Top 10 capacitors for harsh environments

Emerging applications like 5G communications and evolving automotive requirements such as for advanced driver-assistance systems (ADAS), autonomous driving, and on-board chargers for electric vehicles are requiring higher-performing capacitors. This can mean anything from higher capacitance values to higher operating temperatures to ruggedness to operate in harsh environmental conditions. At the same time, board space is at a premium.

In many cases, capacitor makers are developing new processes and designs to meet the growing demand. These are across dielectrics from ceramic to film to polymer.

Here are 10 of the top capacitors introduced over the past year that meet some of these new requirements.

Targeting extreme harsh environments such as aircraft and satellite applications, Exxelia has developed a new film dielectric that the company calls a breakthrough technology for film capacitors. The new Miniature Micro-Layer (MML) capacitors offer ultra-high energy density, claiming the highest capacitance per volume for film capacitors. As a result, the film capacitor family also saves board space and weight while lowering component count.

The new film dielectric, rather than being wound in a cylindrical configuration, is constructed from stacked layers of polymer film, similar to MLCCs, said Exxcelia. “This new dielectric material allows for much higher capacitance per volume that allows for significant weight and space savings.”

Key specifications include a wide capacitance range of 1 μF to 1,000 μF and voltages from 50 V to 1,000 V. The operating temperature range is –55˚C to 140˚C. There is no voltage derating up to 125˚C.

The company calls the MML capacitors a game-changer with an energy density of 400 J/dm³. This allows for a tremendous reduction in size and weight compared with traditional polypropylene or polyester dielectrics, said Exxelia. The technology also offers an increased operating temperature up to 140˚C and transient voltage protection.

In addition, the MML capacitors allow for low-profile configurations. The company also noted several studies using control and DC-link functions for aircraft applications that show about a 50% reduction in size and weight compared with other film technologies. Compared with MLCC capacitors, one study shows a 70% to 90% reduction in weight with no capacitance derating with voltage applied and a low drift of <5% through the temperature range.

A single MML capacitor can replace clusters of stacked MLCCs, which also delivers the increased reliability of film dielectrics, said Exxelia. Also, compared with stacked MLCCs, the MML capacitors offer inherent self-healing properties together with low drift in capacitance over the temperature range (±5% max), as well as low dielectric losses, and they are not prone to cracking due to thermomechanical stress.

Applications for the new capacitor include power supplies, DC-links, AC/DC/AC power converters, charge/discharge, or power-generation functions in commercial/military aircraft, satellite platforms and payloads, launchers, defibrillators, and downhole tools.

The MML capacitors are available in four different series with through-hole, SMD, or copper terminals. Samples in the DIL configuration are available now with the following ratings: 10 µF, ±10%, 600 VDC; 13.5 µF, ±10%, 600 VDC; and 36 µF, ±10%, 600 VDC.

New designs for automotive

Murata Manufacturing Co., Ltd. has introduced an ultra-thin LW-reversed, low-equivalent-series-inductance (ESL) multilayer ceramic capacitor (MLCC) for 4-VDC–rated automotive applications that helps lower impedance. As ADAS evolves to increase safety and in the future deliver self-driving vehicles, ICs for in-vehicle equipment have become increasingly high-performance, which challenges designers to lower the power supply lines’ impedance, said Murata.

Targeting in-vehicle ADAS applications, the LLC152D70G105ME01 decoupling capacitor can be implemented on the back of a processor package. This contributes to lower impedance on a power supply line, thanks to Murata’s proprietary thin-layer technology for ceramic elements and thin-sheet formation technology, said the company. The AEC-Q100–compliant MLCC, measuring 0.5 × 1.0 mm with a maximum thickness of 0.22 mm, can also sit close to the main processor on the motherboard.

In addition, the LW reverse construction flips the electrodes by 90˚ so they are positioned on the long side of the rectangular chip. This reverses the length-to-width ratio, providing noise suppression in high-frequency applications, said Murata.

Key specs include a capacitance value of 1.0 µF ±20% and an operating temperature range of –55˚C to 125˚C. The MLCC also is RoHS- and REACH-compliant.

Aimed at automotive applications in 48-V on-board supplies, TDK Corp.’s recently introduced B40640B* and B40740B* series hybrid polymer capacitors offer a very high ripple current capability, which was increased by up to 29% compared with predecessors. The ripple current capability is now up to 35 A (20 kHz, 125˚C).

The capacitors offer a capacitance range from 390 µF to 720 µF, a rated voltage of 63 V, and extremely low equivalent series resistance (ESR) of 3.9 mΩ at 20 kHz and 20˚C as an example. Even at an operating temperature of –40˚C, the ESR is just 5.4 mΩ, said TDK.

