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I am designed a PCB in Eagle and I am new to doing this. I have created a ground plane on the bottom layer that covers the whole board but I still have a few traces running through the bottom layer (see the attached picture). The reason I did that is because those components for which I did that to, soldering the pins on the top layer will be very hard when the component is placed on the board. That is why I moved the trace to the bottom layer so I could then solder the pin. My question is, do I need to do that? All of the pads are meant to be thru-hole pads so does that mean a pad will be placed on both the bottom and top layer? If that is the case, can I still run all my traces on the top layer because I will be able to solder all the components on either the top or bottom layer? Overall, I need your advice on how to go about making traces for components that I can't solder on the top layer and that I still want a ground plane. enter image description here

I attached the schematic also. Right now, all of my traces are 10 mil wide. This circuit is a simple current amplifier that uses the OPA548 amp. The other components are a DC-DC converter to get +-15 to power the amp, some decoupling capacitors, and resistors to dictate the gain and current limit. At most, the op amp will be pushing around 750mA. Is a 10 mil wide trace enough for that? What is the best way to determine trace width?

enter image description here

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  • \$\begingroup\$ I have a sneaking suspicion that a lot of your trace widths are inadequate. No way to know for sure without a schematic. \$\endgroup\$ – Matt Young Mar 25 '15 at 13:53
  • \$\begingroup\$ any particular reason you are not doing this as mostly smd? \$\endgroup\$ – PlasmaHH Mar 25 '15 at 14:05
  • \$\begingroup\$ Your question is a bit confusing. Above the 1st picture you're worried about "breaking" the ground plane by some traces, below the 1st picture you're worried about the current capability of any trace and the title just says "ground plane". So what's your actual question? Whether breaking the ground plane does harm or current capability of traces (there are definitely questions with answers already)? Temporarily down voted until clarified. Please note not to make a fourth question when editing. \$\endgroup\$ – try-catch-finally Dec 23 '16 at 9:44
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Yes, through-hole components will have copper pads on either side. Similar to this:

enter image description here

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  • \$\begingroup\$ Not necessarily, only if the pad is plated through and on both layers. It's very possible to have a through hole pad on only one layer. \$\endgroup\$ – Matt Young Mar 25 '15 at 13:52
  • \$\begingroup\$ @MattYoung, Is this a special request to the board-house to reduce copper? Or perhaps a parameter in Eagle when developing the footprint? I have never had a through-hole component with a single-sided copper pad. \$\endgroup\$ – sherrellbc Mar 25 '15 at 13:57
  • \$\begingroup\$ There are plenty of cheap consumer widgets that use single sided, stamped boards. As to Eagle, I cannot say. Any real CAD package should give you the option to do whatever you want with a pad. \$\endgroup\$ – Matt Young Mar 25 '15 at 14:03
  • \$\begingroup\$ @MattYoung, since s/he's using vias to connect his bottom layer traces to top layer traces, I think it's a safe bet he's having the board plated. Of course it's possible to also make non-plated holes, but the library footprints will have plated holes. \$\endgroup\$ – The Photon Mar 25 '15 at 15:50
  • \$\begingroup\$ @ThePhoton I'm sure he's fine, my issue is with the blanket statement that through hole components will have copper on both sides, which is not always true. \$\endgroup\$ – Matt Young Mar 25 '15 at 15:54
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It doesn't matter what layer the tracks are on in the case of through hole pads.

The reason for this is that the PCB manufacturer will place a pad on either side and the hole will also be lined with copper so that the pads on either side are connected to each other. This way you can solder on the component whichever way you like, and you do not have to worry about what side the track is running on.

The only time the track needs to be on a certain side is if it is a surface mount component and then the pad will only be present on one side (unless you have a vie on the pad but that's neither here nor there).

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Assuming you did your foot prints correctly then a through hole will have pads on the top and bottom that are connected to each other during the plating process. It's effectively a via. You don't have to via down to the bottom layer to connect to them. Further eagle must have some kind if rats nest and report showing in connected nets. After you hook up everything on the top layer you should see zero unconnected nets and that should give you confidence that you've done it right.

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  • \$\begingroup\$ When you generate your gerbers for production load them into a free gerber viewer to double check that you see pads on both your top and bottom layer \$\endgroup\$ – Some Hardware Guy Mar 25 '15 at 13:54
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I think, for this circuit, the ground plane is not even necessary. A one layer PCB will, almost certain, do the job. But since you are probably sharpening your skills as a PCB designer let's point some things.

Firstly, the thumb rule for width of traces (for the typical 1 oz of thickness), is 1mm (39,37 mils) per Ampere. So, for 750mA, approximately 30mils will be fine.

Secondly, as Dr. Howard Johnson recommends (you can see some of his job on https://www.sigcon.com/), your ground plane must be solid with none splits, gaps or traces always when it is possible. So, at least, try to short the bottom traces if is not possible to remove them.

Also, try to figure out if you really need the DC-DC converter. There's another ways to supply your OPAMP without the need of this big component.

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  • \$\begingroup\$ Lastly, your PCB seems bigger than necessary. Why not try to route one with half of size? \$\endgroup\$ – Pedro Quadros Mar 25 '15 at 18:16

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