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I am curious, are there any reasons why Altium tends to route a trace to the side of a pad, instead of the top? The top looks more logical, since it will not disturb other traces in a SOIC for example. I am including a picture for reference.

EDIT: I am not using Auto Route. It's the snap of the trace on the pad that bothers me.

Altium trace connection

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Short answer: because autorouters are still pretty dumb. As long as it isn't violating any of your design rules, there's nothing "motivating" it to move the trace where you want. – The Photon Dec 12 '12 at 20:18
up vote 4 down vote accepted

It's worth noting that the mouse-snap actually uses the autorouter to some extent.

Depending on the routing mode you have enabled, it will behave differently. Shift+ R while in the interactive routing mode (e.g. placing traces) changes the routing mode.

Anyways, if you want to change the orthogonality of the traces as you're routing, you just press the space, and it should try the other angle (note that some routing modes are more responsive to hitting space then others in the more recent versions, particularly if you have pin swapping turned on).

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Autorouters typically employ a scoring system for figuring out "optimal" routes. Vias cost a certain amount, distance costs, angles have a cost... The lowest cost overall "wins."

But this by no means imbues the autorouter with any sense of artistic quality or knowledge of what is aesthetically "better." There are certain steps taken to ensure electrical quality, but it is only enforced through rules and scoring.

The autorouter on any PCB design package should be used on a limited basis as a helpful tool, in some small areas (not the whole board!) and certainly should not be treated as a "final" route.

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I am not using the auto route, sorry I didnt made it clear...it's the "snap" of the mouse – mFeinstein Dec 12 '12 at 20:43
Ah, that is an important distinction. – JYelton Dec 12 '12 at 21:11
But more or less the same issue. Altium doesn't know the long side of the pad is any different from the short side of the pad, and doesn't have any preference to connect to it one way or the other. – The Photon Dec 12 '12 at 21:47

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