IPC-4761 (Design Guide for Protection of Printed Board Via Structures) defines several types of methods for protecting PCB vias. These are:
- Type I: Tented
- Dry film solder mask is stretched over the hole. No other materials are added.
- Type II: Tented and covered
- An additional dry film or liquid solder mask layer covers the tenting of a Type I tented via.
- Type III: Plugged
- A non-conductive material penetrates partially into the hole, but does not go all the way through.
- Type IV: Plugged and covered
- An additional dry film or liquid solder mask layer covers the plugging of a Type III plugged via.
- Type V: Filled
- A conductive or non-conductive material penetrates completely into the hole, filling the hole all the way through.
- Type VI: Filled and covered
- An additional dry film or liquid solder mask layer covers the filled material of a Type V filled via.
- Type VII: Filled and capped
- A metalized coating covers the filled material of a Type V filled via.
In general, production costs increase as you go down the list, with type III being more expensive than type I, etc.
Additional info:
- IPC-4761: Via Plugging Guideline by Yash Sutariya, Saturn Electronics
- Via Tenting, Plugging, and Filling by PCB Universe
- Filled, Plugged, Plated Via-In-Pad by John Steinar Johnsen, Elmatica
