Evaluation of physical factors influencing solder-joint reliability of a 10mm leadless QFN package with top-side paddle

The standard QFN package consists of a leadless perimeter array and a bottom solderable thermal paddle. The thermal performance of the package can be improved by moving the paddle to the top-side. The soldered surface area of the package reduces by about 80% with a top-side paddle. The soldered-joint life will also reduce due to the significant thermal coefficient of expansion mismatch between the QFN package and the circuit board.;The solder-joint reliability of a large QFN package with top-side paddle is not well understood. This thesis evaluates the solder-joint reliability of a 10mm square leadless QFN package with top-side paddle. The analysis includes several classical models for a leadless package and compares modeling results to accelerated reliability testing. The accelerated tests include the influence mold compound and lead finish play on solder-joint life and ways to improve solder-joint reliability.