微波组件常见湿气失效现象和防护措施

Frequent Failures Caused by Humidity in Microwave Subassembly and Protective Measures

微波组件具有频率高、波长短和内部元器件密度高的特点。盒体材料一般使用铝合金,因此容易受到湿气的影响。常见湿气故障可以分为内部故障和外部故障,也可以分为永久性故障和暂时性故障。针对环境试验中遇到的几种微波组件常见的湿气问题,如盒体腐蚀、电路板腐蚀、输出功率下降以及低温升高温时自激振荡,进行了详细描述,给出了部分照片,并进行了深入的机理分析。最后从电路设计和工艺设计的不同方面给出了综合有效的7条微波组件湿气防护措施,这些措施包括元器件的选取、电路板的防护处理、接缝的防护处理和盒体的防护处理等。结果证明这些措施是行之有效的。

Microwave subassemblies have many characteristics such as high operating frequency, short wavelength and high density of elements and devices. The subassemblies are commonly made of alloy aluminum, therefore they are liable to influence of humidity. The frequent failures caused by humidity can be divided into different types： the interior and the exterior, or the perpetuity and the temporariness. Several moist problems frequently appearing in environment tests of microwave subassemblies were particularly described, such as the case erosion, PCB erosion, output power decline and self-oscillation from the low temperature to the high temperature. Simultaneously an in-depth analysis of their mechanism was performed. A portion of corresponding photos were given. Finally, 7 colligated available moisture proof measures from different aspects were presented, such as the circuit design and the process design. These measures include the choice of elements and devices, the protective treatment of PCB, the protective treatment of contact seams and the protective treatment of cases, etc. The above-mentioned protective measures were proved effective by experimental results.