I am making a circuit that will allow a load to be configured in this manner:

  1. Load is ON/OFF.
  2. If OFF (controlled by a low-side FET making the circuit OPEN), the high side and low side can be configured to PU, PD, open, or to external load (external load connects outside of original circuit through banana jacks by connecting to High Side and Low side).

I should add that the MOSFET switching issues (flyback etc.) are not such an issue as this is to configure to a particular setting before power is introduced to the system. If it needs to be changed, the system will be removed from power and then the switches will be actuated.

enter image description here

This circuit is specified to see 16A at 85V (although it is possible for this current to exceed this if someone is to incorrectly configure the driver so I considered a fuse on the HS, say 20-30A fuse).

I have no experience designing a custom PCB and thought to just buy one and solder myself, something like this https://www.mouser.com/datasheet/2/58/BPS-DAT-(BR1)-Datasheet-932653.pdf.

My concern from using the online PCB trace calculator estimates that the trace should be 10.8mm. I don't believe the copper traces are that big on these PCBs, so do I make the solder joints to the board 10.8mm? Won't that short to other parts of the PCB at that width?

enter image description here

I guess my question boils down to implementation on the PCB. I will use traces as little as possible and instead shorten the trace and use wire as much a possible, but not really sure if I am overlooking things or not in regards to the PCB.

  • \$\begingroup\$ Sometimes you don't want to use a PCB at all. \$\endgroup\$ Commented May 18, 2018 at 17:44
  • \$\begingroup\$ use parallel traces then and heavily tin those traces. I have use stripboard to carry 30A before without issue \$\endgroup\$
    – user16222
    Commented May 18, 2018 at 17:52
  • \$\begingroup\$ So what make the PU/PD resistor network and rails on a PCB and connect the fet and load circuit by just wires? S \$\endgroup\$ Commented May 18, 2018 at 17:52
  • \$\begingroup\$ oh, so connect the voltage to two rails to distribute the current across a parallel rails? Then connect those to the load? \$\endgroup\$ Commented May 18, 2018 at 17:54
  • \$\begingroup\$ Make sure that the banana plugs and sockets are rated sufficiently - the ordinary exposed ones are only rated for low voltages so you will need shrouded ones such as multimeters tend to use nowadays. \$\endgroup\$ Commented May 18, 2018 at 18:00

2 Answers 2


Seeing as you're doing hand assembly, you can solder extra copper to the undersideof the high current tracks.

You can buy tinned wire, or recycle the core from offcuts of solid core mains wiring cable (eg Romex), use the bundle of strands from flex, or even desoldering braind for this.


In this case I recomend you to check it with SATURN PCB. It allows you to simulate a lot of things.

The first topic is the thinkness of copper layer. You are choosing 1-OZ = 35um layer. In your case I would go at least 2 oz. I can provide you some images from what it looks like with 1oz and how it variates with width. 1secong_0.254mm width

Continuous use

100seconds__=.254mm width

And this is what happends when you have 2oz layer


Here you have to take into account that you can route as a poligon and not only on TOP but also on button to decrease the stress.

My recomendation is to go to at least 2-3 oz(this makes it more expensive) and use a wide track / poligon. Also you are calculating that it should always stay at 25°C so that´s also the reason why it gives you these values. It can go up to 40.

There is more things to consider but I think this gives you a new way of working around your problem. Also check that the thickness of inner layer also influences the thermal disipation. Before manufacturing the board you can always consult the manufacturer, they usually give a lot of recomendations.

This is the last simulation in conductor properties with 4oz base copper, you can check it: Conductor Properties


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