The Experts below are selected from a list of 645 Experts worldwide ranked by ideXlab platform
Kyung-wook Paik - One of the best experts on this subject based on the ideXlab platform.
-
Woon-Seong Kwon Thermal Cycling Reliability and Delamination of Anisotropic Conductive Adhesives Flip Chip on Organic Substrates With Emphasis on the Thermal Deformation
2020Co-Authors: Myung-jin Yim, Kyung-wook Paik, Suk-jin Ham, Mems Lab, Soon-bok LeeAbstract:One of the most important issues whether Anisotropic Conductive Film (ACF) interconne
-
Mechanism of Solder Joint Cracks in Anisotropic Conductive Films Bonding and Solutions: Delaying Hot-Bar Lift-Up Time and Adding Silica Fillers
MDPI AG, 2018Co-Authors: Shuye Zhang, Ming Yang, Mingliang Jin, Wen-can Huang, Tiesong Lin, Panpan Lin, Kyung-wook PaikAbstract:Micron sizes solder metallurgical joints have been applied in a thin Film application of Anisotropic Conductive Film and benefited three general advantages, such as lower joint resistance, higher power handling capability, and reliability, when compared with pressure based contact of metal conductor balls. Recently, flex-on-board interconnection has become more and more popular for mobile electronic applications. However, crack formation of the solder joint crack was occurred at low temperature curable acrylic polymer resins after bonding processes. In this study, the mechanism of SnBi58 solder joint crack at low temperature curable acrylic adhesive was investigated. In addition, SnBi58 solder joint cracks can be significantly removed by increasing the storage modulus of adhesives instead of coefficient of thermal expansion. The first approach of reducing the amount of polymer rebound can be achieved by using an ultrasonic bonding method to maintain a bonding pressure on the SnBi58 solder joints cooling to room temperature. The second approach is to increase storage modulus of adhesives by adding silica filler into acrylic polymer resins to prevent the solder joint from cracking. Finally, excellent acrylic based SnBi58 solder joints reliability were obtained after 1000 cycles thermal cycling test
-
a study on the failure mechanism and enhanced reliability of sn58bi solder Anisotropic Conductive Film joints in a pressure cooker test due to polymer viscoelastic properties and hydroswelling
IEEE Transactions on Components Packaging and Manufacturing Technology, 2016Co-Authors: Shuye Zhang, Kyung-wook PaikAbstract:A study of the failure mechanism and the enhanced reliability performance of SnBi58 solder ACF joints were investigated by considering the total influence of polymer viscoelastic and hygroscopic properties on the cross-sectional morphologies and the electrical properties of Sn58Bi solder joints in a pressure cooker test (PCT) for 120 h. The Sn58Bi solder failure mechanism is demonstrated that, when polymer resin absorbed moisture, the $T_{g}$ values of polymer resins decreased, and the coefficient of thermal expansion (CTE) values of polymer resins increased, due to a hydroswelling effect. Considering the total influence of polymer viscoelastic and hygroscopic properties on the cross-sectional morphologies and the reliability of Sn58Bi solder joints in a PCT for 120 h, four typical polymer resins were evaluated. As a result, cationic epoxy (128 ppm/°C) with the smallest CTE mismatch (112 ppm/°C) with SnBi58 solder joints (16 ppm/°C) in a PCT aging test (121 °C, 100% humidity, and 2 atm) showed a stable electrical property in terms of joint contact resistance and remained a complete cross-sectional Sn58Bi solder joint morphology after PCT reliability for 120 h.
