Solid Electrolytic Capacitors Designed for High Temperature Applications

Abstract

For decades the maximum recommended operating temperature of solid electrolytic capacitors was 125°C. Responding to needs in the automotive and downhole drilling industries passive component manufacturers developed surface mount tantalum capacitors rated at 150°C in 2002–2003. Since that time the industry has introduced high temperature capable tantalum capacitors generally in 25°C increments roughly every four years. Today multiple manufacturers have products rated at 230°C poised for market release. The tantalum anode, tantalum pentoxide dielectric and manganese dioxide primary cathode material stand up well to these temperatures, although some optimization of the design and manufacturing process for these materials have been required. The primary challenges encountered when developing solid electrolytic capacitors with high temperature capabilities are associated with the carbon, silver and epoxy encapsulant materials used in conventional surface mount tantalum capacitors. Capacitor manufacturers have taken different paths to overcome these challenges. We have developed a metallized plating process to avoid issues associated with silver paints utilized in conventional Ta capacitors. We have worked with suppliers, or developed in house capabilities, to manufacture the other materials required to withstand the rigors of high temperature applications. This paper will discuss these challenges and provide reliability test data on a recently developed tantalum surface mount series capable of continuous operation at 230°C.