摘要
电表在加速寿命试验(ALT)中,由于其内部轻触开关接触不良,导致电表功能失效。通过电阻测试、扫描电子显微镜、聚焦离子束等手段研究轻触开关在ALT环境中的失效行为及机理。结果表明:开关失效部位为锅仔接触面,原因为锅仔接触面的镀Ag层存在凹坑,且凹坑处的Ag镀层太薄,在ALT环境中无法有效保护Cu基体,导致基体发生腐蚀。由于腐蚀产物的导电性差,使得开关因接触不良而失效。其机理为ALT环境中,凹坑处Ag镀层本身氧化以及Ag层表面微电池的形成两方面的协同作用,加速凹坑处Ag层与基体的腐蚀破坏。可通过控制锅仔铜基体的粗糙度和增加锅仔镀银层厚度来改善锅仔在ALT环境中的腐蚀失效问题。
The ammeter was functional failed due to the poor contact of the switch used in ammeter during accelerated life test(ALT).The failure behavior and mechanism of switch in ALT environment were studied by resistance test,scanning electron microscope equipped with energy dispersive spectroscopy and focus ion beam.The results indicate that the failure site of switch is in contact surface of contact.This because the Ag plating is too thin in pits in contact surface to protect the Cu substrate,and the corrosion product of Cu substrate is high resistance,which leads to the poor contact between terminal and contact.The failure mechanism is that both the oxidation of Ag plating itself in pits and the formation of many galvanic cells on the Ag plating in ALT environment could accelerated the corrosion of Ag plating and Cu matrix especially in pits.To prevent the failure of contact in ALT,it should decrease the roughness of Cu substrate of contact and increase the Ag thickness on contact.
作者
赵晨
郑旭彬
郑佳华
刘路
ZHAO Chen;ZHENG Xu-bin;ZHENG Jia-hua;LIU Lu(Dongguan Kaifa Technology Co.,Ltd.,Guangdong Dongguan 523905,China;Shenzhen Kaifa Technology Co.,Ltd.,Guangdong Shenzhen 518035,China)
出处
《失效分析与预防》
2023年第3期201-206,共6页
Failure Analysis and Prevention
