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The formation of thin intermetallic compounds (IMC) due to reaction between the solder and substrate during device fabrication is essential to achieve a good metallurgical bond. Nevertheless, excessive IMC growth significantly decreases the reliability of the solder joint. The thickness of IMC is influenced by numerous factors during the component fabrication process and in service. Stress is known to be an important factor, but no existing method can be used to study the effect of stress state on IMC growth. This work presents a novel method to study the effect of stress on interface IMC layer growth of Sn-Ag-Cu lead-free solder on the Cu substrate coated with electroless Ni and immersion Au (ENIG). In this technique, C-ring is used and in-plane bending induced tensile and compressive stresses can be applied by tightening the C-ring. Isothermal annealing experiments at 125 °C and at different levels of induced bending stresses on the C-ring were investigated The effect of in-plane tensile and in-plane compressive stresses on IMC growth are quantified.
Date of Conference: 8-10 Dec. 2004