Content area
Full Text
1.
Introduction
The banning of lead in many solder alloys marked the beginning of efforts in developing potential replacement candidates among lead-free solders. In such efforts, wide ranges of lead-free solder systems (binary, tertiary and quaternary) have been intensively studied. Among the vast availabilities of the lead-free solders, Sn-Ag-Cu (SAC) formulations, and particularly the Sn-3.0Ag-0.5Cu (SAC305) alloy, have been found to be well-rounded contenders which relatively outperform other lead-free solders.
The current development of lead-free solders has led to the production of new variations in solder alloy formulations and families. Evaluation of the developed solder alloy involves several characterizations and tests such as phase analysis, morphological behaviour, corrosion resistance and mechanical properties. The mechanical testing (tensile, shear and hardness) is one of the main indicators in determining the performance of lead-free solders and thus has received significant interest among scholars and researchers (Karaköse et al. , 2016). Specifically, in mechanically evaluating a solder alloy, the incorporation of hardness testing in most research studies was obvious, as such techniques offer direct information regarding the material resistance towards deformation (Marques et al. , 2013). Currently, the preferred methods include the Vickers microhardness, Brinell microhardness and nanoindentation (the Rockwell hardness test is another typical testing method, but from 2010 to 2016, hardness evaluation of lead-free solders showed little or no involvement of the technique). The capabilities and merits of each method are seen to influence the testing selection process, including the consideration of the indenter size, loading capability and test design (Spinelli et al. , 2014; Sakharova et al. , 2009). Additionally, a favourable interest in these methods can also be attributed to the following (Yahaya et al. , 2016; Oliver and Pharr, 2004):
* Simplicity in the hardness determination : the Vickers and Brinell microhardness allows direct acquisition of the hardness values. Such access is useful and acts as a preliminary evaluation stage prior to further characterization.
* Flexibility in testing orientation/condition : various types of lead-free solder samples, such as bulk samples, joints and cast solder alloys can be evaluated.
* Enhancements in the features : methods such as nanoindentation allow dynamic load control measurements, which simultaneously yield additional analysis and information.
An adequate understanding of the method used for the hardness measurement is very important....