This study focused on predicting the fatigue life of an insulated gate bipolar transistor (IGBT) power module for electric locomotives. The effects of different wiring technologies, including aluminum wires, copper wires, aluminum ribbons, and copper ribbons, on solder fatigue life were investigated to meet the high power requirement of the IGBT module. The module's temperature distribution and solder fatigue behavior were investigated through coupled electro-thermo-mechanical analysis based on the finite element method. The ribbons attained a chip junction temperature that was 30° C lower than that attained with conventional round wires. The ribbons also exhibited a lower plastic strain in comparison with the wires. However, the difference in plastic strain and junction temperature among the different ribbon materials was relatively small. The ribbons also exhibited different crack propagation behaviors relative to the wires. For the wires, the cracks initiated at the outmost edge of the solder, whereas for the ribbons, the cracks grew in the solder layer beneath the ribbons. Comparison of fatigue failure areas indicated that ribbon bonding technology could substantially enhance the fatigue life of IGBT modules and be a potential candidate for high power modules.
In this study, we developed an ultra-thin flexible printed circuit board(FPCB) using the sputtered flexible copper clad laminate. In order to enhance the adhesion between copper and polyimide substrate, a NiMoNb addition layer was applied. The mechanical durability and flexibility of the ultra-thin FPCB were characterized by stretching, twisting, bending fatigue test, and peel test. The stretching test reveals that the ultra-thin FPCB can be stretched up to 7% without failure. The twisting test shows that the ultra-thin FPCB can withstand an angle of up to 120 o . In addition, the bending fatigue test shows that the FPCB can withstand 10,000 bending cycles. Numerical analysis of the stress and strain during stretching indicates the strain and the maximum von Mises stress of the ultra-thin FPCB are comparable to those of the conventional FPCB. Even though the ultra-thin FPCB shows slightly lower durability than the conventional FPCB, the ultra-thin FPCB has enough durability and robustness to apply in industry.
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