Via Filling is a technique that guarantees completely closed via holes.

Via Filling with Resin

The vias to be filled are filled with a special hole plugging resin, TAIYO THP-100 DX1 thermally curable permanent hole filling material, using a dedicated machine, ITC THP 30. The extra production steps needed, are performed before the 2-layer PCB production process. In case of making multi layers, this is after pressing.

Picture2Overview of the extra processes:

  • Drilling of only the vias that need filling
  • 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, this Via Filling type with Resin process ALWAYS results in a “Type VII – Filled and Capped” via.

Note: This Via Filling with Resin type is suitable for Via-in-Pad application.

Technical specifications

Via Filling with Resin
ToolSize / EndSize (mm)Min0.20 / 0.10
Max0.60 / 0.50
Material Thickness (mm)Min1.00
Outer StartCopper Thickness (µm)Min12
UL certificationNo
IPC-4761 via protection typeVII – Filled and Capped
Via-in-Pad applicationYes
  • ONLY PTH holes (PTH hole = hole with copper pad on TOP and BOT side).
  • ONLY through hole vias, so Blind vias can NOT have Via Filling.

Important parameters are resin content, aspect ratio of the hole and the thickness of the core involved.  A complete filling can’t be guaranteed.

Avoid naming confusion between Via Filling and Via Plugging

The IPC-4761 via protection type classification, clearly defines the difference between

Filling ill_printplaten-05 and Plugging ill_printplaten-07 ill_printplaten-08

In our manufacturing processes we only use Via Filling as it has considerable advantages over Via Plugging.

Below is a short video explaining the process.

See also:

PCB Design Guidelines – Via Filling