Design Selection and Optimization of Mechanical Anchoring Structure on Pre-plated Cu Leadframes

The study aims to select the ringframe anchoring design that would provide sufficient glue adhesion strength that could pass reliability tests without detached ringframe. The selected design was optimized using the measured ringframe glue loop volume in response of cross-sectional flowout, bondline thickness of glue between ringframe and flange, and occurrence of voids. Optimized anchoring dimensions were used as basis for the fabrication of stamping tool to produce final leadframe samples with ringframe anchoring. Each samples was subjected to Gross Leak Test (GLT) and Ringframe Shear Test (RST) at varying test temperatures at zero-hour and after every reliability readpoint. Results showed that only dovetail groove design could meet the $\geq 25$ and 0.5 kgF at 120°C and 260°C test temperatures and was selected as the anchoring design for optimization. The dovetail dimensions with smallest groove volume and cross-sectional area exhibited flowout, glue bondline thickness, glue coverage and voids within criteria. Final stamped leadframe samples with optimized dovetail groove dimensions showed higher adhesion strength than standard flanges at UHAST 96H and TMCL 1500 cycles without detached ringframe. Lastly, the shear force of dovetail with and without surface roughening have no significant difference implying that surface roughening can be removed for cost reduction.