Top ten harsh environment resistors

Fixed resistor manufacturers face continued demand for extended operating temperature ranges and AEC-Q200 qualified parts for automotive and industrial applications that need high stability in harsh environments. At the same time, a continuing trend towards miniaturization poses an additional challenge as manufacturers try to pack more performance in smaller package sizes.

Also, over the past several years, there has been a greater need for anti-sulfur resistors. Sulfur contamination was primarily an issue for the automotive industry but it has become a more widespread challenge in other application areas. Sulfur contamination impacts the reliability of resistors in high-sulfur content environments, which can cause product failures.

Here are 10 resistor lines introduced this year that deliver high reliability, high stability, or high-temperature performance for a range of applications that require more robust performance.

Model CRxxxxA-AS devices can be used in a range of applications, from general purpose to industrial (industrial motor controls, pump controls, and welding equipment) and outdoor and on-road applications (lighting and traffic control).

The AEC-Q200 compliant resistors are available in eight different footprints from 0201 (0603 metric) to 2512 (6432 metric) case sizes with rated power from 0.05 W to 1 W. The resistance values range from 1 ohm to 20 Mohms. The expanded line of resistors are RoHS compliant and halogen free. The operating temperature range is -55°C to 125/155°C.

The resistors deliver improved electrolytic corrosion resistance and high stability compared to KOA’s existing RN73 thin-film resistors. The RN73R offers excellent heat tolerance with an operating temperature range of -55°C to 155°C and a rated ambient temperature of 85°C, as well as improved moisture tolerance of 85% for 1,000 hours at 85°C.

The RN73R resistors are offer power ratings (per case size) of 0.063 W (0402), 0.1 W (0603), 0.125 W (0805), and 0.25 W (1206) with a resistance range of 10 to 1.5 Mohms, resistance tolerances ranging from ±0.05% to ±1% and temperature coefficient of resistance (TCR) values of ±5, ±10, ±25, ±50, and ±100 ppm/°C. The resistors are RoHS compliant.

The company attributes the resistors’ high level of performance to the use of ceramic cores instead of fiberglass. Ceramic offers higher efficiency by handling heat more effectively during overload and current surge events.

The resistors are available in flat (BR) or tall (BRT) series versions with quick-connect terminations. They offer a resistance range from 0.1 ohm to 1 kohm with tolerances of 1%, 5%, and 10%; a withstand voltage of 2,500 VAC, and good long-term stability with a TCR of less than ±260 ppm maximum. The operating temperature range is –55°C to +200°C.

An ultra-slim version, the BRS series, also is available. Offering a 12-mm profile, the series offers power ratings from 100 W to 500 W and a resistance range from 1 ohm to 5 kohms.

The RTAN series are designed with anti-sulfur materials and passes the ANSI/EIA-977 (method A) standard sulfur test. The series also is AEC-Q200 compliant. It’s available in popular resistance values with 0.1% tolerance and 25-ppm TCR in 0805 and 1206 packages from stock. See the datasheet for the full range of case sizes, resistance values, TCR, voltage, and power ratings.

Applications include instrumentation, aerospace, test equipment, industrial controls, portable communications diagnostic equipment, and portable medical devices.

A proprietary direct film deposition process enables the HVAM to achieve tolerances down to 0.1% and TCRs as low as ±50 ppm, while providing high-voltage ratings. These devices can be used in a variety of medical applications, circuit protection, voltage dividers, welding and plasma cutting equipment, and high-voltage power supplies.

These anti-sulfur resistors provide better surge voltage and pulse power for enhanced surge protection in small, surface-mount designs. This also translates into enhanced reliability and reduces field failures in applications exposed to electrical surges like connected health and Industry 4.0 applications. They can withstand up to 6.5 kV peak for a 1.2/50 µs surge and up to 6 kW for a 0.1 ms pulse. The operating temperature range is -55°C to 155°C.

The HDSC resistors are available in four sizes from 0805 to 2512 and can be used to replace large chip or multiple chip solutions. The small footprint for given ratings saves printed-circuit-board (PCB) area for applications that call for a compact design.

The WFM resistors offer 2-W and 3-W power ratings in 2010 and 2512 case sizes. The resistors feature a solid metal manganese-copper or nickel-chromium alloy resistive element with a low TCR of < 20 ppm/°C, low inductance values of 0.5 nH to 5 nH, and low thermal EMF to < 3 µV/°C. The operating temperature range is -65°C to 170°C. The devices are RoHS-compliant, halogen-free, and Vishay Green.

The WFM devices incorporate an improved thermal management design using a copper heat spreader that allows the resistors to maintain its electrical characteristics of the Power Metal Plate construction. Vishay also uses a proprietary processing technique that enables a wide range of low resistance values from 5 mohms to 500 mohms, with tolerances down to ± 1.0%.

The devices are suited for a wide range of current sensing and pulse applications. These include automotive electronic controls, brushless DC motor controls, and battery management for electric and hybrid vehicles. They also can be used in high power inverter/converter controls and large motor drives for industrial applications; power supplies for downhole instrumentation; inverter control for consumer appliances and HVAC systems; and power management, conversion, and safety in servers and other computing applications.

The Vishay Dale Power Metal Strip resistors, offered in an 8518 case size and an all-welded construction, offer very low resistance down to 100 microohms thanks to a proprietary technique and power ratings up to 36 W. The resistors feature a proprietary processing technique that produces their extremely low resistance values, which allow for high current capabilities.

The WSBS8518…34 and WSBS8518…35 offer low inductance values of <5 nH, low thermal EMF down to <1.25 μV/°C, and an operating temperature range of -65°C to +170°C. The resistors are RoHS-compliant, halogen-free, and Vishay Green.

Source: Electronic Products article
By Gina Roos, Electronic Products select 10 top resistors designed for harsh environments, including automotive and industrial applications.