Murata’s solution “Ceramic capacitor”
Steadily expands product portfolio while seeking high-reliability
Consistent product development from material to production is our strength

Mr. Moritaro Hagiwara
Chief of merchandise technology section, monolithic capacitor products group, monolithic capacitor products division, Fukui Murata Manufacturing Co., Ltd.

Murata Manufacturing Co., Ltd. is playing an active role in the global market as one of the largest suppliers of chip monolithic ceramic capacitors. In order to precisely satisfy the needs of automotive manufacturers and in-vehicle equipment makers, the company offers a product lineup dedicated to the in-vehicle use aside from the general-use. While increasing the capacity of the capacitors, Murata steadily adds variety. New capacitors responding to the latest needs are released one after another, including high heat resistant products (up to 150°C), small-size products and those with resin electrode that resist heat cycle and distortion in substrate.

An anchor product of chip monolithic ceramic capacitor Murata is developing for in-vehicle use is the GCM series (export version is compatible with AEC-Q200 standard), which meets the reliability requirements from automobile manufacturers. In this series, Murata is actively increasing the capacitance. The movement towards larger capacitance in chip monolithic ceramic capacitors is one of the key trends designers concerned about reliability should notice (See Fig-1), as the system reliability can be improved by replacing current capacitors with chip monolithic ceramic capacitors.

Fig-1. Transition of electrostatic capacity per unit volume

There are three types of capacitors now being used in electronic equipment. That is, (1) Chip monolithic ceramic capacitor, (2) Ta (Tantalum) capacitor and (3) Al (Aluminum) electrolytic capacitor. Of the three, chip monolithic ceramic capacitor is best equipped with excellent features in terms of reliability. “Chip monolithic ceramic capacitors are resistant to electrical strike. Since their tolerance for overvoltage can be as high as 5 to 10 times of regular voltage, the tolerance for ESD (Electro-Static Discharge) or surge voltage improves dramatically. (Mr. Moritaro Hagiwara, Chief of merchandise technology section, monolithic capacitor products group, monolithic capacitor products division, Fukui Murata Manufacturing Co., Ltd.) However, the electric capacitance of chip monolithic ceramic capacitor was smaller in comparison to other types of capacitor, and therefore its application was limited. If the capacitance can be enhanced, these highly-reliable chip monolithic ceramic capacitors can replace conventional Ta capacitors and Al electrolytic capacitors.

Consistent in-house product development covering material to production is Murata’s strength

Murata has been increasing the number of product variety of chip monolithic ceramic capacitor whose capacitance ranges from 4.7µF to 100µF where Ta capacitors have been dominating. In the GCM series, the maximum 47µF (withstand voltage is 6.3V) type is already available. “Its application range will expand in such usage as DC-DC converter circuit installed next to a battery. 47µF type product has already been adopted by Tier 1 suppliers of the in-vehicle equipment. We believe that in 5 to 7 years, the ratio of monolithic ceramic capacitors to total capacitors used in the in-vehicle equipment will grow rapidly.” (Mr. Hagiwara)

Fig-2 Thinning technology of chip monolithic ceramic capacitor
* In this photo, internal electrode is treated by etching process (Click to enlarge)

The key to a larger electrostatic capacitance of a chip monolithic ceramic capacitor is to reduce the thickness of dielectric layers. Chip monolithic ceramic capacitors consist of multiple layers of dielectrics in ceramic. As the number of the layers increases, the electrostatic capacitance increases. In other words, the capacitance can be improved without making the product physically larger, if the number of layers can be increased by thinning the dielectrics. (See Fig-2). However, a thinner-layer could result in the degradation of voltage resistance. Technologies such as to refine the particles of dielectrics, and to flatten electrodes and dielectric layers are indispensable. “In order to strike a balance between thinner dielectric layers and improvement of product reliability, various improvements in a broad range covering from material, device design, to manufacturing process are integral. Murata has a consistent system for chip monolithic ceramic capacitors: we develop everything from materials, manufacturing equipment to capacitor products in-house, and that is our strength in pursuing larger-capacitance.” (Mr. Hagiwara)

Fig-3. Trend of miniaturization in in-vehicle chip monolithic ceramic capacitor

Murata already offers small-size chip monolithic ceramic capacitors developed by the thinning technology of dielectrics. They are GCM15 series, or so called 0402(EIA)-size (1.0 x 0.5mm) products and GCM03 series, or so called 0201(EIA)-size (0.6 x 0.3mm) products. “As the number of electronic equipment installed into the limited space of a vehicle increases, the demand for miniaturization will increase. Although the current demand concentrates on0603(EIA)-size (1.6 x 0.8 mm) products, I think the demand for 1005 will increase dramatically in the next five years. I also believe that the demand for 0201(EIA)-size (0.6 x 0.3 mm) will gradually increase.” (See Fig-3) (Mr. Hagiwara)

Lineup of 150°C guaranteed products is expanding

One of the particularly stringent requirements posed on in-vehicle electronic components is operating temperature range. The temperature limit for the most chip monolithic ceramic capacitors used in consumer electronics is 85°C, while that of GCM series made for in-vehicle use is as high as 125°C. This is because the in-vehicle equipment is often installed in the places where surrounding temperature can easily rise. And now the products with even higher operating temperature limit of 150°C are needed in the market. “It reflects the trend of collaborative R&D between mechanical technology and electronics technology. There is a tendency to directly mount electronic circuits in such places as engine or gear boxes where temperatures can go up to the highest level in the car. (Mr. Hagiwara)

Quickly responding to such needs, Murata offers the products whose operational temperature range was expanded to -55°C - +150°C. “In order to expand the range, we have improved dielectric material.” (Mr. Hagiwara) However, when the surrounding temperature reaches around 150°C, mounting with solder becomes a problem. Therefore, the company also offers GCG series with 150ºC-guaranteed products that can be mounted with conductive adhesive. By replacing Ni/Sn layer on Cu electrode surface of existing product with Ag/Pd, use of conductive adhesive became possible.

A product with crack prevention measures was developed

Fig-4. Chip monolithic ceramic capacitor adopting resin external electrode

Furthermore, responding to the needs of auto makers and in-vehicle equipment suppliers who seek higher reliability, Murata developed GCJ series using conductive resin in the base of external electrode. (See Fig-4) The major characteristic of the product is that the structure of external electrodes is devised so as to prevent a crack from occurring in the internal dielectrics when external stresses are applied. For example at temperature cycle test, when thermal expansion or shrinkage rates differ between printed circuit board and ceramic capacitor, external stresses are applied through external terminals to the inside of a ceramic capacitor. Also, when a printed circuit board is distorted by some external shock, stresses are added between the internal dielectric and the external terminal. Those are the cases cracks can run in the internal dielectrics. “As the capacitance becomes larger, there will be more chances for the capacitors to be used in the circuit for high current. If cracks are generated in such a high-current circuit, the accidents accompanied with heat or smoke may happen. (Mr. Hagiwara)

So, Murata has adopted a unique structure in GCJ series: a resin electrode is formed on the Cu electrode located in the innermost layer of an external electrode, and is coated with Ni/Sn plating film. Furthermore, stresses added to the internal dielectrics from outside are alleviated by optimizing the shape and other factors of the external electrode. When great stresses are added, the resin electrode will be peeled off, thus preventing dielectrics from the stresses and therefore from cracking as well. This product is already used in some in-vehicle equipment. “In the near future, we will be offering products with operating temperature limit of 150°C.” (Mr. Hagiwara)