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Lead-free SMT capacitors minimize dc leakage

Posted: 11 Nov 2002 ?? ?Print Version ?Bookmark and Share

Keywords:avx? niobium oxide capacitor? ceramic capacitor? oxicap? oxicap noj?

AVX Corp. is among the first passive-components vendors to launch a family of niobium oxide capacitors that claim to solve a number of problems inherent in metal capacitors. The company will unveil the line at the Electronica 2002 trade show slated from November 12 to 15 at the New Munich Trade Show Center in Munich, Germany.

By using a niobium oxide anode in combination with proprietary manufacturing processes, AVX said it is able to offer high-performance, high-reliability and long-lived niobium capacitors that eliminate the drawbacks typically associated with metal ones, such as high leakage, inability to withstand high-temperature reflow, and susceptibility to thermal shock.

Designated the OxiCap series, the solid electrolytic ceramic capacitors fill the performance gap between ceramic multilayer and aluminum electrolytic capacitors, providing a safe, robust, lead-free surface-mount solution, said the company.

The non-burning technology is thermally robust and offers lower derating and light weight because of its material density, said Bill Millman, division quality and technology manager for AVX.

The capacitor technology also virtually eliminates the problems associated with capacitance drop and high dc leakage typically exhibited in aluminum electrolytic capacitors, he said. "Because it is a solid electrolytic capacitor," Millman said, "it does not suffer from the capacitance losses normally associated with high-temperature and long-term operation or from capacitance bias effects when operating close to its rated voltage."

Rail voltages up to 5V suit the capacitors for filtering applications, the company said. The voltage-derating characteristic of the OxiCap is 20 percent, compared with the standard 50 percent for comparable products, thanks to its high reliability and safe-failure mode, AVX said.

The company said one OxiCap capacitor offers ESR values typically achieved with up to 10 aluminum electrolytic capacitors. For example, the NOS series can provide an ESR of 100 milliohms with 330?F at 4V in a D-case size.

In addition, the capacitors offer a more rugged construction and production capability than alternative solutions such as aluminum, aluminum polymer and tantalum polymer capacitors, which are more susceptible to thermal and mechanical shock, according to the company.

The devices are available with voltage ratings of 4V and 6.3V; 2.5V and 10V models are under development. Capacitance values range from 105F in a 1206-size (A-case) package up to 470?F in a 7343H (E-case) package. The operating temperature range is -55C to 105C for the NOJ series and -55C to 125C for the NOS series (the low-ESR version).

The ready availability of the new dielectric may also mitigate supply chain problems, AVX maintains. Millman said that niobium is widely used in other industries but is not dominated for electronics use.

Moreover, he said, the technology to develop this material for use in capacitors is simpler than in metal-based capacitors. "At the outset of our development project, AVX considered the material supply chain to ensure long-term availability for our customers," he said.

In OEM quantities, typical pricing for the OxiCap NOJ series capacitors is approximately 5 cents (A case, 10?F) to 18 cents (D case, 100?F). Delivery is from six to eight weeks. Samples are available immediately.

EE Times

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