汽车PC开关应力开裂改善与表征

Characterization and Improvement of Stress Cracking of Automobile PC Switches

通过采用不同成分的溶剂浸泡试验以及气候循环试验,对汽车PC开关应力进行表征,追溯了导致现生产PC开关失效的应力来源,验证了不同退火工艺对改善PC开关应力的效果。结果表明丙酮和CCl4对PC开关的腐蚀性较强,且由于安全原因不适合作为PC开关应力表征的溶剂。乙酸由于诱导PC开关应力释放能力很弱,也不能作为表征PC开关应力大小的有效检测手段。乙酸乙酯与正丁醇(2:1)混合溶剂由于诱导PC开关应力释放能力适中,溶剂低毒而且较易获得,适宜作为PC开关应力的表征溶剂。气候循环交变对诱导开关类零件的应力释放效果甚微,不适合应力表征。另外,研究表明对装配前的开关分零件进行分别退火无法有效减小装配后的开关总应力,而对装配后的PC开关采用90℃,1 h的退火处理可以有效改善PC开关的应力开裂问题。

By solvent immersion test with different components and climatic cycle test,this paper characterizes stress of automobile PC switches,and traces the source of stress leading to the failure of PC switches and verifies the effect of different annealing processes to improve PC switch stress.The results show that acetone and CCl4 are highly corrosive to PC switches and not suitable for stress characterization due to safety reasons.Acetic acid cannot be used as an effective measure to characterize the stress of PC switches because of its weak ability to induce stress release.The easily available mixed solvent of ethyl acetate and n-butanol(2:1)is suitable for stress characterization of PC switches due to its moderate ability to induce stress release and low hypotoxicity.The climatic cycle alternate test is not suitable for the stress characterization due to its little effect on stress release.In addition,the research shows that the total stress of assembled switches can’t be effectively reduced by annealing its components separately before assembly,but with the annealing treatment for the assembled PC switches at 90℃for 1 hour,the stress cracking of assembled switches can be improved effectively.