Multilayer Ceramic Capacitors Indispensable to High-performance Semiconductor Devices
Resistors, capacitors, and inductors are passive parts often regarded as somewhat minor components, but in fact, they are indispensable to cutting-edge electronics. In particular, multilayer ceramic capacitors are crucial to leading-edge semiconductor devices. Without them, we would not be able to count on devices to operate properly. Some in the electronics industry predicted that capacitors would be eventually integrated into semiconductor devices. In reality, however, the importance of multilayer ceramic capacitors tends to increase as semiconductor devices evolve.
A multilayer ceramic capacitor is smaller than a particle of sugar. Are you aware of the roles this extremely tiny component plays in electronic devices? It has such important roles as supporting the power supply required for semiconductor devices, and eliminating noise that may result in a malfunction or performance degradation. Without multilayer ceramic capacitors, the semiconductor devices manufactured using advanced leading-edge process technology, such as microprocessors, DSPs, microcomputers, and FPGAs, could not be expected to operate properly.
History of Size Reduction and Capacitance Enhancement
The size of the multilayer ceramic capacitor market is presently the largest among the markets for various types of capacitors, namely aluminum electrolytic capacitors, tantalum electrolytic capacitors, and film capacitors. In 2008, 627.8 billion multilayer ceramic capacitors were shipped in Japan and domestic sales reached JPY305.9 billion (according to "Yearbook of Machinery Statistics" published by Japan's Ministry of Economy, Trade, and Industry). Aluminum electrolytic capacitors took second place with shipments of 18.2 billion units and sales of JPY174.3 billion. There is a wide gap between first and second place.
Multilayer ceramic capacitors are currently the top-selling product in the capacitor market, but market acceptance was slow to develop when they were first introduced. It was a U.S. company that first came up with the idea of a multilayer ceramic capacitor. In the midst of the Apollo program, which was launched in 1961, a multilayer ceramic capacitor was invented to meet the need for a compact, high-capacitance capacitor. The new capacitor was designed to have the electrodes formed in a number of laminated dielectric layers so that it has a high capacitance in a small size (fig. 1).
The layers of the dielectric material and internal electrodes are laminated on top of each other, thus achieving a greater capacitance.
Murata Manufacturing Co., Ltd. introduced this technology ahead of others and put the first product on the market in 1965. It was a 100pF model targeting LC resonant circuits in AM radios and it consisted of 50μm dielectric film layers. The product used titanium oxide (TiO2) as the dielectric material. "When we first launched the product, it did not sell at all," said Kiminori Yamauchi, director of the Components Business Unit of Murata. "But after an ultra-slim radio dubbed 'Paper Radio' was released, the market for multilayer ceramic capacitors grew rapidly because they were smaller than any other type of capacitor."
The history of multilayer ceramic capacitors since then can be described as the "history of size reduction and capacitance enhancement." In general, the capacitance C of a capacitor is expressed as follows:
where ε, S and d denote the dielectric constant, the area of the electrodes, and the distance between the electrodes (the thickness of the dielectric body), respectively. In short, there are only two ways to increase the capacitance in a certain volume: either to use a material with a higher ε value or to reduce the thickness of the dielectric body.
Murata used titanium oxide as the dielectric material during the initial phase after product release, but introduced barium titanate (BaTiO3) at a relatively early stage. Since then, the relative dielectric constant has been continuously increasing as a result of improvements made to the material. So far, the value has reached approximately 3,000. The relative dielectric constant of titanium oxide is several dozen at most. In other words, that of BaTiO3 has become two orders of magnitude greater than that of titanium oxide.
The thickness of the dielectric material was gradually reduced from 50 μm during the initial phase to 0.5 μm at present. Thus, compared with the initial values, the dielectric constant is 100 times higher, while the thickness is 1/100. With a thickness reduced to 1/100, the number of layers can be increased 100 times. Therefore, in terms of capacitance, it is equivalent to a million-fold increase with the same size. In terms of size, on the other hand, it means that a 1/1,000,000 reduction is possible with the same capacitance.
To be continued in "part 2 of 2," which will describe application trends and the roles of capacitors in each application.
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* The content of this article, from the February to March 2010 issue of "Tech On!" Nikkei Business Publications, Inc., was restructured.
* For more details on Murata Manufacturing's multilayer ceramic capacitors, please refer to the following: