What makes Tantalum a perfect dielectric for capacitors? It’s the oxide it produces. Almost all kinds of metals produce some kind of oxide when reacting with air. For example iron produces rust and copper produces a black oxide. Those types of oxides are referred to as crystalline oxides, meaning they are non-protective. Tantalum belongs to a group of metals called valve metals which include titanium, zirconium, niobium, hafnium, and aluminum. What makes Valve metals special is that they are able form a tightly adhering, stable, and electrically insulating oxides. However not all valve metals are able to have the thickness of their oxide accurately controlled through an electrochemical process.

Tantalum pentoxide possesses an extremely high dielectric constant of 26. When comparing a tantalum pentoxide to aluminum oxide you will notice a huge difference in dielectric constants. Both dielectrics are made from precious valve metals and possess the highest dielectric constants in the table. However tantalum pentoxide has a dielectric constant that is almost three times greater than aluminum oxide.

The military specification MIL-PRF-39006 establishes the failure rate testing per 1000 hours.

• 2%
• 1%
• 0.1%
• 0.01%
• 0.001%

The points on the graph marked with an “X” are fixed from ongoing reliability test data at +125 °C and above at the appropriate voltage derating.

Note: Any application above +85°C should be at a derated voltage suitable for the temperature.