PCB design tips- edge clearance

Many PCB designers encounter with this problem when make the schematic drawing, "how close can I put parts to the edge of a PCB?" You don't want change your design after the PCB order already sent to the PCB manufacturer. So, let’s have a discuss below with SysPCB Shenzhen China PCB maker.

The problem is that there are a number of valid answers all governed by the phrase "it depends." I'm not going to leave it at that though. I could. But I won't. Not today anyway. It really does depend on a number of factors, but I think it can be nailed down a little tighter than that. You've got to start by considering a few things:

First, our old friend IPC-7351A does specify a keep-out area (AKA Courtyard Manufacturing Zone) on the part footprint. Keep stuff out of that area. This includes the board edge. Don't have any part of the component's keep-out area hanging over the edge of the PCB.

Second, look at your PCB mounting arrangement. Make sure the keep-out area does not interfere with any mounting screws, and that includes any washers you may be needing. If your PCB mounts with slots or rails, make sure the keep-out area doesn't interfere with any of the rails or slots or case edges.

Check with your manufacturer about their specific line limits. Many manufacturers have specific edge clearance limits based on their assembly line.

Take your application and consider those three items. Whichever gives you the biggest number is the Eagle corner edge clearance you need to follow. Based on your mounting scheme, you may have different clearance requirements on different parts of the board. Still, make sure that for each section of the board, you use the biggest number from above.

In the world of prototypes, things are a little different. At Screaming Circuits, we sometimes build up boards with parts right up to, and in some cases, over the pc board edge. You just have to ask yourself two questions for your prototype:
1. Is there enough copper to give a good electrical and mechanical connection to the PCB?
2. Am I likely to knock the part off the board with my handling?

If the answer the #1 is yes and #2 is no, then go for it. Of course, in the prototype world, you can always accept the risk yourself and go for it whatever the answers are. That's up to you. As part of any development process it is normally advisable to make a prototype before committing to full production. The same is true of printed circuit boards where a PCB prototype is normally manufactured and tested before full production. Typically a PCB prototype will need to be manufactured quickly as there is always pressure to complete the hardware design phase of the product development. As the main purpose of the PCB prototype is to test the actual layout, it is often acceptable to use a slightly different PCB manufacturing process as only a small quantity of the PCB prototype boards will be needed. However it is always wise to keep as close as possible to the final PCB manufacturing process to ensure that few changes are made and few new elements are introduced into the final printed circuit board.