High Voltage Tantalum Polymer Capacitors
Solid tantalum (Ta) capacitors with intrinsically conductive polymers as the cathode material have been widely used in the electronics industry due to their low equivalent series resistance (ESR) and “non-burning/non-ignition” failure mode. Intrinsically conductive polymers, commonly known as conductive polymers, are electrically conductive at the molecular level. Unlike polymeric materials whose electrical conductivity is imported from the presence of foreign conductive particles (for example silver paints or adhesives), a single molecule (a polymer chain) of an intrinsically conductive polymer is conductive. Various types of conductive polymers including polypyrrole, polyaniline, and polyethyldioxythiophene (PEDT) can be applied to dielectric oxides to serve as the primary cathode material for solid electrolytic capacitors. Two methods of coating the dielectric oxide with conductive polymers are widely used in the industry, in-situ polymerization and electrochemical polymerization. In in-situ polymerization the monomer of an intrinsically conductive polymer is brought into contact with an oxidizer to drive the polymerization reaction. In electrochemical polymerization the reaction is driven by an externally supplied current. The major drawback of conductive polymer capacitors, regardless of the type or method of application, is their relatively low working voltages compared to their MnO2 counterparts. For example, the maximum voltage rating of existing surface mount polymer tantalum capacitors is 25 volts, while that of their MnO2 counterparts is 50 volts. When subjected to voltages exceeding 25 volts, the existing polymer capacitors have, to varying degrees, reliability issues. This limitation has restricted the use of these devices to relatively low voltage applications (<20 volts). New developments in material and process technologies have overcome these limitations leading to the introduction of a new line of high voltage tantalum polymer capacitors with excellent long term reliability.
Performance and Reliability Study of 50V and 63V Tantalum Polymer Capacitors
Since their introduction, tantalum polymer capacitors have been sought after as a welcome complement to traditional tantalum MnO2 capacitors. Their advantages of improved ESR, benign failure modes, improved voltage derating and higher ripple handling have become well known by designers throughout the industry who need to consider such characteristics in their design. While the release of tantalum polymer capacitors has addressed most of the needs designers were seeking, one item had remained unresolved until recently, higher voltage ratings for power input rails.
Reference Data for Engineers: Radio, Electronics, Computers and Communications
Reference Data for Engineers is the most respected, reliable, and indispensable reference tool for technical professionals around the globe. Written by professionals for professionals, this book is a complete reference for engineers, covering a broad range of topics. It is the combined effort of 96 engineers, scientists, educators, and other recognized specialists in the fields of electronics, radio, computer, and communications technology.By providing an abundance of information on essential, need-to-know topics without heavy emphasis on complicated mathematics, Reference Data for Engineers is an absolute "must-have" for every engineer who requires comprehensive electrical, electronics, and communications data at his or her fingertips. Featured in the Ninth Edition is updated coverage on intellectual property and patents, probability and design, antennas, power electronics, rectifiers, power supplies, and properties of materials. Useful information on units, constants and conversion factors, active filter design, antennas, integrated circuits, surface acoustic wave design, and digital signal processing is also included. The Ninth Edition also offers new knowledge in the fields of satellite technology, space communication, microwave science, telecommunication, global positioning systems, frequency data, and radar.