Critical Review of the Engelmaier Model for Solder Joint Creep Fatigue Reliability

Structural Reliability of Novel 3-D Integrated Thermal Packaging for Power Electronics

“…[21] On the basis of experimental fatigue data presented by R.N. Wild for 63Sn37Pb solder joints used for interconnecting leadless devices on printed wiring boards, Engelmaier proposed a failure model, [22] …”

“…This version does incorporate a frequency and temperature term. The value of m varies from 1.89 to 2.5, as per literature [22], and inversely relates the cycles-to-failure to the shear strain.…”

“…The equation relating the number of cycles to failure to the plastic strain was developed by Engelmaier [22,23] in the early 1980's and is given as following.…”

“…However, in actual application condition, we often observe a cyclic warpage in substrate due to the effects of thermal expansion mismatch and temperature gradient, unless the substrate is stiffened. [22] Engelmaier updated the drawbacks in his initial model later. He modified the cyclic frequency term in the model above to focus on the half cycle dwell time at the maximum temperature.…”

“…Engelmaier identified six caveats in his model (includes assumptions and areas of concern), which are namely, 1) solder quality, 2) large temperature excursions, 3) high frequency/low temperature, 4) local expansion mismatch, 5) lead-solder CTE mismatch, and 6) very stiff leads/large expansion mismatches. [22,23] …”