page_title: Polymer capacitor
section_title: History
hierarchical_section_title: Polymer capacitor / History
caption_attribution_description: English: conductivities of some electrolytes for electrolytic capacitors
context_page_description: A polymer capacitor, or more accurately a polymer electrolytic capacitor, is an electrolytic capacitor with a solid electrolyte of a conductive polymer. There are four different types:
  Polymer tantalum electrolytic capacitor
  Polymer aluminum electrolytic capacitor
  Hybrid polymer capacitor
  Polymer niobium electrolytic capacitors
  Polymer Ta-e-caps are available in rectangular surface-mounted device chip style. Polymer Al-e-caps and hybrid polymer Al-e-caps are available in rectangular surface-mounted device chip style, in cylindrical SMDs style or as radial leaded versions.
  Polymer electrolytic capacitors are characterized by particularly low internal equivalent series resistances and high ripple current ratings. Their electrical parameters have similar temperature dependence, reliability and service life compared to solid tantalum capacitors, but have a much better temperature dependence and a considerably longer service life than aluminum electrolytic capacitors with non-solid electrolytes. In general polymer e-caps have a higher leakage current rating than the other solid or non-solid electrolytic capacitors.
context_section_description: Aluminum electrolytic capacitors (Al-e-caps) with liquid electrolytes were invented in 1896 by Charles Pollak.
  Tantalum electrolytic capacitors with solid manganese dioxide (MnO₂) electrolytes were invented by Bell Laboratories in the early 1950s, as a miniaturized and more reliable low-voltage support capacitor to complement the newly invented transistor, see Tantalum capacitor. The first Ta-e-caps with MnO₂ electrolytes had 10 times better conductivity and a higher ripple current load than earlier types Al-e-caps with liquid electrolyte. Additionally, unlike standard Al-e-caps, the equivalent series resistance (ESR) of Ta-caps is stable in varying temperatures.
  During the 1970s, the increasing digitization of electronic circuits came with decreasing operating voltages, and increasing switching frequencies and ripple current loads. This had consequences for power supplies and their electrolytic capacitors. Capacitors with lower ESR and lower equivalent series inductance (ESL) for bypass and decoupling capacitors used in power supply lines were needed. see Role of ESR, ESL and capacitance.
  A breakthrough came in 1973, with the discovery by A. Heeger and F. Wudl  of an organic conductor, the charge-transfer salt TCNQ. TCNQ (7,7,8,8-tetracyanoquinodimethane or N-n-butyl isoquinolinium in combination with TTF (Tetrathiafulvalene)) is a chain molecule of almost perfect one-dimensional structure that has a 10-fold better conductivity along the chains than does MnO₂, and has a 100-fold better conductivity than non-solid electrolytes.
  The first Al-e-caps to use the charge transfer salt TTF-TCNQ as a solid organic electrolyte was the OS-CON series offered in 1983 from Sanyo. These were wound, cylindrical capacitors with 10x increased electrolyte conductivity compared with MnO₂
  These capacitors were used in devices for applications that required the lowest possible ESR or highest possible ripple current. One OS-CON e-cap could replace three more bulky "wet" e-caps or two Ta-caps. By 1995, the Sanyo OS-CON became the preferred decoupling capacitor for Pentium processor-based IBM personal computers.
  The Sanyo OS-CON e-cap product line was sold in 2010 to Panasonic. Panasonic then replaced the TCNQ salt with a conducting polymer under the same brand.
  The next step in ESR reduction was the development of conducting polymers by Alan J. Heeger, Alan MacDiarmid and Hideki Shirakawa in 1975. The conductivity of conductive polymers such as polypyrrole (PPy)  or PEDOT is better than that of TCNQ by a factor of 100 to 500, and close to the conductivity of metals.
  In 1988 the first polymer electrolyte e-cap, "APYCAP" with PPy polymer electrolyte, was launched by the Japanese manufacturer Nitsuko.  The product was not successful, in part because it was not available in SMD versions.
  In 1991 Panasonic launched its polymer Al-e-cap series "SP-Cap", These e-caps used PPy polymer electrolyte and reached ESR values that were directly comparable to ceramic multilayer capacitors (MLCCs). They were still less expensive than tantalum capacitors and with their flat design useful in compact devices such as laptops and cell phones they competed with tantalum chip capacitors as well.
  Tantalum electrolytic capacitors with PPy polymer electrolyte cathode followed three years later. In 1993 NEC introduced its SMD polymer Ta-e-caps called "NeoCap". In 1997 Sanyo followed with the "POSCAP" polymer tantalum chips.
  A new conductive polymer for tantalum polymer capacitors was presented by Kemet at the "1999 Carts" conference. This capacitor used the newly developed organic conductive polymer PEDT (Poly(3,4-ethylenedioxythiophene)), also known as PEDOT (trade name Baytron®).
  Two years later at the 2001 APEC Conference, Kemet introduced PEDOT polymer aluminum e-caps to the market.  PEDOT polymer has a higher temperature stability, and as PEDOT:PSS solution this electrolyte could be inserted only by dipping instead of in-situ polymerization like for PPy which makes the production faster and cheaper. Its AO-Cap series included SMD capacitors with stacked anode in "D"
caption: Conductivities of some electrolytes
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