Corrosion failure analysis of hearing aid battery-spring contacts. (September 2017)

• Record Type: Journal Article
• Authors: Gudla, Visweswara Chakravarthy; Ambat, Rajan
• Is Part Of: Engineering failure analysis. Volume 79(2017)
• Page Start: 980
• Page End: 987
• Publication Date: 2017-09
• Subjects: Chloride -- Coating failures -- Corrosion -- Environmental interaction -- Failure analysis; System failures (Engineering) -- Periodicals; Fracture mechanics -- Periodicals; Reliability (Engineering) -- Periodicals; Pannes -- Périodiques; Rupture, Mécanique de la -- Périodiques; Fiabilité -- Périodiques; Fracture mechanics; Reliability (Engineering); System failures (Engineering); Periodicals; Electronic journals; 620.112
• DOI: 10.1016/j.engfailanal.2017.05.045
• Languages: English
• ISSNs: 1350-6307

Abstract

Abstract: Reliability of low power electrical contacts such as those in hearing aid battery-spring systems is a very critical aspect for the overall performance of the device. These systems are exposed to certain harsh environments like high humidity and elevated temperatures, and often in combination with high levels of salt from human perspiration and environmental pollutants. In addition, the design aspects of such systems often call for multi-material combinations of substrate and coatings for catering to various requirements such as electrical conductivity and wear resistance, which in turn enhance the susceptibility of these systems to galvanic corrosion. In this study, traditional behind-the-ear (BTE) hearing aid systems, which failed during service were analysed. Failure analysis was performed on the dome type battery-spring contact systems. The morphology of the contact areas was observed using scanning electron microscopy, and the compositional analysis of the corrosion products and contaminants was performed using energy dispersive X-ray spectroscopy. Wear track morphology was observed on the contact points, and the top coating on the dome was worn out exposing the substrate spring material. The obtained results were correlated to the underlying corrosion mechanism and the failure mode is presented. Highlights: Corrosion and wear was observed on failed hearing aid battery spring contacts. Contacts were observed to have an electroplated Au layer on a Ni underlayer. Corrosion products contained oxides and chlorides of Ni and Fe. Delamination of Au layer and wear of underlying Ni based substrate occurred. Human perspiration, dust, organic contamination and faulty batteries caused failure.