
Via hole filling/plugging of a PCB is a process where the via hole is filled with solder mask or resin.
Via holes that are filled/plugged improve the PCB reliability by decreasing the possibility of trapped air/liquid in the via, thus ensuring good yield through assembly.
See the table below – Fineline’ s recommendation for via protection according to IPC-4761 via types.
For more information please contact Fineline.
IPC-4761 Design Guide for Protection of Printed Board Via Structures
Via Protections Definitions | Type | Description | Figure-IPC-4761 | Material | Fineline Recommendation | |
---|---|---|---|---|---|---|
Plugged and Covered Via | Type IV-b | Plugged and Covered Double-sided | ![]() |
Plugging material:LPI solder mask or Resin Cover material: LPI solder mask |
Recommended | |
Filled Via | Type V | Filled (fully plugged) | ![]() |
Filling material: Conductive or non-conductive material | Recommended | |
Filled and Covered Via | Type VI-a | Filled and Covered – Single-Sided | ![]() |
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Filling material:Conductive or non-conductive material Cover material: Dry film mask or LPI solder mask |
Recommended |
Filled and Covered Via | Type VI-b | Filled and Covered Double-sided | ![]() |
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Filling material:Conductive or non-conductive material Cover material: Dry film mask or LPI solder mask |
Recommended |
Filled and Capped Via | Type VII | Filled and Capped | ![]() |
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Filling material: Conductive or non-conductive material Capped: a secondary metallized coating |
Recommended |
Non-Recommended Via Protection Types
Via Protections Definitions | Type | Description | Figure-IPC-4761 | Material | Fineline Recommendation | |
---|---|---|---|---|---|---|
Tented Via | Type I-a | Tented - Single-Sided | ![]() |
Tenting material: Dry film mask | Not Recommended Long-term reliability risk. |
|
Tented Via | Type I-b | Tented - Double-Sided | ![]() |
Tenting material: Dry film mask | Not Recommended Dimples may be a concern. |
|
Tented and Covered Via | Type II-a | Tented and Covered – Single-Sided | ![]() |
Tented and Covered – Single-Sided | Not Recommended Long-term reliability risk. | |
Tented and Covered Via | Type II-b | Tented and Covered – Double-Sided (IIb) | ![]() |
Tenting material: Dry film mask Covering material: LPI Solder mask |
Not Recommended Dimples may be a concern. | |
Plugged Via | Type III-a | Plugged – Single Sided | ![]() |
Plugging material: LPI solder mask or Resin | Not Recommended Long-term reliability risk. | |
Plugged Via | Type III-b | Plugged - Double Sided | ![]() |
Plugging material: LPI solder mask or Resin | Not Recommended Solder mask partially covers the annular rings | |
Plugged and Covered Via | Type IV-a | Plugged and Covered – Single-Sided | ![]() |
Plugging material:LPI solder mask or Resin Cover material: LPI solder mask |
Not Recommended Long-term reliability risk. |