-
A Study on the Solder Ball Size and Content Effects of Solder ACFs for Flex-on-Board Assembly Applications Using Ultrasonic Bonding
IEEE Transactions on Components Packaging and Manufacturing Technology, 2015Co-Authors: Shuye Zhang, Kyung-wook PaikAbstract:In this paper, the electrical and reliability properties of various solder Anisotropic Conductive Film (ACF) joints for flex-on-board (FOB) assembly using ultrasonic bonding were assessed in terms of short circuits, contact resistance, current handling capability, wetted solder areas, and reliability evaluation. It was found that the wetted solder areas increased and reliability was enhanced as the size and content of the solder ball increased. Regardless of solder ball size and content, the contact resistances of solder ACF joints were almost the same, because the current went through the electrode/electrode contact, which is like a short circuit to the solder joint. In addition, the exact value of current handling capability of all the ACF joints could not be evaluated, because metal lines of printed circuit board were burnt before ACF joint failure. After 120 h of pressure cooker test (PCT), the open-circuit failures were mainly observed at Ni ACFs, and 5-15-μm solder ball size from 10 to 30 wt% solder content and 25-32-μm size and 10 wt% solder content of solder ACFs, presumably due to lower wetted solder areas on metal electrodes. In addition, the crack was noted after 120 h of PCT in the solder ACF joints who has lower wetted solder areas. As a result of this paper, the solder ball size and content of solder ACFs joints were optimized at 25-32-μm sizes and above 30 wt% content for 300-μm pitch FOB assembly.
-
study on fine pitch flex on flex assembly using nanofiber solder Anisotropic Conductive Film and ultrasonic bonding method
IEEE Transactions on Components Packaging and Manufacturing Technology, 2012Co-Authors: Sang Hoo Lee, Kyunglim Suk, Ki Wo Lee, Kyung-wook PaikAbstract:A new concept of Anisotropic Conductive Film (ACF) called nanofiber/solder ACF combined with an ultrasonic bonding method can overcome limitations of fine pitch flex-on-flex (FOF) assembly using conventional ACF, such as short circuit issues, low current-handling capability, and poor reliability. To fabricate the nanofiber/solder ACF, SAC305 (96.5% Sn, 0.5% Cu, and 3% Ag) Conductive solder balls are added to polyacrylonitrile polymer solution and ejected as nanofibers containing SAC305 Conductive solder balls by an electrospinning method. This new concept of nanofiber/solder ACF successfully prevents short circuits between neighboring conducting electrodes by limiting the free movement of conducting balls and insulating individual Conductive solder balls with coated nanofiber layers. Moreover, SAC305 Conductive solder balls in nanofiber/solder ACF are completely melted and made metallurgical alloy contact between FOF electrodes during the ultrasonic bonding, resulting in 41% more electrical power being carried, and showing significant improvement in reliability performance compared with conventional nickel ball ACF.
Myung-jin Yim - One of the best experts on this subject based on the ideXlab platform.
-
Woon-Seong Kwon Thermal Cycling Reliability and Delamination of Anisotropic Conductive Adhesives Flip Chip on Organic Substrates With Emphasis on the Thermal Deformation
2020Co-Authors: Myung-jin Yim, Kyung-wook Paik, Suk-jin Ham, Mems Lab, Soon-bok LeeAbstract:One of the most important issues whether Anisotropic Conductive Film (ACF) interconne
-
Highly Reliable Flip-Chip-on-Flex Package Using Multilayered Anisotropic Conductive Film
