UV Flash Sintering of Aerosol Jet Printed Silver Conductors for Microwave Circuit Applications

Recently, there has been significant research focus on the design of high functional density electronic systems, especially for 5G applications. In parallel, to address accurate, high-quality, fine-resolution circuit geometry requirements, increased research into additive manufacturing (AM) printing techniques, such as aerosol jet printing (AJP), has emerged. The issues are complicated by low-loss flexible substrates, such as liquid crystal polymers (LCPs), which are commonly used in the design of high-frequency circuits and systems. These substrates cannot be taken through high sintering temperature processes that are commonly required for silver inks. To avoid permanent damage, it is essential that the sintering temperature remains below the glass transition temperature (T
_g
) of the substrates. Recent work on LCP substrates has demonstrated 10%-20% bulk silver (Ag) conductivity by using low-temperature thermal sintering techniques. This article investigates the use of a rapid ultraviolet (UV) flash annealing technique to achieve high conductivity of Ag on LCP for use in high-frequency circuits while maintaining the integrity of the substrate. Results are compared against thermally sintered films. The resulting conductivity was studied as a function of UV exposure time and energy, printed film thickness, surface roughness of the substrate, and multilayer deposition.