Eagle Q re: copper through pads

[mth5044]

I'd been using PCBExpress for a while, but I've been trying to learn Eagle, due to someone pointing out the Dorkbot PCB fab service. I'm also using the GM eagle components.

My question is how to make pads that are on the bottom 16 layer also connect to the top 1 layer? I see how to put vias in, but it would be so much easier if the bottom solder pad that the component is soldered to would be plated through with copper so a trace on the top layer could continue without having to add in a via. Would I have to change the pad information or something? It says I can't add a via overtop of the component pad, so that won't work. Any ideas?

I'm also having trouble figuring out how to make 'thermally coupled' pads to connect to the surroundings, such as a ground plane.

Thanks a lot!

[Taylor]

I don't use Eagle and am not too familiar with it, but by default any component with a through hole should have a pad on both top and bottom which are connected with a plated through hole. I just pulled up Eagle and it seems to do this. Am I looking at it wrong or something?

Normally all holes will be plated unless you specifically mark them otherwise.  Some fab operations (usually proto services like Dorkbot) will plate all holes even if you wanted some unplated, or they will upcharge 50 bucks or so to do unplated holes.

I couldn't figure out how to make thermal pads either, even with a bunch of Googling just now. What an obstinate program! How I love Osmond CAD.

[mth5044]

Good to know, Taylor! I had just tried drawing a trace on the top layer of a pad, and it didn't have any fuss about it, so it looks like you are right.

I have never heard of Osmond CAD, I will do some googling!

[Taylor]

Osmond is unfortunately only available for Mac. But it is completely free and has no real limitations like the free version of Eagle does. I originally chose it because at the time I was using Macs only. But it was so much easier to learn and now I'm so used to it that I use it even though I've got a PC now. I have to yoink my girlfriend's computer to do PCBs now. I find it a lot more intuitive than Eagle, but it's just a matter of finding something that works for you, so others might prefer Eagle.

[mth5044]

Ah, well no mac in sight here  

So I figured out how to turn the thermals on and off, I just don't know how to make pads on components into thermals.

And since posting, I've come up with yet another question. I intended the top layer as a ground plane, being made with the square tool. However, there are 5 or six traces on top that making the ground plane obliterates (not to mention going over every pad). Any way around that?

[Taylor]

It's something goofy, like you have to go through and select each trace, set it to something, hit rat's nest, blah blah. You've probably seen this if you're using his library, but GM has a tutorial for Eagle where I'm pretty sure he explains how to do this all:

http://gaussmarkov.net/wordpress/tools/software/eagle-cad/

[mth5044]

Oi, I did read that, and tried and failed a few hours ago... surprising what a few hours of tinkering can do to make a tutorial make so much more sense! I got a ground pour, its routed around pads and traces, it's connected to everything I said to connect to.. BUT it doesn't have any thermals

But maybe it won't matter. From what I understand, thermals are there so you don't have to struggle with heating up the entire ground to get it to solder. I won't be soldering on ground pour side (hopefully, unless they aren't actually all copper through holes), so maybe the single pad on the bottom will be small enough to get the solder stuck and no problems!

Thanks Taylor!!!

[defaced]

BUT it doesn't have any thermals

Check the settings in the DCR.  The supply tab is where the thermals come in.  And yes, you want them, they do make a big difference when it's time to assemble. 

Pads are their own layer, and depending on how you define the Gerber files, they can be on whatever layer you'd like.  Usually they're on the top and bottom though, and like Tylor said, processed however the board house does them. 

[mth5044]

Thanks defaced. I went under the DRC and the supply tab, and the only bits it says about the thermals is to change 'isolate' which is at 10mil, a restring check box, and another check box that says 'generate thermals for via's'. I have both boxes checked. Can't figure it out 

[Gurner]

Re pads into thermals with Eagle - my SMD pads are automatically turned into thermals should they be located on flooded bit of copper - in other words, I didn't have to turn the option on. The isolation setting is important under DRC, as this sets the amount pads are erhm isololated when the pats sit on a copper flood.


Can you do a screen shot of what your copper plane looks like with your eagle board - it'd help sport the problem a bit easier.

[mth5044]

Alright, here is one I'm working with. You can see all the ones that are attached to the ground pour (C12,11,4,5,3,pins 3 and 4, etc) are just floating on the plane.

[Gurner]

I can't help much here as when I read PADs at the foot of your original pst, I assumed a 'pad' in the SMD 'pad' sense of the word- I can now see this pad query relates to through hole. I only work in SMD & certainly all my Eagle SMD pads are isolated when on a copper plane (without anything being preset) ...Eagle must treat through hole pads differently to SMD.

I can recommend asking the Eagle oracles (using your screenshot)....

http://www.eaglecentral.ca/forums

you'll have an answer within hours.

[defaced]

Post the actual egale files (or dummies with a couple of parts deleted if you'd rather not share the details of the circuit).  Without the schematic we can't see what the ratsnest is doing and where there error could be.  The schematic and board files work together to make the final board.