2016Co-Authors: Myung-jin Yim, Jin-sang Hwang, Jin Gu Kim, Jin Yong AhnAbstract:Anisotropic Conductive lm (ACF) has been used as interconnect material for at-panel display module packages, such as liquid crystal displays (LCDs) in the technologies of tape automated bonding (TAB), chip-on-glass (COG), chip-on-lm (COF), and chip-on-board (COB). Among them, COF is a relatively new technology after TAB and COG bonding, and its requirement for ACF becomes more stringent because of the need of high adhesion and ne-pitch interconnec-tion. To meet these demands, strong interfacial adhesion between the ACF, sub-strate, and chip is a major issue. We have developed a multilayered ACF that has functional layers on both sides of a conventional ACF layer to improve the wetting properties of the resin on two-layer ex for better interface adhesion and to control the ow of Conductive particles during thermocompression bond-ing and the resulting reliability of the interconnection using ACF. To investi-gate the enhancement of electrical properties and reliability of multilayered ACF in COF assemblies, we evaluated the performance in contact resistance and adhesion strength of a multilayered ACF and single-layered ACF unde
-
ultrasonic bonding using Anisotropic Conductive Films acfs for flip chip interconnection
IEEE Transactions on Electronics Packaging Manufacturing, 2009Co-Authors: Ki Won Lee, Myung-jin Yim, Hyoungjoon Kim, Kyung-wook PaikAbstract:In this paper, a novel Anisotropic Conductive Film (ACF) flip chip bonding method using ultrasonic vibration for flip chip interconnection is demonstrated. The curing and bonding behaviors of ACFs by ultrasonic vibration were investigated using a 40-kHz ultrasonic bonder with longitudinal vibration. In situ temperature of the ACF layer during ultrasonic (U/S) bonding was measured to investigate the effects of substrate materials and substrate temperature. Curing of the ACFs by ultrasonic vibration was investigated by dynamic scanning calorimetry (DSC) analysis in comparison with isothermal curing. Die adhesion strength of U/S-bonded specimens was compared with that of thermo-compression (T/C) bonded specimens. The temperature of the ACF layer during U/S bonding was significantly affected by the type of substrate materials rather than by the substrate heating temperature. With room the temperature U/S bonding process, the temperature of the ACF layer increased up to 300degC within 2 s on FR-4 substrates and 250degC within 4 s on glass substrates. ACFs were fully cured within 3 s by ultrasonic vibration, because the ACF temperature exceeded 300degC within 3 s. Die adhesion strengths of U/S-bonded specimens were as high as those of T/C bonded specimens both on FR-4 and glass substrates. In summary, U/S bonding of ACF significantly reduces the ACF bonding times to several seconds, and also makes bonding possible at room temperature compared with T/C bonding which requires tens of seconds for bonding time and a bonding temperature of more than 180degC.
-
effect of filler content on the dielectric properties of Anisotropic Conductive adhesives materials for high frequency flip chip interconnection
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2006Co-Authors: Myung-jin Yim, Woonseong Kwon, Kyung-wook PaikAbstract:Abstract The dielectric property of Anisotropic Conductive Film (ACF) as an interconnect materials in the flip–chip joints is becoming important concern for device packaging solution at high-frequency due to low parasitic effect on the signal transfer. The effects of non-Conductive, dielectric filler content on dielectric properties of ACA materials, like dielectric constant, loss factor and loss tangent, and conductivity at high-frequency were investigated. Frequency is dominating factor in determining dielectric constant, loss factor, and conductivity. However, the filler content is dominant only on dielectric constant, not on the loss factor, and conductivity at low-frequency range. The effect of low dielectric constant (low-k) filler addition on high-frequency behavior of ACF interconnection in flip–chip assembly was also investigated. Impedance parameters of low-k ACF with Ni filler and low-k SiO2 filler extracted from measurement were compared with that of conventional ACF with only Ni filler. The resonant frequency of conventional ACF flip–chip interconnect was 13 GHz, while the resonant frequency of low-k ACF including low-k SiO2 filler was found at 15 GHz. This difference is originated from capacitance decrease of polymer matrix between bump and substrate pad due to change in dielectric constant of polymer matrix, which was verified by measurement-based modeling. The high-frequency property of the Conductive adhesive flip–chip joint, such as resonant frequency can be enhanced by low-k polymer matrix.
