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.
However, the current temperature range of aluminum electrolytic capacitors is limited to −50 °C to 150 °C, [, ] primarily restricted by the poor thermal stability of their cathode materials, such as electrolyte, MnO 2, or conductive polymers [, , , , , ].
Film capacitors mainly use polymers as the dielectric material, but their high temperature aging characteristics have always limited significant improvements in high temperature performance. When polyetherimide (PEI) [1, 14] or polyimide (PI) is used as the dielectric material, the maximum temperature range can reach 200–250 °C.
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.
However, electrolytic capacitors are restricted in working temperatures (<150 °C) and humidity conditions due to the inherent characteristics of MnO 2 or polymer cathodes that tend to deteriorate at high temperatures and moisture.
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.