• Journal of the Microelectronics and Packaging Society
• /
• v.13 no.3 s.40
• /
• pp.39-45
• /
• 2006

This study was investigated the thermal properties of underfill with various epoxy resins using thermal analysis methods such as differential scanning calorimetry (DSC), thermo gravimetry analysis (TGA), dynamic mechanical analysis (DMA) and thermo-mechanical analysis (TMA). And, the adhesion strength of the underfills/FR-4 substrate was evaluated. The glass transition temperature (Tg) of underfill which was composed the cycolaliphatic epoxy resin was lower than that of underfill which was not composed the cycolaliphatic epoxy resin. The thermal degradation of underfill was composed of two processes, which involved chemical reactions between the degrading polymer and oxygen from the air atmosphere. The coefficient of thermal expansion (CTE) of underfill which was composed the cycolaliphatic epoxy resin was higher than that of underfill which was not composed the cycolaliphatic epoxy resin. The excessive curing temperatures caused a weak boundary layer of epoxy resin, which resulted in a deterioration of mechanical properties in the epoxy resin and thus led to poor adhesion property between the underfill/FR-4 substrate.

• Journal of the Microelectronics and Packaging Society
• /
• v.16 no.3
• /
• pp.39-43
• /
• 2009

In this paper, the flow characteristics of underfill material driven by capillary action between flip-chip and substrate were investigated. Also, the effects of viscosity level and dispensing point of underfill on flow characteristics were investigated. Flip chip package size was $5mm{\times}5mm{\times}0.65^tmm$, the diameter of solder bump was 100 ${\mu}m$, and the pitch was 150 ${\mu}m$. It was full grid area-array type with 1024 I/Os. The glass substrate was used and the gap between the chip and substrate was 50 ${\mu}m$. For the experimental study, three different underfills with different viscous properties($2000{\sim}3700$ cps), and two different types of dispensing methods(center dot and edge dot) were used. The flow characteristics and filling time of underfill were investigated by using CCD camera. The results show that the edge flow was faster than center flow due to the edge effect, which was caused by the resistance of solder bumps. In case of edge dot dispensing type, the filling time was faster due to the large edge effect, compared to center dot dispensing type. Also, it was found that the underfill flow was faster and the filling time decreased as the viscosity level of underfill was decreased.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
• /
• 2002.11a
• /
• pp.64-68
• /
• 2002

플립칩 공정에서는 반도체 칩과 기판사이의 열팽창계수(CTE : Coefficient of Thermal Expansion)의 차와 외적 충격과 같은 이유로 인해 피로균열(Fatigue crack)이나 치명적인 전기적 결함이 발생하게 된다. 이런 부정적인 요인들로부터 칩을 보호하고 신뢰성을 향상시키기 위해서 플립칩 언더필 공정이 적용되고 있다. 본 연구에서는 기존의 몰딩 공정을 응용한 플립칩 언디필 방법을 소개하였다. 공정 이론과 디바이스를 소개하였으며, 시뮬레이션 및 수식을 통하여 최적의 언더필을 위한 몰더 설계 조건을 구하였다. 그리고 본 연구를 통해 기대되는 공정의 장점을 제시하였다.

• Journal of the Microelectronics and Packaging Society
• /
• v.9 no.4
• /
• pp.35-45
• /
• 2002

The stresses of the underfill/chip interface due to thermal loading was studied using the finite element method. At first, the effective properties of underfill for several volume fractions of silica particles were calculated by Mori-Tanaka method for three different material sets, and the parameters of singularity for the bimaterial edge and the bimaterial wedge were calculated. Consequently, the stresses at the underfill/chip interface with volume fraction of silica particles were investigated. Five different geometric models of flip-chip assembly involving two kinds of bimaterial strips and three kinds of three-layer models were considered under the assumption that the underfill is homogeneous. It was assumed that all components of the flip-chip assembly were linear elastic and isotropic, and their properties were temperature independent. The analysis was conducted in the context of the uncoupled plane thermo-elasticity under a plane strain assumption.

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.4
• /
• pp.351-357
• /
• 2013

In flip chip packaging, underfill process is used to fill epoxy bonder into the gap between a chip and a substrate in order to improve the reliability of electronic devices. Underfill process by capillary motion can give rise to unwanted air void formations since the arrangement of solder bumps affects the interfacial dynamics of flow meniscus. In this paper, the unsteady flows in the capillary underfill process are visualized and then the racing effect and merging of the meniscus are investigated according to the arrangement of solder bumps. The result is shown that at higher bump density, the fluid flow perpendicular to the main direction of flow becomes stronger so that more air voids are formed. This phenomenon is more conspicuous at a staggered bump array than at a rectangular bump array.

