PDMS-based flexible packaging method via a 12-inch RDL-first process for conformal electronic applications

Abstract

Purpose This study aims to realize large-scale and high-density manufacturing of conformal electronic devices by proposing a polydimethylsiloxane (PDMS)-based flexible packaging method via a 12-inch wafer-level redistribution-layer-first (RDL-first) process. Design/methodology/approach PDMS is used as the substrate to fabricate a conformal prototype, owing to its excellent processability, high flexibility and low cost. Electrical simulations show the series resistance and inductance of the daisy-chain structure. Mechanical simulations predict the stress distribution of the packaged structure under a 73.9 mm curvature radius, verifying its mechanical safety when embedded in a cranial mold. Experiments elaborate the process flow, mainly including temporary carrier preparation, RDL layer fabrication, chip flip-bonding and PDMS molding, successfully demonstrating a primary intelligent cranial prototype for signal processing and transceiving. Findings Mechanical simulations reveal that the maximum stress in the prototype when conformal to the cranial mold is 894.16?MPa with a PDMS thickness of 0.16 cm. The simulations also find that increasing PDMS thickness and reducing silicon thickness effectively lowers the maximum von Mises stress. A radio frequency (RF) signal processing prototype is precisely fabricated, containing four dies packaged in a dimension of 30 × 31.5 × 1.6 mm. It shows good flexibility with a minimum bending radius of 43.50 mm. The electrical test results demonstrate high consistency with the simulation results. Originality/value This work provides a processable, low-cost and high-efficiency packaging strategy for conformal electronics. PDMS encapsulation and 12-inch RDL-first wafer-level packaging process are combined. It may provide new strategies to wafer-level packaging technology in flexible applications.