• 한국생산제조학회지
• /
• 제20권5호
• /
• pp.559-563
• /
• 2011

Drop impact reliability assessment of solder joints on the flip chip is one of the critical issues for micro system packaging. Our previous researches have been showing that new solder ball compositions of Sn-3.0Ag-0.5Cu has better mechanical reliability than Sn-1.0Ag-0.5Cu. In this paper, dynamic reliability analysis using Finite Element Analysis (FEA) is carried out to assess the factors affecting flip chip in drop simulation. The design parameters are size and thickness of chip, and size, pitch and array of solder ball with composition of Sn1.0Ag0.5Cu. The board systems by JEDEC standard including 15 chips, solder balls and PCB are modeled with various design parameter combinations, and through these simulations, maximum yield stress and strain at each chip are shown at the solder balls. It is found that larger chip size, smaller chip array, smaller ball diameter, larger pitch, and larger chip thickness have bad effect on maximum yield stress and strain at solder ball of each chip.

• 마이크로전자및패키징학회지
• /
• 제15권4호
• /
• pp.9-15
• /
• 2008

Au와 Sn을 순차적으로 도금한 Au/Sn 범프를 플립칩 본딩하여 Au-Sn 솔더 접속부를 형성 후, 미세구조와 접속저항을 분석하였다. $285^{\circ}C$에서 30초간 플립칩 본딩한 Au-Sn 솔더 접속부는 $Au_5Sn$+AuSn lamellar 구조로 이루어져 있으며, 이 시편을 $310^{\circ}C$에서 3분간 유지하여 2차 리플로우시 $Au_5Sn$+AuSn interlamellar spacing이 증가하였다. $285^{\circ}C$에서 30초간 플립칩 본딩한 Au-Sn 접속부는 15.6 $m{\Omega}$/bump의 평균 접속저항을 나타내었으며, 이 시편을 다시 $310^{\circ}C$에서 3분간 유지하여 2차 리플로우 한 Au-Sn 접속부는 15.0 $m{\Omega}$/bump의 평균 접속저항을 나타내었다.

• 마이크로전자및패키징학회지
• /
• 제17권3호
• /
• pp.27-32
• /
• 2010

Cu pillar 범프와 Sn 패드로 구성된 플립칩 접속부를 형성한 후, Sn 패드의 높이에 따른 Cu pillar 플립칩 접속부의 열 싸이클링 및 고온유지 신뢰성을 분석하였다. Cu pillar 플립칩 접속부를 구성하는 Sn 패드의 높이가 5 ${\mu}m$에서 30 ${\mu}m$로 증가함에 따라 접속저항이 31.7 $m{\Omega}$에서 13.8 $m{\Omega}$로 감소하였다. $-45^{\circ}C{\sim}125^{\circ}C$ 범위의 열 싸이클을 1000회 인가한 후에도 Cu pillar 플립칩 접속부의 접속저항의 증가가 12% 이하로 유지되었으며, 열 싸이클링 시험전과 거의 유사한 파괴 전단력을 나타내었다. $125^{\circ}C$에서 1000 시간 유지시에도 Cu pillar 플립칩 접속부의 접속저항의 증가가 20% 이하로 유지되었다.

• 한국마이크로전자및패키징학회:학술대회논문집
• /
• 한국마이크로전자및패키징학회 2001년도 Proceedings of 6th International Joint Symposium on Microeletronics and Packaging
• /
• pp.35-43
• /
• 2001

Flip chip assembly on organic substrates using ACAs have received much attentions due to many advantages such as easier processing, good electrical performance, lower cost, and low temperature processing compatible with organic substrates. ACAs are generally composed of epoxy polymer resin and small amount of conductive fillers (less than 10 wt.%). As a result, ACAs have almost the same CTE values as an epoxy material itself which are higher than conventional underfill materials which contains lots of fillers. Therefore, it is necessary to lower the CTE value of ACAs to obtain more reliable flip chip assembly on organic substrates using ACAs. To modify the ACA composite materials with some amount of conductive fillers, non-conductive fillers were incorporated into ACAs. In this paper, we investigated the effect of fillers on the thermo-mechanical properties of modified ACA composite materials and the reliability of flip chip assembly on organic substrates using modified ACA composite materials. Contact resistance changes were measured during reliability tests such as thermal cycling, high humidity and temperature, and high temperature at dry condition. It was observed that reliability results were significantly affected by CTEs of ACA materials especially at the thermal cycling test. Results showed that flip chip assembly using modified ACA composites with lower CTEs and higher modulus by loading non-conducting fillers exhibited better contact resistance behavior than conventional ACAs without non-conducting fillers. Microwave model and high-frequency measurement of the ACF flip-chip interconnection was investigated using a microwave network analysis. ACF flip chip interconnection has only below 0.1nH, and very stable up to 13 GHz. Over the 13 GHz, there was significant loss because of epoxy capacitance of ACF. However, the addition of $SiO_2filler$ to the ACF lowered the dielectric constant of the ACF materials resulting in an increase of resonance frequency up to 15 GHz. Our results indicate that the electrical performance of ACF combined with electroless Wi/Au bump interconnection is comparable to that of solder joint.

