Lead Frame Recess Layout for Crack-Resistant QFN Solder Joints

The patent applies local quality by creating recessed portions at specific locations on the lower surface of the lead and die paddle, rather than making the entire surface non-flat. These localized recesses provide mechanical interlocking for solder connections while maintaining a largely flat surface for compact packaging. The recessed portions are strategically positioned to enhance solder joint stability without significantly increasing the overall package footprint area.

The patent applies segmentation by dividing the continuous lower surface of the lead and die paddle into multiple recessed portions. Instead of creating a single complex non-planar surface, the design segments the surface into several smaller recesses distributed across the bonding area. This segmentation simplifies the manufacturing process compared to creating one large complex feature, while still providing adequate mechanical interlocking for solder connections.

The patent applies partial action by creating recessed portions that are sufficient to block shear stress transmission but not excessive in size or number. The recesses are designed with optimal dimensions and spacing to provide the necessary mechanical interlocking for preventing cracks during reliability tests, while maintaining adequate remaining bonding area for solder connections. The design avoids over-engineering the recess features, balancing shear stress blocking capability with bonding area requirements.