Archive for September 26th, 2010

Copper Tape for PCB Edge Binding

I’m laying out a PCB with ampere load currents, millivolt sense voltages, and PWM drive, all connected to an Arduino’s strictly digital ground layout through the usual headers. While I’ve laid the board out with the high-current stuff over there, the sense inputs here, and the PWM as far off in its own corner as possible, I fear this will get ugly.

One step to reducing the noise involves a decent ground system. The Arduino pretty much eliminates the whole single-point ground concept, so I’m using a double-sided ground plane with plenty of Z-wire stitching , plus copper tape around the edge binding the top and bottom planes.

Copper tape on PCB edge

Copper tape on PCB edge

The PCB is 60 mils thick, so I cut four copper foil strips about 3/16-inch wide, folded them around the board edges, then burnished the surfaces flat.

Although the tape has adhesive on one side which is allegedly conductive, I figured running a solder bead along the edges couldn’t possibly hurt. That worked out reasonably well, if you don’t mind blobular solder along the edge of your board.

Copper tape solder joint

Copper tape solder joint

The joint along the bottom edge shows one problem: some adhesive oozed out while soldering and formed a barrier. I think that happened along the tape edges from the outside of the roll, because it’s most prominent along two board edges.

Memo to Self: Slice off and discard the outer few millimeters. Mask the outer board edge for a solid pour, not a hatch.