| Summary: | 碩士 === 中興大學 === 化學工程學系所 === 99 === Flip chip in package have been used extensively in electronic product, the advantage of small size, high density, good reliability has been discovered. Flip chip is made by solder joint and under bump metallurgy. To decrease copper atom reacting with solder, a diffusion barrier in UBM that made by nickel is been researched extensively. Because of the difference of coefficient of thermal expansion, thermal stress is become an important issue. The solder joints wetting, interfacial reaction of solder and substrate would be problem in electronic reliability. In order to realize the difference of Coefficient of thermal expansion, we applied compression and tension stress/strain by modules on silicon wafer. With different UBM layer that effect Ni/Sn interfacial reaction.
Ni3Sn4 phase formed between Ni/Sn interfacial at 200, 170, 150ºC. Regardless of compression or tension strain would cause IMC thickness growth thicker. With reaction time increasing, the effect of strain/stress is going to be great. Moreover, the applied strain/stress could force nickel grain growth. In FIB cross section, compression strain would cause grain become long and thin vertically. Tension strain would cause grain growth bigger and got uniform grain boundary.
In reflow experiment, Ni3Sn4 grain morphology grow smaller because of the strain larger. In region M, the Ni3Sn4 grain become smaller. With no bending specimen, the Ni3Sn4 grain become large. Ni3Sn4 grain difference being less until reflow time exceed to 60min. In initial reaction stage, Ni3Sn4 grain would be round shape. Then Ni3Sn4 grain grow from round shape to needle crystal. Finally, needle crystal become to faceted crystal.
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