Advances in Ceramic Capacitors for High Temperature Applications

Abstract

There is a growing need for capacitors for applications at temperatures of 150°C or above, such as electronics for down-hole drilling and exploration, geothermal energy generation and power electronics. Conventional X7R and X8R type ceramic capacitors are designed for applications up to 125°C and 150°C, respectively. At temperatures above 150°C, these types of capacitors typically suffer from degradation of reliability performance and severe reduction in capacitance, especially under DC bias conditions. Recently, a Class-I C0G dielectric has been developed using Nickel electrodes for high temperature application up to 200°C and beyond. Due to its linear dielectric nature, this material exhibits highly stable capacitance as a function of temperature and voltage. Multi-layer ceramic capacitors (MLCC) made from this material can be qualified as X9G with robust reliability. A Class-II modified-X7R dielectric composition with nickel internal electrodes showing robust reliability at 175°C has also recently been developed. This paper will report electrical properties and reliability test data on these Class-I C0G and Class-II ceramic capacitors at high temperatures of 150–200°C and above.