Slot for USB Connector Tabs

[Anonymous]

Need to make two slots for the side tabs on a USB Connector.  I have read posts and think I know what to do but want to make sure.   I have pads for the shape of the slots and then on layer 46 Milling, I drew a Wire the width of the slot needed.

Wires drawn on layer 46s

1.  Is this the correct procedure?

2.  Do I need to tell the board house anything specific, or is the Mill Layer info enough?

Thanks

[jm2morri]

Yes, that is about the best way to create slots currently in EAGLE.  However, you should have a PCB drawing or other document that clearly points out the slots, lists the details (like the intended slot width) and that you want them plated.  And you'll need to include a gerber file for the milling layer as well.

If you are using a prototype service that can't do slots, then the best you can do is to use a drill of the diameter of the length of the slot.  That takes a lot of solder.  When I need to do this and it's a hand build then I'll make the hole diameter just slightly smaller than the width of the pin so that it's a bit of an interference when inserted -- that keeps the solder you'll need to a minimum.  The bigger the hole, the more solder you'll need and the more likely you'll get a blob getting shorting out to the real pins.  However, these holes are big and if they interference with the signal pin drills then this won't work at all.

James.

[jm2morri]

One more thing, if you have internal planes (I can't tell) then you may need a cutout polygon under those pins so internal copper doesn't connect to the plated hole.  If those slots are connected to GND then you would want to add a thermal-type connection to any GND copper under the holes.  Since EAGLE doesn't handle these natively you'll have to make sure that the structures are created manually.  Best to look at the output gerber files to confirm, but you can use polygon cutouts to achieve both.

[jorge_garcia]

Hi @Anonymous,

I hope you're doing well. The slot should be made up of a contour of 0 width wires on the milling layer. Don't just use one wire with the thickness of the slot. The way you did it could work in older versions but the procedure now is to draw the slot contour.

Outside of that everything else James said is spot on.

Please let me know if there's anything else I can do for you.

Best Regards,

[Anonymous]

Thanks Jorge.  Like this?

[jm2morri · Accepted solution]

That looks good.  The zero width just removes the confusion about whether you want the tool to follow the center of the outline or the outer dimension (or inner dimension for that matter).  So that is why zero width is good.

As for your drawing, it looks OK.  You likely to make the pad a bit bigger to have a bit more copper left over, but it's not awful.  You should also confirm that your PCB fabricator can route a slot that narrow.   0.65mm is 0.026" and I know that ~0.032 is the smallest some places can route.  Confirm with your PCB fab what their minimum is and make sure the width is at least that.

James.

[Anonymous]

Thanks James.  The PCB shell, with the tabs, is usually grounded.  I have a ground plane on the bottom side of board where the USB is mounted and a power plane on the top side of board where the tabs come through the slots.  I don't want to short the ground and power planes together with the tabs so I created a polygon fill around the tabs on the top side and made it another ground, so ground is on both sides where the tabs go through.

Bottom Side of BoardTop Side of Board

Is this the right way to handle this?

[jm2morri]

Yep, looks like the right idea.

James

[scott]

Is native support for slots getting closer to release?  I know I've been beating this drum for a while, but it's a time-sink to create slots by hand for multi-layer boards, especially when thermal ties are needed to planes, plus DRC doesn't help very much with slots.

Thanks,

Scott

[jorge_garcia]

Hi @scott,

You keep beating that drum, I don't have an ETA for this yet so it's not in the near future. However it is important we are committed to implementing it.

That's all the info I have for now.

Please let me know if there's anything else I can do for you.

Best Regards,

[Anonymous]

With the advent of USB C connectors, I think it's becoming harder and harder to find connectors that do not require PCB slots.  This has gone from minor annoyance to major nuisance.  We need this in the next release.