High Dielectric Constant Polymer Film Capacitors (PREPRINT)

摘要

Pulse-forming networks (PFNs) are critical for many pulsed power applications; they perform conversion of prime electric energy into short pulses needed to energize large loads. They require high energy density, fast discharge speed (milliseconds to nanoseconds) capacitors. Medical defibrillators also require high performance capacitors that can deliver pulsed energy to the patient heart in approximately 5 milliseconds at 800 volts (implantable) or over 2,000 volts (external). Current commercial electrostatic capacitors usually have an energy density well below 3 J/cc due to the limitation of dielectric material performance and reliability constraints. The capacitors usually occupy a large fraction of the volume and contribute to the major cost in both the PFNs. The bulky size of capacitor components severely impedes the miniaturization of many electronic devices. The energy density (UE) of a linear dielectric material is proportional to its dielectric constant (K) and the square of its dielectric breakdown strength (DBS). Therefore, high K and DBS are critical to achieve a high energy density in capacitors. DBS is determined by both intrinsic and extrinsic (process-related) factors, but there is a general consensus that except for very thin films deposited on a substrate, the breakdown in practical components is limited by defects introduced during film processing. There have been many improvements over the last 10 to 20 years in polymer resin purity, capacitor film quality, metallization design, and capacitor fabrication so that energy densities of 1 to 3 J/cubic cm are now available with predictable lifetime for mission critical applications. It is uncertain if more process improvements can be expected to yield further energy density. In this paper, we present our recent progress in the development of high-K polymer dielectric materials, the commercial scale production of high- quality capacitor film, and the test of our first generation prototype capacitors.