UCLA

Leading-edge implantable applications such as neural implanted prosthetics and next-generation Internet of Things (IoT) devices require the integration of high performance and low power logic, memory and sensors at high interconnect density which is not possible using conventional printed flexible electronics. As flexible applications mature, there will be a demand that they are “smart,” which will require leading edge CMOS and RF electronics, advanced sensors, and power management. There is a need to develop a robust and flexible electronics packaging platform that will enable the unrestricted integration of high-performance, state-of-the-art components (processors, memories, sensors, data transmitters and receivers, power sources etc.) on biocompatible, flexible substrates with the ability to miniaturize, interconnect at high density with acceptable reliability, and scale-up in manufacturing at economical and cost-effective price points. Considering all the above requirements, in this work, the development of a highly flexible and reliable heterogeneous integration platform with fine interconnect pitch (≤ 40 �m) called FlexTrateTM is investigated. The fabrication and assembly processes necessary for such a platform are developed. FlexTrateTM is based on a die-first flexible Fan-Out Wafer-Level Packaging (FOWLP) approach where Polydimethylsiloxane (PDMS) is used as a molding compound to embed the heterogeneous dies and integrate them with mechanically robust vertically corrugated interconnects at 20-40 �m pad pitches without the use of solder. FlexTrateTM is demonstrated to be bendable to 1 mm bending radius for thousands of bending cycles with minimal degradation in the system’s electrical performance. The benefits to system performance and flexibility of FlexTrateTM-style integration are highlighted through three demonstrations: 200 dies integrated at 40 �m pad pitches, a foldable display, and a wearable biosensing system in the form of wireless multi-channel surface electromyography (sEMG) system. The sEMG system can be attached to the skin to record quality muscle signals through dry electrodes and can transmit data to a computer or smartphone via Bluetooth Low Energy (BLE). The ability to acquire muscle signals through our device in a mobile setting is critical for the study of many muscular physiological phenomena and disorders.