Low-cost flip-chip process for monolithic microwave integrated circuits and optical components

Flip-chip solder bonding is a method for simultaneously achieving attachment and interconnection between electronic components and substrates. It is particularly attractive for microwave and optical active devices. However, a major stumbling block to demonstrating flip-chip technology for any new or low-volume application is the requirement for whole semiconductor wafers in order to apply solder bumps to the die bond pads. This makes design iteration and technology demonstration extremely expensive. This paper describes a flip-chip soldering process suitable for commercial GaAs monolithic microwave integrated circuits (MMICs), where the MMICs are available only as individual dice with conventional gold wire bond pads. The electrical performance of active test circuits manufactured using this method is presented, and confirms the superiority of flip-chip soldering for attachment and interconnection of microwave devices.