• Capacitors, also known as condensers, are electrical devices that, something like batteries, can be charged to store electricity and release it (discharge) when it is needed. The most important difference is that the charging and discharging of a capacitor is much faster than with a battery. A simple capacitor is made from two metal plates (or plates made of another electrically conductive material), separated by a non-conducting--or insulating--material called the dielectric, in this instance, the precious metal tantalum.
  
  

Tantalum Capacitors

• How much electricity a capacitor can store (its capacitance) can be increased by making the conductive plates larger, building them closer together or by using a different dielectric. Tantalum is used because the metal forms an oxide layer on its surface which acts acting as the dielectric. Tiny tantalum capacitors are used in computers to even out power spikes that can damage the infinitesimal circuits on a chip.
  
  

Size, Life and Reliability

• Tantalum capacitors are particularly desirable because they can store a great deal of electricity for their size and weight, so the capacitors can be smaller--an advantage that mobile phone makers have taken advantage of to produce smaller and smaller cell phones. They are used especially where saving space is a priority and when long life and reliability are at a premium.
  
  

Polymers Vs. MnO2

• "Polymer" is a chemical term for large molecules that are made by creating chains of a small molecule. Proteins and starches are examples of natural polymers and plastics are man-made polymer materials. In the past, tantalum capacitors had two main weaknesses. Both of them were a byproduct of using magnesium dioxide (MnO2) as the cathode--the second plate, so to speak.
  
  Because the MnO2 contains a lot of oxygen and magnesium is a flammable metal, under some circumstances, when the capacitor failed they had a tendency to ignite. Replacing the MnO2 with an electrically conductive polymer solves that problem.
  
  The other drawback was that the tantalum-MnO2 capacitors had a higher "electrical resistance" than capacitors made with other dielectrics. By using a polymer for the cathode instead, engineers have been able to reduce the resistance inherent in the devices, as well, making them a better alternative. In fact, the conductive polymer developed as an alternative in the 1990s is 1,000 times more conductive than MnO2.