Via Filling is the process where the barrel of the Via Hole is filled with resin and is the only way to guaranteed the Via Holes are sealed.

How to Provide Data for Via Filling

  • All Via Holes are Plated Through Holes and are defined by default as a hole that is <=0.45mm (18mil) in diameter.
  • If you have component lead or mounting holes of 0.45 mm or smaller, please ensure that you clearly identify that they are plated holes and NOT via holes in our Drill editor.
All Via Holes must be Filled

If all via holes are to be filled, then the data can be sent as normal in one of the Data Input Formats we can accept and selecting the via filling option in our Advanced options of PCB Configurator.

Specific Via Holes must be Filled

If you have specific via holes that must be filled there are different ways in which you can provide this information as detailed below.

Remember to select the via filling option in our Advanced options of PCB Configurator.

Separate Data File/layer (preferred option)

Provide a specific data file that contains only the vias holes that are to be filled and use an appropriate file name (e.g., Via Filling). Alternatively, if you are supply a native CAD file (Eagle/KiCAD) it can also be a specific or an already existing layer in the design file.

Manually Identify Vias Holes to be Filled in the Drill Editor

Use the Drill editor to manually select the via holes that are to be filled and identify them as Via Filled.

Filling with Resin

The Via Holes are filled with a special plugging resin.

We use the  TAIYO THP-100 DX1 thermally curable permanent hole filling material.

This resin is applied using a dedicated machine the ITC THP 30.

Additional process are required for resin filling and these must be performed before the normal PCB production can begin.

In case of making multi layers the inner layers are produced and bonded together before the filling process.

Cross Section of Filled ViaOverview of the extra process steps:

  • Drilling of only the vias that need plugging.
  • Cleaning: plasma and brushing.
  • Black Hole.
  • Apply dry resist.
  • Imaging of ONLY the via holes.
  • Via hole galvanization (PTH).
  • Strip dry resist.
  • Brushing if needed.
  • Baking: 150°C for 1 hour.
  • Via plugging with resin.
  • Baking: 150°C for 1.5 hours.
  • Brushing.

After these steps the normal PCB production process starts or continues: drilling of the other PTH holes, and the normal outer layer production processes.

Using the IPC-4761 via protection type classification, Via Holes filled with Resin will always results in a “Type VII – Filled and Capped” Via Holes as shown below.

Via Filled and Capped


The type Resin we use is suitable for Via-in-Pad application.

Technical Specifications

Filling with Resin
TOOLSIZE / ENDSIZE (mm)Min0.20 / 0.10
Max0.60 / 0.50
Material Thickness (mm)Min1.00
Outer Start Copper Thickness (µm)Min12
UL CertificationNo
IPC-4761 Via Protection typeVII – Filled and Capped
Via-in-Pad ApplicationYes
  • ONLY PTH holes can be filled (PTH hole = hole with copper pad on TOP and BOT side).
  • ONLY through hole vias can be filled, so Blind Via Holes can NOT be filled.

Important parameters are resin content, aspect ratio of the hole and the thickness of the core involved.

In compliance with the IPC-A-600 and IPC-6012 class 2, holes that require Via Filling must have a minimum of 60% of the hole volume filled.

Avoid Confusion

The IPC-4761 via protection type classification, clearly defines the difference between Filling and Plugging.


Via Filling


  Via Plugging Via Plugging

In our manufacturing processes we only use Filling as it has considerably more advantages than Plugging.

Page Update History

17/03/2020 – Changed – Minimum Start Copper for Via Filling with resin.

03/07/2020 – Via Filling with Soldermask discontinued July 2020.

28/03/2022 – Update on how to provide data.

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