Sparkfun Button Pad 4x4 - Breakout PCB COM-08033Sparkfun
This a simple breakout board for the button pads. Each LED and button is brought out to the side connectors. The connectors are soldered to the back side of the PCB. We recommend trimming the connector leads on the button side as short as possible to reduce the deflection of the pad.
Now with footprints for diodes! Use the super cheap 1N4148 through hole diodes. These can be used to isolate the switches to make for a bit easier decoding.