Anti-sulfurated Chip Resistors That Have Achieved High Reliability by Adopting Gold-based Electrodes and High Palladium-Silver Alloy Electrodes
Through our technical information, we introduced current sensing chip resistors and high precision chip resistors as high-performance resistors. In this issue, we will present anti-sulfurated chip resistors, which provide high reliability even under harsh environmental conditions.
What Are Anti-sulfurated Chip Resistors?
Anti-sulfurated chip resistors, as their name suggests, are chip resistors with enhanced anti-sulfurated performance. Sulfuration usually refers to the phenomenon of combining with sulfur components contained in the air such as hydrogen sulfide. In chip resistors, sulfur components may enter from a gap between the protective coating and the electrode and sulfurate the silver (Ag) of the electrode materials into silver sulfide (Ag2S), causing disconnection. An example is shown below.
It is therefore necessary to use chip resistors with applied anti-sulfurated measures in environments with a high sulfur content. Anti-sulfurated measures include the adoption of a structure that does not easily allow the penetration of sulfur into the internal electrode section and the use of a sulfuration-resistant metal for electrodes.
Applications of Anti-sulfurated Resistors
Anti-sulfurated resistors are used to maintain/improve reliability in environments with a high sulfur content. Locations with a high sulfur content include areas near volcanoes or hot spring resorts, along trunk roads with a high level of automobile exhaust gas emission, and near places where cutting oil or rubber products are used. Some materials used in general environments may also contain sulfur components. For example, cooling fan filters, packing or vibration-isolating rubber products and mold resins, etc., require attention. Some silicon-based coating materials, etc., promote sulfuration.
Applications include equipment and facilities that are often exposed to the external environments or used in environments with a high sulfur content, such as, machine tools, industrial machines, computer servers, base stations, lighting, security, industrial motors, control equipment, and automobiles.
Features of Panasonic Anti-sulfurated Chip Resistors
Panasonic anti-sulfurated chip resistors have achieved high reliability by changing the top electrode material from silver to one with high sulfuration-resistance. Taking the balance of performance and costs into consideration, the company also offers two product series: one that pursues "absolute performance" and the other with enhanced "life-extending effects."
1) Gold-based electrodes pursue absolute performance
ERJS type products use a gold-based material for their top electrode. It is well known that gold-based materials are stable in the presence of sulfur and are highly resistant to sulfuration.
2) High palladium electrodes with enhanced life-extending effects
ERJU type products use a silver-palladium alloy for their top electrode to improve the resistance to sulfuration. Alloying silver with palladium suppresses the diffusion of silver, thereby increasing resistance to sulfuration. Furthermore, the products use a high palladium-silver alloy with an increased palladium content ratio that achieves even higher resistance to sulfuration.
An immersion test for the electrodes of these anti-sulfurated chip resistors and standard type items was conducted with oil that contains sulfur components. The test results are shown below.
Although the electrodes of standard type items also contain palladium (Pd), the content ratio is low, and open failures occurred after around 100 hours. Conversely, no disconnection (open circuit) occurred with ERJU type products with high palladium-silver alloy electrodes even after 3,000 hours, clearly indicating their improved reliability. There's a correlation between the palladium content ratio and the time until disconnection, and design values that do not allow disconnection even after 12,000 hours in this test are adopted for ERJU type products. ERJS type products, which have adopted gold-based electrodes, indicate no change in resistance even after 3,000 hours, demonstrating very high reliability.