A Comprehensive Way to Use Bonding to Improve RF Performance of Low Noise Amplifiers

Is RF engineering a form of black magic? This article analyzes the challenges faced in the development of ADH519S, an 18 GHz to 31 GHz low noise amplifier (LNA), for the aerospace market. The die used in the product development for space was originally released to the commercial industry in the LC4 package. To release this product for the space and high reliability market, and comply with MIL-PRF-38535 standards, this part was assembled using the most suitable and available hermetically sealed ceramic package. This article presents a unique solution and process education to improve RF performance via bonding.

This product development process presented the following challenges:

• The most suitable and available space qualified hermetically sealed ceramic package had a large cavity in relation to the die in the originally released package. The larger cavity drove the need to double the length of bond wires, which, when combined with the parasitics of the new package, had the potential to cause device instability.
• Even if instability did not occur, the parasitics of the long bond wires could degrade the S-parameters.

This article reviews the different methods used to overcome these challenges and how to achieve the best stability and noise figure performance from the new hermetically sealed ceramic package.