在役晶体管湿热试验失效模式及机理研究

目的 研究在役晶体管湿热试验的失效模式及失效机理，为减少晶体管失效提出改进建议。方法 选取长期贮存了10余年未失效的3型在役晶体管进行湿热环境试验，采用扫描电镜观测、电性能参数测试、离子色谱分析等方法研究晶体管失效的模式和失效机理。结果 晶体管经过2 160 h湿热试验后，有 3.75%的晶体管发生失效，其中晶体管管腿断裂失效比例占2.50%，失效机理为应力腐蚀开裂；晶体管参数超标比例为1.25%，失效机理为器件背部或三防漆所含粘附离子引起的漏电。结论 湿热试验会加速在役晶体管的失效，其失效模式主要为因应力腐蚀开裂导致的管腿断裂以及因表面粘附离子引起的参数超差。建议在晶体管的寿命期内加强质量管理，改善不当的制管工艺，减少器件的内部缺陷及残余应力的存在，控制器件贮存环境的温湿度以及大气成分，杜绝氯离子等粘附离子及其他活性物质的引入。

Failure Mode and Mechanism of In-service Transistors in Damp Heat Test

The work aims to study the failure mode and failure mechanism of in-service transistors in damp heat test, and to propose improvement suggestions for reducing transistor failures. Three types of in-service transistors stored for more than 10 years without failure were selected for the damp heat test. The failure mode and failure mechanism of the transistors were studied by scanning electron microscope observation, electrical performance parameter testing, and ion chromatography analysis, etc. The results showed that 3.75% of transistors failed after 2 160 hours of damp heat test, including 2.50% of transistor lead breakage failure, and the failure mechanism was stress corrosion cracking; 1.25% of transistor parameters exceeded the standard. The failure mechanism was electric leakage caused by the adhesion ions contained in the back of the device or conformal coating. Damp heat test accelerates the failure of in-service transistors. The main failure modes are lead breakage due to stress corrosion cracking and parameter out-of-tolerance due to surface adhering ions. It is recommended to strengthen quality control during the lifetime of transistors, improve improper tube manufacturing process, reduce internal defects and residual stress, control the temperature, humidity and atmospheric composition of the storage environment, eliminate chloride ions and other adhering ions, and avoid the introduction of other reactive substances.