• 마이크로전자및패키징학회지
• /
• 제10권4호
• /
• pp.81-86
• /
• 2003

상부 칩과 하부 기판이 모두 Si으로 구성되어 있는 플립칩 패키지 시편을 제조하여 Sn-3.5Ag 솔더범프의 electromigration 거동을 분석하였다. Sn-3.5Ag 솔더범프의 electromigration 테스트 초기부터 파단이 일어나기 직전까지는 플립칩 시편의 저항이 거의 변하지 않았으나, 파단이 발생하는 순간 저항값이 크게 증가하였다. 전류밀도 $3\times 10^4$∼$4\times 10^4$A/$\textrm{cm}^2$에서 Sn-3.5Ag 솔더범프의 electromigration에 대한 활성화 에너지는 ∼0.7 eV로 분석되었다. Sn-3.5Ag 솔더범프의 cathode 부위의 솔더/UBM 계면에서 void의 형성 및 전파에 의해 솔더범프의 파단이 발생하였다.

• 한국마이크로전자및패키징학회:학술대회논문집
• /
• 한국마이크로전자및패키징학회 2002년도 International Symposium
• /
• pp.97-120
• /
• 2002

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
• /
• pp.10-10
• /
• 2008

Flip chip technology is keeping pace with the increasing connection density of the ICs and is capable of transferring semiconductor performance to the printed circuit board. One of the most general flip chip technology is CPB technology presented by Intel. The CPTB technology has similar benefits with CPB but has simpler process and better reliability characteristics. In this paper, process sequence and structure of CPTB are presented.

• 한국공작기계학회논문집
• /
• 제16권5호
• /
• pp.134-139
• /
• 2007

This paper presents a computer-based analysis on the thermal shock characteristics of Pb-free solder joints and UBM in flip chip assemblies. Among four types of popular UBM systems, TiW/Cu system with 95.5Sn-3.9Ag-0.6Cu solder joints was chosen for simulation. A simple 3D finite element model was first created only including silicon die, mixture between underfill and solder joints, and substrate. The displacements due to CTE mismatch between silicon die and substrate was then obtained through FE analysis. Finally, the obtained displacements were applied as mechanical loads to the whole 2D FE model and the characteristics of flip chip assemblies were analyzed. In addition, based on the hyperbolic sine law, the accumulated creep strain of Pb-free solder joints was calculated to predict the fatigue life of flip chip assemblies under thermal shock environments. The proposed method for fatigue life prediction will be evaluated through the cross check of the test results in the future work.

• 마이크로전자및패키징학회지
• /
• 제10권3호
• /
• pp.9-17
• /
• 2003

In this paper, thermo-mechanical and rheological properties of NCPs (Non-Conductive Pastes) depending on silica filler contents and diluent contents were investigated. And then, thermal cycling (T/C) reliability of flip chip assembly using selected NCPs was verified. As the silica filler content increased, thermo-mechanical properties of NCPs were changed. The higher the silica filler content was added, glass transition temperature ($T_g$) and storage modulus at room temperature became higher. While, coefficient of thermal expansion (CTE) decreased. On the other hand, rheological properties of NCPs were significantly affected by diluent content. As the diluent content increased, viscosity of NCP decreased and thixotropic index increased. However, the addition of diluent deteriorated thermo-mechanical properties such as modulus, CTE, and $T_g$. Based on these results, three candidates of NCPs with various silica filler and diluent contents were selected as adhesives for reliability test of flip chip assemblies. T/C reliability test was performed by measuring changes of NCP bump connection resistance. Results showed that flip chip assembly using NCP with lower CTE and higher modulus exhibited better T/C reliability behavior because of reduced shear strain in NCP adhesive layer.

• 한국재료학회지
• /
• 제20권12호
• /
• pp.681-685
• /
• 2010

The application of flip chip technology has been growing with the trend of miniaturization of electronic packages, especially in mobile electronics. Currently, several types of adhesive are used for flip chip bonding and these adhesives require some special properties; they must be solvent-free and fast curing and must ensure joint reliability against thermal fatigue and humidity. In this study, imidazole and its derivatives were added as curing catalysts to epoxy resin and their effects on the adhesive properties were investigated. Non-isothermal DSC analyses showed that the curing temperatures and the heat of reaction were dependent primarily on the type of catalyst. Isothermal dielectric analyses showed that the curing time was dependent on the amount of catalysts added as well as their type. The die shear strength increased with the increase of catalyst content while the Tg decreased. From this study, imidazole catalysts with low molecular weight are expected to be beneficial for snap curing and high adhesion strength for flip chip bonding applications.