Aim for large pads with tight fitting holes for your leads.

The pad/land mass around the holes takes the full strain exerted from the component leads. With only a thin annular ring the smallest pressure applied onto a component lead can lift the pad. As a rough guide multiply the hole diameter by a figure in the range of 2.5 to 3. If space is at a premium elongating the pads works well. Larger pads will also help prevent de-lamination should any rework be required. 

Unlike PTH boards it is very important to have close fitting holes especially on connectors. Dry joints frequently occur where the solder bridges over the gaps. In certain industries it is normal to make S/S boards with plated through holes specifically to eliminate the associated risk.

If larger clearances can be maintained it is often possible to Silk Screen the etch resist onto single sided circuit boards as opposed to using the more expensive dry film resists.  Which can lead to a moderate cost saving especially on the larger production batches.

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 Rev  08 October 2024

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