-
the contact resistance and reliability of Anisotropically Conductive Film acf
Electronic Components and Technology Conference, 1999Co-Authors: Myung-jin Yim, Kyung-wook PaikAbstract:The effect of bonding pressure on the electrical and mechanical properties of Anisotropic Conductive Film (ACF) joint using nickel particles and metal-coated polymer ball-filled ACF's was investigated. The contact resistance decreases as the bonding pressure increases. Contact resistance of ACF is determined by the contact area change between particles and contact substrates. Electrical conduction through the pressure engaged contact area between Conductive particles and conductor substrates is the main conduction mechanism in ACF interconnection. In addition, environmental effects on contact resistance and adhesion strength such as thermal aging, high temperature/humidity aging and temperature cycling were also investigated. Interestingly, the contact resistances of the excessively bonded samples deteriorated more than those of optimally bonded ones. Increasing contact resistance and decreasing adhesion strength after harsh environmental tests were mainly due to the loss of contact by thermal stress effect and moisture absorption, and also partially due to the formation of metal oxide on the Conductive particles.
Young Ho Kim - One of the best experts on this subject based on the ideXlab platform.
-
review paper flip chip bonding with Anisotropic Conductive Film acf and nonConductive adhesive nca
Current Applied Physics, 2013Co-Authors: Sun-chul Kim, Young Ho KimAbstract:Abstract Recently, the flip-chip bonding technology using adhesives has been widely used in the packaging industry because of environmental friendliness (elimination of lead material and flux cleaning), low temperature process (no soldering process), fewer processing steps (no underfill process), and the fine pitch capability. In flip-chip assembly using adhesives, the electrical interconnection is established by mechanical contact between the bumps on the chip and the corresponding pads on the substrate after the adhesive is cured. The adhesive can be categorized into two types with respect to the presence of the Conductive particles: Anisotropic Conductive Film (ACF) and nonConductive adhesive (NCA). ACF is the adhesive polymer Film with dispersed Conductive particles, and NCA is just adhesive which contains no Conductive particles. In this review, the bonding technologies with ACF and NCA are introduced, and the principle and characteristics of each bonding method are discussed.
Yin Chunyan - One of the best experts on this subject based on the ideXlab platform.
-
Macro-micro modelling of moisture induced stresses in an ACF flip chip assembly
'Emerald', 2006Co-Authors: Yin Chunyan, Lu Hua, Bailey Christopher, Chan Y.c.Abstract:Purpose – This paper discusses the use of modelling techniques to predict the reliability of an Anisotropic Conductive Film (ACF) flip chip in a humid environment. The purpose of this modelling work is to understand the role that moisture plays in the failure of ACF flip chips. Design/methodology/approach – A 3D macro-micro finite element modelling technique was used to determine the moisture diffusion and moisture-induced stresses inside the ACF flip chip. Findings – The results show that the ACF layer in the flip chip can be expected to be fully saturated with moisture after 3?h at 121°C, 100%RH, 2?atm test conditions. The swelling effect of the adhesive due to this moisture absorption causes predominately tensile stress at the interface between the adhesive and the metallization, which could cause a decrease in the contact area, and therefore an increase in the contact resistance. Originality/value – This paper introduces a macro-micro modelling technique which enables more detailed 3D modelling analysis of an ACF flip chip than previously
-
Experimental and modelling analysis on the performance of Anisotropic Conductive Films as used in electronics packaging
University of Greenwich, 2006Co-Authors: Yin ChunyanAbstract:The aim of this research is to understand the failure modes and mechanisms of adhesive materials used to flip-chip bond a silicon die onto a polyimide substrate. The bonding material investigated in this research is called Anisotropic Conductive Film (ACF). This is a promising interconnection material and has gained extensive interest in the electronics packaging industry. Both the experimental and finite element analysis (FEA) methods were used in order to investigate the behaviour of the ACF materials when subjected to certain manufacturing and environmental testing conditions. The manufacturing condition investigated was a subsequent solder reflow process on an ACF flip-chip bonded device. The environmental testing condition investigated was the moisture