Power Electronics

Tantalums Deliver Higher Capacitance, Ruggedness and Lead-free Design

Although they continue to face competition from improving ceramic capacitors, surface-mount tantalum capacitors continue to develop with newer devices offering higher values of capacitance in smaller packages. And with the July 2006 deadline looming for RoHS compliance, tantalum manufacturers also are introducing new components with lead-free designs. Other recent tantalum developments include the introduction of surge-robust tantalums for military applications and the spread of common nomenclature to simplify ordering.

Tantalum capacitors have some advantages over ceramic capacitors and other types that drive their continued development and use. According to John Prymak of Kemet, tantalums offer the highest volumetric capacitance of any electrostatic capacitors. Moreover, surface-mount tantalums are available in values that are still out of reach for ceramics. Prymak observes that while some 200 µF or 220 µF ceramic capacitors are just starting to sample, in practice, it’s difficult to find ceramics above 100 µF.

In contrast, recently introduced surface-mount tantalums feature values up to 1000 µF and higher values (at least 1500 µF) already are available in existing tantalum product families. In addition, tantalum capacitors do not suffer the degradation in performance that ceramics do over applied voltage and frequency.

Many of the tantalum benefits are illustrated by recent product introductions. For example, the TCJ Series of tantalum polymer capacitors from AVX are said to deliver the “industry’s highest capacitance values” in the designated case sizes. The TCJ Series features a 10-µF, 6.3-V capacitor in an 0805 case; a 47-µF, 6.3-V capacitor in a 1206; and a 100-µF, 4-V part in a 1206 (see the table).

The capacitors offer an operating voltage up to 12 V, operation at temperatures up to 125°C and guaranteed ESR. They also can withstand three times reflow profile up to 260°C and comply with RoHS requirements. Typical pricing ranges from $0.200 to $0.320 in quantities of 10,000, with lead times from 8 to 10 weeks and samples available immediately.

AVX also has unveiled a series of RoHS-compliant tantalums with very short package height for space-constrained applications. The low-profile TAJ “R” case size tantalum capacitor offers height options of 1.2 mm (0.047 in.), 1.5 mm (0.059 in.) and 2 mm (0.079 in.), which equate to that of standard IC packages after mounting. Applications include computer power supplies, disk drives, cellular phones and PCMCIA cards.

The high volumetric efficiency of the TAJ R tantalum capacitor material allows the chip to achieve high capacitance values in standard case sizes. Capacitance values range from 0.1µF to 22µF with a capacitance tolerance of ±10% to ±20%. This product series also includes higher values of capacitance in other case sizes (see the table). In addition, this tantalum capacitor family has an operating temperature range of -55°C to +125°C. Pricing for the TAJ devices is in the range of $0.21 each in volume.

In October, KEMET introduced its High-Grade COTS T497 Series of surge-robust tantalum capacitors. These devices achieve their ruggedness through conservative design. As the company notes in its Product Release documentation, “These parts are built with long proven capabilities using tantalum as the anode or base material. Ta2O5 as the dielectric, and MnO2 as the cathode system. Unlike the commercial versions of this device, we will not push the envelopes of safe design for the considerations of higher capacitance at specific voltages.”

The new parts are available in nonstandard case sizes corresponding to the Military CWR09, 19 and 29 styles.

The T497 COTS capacitors range in values from 0.10 µF to 150 µF at voltages ranging from 4 V to 25 V (see the table). This series fits a demand for extended safety considerations. The T497 Series offers many unique options that allow users to customize the product to their specific application needs.

KEMET’s T497 High Grade COTS are suitable for high-end industrial power supplies, military designs, portable communication systems, and other critical filtering and decoupling applications. This product is low profile (0.0500 in. height for case size A through D), which is compatible with PCMCIA type II applications.

The T497 Series has been designed with very low leakage current making it suitable for self-contained or battery-powered products. The T497 is offered with a COTS option with special testing available for surge current, Weibull grading and 100% X-ray inspection. The T497 capacitors are available in RoHS-compliant versions and in standard tin-lead terminations.

Last month, Vishay Intertechnology introduced the TR3 series molded tantalum chip capacitors, which provide ESR values down to 35 mΩ and maximum ripple current values up to 2.07 A (at 100 kHz and 470 µF) (see the table). Low ESR values allow for more efficient filtering in dc-dc converters, while the devices’ ability to handle high currents is key in microprocessor bulk energy storage. The TR3 capacitors target applications in telecom, automotive, computer, industrial, commercial, medical and avionics end systems.

According to the vendor, this product series is notable for its use of an ordering nomenclature that matches that of Vishay’s competitors. This development eases cross referencing of parts among different suppliers.

In addition to providing very low ESR values and a high ripple-current handling capability, the capacitors feature a proven solid tantalum construction that ensures long-term reliability. Outstanding stability over time and temperature further enhances the TR3 devices’ performance and reliability.

TR3 devices are available with 100% tin RoHS-compliant terminations or 90/10 tin/lead terminations on request. Devices in the B, C, D and E case sizes are 100% surge-current-tested. All TR3 capacitors meet EIA 535BAAE and IEC QC300801/US0001 specifications.

Capacitance values for TR3 tantalum chip capacitors range from 0.47 µF to 680 µF with standard capacitance tolerances of 10% and 20% (see the table). Voltage ratings range from 4 Vdc to 50 Vdc. The operating temperature range for the new devices is -55°C to +85°C, or +125°C with voltage derating.

Samples and production quantities of the new TR3 molded tantalum chip capacitors are available now. Pricing in 10,000-piece quantities ranges from $0.08 to $1.00, depending on case size.

Recently introduced tantalum capacitors.

Series Cap values (µF) Tolerance Voltage ratings ESR (mΩ) Case sizes
AVX TCJ Series tantalum polymer capacitors 4.7 to 220 ±20% 2.5, 4, 6.3, 10, 16 25 to 300 A, B, R, C, T, W, Y
AVX TAJ Series 0.1 to 1000 ±20%, ±10% 2.5, 4, 6.3, 10, 16, 20, 25, 35, 50 100 and higher F, K, P, R, S, T, W, Y, X
Vishay TR3 Series molded tantalum chip 0.47 to 680 ±20%,±10%, or ±5% (special order) 4, 6.3, 10, 16, 20, 25, 35, 50 35 and higher A, B, C, D, E
Kemet High Grade COTS T497 Series 0.10 to 150 ±20%, ±10% 4, 6, 10, 15, 20, 25 900 and higher A, B, C, D, E, F, G, H, X

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