The rugged capacitors offer a high vibration strength of 60 g and can be operated at up to 150˚C. Depending on the capacitance values, the dimensions vary between 14 × 25 mm and 16 × 30 mm (D × H). The RoHS-compatible capacitors are available in axial-lead (B40640B*) and solder-star (B40740B*) designs. These devices target automotive applications in 48-V on-board supplies.

Also designed for harsh automotive environments is Kemet’s (part of the Yageo Group) R53 series of miniature, polypropylene-film X2 electromagnetic interference (EMI)-suppression capacitors. They can also be used in industrial, consumer, and energy applications that require a smaller, high-capacitance X2 class solution for suppressing EMI.

 

The R53 series offers capacitance values from 0.1 µF to 22 µF. On average, the X2 EMI capacitors are 60% smaller in volume than competitive devices, which impact board space, weight, cost, and reliability. Lead spacing ranges from 15 mm to 37.5 mm.

Compared with competitive solutions, Kemet said they either have larger dimensions or require capacitors in parallel in the design. With a rated 310 VAC at 50 or 60 Hz, the R53 series is intended for use in Class X2 line-to-line applications or in series with the AC mains.

The AEC-Q200–qualified capacitors are well-suited for AC/DC converters in on-board chargers for xEVs, smart-grid hardware, EMI filtering in variable-frequency drivers, LED drivers, and high-energy–density applications such as capacitive power supplies, which often require operation in harsh environmental conditions.

The R53 series features a metallized polypropylene film encapsulated in a self-extinguishing resin and a shell that meets UL 94 V-0 requirements. The metallized polypropylene film combined with an internal parallel construction provides self-healing properties to prevent catastrophic failure and extend service life, said Kemet.

Targeting high-temperature automotive applications, AVX Corp.’s TCO Series of high-temperature, automotive-grade polymer chip capacitors are rated for operating temperatures up to 150˚C at category voltage. They also boast low leakage current (DCL) and a benign failure mode. Target applications include high-temperature, low- and medium-power automotive, industrial, and telecommunications applications.

These polymer capacitors meet AEC-Q200 Stress Test Qualification for Passive Components requirements, which ensure stable performance at 85˚C, 85% relative humidity, and rated voltage for up to 1,000 hours.

Based on AVX’s TCQ Series automotive polymer capacitors, the capacitors feature J-lead construction comprised of tantalum anodes, tantalum pentoxide (Ta₂O₅) dielectrics, and conductive polymer electrodes that exhibit a benign failure mode under recommended use conditions, said the company.

The series exhibits low DCL at 0.1 CV and basic reliability of 1% per 1,000 hours at 85˚C and rated voltage with 0.1 Ω/V series impedance and 60% confidence, said AVX.

The TCO Series is currently available in a D-case (EIA Metric 7343-31) package and is rated MSL 3 per J-STD-020. Key specifications include a capacitance of 10 µF ±20% tolerance and a rated voltage of 50 VDC at 105˚C, with a maximum of 50-µA DCL and 150-mΩ maximum ESR at 100 kHz. The operating temperature ranges from –55˚C to 150˚C.

The capacitors are RoHS-compliant, lead-free–compatible, and capable of withstanding three reflow cycles at 260˚C. These devices are suited for automotive cabin control, infotainment, and comfort systems; body electronics that manage safety, power management, and diagnostic systems; and aftermarket electronics such as dash cams, radar detectors, navigation systems, subwoofers, amplifiers, and headrest monitors, as well as DC/DC converters and coupling/decoupling circuits in industrial and telecommunications equipment.

 

Safety capacitors

While addressing harsh environment applications, some of these new capacitors can also be used in the renewable-energy market for applications such as wind-turbine monitoring and solar inverters.

One example is Cornell Dubilier’s PCD series of high-current, AC-harmonic–filter capacitors that offer dual, built-in, fail-safe protection systems, one at each end of the capacitor. While these fail-safe devices are designed to prevent case rupture at end of life, PCD series capacitors are designed to be exceptionally reliable, with a service life of over 60,000 hours at rated voltage and temperature, said CDE. A self-healing, metalized dielectric construction adds to their reliability.

Typically, these types of capacitors have one open-circuit pressure device located under the top cover that requires the device to be mounted from its bottom stud. “With the addition of a bottom-pressure device, the PCD’s terminals can be fixed to a rigid busbar, allowing for activation of the bottom safety device when proper clearance is provided at the bottom,” said CDE.

The PCD series is offered with capacitance ratings ranging from 20 µF to 125 µF at voltage ratings from 240 VAC to 600 VAC at 50/60 Hz. The max rated current is 85 A. Case diameters range from 63.5 to up to 116 mm. Custom capacitance and voltage ratings, sizes, and performance characteristics are also available. A variety of terminations are available.

The PCD capacitors can be used in high-humidity environments. The series has been tested at temperature-humidity bias for 1,000 hours at 85˚C/85% RH, which places them in the highest climatic category of Class III-B, per IEC 60384, said the company.

Applications include UPS, AC-tuned filters, AC input filtering, line conditioning, noise suppression, variable-speed drives, and wind-turbine monitoring. The PCD is an upgrade to European AC power film capacitors, said CDE, which usually have a downward expanding interruption mechanism. The PCD’s dual-pressure interrupter provides for maximum flexibility in mounting when fail-safe operation is of prime importance.

Another safety capacitor series is the SMDY1 from Vishay Intertechnology, Inc., which the company claims is the industry’s first SMD ceramic safety capacitors with a Y1 rating of 500 VAC and 1,500 VDC. The Vishay BCcomponents SMDY1 series of AC line rated ceramic disc safety capacitors are designed to withstand harsh, high-humidity environments. They can be used for EMI/RFI filtering in power supplies, solar inverters, smart meters, and LED drivers.

The closest competing devices offer capacitance up to 1.5 nF and Y1 ratings to 300 VAC, with no DC rating, said Vishay.

The SMD ceramic safety capacitors offer industry-high capacitance to 4.7 nF (470 pF to 4,700 pF) ±20% tolerance. They also offer higher humidity resistance with a Class IIB humidity grade (in accordance with IEC60384-14 annex I) and a moisture sensitivity level of 2a. The operating  temperature range is –55˚C to 125˚C.

Due to their surface-mount packaging, the capacitors offer a lower profile and eliminate the need for clearance space on the backside of the PCB. The devices are RoHS-compliant and halogen-free.

5G capacitors

Samsung Electro-Mechanics has developed a high-capacitance, high-voltage MLCC for 5G communication base stations. The MLCC in the 3225 case size (3.2 × 2.5 mm) offers a high capacitance of 10 µF and a high rated voltage of 100 V. It can replace two to three low-capacitance MLCCs, thereby reducing the mounting area of components.

The number of MLCCs used for each 5G base station is about 20,000, said the company, which is 4× that of 4G LTE, so the MLCC market demand for base stations is expected to grow rapidly.

MLCCs mounted on 5G communication base stations must be high-capacitance to minimize the component mounting area and to provide a stable power supply, said Samsung. In addition, high-voltage products are required due to the characteristics of base stations that use high operating voltages to reduce power loss, added the company.

The Samsung MLCC can operate reliably in harsh environmental changes such as in temperature and humidity, along with shock and vibration. The MLCC is said to offer an industry-best tensile strength with 3 mm guaranteed.

Targeting 5G smartphones is the low-profile and low-ESL AWK105 BJ474MN (4 V) and PWK105 C6474MN (2.5 V) MLCCs from Taiyo Yuden Co., Ltd. Measuring 0.52 × 1.0 × 0.1 mm, these MLCCs are suited for thin, space-constrained devices such as smartphones and wearables for decoupling the IC power supply lines inside these devices, which have become faster and more sophisticated for 5G services, said the company.

The devices provide a capacitance of 0.47 μF, which is about twice the capacity of its conventional capacitor (AWK105 BJ224MN) with the same dimensions and a capacitance of 0.22 μF. The low ESL was achieved thanks to improving its conventional thin-film technology and placing the external electrodes lengthwise, said the company.

New wide-bandgap power devices are also having an impact on capacitor designs. Knowles Precision Devices, a division of Knowles Corp., has extended its V-Series single-layer capacitor product line with a new 100-nF capacitor that can improve bypass performance in GaN and GaAs amplifier applications.

The high-frequency, wire-bondable 100-nF capacitor is suited for GaN and GaAs amplifier applications in which small size and microwave performance are critical, said the company. The single-layer capacitors support microwave and mmWave applications up to 100 GHz, targeting general DC blocking, low-noise amplifiers, power amplifiers and high-power amplifiers, oscillators, and filters.

The V-Series capacitors offer higher capacitance in a smaller footprint. The 100-nF device, housed in a 0408 case size, leverages Class II dielectric material with X7R characteristics for DC blocking and RF bypassing in a broad frequency range. They can be used in filtering, tuning, and coupling applications.

In addition to X7R temperature stability, the 100-nF capacitor is RoHS-compliant and offers the highest moisture sensitivity level (MSL-1). The capacitors offer high capacitance density and can be attached using conductive epoxy or be AuSn solder-mounted.

In RF-bypassing applications, the 100-nF capacitor can help eliminate supply-line noise. “Supply noise can mix with RF signals, impacting signal-to-noise ratios and potentially causing spurious output,” said Knowles, and “a bypass capacitor provides an efficient path to ground for RF energy on the supply line before it enters a gain.”