Voltage and Amps Over Traces and Pours

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finalman
Posts: 4
Joined: 25 Nov 2019, 22:02

Voltage and Amps Over Traces and Pours

#1 Post by finalman » 06 Jan 2020, 02:22

I'm building my 2nd PCB ever and need help on making sure my traces and pours can handle the voltage and amp ratings that will be passing through them.

This PCB is a power supply adaptor from a 6pin PC power connector usually found on GPUs to a custom 8pin connector with prongs. It has three GND, three 12V, one 5V and a On/Off rail. The 12V and GNDs need to be able to handle upto 16 amps across them all combined. The 5V only needs to handle 1 amp. The on/off rail doesn't require much so I don't need help with that one.

Details:

5V Rail:
85mm long 1mm wide trace
One 2mm hole to 3.25mm pads

12V Rail
Three 4mm hole to 6mm pads
Copper pour at it's thinnest 3mm thick x 9.7mm long
Copper pour at it's thickest 6mm thick x 36mm long

GND Rail
Three 4mm hole to 6mm pads
Board Top side copper pour almost the size of the PCB 25x45mm.
PCB Bottom Copper pour at it's thickest 8.5mm thick x 7.5mm long
PCB Board Bottom Copper pour at it's thinnest 6mm thick x 36mm long

amp.PNG

Would it be true that I only have to worry about the copper thickness during manufacturing?

Will my PCB be OK at those voltages and amps? if not can you give me some tips...
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Tomg
Expert
Posts: 1523
Joined: 20 Jun 2015, 14:39

Re: Voltage and Amps Over Traces and Pours

#2 Post by Tomg » 06 Jan 2020, 08:24

Here's a thread that might help you figure things out - viewtopic.php?f=4&t=12949&p=27049
Tom

finalman
Posts: 4
Joined: 25 Nov 2019, 22:02

Re: Voltage and Amps Over Traces and Pours

#3 Post by finalman » 06 Jan 2020, 17:17

So after submitting my thread I came across the same circuitcalculator link from the reply to your thread. Unfortunately due to the space constraints around the 6pin power connector I won't be able to achieve the 3mm trace width cause it would require me to use 5oz copper which would be ridiculously expensive so I'll probably just solder a solid copper wire between the points.

rick.curl
Expert
Posts: 161
Joined: 14 Jun 2010, 16:46

Re: Voltage and Amps Over Traces and Pours

#4 Post by rick.curl » 20 Jan 2020, 14:57

Duplicate the traces on the other side of the board. That will help a lot.
If that's still not enough, don't put solder mask over the traces and order the board finish as HASL (hot air solder leveling). The extra solder over the traces will beef it up even more.

-Rick

i_ionut
Posts: 3
Joined: 30 Apr 2015, 11:21

Re: Voltage and Amps Over Traces and Pours

#5 Post by i_ionut » 10 Jun 2020, 05:57

A little late, but you can try these tricks:

- For amperage you can choose not to have traces masked. In PCB draw a filled shape over traces and put it on Top/Bottom Mask layers, depending on which layer you work. Check with 3D Viewer that you have clean traces, with no solder mask on them. When you get your PCBs from the manufacturer put a lot of solder alloy on them, like you solder the components. This will increase the amperage supported by trace. It is not a scientifically accurate method, but a rule of thumb used by many electronics manufacturers.
- For voltage you can increase the distance between traces (clearance). If it's not possible, you can add cuts in your board to gain extra space (creepage). Google have some nice images about this method. For a standard FR4 1.6 mm PCB you can get up to 3.2 mm of electrical path.

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