Minimizing Temperature Gradient In Photonic Sintering For Defect-Free High-Conductivity Cu-Based Printed Patterns By Bidirectional Irradiation

Intense pulsed light (IPL)-induced photothermal heating is relatively effective at reducing the annealing or sintering time of metal particle-based conductive patterns in the manufacturing of printed electronics. However, defects such as cavities, delamination, and inhomogeneous shrinkage within the sintered patterns are a well-known problem in IPL sintering. These defects are considerably influenced by undesired temperature gradients induced inside samples during IPL sintering. To solve this undesired temperature gradient problem, we propose a bidirectional IPL (B-IPL) sintering approach using front- and back-elliptical reflectors on both sides of the printed pattern. The effects of the B-IPL energy density and number of shots on the electrical and mechanical properties of the printed patterns were systematically investigated using noncontact spectroscopic temperature sensing techniques with a mu s-timescale infrared temperature sensor system. Cross-sectional field emission scanning electron microscopy images indicate that B-IPL sintering significantly enhances the densification level and sintering uniformity of printed patterns compared to conventional IPL.