• 대한금속재료학회지
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• 제46권1호
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• pp.33-38
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• 2008

The interfacial reactions and shear strength of pure Sn solder bump were investigated with different under bump metallizations (UBMs) and reflow numbers. Two different UBMs were employed in this study: Cu and Ni. Cu6Sn5 and Cu3Sn intermetallic compounds (IMCs) were formed at the bump/Cu UBM interface, whereas only a Ni3Sn4 IMC was formed at the bump/Ni UBM interface. These IMCs grew with increasing reflow number. The growth of the Cu-Sn IMCs was faster than that of the Ni-Sn IMC. These interfacial reactions greatly affected the shear properties of the bumps.

• 한국소음진동공학회논문집
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• 제15권10호
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• pp.1202-1210
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• 2005

This paper develops a computer model for estimating the bump characterisitcs of a cat)over type large-sized truck. The truck is composed of front and rear suspension systems, a frame, a cab, and ten tires. The computer model is developed using MSC.ADAMS. A shock absorber, a rubber bush, and a leaf spring affect a lot on the dynamic characteristic of the vehicle. Their stiffness and damping coefficient are measured and used as input data of the computer model. Leaf springs in the front and rear suspension systems are modeled by dividing them three links and joining them with joints. To improve the reliability of the developed computer model, the frame is considered as a flexible body. Thus, the frame is modeled by finite elements using MSC.PATRAN. A mode analysis is performed with the frame model using MSC.NASTRAN in order to link the frame model to the computer model. To verify the reliability of the developed computer model, a double wheel bump test is performed with an actual vehicle. In the double wheel bump, vortical displacement, velocity, acceleration are measured. Those test results are compared with the simulation results.

• Journal of Welding and Joining
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• 제19권5호
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• pp.520-525
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• 2001

The Sn-Pb eutectic solder bump formation ($150\mu\textrm{m}$ diameter, $250\mu\textrm{m}$ pitch) by electroplating was studied for flip chip package fabrication. The effect of current density and plating time on Sn-Pb deposit was investigated. The morphology and composition of plated solder surface was examined by scanning electron microscopy. The plating thickness increased wish increasing time. The plating rate became constant at limiting current density. After the characteristics of Sn-Pb plating were investigated, Sn-Pb solder bumps were fabricated in optimal condition of $7A/dm^$. 4hr. Ball shear test after reflow was performed to measure adhesion strength between solder bump and UBM (Under Bump Metallurgy). The shear strength of Sn-Pb bump after reflow was higher than that of before reflow.

• Journal of Welding and Joining
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• 제31권6호
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• pp.77-83
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• 2013

3D packaging technology using TSV (Through Silicon Via)has been studied in the recent years to achieve higher performance, lower power consumption and smaller package size because electrical line is shorter electrical resistivity than any other packaging technology. To stack TSV chips vertically, reliable and robust bonding technology is required because mechanical stress and thermal stress cause fracture during the bonding process. Cu pillar/solder ${\mu}$-bump bonding process is usually to interconnect TSV chips vertically although it has weak shape to mechanical stress and thermal stress. In this study, we suggest Insert-Bump (ISB) bonding process newly to stack TSV chips. Through experiments, we tried to find optimal bonding conditions such as bonding temperature and bonding pressure. After ISB bonding, we observed microstructure of bump joint by SEM and then evaluated properties of bump joint by die shear test.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 추계기술심포지움논문집
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• pp.49-53
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• 2002

The Sn-Cu eutectic solder bump formation ($140{\mu}{\textrm}{m}$ diameter, $250{\mu}{\textrm}{m}$ pitch) by electroplating was studied for flip chip package fabrication. The effect of current density and plating time on Sn-Cu deposit was investigated. The morphology and composition of plated solder surface was examined by scanning electron microscopy. The plating thickness increased with increasing time. The plating rate increased generally according to current density. After the characteristics of Sn-Cu plating were investigated, Sn-Cu solder bumps were fabricated on optimal condition of 5A/dm$^2$, 2hrs. Ball shear test after reflow was performed to measure adhesion strength between solder bump and UBM (Under Bump Metallization). The shear strength of Sn-Cu bump after reflow was higher than that of before reflow.

• Tribology and Lubricants
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• 제36권6호
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• pp.332-341
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• 2020

High-speed turbomachinery implements gas foil bearings (GFBs) due to their distinctive advantages, such as high efficiency, lesser part count, and lower weight. This paper provides the test results of the static structural stiffnesses and loss factors of bump-type foil thrust bearings with increasing preload and bearing deflection. The focus of the current work is to experimentally quantify variability in structural stiffnesses and loss factors among the four test thrust bearings with identical design values and material of the bump and top foil geometries using the same (open-source) fabrication method. A simple test setup, using a rigidly mounted non-rotating shaft and thrust disk, measures the bearing bump deflections with increasing static loads on the test bearing. The inner and outer diameters of the test bearings are 41 mm and 81 mm, respectively. The loss factor, best-representing energy dissipation in the test bearings, is estimated from the area inside the local hysteresis loop of the load versus the bearing deflection curve. The measurements show that structural stiffnesses and loss factors of the test bearings significantly rely on applied preloads and bearing deflections. Local structural stiffnesses of the test bearings increase with applied preloads but decrease with bearing deflections. Changes of loss factors are less sensitive to applied preloads and bearing deflections compared to those of structural stiffnesses. Up to 35% variability in static load structural stiffnesses is found between bearings, while up to 30% variability in loss factors is found between bearings.

