When we create a device, it's easy to connect several pads to the same pin, ( for earlier Eagle version, to several pin with the same name (ex : GND@1, GND@2 ...). When we use a device with several pad to the same pin, Eagle consider that all the pad should be connected, so there is an airwire on each pad. That 's great because it's mostly what we need.
But in some cases, it's not quite what we need, and routing one of those pad is not mandatory. For example I have heat-sink, with 3 fixing pads, which are all connected to one pin (usually connected to GND but not necessary ). But on my board, I have one of them that can not reach the GND plane (it's 'lost' in a high voltage area). So the only 2 options I have are :
- I consider my board finished, even if I have ariwire left. I can leave with that, but when I send my .brd file to the PCB house they ask me why this ariwire is not routed....
- In the library I separate the third pad. But it's worse because of 2 problems.
The first, (but not the worse) is that I have to create different packages, depending on the board where I use it (It's not necessary the same pad that must be left unconnected on every board). Second problem is that the pad is not anymore connected to the signal of the 2 other pads, so the isolation with other signals around the pad is no longer respected, since there is no signal connected to this pad, no signal = default class.
There is also other components (such as battery clips), that can have this problem, and some time the component itself may be use as a bridge.
So my little suggestion would be : when we create a symbol, and connect several pad on one pin, we can add a 'bridge' option. So Eagle will know that at least one of these pad need to be connected, and the other connection are not mandatory. The optional ariwires could have a separate color (or layer so we can display or not). After a ratsnest, the result could look like "ratsnest : 16 airwires, 1 optional airwires" or "Nothing to do but 1 optional airwire".