Metric BGA on standard 0.1" PCB grid (Eagle 7)

[ebastler]

This seems like a really basic question, but I can't see a good solution, and surprisingly didn't find one Googling:

I have a BGA with a 0.8mm pitch. Obviously I need to place vias and traces within the FPGA on that metric grid. But the PCB on which the BGA sits has a standard 0.1" grid, and for space and symmetry reasons the center of the BGA should align with that 0.1" grid.

So, can I switch to a grid with 0.8mm pitch and an offset which is different from the standard (0,0) used by the PCB's grid? Or what is the workaround for routing the BGA traces?

Note: I use the amateur/Make license of Eagle 7. Hence I can't set my standard origin to the center of the BGA, since Eagle won't allow pads in negative coordinate territory. Grmpf...

[ebastler]

OK, I found a workaround: To work on the routing within the BGA footprint, I move my whole design slightly relative to the (0,0) origin, such that the BGA center lands on a multiple of the desired 0.4mm grid.

- Activate all layers, to make sure they are all moved.
- Set grid to 0.4mm
- Group the complete board are with the mouse.
- Type command: "   move (> 0 0) (0.18 0.31)" (a relative move by 0.18 mm and 0.31mm)
- Work on BGA
- Later, move back with "move (> 0.18 0.31) (0 0)"

Awkward, but works. Which sums up that old Eagle version nicely. 

[jpanhalt]

I just have a key (F5) that lets me view and change grid settings easily.  I tried to make it a toggle similar to grid on/off, but couldn't get that to work.  The best I could get was to have default one system and the alternate the other, but then one loses the coarse/fine control.

[TomS_]

What's wrong with having the BGA aligned to a metric grid? As in, why does it have to be moved afterwards?

[ebastler]

What's wrong with having the BGA aligned to a metric grid? As in, why does it have to be moved afterwards?

Well, the PCB is a small, DIP-40 sized affair, with pins on the 100 mil grid. And there is just enough space for the BGA to sit between the two row of pins, so it has to be centered between them, i.e. centered on the non-metric grid (at least in one direction). Not much wiggle room there, not enough to center the BGA on a multiple of 0.4 mm.

[TomS_]

Ah ok, that's fair enough.

I would suggest checking out the latest version of EAGLE. There have been some VERY nice changes since v7, in particular since it is now "part of" Fusion (it's still a separate standalone application.)

Feature wise it now has push and shove routing, so as long as you setup your clearances etc properly in DRC then you can let the routing tool do all of the work centering traces between balls.

And you can now have full blown EAGLE for free on a year to year hobbyist license. Very easy to setup during the signup process.

So you could move the BGA to the 0 0 coordinate since you won't have board size constraints, set grid to 0.4mm, route traces just to the edge of the package, set grid back to 0.1" and move it all.

Well worth looking into as there are a couple of ways to achieve this very easily.

[jpanhalt]

And you can now have full blown EAGLE for free on a year to year hobbyist license. Very easy to setup during the signup process.

Yes, the new features are attractive, but how long will they last?  How long will a free version last?  Will any projects saved in 8.0+ be readable on 7.x next year or the year beyond when the free versions cease to exist?

Are you sure there is a free, new, standalone Eagle without a subscription to Fusion 360?  I couldn't find it.  Can you provide a link?

[TomS_]

You can "Save for version 7" from the File menu if you're worried about it.

I won't discuss any supposed merits of whether offering a free version is a good or viable long term option, pretty sure that has been done to death in other threads.

[TomS_]

You have to sign up for a Fusion hobbyist license and use your Autodesk account to sign in to EAGLE. IIRC that happens as part of the Fusion download process. I did it just recently but I don't recall the exact process.

The Autodesk website seems a bit like they don't want you to find it, but it was there.

[ebastler]

You can "Save for version 7" from the File menu if you're worried about it.

Ah, thank you for the hint! I actually do have a subscription for the current Eagle version -- took the plunge when they did their "ast chance to license Egle stand-alone" promotion. But I have shied away from using it since I did not want to lock myself into the new, subscription-based version forever.

I realized that the file format was changed, but did not notice the "save for version 7" option. Is that a "lossless" change of format, and could one go back and forth between the two versions without messing things up?

[jpanhalt]

This is the part of the sign up that concerned me:

One can read that two ways:
1) A one-year, now renewable free license; or
2) A year by year renewable learning license.

Tomorrow, I will download  and try it.  I am very much a pure hobbyist and have no commercial plans whatsoever (late seventies and retired).  I use Eagle frequently for quick schematics on various sites.    As for making real PCB's, more than twice a year would be a lot for me.   My personal library is pretty large, so new libraries are not a real advantage.   Ability to push and pull parallel tracks and an easier way to ensure plated slots are attractive.

[TomS_]

The way I was reading things, it sounded like it would be renewable. Certainly hope so!

Edit: this page seems to be suggesting they intend to keep a free tier for hobbyists: https://forums.autodesk.com/t5/fusion-360-design-validate/is-fusion-360-free-indefinitely-if-your-a-hobbyist/td-p/6280628

I have an older version of EAGLE 7 installed as well. Using that "save for v7" option seems to work reasonably well. A couple of error messages pop up about some unrecognised attributes or some such, but the boards and schematics do seem to be fully intact.