• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.72-75
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• 2003

솔더의 상호확산을 이용한 저온 칩 접합을 구현하기 위하여 $117^{\circ}C$의 공정 온도를 가지는 In과 Sn 솔더패드를 $25\;mm^2$의 접합면적에 형성하고 두 솔더의 융점 보다 낮은 온도인 $120^{\circ}C$에서 접합을 시행하였다. 30초의 반응시간에서도 접합이 이루어 졌으며 반응시간이 지남에 따라 두 솔더가 반응하여 혼합상을 형성하였다. 솔더패드 접합에서 접합부는 낮은 접속저항과 높은 접속강도를 가짐을 확인할 수 있었다. $40\;{\mu}m$의 극미세피치의 In, Sn 솔더 범프를 형성하여 접합부를 형성하였으며 daisy chain을 형성한 접합부를 이용하여 평균 $65\;m\Omega/bump$ 저항값을 얻을 수 있었다. 상온에서 시효후 $54\%$의 접속저항이 감소함을 확인할 수 있었다.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.09a
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• pp.253-257
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• 2003

The low temperature flip chip technique is applied to the package of the temperature-sensitive devices for LCD systems and image sensors since the high temperature process degrades the polymer materials in their devices. We will introduce the various low temperature flip chip bonding techniques; a conventional flip chip technique using eutectic Bi-Sn (mp: $138^{\circ}C$) or eutectic In-Ag (mp: $141^{\circ}C$) solders, a direct bump-to-bump bonding technique using solder bumps, and a low temperature bonding technique using low temperature solder pads.

• Korean Journal of Materials Research
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• v.10 no.12
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• pp.799-806
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• 2000

Cu$_{6}$Sn$_{5}$-dispersed 63Sn-37Pb solder bumps of 760$\mu\textrm{m}$ size were fabricated on Au(0.5$\mu\textrm{m}$)/Ni(5$\mu\textrm{m}$)/Cu(27$\pm$20$\mu\textrm{m}$) BGA substrates by screen printing process, and their shear strength were characterized with variations of dwell time at reflow peak temperature and aging time at 15$0^{\circ}C$ . With dwell time of 30 seconds at reflow peak temperature, the solder bumps with Cu$_{6}$Sn$_{5}$ dispersion exhibited higher shear strength than the value of the 63Sn-37Pb solder bump. With increasing the dwell time longer than 60 seconds, however the shear strength of the Cu$_{6}$Sn$_{5}$-dispersed solder bumps became lower than that the 63Sn-37Pb solder bumps. The failure surface of the solder bumps could be divided into two legions of slow crack propagation and critical crack propagation. The shear strength of the solder bumps was inversely proportional to the slow crack propagation length, regardless of the dwell time at peak temperature, aging time at 150 $^{\circ}C$ and the volume fraction of Cu$_{6}$Sn$_{5}$ dispersion.> 5/ dispersion.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.4
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• pp.11-17
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• 2010

The electromigration phenomenon in lead-free flip-chip solder joint has been one of the serious problems. To understand the mechanism of this phenomenon, the crystallographic orientation of Sn grain in the Sn-Ag-Cu solder bump has been analyzed. Different time to failure and different microstructural changes were observed in the all test vehicle and bumps, respectively. Fast failure and serious dissolution of Cu electrode was observed when the c-axis of Sn grain parallel to electron flow. On the contrary of this, slight microstructural changes were observed when the c-axis of Sn perpendicular to electron flow. In addition, underfill could enhance the electromigration reliability to prevent the deformation of solder bump during EM test.

• Advances in materials Research
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• v.1 no.1
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• pp.83-92
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• 2012

The effect of under-bump-metallization (UBM) on electromigration was investigated at temperatures ranging from $135^{\circ}C$ to $165^{\circ}C$. The UBM structures were examined: 5-${\mu}m$-Cu/3-${\mu}m$-Ni and $5{\mu}m$ Cu. Experimental results show that the solder joint with the Cu/Ni UBM has a longer electromigration lifetime than the solder joint with the Cu UBM. Three important parameters were analyzed to explain the difference in failure time, including maximum current density, hot-spot temperature, and electromigration activation energy. The simulation and experimental results illustrate that the addition 3-${\mu}m$-Ni layer is able to reduce the maximum current density and hot-spot temperature in solder, resulting in a longer electromigration lifetime. In addition, the Ni layer changes the electromigration failure mode. With the $5{\mu}m$ Cu UBM, dissolution of Cu layer and formation of $Cu_6Sn_5$ intermetallic compounds are responsible for the electromigration failure in the joint. Yet, the failure mode changes to void formation in the interface of $Ni_3Sn_4$ and the solder for the joint with the Cu/Ni UBM. The measured activation energy is 0.85 eV and 1.06 eV for the joint with the Cu/Ni and the Cu UBM, respectively.

