Correction of Nonuniform Attenuation of Voltage-Controlled Attenuator Under Harsh Environment by Process Improvement

This paper describes the assembly process improvement of die attachment technique of an open-loop multistep voltage-controlled attenuator (VCA) in detail. The VCA is made up of p-i-n diodes (dies). Die p-i-n diodes suffer from attachment issues done by single or binary epoxy followed by controlled temperature treatment. It results in improper ground impedance at microwave and millimeter-wave applications. A thorough analysis is carried out on these epoxy attachment issues. A suitable technique for the attachment of dies on the metallic standoff is adopted to overcome these issues for the mass production scenario. Multiple modules have been made and tested over extensive thermal cycling from -30 °C to +70 °C, and random vibrations in three axes to establish the analysis.