Vias in BGA Pads

摘要

The answer to the question "Is it ever okay to put open vias in BGA pads?" is simply "no." It's no, no, no, no, not ever!!! That makes it easy. No technique to worry about. No tolerances. Nothing. Just don't put an exposed via in a BGA pad. The only option is between the pads, with a complete solder mask dam between the pad and via, or have the vias filled and plated over at the board house. It doesn't matter if the BGA is sub-millimeter pitch or larger-than-millimeter pitch. Nothing but metal is allowed on the BGA pad. Now, other components offer more flexibility and thus require some choices and guidelines. Reader Andy B. asked about large components, such as voltage regulators, where the manufacturer has recommended vias to connect the thermal pad to the ground plane, or to additional thermal area on the back side of the PCB.