• Journal of the Microelectronics and Packaging Society
• /
• v.25 no.1
• /
• pp.41-45
• /
• 2018

As the size of semiconductor chip shrinks, the electronic industry has been paying close attention to fan-out wafer level packaging (FO-WLP) as an emerging solution to accommodate high input and output density. FO-WLP also has several advantages, such as thin thickness and good thermal resistance, compared to conventional packaging technologies. However, one major challenge in current FO-WLP manufacturing process is to control wafer warpage, caused by the difference of coefficient of thermal expansion and Young's modulus among the materials. Wafer warpage induces misalignment of chips and interconnects, which eventually reduces product quality and reliability in high volume manufacturing. In order to control wafer warpage, it is necessary to understand the effect of material properties and design parameters, such as chip size, chip to mold ratio, and carrier thickness, during packaging processes. This paper focuses on the effects of thickness of chip and molding compound on 12" wafer warpage after PMC of EMC using finite element analysis. As a result, the largest warpage was observed at specific thickness ratio of chip and EMC.

• Journal of the Microelectronics and Packaging Society
• /
• v.22 no.1
• /
• pp.35-41
• /
• 2015

In this study, in order to improve the reliability of ACF interconnections, solder ACF joints were investigated interms of solder joint morphology and solder wetting areas, and evaluated the electrical properties of Flex-on-Board (FOB) interconncections. Solder ACF joints with the ultrasonic bonding method showed excellent solder wetting by broken solder oxide layers on solder surfaces compared with solder joints with remaining solder oxide layer bonded by the conventional thermo-compression (TC) bonding method. When higher target temperature was used, Sn58Bi solder joints showed concave shape due to lower degree of cure of resin at solder MP by higher heating rate. ACFs with epoxy resins and SAC305 solders showed lower degree of resin cure at solder MP due to the slow curing rate resulting in concave shaped solder joints. In terms of solder wetting area, solder ACFs with $25-32{\mu}m$ diameters and 30-40 wt% showed highest wetted solder areas. Solder ACF joints with the concave shape and the highest wetting area showed lower contact resistances and higher reliability in PCT results than conventional ACF joints. These results indicate that solder morphologies and wetting areas of solder ACF joints can be controlled by adjustment of bonding conditions and material properties of solder and polymer resin to improve reliability of ACF joints.

• Journal of the Microelectronics and Packaging Society
• /
• v.10 no.3
• /
• pp.43-55
• /
• 2003

As the development of If industries and their electronic device manufacturing technology have been accelerated recently, the request for electronic devices with small size, light weight, and high performance has been inducing that electronic package and substrate (PCB) companies have to develop substrates with low cost, high dense I/O, excellent thermal properties and electrical properties. Therefore, world-wide chip makers have been setting their own severe reliability standards and requiring their suppliers to keep specification and to develop green, high frequency and high-performing substrates. Because properties of substrates are dependent mainly on their constituent materials, the application of them showing superior properties is expected to satisfy the customer's requirement. Therefore, substrate companies should ensure the superiority of materials and assure their competitive capability of substrates by analyzing the latest trends of technology and properties of the materials.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.9
• /
• pp.1408-1414
• /
• 2004

The use of flip-chip technology has many advantages over other approaches for high-density electronic packaging. ACF (anisotropic conductive film) is one of the major flip-chip technologies, which has short chip-to-chip interconnection length, high productivity, and miniaturization of package. In this study, thermal fatigue lift of ACF bonding flip-chip package has been predicted. Elastic and thermal properties of ACF were measured by using DMA and TMA. Temperature dependent nonlinear hi-thermal analysis was conducted and the result was compared with Moire interferometer experiment. Calculated displacement field was well matched with experimental result. Thermal fatigue analysis was also conducted. The maximum shear strain occurs at the outmost located bump. Shear stress-strain curve was obtained to calculate fatigue life. Fatigue model for electronic adhesives was used to predict thermal fatigue life of ACF bonding flip-chip packaging. DOE (Design of Experiment) technique was used to find important design factors. The results show that PCB CTE (Coefficient of Thermal Expansion) and elastic modulus of ACF material are important material parameters. And as important design parameters, chip width, bump pitch and bump width were chose. 2$^{nd}$ DOE was conducted to obtain RSM equation far the choose 3 design parameter. The coefficient of determination ($R^2$) for the calculated RSM equation is 0.99934. Optimum design is conducted using the RSM equation. MMFD (Modified Method for feasible Direction) algorithm is used to optimum design. The optimum value for chip width, bump pitch and bump width were 7.87mm, 430$\mu$m, and 78$\mu$m, respectively. Approximately, 1400 cycles have been expected under optimum conditions. Reliability analysis was conducted to find out guideline for control range of design parameter. Sigma value was calculated with changing standard deviation of design variable. To acquire 6 sigma level thermal fatigue reliability, the Std. Deviation of design parameter should be controlled within 3% of average value.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.412-412
• /
• 2008

