Abstract
Sn96.5Ag3Cu0.5 (SAC305) is widely used as lead-free solder for surface mount technology (SMT) card assembly and for ball-grid-array (BGA) interconnection in the microelectronic packaging industry as solder balls and pastes. In this study the effects of Lanthanum (La) doping on SAC305 under thermal aging was investigated as function of intermetallic compounds (IMCs) growth and grain size evolution. The morphology of the microstructure was analyzed under Scanning Electron Microscope (SEM) and optical microscope, the elemental distribution was confirmed by Energy Dispersive Spectroscopy (EDS) and phase identification of the crystalline structure formed during thermal aging was confirmed by x-ray diffraction (XRD). It was found that the microstructure of SAC305 solder alloy changes significantly with addition of La. Quantitative analysis of grain size and intermetallic particle size was performed both for undoped and La-doped SAC305 alloys.
Highlights
The increasingly environmental concern over the toxicity of lead (Pb) combined with strict environmental regulations around the world have been targeted to eliminate the usage of Pb-bearing solders in electronic assemblies and to adopt lead-free solder alloys [1,2,3,4,5]
It was observed that the microstructure of un-doped SAC305 alloy contained two intermetallic compounds (IMCs) phases, i.e. Ag3Sn and Cu6Sn5 while that of lanthanum doped SAC305 alloy contained three IMC phases i.e. Ag3Sn, Cu6Sn5 and La5Sn3
Previous studies [25,57,61,86] found that Lanthanum doped SAC alloy will cause LaSn3 IMCs while our results shows the presence of La5Sn3 instead of LaSn3
Summary
The increasingly environmental concern over the toxicity of lead (Pb) combined with strict environmental regulations around the world have been targeted to eliminate the usage of Pb-bearing solders in electronic assemblies and to adopt lead-free solder alloys [1,2,3,4,5]. The European Union Waste Electrical and Electronic Equipment (WEEE) Directive, published in 2002 and Restriction of Hazardous Substances (RoHS) Directive of European Community, published in 2003 restricted the usage of certain toxic materials including Lead (Pb) in production of electronic devices used in European Union effective on 1 July 2006 [6]. Owing to the enforcement of these directives, all electrical or electronic equipment and devices produced in or imported to EU member countries must meet the lead-free standards except those items that are exempted from the bans. Several Japanese electronics manufacturers have successfully created a market differentiation and increased market share based on “green” products that use Pb-free solders and many Japanese companies have brought their lead-free products into the market much earlier than the EU directives’ effective dates, including Panasonic in 2001, Sony in 2001: Toshiba in 2000, NEC in 2002, and Hitachi in 2001.
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