Ask Helena & Leo

Question: What is the spacing requirements between the board and the bottom edge of the component that doesn’t have a spacer or insulator in a supported through-hole terminations?

Answer: There are no spacing requirements for mounting components on a printed circuit board. The only requirement for mounting a component off the surface of the board is the heat the component will generate while it is operating, which if too high will burn the board. These types of components should be identified by design engineering when the product is designed and this condition should be identified on the product documentation and drawings.

You would also want to mount the component off the board if the component body interferes with the solder flow through to the component side of the board. This is where a spacer would be used to lift the component off the plated through hole which will then allow the solder to flow to the top side.

Radial components also have a coating which at times extend down the leads. According to IPC-A-610, the meniscus cannot go into the plated through hole and again this is a soldering issue related to solder flow to the top side of the board. None of these issues are related to a component sitting or touching the board itself.