test. For the manufacturing condition, both experimental and modelling results demonstrate the impact of a subsequent reflow process on the behaviour of the ACF joint. Typical failures observed after this process were cracks at the pad/particle interface. This failure mode was more sever with a higher peak reflow temperature. This was also found using FEA where high tensile stresses were predicted in these regions. FEA modelling was also used to help identify the mechanisms leading to these failures. This is primarily due to the Coefficient of Thermal Expansion (CTE) miss-match in the materials and the elastic/plastic deformation behaviour of the Conductive particle. Important design variables that can minimise these failures are the Young’s Modulus and CTE of the adhesive and the height of the hump on the die. For the environmental testing condition, an autoclave test at 121°C, 100%RH and pressure of 2atm was used. More than 85% of the ACF joints failed during the first 24 hours of testing. The failure mode observed was cracking along the interface between the adhesive and substrate and pad. A macro-micro modelling approach was used to help identify the mechanisms leading to these failures. It was found that most of the damage is caused by moisture diffusion and associated swelling. Important design variables that will help minimise this mode of failure are: Coefficient of Moisture Expansion (CME) and Young’s Modulus of the adhesive and the height of the bump on the die
-
Experimental and modelling analysis on the performance of Anisotropic Conductive Films as used in electronics packaging
2006Co-Authors: Yin ChunyanAbstract:The aim of this research is to understand the failure modes and mechanisms of adhesive materials used to flip-chip bond a silicon die onto a polyimide substrate. The bonding material investigated in this research is called Anisotropic Conductive Film (ACF). This is a promising interconnection material and has gained extensive interest in the electronics packaging industry. Both the experimental and finite element analysis (FEA) methods were used in order to investigate the behaviour of the ACF materials when subjected to certain manufacturing and environmental testing conditions. The manufacturing condition investigated was a subsequent solder reflow process on an ACF flip-chip bonded device. The environmental testing condition investigated was the moisture test. For the manufacturing condition, both experimental and modelling results demonstrate the impact of a subsequent reflow process on the behaviour of the ACF joint. Typical failures observed after this process were cracks at the pad/particle interface. This failure mode was more sever with a higher peak reflow temperature. This was also found using FEA where high tensile stresses were predicted in these regions. FEA modelling was also used to help identify the mechanisms leading to these failures. This is primarily due to the Coefficient of Thermal Expansion (CTE) miss-match in the materials and the elastic/plastic deformation behaviour of the Conductive particle. Important design variables that can minimise these failures are the Young’s Modulus and CTE of the adhesive and the height of the hump on the die. For the environmental testing condition, an autoclave test at 121°C, 100%RH and pressure of 2atm was used. More than 85% of the ACF joints failed during the first 24 hours of testing. The failure mode observed was cracking along the interface between the adhesive and substrate and pad. A macro-micro modelling approach was used to help identify the mechanisms leading to these failures. It was found that most of the damage is caused by moisture diffusion and associated swelling. Important design variables that will help minimise this mode of failure are: Coefficient of Moisture Expansion (CME) and Young’s Modulus of the adhesive and the height of the bump on the die.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
-
Moisture Effects on the Reliability of Anisotropic Conductive Film Interconnection for Flip Chip on Flex Applications
'ASME International', 2005Co-Authors: Yin Chunyan, Lu Hua, Bailey Christopher, Chan Yan-cheongAbstract:Anisotropic Conductive Film (ACF) which consists of an adhesive epoxy matrix and randomly distributed Conductive particles are widely used as the connection material for electronic devices with high I/O counts. However, for the semiconductor industry the reliability of the ACF is still a major concern due to a lack of experimental reliability data. This paper reports the investigations into the moisture-induced failures in Flip-Chip-on-Flex interconnections with Anisotropic Conductive Films (ACFs). Both experimental and modeling methods were applied. In the experiments, the contact resistance was used as a quality indicator and