7 different types of PCB via filling

Via filling is something that can be very important for your PCB, but a lot of times the designer doesn’t really know all the available via filling types and which type to specify. Only specifying that the vias must be ‘filled’ or ‘plugged’ is something we do not recommend. This makes it not only confusing for the designer, but also for the manufacturer.
Instead of only specifying ‘filled’ or ‘plugged’ we recommend to specify a certain IPC-4761 via type. These types make it easy to understand for both the designer and the manufacturer and therefore you know what to expect from your vias. The IPC-4761 only specifies via types for mechanically drilled vias, but not for microvias which are laser drilled. Microvias will always be copper filled if these are placed in the pad of a component or if another microvia is stack on top of it. 

IPC-4761 specifies 7 different types of vias:

1.Tended (Via Type I-a/-b) 

The via is completely covered with  dryfilm solder-stop.

One-sided: Type I-a

Double-sided:Type I-b

2.Tented and covered (Via type II-a/-b)
The via is completely covered with  dryfilm solder-stop and overprinted with normal solder-stop, afterwards.

One-sided: Type II-a

Double-sided:Type II-b

3.Plugged (Via Type III-a/-b) 

A via or through hole with material applied allowing partial penetration into the via or through hole. The plug material may be applied from either one or both sides of the via structure. (Prior to surface finish.)

One-sided: Type III-a

Double-sided: Type III-b

4.Plugging and covered (Via Type IV-a/-b)

A via or through hole with a secondary covering of mask material applied over the plugged via. The material may be applied from either one or both sideso f the via structure. (Prior to surface finish.)

One-sided: Type IV-a

Double-sided: Type IV-b

HopetimePCB recommends one-sided plugging (Type III-a / Type IV-a) as there is a chance of cracks through encapsulated gas while soldering double-sided plugged vias

5.Filled (Via Type V)

A via or through hole with material applied into the via or through hole targeting a full penetration and encapsulation of the hole. (Prior to surface finish.)

The via is filled completely with non-conductive paste.  

6.Filled and covered (Via Type VI)

A via or through hole with a secondary covering of material applied over the filled via or through hole. The material may be applied from either one or both sides of the via structure. (Prior to surface finish.)

One-sided: Type VI-a

Double-sided: Type VI-b

7.Filled and capped (Via Type VII) 

A via or through hole with a secondary metallized coating covering the via or through hole. The material may be applied from either one or both sides of the via structure. (Prior to surface finish.)

Filled & Capped Vias are also possible for Blind vias. 

‘For tented and plugged via types “-a” stands for single sided and “-b” stands for both sides of application.
A type I via is tented during the soldermask process. The downside is that the manufacturer cannot guarantee that the hole is 100% closed. As you can see in the picture on the right, there’s a chance of exposed copper. If you specify this via type, please tent the vias from both sides instead of only one side.

Type III and IV can be specified if you want an inexpensive solution to close the via hole 100%. The via will be plugged from one or both sides.A Type V or VI vias will be filled with a substance which is normally soldermask or epoxy. IPC does not give a requirement in terms of depth of fill. 

Nowadays the price is more important than ever. It is therefore important to specify the right IPC-4761 type.Before specifying it, please ask yourself what you require from the via. Do I need to place the through hole via inside a pad? Do I only require the via to be closed 100%? What’s the size of the via and is it actually too large to be filled?

Additional information:

--Press-fit technology

--Blind & Buried vias

--Drills &Throughplating