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열충격 사이클에 따른 SnAgCu 솔더별 솔더 접합부의 신뢰성 및 계면반응
오철민 ( Chul Min Oh ),박노창 ( No Chang Park ),한창운 ( Chang Woon Han ),방만수 ( Man Soo Bang ),홍원식 ( Won Sik Hong ) 대한금속·재료학회 2009 대한금속·재료학회지 Vol.47 No.8
Pb-free solder has recently been used in electronics in efforts to meet environmental regulations, and a number of Pb-free solder alloy choices beyond the near-eutectic SnAgCu solder are now available. With increased demand for thin and portable electronics, the high cost of alloys containing significant amounts of silver and their poor mechanical shock performance have spurred the development of low Ag SnAgCu solder, which provides improved mechanical performance at a reasonable cost. Although low Ag SnAgCu solder exhibits significantly higher fracture resistance under high-strain rates, little thermal fatigue data exist for this solder. Therefore, it is necessary to investigate thermal fatigue reliability of low Ag SnAgCu solder under variation of thermal stress in order to allow its implementation in electronic products with high reliability requirements. In this study, the reliability of Sn0.3Ag0.7Cu(SAC0307), a low Ag solder alloy, is discussed and compared with that of Sn3Ag0.5Cu(SAC305). Three sample types and six samples size are evaluated. Mechanical properties and microstructure of the solder joint are investigated under thermal shock cycles. It was observed that the mechanical strength of SAC0307 dropped slightly with thermal cycling relative to that of SAC305. This reveals that the failure mode of SAC0307 is different from that SAC305 under this critical condition.
DC/DC 전력 컨버터의 전류모드 PWM 제어기의 방사선 영향
노영환(Young Hwan Lho),황의성(Eui Sung Hwang),노경수(Kyeoung Su Lho),푸파논(Phouphanonh),캄푸는(Khamphoungeun),한창운(Chang Won Han) 한국철도학회 2011 한국철도학회 학술발표대회논문집 Vol.2011 No.10
DC/DC switching power converters produce DC output voltages from different DC input sources. The converters can be used in regenerative braking of DC motors to return energy back in the supply resulting in energy savings for the systems containing frequent stops. The current mode DC/DC converter is composed of a PWM (pulse width modulation) controller a MOSFET and inductor etc. Pulse width modulation is applied to control and regulate the total output voltage. It is shown that the variation of threshold voltage at MOSFET and the offset voltage increase caused by radiation effects make the PWM pulse unstable. In the PWM operation the missing pulses the changes in pulse width and a change in the period of the output waveform are studied by simulation program with integrated circuit emphasis (SPICE) and experiments.