Atomic Oxygen Durability of Uncoated and Coated High-Frequency Circuit Materials

Abstract

Different materials were considered for high-frequency circuit applications requiring exposure to low Earth orbit (LEO) space environment. The potential candidates were TMM3 which is a ceramic thermoset polymer composite, and RO4003 which is a glass reinforced hydrocarbon/ceramic laminate, both manufactured by Rogers Corporation (USA). Various constituents of the space environment can affect these materials’ properties. Atomic oxygen is considered the most hazardous component since it may cause degradation of these materials by etching and/or changing the chemical composition. The candidate materials were tested by exposure to different equivalent atomic oxygen (ATOX) fluences of up to 1.9 × 10²¹ atoms cm⁻². The effects of the atomic oxygen exposures were studied by means of scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), atomic force microscopy (AFM) and mass loss measurements. Both materials were degraded under ATOX exposure, resulting in intensive mass loss as well as changes in surface morphology and chemistry. In order to protect these materials in the LEO environment several protective coatings were evaluated for TMM3. The protective coatings tested were SiO₂, CV1144-0 (a clear silicone coating) and SG120FD (a white silicone paint). SG120FD was found to provide the best protection against ATOX irradiation attack, while CV1144-0 provided a sufficient, though somewhat inferior protection.