Space-saving capacitors and resistors

Board space is always at a premium, especially when it comes to passive components. However, designers in high-reliability markets are looking for more than just tiny devices; they also need capacitors and resistors that can handle higher operating temperatures and harsh environmental conditions. These include applications in automotive, avionics, industrial and telecommunications.

In many cases, passive component manufacturers are doing more than just shrinking the package size. They are packing more performance in these tiny devices while providing higher reliability. In many cases, higher performance enables designers to shrink their bill of materials.

For capacitors, this means higher capacitance/voltage (C/V) ratings in the same or smaller package sizes as well as lowering the equivalent series resistance (ESR) and equivalent series inductance (ESL). For resistors, this often translates into technological improvements to simplify design and higher power ratings in smaller packages, resulting in fewer components in the design and lower costs.

Here is a selection of capacitors and resistors introduced in 2023 that meet the growing demand for smaller packaging and higher performance in high-reliability markets.

Smaller and higher-performance capacitors

Murata Manufacturing Co. Ltd. recently introduced the LLC series, claiming the smallest and thinnest 1-µF LW reversed multilayer ceramic capacitor (MLCC) for automotive applications. The automotive-grade MLCCs tout the industry’s first 0.18-mm profile package and feature a reversed termination for low ESL.

In addition, the 1-µF capacitance in a 0.5 × 1.0-mm footprint makes the parts the smallest in the market, Murata said.

The company attributes the smaller size to Murata’s proprietary thin-layer forming and high-precision lamination technology, in combination with advanced material atomization and homogenization techniques. The result is about a 20% reduction in component height compared with existing parts.

Murata said the smaller size allows the capacitors to fit more easily on the backside of circuit boards. It also allows the parts to be placed in optimum positions for decoupling of processor power rails, close to the die. This reduces the number of capacitors required, thus saving cost and increasing system reliability, the company said.

The MLCC series features low ESR and a reduction in ESL, which is reported to reduce the high-frequency impedance of the capacitors. “This improves circuit performance to meet the requirements of modern, low-voltage, compute-intensive applications, such as automotive advanced driver-assistance systems,” Murata said.

The LLC series complies with AEC-Q200 requirements. The operating temperature range is –55°C to 125°C.

Even the traditionally larger aluminum electrolytic capacitors are available in smaller case sizes without compromising capacitance density. This includes delivering higher C/V in the same or smaller package sizes.

Aimed at automotive applications, Vishay Intertechnology Inc.’s new series of low-impedance automotive-grade miniature aluminum electrolytic capacitors deliver higher performance in smaller case sizes than previous-generation solutions. The Vishay BCcomponents 172 RLX series features high ripple currents up to 4.9 A, high-temperature operation to 105°C and a useful life of up to 10,000 hours. They are available in 14 case sizes, ranging from 10 × 12 mm to 18 × 40 mm.

The AEC-Q200–qualified capacitors offer lower impedance and higher capacitance for a given case size and voltage, as well as up to 54% higher ripple current at the same C/V rating in smaller case sizes, compared with previous solutions. The benefits for designers translate into fewer components needed, increased design flexibility and board space savings.

Key specifications include rated voltages up to 50 V, a capacitance value range from 150 µF to 15,000 µF and low impedance down to 0.011 Ω at 20°C. The devices are charge- and discharge-proof and feature radial leads and a cylindrical aluminum case with pressure relief, insulated with a blue sleeve.

The polarized aluminum electrolytic capacitors with a non-solid electrolyte are suited for smoothing, filtering and buffering in switch-mode power supplies, DC/DC converters, motor drives and control units for industrial, automotive, telecommunications, audio-video and electronic data-processing applications. The devices are RoHS-compliant.

A new series of low-profile aluminum electrolytic capacitors from Cornell Dubilier Electronics Inc. (CDE) saves space and offers more options. The flatpack MLPS capacitors offer high capacitance density in a flat configuration, with voltage ratings up to 450 VDC. They are rated for 10,000 hours at 105°C.

One or two MLPS capacitors can replace large banks of surface-mount aluminum electrolytics or axial wet tantalum capacitors, which reduces space, cost and weight, CDE said.

The capacitors offer a capacitance range from 120 µF to 51,000 µF and voltage ratings from 7.5 VDC to 450 VDC. The operating temperature is –55°C to 105°C.

The Flatpack capacitors are used in commercial and military aircraft, as well as ground-based and shipboard radar. Although most applications use either 85°C or 125°C rated components, CDE said it developed the new 105°C devices to provide greater design flexibility, higher performance and lower cost in power supply designs.

“The use of higher-temperature components than needed adds cost and size, making them less efficient,” CDE said.

These aluminum electrolytic capacitors are available in four sizes. All devices have a thickness (height profile above the board) of 0.6 inches and a width of 1.8 inches. Case lengths range from 1.5 to 3.0 inches. The larger case sizes are typically rated for several amps (RMS), CDE said.

“Ripple current ratings can be significantly enhanced by adding one or more heat sinks to their flat sides,” the company said.

Unlike conventional electrolytics that have a rolled cover, the MLPS covers are laser-welded, which are reported to provide near-hermetic seals that resist electrolyte dry-out. They can be used at high altitudes of up to 80,000 feet and exhibit excellent capacitance retention at low temperatures, according to CDE. The MLPS capacitors offer a variety of lead types and mounting options.

