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I am in process of hiring a freelancer to develop a PCB which will incorporate Wiznet W5500 ethernet IC. Some have suggested a 4 layer PCB, but some are saying it is possible in 2 layers. As the board has many buffer IC's and other connectors which don't require 4 layers. I am skeptical to take this decision and need help.

Please advice. Thanks!

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  • \$\begingroup\$ If you are hiring a PCB freelancer, do you not trust their decision on how many layers they believe are necessary for a clean design with suitable signal integrity? \$\endgroup\$ – nanofarad Jul 26 '20 at 17:20
  • \$\begingroup\$ 50 % have the opposite opinion sadly \$\endgroup\$ – Sap Jul 26 '20 at 17:21
  • \$\begingroup\$ Have you asked them to briefly justify their decision? It's perfectly possible that our community here will also be split on two and four layers, depending on our individual experiences and preferred practices. \$\endgroup\$ – nanofarad Jul 26 '20 at 17:22
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    \$\begingroup\$ 4 layers in all probability will be a quieter board, with proper ground/power planes. This can improve reliability and lead to a working product faster. Consider how many you are making : volume has to be pretty high to justify spending more time getting the 2 layer design working right if you aren't lucky first time. \$\endgroup\$ – user_1818839 Jul 26 '20 at 18:41
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    \$\begingroup\$ In 2020, the cost difference for a 4-layer board is 100% worth it to allow for a solid ground plane (yielding much better EMI/EMC properties), unless you plan to make tens of thousands of these things, and even then, it might not be justified, imho. I mean not everything needs to be 4-layers, but when I have any doubts these days, I can usually justify it to myself. \$\endgroup\$ – vicatcu Jul 26 '20 at 18:52
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You may be able to make a board smaller in 4-layer so the square inches may compensate somewhat. 4 layer has dropped quite a bit in price in the last couple years, price starts to tick up considerably at 6 or more.

That said, 2 layer looks do-able. There was a layout here some time ago which has a number of examples of what not to do (pours are not great, power lines don't look great, crystals are very poorly and unnecessarily placed in relation to other lines). Make sure that the freelancer follows the hardware guide.

Personally, I would go for 4-layer unless I had a lot of confidence in the designer and budgeted enough of their time to take care with signal and power integrity (assuming they know how to do that in the first place). On the other hand, a novice following the guide would likely not have any issues with a reasonable 4-layer or more layout. I've seen some pretty slapdash subcontractors purveying their work online.

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    \$\begingroup\$ Thank you for your help! \$\endgroup\$ – Sap Jul 27 '20 at 9:00

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