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I am currently routing a 4 layer PCB and I was wondering how I connect the ground and power planes to the connector and components that need them. Do I simply leave the two planes without routing on them? If so how can a connection be created between those planes and the components.

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  • \$\begingroup\$ How you connect the planes to the connectors depends entirely on the connectors, and what protection you need to give the power and ground nets from the outside world. \$\endgroup\$ – Matt Young Dec 17 '14 at 20:57
  • \$\begingroup\$ Well first off we need to know what PCB software you're using. \$\endgroup\$ – Funkyguy Dec 22 '14 at 3:51
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Use a via.

Presumably the power planes are internal. Use a via to connect from the signal planes (top and bottom) to the internal power or ground plane. The via can be completely through the board but only connected to the starting trace and the plane you want.

Depending on your software you'll probably just need to be routing a signal of the same name as the power plane and once you make the via, it will connect automatically.

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    \$\begingroup\$ And note that not all PCB houses are capable of creating blind vias, so you may need to put them through the whole board regardless. \$\endgroup\$ – Ignacio Vazquez-Abrams Dec 17 '14 at 21:06
  • \$\begingroup\$ I'm using PADS.I'm not sure I completely understand what you mean. So should I route a small trace from the signal planes and end them as vias to the power/ground plane? \$\endgroup\$ – Mega Dec 17 '14 at 21:08
  • \$\begingroup\$ @IgnacioVazquez-Abrams True, also, if they are offered then they almost always cost extra. \$\endgroup\$ – Samuel Dec 17 '14 at 21:09
  • \$\begingroup\$ @Mega I haven't used PADS for almost two years, but I believe you can just start drawing a trace from the signal layer, then shift-click to manually place a via. The router should recognize that you're done at that point, since you have reached electrical connectivity with the power plane. \$\endgroup\$ – Samuel Dec 17 '14 at 21:11
  • \$\begingroup\$ @Samuel okay thanks. This totally helps me make sense of my connections. \$\endgroup\$ – Mega Dec 17 '14 at 23:14
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Connection to a ground plane is done through a via. In case of surface-mount component, there is separate via connected to the surface-mount pad. In case of throughole component (pictured below), the pin is soldered into the via.

enter image description here
Notice that in this case, ground plane is connected to the via. Vcc plane has an annular clearance around the via, and so it's not connected to the via.

enter image description here
When soldering throughole components, a plane can act a heat sink. That makes soldering more difficult. Thermal relief pattern makes soldering of plane-connected pins easier.

(Source of drawings: Nick's introduction to PCB design workshop.)

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  • \$\begingroup\$ Nice diagrams :) \$\endgroup\$ – Some Hardware Guy Dec 17 '14 at 21:32
  • \$\begingroup\$ @SomeHardwareGuy Thank you. I owe the quality of illustrations to SolidWorks. \$\endgroup\$ – Nick Alexeev Dec 17 '14 at 21:34
  • \$\begingroup\$ Your self promotion is shameless. \$\endgroup\$ – Samuel Dec 17 '14 at 23:01
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For through-hole components, pins connected to the Vcc or GND nets will be automatically connected to the power or ground planes as needed - the planes will have no clearance around the hole, so will connect to the through-hole plating.

For SMD components, connect the ground or power leads to short traces. A via placed on those traces should automatically connect to the appropriate plane.

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  • \$\begingroup\$ Okay, so when using through whole component, pins connected to the ground/power should just be traced to the ground/power connector on the bottom or top layer? \$\endgroup\$ – Mega Dec 17 '14 at 21:25
  • \$\begingroup\$ BTW I'm using PADS and and the signal layers are top and bottom. \$\endgroup\$ – Mega Dec 17 '14 at 21:28
  • \$\begingroup\$ On through-hole components, if the schematic shows the pins connected to power or ground, the PCB program will automatically connect those pins to the appropriate plane - no need to do any routing. (This is based on my experience with Protel/Altium and KiCAD, but I would expect other programs to do the same.) \$\endgroup\$ – Peter Bennett Dec 17 '14 at 23:34
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If you put a big copper plane for ground on layer 2 and another one for power on 3 and assign them to the ground and power nets respectively, PADS will automatically connect them when you flood the copper. All of the through holes will get connected using the copper "spokes" for thermal relief. The SMD pads on the top (and possibly bottom) layers would need additional vias.

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  • \$\begingroup\$ How about routing the pins to the ground and power connector. Do I simply route them on either the bottom or top layer (signal layer) and add a via to the connector? \$\endgroup\$ – Mega Dec 17 '14 at 23:13

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