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I was wondering if someone can give me advice in routing this PCB.

enter image description here

The PCB contains several triacs driving AC loads and digital end which contains a micro and several digital I/Os. So far, I have decided on the following:

  • Use 18 AWG wire to connect the LIVE via the spade terminals.
  • Use 5oz copper on the top layer to reduce the track width for the high current tracks for triac output to AC load spade terminal.
  • Solder Y caps underneath the board with insulation and hot melt glue.
  • Use 4 layers
  • First layer contains AC tracks on the mains side and DC signal tracks on the digital side.
  • Second layer contains ground layer on the digital side with some signals.
  • Third layer contains digital VCC layer on the digital side with some signals.
  • Fourth layer contains signals on digital and secondary voltage from the transformer.

I have few constraints in the design like the placements of the headers and AC spade terminals cannot be modified plus the board size cannot be changed. I have placed the heatsink/triacs and spade terminals so I can route the signal tracks to the optocouplers and secondary output of the transformer via the middle of the PCB. I am trying to ensure there is a least 2.5mm separation for the AC tracks.

Do anyone see any issues or problems with this layout or have any suggestions?

Regards Paul

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  • \$\begingroup\$ I am going to route the AC side on the bottom layer so I can route the digital side on the top layer. \$\endgroup\$
    – Paul
    Oct 13, 2013 at 1:41
  • \$\begingroup\$ How big these currents are? Actually I am not sure you need 4 layers in this PCB. \$\endgroup\$
    – johnfound
    Oct 13, 2013 at 6:15
  • \$\begingroup\$ 15A 230V. The main reason why I chose four layers is to be able to route the optocouplers input/ground and secondary output of the transformer to the digital part of the circuit. \$\endgroup\$
    – Paul
    Oct 13, 2013 at 10:40
  • \$\begingroup\$ The dimension of the board is 240mm x 30mm as an additional information. I have routed the 4 layer board and asked the PCB manufacturer for a quote to see how much it will cost. \$\endgroup\$
    – Paul
    Oct 13, 2013 at 10:42
  • \$\begingroup\$ Related: This excellent reference - TI Analog Engineer’s Pocket Reference - 4th edition provides some useful information on PCB track current/ voltage drop / heat / fusing issues. Especially pages 55-68. \$\endgroup\$
    – Russell McMahon ♦
    May 5, 2016 at 5:31

1 Answer 1

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On 15A/230V you need 2mm track width and 2mm of clearances (5Oz/ft2 Cu and 20*C temperature rise).

Although, IMO, using 0.2mm copper PCB is pretty over engineered. The same results can be reached with more careful trace design.

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  • \$\begingroup\$ You are probably right. Just by looking at the PCB, I notice I can shift one of my spade terminals and reducing the track length. I could also use both top and bottom layers to route the high current tracks. \$\endgroup\$
    – Paul
    Oct 13, 2013 at 11:10
  • \$\begingroup\$ Reduced it down to two layers. Just finding a way to supply the current. \$\endgroup\$
    – Paul
    Oct 13, 2013 at 11:44
  • \$\begingroup\$ Ok got it down to 2oz of copper and two layers now. This will be a significant drop in cost for the manufactured board. \$\endgroup\$
    – Paul
    Oct 13, 2013 at 12:08
  • \$\begingroup\$ @user468662 Good work. Now it sounds as a reasonable design. :) \$\endgroup\$
    – johnfound
    Oct 13, 2013 at 12:20

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