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I have a four layer board. The stack is divided as follows: Layer 1: Signal Layer 2: GND Layer 3: Power Layer 4: Signal

I have SMD components such as an SMD fuse, but the Power layer is in Layer 3.

What is the best way to properly achieve this connection?

Do I need to place a copper polygon pour on Layer 1 as well as Layer 3 and then connect them using vias?

Or because it is a small connection I can get away with just using a top copper pour?

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  • \$\begingroup\$ Using a via - they take signals through the board. \$\endgroup\$ – Tom Carpenter Oct 11 '18 at 10:00
  • \$\begingroup\$ So two copper pours, one on Layer 1 and the other one on Layer 3 and then using via's to connect them? \$\endgroup\$ – ll ll Oct 11 '18 at 10:02
  • \$\begingroup\$ Copper pours or traces. You can use multiple vias if you want more current handling capacity. \$\endgroup\$ – Tom Carpenter Oct 11 '18 at 10:21
  • \$\begingroup\$ But can I then use a normal via that connects Layer 1 all the way to Layer 4 and then use only copper pours on Layer 1 and Layer 3, will that leave Layer 2 and Layer 4 alone (because now I don't have the option to place a Blind Via)? \$\endgroup\$ – ll ll Oct 11 '18 at 11:00
  • \$\begingroup\$ Correct. In eagle a 1-4 via allows connection to all layers. However it will only connect to planes belonging to its own signal. Planes on the inner layers will behave just like planes on the outer layers - they will avoid anything that they are not on the same net as. \$\endgroup\$ – Tom Carpenter Oct 11 '18 at 11:03
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To connect between top layer and inner layers, you need to use vias - these are basically plated holes that can take signals through the board.

Connect your component to the vias using copper pours or traces. You can also use multiple vias if you want more current handling capacity.

You don't need specialist vias for this purpose. Vias allows connection to all layers. However they will only connect to copper belonging to their own signal. Planes on the inner layers will behave just like planes on the outer layers - they will avoid anything that they are not on the same net as.

The net result is that as your via goes through the board, there will be no shorts to planes on any layer that is of a different signal. A GND via will for example not connect up to a +5V plane - in fact the plane will cut away to avoid it.

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