Development of a pre-mold lead-frame for multi-row QFN package

QFN and Dual row QFN (DR-QFN) are mature packages which the current industry can only provide IC assembly for body size less than 13×13mm, with less than 180 IO counts. At present, substrate with Ball Grid Array is often preferred as the market trend for more pin counts requisition. Yet, the cost of substrate is significantly higher than lead-frame. By applying the concept of trace routing in a conventional substrate to intermix with QFN lead-frame manufacturing process, an ordinary QFN package was then reborn to support for more IO pin counts and larger body size, which this multi-row QFN has a new name - enhanced QFN (eQFN, by SPIL). Apart from the standard etching and punching manufacturing process on a conventional lead-frame, the lead-frame for eQFN adopts plating process, such that it is similar to Cu plating of a substrate. The conventional drilling was replaced by photo and plating process, that makes the luxury of having 30um/30um line width/space not a concern for higher cost. A pre-mold process was employed to sustain the Cu trace within lead-frame, providing the physical strength for the resined strip to survive the rest of assembly process. By using such lead-frame, the number of IO could be increased up to 400 and the maximum body size extended to 15mm×15mm. Two test vehicles (body sizes range between 10×10mm to 15×15mm, IO counts range between 200 and 350) were studied. Affirmatively, the goal were achieved to replace current TFBGA with offering the same package outline and pin out as well as identical ball assignment. In this report, reliability and functional verification between the two package types were compared. Thus eQFN is the new package with breakthrough technology in place of current TFBGA under certain conditions.