A chip integration method for implantable devices based on structural embedding using cyclic olefin copolymer

Reliable chip integration remains a major challenge in implantable devices, where continuous fluid exposure, mechanical deformation, and severe space constraints must be addressed simultaneously. Existing chip packaging approaches often create structural dead space and require complex encapsulation, which can increase vulnerability to fluid ingress and long-term reliability degradation under implantation-relevant conditions. This study presents a chip integration strategy based on structural embedding using cyclic olefin copolymer (COC). Integrated circuit chips were embedded into a thermoplastic polymer substrate through an inverse truncated pyramid (ITP) geometry, enabling direct electrical integration without additional interconnection space. The integrated structure was subjected to a broad set of evaluations under implantation-relevant conditions, including in vitro biocompatibility assessment, electrical connectivity measurement, mechanical and thermal reliability testing, long-term insulation evaluation, and functional validation. The proposed approach achieved an electrical connectivity yield of up to 87% after PEDOT:PSS reinforcement. Finite element analysis showed that the ITP geometry redistributed mechanically induced stress away from the chip in terface and facilitated spatial dissipation of chip-generated heat. Long-term soak testing confirmed stable electrical insulation for 380 days, corresponding to aprojectedoperational lifetime of approximately 14.5 years under physiological conditions. Embedded functional devices also retained stable electrical performance after integration. These results demonstrate that the proposed structural embedding strategy enables monolithic, space efficient, and mechanically robust chip integration under implantation-relevant conditions. Taken together, the findings suggest that the proposed approach may offer a promising basis for further development toward compact and reliable implantable devices with integrated electronics.