| Eutectic tin-lead solder alloy is widely used in electronic packaging industry because of its good physical properties and low cost. Research on the mechanical behavior of tin-lead solder is one of the basic jobs to improve the long-term reliability of solder balls and electronic packaging.In this work, the cyclic mechanical behaviors of eutectic 63Sn-37Pb under uniaxial and multiaxial loading were investigated. It is shown that eutectic tin-lead solder is cyclic softening under uniaxial, pure torsional and axial/torsional ratcheting loading. The variation of maximum stress and minimum stress with cycles can be divided into three stages. Cyclic softening was found to be due to the decrease of friction stress.A series of uniaxial and multiaxial ratcheting experiments have been conducted on 63Sn-37Pb solder alloys. Even low-level stress can cause high ratcheting strain. The rate of ratcheting strain remains steady and does not decay rapidly. Axial stress and shear strain range have great influence on axial stress and its rate. Under constant axial stress and cyclic shear strain, the axial ratcheting strain and its rate rise with increase of the axial stress and shear strain range, but loading history and its sequence have no clear influence on the ratcheting behavior. The axial ratcheting strain rate is found to be strongly dependent on applied shear strain rates in axial/torsional ratcheting experiments. Axial ratcheting strain rates increase with decreasing shear strain rates.In order to predict the ratcheting rate of each step under multiaxial loading accurately, a simple constitutive model, based on Edmunds-Beer Equation, is proposed. The simple model takes account of the rate dependent ratcheting behavior of Sn-Pb solder and is promising to be easily used in engineering applications, without many complex coefficients to be determined.
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