Laser Annealing Effects on DC Surface Flashover of PMMA and Polystyrene

Abstract

This research focuses on the effects of laser annealing on DC surface flashover characteristics of Polymethyl Methacrylate (PMMA) and Polystyrene (PS) dielectric samples. While many factors can contribute to flashover performance of a dielectric, such as insulator parameters, insulator operating environment and the interface between electrode and dielectric, micro scale structures on the surface of dielectrics have been identified as a major factor that affects the flashover performance. In an effort to increase flashover hold-off voltage, excimer laser annealing was used to melt and recrystallize the surface of the dielectric samples yielding smaller grain size and a more uniform surface. Samples were subdivided into three major categories governed by the ambient gas that the samples were annealed in: vacuum, SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> , and nitrogen. Results were compared with unannealed benchmarks. Other processing variables include number of pulses per unit area and laser fluence, ranging from 250 mJ/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> to 1000 mJ/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . All samples are cylindrical in shape with a diameter of 51 mm and a thickness of 6.24 mm. The results demonstrated a correlation between the annealed energy and the flashover voltage.