Hybrid moisture problems

This paper will present the analysis and results of a project to determine why a group of RF hybrid microcircuit amplifiers failed with internal water vapor between 14.5 kppm and 93 kppm. Details of 85°C/85% humidity, active temperature cycling and shock tests, life testing, dew point testing, infrared microscanning, vibration tests and field failure analysis will be presented. Specific analysis of multilayer chip capacitor cross sectioning, testing in <5 kppm internal H₂O environment and 85°C/85% humidity with known good and known bad capacitors, methanol test, delamination and crack formation, tunneling voids, metal migration under DC bias and moisture, Scanning Laser Acoustic Microscopy (SLAM) test, thermal stress of solder fillets on endcaps of barium titanite capacitors using ANSYS^(R) , and DC bias voltage effects on metal migration shorts will be presented. The physics of failure in this case and hybrid assembly lessons learned will be of interest to both hybrid and multilayer chip capacitor users and manufacturers