Papers by Keyword: Thermal Fatigue Behavior

Abstract: Thermal cycling tests were conducted on solder joints of wafer-level chip scale packages with Sn-3.0Ag-0.5Cu (mass%) to investigate the effect of difference in the thermal cycle profile on the thermal fatigue properties. The tests were conducted using three different types of chambers and the temperature range was-40°C to 125°C. The result showed that the thermal fatigue life tends to be shorter when the temperature change rate in the thermal cycle profile is slow. This means that the effect of creep on thermal fatigue life is large. The analogous analysis result was obtained by finite element analysis. The microstructural analysis of damaged joints revealed that recrystallized grains form in the solder and crack progresses at their grain boundaries. Thus the thermal fatigue life was suggested to be dominated by the ease of formation of recrystallized grains in solder.

Abstract: The effect of carbon content on the microstructural evolution and thermal fatigue behavior of Ni-Cr-Fe-Mo alloy with different carbon content was carried out at temperature ranging from 20°C to 920°C. The microstructure evolution was detected and the length of thermal fatigue cracks was measured. The results revealed that all the alloys are mainly composed of γ phase and carbides. With the increase of carbon content, the volume fraction of carbides increase and the morphology varies from blocky to script-like and sheet-like. The microstructural features exert influence on the thermal fatigue cracks of the alloys with different carbon content. Considering the thermal fatigue properties, the optimum carbon content of the Ni-Cr-Fe-Mo alloy superalloy should be below 0.08wt.%.

Abstract: With the Uddeholm self-restricted thermal fatigue method, the transformation of phase constitutions and morphology of boride layer after 3000 cycles of thermal fatigue test was studied by XRD and SEM and the surface residual stress in the process of thermal fatigue test was researched by X-ray Stress Analyzer; the formation of the heat checking of boride layer was also analyzed. The results show that with the high strength and excellent thermal stability of boride layer, morphology of heat checking alters. Therefore, boronizing treatment of H13 steel improves its thermal fatigue behavior.