Determination of Optimal Setting for the Tape-Based Partial Package Sawing of Wettable Flank QFN Package

Wettable flank Quad Flat No Leads (QFNs) have been developed nowadays to meet the demand of semiconductor industry to produce IC devices that enable easy visual examination of solder joint integrity. This capability of these devices is attributed to their solderable sidewalls, which can be created through the introduction of plated sidewall, dimple, curved punch, or step cut at the terminal ends of the QFN package. The latter step cut option can be formed through partial package sawing. To achieve desirable step cut quality, sawing parameters such as feed speed and spindle rotational speed must be identified, employed, and maintained at optimum level. Thus, the objective of this work is to establish optimal parameter combination for the partial package sawing of wettable flank QFN package. Experimental runs were carried out in a tape-based sawing machine. From the results, it was found out that the metal burr produced is getting larger as spindle revolution is increased at constant feed speed. At constant spindle revolution, on the other hand, no significant changes in burr length were observed as feed speed was increased. The identified best parameters were 30 mm/s feed speed and 30000 rpm spindle revolution. This produced passing burr measurement without internal package delamination.