Layout questions: Ground pour and trace width

Started by ballooneater, December 04, 2008, 10:08:29 PM

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ballooneater

Two questions regarding PCB layouts:

-When creating a PCB for a low-voltage application (effect pedal, synthesizer, etc.) is it important or beneficial to have a ground pour?

-What is the smallest feasible size I could make the PCB traces (in mils) that would still come out using the toner transfer method and typical materials? (I know this will vary from person to person, but an average would be nice)

Thanks for your help!

Zben3129

I think it's beneficial to have a ground plane simply because etching is quicker and uses less etchant.


Zach

rnfr

Quote from: ballooneater on December 04, 2008, 10:08:29 PM
Two questions regarding PCB layouts:

-When creating a PCB for a low-voltage application (effect pedal, synthesizer, etc.) is it important or beneficial to have a ground pour?

-What is the smallest feasible size I could make the PCB traces (in mils) that would still come out using the toner transfer method and typical materials? (I know this will vary from person to person, but an average would be nice)

Thanks for your help!
wait a second... i thought you were an eagle expert?

ballooneater

You caught me!

I suppose I should specify that I am a "heavily experienced schematic to layout-er that knows the UI inside out but is still learning the practicality of it all" but that would take up too much space.

earthtonesaudio

Less unnecessary etching is also better for the environment.  :)

Papa_lazerous

I almost always use a GND pour as said above it uses less etchant, better on your pocket as well as the environment a no brainer.  Also just route signals voltages etc and then do "POLY GND" draw it round your circuit and you will have all your GND's routed I find you can get away with allot this way without needing jumpers across traces and lends to a neater layout. Also having everything surrounded by GND helps with noise issues in many cases.

as far as clearence in mills (thousandths of an inch to those who think mils are mm's)  I would stringly suggest you use your own judgement and common sense on this one.........  Do a layout and print it, if it looks stupidly small then it is!  if you right click around the edge of where your GND pour is placed and click on the properties part of the drop down menu you will find you can edit the isolation clearence and thickness of the pour.  also go into DRC and change the thermal vias so it suits your needs.  track width 0.024 to 0.030 may be a good starting point for you, its by no means the smallest you can go but why make it too small.

As someone suggested above you know Eagle so what I am saying should/will make sense :)

ballooneater

Thanks for the tips, everyone!

I think all my questions have been answered.

Papa_lazerous

#7
dont be shy to post a pic of your board when its done.....sometimes others can see you cannot and you may end up with some more tips or ides


PS: you're sig cracks me up.......what with you asking mere mortals for advice   :P  :P  :P  :P  :P  :P  :P  :P  :P

ballooneater

I live for irony...

I've already made quite a few boards, that worked just fine without ground pours and used relatively large trace sizes, but I am attempting to make a SoundLab Mini-Synth board with a good number of mods, something that will take up at least 5in x 6in and use a double-sided PCB.  Just wanted to make sure I wouldn't screw things up.

Papa_lazerous

I can see a big problem..........Eagle wont let you do a board size that big.

Unless you either:

a) Have a license (Jealous)
b) Are running a crack (Not Jealous as I might have tried that once and found after an undetermined amount of saves it not only stopped working but locked all my eagle files by encripting them with the only way to fix them to contact Eagle and pay for a license before they will unlock them)

Zben3129

Quote from: Papa_lazerous on December 05, 2008, 11:53:44 PM
I can see a big problem..........Eagle wont let you do a board size that big.

Unless you either:

b) Are running a crack (Not Jealous as I might have tried that once and found after an undetermined amount of saves it not only stopped working but locked all my eagle files by encripting them with the only way to fix them to contact Eagle and pay for a license before they will unlock them)

Ouch! EagleCAD 1, crack software 0.

ballooneater

Let's just say that I'm backing up all my Eagle files now...

Papa_lazerous

haha its too late.......Even backed up those files will still lock up!

Even if you use a free license and someone you know uses a naughty license and sends you the file, it will still lock up.  Smart huh! google it there are loads of instances of it. 

So if you have saved files from a naughty license I suggest you load them and print them so you have a hard copy, as they are like a ticking bomb they can still lock even using a clean version of Eagle.  It must have some sort of system of checking the license used to save the file? I dunno