Design characterization of microwave antenna BGA interconnect structure using test-validated physics-of-failure methods

A prototype two-component solder BGA interconnect structure was evaluated for attachment of microwave electronics to a phased array antenna element. The assembly comprised a dual circular polarization receiver module (DPR) for a direct broadcast satellite television (DBS) phased array antenna for mobile platforms. A fatigue life study was conducted to characterize the thermo-mechanical performance of a 42 I/O solder ball interconnect between a high temperature co-fired ceramic chip carrier and a plastic encapsulated metallic antenna probe. The BGA structure consisted of high temperature 90Pb10Sn solder balls with 63Sn37Pb attachment solder fillets. Alternative design configurations and material selections were evaluated for durability using concurrent design/analysis for rapid product development cycle times. A plastic-strain damage model based on a modified Coffin-Manson fatigue criterion was selected to represent the dominant BGA interconnect failure mechanism of low-cycle solder fatigue. Plastic-strain range characterization was completed using a nonlinear finite element code, Nike3d. Durability life was improved from 10s of thermal cycles to thousands with corresponding plastic-strain reductions at critical interconnects. The primary design change involved encapsulant CTE reduction. However, this change was not implemented in production due to inadequate dielectric loss performance with the replacement encapsulants. By using concurrent design/analysis, life-cycle durability characterization of a complex interconnect system was accomplished in a cost-efficient manner without time consuming experimental iterations.