• Journal of the Semiconductor & Display Technology
• /
• v.1 no.1
• /
• pp.29-33
• /
• 2002

In the flip-chip process, the problem like electric defect or fatigue crack caused by the difference of CTE, between chip and substrate board had occurred. Underfill of flip chip to overcome this defects is noticed as important work developing in whole reliability of chip by protecting the chip against the external shock. In this paper, we introduce the underfill methods using mold and plunge and improvement of process and reliability, and the advantage which can be taken from embodiment of device.

• The Journal of the Korean life insurance medical association
• /
• v.22
• /
• pp.121-137
• /
• 2003

현행 생명보험업계는 중복가입계약에 대한 정보교환제도를 시행함으로써 잠재적 위험에 대한 위험평가를 하고는 있으나 실제 언더라이팅 과정에서는 효율적인 활용을 못하고 있다. 따라서 언더라이팅 실무 입장에서 현행 정보교환제도의 문제점을 파악하고 각 보험회사가 취할 수 있는 효율적인 대응방안을 제시할 필요성이 대두되고 있다. 현행 정보교환제도의 문제점을 크게 몇가지로 나눌 수 있다. - 교환기준에 미달하는 다수의 계약건을 가입한 경우 위험평가 불가 - 위험평가상 고지의무에 충실한 계약자의 상대적 불리 - 정해진 기준과 다른 임의적 기준적용 등 선별적 자료교환으로 위험선택에서 배제된 잠재적 위험들의 계속적인 계약 및 지급 등 역선택 방조기능 - 실시간 반영된 정보부재 및 교환된 자료만으로 one-stop 위험평가를 할 수 없는 어려움 내재 - 정보교환에 대한 전체적 참여노력 부족 및 자기정보에 대한 방어와 자체 활용 이런 문제점들을 인식하고 이에 대한 효율적 대응방안을 제시해 본다. - 언더라이팅 측면에서 판매채널 다변화, 업무겸업화 둥 대외 환경변화에 따른 위험분석 및 평가, 위험분산을 위한 multi-player로서의 언더라이터 양성 필요 - 지급, 조사건의 분석 및 통계화 등 feed back 기능 강화통한 언더라이팅 활용 - 방문진단 통한 적부기능 활용 또는 모집자 사정평점제 등 언더라이팅 과정에서 활용할 수 있는 위험평가 자료축적 - 영업환경적 측면에서 고보장 상품의 경쟁적인 개발제한 - 정보교환제도 측면에서 정보교환 기준 변경 및 교환내용 추가 및 공동의 계약인수 guideline 필요 - 진단거절체, 표준미달체, 사절체 등 새로운 정보교환의 추진 필요 - 종합적인 피보험자의 정보를 획득할 수 있는 피보험자 종합정보의 데이터 구축 및 활용 효율적인 위험관리 외에도 각 보험회사별로 역선택 위험에 대한 심각성을 인식하고 업계간 정보교환에 적극적인 참여와 노력이 필요하며 잠재적 위험평가를 하는데 있어 계약자에게는 객관적 근거없이 불편을 갖지 않도록 언더라이팅 서비스하는 것 또한 중요하다. 지속적인 피보험자의 위험통계축적으로 잠재위험에 대한 보다 객관화된 위험평가를 할 수 있는 언더라이팅 기법을 체득함으로써 언더라이팅 경쟁력을 갖을 수 있다.

• Journal of the Microelectronics and Packaging Society
• /
• v.18 no.4
• /
• pp.19-25
• /
• 2011

The size reduction of the semiconductor chip and the improvement of the electrical performance have been enabled through the introduction of the Cu/Low-K process in modern electronic industries. However, Cu/Low-K has a disadvantage of the physical properties that is weaker than materials used for existing semiconductor manufacture process. It causes many problems in chip manufacturing and package processes. Especially, the delamination between the Cu layer and the low-K dielectric layer is a main defect after the temperature cycles. Since the Cu/Low-K layer is located on the top of the pad of the flip chip, the stress on the flip chip affects the Cu/Low-K layer directly. Therefore, it is needed to improve the underfill process or materials. Especially, it becomes very important to select the underfill to decrease the stress at the flip-chip and to protect the solder bump. We have solved the delamination problem in a 90 nm Cu/Low-K flip-chip package after the temperature cycle by selecting an appropriate underfill.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2004.11a
• /
• pp.56-56
• /
• 2004

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.19 no.2
• /
• pp.157-162
• /
• 2010

This paper describes the thermal fatigue life prediction models for 95.5Sn-4.0Ag-0.5Cu solder joints of Flip chip package considering Under Bump Metallurgy(UBM). A 3D Finite element slice model was used to simulate the viscoplastic behavior of the solder. For two types of solder bump pitches, simulations were analyzed and the effects of underfill packages were studied. Consequently, it was found out that solder joints with underfill had much better fatigue life than solder joints without underfill, and solder joints with $300{\mu}m$ bump pitch had a longer thermal fatigue life than solder joints with $150{\mu}m$ bump pitch. Through the simulations, flip chip with lead-free solder joints should be designed with underfill and a longer bump pitch.