Tak Fukushima - FlexTrate Characterization

Session 5: FHE Manufacturing Methods I

FlexTrateTM Characterization
Tuesday, June 20, 2017 
3:20 PM - 3:40 PM

We have adapted Fan-Out Wafer-Level Packaging (FOWLP) to integrate a heterogeneous set of small and thin dielets (Si or III-V etc.) on a biocompatible flexible substrate we call FlexTrateTM. This technology allows us to embed multiple dies(~625) and interconnect them at pitches below 10 µm . No wire bonding and solder bumping are required to integrate this flexible system consisting of the semi-rigid inorganic dielets and flexible polymeric substrates. The wafer-level processing is scalable, and high-performance inorganic semiconductor devices can be integrated onto flexible substrates without the use of organic semiconductor materials and printed wiring processes. In this work, we characterize the FlexTrateTM having high-density flexible interconnects from the point of view of process integration, electrical properties as well as mechanical reliability/biocompatibility. Typical FOWLP technologies using rigid epoxy substrates potentially have big concerns on die shift causing misaligned dielets and wafer bow resulting in lithographical errors/handling failures. However, we employ a stretchable PDMS that has low Young’s modulus and low-temperature curing properties. Thus, extremely low die shift and wafer bow are expected. In addition, the extreme flexibility (bending twisting and stretching) of FlexTrateTM with 100-µm-thick Si dielets and the endurance on saline immersion test are evaluated not only for wearable use but also implantable applications such as retina prosthesis and brain stimulation.


Speaker's Biography

Takafumi Fukushima received the B.S., M.S., Ph.D. degrees in Department of Materials Science and Chemical Engineering from Yokohama National University in 1998, 2000, 2003, respectively. From 2001 to 2003, he was a technical advisor at PI R&D Corporation in Yokohama. After that, he worked at Venture Business Laboratory of Tohoku University as a postdoctoral fellow for a year. From 2004 to 2009, he was an assistant professor at Department of Bioengineering and Robotics, Tohoku University. From 2010 to 2014, he was an associate professor at New Industry Creation Hatchery Center (NICHe), Tohoku University. From 2015-2016, he was an associate professor at Department of Bioengineering and Robotics, Tohoku University. He worked on many aspects of 3D and heterogeneous system integration including TSV (through-silicon via) technologies, capillary self-assembly, retinal prosthesis, and brain implantable probes in Tohoku University. From 2013, he also joined a consortium of 8/12-inch R&D fab, called Global INTegration Initiative (GINTI), for new 2.5D/3D integration technologies, Tohoku University. He is currently working on 3D/heterogeneous integration technologies at Department of Mechanical System Engineering, Tohoku University, as an associate professor, and new flexible device integration at Center for Heterogeneous Integration and Performance Scaling (CHIPS), Electrical Engineering Department, UCLA, as a visiting research associate. He was awarded “German Innovation Award / the Gottfried Wagener Prize 2009” and “ 2010 Outstanding Paper Award of the 60th Electronic Components and Technology Conference (ECTC)”, and so on.


Tak Fukushima
University of California Los Angeles