No Sulfur Corrosion Here: Sulfur Resistant Film Resistors

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There are plenty of hostile environments that test the reliability of electronic components. Temperature extremes, dust, humidity, and altitude are just a few conditions that designers have persevered against with rugged designs. Toxic chemicals and gases present some of the worst threats and are common conditions in many industries. In particular, high sulfur environments play havoc with everything from IT industry server farms and data/storage centers and telecommunication base stations to industrial control equipment and rubber, paper and oil manufacturing plants. For instance, sulfurous environments have a particularly negative impact on film resistors. Sulfur, when it reacts with elements such as silver, produces sulfide growth that can cause resistors to go open circuit.

In standard film resistors, their internal silver (Ag) or silver palladium (AgPd) terminal is only protected by the epoxy passivation layer making the device very susceptible to sulfur-based gases. These gases can attack the silver in the terminal starting the corrosion process based on surrounding conditions such as temperature, humidity, and even air flow.

Realizing how sulfur gases can affect the reliability of its film resistors, Bourns developed a specialized Palladium (Pd) layer that removes the chance for corrosion and the formation of silver sulfide. By adding the protective Palladium material over the termination and production layer of its chip resistors, it dramatically slows down the amount of sulfur penetration that can reach the internal silver layer areas of the resistor. Palladium is a highly-resistant material against sulfurous gases that also helps inhibit the growth of silver sulfide. Tests that Bourns engineers have performed demonstrate that its sulfur-resistant devices offer 20 times greater operating life compared to its standard film resistors.

There are other solutions such as adding a gold layer or eliminating the use of silver in terminations, which can be more effective solutions to prevent sulfur corrosion damage. The downside of these approaches is they are much costlier compared to Palladium. We have found that most customers are very happy with our cost-effective Palladium solution that gives them enough protection for their applications.

With the use of Bourns® sulfur-resistant film resistors, this corrosion-related type of hard failure can be greatly reduced, resulting in improved system reliability, performance, robustness, and reduction of downtime. This is one of the most important operating factors in the IT industry where subsystems such as memory modules are used heavily in server farms and the data/storage center marketplace. If your application needs to ensure critical data transfers even in unfavorable sulfurous environments, Bourns wants to help.