ENIG(Electroless Nickel Immersion Gold)is a surface treatment method that is used most widely at fine pitch's SMT and BGA packaging process. ENIG has good diffusion barrier of Ni against solder and good wettability due to Au finish. But when the discoloration occurred on the Au finish of ENIG, some key characteristics related to the quality and reliability of PCB such as bondability, solderability and electrical flowing of packaging process could be deteriorated. In this paper, we have performed the water dip test ($88^{\circ}C$ purified water) which accelerates the galvanic corrosion of Ni diffused from the Ni-P layer. That is, the excessive oxidation of the Ni layer could result in non-wetting of the solder because the flux may not be able to remove excessive oxides. Though Au discoloration have been reported to be caused by Ni oxides in many literature, it is still open to verify and discuss The microstructures and chemical compositions have been investigated using FE-SEM, TEM, FIB, EDS and XPS. As a result, authors have found that the Au discoloration in ENIG type is severely caused by the oxidation of the Ni and the mechanism of Au discoloration can be confirmed through the experiment result of water dip test.

• Korean Chemical Engineering Research
• /
• v.46 no.2
• /
• pp.402-407
• /
• 2008

Recent popularity in mobile electronics requires higher standard on the mechanical strength of electronic packaging. Thus, the method of soldering between chip and substrate in electronic packaging process is changing from conventional method using intermetallic compound to a new method using organic solderability preservative (OSP) in order to improve the stability and the reliability of final product. Since current organic solder preservatives have several serious problems like thermo-stability during packaging process, however, it is necessary to develop new OSPs having thermo-stability. The main purpose of this study is to investigate the effect of MeOH/IPA (Isopropyl alcohol) ratio on the fluxing of a new OSP, developed in previous research, andto find out an optimum formulation of flux components for the application of the OSP in current packaging process. As a result of this study, it was revealed that higher MeOH/IPA ratio in flux showed better performance of fluxing a new OSP.

• Electrical & Electronic Materials
• /
• v.7 no.6
• /
• pp.527-533
• /
• 1994

In this study, it was studied on dielectric breakdown strength and thennostability properties due to the structure variation of matrix resin and treatment of coupling agent of epoxy insulating materials. The interpenetrating network structure was formed by simultaneous heating curing the epoxy resin with single network structure and the methacrylic acid resin. Also inner structure was observed and the glass transition temperature was measured on these three type specimens. Dielectric breakdown properties were investigated by applying DC, AC and impulse voltage. As a result, the glass transition temperature and the dielectric breakdown strength of specimen with interpenetrating network structure was more higher than another two type specimens.

• Proceedings of the KWS Conference
• /
• 2003.05a
• /
• pp.224-227
• /
• 2003

The longitudinal thermosonic bonding method is investigated in this work for its application to the soldering process for electronic packaging. The effect of the ultrasonic is analyzed through lumped modeling, and the material properties of a viscoelastic model are measured experimentally. The thermosonic bonding method is verified by inserting the Cu pin and Au bump into solder block. As the solder thickness decreases, temperature of the solder is calculated to increase rapidly because of larger strain. Localized heating due to ultrasonic vibration is observed to melt the solder near the pin, which is adequate to the high density electronic package and Pb-free solder having high melting temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.24-24
• /
• 2009

ENIG(Electroless Nickel Immersion Gold) is the surface treatment method that is used most widely at fine pitch's SMT and BGA packaging process. In this paper, we have studied the effect of P content variation during ENIG process on those phenomena related to the solder joint. The effect of P content was discussed using the results obtained from FE-SEM, EPMA, EDS and FIB. Finally, it was concluded that the more P-content in Ni layer, the thicker P-rich layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.178-178
• /
• 2009

전자제품의 고속화, 고집적화, 고성능이 요구되어짐에 따라 IC's 성능 향상을 통해 패키징 기술의 소형화를 필요로 하고 있어 소재나 칩 부품을 이용해 커패시터나 저항을 구현하여 내장시키는 임베디드 패시브 기술에 대한 연구가 많이 진행되어 지고 있다. 본 연구에서는 3D 패키징이 가능한 flexible 소재에 능, 수동 소자를 내장하기 위한 다층 flexible 기판 공정 기술에 대한 연구를 수행하였다. 기판제작을 위해 flexible 소재에 미세 형성이 가능한 폴리머 필름을 접착하였고 flexible 위에 후막 저항체 패턴을 퍼|이스트를 이용하여 형성하였다. 또한, 능동소자 내장을 위해 test chip을 제작하여 플립칩 본더를 이용해 flexible 기판에 접합한 후에 bonding film을 이용한 build up 공정을 통해 via를 형성하고 무전해 도금 공정을 거쳐 전기적인 연결을 하였다. 위의 공정을 통해 앓고 가벼울 뿐만 아니라 자유롭게 구부러지는 특성을 갖고 있는 능, 수동 소자 내장형 flexible 기판의 변형에 따른 전기적 특성을 평가하였다.