Tantalum Capacitor Technology Assessment Tantalum electrolytic capacitors have long been used in high temperature applications. Since the introduction of the first practical devices in the 1950’s, steady progress has been made increasing energy density and reliability. These are polar devices having distinct positive and negative terminals that cannot be reversed. The family of tantalum electrolytic capacitors can be subdivided into two major categories, solid tantalums and wet tantalums. As will be noted, these types are somewhat different in their operation. All modern tantalum capacitors share a common element, the pellet anode, made by pressing and sintering high surface area tantalum powder to form a pellet of tantalum with low density, high surface area, and a high level of internal porosity. An insulating layer of tantalum oxide, which serves as the capacitor dielectric, is formed on the surface of the pellet. The thickness of the dielectric determines the voltage rating of the capacitor. Wet tantalum capacitors are generally available with voltage ratings up to 125 volts. Tantalum chips are made with voltage ratings up to 50 volts. The size of the tantalum pellet and the thickness of the dielectric determine the overall capacitance of the device.
