Nemco Electronics Performance Info - Manual

General Performance Information
Introduction
Tantalum capacitors are manufactured from a powder of pure tantalum metal. The powder is compressed under high
pressure around a tantalum wire to form a ‘pellet’. The riser wire is the anode connection to the capacitor. This is subsequently
vacuum sintered at high temperature (typically 1500 - 2000°C). This helps to drive off any impurities within the powder by
migration to the surface. During sintering the powder becomes a sponge like structure with all the particles interconnected in a
huge lattice. This structure is of high mechanical strength and density, but is also highly porous giving a large internal surface area.
The larger the surface area the larger the capacitance. By choosing the powder used to produce each capacitance/voltage
rating, the surface area can be controlled. The next stage is the production of the cathode plate. This is achieved by pyrolysis of
manganese nitrate into manganese dioxide. The ‘pellet’ is dipped into an aqueous solution of nitrate and then baked in an oven
at approximately 250°C to produce a dioxide coat. This process is repeated several times, varying specific densities of nitrate to
build up a thick coat over all internal and external surfaces of the ‘pellet’. The ‘pellet’ is then dipped into graphite and silver to
provide a good connection to the manganese dioxide cathode plate. Electrical contact is established by deposition of carbon onto
the surface of the cathode. The carbon is then coated with a conductive material to facilitate connection to the cathode
termination. Packaging is carried out to meet specifications and customer requirements.
Specifications
Data relates to an ambient temperature of +25° C
z Operating temperature range -55°C to +125°C
PCT, LSR, MCT and TB
- 2/3 x Vr (linear derating) required for operation above +85°C.
CGT (Consumer grade) - (linear derating) +40°C to 0.5 x Vr at +85°C and 0.2 x Vr at +125°C.
z Capacitance Nominal rated capacitance is measured at +25°C, 120 Hz source, free of harmonics with a maximum bias of
2.2V d.c. Capacitance decreases with increasing frequency and increases with increasing temperature.
Typical Component Typical Component
Capacitance vs. Temperature Capacitance vs. Frequency
Temperature °C Frequency
z Capacitance tolerances E.I.A. standard ±20% and ±10%.
Tolerance is the permissable variation of the actual value of capacitance from the rated value.
z Stability ΔC ≤ 12% over the operating temperature range
C
z Environmental Classification 55/125/56 (IEC 68-2)
Cap
acit
ance %
% Cap
acit
ance Change