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

Abstract

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.

Influence of gallium addition in Sn–Ag–Cu lead-fee solder

“…5. When adding 1 wt% Ga, the spreading ratio is about 77 % in a good agreement with Chen et al [12].…”

“…GB/ T11364-2008), spreading ratio (K) has been calculated by K ¼ HÀh H , where H is the diameter of the solder being spherical, and h is the height of the soldering after spreading. The calculated spreading ratios of the four alloys in the present work have been plotted and compared to the results of Chen et al [12] in Fig. 5.…”

“…5 The calculated spreading ratios of different Sn-Ag-Cu-Ga alloys compared to Chen et al [12] J Mater Sci: Mater Electron (0 wt% Ga) to 2.7 lm (1.5 wt% Ga) during solidification of the solders. As the intermetallic compounds are brittle and thus too thick interfacial layer is harmful to the joints.…”

“…So far Sn-Ag-Cu based alloys could satisfy most of those technical requirements and commercial cost [5,6], except the melting temperature being 20-30°C higher than that of the conventional Sn-Pb solders. It therefore becomes a key point to optimise alloy compositions in order to obtain lower melting temperatures [7][8][9][10][11][12]. In 2005, Chen et al [12] has found that Sn-Ag-Cu alloy with Ga (7-10 wt% Ga) addition have lower melting temperature, greater melting range, and smaller wetting angles.…”

“…It therefore becomes a key point to optimise alloy compositions in order to obtain lower melting temperatures [7][8][9][10][11][12]. In 2005, Chen et al [12] has found that Sn-Ag-Cu alloy with Ga (7-10 wt% Ga) addition have lower melting temperature, greater melting range, and smaller wetting angles. Taking into account the price of Ga, the cost of solders with large Ga addition would be unaffordable for industrial manufacturing.…”