Abnormal Capacitance Increasing at Elevated Temperature in Tantalum Capacitors with PEDOT:PSS Electrodes

Qifeng Pan,Qiao Liu,Yuanjiang Yang,Dongbin Tian

doi:10.1155/2018/9864387

Abstract

Due to the importance of capacitance temperature stability in precise analog circuit applications, capacitance instability at elevated temperature of 125°C was investigated in tantalum capacitors with PEDOT:PSS counter electrodes. Capacitance-voltage measurement supposed that residual ions in the PEDOT:PSS dispersion caused an accumulation of charges at the dielectric-cathode interface which contributed to an increase in the dielectric constant and resulted in the capacitance increasing at high temperature. Based on the hypothesis, water wash process was applied and capacitance dropped significantly at high temperature. This study shows that an additional water wash process is necessary to improve the capacitance temperature stability after each dispersion dip step.

Highlights

Due to much lower equivalent series resistance (ESR) and more benign failure mode than the incumbent MnO2cathode technology, conductive polymer tantalum capacitors are expanding their market share in both the commercial world and military world
Because the processing of 3,4ethylenedioxythiophene (EDOT) is much simpler than other conducting polymers and it is not classified as toxic chemical like pyrrole, Poly(3,4-ethylenedioxythiophene) (PEDOT) becomes the material of first choice for solid electrolytic capacitors
The first generation of conductive polymer tantalum capacitors was limited to using temperatures of 105∘C because it was found that some percentage of the devices would suffer steadily increasing ESR at higher temperature [5]

Summary

Introduction

Due to much lower equivalent series resistance (ESR) and more benign failure mode than the incumbent MnO2cathode technology, conductive polymer tantalum capacitors are expanding their market share in both the commercial world and military world. The first tantalum and aluminum polymer capacitors were introduced into the markets in early 1990s [1, 2]. Tantalum polymer capacitors are not without faults. The thermal stability of PEDOT is a major argument to substitute the much more stable MnO2 in tantalum electrolytic capacitors. The first generation of conductive polymer tantalum capacitors was limited to using temperatures of 105∘C because it was found that some percentage of the devices would suffer steadily increasing ESR at higher temperature [5]

Methods

Results

Conclusion