• Korean Journal of Metals and Materials
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• v.49 no.3
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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.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.235-237
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• 2007

In this paper, fabrication of Sn-3.0Ag-0.5Cu solder bumping having accurate composition and behavior of intermetallic compounds(IMCs) growth at interface between Sn-Ag-Cu bumps and Cu substrate were studied. The ternary alloy of the Sn-3.0Ag-0.5Cu solder was made by two binary(Sn-Cu, Sn-Ag) electroplating on Cu pad. For the manufacturing of the micro-bumps, photo-lithography and reflow process were carried out. After reflow process, the micro-bumps were aged at $150^{\circ}C$ during 1 hr to 500 hrs to observe behavior of IMCs growth at interface. As a different of Cu contents(0.5 or 2wt%) at Sn-Cu layer, behavior of IMCs was estimated. The interface were observed by FE-SEM and TEM for estimating of their each IMCs volume ratio and crystallographic-structure, respectively. From the results, it was found that the thickness of $Cu_3Sn$ layer formed at Sn-2.0Cu was thinner than the thickness of that layer be formed Sn-0.5Cu. After aging treatment $Cu_3Sn$ was formed at Sn-0.5Cu layer far thinner.

• Journal of the Korean Society of Radiology
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• v.8 no.7
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• pp.371-376
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• 2014

The process of flip-chip bump bonding, Au wire bonding and encapsulation were sucessfully developed and modularized. The CdTe sensor and ROIC were optimally jointed together at $150^{\circ}C$ and $270^{\circ}C$ respectively under24.5 N for 30s. To make SnAg bump on ROIC easy to be bonded, the higher bonding temperature was established than CdTe sensor's. In addition, the bonding pressure was lowered minimally because CdTe Sensor is easier to break than Si Sensor. CdTe multi-energy sensor module observed were no electrical failures in the joints using developed flip chip bump bonding and Au wire bonding process. As a result of measurement, shearing force was $2.45kgf/mm^2$ and, it is enough bonding force against threshold force, $2kgf/mm^2s$.

• Journal of the Korean Society of Industry Convergence
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• v.12 no.4
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• pp.215-219
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• 2009

A packaging technology based on flip-chip bonding and Pb-free solder for silicon pressure sensors on printed circuit board (PCB) is presented. First, the bump formation process was conducted by Pb-free solder. Ag-Sn-Cu solder and the pressed-screen printing method were used to fabricate solder bumps. The fabricated solder bumps had $189-223{\mu}m$ width, $120-160{\mu}m$ thickness, and 5.4-6.9 standard deviation. Also, shear tests was conducted to measure the bump shear strength by a Dage 2400 PC shear tester; the average shear strength was 74 g at 0.125 mm/s of test speed and $5{\mu}m$ shear height. Then, silicon pressure sensor packaging was implemented using the Pb-free solder and bump formation process. The characteristics of the pressure sensor were analogous to the results obtained when the pressure sensor dice are assembled and packaged using the standard wire-bonding technique.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.56-56
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• 2013

Sn-Ag 전해도금시 도금욕의 Sn 이온의 농도, Ag 이온의 농도, MSA 함량 및 인가 전류밀도 등의 인자들이 솔더의 조성과 표면형상에 미치는 영향에 관하여 연구하였다. 본 연구를 통하여 20의 미세피치와 15의 범프 높이를 가지는 공정 Sn-Ag 솔더 범프를 형성하였다. 도금된 솔더의 조성은 XRF와 ICP 분석을 통하여 확인하였고 형상은 광학현미경과 SEM을 통해 분석하였다. 또한 void 발생 여부 확인을 위해 FIB장비 및 X-Ray inspection장비를 사용 내부 Void 형상을 분석하였다. 전해 도금시 작용하는 주요 도금인자의 변경을 통해 15ASD에서 양호한 Bump를 구현하였다.