• 마이크로전자및패키징학회지
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• 제12권2호
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• pp.95-103
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• 2005

42Sn-58Bi 솔더(이하 wt.$\%$에 의한 표기)와 무전해 Ni-P/치환 Au under bump metallurgy (UBM) 간의 계면 반응을 intermetallic compound (IMC)의 형성과 성장, UBM의 감소, 그리고 범프 전단강도의 영향 관점에서 시효 처리 전 후에 어떠한 변화가 생기는 지를 알아보고자 하였다. 치환 Au 층을 $5{\mu}m$ 두께의 무전해 Ni-P ($14{\~}15 at.\%$ P)위에 세 가지 각기 다른 두께, 즉 $0{\mu}m$(순수한 무전해 Ni-P UBM), $0.1{\mu}m$, $1{\mu}m$로 도금하였다. 그 후 42Sn-58Bi 솔더 범프를 세 가지 다른 UBM 구조에 스크린프린팅 방식으로 형성하였다. 범프 형성 직후에는 세 가지 다른 UBM구조에서 솔더와 UBM 사이에 공통적으로 $Ni_3Sn_4$ IMC (IMC1) 만이 형성됐다. 하지만, 이를 $125^{\circ}C$에서 시효 처리를 할 경우 특이하게 Au를 함유한 UBM 구조에서는 $Ni_3Sn_4$ 위로 또 다른 4원계 화합물 (IMC2)이 관찰되었다. 원자 비로 $Sn_{77}Ni{15}Bi_6Au_2$인 4원계 화합물로 확인되었다. $Sn_{77}Ni{15}Bi_6Au_2$ 층은 솔더 조인트의 접합성에 매우 치명적인 영향을 미쳤다. 시효 처리를 거친 Au를 함유한 UBM 구조에서 솔더 범프의 전단 강도 값은 시효 처리 전에 비해 $40\%$ 이상의 감소를 보였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.456-462
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• 2002

In the present work, a low cost and fine pitch bumping process by electroless Ni/immersion Au UBM (under bump metallurgy) and stencil printing for the solder bump on the Al pad is discussed. The Chip used this experimental had an array of pad 14x14 and zincate catalyst treatment is applied as the pretreatment of Al bond pad, it was shown that the second zincating process produced a dense continuous zincating layer compared to first zincating. Ni UBM was analyzed using Scanning electron microscopy, Energy dispersive x-ray, Atomic force microscopy, and X-ray diffractometer. The electroless Ni-P had amorphous structures in as-plated condition. and crystallized at 321 C to Ni and Ni$_3$P. Solder bumps are formed on without bridge or missing bump by stencil print solder bump process.

• 대한금속재료학회지
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• 제49권3호
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• pp.237-242
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• 2011

The effect of shearing speed on the shear force and energy of Sn-0Ag-0.5Cu solder ball was investigated. Various UBM (under bump metallurgy)'s on Cu pads were used such as ENEPIG (Electroless Nickel, Electroless Palladium, Immersion Gold; Ni/Pd/Au), ENIG (Electroless Nickel, Immersion Gold; Ni/Au), OSP (Organic Solderability Preservative). To fabricate a shear test specimen, a solder ball, $300{\mu}m$ in diameter, was soldered on a pad of FR4 PCB (printed circuit board) by a reflow soldering machine at $245^{\circ}C$. The solder bump on the PCB was shear tested by changing the shearing speed from 0.01 m/s to 3.0 m/s. As experimental results, the shear force increased with a shearing speed of up to 0.6 m/s for the ENIG and the OSP pads, and up to 0 m/s for the ENEPIG pad. The shear energy increased with a shearing speed up to 0.3 m/s for the ENIG and the OSP pads, and up to 0.6 m/s for the ENEPIG pad. With a high shear speed of over 0 m/s, the ENEPIG showed a higher shear force and energy than those of the ENIG and OSP. The fracture surfaces of the shear tested specimens were analyzed, and the fracture modes were found to have closer relationship with the shear energy than the shear force.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 춘계 기술심포지움 논문집
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• pp.85-91
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• 2002

Even though electroless Hi and Sn-Ag-Cu solder are widely used materials in electronic packaging applications, interfacial reactions of the ternary Ni-Cu~Sn system have not been known well because of their complexity. Because the growth of intermetallics at the interface affects reliability of solder joint, the intermetallics in Ni-Cu-Sn system should be identified, and their growth should be investigated. Therefore, in present study, interfacial reactions between electroless Ni UB7f and 95.5Sn-4.0Ag-0.5Cu alloy were investigated focusing on morphology of the IMCs, thermodynamics, and growth kinetics. The IMCs that appear during a reflow and an aging are different each other. In early stage of a reflow, ternary IMC whose composition is Ni$_{22}$Cu$_{29}$Sn$_{49}$ forms firstly. Due to the lack of Cu diffusion, Ni$_{34}$Cu$_{6}$Sn$_{60}$ phase begins growing in a further reflow. Finally, the Ni$_{22}$Cu$_{29}$Sn$_{49}$ IMC grows abnormally and spalls into the molten solder. The transition of the IMCs from Ni$_{22}$Cu$_{29}$Sn$_{49}$ to Ni$_{34}$Cu$_{6}$Sn$_{60}$ was observed at a specific temperature. From the measurement of activation energy of each IMC, growth kinetics was discussed. In contrast to the reflow, three kinds of IMCs (Ni$_{22}$Cu$_{29}$Sn$_{49}$, Ni$_{20}$Cu$_{28}$Au$_{5}$, and Ni$_{34}$Cu$_{6}$Sn$_{60}$) were observed in order during an aging. All of the IMCs were well attached on UBM. Au in the quaternary IMC, which originates from immersion Au plating, prevents abnormal growth and separation of the IMC. Growth of each IMC is very dependent to the aging temperature because of its high activation energy. Besides the IMCs at the interface, plate-like Ag3Sn IMC grows as solder bump size inside solder bump. The abnormally grown Ni$_{22}$Cu$_{29}$Sn$_{49}$ and Ag$_3$Sn IMCs can be origins of brittle failure.failure.