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I am trying to create the best PCB possible for my DC Motor controller. I have been looking into the different ways to make my vias for my PCB and I am a little confused on the topic of tenting and plugging and conductivity between the bottom and top layers. The general idea behind the two are:

Tenting - Apply solder mask over the via to decrease exposure to external conductors, cleaner looking but from what I'm reading it does not work for large drills.

Tenting

Plugging - Vias are entirely filled with a non-conductive material. This ensures 100% of the via is filled so as no complications with tenting can happen, used for larger drills.

Plugging

Now one thing I am not understanding is doesn't there need to be a wire that is fed through the via and soldered so as to create a conductive path between the bottom and top layers? If so wouldn't tenting/plugging ensure that no wire can be fed through the via as to create a conductive path. The way I see it, in this case, the via would be a useless hole.

Does the annular ring that feeds between the two layers give enough conductance between the two layers? How is the conductive path between the two layers established in these examples?

When would you use one versus the other? Does it have to do with the size of the drill or are there external factors that must also be considered?

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doesn't there need to be a wire that is fed through the via and soldered so as to create a conductive path between the bottom and top layers?

In professionally made boards, there's no wire passed through the hole. Instead, copper is electroplated onto the sides of the hole to make the connection.

The diagram you shared shows the plating has been done, leaving a copper connection through the board:

enter image description here

The plating process is done before solder mask is applied to the outer layers of the board, so the connection is already made before the tenting and/or plugging is done.

Does it have to do with the size of the drill or are there external factors that must also be considered?

Tenting without plugging is not recommended for large hole sizes, because the air trapped in the hole will expand if the board is heated (for example, when soldering parts to the board), breaking the tenting.

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  • \$\begingroup\$ I am using OSHPark, the original board I have created has vias not covered. There is a straight hole through the board. The copper that is connected to the annular rings and fed through is enough conductance in this situation? No pins/wires are needed to be used to fill this hole? If this is the case why are vias not always plugged? \$\endgroup\$
    – Grant
    Commented Feb 22, 2020 at 3:28
  • \$\begingroup\$ @Grant, you can calculate the resistance of the connection from the thickness of the copper (typically ~25 um), the circumference of the hole, and the length of the hole (typically 1.6 mm). The voltage drop across the hole then depends on the current you're passing through it. If you need to reduce the resistance of the hole, it's easier to make a bigger hole (with greater circumference) or connect multiple holes in parallel than to solder wire into the hole. \$\endgroup\$
    – The Photon
    Commented Feb 22, 2020 at 3:32
  • \$\begingroup\$ Makes sense. Wider hole, smaller current density, and less joule heating. But that dosent explain why vias are not always plugged? Is it a higher cost and only done on request? What is the treshold for tenting drill size also? Is there an industry standard on when to one versus the other? \$\endgroup\$
    – Grant
    Commented Feb 22, 2020 at 3:57
  • \$\begingroup\$ Yes, it costs extra. I usually only tent 0.2 mm holes, but I'm not sure what the vendors recommend. I would just leave the holes untented rather than pay for plugging. \$\endgroup\$
    – The Photon
    Commented Feb 22, 2020 at 3:59
  • \$\begingroup\$ Appreciate the help \$\endgroup\$
    – Grant
    Commented Feb 22, 2020 at 4:16

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