Parts on bottom layer of PCB, use mirror?

Very basic question. I did find some hints of answer on the forum but just want to confirm. My question is: if I want a part on the bottom layer, I use mirror function in Eagle to do it, right? All I want to do is to save space. I want an LCD on top of the PCB but it covers up a large area that can't be easily used. I want to mount my atmega 328 on the bottom, beneath the LCD. I want to tell Eagle that the chip is going on bottom layer, or hanging upside down. Thanks.

if I want a part on the bottom layer, I use mirror function in Eagle to do it, right?

no! you change the layer of the part to "bottom".

If all the parts are going on the bottom except for the LCD, I'd probably design the board upside down, such that the LCD is on the "bottom".

Don't forget, you may be able to put some parts under the LCD (especially if they're small, e.g. SMT, parts).


I actually don't know how to put anything on the bottom layer. I tried change object properties with the "wrench" icon, no way to pick the parts always the yellow lines. Any help? Thanks.

Actually I think you do use mirror - on the Board view. That's how I did it for SMT parts anyway.

Thanks. For LCD that has a 16pin one row pin headers connector, I can just rotate 180 and not worry about it, right?

Assuming you're in the board view, use the mirror tool (under the move tool) and click the part you want to stick on the bottom... or, while you are moving a part around: left click - place, right click - rotate, middle click - mirror

Thanks nickvd. I didn't know middle click.

Hmm, interesting! I have enough trouble trying to visualize how to rotate/mirror things for single-sided toner transfer. Double sided would be a nightmare! :open_mouth:

I am going to be trying my first double sided board soon... I tried to integrate an atmega on my board, but could not get the routing completed on a single side...

I'll be sure to post my results when/if i get around to it :slight_smile:

A couple pics of the boards i've made are below (toner transfer using random hp photo paper i had laying around on a hp lj P1505, etched with FeCL)

My first (variable voltage regulator):

Button board for my Connect Fourduino project:

Control board (back) for the Connect Fourduino:

Control board (front) for the Connect Fourduino:

5x2 Pin header to .01 breadboard (left) and 7x5 led matrix board to two 5x2 pin headers (rows and columns)

Etching is FUN!

Ive just done my own double sided.
Have a look at Sideuino - My Scratchpad

Ill have to get round to putting the eagle files up.

Why not have a look at the eagle files published for the official boards.
I used them as part of my learning curve by looking at how the parts were laid out on each side and the traces.


Thanks for the answers. I've mirrored the part that are on the bottom layer. Hope it works. This circuit board is the most complicated I've ever designed. Still working on drill bit selections and what stand-off to choose. Making PCBs seems like both electrical and mechanical, a little tough for me since I was trained neither electrical nor mechanical.

The toughest part for me was getting used to eagle itself... besides the routing of course, which has made me tear nearly all my hair out :wink:

Eagle is pretty ridiculous.. Perhaps the dumbest thing I have ever seen in a CAD program was the need to "invoke" parts of IC's in Eagle. For example: Op Amps need to have the "power" pins invoked into the schematic so you can connect to them. Is there ever an instance where you wouldn't need the power pins for an Op Amp?? Talk about frustrating. I had no idea why they weren't there and couldn't have my board cut until I figured it out. In the end I guess I should just be grateful that Eagle is free.

Here is the aforementioned circuit board:

I had to run a couple of jumper wires, but all-in-all I think it came out pretty good for my first board. I should clarify that I didn't etch this. It was made on a CNC router at my school.