An Optical Aerosol Sensor for Process Monitoring of Aerosol-Jet Printing

Aerosol-Jet Printing (AJP) is a fabrication technology for 3D printed electronic applications ranging from conformal metallization to system-in-package hybrid devices. The desire to achieve improved control of the AJP process has spurred the development of strategies for in-line estimation of key AJP process variables. This paper describes the design and initial testing of a novel optical light scattering sensor for enabling in-line process monitoring and control of aerosolized ink properties for future process control strategies. The sensor measures optical scattering by the AJP aerosol at nine angular positions using silicon photodetectors and LED light sources, providing a path for a compact, cost-effective in-line monitoring solution. An experimental evaluation of the sensor response to varied AJP ink compositions and process parameters was performed. Finally, the optical response of the system was modeled, and a general framework for extracting quantitative measurements of the scattering and absorption coefficients of the AJP transport mist was provided.