• ETRI Journal
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• v.38 no.6
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• pp.1163-1171
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• 2016

Integration technologies involving flexible substrates are receiving significant attention owing the appearance of new products regarding wearable and Internet of Things technologies. There has been a continuous demand from the industry for a reliable bonding method applicable to a low-temperature process and flexible substrates. Up to now, however, an anisotropic conductive film (ACF) has been predominantly used in applications involving flexible substrates; we therefore suggest low-temperature lead-free soldering and bonding processes as a possible alternative for flex-on-flex applications. Test vehicles were designed on polyimide flexible substrates (FPCBs) to measure the contact resistances. Solder bumping was carried out using a solder-on-pad process with Solder Bump Maker based on Sn58Bi for low-temperature applications. In addition, thermocompression bonding of FPCBs was successfully demonstrated within the temperature of $150^{\circ}C$ using a newly developed fluxing underfill material with fluxing and curing capabilities at low temperature. The same FPCBs were bonded using commercially available ACFs in order to compare the joint properties with those of a joint formed using solder and an underfill. Both of the interconnections formed with Sn58Bi and ACF were examined through a contact resistance measurement, an $85^{\circ}C$ and 85% reliability test, and an SEM cross-sectional analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.164-165
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• 2008

현재의 소자간 연결을 위해 사용되는 금속배선 PCB의 한계로 인해 보다 고속/대용량의 광PCB가 크게 각광받고 있다. 본 논문에서는 광PCB와 소자간의 전기적 연결을 위해 사용되는 솔더 범프를 전도성 에폭시를 사용하여 마이크로 머시닝 공정을 통해 구현하고 제작된 솔더 범프의 I-V 특성을 살펴보았다. 제작된 100 um $\times$ 100 um $\times$ 25 um 와 300 um $\times$ 300 um $\times$ 25 um 의 샘플에서 각각 30 m$\Omega$과 90m$\Omega$의 전기저항을 얻을 수 있었다. 이를 통해 향후 센서및 엑츄에이터 시스템과 광 MEMS 등의 여러 분야에서 전도성 에폭시 솔더 범프를 이용하여 우수한 성능의 플립칩 본딩을 구현할 수 있을 것이다.