Intense pulsed light sintering of Cu nano particles/micro particles-ink assisted with heating and vacuum holding of substrate for warpage free printed electronic circuit.

Abstract In this work, intense pulsed light (IPL) sintering process was investigated with vacuum stretching and heating of the polymer substrate for warpage free printed electronics circuit. The IPL irradiation energy and substrate heating temperature were optimized to obtain high electrical conductivity, high adhesion strength, and little warpage of printed Cu electrodes pattern on the polyimide (PI) substrate. Scanning electron microscopy and x-ray diffraction were conducted to characterize microstructure and transformation crystal phase of the IPL sintered Cu nanoparticle (NP)/microparticle (MP)-ink film. The resistivity of IPL sintered Cu NP/MP-ink films was measured using the four-point probe method and profilometer. In order to monitor IPL sintering process, in-situ resistance and temperature monitoring of Cu NP/MP-ink were conducted. Also, a transient heat transfer analysis was performed using finite-element analysis software to predict temperature gradients of Cu NP/MP-ink and polymer substrate during IPL light sintering process. As a result, the optimal IPL light sintered Cu NP/MP-ink film (vacuum applied, 150 °C heating, and irradiation energy: 3.5 J/cm2) had a low resistivity 6.94 μΩ·cm and 5 B level of adhesion strength with almost no warpage of PI substrate. Highlights • Cu nano/micro particle (NP/MP)-ink was intense pulsed light (IPL) sintered. • We employed the substrate vacuum holding and heating during IPL sintering. • 3.5 J/cm2 with 150 °C heating was determined as optimum conditions. • The sintered Cu NP/MP-ink showed the lowest resistivity with 5B adhesion level. • The Cu NP/MP-ink was sintered with almost no warpage of polymer substrate. [ABSTRACT FROM AUTHOR]