TDK Corp. has added the EPCOS B43657 series with snap-in terminals to its EPCOS aluminum electrolytic capacitor family. These snap-in capacitors with case sizes from 22 × 25 mm to 35 × 60 mm claim extremely high capacitance density. They provide 20% higher capacitance compared with their predecessor.

A key feature of the B43657 series is its high-ripple–current capability of up to 8.54 A (120 Hz, 60°C), TDK said. Accurate lifetime calculation under application-specific conditions is available via TDK’s online AlCap Tool.

Key specifications include capacitance values from 120 µF to 1,250 μF, rated voltages from 450 VDC to 475 VDC and a service life of at least 2,000 hours at a maximum operating temperature of 105°C. Other features include a capacitance tolerance of ±20% and an operating temperature range of –40°C to 105°C.

The high-C/V capacitors are housed in an aluminum case with an insulated PET sleeve without an insulation sheet at the bottom of the can. Thanks to their high reliability, the RoHS-compatible capacitors can be used in high-end switch-mode power supplies and power supplies for industrial and telecommunications applications. Other applications include UPS systems, photovoltaic inverters and frequency converters.

More options for resistors

Vishay Intertechnology Inc. has developed a couple of space-saving power resistors this year. The first one is the Vishay MCB ISOA power resistor with an optional NTC thermistor and pre-applied thermal interface material (PC-TIM), which saves space and reduces cost.

Designed for mounting on a heat sink, the AEC-Q200–qualified thick-film power resistor is housed in a low-profile SOT-227 package. The optional NTC thermistor for internal temperature monitoring simplifies design and saves board space, while the pre-applied PC-TIM delivers more efficient mounting and streamlined installation. The power resistor also features high pulse-handling capability and high power dissipation up to 120 W at an 85°C bottom-case temperature.

Key specifications include a resistance range from 0.47 Ω to 1 MΩ, with tolerances of ±5% and ±10%; TCRs of ±100 ppm/K, ±150 ppm/K and ± 300 ppm/K; a maximum operating voltage of 1,500 V; and dielectric strength of 4,000 Vrms. The operating temperature range is –55°C to 150°C.

The RoHS-compliant device features a non-inductive design and can include two resistors, the company said.

The high power and high energy dissipation of the resistors also help simplify designs and lower costs by reducing the need for power components. For applications subject to high and repetitive pulse surges, the resistor can handle high energy pulses (i.e., 110 J for 0.1 seconds) and is multi-pulsed tested at 230 J for 670 ms and 3,000 cycles and 350 J for 1,060 ms and 5,000 cycles. Custom testing options are available.

The resistor is built on an exposed alumina substrate instead of a metal tab and is used as a pre-charge, discharge, active discharge or snubber resistor. Applications include automotive and industrial as well as avionics, military and space (AMS) applications.

Another space and cost saver is the improved Vishay Draloric RCS0805 e3 anti-surge thick-film power resistor in the 0805 case size with a higher power rating of 0.5 W. Applications include automotive, industrial, telecommunications and medical.

This AEC-Q200–qualified device lowers component count and placement costs. Case in point: With its increased power rating, the RCS0805 e3 can now be used in place of four standard parallel resistors in the 0805 case size, two parallel devices in the larger 1206 or one resistor in the 1210 case size, Vishay said.

The resistor also offers “superior” pulse-load performance and electrostatic-discharge surge characteristics when compared with standard chip resistors for applications that are subject to high and repetitive surge pulses, according to Vishay.

Key features include a resistance range from 1 Ω to 10 MΩ—and 0-Ω jumper—with tolerances of ±0.5%, ±1% and ±5% and TCRs of ±100 ppm/K and ±200 ppm/K. The resistor offers an operating voltage of 150 V and an operating temperature range of –55°C to 155°C. The power resistors are RoHS-compliant and halogen-free.

Packing more power in a smaller package size, KOA Speer Electronics recently introduced the UR73VH2B current-sense resistor for automotive applications. The AEC-Q200 resistor offers a higher power rating of 1 W in a smaller 1206 package size and extends the resistance range for the UR73VHB resistors.

Key specifications include a resistance range of 100 mΩ to 1 Ω, a TCR of ±100ppm/°C and a standard tolerance of ±1%. The resistor also offers a wide operating temperature range of –55°C to 155°C, with a rated terminal temperature of 125°C.

Delivering low resistance, high accuracy, high reliability and current detection, the UR73VH2B resistors are suited for automotive, industrial, telecommunication and consumer electronics markets in a range of applications, including electronic control units, small motors, displays, monitors, DC-to-DC conversion and AC adaptors, power supplies, notebook PCs, cellphones and motor circuits.

Stackpole Electronics Inc. has expanded its RNCP series of anti-sulfur chip resistors with miniature packages, now offering 1210, 2010 and 2512 sizes. These thin-film, precision chip resistors can be used in applications like automotive, industrial and lighting that require anti-sulfur performance, replacing many thick-film resistors that aren’t suitable for this application.

The RNCP chip resistor series features high precision with tolerances down to 0.1% and TCR as low as 10 ppm, as well as anti-sulfur capability with shifts of less than 2% under industry-standard EIA-977 testing, according to the company.

Unlike thick-film resistors, the RNCP series does not require a lead-containing dielectric glass, providing an RoHS-compliant solution without exemptions, Stackpole said.