Reliability of Anisotropic Conductive Film Joints Using Bumpless Chip—Influence of Reflow Soldering and Environmental Testing

2005 ◽  
Vol 127 (2) ◽  
pp. 113-119 ◽  
Author(s):  
W. K. Chiang ◽  
Y. C. Chan
Keyword(s):  
Contact Resistance ◽  
Corrosion Mechanism ◽  
Anisotropic Conductive Film ◽  
Reflow Soldering ◽  
Environmental Testing ◽  
Polymer Hydrolysis ◽  
Conductive Film ◽  
Reflow Temperature ◽  
Environmental Test ◽  
Modulus Reduction

This paper presents the reliability of anisotropic conductive film (ACF) joint tested under reflow soldering and environmental test effect. The ACF joint behaved differently under different reflow soldering profiles. The lower reflow temperature resulted in more reliable ACF joints by maintaining low contact resistance. By contrast, high contact resistance was found in assemblies treated with higher reflow. Under humidity aging (85°C/85%RH), bumpless chips proved to be unreliable due to corrosion mechanism. Moreover, ACF had shown degradation in chemical and physical properties, including modulus reduction, Tg depression, polymer hydrolysis, and surface swelling after exposing to humidity aging. The deterioration in reliability of aged ACF joint during reflow process was mainly caused by hydroscopic swelling-induced stress of ACF.

Anisotropic conductive film for fine-pitch interconnects

2016 ◽  
Vol 2016 (1) ◽  
pp. 000044-000049 ◽  
Author(s):  
Daniel Nilsen Wright ◽  
Branson D. Belle ◽  
Kari Schjølberg-Henriksen ◽  
Hoang-Vu Nguyen ◽  
Jakob Gakkestad ◽  
...  
Keyword(s):  
Flip Chip ◽  
Failure Mechanisms ◽  
Anisotropic Conductive Film ◽  
Environmental Testing ◽  
Fine Pitch ◽  
Conductive Film ◽  
The Stability ◽  
Mechanical Bonds ◽  
Electrical Connections

Abstract An anisotropic conductive film (ACF) can be utilized to simultaneously form mechanical bonds and electrical connections during flip-chip assembly. The electrical connection is created by trapping randomly dispersed metallized polymer spheres (MPS) in the ACF that are deformed during the bonding process. This work postulates that the reliability of interconnects formed with ACF depends on the degree to which the MPS are deformed. Silicon samples with fine-pitch electrical test structures were flip-chip assembled using an ACF and measured in-situ during environmental testing. Interconnects with MPS deformation below 60% proved more stable than interconnects with higher deformation during exposure to 85% relative humidity at 20 °C, 45 °C, 60 °C and 85 °C, as postulated. On the other hand, the stability of the interconnects did not show a dependence on MPS deformation during exposure to thermal shock cycling (TSC) (−55 °C / +125 °C, 7 s transit time, 700 cycles). The results suggest that deformation of MPS is a central factor with respect to reliability of ACF-bonded fine-pitch samples exposed to humid conditions, but the results also indicate that other failure mechanisms are more important for samples exposed to thermally unstable conditions.

Behavior of Anisotropic Conductive Film (ACF) Joint under Mechanical Shock

2005 ◽  
Vol 127 (4) ◽  
pp. 375-380 ◽  
Author(s):  
Rashed Adnan Islam ◽  
Y. C. Chan
Keyword(s):  
Contact Resistance ◽  
Flexible Substrates ◽  
Mechanical Shock ◽  
Conductive Layer ◽  
Anisotropic Conductive Film ◽  
Particle Deformation ◽  
Humid Environment ◽  
Conductive Film ◽  
Microscope Images ◽  
Scanning Electron

The contact resistances investigated by this study of ACF joints using Au∕Ni bumps and flexible substrates are found to be increased by the induced mechanical shock and also by the combined effect of heat/humidity and the mechanical shock. The samples humidified at 85°C/85% RH for 384 h, on which a load of 3.164 Kg was dropped four times from a height of 0.4 m, exhibit the most severe results. The contact resistance increases by 700%, which had been about 62 mΩ in the as-bonded condition. The samples without humidification showed a sluggish and gentle increase in contact resistance with the induced mechanical shock. The contact resistance was found to be increased by 400% after the sixth drop from a height of 0.5 m. Scanning electron microscope images show particle deformation due to abrasion and friction between the contacting surfaces resulting from the sudden impact. Joints are also observed with no connections, which signify open circuits. Almost 25% of the circuits were found open in the samples (after 384 h in a humid environment), which have suffered severe mechanical shock (load drops four times from 0.4 m height). Breaking of the conductive layer of the particle and exposing the underlying polymeric portion were also observed.

Moisture Effects on the Reliability of Anisotropic Conductive Film Interconnection for Flip Chip on Flex Applications

2005 ◽  
Author(s):  
Chunyan Yin ◽  
Hua Lu ◽  
Chris Bailey ◽  
Yan-Cheong Chan
Keyword(s):  
Contact Resistance ◽  
Flip Chip ◽  
Semiconductor Industry ◽  
Moisture Diffusion ◽  
Testing Time ◽  
Anisotropic Conductive Film ◽  
Conductive Films ◽  
Conductive Film ◽  
Moisture Effects ◽  
Conductive Particles

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 the Thermocompression Bonding on the Microstructure and Contact Resistance for the Ultrafine Pitch Chip-on-Glass Packaging With Nonconductive Film

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Jianhua Zhang ◽  
Jinsong Zhang ◽  
Lianqiao Yang
Keyword(s):  
Contact Resistance ◽  
Bonding Temperature ◽  
Anisotropic Conductive Film ◽  
Bonding Parameters ◽  
Conductive Film ◽  
Geometric Size ◽  
Ε Phase ◽  
Thermocompression Bonding ◽  
Temperature And Pressure ◽  
Glass Packaging

Nonconductive film (NCF) is a challenging potential material to substitute the application of anisotropic conductive film in the ultrafine pitch chip-on-glass (COG) packaging. The NCF interconnection requires a high bonding temperature and pressure to form joints, and this causes new reliability concerns. This study investigated effects of the thermocompression bonding parameters on the microstructure and geometric size in the joints to a COG module packaged with NCF. The results revealed that the high temperature and pressure compressed the joints to become wider and shorter. A dual layer of intermetallic compounds consisting of AuSn2 (ε phase) and AuSn4 (η phase) was found in each joint. They were the two kinds of interphases with different melting points (AuSn2:309°C and AuSn4:257°C) during the interfacial reaction between Au and Sn. At the low temperature (below the melting point), the high pressure induced the residual inner stress to generate the cracks in the joints, and this also increased the contact resistance of the joints. The contact resistance increased with the pressure elevating at the same temperature and with the temperature degrading at the same pressure. In the COG packaging with NCF, a proper elevating of the bonding temperature could produce a stable direct connection with the low contact resistance.

Electron beam curing of acrylated epoxy resins for anisotropic conductive film application

2013 ◽  
Vol 547 ◽  
pp. 246-249 ◽  
Author(s):  
Tae gyu Shin ◽  
Inhyuk Lee ◽  
Jungmin Lee ◽  
Jinyoung Hwang ◽  
Hoeil Chung ◽  
...  
Keyword(s):  
Electron Beam ◽  
Epoxy Resins ◽  
Anisotropic Conductive Film ◽  
Conductive Film ◽  
Electron Beam Curing
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