Papers by Author: Keisuke Yoshizawa

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Authors: Ikuo Shohji, Keisuke Yoshizawa, Masaharu Nishimoto, Takayuki Kawano
Abstract: The effect of the mechanical and physical properties of an underfill material on thermal stress relief in a lead-free chip size package (CSP) solder joint has been investigated. Thin sheets of underfill materials for the CSP solder joint were prepared and the mechanical and physical properties of the sheets were investigated. Using these properties, thermal stress relief in an encapsulated CSP lead-free solder joint with the underfill material was examined by a finite element analysis method under thermal cycle conditions in the temperature range from 293K to 398K and 233K.
Authors: Ikuo Shohji, Tomotake Tohei, Keisuke Yoshizawa, Masaharu Nishimoto, Yasushi Ogawa, Takayuki Kawano
Abstract: Accelerated thermal cycling (ATC) tests were conducted to investigate an effect of thermal cycle conditions on thermal fatigue life of a chip size package (CSP) lead-free solder joint. A ternary Sn-Ag-Cu alloy was used as a lead-free solder material. For frequency of thermal cycle (1~3 cycles/h) and maximum (388~423 K) and minimum (223~273 K) temperatures investigated, the effects of them on thermal fatigue life of the solder joint were slight. On the contrary, correlation was recognized between temperature amplitude and thermal fatigue life of the solder joint. The thermal fatigue life increased with decreasing temperature amplitude. The relationship obeyed the Coffin-Manson’s type equation.
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