was measured continuously during the accelerated tests (autoclave tests). The temperature, relative humidity and the pressure were set at 121°C, 100%RH, and 2atm respectively. The contact resistance of the ACF joints increased during the tests and nearly 25% of the joints were found to be open after 168 hours’ testing time. Visible conduction gaps between the adhesive and substrate pads were observed. Cracks at the adhesive/flex interface were also found. For a better understanding of the experimental results, 3-D Finite Element (FE) models were built and a macro-micro modeling method was used to determine the moisture diffusion and moisture-induced stresses inside the ACF joints. Modeling results are consistent with the findings in the experimental work
-
Effects of solder reflow on the reliability of flip-chip on flex interconnections using Anisotropic Conductive adhesives
'Institute of Electrical and Electronics Engineers (IEEE)', 2004Co-Authors: Yin Chunyan, Lu Hua, Bailey Chris, Chan Yan-cheongAbstract:This work describes the work of an investigation of the effects of solder reflow process on the reliability of Anisotropic Conductive Film (ACF) interconnection for flip-chip on flex (FCOF) applications. Experiments as well as computer modeling methods have been used. The results show that the contact resistance of ACF interconnections increases after the reflow and the magnitude of the increase is strongly correlated to the peak reflow temperature. In fact, nearly 40 percent of the joints are open when the peak reflow temperature is 260°C, while there is no opening when the peak temperature is 210°C. It is believed that the coefficient of thermal expansion (CTE) mismatch between the polymer particle and the adhesive matrix is the main cause of this contact degradation. To understand this phenomenon better, a three-dimensional (3-D) finite element (FE) model of an ACF joint has been analyzed in order to predict the stress distribution in the Conductive particles, adhesive matrix and metal pads during the reflow process. The stress level at the interface between the particle and its surrounding materials is significant and it is the highest at the interface between the particle and the adhesive matrix
Y C Chan - One of the best experts on this subject based on the ideXlab platform.
-
Effects of bonding parameters on the reliability performance of Anisotropic Conductive adhesive interconnects for Flipchip-on-flex packages assembly II. Different bonding pressure,” Microelectronics Reliability 42 (2002) 1195–1204
2020Co-Authors: Y C Chan, D Y LukAbstract:Abstract The effects of different bonding pressure during flip-chip-on-flex (FCOF) assembly in relation to the performance of Anisotropic Conductive Film (ACF) interconnect were investigated. Two types of ACF were used in this study. ACF 1 is designed to create good interconnection when the connecting bumps and pads are in close contact while ACF 2 can give good connections when the Conductive particles are in contact with the bumps and pads, hence the deformation of Conductive particles within ACF 2 FCOF packages were less than that within ACF 1 packages. ACF 2 gave much better interconnection performance when compared to ACF 1 indicating that ACF 2 is more flexible and can tolerate a wider range of bonding pressure
-
RLC effects in fine pitch Anisotropic Conductive Film connections
2006Co-Authors: Guangbin Dou, Y C Chan, J.e. Morris, David WhalleyAbstract:The resistance, capacitance and inductance of Anisotropic Conductive Film (ACF) connections determine their high frequency electrical characteristics. The presence of capacitance and inductance in the ACF joint contributes to time delays and crosstalk noise as well as simultaneous switching noise (SSN) within the circuit. The purpose of this paper is to establish an experimental method for estimating the capacitance and inductance of a typical ACF connection. This can help to provide a more detailed understanding of the high frequency performance of ACF assemblies. Design/methodology/approach Experiments on the transient response of an ACF joint were performed using a digital oscilloscope capable of achieving the required ns resolution. An equivalent circuit model is proposed in order to quantify the capacitance (C) and inductance (L) of a typical ACF connection and this model is fitted to the experimental data. The equivalent model consisted of two resistors, an inductor, and a capacitor. Findings The capacitance and inductance of a typical ACF connection were estimated from the measured transient response using Kirchhoff's Voltage Law. The method for estimation of R, L, and C from the transient response is discussed, as are the RLC effects on the high frequency electrical characteristics of the ACF connection. Research limitations/implications There was decay time deviation between the calculation and the experiment. It may be resulted from the skin effect in the high frequency response and the adhesive surrounding joint as well. The main reason may be the capacitance dielectric lost. Further research work will be done to test the dielectric lost in the ACA joint. What is original/value of paper This paper presents a new method to characterise the high frequency properties of ACA interconnections and will be of use to engineers evaluating the performance of ACF materials in high frequency applications
