Three panel tab assembly tips. By Duane Benson
Many small quantity PC boards are ordered individually cut. They come to Screaming Circuits as a set of unconnected boards. For small quantities of reasonable size boards, it makes the most sense to order them this way. However, for really small boards and larger quantities - 50 or more - purchasing boards in a panel (also called an array) is more appropriate. It reduces errors and assembly time.
There are three additional factors to consider with panelised boards:
1. Avoid family panels. A family panel is when several different boards are put onto the same panel. The boards in family panels often repeat reference designators, which causes problems at assembly.
2. Don't try and create a panel in your CAD software. Just lay it out as a single board and have the FAB house put it in a panel. You'll get the most efficient use of PCB space that way, and the FAB house will create the files in the format that the assembly shop needs.
3. Avoid overhanging parts. If you have overhanging parts, like the increasingly common micro USB connector, make sure that the panel tabs aren't placed near the overhanging parts. If you have overhanging components, make sure that the panel tabs are not placed where the overhanging components are. Some components have protrusions that will keep them from laying flat on a panel tab. In all cases, even without the protrusions, the operation of separating the panels with a component on the tab can weaken the component solder joints, or even pop it off the board completely.
Duane Benson is the Chief Technology Champion at Screaming Circuits, a prototype PCB assembly electronic manufacturing company in Oregon, USA.