| Summary: | 博士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 98 === This present study investigated the fracture behavior of the Pb-free solder joint with the aid of micro-impact test method. The results of investigation indicated that the characteristic curve of the micro-impact test provides the base for estimating the mechanical properties and identifying the fracture mechanism of the joint. The full width at half maximum (FWHM) can be regarded as the index for defining the fracture type. The fracture energy obtained from the curve gives the estimation of the energy needed for completely detaching the solder joint. The fracture mechanism can be categorized as Type I (fracture at solder/solder), Type II (fracture at Solder/IMC), and Type III (fracture at IMC/Ni). The magnitudes of FWHM and the fracture energy of the corresponding fracture type are in the descending order: Type I ＞ Type II ＞ Type III. Incorporating the values of Young’s modulus, micro hardness, and lattice mismatch, it is understandable that the fracture mechanism is governed by the plastic deformability of the solder alloy and the lattice mismatch between the interfaces. The proportion of the Type I fracture for all the solder joints investigated is in the descending order of SAC101NiIn/AuNi ＞ SAC105/AuNi ＞ SAC205/AuNi ＞ SAC105Co/AuNi ＞ SAC105Ni/AuNi.
The interaction during reflow and the thermal cycle test (TCT) greatly affect the microstructure of the solder joint and the formation of interfacial intermetallic compound. It will further increase the proportion of the interfacial fracture type (Type II and Type III). The proportion of interfacial fracture increases from 15.4 % to 69.2 % when the reaction time increases from 30 sec to 120 sec, while the proportion becomes as high as 37.5 % after 1000 cycles of test.
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