Frequency-dependent strain-life characteristics of Sn1.0Ag0.1Cu solder on cupper pad at high cyclic frequency

The low-cycle strain-life characteristic of solder joint formed by reflowing Sn1.0Ag0.1Cu solder onto copper pad has been investigated at the high cyclic frequency regime between 30 Hz and 150 Hz. Expressing the strain-frequency-life relation of the solder joint as εpcbfq=moNαλ, the frequency exponent q has been evaluated to be 0.34, implying decreasing fatigue life with increasing cyclic frequency, in opposite trend to creep-fatigue. Analysis of the test system has suggested that while the stresses experienced by the solder joints increases only marginally with increasing frequency, the fatigue strength of the solder joint decreases drastically with increasing frequency - due to reduction in the fracture toughness of solder joints with increasing strain rate - giving rise to a net reduction in fatigue life of the solder joint.