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Method for low ESR, high frequency tantalum capacitors

IP.com Disclosure Number: IPCOM000008885D
Publication Date: 2002-Jul-19
Document File: 3 page(s) / 41K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for low effective series resistance (ESR), high frequency tantalum (Ta) capacitors. Benefits include improved performance and improved design flexibility.

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Method for low ESR, high frequency tantalum capacitors

Disclosed is a method for low effective series resistance (ESR), high frequency tantalum (Ta) capacitors. Benefits include improved performance and improved design flexibility.

Background

              Fabrication of Ta capacitors starts with high surface area Ta powders. After power compaction and insertion of Ta wires, an anodization process is used to form Ta2O5 dielectric. Cathods are made with either MnO2 or a conducting polymer. One of the main advantages for using Ta capacitors is the high capacitance density due to the high surface area generated by fine Ta powders (see Figure 1). However, a higher ESR and resistance capacitance (RC) ladder effect is the by-product as high resistance and series resistance occur along the powders linked by the neck region formed by compaction.

      Ta capacitors offer high capacitance density and good high temperature performance. However, high ESR and significant capacitance rolloff at high frequency (100 KHz and above) have prevented them from being used for voltage regulation for high-performance CPUs. To achieve lower ESR and improve capacitance rolloff, Ta capacitor suppliers conventionally use multiple anodes and conducting polymer (instead of MnO2, which has a lower conductivity). Multiple anodes result in a higher cost. Conducting polymer helps to improve the ESR and high-frequency performance to some extent but further improvement is still required to catch up with an increasing demand for voltage regulation.

General description

      The disclosed method is a design to use Ta capacitors with lower ESR and improved high-frequency performance.

      The key elements of the method include:

·        Ta capacitors using different Ta power morphology, such as plate or cube shape, which provides a greater surface contact after compaction

·        Ta capacitors using doped/coated Ta powder with conducting metals (such as Al, Ag, and Cu)

·        Ta capacitors using conducting polymer mixed/doped with conducting metal powders/flakes (such as Al, Ag, C, and Cu)

Advantages

              The disclosed method provides advantages including:

·        Improved ESR and high-frequency performance for Ta capacitors

·        Im...