When designing printed circuit boards, consider these tips for placing test pads to reduce fixture cost and improve testability.

Placing test pads only on the bottom side of the board enables use of a single-sided test fixture. This is much simpler and cheaper than a two-sided probing solution.

Deciding on the type of test probes and determining their minimum spacing before placement avoids unpleasant surprises later. A DRC rule can be created to check spacing for test pads placed arbitrarily, or alternatively placing on a grid is an easy strategy. For popular S-075 style probes, a 2mm grid works well and ensures that minimum spacing is met.

Carefully choosing test pad size and placement grid helps to make best use of the available space for routing traces. For example, using 1mm test pads on a 2mm grid with 0.2mm traces permits routing exactly two traces between test pads.

Avoiding vias placed off-center in test pads prevents test probes slipping into them and getting bent, causing binding and reducing reliability. Either put the via in the dead center, or avoid the pad altogether.

Read more tips like this in our free PCB Design Guide.