Understanding the Impact of Spindle Rotation Direction in the Full Cut Singulation Process of Wettable Flank QFN Packages

Full cut singulation is one of the critical steps in the end of line back end integrated circuit (IC) package assembly. It is a process where in IC packages in lead frame strip form are separated into individual units. Important singulation process parameters must be maintained at best setting to attain dimensionally precise and defect-free packages. Therefore, the aim of this work is to determine the effect of spindle rotation direction, a process factor of great importance, in the full cut singulation process of wettable flank QFN package. Sample lead frame strips were processed in a singulation machine with front and rear spindles. Two cutting set-ups were performed – first, with both spindles rotating clockwise and second, with rear and front spindles rotating in clockwise and counterclockwise direction, respectively. The results revealed that, given the lead frame strip is in a dead bug position, cutting in counterclockwise direction, with feed direction against it, will result to production of large quantity of IC units affected with metal burrs or smearing. On the other hand, cutting in clockwise direction in the same lead frame strip position and in parallel to the direction of feed will produce little to no metal burr or smearing.