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I have a design which is literally just 2 connectors (input and output), a relay and a diode. Basically using the relay to connect a charger to a battery.

The board size is predetermined and I can't decrease it. It seems like I have plenty of space to comfortably route everything in 1,2 or 4 layers.

The current from input to output could get up to 30A.

Considering board prices between 2 and 4 layer boards is pretty similar these days, is there any reason I should proceed with 2 layers instead of the 4?

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  • \$\begingroup\$ I would normally say no, but your board is more like a breakout board than a circuit so just go two layers. \$\endgroup\$
    – DKNguyen
    Commented May 3, 2022 at 15:45

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Price and lead time is generally less for 2-layer than 4-layer (4 layer probably more than 50% more costly in moderate quantity such as 1K pcs). As far as lead time, for quick turn PCBs from PCBWay, the standard time for 2-layer is 24 hours, and 4-5 days for 4-layer.

In the unlikely eventuality that you need to modify such a simple PCB with cuts and jumpers it will be a lot easier with a 2-layer board. Multilayer boards you might have to drill holes or cut slots to sever internal traces.

Since you have relatively high current you might consider heavier copper like 2oz for the outer layers, which will significantly affect pricing in both cases. More than 1oz or 1.5oz inner copper layers is often non-standard.

Eg. Just one supplier (PCBWay), it may vary signficantly with other suppliers. 100 pieces, 50 x 80mm

2l 1 oz $71

2l 2 oz $92

4l 1oz $160

4l 2oz outside, 1 oz inner $225

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  • \$\begingroup\$ Do you know how heavier copper on a 2 layer would compares to say 1 oz on a 4 layer in price? \$\endgroup\$
    – Hasman404
    Commented May 3, 2022 at 15:54
  • \$\begingroup\$ @Hasman404 See edit above. The 2l 2oz looks like the better option of those 4 with that particular supplier and other assumptions. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented May 3, 2022 at 16:01
  • \$\begingroup\$ As you have only few components to solder on the board with enough space, personally I will go to the 2 layers board with 2oz of copper in this scenario. In case you will be working with RF or you have much components to route or impedance will be a fact, then 4 layers board will be the appropriate. Also have in mind that a 4 layer board with 2oz of copper need a lot of heat to soldering components. \$\endgroup\$
    – marcosbc
    Commented May 3, 2022 at 17:18

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