• 한국산학기술학회논문지
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• 제18권5호
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• pp.674-680
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• 2017

본 논문은 현재 개인 휴대기기 및 대형 디스플레이 장비의 제어에서 폭넓게 사용되고 있는 터치스크린 패널 (TSP; Touch Screen Panel)의 정상 작동 유무를 확인하기 위한 micro bump 제작 기술에 관한 연구이다. 터치스크린 패널은 감압식, 정전식 등의 여러 가지 방식이 있으나 지금은 편리성에 의하여 정전식 방식이 주도하고 있다. 정전식의 경우 해당하는 좌표의 접촉에 따라 전기적 신호가 변화하게 되고, 이를 통하여 접촉 위치를 확인할 수 있으며 따라서 접촉 위치에 따른 전기 특성 검사가 필수적이다. 검사공정에서 TSP의 모델이 변경됨에 따라 새로운 micro bump를 제작이 및 검사 프로그램의 수정이 필수적이다. 본 논문에서는 새로운 micro bump 제작 시 mask를 사용하지 않아 보다 경제적이며 변화에 대응이 유연한 maskless lithography 시스템을 이용하여 micro bump 제작 가능성에 대하여 확인하였다. 이를 위하여 제작되는 bump의 pitch에 따른 전기장 간섭 시뮬레이션을 진행하였으며, maskless lithogrphy 공정을 적용하기 위한 패턴 이미지를 생성하였다. 이후 MEMS 기술에 해당하는 PR(Photo Resist) 패터닝 공정에서 노광(Lithography) 공정 및 현상(Developing) 공정을 통하여 PR 마스크를 제작한 후 electro-plating 공정을 통하여 micro bump를 제작하였다.

• 마이크로전자및패키징학회지
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• 제15권2호
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• pp.37-45
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• 2008

본 논문에서는 유기 기판 위에 $100{\mu}m$ 피치를 갖는 플립칩 구조인 Cu(60 um)/SnAg(20 um) 더블 범프 플립칩 어셈블리를 구현하여 이의 리플로우, 고온 유지 신뢰성, 열주기 신뢰성, Electromigration 신뢰성을 평가하였다. 먼저, 리플로우의 경우 횟수와 온도에 상관없이 범프 접속 저항의 변화는 거의 나타나지 않음을 알 수 있었다. 125도 고온 유지 시험에서는 2000시간까지 접속 저항 변화가 관찰되지 않았던 반면, 150도에서는 Kirkendall void의 형성으로 인한 접속 저항의 증가가 관찰되었다 또한 Electromigration 시험에서는 600시간까지 불량이 발생하지 않았는데 이는 Al금속 배선에서 유발되는 높은 전류 밀도가 Cu 칼럼의 높은 두께로 인해 솔더 영역에서는 낮아지기 때문으로 해석되었다. 열주기 시험의 경우, 400 cycle 이후부터 접속 저항의 증가가 발견되었으며, 이는 열주기 시험 동안 실리콘 칩과 Cu 칼럼 사이에 작용하는 압축 변형에 의해 그 사이에 있는 Al 및 Ti 층이 바깥쪽으로 밀려나감으로 인해 발생하는 것으로 확인되었다.

• 전자공학회논문지D
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• 제34D권7호
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• pp.30-36
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• 1997

Bump bonded piezoesistive silicon accelerometer was fabricated by the porous silicon micromachining and th eprocess technique of integrated circuit. The output voltage of the accelerometer fabricated on (111)-oreiented Si substrates with n/n$^{+}$n triple layers showed good linear characteristic of less than 1%. The measured sensitivity and the resonant frequency was about 743 .mu.V/g and 2.04 kHz, respectively. And the transverse sensitivity of 5.2% was measured from the accelerometer. Also, to investigate an influence on the output characteristics of the sensor due to bump bonding, the values of the piezoresistors were measured through thermal-cycling test in the temperature variation form -50 to 120.deg. C. Then, there was 0.014% resistance changes about 3.61 k.ohm., so sthe output charcteristics of the sensor was less affected by bump bonding.g.

• 한국소음진동공학회논문집
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• 제20권4호
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• pp.381-389
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• 2010

Modern military equipments are often required to be mounted on a truck for their survivability and operation performance. Special units installed on the truck at times experience serious shock vibration caused by obstacles of road and/or uncommon road shape. It is then essential to analyze the travel performance of truck-mounted special units for their survivability and performance. In this paper, shock responses of the equipments subjected to bump passing and wash board road are experimentally obtained and also analyzed via FEM. Modified bump configuration and road profile considering the interface with tire are suggested. Analytical results considering this modification show good agreement with test results.