Comments on my first PCB layout please

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ej_whyte

Well-known member
Joined
Nov 12, 2010
Messages
263
Location
Cambridge, UK
Hi,

Heres my first pcb layout, just looking for some comments and guidance please.
The circuit is 4 channel summing, stereo with the neutrik stacked jacks. 680R shunt and Cinemag CM-75101APC. Its part of a larger circuit for a project im working on. Also the first time I've made an eagle library, the cinemag and neutrik jacks.

Cheers

schematic-1.png

all.png

traces.png

placement.png
 
Looks pretty good so far. I'd increase the trace width a little wherever possible, and add the parts names to the silkscreen (R1, R2, etc), makes troubleshooting much easier. Also, flood the ground plane. Here's a link

http://www.muzique.com/schem/eagle.htm
 
Ptownkid said:
Looks pretty good so far. I'd increase the trace width a little wherever possible, and add the parts names to the silkscreen (R1, R2, etc), makes troubleshooting much easier. Also, flood the ground plane. Here's a link

http://www.muzique.com/schem/eagle.htm

OK thanks, ill have a look at that.

The mains things i wasn't sure about were proximity of the traces around all the summing resistors and the GND hole. To make the GND I just placed a via over that ground trace, but I wan't sure if there was anything else special I would have to do?

Cheers
 
You may want to stay away from 90 degree angles on traces.  Generally you want a 45 degree angle at the bend.  I also prefer straight lines, rather than long angled lines when possible.
 
It looks good. A few comments:

1) You can increase the penetration of your ground flood by moving a few of the resistors and decreasing the isolation down to about 20 mils.  
2) Will you be fabbing this or are you going to have a PCB house do it?  
3) I would turn off the tvalues layer and turn on the tnames layer:  part designations are much more useful when assembling than the values, which you can just read from the schematic.
4) Turn on thermal relief's for the ground plane connections.  Without them soldering those connections can be a PITA and leave you with cold joints.
5) Change the right angles in the traces below the Neutrik connectors to 45 degree angles...you'll get much cleaner etches that way. Not as big a deal at 0.8mm trace width, but it also looks good too (and PCB's are as much art as function).
6) Make sure your DRC matches your board house.  Sparkfun has a good one for Eagle good for 7mil x 7mil design rules which most fab houses can support.  In particular fab houses are picky about annular ring and minimum drill sizes (yours look fine just by visual inspection).
 
Matador said:
It looks good. A few comments:

1) You can increase the penetration of your ground flood by moving a few of the resistors and decreasing the isolation down to about 20 mils.  
2) Will you be fabbing this or are you going to have a PCB house do it?  
3) I would turn off the tvalues layer and turn on the tnames layer:  part designations are much more useful when assembling than the values, which you can just read from the schematic.
4) Turn on thermal relief's for the ground plane connections.  Without them soldering those connections can be a PITA and leave you with cold joints.
5) Change the right angles in the traces below the Neutrik connectors to 45 degree angles...you'll get much cleaner etches that way. Not as big a deal at 0.8mm trace width, but it also looks good too (and PCB's are as much art as function).
6) Make sure your DRC matches your board house.  Sparkfun has a good one for Eagle good for 7mil x 7mil design rules which most fab houses can support.  In particular fab houses are picky about annular ring and minimum drill sizes (yours look fine just by visual inspection).

OK, thanks for the help everyone.

2. Hopefully get a PCB manufacturer to do it, if it isn't too expensive, any idea on cost? If not, what changes need to made for home fab?
4. Thermal reliefs. Don't have a clue what they are. I'll google it.

I'll get on the 45 degree angles in a bit

Cheers
 
You might also consider having un-used inputs switched to ground to keep the gain the same no matter how many channels you are going to plug into the bus. 
 
I am also working on my first circuit board layout in DIY layout creator. Haven't really got a handle on Eagle yet. What does flooding the ground plane do, and is it something that should just be done all the time?

Gotta figure out how to do this in DIY lc. 
 
Insomniaclown said:
I am also working on my first circuit board layout in DIY layout creator. Haven't really got a handle on Eagle yet. What does flooding the ground plane do, and is it something that should just be done all the time?

Gotta figure out how to do this in DIY lc. 

Actually it does many things:  provides some shielding for signal lines, adds capacitance to the ground connection and can improve noise immunity, better controls impedance, etc.
 
Updated with thermals & 45 degree angles all round.

With regards to switching, I have chosen not to use it to do with other parts of the circuit, thanks anyway

Screenshot2011-05-10at173836.png
 
Matador said:
Insomniaclown said:
I am also working on my first circuit board layout in DIY layout creator. Haven't really got a handle on Eagle yet. What does flooding the ground plane do, and is it something that should just be done all the time?

Gotta figure out how to do this in DIY lc. 

Actually it does many things:  provides some shielding for signal lines, adds capacitance to the ground connection and can improve noise immunity, better controls impedance, etc.
In addition, it uses less chemicals since there is less copper to etch. :)
 
abbey road d enfer said:
In addition, it uses less chemicals since there is less copper to etch. :)

Ahh yes! How could I forget!  Show you how long it's been since I've destroyed the liner to a bathtub with Ferric Chloride!  ;)
 
Matador said:
abbey road d enfer said:
In addition, it uses less chemicals since there is less copper to etch. :)

Ahh yes! How could I forget!  Show you how long it's been since I've destroyed the liner to a bathtub with Ferric Chloride!  ;)

This is one of the reasons why I am going to try the sponge method for my first etch. I am working on replacing the circuit in my Apex 180's with the mk 012 circuit. I was going to do the etch resist with a sharpie. Now I am not so sure. Things look so much bigger on the computer screen! Think I should get some press n peel blue before I go any further.
 
sharpie is a no-go, especially with the sponge method... they do make other markers specifically for this, but just a thick ink marker will be best. I just did a hand drawn PCB for a g7 circuit with sharpie and the ferric started to eat it away toward the end of the etching. no cut traces, but just took off small scratchy bits off the traces and left rough trace edges.
 
Thanks for the info. Well, press and peel blue it is. I keep looking at the PCB, and I know for a fact that my big hands will make a mess of it anyway.
 
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