Dead Copper

[Samuel Groner]

Hi

A PCB layout question: is it generally advisable to remove "dead copper" from a ground plane? I'm working on a discrete opamp (what else :green: ) layout and things are just too tight to get a ground connection to every edge.

Thanks for your input!

Samuel

 

[Svart]

personally I leave it in unless the design calls for it to be gone. in both etching and machining it takes time and money to take it off. When left in you can also use it to heatsink parts as well..

:thumb:

 

[tk@halmi]

If you are designing for the 990 footprint the groundplane is pointless as it is nearly ineffective. With just five or six transistors and a few resistors you may be able to pull it off, but you may not get the benefits you expected. Then try to stuff through hole parts in there without going insane and shorting traces to ground all the time. You may have guessed, but i have done it before on a ten transistor opamp.
A metal case that can be grounded is WAY more effective and leaves you with more space to create a convenient layout.
Metal cases can be made easily just using brass sheets and a small metal sheer. Cut out a cross with appropriate dimensions, bend the sides and you have a metal case that can be soldered. Total investment is less than eating a dinner out.

Cheers,
Tamas

 

[mnats]

Samuel - will you be putting your ground plane on the top or bottom? I was thinking if you put it on the bottom you could solder the can that tk@halmi suggested to it. Maybe then it would have a better shielding effect?

Oh yeah, the old-timer who I learned pcb design from would say remove all the dead copper. His reasoning was that during manufacture these patches can come off, causing problems elsewhere. Personally, I've never had copper come off the board except under extreme abuse.

 

[CJ]

save chemicals-less copper to etch...

 

[Samuel Groner]

Thanks for your answers.

Then try to stuff through hole parts in there without going insane and shorting traces to ground all the time.

My boards will have a solder mask so this should not be a problem. Sure a metal can would be nice to have, but I'm simply too lazy at the moment for this. :roll:

Will you be putting your ground plane on the top or bottom?

Both sides. I just route all traces and then see how the ground planes fill up the blanks. Like I have done it here: PCB.pdf

I don't think having a ground plane makes that much difference for a 2520 style opamp, but I do it as a matter of good practice.

Samuel

 

[tk@halmi]

[quote author="Samuel Groner"]

Then try to stuff through hole parts in there without going insane and shorting traces to ground all the time.

My boards will have a solder mask so this should not be a problem.
Samuel[/quote]

You will see what I mean when you put them together. That layout loks like a flashback to the house of pain to me. Save your old tooth brush for cleaning the solder side of the pcb.

 

[Samuel Groner]

So what would you have changed on this layout? I think I'd have ended up with the same/similar component placement without ground planes.

Samuel

 

[tk@halmi]

I would remove the extra copper and afford a little wider traces. Otherwise it is fine work.
Can I get a few when ready? :green:

 

[Samuel Groner]

I would remove the extra copper and afford a little wider traces.

OK, skipping the ground plane for wider traces makes sense to me. I have a good stack of boards with ground planes waiting on my desk allready, so we'll see how much trouble I have with this revision.

Can I get a few when ready?

Sure! At the moment it looks like you'll get them from Brazil. :thumb:

Samuel