Plumbridge, William J.
Second generation lead-free solder alloys: a challenge to thermodynamics.
Monatshefte fur Chemie / Chemical Monthly, 136(11) pp. 1811–1821.
For environmental reasons, lead has to be removed from solder alloys used for interconnection purposes in electronics equipment. A new series of alloys, mainly based upon tin, and often containing copper and silver, has been evolved by empirical reasoning. A more theoretical approach is now being pursued, using thermodynamic principles, to produce the second generation of solder alloys. The paper outlines the soldering process, the requirements of solder alloys, and the various mechanisms (such as overload, fatigue, creep, and thermomechanical fatigue) that are potential causes of failure in service. It also describes from the manufacturing and the performance perspectives, the physical and mechanical properties necessary for reliable solder joints. These include conductivity, melting point, strength, ductility, and thermal stability of microstructure. The challenging question is posed as to how can thermodynamics contribute to prescribing and developing an improved series of alloys?
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