Flexible In-Mold Electronics: Advanced FHE Technologies and Applications

4:50 pm - 5:10 pm

A new technological platform is established for scalable and high-performance flexible In-Mold Electronics (IME) based on advanced die-first or RDL-first FOWLP (fan-out wafer-level packaging) methodology. The concept of chiplets is extended to dielets including tiny passive dies, ultrasmall micro-LEDs, and bare dies consisting of a functional group divided from large chips, etc. Rigid, small, and thin dielets are embedded in flexible resins such as PDMS, flexible epoxy, and hydrogel as substrates. Ultrathin dies are not employed for the flexible IME applications due to their reliability issues. We demonstrate heterogeneous integration of Si-LSI, passives, and III-V dielets with various thicknesses ranging from 50 to 200 Î¼m. Fine-pitch interconnections are successfully formed on a stress buffer layer (SBL) as a key element that is inserted between the substrate and high-density wirings to mitigate mechanical stress and enhance bending reliability. Our flexible IME systems exhibit high bendability with a bending cycle of beyond 1,000 (bending radius: < 5 mm) by controlling neutral planes. Various demonstrators are fabricated for the advanced FHEs called flexible IME: (a) Flexible trans-nail photoplethysmographic (PPG) sensors with mini-LED drivers and photodiodes for biomedical/healthcare applications for monitoring pulse wave and percutaneous oxygen saturation (SpO2) as an indicator for COVID-19 (b) Flexible retina prosthesis system with embedded three-dimensionally stacked IC (3D-IC) having through-silicon via (TSV), so-called flexible 3D-IC (c) Flexible implantable neural probes embedding micro-LEDs for optogenetics (d) Flexible 3D IME such as smart contact lens, etc. (e) Hydrogel-based flexible patch for UV sterilization for COVID-19, etc. Interconnect formation and heterogeneous dielets integration on hydrogels are very challenging because the hydrogels are mainly composed of water or hydrophilic solvents. These highly integrated flexible IMEs would be expected for future wearable and implantable flexible devices toward the upcoming Internet Of Everything (IoE) society with real AI.

Speaker

Takafumi Fukushima

Professor Tohoku University

Takafumi Fukushima received the PhD degrees in the Department of Materials Science and Chemical Engineering from Yokohama National University in 2003. His research activity from 2004 includes 3D and heterogeneous system integration using TSV (through-silicon via) and capillary self-assembly in Tohoku University as an assistant professor and associate professor. From 2016 to 2017, He was a visiting research associate at the Center for Heterogeneous Integration and Performance Scaling (CHIPS), Electrical Engineering Department, UCLA. He is currently working on 3D/hybrid/flexible integration technologies for wearable/healthcare devices at the Department of Mechanical Systems Engineering, Tohoku University, as an associate professor. He is a senior member of IEEE.