This study proposes an innovative methodology for developing flexible printed circuit boards (FPCBs) capable of conforming to three-dimensional shapes, meeting the increasing demand for electronic circuits in diverse and complex product designs. By integrating a traditional flat plate-based fabrication process with a subsequent three-dimensional thermal deformation technique, we have successfully demonstrated an FPCB that maintains stable electrical characteristics despite significant shape deformations. Using a modified polyimide substrate along with Ag flake-based conductive ink, we identified optimized process variables that enable substrate thermal deformation at lower temperatures (~130℃) and enhance the stretchability of the conductive ink (ε ~30%). The application of this novel FPCB in a prototype 3D-shaped sensor device, incorporating photosensors and temperature sensors, illustrates its potential for creating multifunctional, shape-adaptable electronic devices. The sensor can detect external light sources and measure ambient temperature, demonstrating stable operation even after transitioning from a planar to a three-dimensional configuration. This research lays the foundation for next-generation FPCBs that can be seamlessly integrated into various products, ushering in a new era of electronic device design and functionality.

In this paper, we analyzed the effects of doctoring process on the patterns of Ag in gravure off-set printing. The parameters of doctoring process were the angle and the pressure, which was represented by the depth of movement to the gravure roll, of doctor blade to the surface of gravure roll, and the angle of patterns engraved on the gravure roll to doctor blade moving direction. The proper parameters were extracted for the fine patterns and they were 15 mm for the pressure, 60° for the blade angle. And the angle of patterns with respect to blade movement should be less than 40° for the best results. The gravure off-set printing with the above parameters was carried out print gate electrodes and scan bus lines of OTFT-backplane for e-paper. The line width of 50㎛ was successfully obtained. The thickness of electrodes was 2.5㎛and the surface roughness was 0.65㎛ and sheet resistance was 15.8 Ω/□.