Sulfur contamination in chip resistors was primarily an issue for the automotive industry, but over the past several years it has migrated into other applications. Sulfur contamination can impact the long-term reliability of resistors in high-sulfur content environments. While there aren’t a huge number of applications in high-sulfur environments, in some industrial locations, such as some areas of China, the air contains enough sulfur to cause failures in electronic devices, according to Stackpole Electronics.
Once an OEM purchaser puts a policy in place to buy only anti-sulfur resistors that gets pushed down to their supply base. It not only impacts the resistors they buy but also other electronics components that contain resistors such as power supplies and memory modules.
Stackpole’s new RNCS-AS thin-film precision chip resistors are resistant to both sulfur and moisture. Although thin-film nichrome resistors typically have difficulty withstanding high humidity environments under low power, Stackpole uses proprietary materials and processing to protect the nichrome element, enabling the devices to perform as well - under high humidity testing - as more expensive technologies such as tantalum nitride film chips, according to the company.
Stackpole also has minimized the effects of sulfur on the printed palladium silver inner terminations, which are susceptible to contamination by sulfur causing resistors to open, through its unique termination material and design. The AEC-Q200 qualified precision chip resistors are suited for applications such as outdoor controls, security and surveillance, instrumentation, and test equipment.
The resistor maker also offers convex termination anti-sulfur chip resistor arrays. The RAVS Series can be used in a range of applications including automotive controls, industrial and commercial machinery controls, marine equipment, electric motor and pump controls, HVAC controls, LED lighting fixtures, fire and safety systems, remote communications equipment, and power supplies for industrial or harsh environments.
Similarly, Vishay Intertechnology offers a new series of sulfur-resistant thick-film resistors in seven small cases sizes. The Vishay Draloric RCA-IF e3 series delivers pulse-proof performance and advanced sulfur resistance for automotive, industrial, and medical applications. The resistors are available in seven case sizes ranging from 0402 to 2512 with power ratings from 0.063 W to 1.0 W.
For high-sulfur environments, the devices offer a sulfur withstand ability in accordance to ASTM B809 95, tested at 90 °C for 1,000 hours, together with excellent anti-surge and pulse characteristics, said Vishay. “The resistors are optimized for applications such as input circuits or MOSFET gate resistors susceptible to pulse loads while operating in a polluted atmosphere.”
Other environmental compliance for the lead (Pb)-free devices (with pure tin plating) include the RoHS directive 2011/65/EU and halogen-free according to the JEDEC JS709A definition.