Electronic Design

Tantalum Is Tantalizing, But Ceramics Are The Real Catch

In 1999, Murata Electronics first began to see industry acceptance of ceramic capacitors as substitutes for hard-to-get tantalum caps. Passive-component producers had adapted to the needs of their customers, producing ceramic capacitors with the same, if not superior, benefits as tantalum. And by 2001, caps made from ceramics and other materials proved they had enough advantages over their tantalum counterparts to become permanent replacements. While some applications are still better served by a tantalum capacitor, most design engineers now recognize that ceramic caps are the caps of the future.

The widespread adoption of ceramic caps represents a milestone in the history of electronics. Tantalum capacitors have always been desired for electronics because of their high density, high melting point, and high capacitance. Plus, tantalum is corrosion-resistant to most acids over a range of temperatures. Such features have made the substance increasingly useful over the years, particularly in miniaturized electrical circuitry.

It wasn't until after World War II that companies began using ceramics in electronics. Yet even then, ceramics weren't as popular as products made with tantalum. In part, this was because ceramics couldn't provide the same capacitance values as tantalum. Though tantalum wasn't perfect (it's nearly as rare as uranium), an alternative simply wasn't necessary. The mindset of "tantalum equals electronics" was hard to overcome. So, what happened?

A scarcity of tantalum powder converged with the rising demand for passive components, producing shortages of tantalum parts. After years of using tantalum parts, manufacturers suddenly needed other options. Capacitor vendors responded with research and development efforts that led to improved engineering and production methods for ceramic capacitors.

Many customers were surprised by the way the resulting improvements in design combined with the inherent characteristics of ceramics. The design modifications led to several advantages, including ease of placement, low equivalent series resistance (ESR), nonpolarization, and high voltage. Lower ESR is particularly important because it lets designers use lesser-value capacitors without degrading performance. But even more significant is the fact that ceramic caps are cost-effective.

As customers realized the design flexibility offered by ceramics, demand for the material surged. Component development engineers could quickly adjust the design of ceramic caps, allowing for drop-in replacements in decoupling, filtering, by-passing, and smoothing applications. It even became possible to customize the ceramic caps in a timely cost-effective manner. In fact, lead times dropped from 52 weeks for tantalum caps to eight weeks for ceramics. Meanwhile, ceramic replacement caps reached capacitance values close to those of tantalum parts.

Although smaller caps can't achieve the same capacitance as larger ones, they do require less raw material. And, a reduced demand for raw material lessens the likelihood of a material shortage, which raises cost. Since tantalum capacitors are typically much larger than the ceramic type, using ceramic caps can reduce component cost and size. Another benefit is that nickel, the electrode material used to make ceramics, is easier to find and mine than tantalum.

The future of ceramic capacitors is very promising. As consumers crave smaller, more sophisticated products, manufacturers will place greater importance on the design flexibility, size, and cost of capacitors. While tantalum is still a useful material, ceramics have proven their value in the market and will continue to do so.

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