CHOOSING THE APPROPRIATE VIA FILLING/PLUGGING TYPE FOR YOUR PCB

By Sam liu

PCB Surface Finish Explained

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 Desing 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 Plugged and Covered Via Type IV-b Plugged and Covered
              – Double-Sided PCB Plugging material:LPI solder mask or Resin Covering material: LPI solder mask Recommended
Filled Via Type V Filled (fully plugged)  Filled Via Filled (fully plugged) PCB Filling material: Conductive or non-conductive material Recommended
Filled and Covered Via Type VI-a Filled and Covered – Single-Sided Filled and Covered Via Type VI-a Filled and Covered
              – Single-Sided PCB Filled and Covered Via Type VI-a Filled and Covered
                 – Single-Sided PCB Filling material:Conductive or non-conductive material Covered material: Dry film mask or LPI solder mask Recommended
Filled and Covered Via Type VI-b Filled and Covered Double-sided Filled and Covered Via Type VI-b Filled and Covered
              Double-sidedPCB Filled and Covered Via Type VI-b Filled and Covered
                 Double-sided PCB Filling material:Conductive or non-conductive material Covered material: Dry film mask or LPI solder mask Recommended
Filled and Capped Via Type VII Filled and Capped Filled and Covered Via Type VI-b Filled and Covered
           Double-sided PCB Filled and Covered Via Type VI-b Filled and Covered
              Double-sided PCB Filling material: Conductive or non-conductive material Capped: a secondary metallized coating Recommended

Not Recommmended Via Types Protection

Via Protections Definitions Type Description Figure-IPC-4761 Material Fineline Recommendation
Tented Via Type I-a Tented - Single-Sided Tented Via Type I-a Single-Sided PCB Tenting material: Dry film mask Not Recommended
Long-term reliability risk.
Tented Via Type I-b Tented - Double-Sided Tented Via Type I-b Double-Sided PCB 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 PCB Tented and Covered – Single-Sided Not Recommended Long-term reliability risk.
Tented and Covered Via Type II-b Tented and Covered – Double-Sided (IIb) Tented and Covered –
                        Double-Sided (IIb) PCB enting material: Dry film mask Covering material: LPI Solder mask Not Recommended Dimples may be a concern.
Plugged Via Type III-a Plugged – Single Sided Plugged Via Type III-a Plugged – Single Sided PCB Plugging material: LPI solder mask or Resin Not Recommended Long-term reliability risk.
Plugged Via Type III-b Plugged - Double Sided Plugged Via Type III-b Plugged – Double Sided PCB 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 Plugged and Covered Via Type IV-a Plugged and Covered
                     – Single-Sided PCB Plugging material:LPI solder mask or Resin Covering material: LPI solder mask Not Recommended Long-term reliability risk.
Fineline Via Filling/Plugging Table Recommended
Fineline Global Via Filling/Plugging Not Recommended

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