IPC Class 3 Annular Ring and Fine Pitch BGA Challenges| 8 September, 2017
I have a few PCB boards i am trying to be manufactured that are miniaturized medical devices. Thus they require IPC Class 3 Specs.
However as miniature devices they have limited space, including a 0.4mm pitch BGA socket, which currently has several via-in-pads at 4/10mil sizing. They are designed currently as through holes for a mechanical drill. 4 Layer 31mil thick board.
One PCB house has informed me that due to the IPC Class 3 annular ring restriction these vias are impossible to manufacture. Hole cannot me smaller and pad cannot be larger. laser drill micro-via design are an option, at a significant cost increase and possible design adjustments on other layers.
Another PCB house has told me as they are Via-in-Pads they can be simply filled with nonconductive epoxy, and plated over. Then they are treated as typical BGA pads and the annular ring restriction will not not apply.