Technical Library

Trends Involving Cutting-Edge Automotive Aluminum
Electrolytic Capacitor Technology

NICHICON CORPORATION

NICHICON CORPORATION has maintained steady growth in the automobile and transportation-related areas by providing full-fledged support for eco-cars. In particular, electric and hybrid vehicles are growing in popularity because of their small environmental footprint and fuel economy. These vehicles are expected to become even more widespread as more infrastructure is put in place to facilitate their use. In recent years, development has been underway on vehicles equipped with safety features and automatic driving mechanisms such as the Advanced Driver Assistance System (ADAS), On-board components are also being miniaturized to make vehicle interiors more comfortable. Correspondingly, demand is increasing for automotive capacitors that are smaller, have higher capacities and can withstand severe or high-temperature environments.
Nichicon has developed two cutting-edge technologies that respond to these demands: aluminum electrolytic capacitors and conductive polymer hybrid aluminum electrolytic capacitors.

■Aluminum Electrolytic Capacitors
Aluminum electrolytic capacitors are primarily composed of aluminum and have a large capacitance per volume when compared to other types of capacitors. Aluminum itself is also one of the most inexpensive metals, allowing high-capacity capacitors to be manufactured at a low cost. The aluminum electrolytic capacitor's dielectric is an oxide film (Al2O3) formed on the surface of high-purity aluminum foil. This oxide film has a higher relative permittivity than other dielectrics and can be formed in exceedingly thin and even layers, giving it high capacitance. An aluminum electrolytic capacitor is formed by placing anode and cathode foil separated by layer of paper. These materials are wound together into a cylindrical shape, impregnated with an electrolytes, inserted into an aluminum case and sealed. The foil surface is roughened (through etching) to increase its effective area, efficiently boosting the capacitance. The separator placed in between the foils acts as an insulator, and components that have not absorbed electrolytes display little static capacitance. This is due to the oxide layer on the foil surface does not function effectively and is why the electrolytes are referred to as the true cathode. As electrolyte characteristics are closely related to capacitor characteristics, the electrolytes we use have compositions that match the capacitors' intended use.

■UCV and UCH Series of Aluminum Electrolytic Capacitors
In recent years, device functionality is being rapidly optimized in the digital appliance and information communication fields, as well as the automotive sector. Demand is rising for smaller devices with higher capacities as a result. NICHICON has responded to this demand with the UCL and UCM Series of miniature and high-capacity capacitors. In April 2015, we launched the UCV Series (Photo 1), which offers the highest capacitance per volume in the industry. Later, in October 2017, we expanded our line of products rated at 16V. Until now, products in the UCL and UCM Series have been used in airbag control circuits, power sliding doors and blower motors. The UCV Series allows for a lower number of capacitors per set and contributes to further functional optimization. We enhanced storage efficiency by using a thin separator and a thinner high-capacity cathode foil and further reduction by increasing the surface area of its anode foil. The UCV series' dimensions range is φ6.3x7.7L to φ10x10Lmm, its rated voltage range is 16 to 35V, its capacitance range is 220 to1500μF, and its temperature range is -55 to 105C. The UCV series' has an endurance rating of 2000 hours at 105C and ripple currents between 600 to 1190mArms at 105 and 100kHz.
Meanwhile, in the automotive transportation-related fields, the practice of arranging electronic circuits within and around the engine compartment to make vehicle interiors more comfortable and optimize performance is becoming more common. In response, demand is increasing for on-board components that are resistant to severe high-temperature environments. Also in demand are products appropriate for use in a wide range of temperatures, including low-temperature environments. In addition to the wide temperature requirements there is a demand for enhanced reliability, we must maintain product features that are stable and durable for long periods of time. In particular, NICHICON is placing more focus on products' equivalent series resistances (ESRs) and the corresponding endurance-tested low-ESR products so that it can achieve acceptable ESR variations at the design stage. Facing further market demand for smaller products with lower ESRs, we developed the UCH Series (Photo 2), which offers the industry's highest performance among endurance-tested low-ESR products. We also expanded our line of capacitors rated at 25V. Through this product series, we can respond to various automotive demands and contribute to the creation of energy-saving set capacitors with longer lives. The UCH Series offers the advantage of cutting the current product's initial endurance-test low-ESR growth rate by 75% for product dimensions of φ6.3x7.7Lmm. We achieved this reduction by adopting low-evaporation, low-resistance electrolytes and by optimizing internal specifications. The UCH series is also smaller than the UCZ series, and its application in peripheral driving devices, such as engine control units and DC-DC converters, is spreading. The UCH series dimensions are φ6.3x7.7L to φ10x10Lmm, its rated voltage range is 25 to 35V, its capacitance range is 47 to 560μF and its category temperature range is -40 to 125C. The UCH series' has endurance life ratings of 2000 hours at 125C and ripple currents of 197 to 500mArms at 125C and 100kHz.

