Small Introduction about Tantalum Capacitors

Tantalum capacitors are widely used in electronics design these days, they are similar to normal electrolytic capacitors, but using tantalum within the construction of the capacitor it is able to offer extremely high levels of capacitance and very high capacity density for any given volume. As such tantalum capacitors are widely used in electronics equipment where there is a need for small size and a high level of capacitance. In view of its advantages, the tantalum capacitor is used in large volumes within the electronics manufacturing industry.

Most common types of tantalum capacitors:

Tantalum SMD capacitors

Tantalum SMD capacitors

Initially tantalum capacitors were used in SMD applications because electrolytic capacitors were not able to survive the high temperatures of the soldering process. They are widely used to provide higher levels of capacitance than those that can be achieved when using ceramic capacitors. The used technology is based on the solid tantalum capacitor technology which is robust and enables a very small capacitor size.

Different packages that are used conform to EIA specifications:

PACKAGE DESIGNATION SIZE
(MM) EIA DESIGNATION
Size A 3.2 x 1.6 x 1.6 EIA 3216-18
Size B 3.5 x 2.8 x 1.9 EIA 3528-21
Size C 6.0 x 3.2 x 2.2 EIA 6032-28
Size D 7.3 x 4.3 x 2.4 EIA 7343-31
Size D 7.3 x 4.3 x 4.1 EIA 7343-43

Tantalum foil electrolytic capacitor

Tantalum foil capacitors have been developed to provide a more reliable form of electrolytic capacitor without the shelf life limitations of aluminum electrolytic capacitors. It was able to be developed as a result of the availability of high purity wires and tantalum foils.

Tantalum capacitors have a higher capacitance density than their aluminium electrolytic counterparts and can operate at temperatures up to about 120 Celsius, therefore they are often used in equipments used in extreme conditions.

Special type of these capacitors are:
» The wet tantalum capacitor, also known as the one with porous anode and liquid electrolyte. It was the first form to be introduced and still offers the best space factor. These type of capacitors are housed in a silver or silver plated container. The porous anode is made by pressing high purity tantalum power into a cylindrical body and then sintering in a vacuum at about 2000C. A variety of electrolytes can be used within this form of tantalum capacitor. Those using sulphuric acid as the electrolyte have very good electrical characteristics and the maximum working voltages that are manufactured tend to be a maximum of about 70 volts.

PCBA Tantalum Capacitor» The solid tantalum capacitors, also known as the one with porous anode and solid electrolyte, is the most common used variety and can be found in many items of consumer and commercial electronic equipment. Solid capacitors were developed by Bell Telephone Laboratories by using a porous anode and then replacing the liquid electrolyte with a solid semiconductor.

These capacitors are superior to aluminum electrolytic capacitors exhibiting by being smaller and exhibiting excellent temperature and frequency characteristics. Nonetheless they are not able to handle high levels of current or voltage spikes.

In view of the nature great care should be taken not to stress all these type of capacitors. The polarity should never be reversed, nor should they be exposed to over-voltage conditions. If so then they may fail, or even sometimes exploding.

Tantalum capacitor advantages and disadvantages

Advantages:
» Volumetric efficiency: offering a much high level of volumetric efficiency than many other types and being superior to common electrolytic capacitors.
» Good frequency characteristics: they are more suitable for use in a number of applications where electrolytics could not be used.
» High reliability: Tantalum capacitors are able to provide an almost unlimited life being operated within their ranges. Therefore their use is not time limited as in the case of the electrolytic capacitor.
» Wide operating temperature range: often specified for operating over the range -55C to +125C. This makes them an ideal choice for use in equipment for use in harsh environmental conditions.
» Compatibility with modern production methods: Tantalum capacitors are able to withstand the temperatures of SMT production and are there fore ideal for use in many new electronics designs.

Disadvantages
» Low ripple current ratings: tantalum capacitors do not have high ripple current ratings and should not be used in areas that require any levels of current to be passed.
» Not tolerant to reverse or excess voltage: Tantalum capacitors don’t like excess voltage or reverse, even spikes can destroy them. If they are exposed to excess or reverse voltages then they easily can explode.
» Higher costs: more expensive than many other capacitors.