We recently had a pilot run of our new boards. I just received some DFM feedback regarding the two PCBAs associated with the boards.
Several of the TI parts on the board such as the LP2951AC have exposed die paddles that are soldered to the PCB to help keep the parts cool. The recommended footprints given in the datasheets for these parts include vias on the PCB pad for the exposed paddle to help transfer heat to inner layers of the PCB (see LP2951 datasheet page 33). The manufacturer indicated that when the solder paste reflows, solder wicks through the vias in the pad for the exposed paddle and forms solderballs. The manufacturer ended up putting Kapton tape over the via holes as a temporary measure. I tried to keep the PCB design as generic as possible so that virtually any shop should be able to produce them, so the via hole size is 10mils. Can you give me any suggestions to prevent solderball formation in this scenario?
Thanks!
Russell
