Characterization Of Electrically Conductive Inks In Simulated Space Environment

Increasing numbers of satellite missions necessitate a standalone power supply with self-recovery capabilities in case of failure in the space environment. A self-repairing kit was developed with the capabilities to repair the damaged solar array by dispensing conductive inks. Dispensing of conductive materials using direct writing technology to the space environment not only repairs damaged electronic components but also demonstrates the possibilities of manufacturing in outer space. For earth application, properties of direct writing inks have been evolved. In space application, direct writing inks or conductive inks have some issues such as outgassing, vapor pressure, curing etc.Therefore, having the properties known of electrically conductive ink can be used for dispensing materials in future space application. This research deals with the curing behavior of electrically conductive inks in simulated space environment. For the experimental investigation, two types of electrically conductive ink E1660 (Ercon) and CB102 (DuPont) have been chosen which passed the requirements of NASA low outgassing ( according to ASTM E595 test, condensed volatile collected mass is less than 0.1%). Also, both of the inks were studied previously as direct writing inks on a 3D printed substrate. E1660 and CB102 consist of flake based silver particles and nano silver particles respectively. A microdispenser was developed to demonstrate the ink injection on a customized printed circuit board. A simple and low-cost continuity test method was used to demonstrate the conductive behavior of inks at different temperatures and pressures at the representative of simulated space environment. A thermal environment test that had the ability to create the temperature range from -150° to 350° was chosen to verify the experimental methods and procedure. Continuity test and voltage divider rule were employed together to determine the time required to develop a conductive path on the surface and subsurface of the ink trace after being dispensed on the substrate. Time was measured until the maximum conductivity obtained for each test. Subsequently, to simulate the space environment, a thermal vacuum chamber was chosen that had the capability to create low vacuum pressure (10-2 Torr) and thermal cycle (-80° to 100°). Thermal vacuum testing was used to examine the curing properties of conductive inks in a vacuum environment. For each thermal vacuum test, there was some bubble formation on the ink surface. Therefore, it was essential to study the microstructure of the cured ink after vacuum testing. SEM micrograph and LabVIEW machine vision tool were used to determine the void space that was created due to the evaporation of polymer binder or solution form the ink bulk. Though 10-2Torr vacuum level is not exactly representing the deep space environment, this Thesis provides the necessary information to develop a direct writing repair kit and characterization techniques of commercially available and previously studied inks