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The Altium Designer has schematic symbol library and PCB footprint library. I understand both of these. However, there is a third one called pad via library.

Pad is the exposed copper on PCB where a component is soldered. It could be a SMT pad or a through hole pad. Via on the other hand is a hole in the PCB whereby a PCB track can go from one layer to another.

That is all there is to know about pad and via isn't it? Then why would anyone need to create a library of these? This is new to me.

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Here (from here) is an illustration of several types of vias used in HDI (high density interconnect) boards, including the simple through hole via you mention:

enter image description here

From an Altium video:

enter image description here

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  • \$\begingroup\$ I am truly in state of shock after seeing this, how do people actually know what sort of via is required? \$\endgroup\$
    – quantum231
    Apr 2, 2022 at 15:59
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    \$\begingroup\$ If you have a not-very-dense 2 or 4 etc. layer board you can use all through-hole vias, but as the density goes up and requiring fine-pitch BGAs, controlled impedance, double side parts etc. you need lots of layers. Through hole vias use too much space- they take up space on every layer and on both sides. The more complicated the buried and blind vias the more operations are required so the cost goes up and up. Similarly lasered microvias and plugged vias cost more (all other things being equal). \$\endgroup\$
    – Spehro Pefhany
    Apr 2, 2022 at 16:48
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Pads and vias can be much more complicated than just a hole and pad diameter. Rounded rectangles, slots, buried and blind vias, tolerance specifications, and tweaks to soldermask and solder paste expansion all can be saved as templates or library elements.

If you only ever need very basic pads with rule-defined expansions, then the library and template are probably of little value. But if you work with unusual clearances, constraints, or components, you may find it helpful to be able to refer back to "that weird pad we created for the flexible polyimide antenna..."

More info on how to use the pad and via library and templates can be found on the official Altium documentation page.

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