Aerosol Jet Printing of Dielectric Polymer-Based Nanocomposites with Improved Thermal Conductivity for Electronic Applications

Aerosol Jet Printing (AJP) is an advanced additive manufacturing technology emerging for its ability to produce high-resolution, cost-effective, and energy-efficient electronic devices. It enables the deposition of a diverse range of materials, including metals, ceramics, and polymers, which is crucial for creating miniaturized, high-performance devices for industrial applications. In the electronics industry, AJP could offer significant advantages over traditional lithographic and screen-printing methods. Its maskless, computer-aided design (CAD) approach allows for rapid prototyping and customization without the need for costly and time-consuming mask production.<br/>As technology advances, electronic devices require higher frequencies, increased integration levels, and miniaturization, bringing increasingly demanding requirements and challenges. The need for low delay times, crucial for high frequencies, has driven attention to low dielectric constant materials. Additionally, densely packed components in miniaturized electronics generate more heat, making efficient heat dissipation fundamental. Thus, materials combining dielectric properties with high thermal conductivity and stability are urgently required to improve heat dissipation and device reliability. Moreover, precision in manufacturing processes is necessary for complex pattern production. Therefore, designing materials with low dielectric constant, improved thermal conductivity, and high thermal stability, and studying their processability with AJP, is a current challenge for fabricating efficient and reliable miniaturized electronics meeting the latest requirements.<br/><br/>In this study, multifunctional polymer-based nanocomposites with a benzocyclobutadiene (BCB) matrix and boron nitride nanosheets (BNNS) as filler, varying from 0 to 20 wt%, were designed and processed by AJP for potential electronics applications. A comprehensive investigation of these nanocomposites' processability with AJP was carried out, and the effects of BNNS in the polymer matrix were investigated in terms of rheological, dielectric, and thermal properties.<br/>The rheological properties of the inks were optimized to ensure viscosity requirements for pneumatic AJP, typically between 1 and 1000 mPa^.s for high-quality prints. The optimized ink formulations facilitated the generation and transport of stable inks. The printability of the inks was investigated by managing various printing parameters, such as atomizer gas flow rate, driving gas flow rate, sheath gas flow rate, and printing speed, unraveling their complex interplay. This analysis followed a design of experiment (DOE) approach, allowing the identification of optimized parameter combinations according to the filler content and, thus, printing patterns with complex geometries, featuring resolutions around 50 µm, demonstrating AJP's applicability in electronics.<br/>The addition of BNNS positively affected the polymer properties. The nanocomposites showed a low dielectric constant even with 20 wt% BNNS, ranging from 2.30 to 2.55, with low dielectric loss values. The heat dissipation ability increased, with a 232% enhancement in thermal conductivity compared to the plain matrix with 20 wt% BNNS incorporation. Furthermore, the nanocomposites were found to be highly thermally stable, with degradation temperatures above 440 °C.<br/><br/>In conclusion, the successful design and printing of nanocomposite dielectric and thermally stable inks with enhanced thermal conductivity demonstrate AJP's capability to process complex formulations with high quality. These findings support the broader adoption of AJP in the electronics industry, especially for multifunctional polymer-based materials with potential applications as passive components like microelectronic packaging, thermal interface materials, and adhesives in high-temperature electronics.