Hi All,
Many components, even if they are placed “on grid”, have pads that fall “off grid”. In many instances, by starting from the off grid pad, a trace will come off the center of the pad, but not always. In some cases, identical components placed side by side will have a different behavior WRT how a trace connects to the off grid pad. Frankly, it’s kind of maddening! Is there a way to force a trace to attach to the center of a pad, regardless of whether it’s on grid or not?
John
It depends on the software. It isn’t a problem with the Pulsonix software I use.
You are going to have to post a pic of what you mean. But, from the way I understand, why would it matter if it’s off center? As long a it’s touching, there should be no problems.
Leon’s right though, what program are you using? That would be a good start to solving your issue…
Hi All,
Ugh, of course, I guess I just assumed that everybody uses Eagle, ha, ha! I can post a picture tomorrow, but in the instance that I’m thinking about right now, I have an SMT resistor (0603 package, I think) that has as its ‘center’ the mid-point between the two SMT pads. That mid-point is placed on the grid during part placement. The centers of the pads on either side of this center point are some odd-ball distance from the part center, and are off grid. Most of the time I try to route the connection to one of these pads, it enters/exits the pad offset from the pad center.
John
PS I’m using Eagle 6.4.
Change the grid…
I often set my gridsize very small to place lines just where I want them, alternatively use the alt grid size.
If you are trying to route an IC that has fine pitch, you have to change your grid. I usually end up setting it to 0.001 on the secondary. Hold “alt” to use it.
Here’s a little tut if you don’t know how to set it.
It’s not that the pads are off grid, the pads will be where they need to be.
It’s your routing grid that needs to change.
Many components are still made to a 0.1" (or derivative) imperial grid because that’s the pitch they were originally created at so they remain the same. Many newer components are on a metric pitch because they are new & do not have to support legacy components.
As such, we - the people making a PCB have to cope with both measurement units and change our grid when needs be.
I have always found that routing out of the pad instead of into it is best to prevent the route offset\dogleg of the track.
Not that it really makes a lot of difference when you do.
If you have design rules that you can follow, and an online DRC then you do not “need” to use a grid - it just makes routing easier.