder through liquid-phase adsorption. The isotherm of adsorption was measured and then the microstructure of coated powder was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy.

Findings

The adsorption isotherm of stearic acid on the powder was “H” type, which revealed the layer-by-layer adsorption on non-porous surface. When the concentration of solution was in the range of 0.001-0.006 mol/L, with an adsorption amount of 0.12 ± 0.1 mg/g, monolayer stearic acid covered the solder powder completely. Uniform and integrated self-assembled monolayer coating was formed through hydrogen bonds between the oxygen ions in surface lattice of Sn3.0Ag0.5Cu solder powder and the —O—H hydroxyl group of stearic acid. The maximum angle of stability of coated powder also reduced by 2.87° compared with that of non-coated powder. The increase rate of oxygen content of coated powder was much slower than that of non-coated powder when they were exposed to humid air.

Originality/value

As a result, oxidation of fine solder powder was effectively limited. Essentially, this method can also be applied to the coating of other types of solder powder and has reference significance to other coating by liquid-phase method.

Details

Soldering & Surface Mount Technology, vol. 31 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

To view the access options for this content please click here
Article
Publication date: 18 February 2019

Fen Peng, Wensheng Liu, Yunzhu Ma, Chaoping Liang, Yufeng Huang and Siwei Tang

To explore substitutes for traditional Sn-Pb solder, Sn-20In-2.8Ag was considered because of its appropriate melting temperature, good reliability and high ductility at…

Abstract

Purpose

To explore substitutes for traditional Sn-Pb solder, Sn-20In-2.8Ag was considered because of its appropriate melting temperature, good reliability and high ductility at less than 100°C. However, the mechanical properties of Sn-20In-2.8Ag were not satisfactory. The reason for the poor mechanical properties of the Sn-20In-2.8Ag/Cu joint was revealed, and a way to solve the problem was found.

Design/methodology/approach

The microstructure evolution, characteristics of melting and solidification and joining performance with Cu were investigated using scanning electron microscopy (SEM), electron probe microanalysis, differential scanning calorimetry (DSC) and mechanical testing.

Findings

SEM results showed that the microstructure of Sn-20In-2.8Ag was composed of coarse dendritic Ag2In and γ phases, with Ag2In distributed at the grain boundaries. DSC measurements revealed that small amount of low temperature eutectic reaction, L → Ag2In + β + γ, occurred at 112.9°C. This reaction was caused by the segregation of indium, which is a process that has a strong driving force. In the lap-shear testing, a crack propagated along the grain boundary of the solder, and failure showed an intergranular fracture. This failure was connected with the three-phase eutectic and coarse Ag2In. Thus, to improve the mechanical properties, segregation of indium should be reduced and coarsening of Ag2In should be prevented.

Originality/value

The reason for the unsatisfactory mechanical properties of Sn-20In-2.8Ag was revealed via microstructural observations and solidification analysis, and the way to solve this problem was found.

Details

Soldering & Surface Mount Technology, vol. 31 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

1 – 2 of 2