Leader Talk

Ceramics Are Now Drawing Attention as Key Materials for Automotive Equipment, Opening Up a New Era for Capacitors and Automobiles

More than 20 years ago, Murata launched its first series of monolithic ceramic capacitors for use in vehicles. Since then, the company has played a part in providing electric control of core automotive functions. With the introduction of hybrid electric vehicles (HEVs) and electric vehicles (EVs) and the increasing use of information technology in vehicles, Murata capacitors have found even more applications in the automotive industry. The company still continues to develop its ceramics process and capacitor technology further to meet automotive customers' increasing requirements for smaller size and higher capacitance.

Kenichi Mizuno
Vice President, Capacitor Division 2, Components Business Unit

Mizuno joined Fukui Murata Manufacturing in 1983, where he was appointed to the positions of process/product development, product engineering and production technology for monolithic capacitors. Between 1995 and 2000, he worked at Murata Electronics (UK) Ltd. and became responsible for product engineering in 2000. He has been serving as Director for Capacitor Division 2 since November 2009. In this way, Mizuno has always been involved in capacitor operations. Mizuno's favorite pastime is gardening.

We always face the challenge of fulfilling automakers' stringent requirements.
This is only natural because in-vehicle systems can threaten occupants' lives if they are defective. Automakers therefore demand that suppliers like Murata meet the highest reliability standards.
In its efforts to meet customer needs, we have continued to help our customers by making appropriate proposals from the perspective of component engineering.
We have conducted our research and development with a clear vision of what cars will be like in a decade. This has allowed us to achieve the high reliability of Murata monolithic ceramic capacitors for in-vehicle use.

Clearly-Differentiated Product Series Tradition of Meeting Stringent Requirements for Reliability

Murata clearly separates its monolithic ceramic capacitor product series into two categories — automotive and consumer-product. Products for in-vehicle use are required to have much higher reliability standards than consumer-product components. They share the basic design, but consumer-product components are only required to withstand temperatures of up to 85°C, while in-vehicle products are expected to work properly at 125°C or even as high as 150°C. Capacitors are used by applying voltage to their dielectric material. Capacitors used in a hot environment require technology that reduces the number of defects in the dielectric material. In other words, such capacitors must be designed right from their materials to ensure uniform crystallization. In addition, capacitors for in-vehicle use must be more reliable than consumer-product components because they have longer lifecycles. Capacitors can break down during a prolonged period of use. We design capacitors for in-vehicle use to have longer service lives and control them by more stringent evaluation criteria. In this way, we take a range of measures to meet the reliability, durability, and safety requirements for capacitors for in-vehicle use. To this end we employ different material design and service life design for this type of capacitors.

Murata Capacitors Set an Example for Electronic Components for Vehicles By Trying to Pick Up Automaker (Tier 0) Needs

Automobiles have a long time to market. We are now working on products that will be put into practice in 3 to 5 years. In the past, we didn't often receive requests directly from automakers. But with the increasing use of information technology and electronics in vehicles in recent years, we have more often heard automakers' requests regarding electronic components. EVs and HEVs were originally designed as strategic next-generation products. Automakers badly feared of defects found in these vehicles after market introduction and therefore were very cautious about selecting electronic components used in them. They were deeply involved in the design and development processes of Tier 1 and Tier 2 suppliers, where they explained the types of components they wanted to use in their cars and how they wanted to use them. Murata has also discussed various issues with automakers to offer components that meet their standards. Our communication with them greatly helps us create new products.

Capacitor

A passive two-terminal electrical component used to electrostatically store and release an electric charge (electric energy) in an electric field. The monolithic ceramic capacitor is a chip-type product consisting of many layers of dielectric ceramic sheets and electrodes. Taking advantage of the high specific permittivity of ceramics, it features high capacitance in its small size. The film capacitor features dielectric sheets made of plastic films. It is characterized by high precision as it causes only slight fluctuations in capacitance with temperature changes. The aluminum electrolytic capacitor's dielectric layers are made of oxidized films formed on the surfaces of the aluminum electrodes. The very thin dielectric layers make it possible to provide high capacitance.

Monolithic Ceramic Capacitors for ECUs

The number of electronic control units (ECU) installed in a vehicle is on the increase. This is because of the increase in sophistication and the number of control systems in both the powertrain (e.g. engine control) , and vehicle body (e.g. air-conditioning control) . The number of ECUs in a vehicle has increased from approximately 30 in the early 1990s to around 50 or 60 in recent years. With this increase, it has become increasingly important to downsize ECUs for space-saving purposes. The number of monolithic ceramic capacitors used in an ECU ranges from a few tens to a few hundreds. With the increase in the number of ECUs in a modern vehicle, the number of monolithic ceramic capacitors used in one now totals in the neighborhood of 1,000 to 3,000.

Heat resistance and possibility to reduce size and weight make monolithic ceramic capacitors increasingly important in-vehicle components.

Preventing Cracks By Reducing Stress: Conductive Resin and Metallic Terminals

Let me give you an example. During the production process of in-vehicle equipment, the printed circuit board can be bent, applying bending stress to capacitors mounted on it. This possibly causes cracks in the joints between external electrodes and ceramics. Such cracks short-circuit the terminals, resulting in an overcurrent. The defective device then produces heat. In the worst-case scenario, it may cause fire, possibly leading to a life-threatening accident. To prevent this short-circuiting, Murata covered the electrodes on the ceramic's end faces with conductive resin before plating the surfaces. The conductive resin reduces stress applied to the joints between the ceramics and external electrodes to prevent cracks from being generated. Another solution is available: Adding metallic terminals to the external electrodes to avoid direct contact with the substrate can prevent the generation of cracks. The elasticity of the metallic terminal is also used to reduce the stress generated by the expansion and shrinkage of the printed circuit board due to changes in temperature, thereby preventing cracks from being caused. Despite their high-heat resistance, ceramics are vulnerable to bending and tension stress. Before the above solutions were developed, quite a few customers avoided using large monolithic ceramic capacitors. This was because cracks were generated more easily with an increase in capacitor size. We are convinced that our solutions have eliminated this problem.

Upsizing and Downsizing Monolithic Ceramic Capacitors Play a More Important Role in Automotive Engineering

In keeping with the increasing use of electronics and information technology in vehicles, automakers demand large-current, high-voltage applications. In-vehicle power electronics employ film capacitors and aluminum electrolytic capacitors. The drawback is that they are vulnerable to heat. Against this backdrop, silicon carbide (SiC) semiconductors are a focus of attention as a solution to increase the efficiency of in-vehicle power converter circuits such as inverters, simultaneously reducing their size and power consumption. An advantage of SiC semiconductors is that they can operate at high temperatures. Ceramics are now drawing attention as heat resistance is required from components used near SiC semiconductors. For the past decade, Murata has conducted research into large monolithic ceramic capacitors for large current and high voltage applications. These capacitors are now being put into practical use. At the same time, automakers (Tier 0) aim to minimize the size and weight of in-vehicle components. To meet this need, even smaller and thinner monolithic ceramic capacitors are being developed. One example is a product that can be integrated directly in the printed circuit board to lower the profile maximally. So we now see trends in opposite directions — upsizing for larger current and high voltage, and downsizing for lower profile. In the future, automotive engineering will evolve in a range of directions. These include environment-friendly drive systems such as EV and HEV, advanced driving assistance systems (ADAS) to improve safety measures, and increasing use of information technology to provide even more attractive infotainment. These developments will surely make monolithic ceramic capacitors more important for vehicle technology.

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