Electrodeposition and Electroless Deposition for High Conductivity, High Resolution Aerosol Jet Printed Components

Abstract

Aerosol jet printing (AJP) additive manufacturing is a technique capable of depositing a variety of materials with linewidths on the order of 10-50 mm. [1] These materials include polymers, metal nanoparticle inks, and ceramics. [2] Nanoparticle Ag inks have been widely used for printing of conductive structures because of their low cost and ease of printing. However, the maximum conductivity of these inks reported in the literature does not exceed around 25% of bulk.[3] Reducing the resistance of a printed part by increasing the number of layers decreases the resolution due to ink spreading. Alternatively, nanoparticle-free reactive inks can reach 60-70% of bulk Ag conductivity but require thermal treatments at 300oC that are incompatible with some substrate materials. [4] Here, we combine AJP with electrochemical deposition processes enabling the fabrication of electronic components with the high resolution of AJP and the higher conductivity parts typical of the electrodeposition. This hybrid process offers access to new materials for which no ink formulations exist but where electrochemical deposition processes including both electroless deposition and electroplating are readily available. Recently we have demonstrated the resistance of printed inductors can be reduced by a factor of 35-45x by Cu electrodeposition from an acid Cu plating bath. [1]Herein, we report on a hybrid approach where aerosol jet printing of nanoparticle Ag ink (UTDots, Ag40X) is used to template a seed layer followed by the electroless and/or electrodeposition of a high conductivity metal. This technique is particularly attractive in the modification of long length printed inductor spirals. Here an Ohmic drop between the interior and exterior of the spirals creates a non-uniform current distribution across the length of the component. Electroless deposition prior to electrodeposition can reinforce the conductance of the part by decreasing this Ohmic loss. An electroless deposition process using a Circuposit Cu solution reduces a spiral inductor’s DC resistance from > 2 kΩ to 105 Ω (Figure 1). The optimization of the hybrid electroless and electrodeposition process parameters for maximizing conductivity, inductance, tolerance of temperature cycling, and uniformity of deposition will also be presented. Acknowledgments SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2021-4056 A