(Photo 1) UCV Series of low-impedance chip-type aluminum electrolytic capacitors

(Photo 1) UCV Series of low-impedance chip-type aluminum electrolytic capacitors

(Photo 2) UCH Series of endurance-tested chip-type aluminum electrolytic capacitors

(Photo 2) UCH Series of endurance-tested chip-type aluminum electrolytic capacitors

■GYA and GYB Series of Conductive Polymer Hybrid Aluminum Electrolytic Capacitors
Demand is rising for aluminum electrolytic capacitors that are better at withstanding high temperatures and have lower resistances and higher ripple currents. In response to these demands, NICHICON developed its GYA series of conductive polymer hybrid aluminum electrolytic capacitors, which are guaranteed at 125C, (Photo 3) and began mass producing them in April 2017. Furthermore, we began mass production of our GYB Series of conductive polymer hybrid aluminum electrolytic capacitors, guaranteed at 105C, in April 2018. This series was developed in response to demands in fields such as industrial equipment, telecommunication base stations, medical equipment and consumer electronics.
 In these capacitors, we utilized hybrid electrolytes, which combine liquid electrolytes with electro conductive polymers, and a unique electro-conductive polymer-forming technology to achieve low ESR performance. Being electro-conductive, these polymers exhibit minimal changes in characteristics in high-frequency and low-temperature environments, and can contribute to further device optimization (Table 1). Additionally, by developing electrolytes compatible with electro-conductive polymers we have achieved the low leakage currents that electrolytic are known for without sacrificing the performance of the electro-conductive polymers. We have extended the endurance lives of our capacitors by utilizing electro-conductive polymers that are stable in high-temperature environments.
 GYA Series dimensions are φ6.3x5.8L to φ10x10Lmm, its rated voltage range is 25 to 63V, its capacitance range is 10 to 330μF, and its category temperature range is -55 to 125C. The series' ripple current is 700 to 2000mArms at 125C and 100kHz and its guaranteed endurance life is 4000 hours at 125C (with superimposed ripple). The GYB Series' dimensions, rated voltage range and capacitance range are the same. However, its category temperature range is -55 to 105C, its high ripple current is 1.2 to 1.4 times higher than the GYA series at 1000 to 2500mArms (105C, 100kHz), and it offers the best guaranteed product life in the industry with 10,000 hours at 105C (with superimposed ripple). We achieved this long guaranteed product life by optimizing the electro-conductive polymers' film formation process. Additionally, both series' φ8x10L and φ10x10Lmm sizes can be made with vibration-resistant structures (guaranteed up to 30G).
 Moving forward, we believe the applications for conductive polymer hybrid aluminum electrolytic capacitors will begin to expand even more. In particular, the automotive market is performing steadily and vehicle electrification and optimization will progress further and further as autonomous driving and ADAS become more commonplace. In response to these trends, we are working to increase the capacities and temperature resistances of our conductive polymer hybrid aluminum electrolytic capacitors. We forecast that we will reach a guaranteed temperature of 135C by using the electro-conductive polymer film formation technology we cultivated through our GYA and GYB Series and by developing and utilizing electrolytes that do not easily evaporatein high-temperature environments. As for increasing capacity, we will achieve this by making several of our materials thinner and applying high-capacity foil. We also plan to respond to wide-ranging needs in consumer markets such as home electronics, communications equipment and industrial equipment by expanding our lineups and product sizes.

(Photo 3) GYA series of conductive polymer hybrid aluminum electrolytic capacitors

(Photo 3) GYA series of conductive polymer hybrid aluminum electrolytic capacitors

(Photo 4) GYB series of conductive polymer hybrid aluminum electrolytic capacitors

(Photo 4) GYB series of conductive polymer hybrid aluminum electrolytic capacitors

(Table 1) Frequency and temperature characteristics of
conductive polymer hybrid aluminum electrolytic capacitors

(Table 1) Frequency and temperature characteristics of
conductive polymer hybrid aluminum electrolytic capacitors

NICHICON CORPORATION
From the Dempa Shimbun, Aug. 23, 2018

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