Microchip Technology Incorporated
Surface-mount integrated circuit package with coated surfaces for improved solder connection

Abstract:

Methods are disclosed for forming flat no-leads packages (e.g., QFN packages) with soldering surfaces that are fully coated, e.g., by a tin immersion process, for improved solder connections of the packages to a PCB or other structure. The method includes forming a flat no-leads package structure including a leadframe terminal structure having an exposed top or bottom surface; forming a first coating of a first coating material (e.g., tin) on the exposed top or bottom surface; cutting through a full thickness of the leadframe terminal structure to define an exposed terminal sidewall surface; and forming a second coating of a second coating material (e.g., tin) over the full height of the exposed terminal sidewall surface. The coating (e.g., tin immersion coating) covering the full height of the leadframe terminal sidewall may enhance the flow of solder material, e.g., when soldering to a PCB, to provide an improved solder connection.