-
Macro-Micro Modeling Analysis for High Density Packaged Flip Chips
2005 Conference on High Density Microsystem Design and Packaging and Component Failure Analysis, 2005Co-Authors: H. Lu, C Bailey, Y C ChanAbstract:A wide range of flip chip technologies with solder or adhesives have become dominant solutions for high density packaging applications due to the excellent electrical performance, high I/O density and good thermal performance. This paper discusses the use of modeling technique to predict the reliability of high density packaged flip chips in the humid environment. Reliability assessment is discussed for flip chip package at ultra-fine pitch with Anisotropic Conductive Film (ACF). The purpose of this modeling work is to understand the role that moisture plays in the failure of ACF flip chips. A macro-micro 3D finite element modeling technique was used in order to make the multi-length-scale modeling of the ACF flip chip possible. Modeling results are consistent with the findings in the experimental work
-
study of Anisotropic Conductive adhesive joint behavior under 3 point bending
Microelectronics Reliability, 2005Co-Authors: M J Rizvi, Y C Chan, C BaileyAbstract:Flip chip interconnections using Anisotropic Conductive Film (ACF) are now a very attractive technique for electronic packaging assembly. Although ACF is environmentally friendly, many factors may influence the reliability of the final ACF joint. External mechanical loading is one of these factors. Finite element analysis (FEA) was carried out to understand the effect of mechanical loading on the ACF joint. A 3-dimensional model of adhesively bonded flip chip assembly was built and simulations were performed for the 3-point bending test. The results show that the stress at its highest value at the corners, where the chip and ACF were connected together. The ACF thickness was increased at these corner regions. It was found that higher mechanical loading results in higher stress that causes a greater gap between the chip and the substrate at the corner position. Experimental work was also carried out to study the electrical reliability of the ACF joint with the applied bending load. As per the prediction from FEA, it was found that at first the corner joint failed. Successive open joints from the corner towards the middle were also noticed with the increase of the applied load.
-
the effect of reflow process on the contact resistance and reliability of Anisotropic Conductive Film interconnection for flip chip on flex applications
Microelectronics Reliability, 2003Co-Authors: Chunyan Yin, Y C Chan, C Bailey, M O Alam, Hua LuAbstract:The work presented in this paper focuses on the effect of reflow process on the contact resistance and reliability of Anisotropic Conductive Film (ACF) interconnection. The contact resistance of ACF interconnection increases after reflow process due to the decrease in contact area of the conducting particles between the mating I/O pads. However, the relationship between the contact resistance and bonding parameters of the ACF interconnection with reflow treatment follows the similar trend to that of the as-bonded (i.e. without reflow) ACF interconnection. The contact resistance increases as the peak temperature of reflow profile increases. Nearly 40% of the joints were found to be open after reflow with 260 °C peak temperature. During the reflow process, the entrapped (between the chip and substrate) adhesive matrix tries to expand much more than the tiny Conductive particles because of the higher coefficient of thermal expansion, the induced thermal stress will try to lift the bump from the pad and decrease the contact area of the Conductive path and eventually, leading to a complete loss of electrical contact. In addition, the environmental effect on contact resistance such as high temperature/humidity aging test was also investigated. Compared with the ACF interconnections with Ni/Au bump, higher thermal stress in the Z-direction is accumulated in the ACF interconnections with Au bump during the reflow process owing to the higher bump height, thus greater loss of contact area between the particles and I/O pads leads to an increase of contact resistance and poorer reliability after reflow.