What is Via Filling?

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..

Overview 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

Cross section of a via hole filled with resin

Filled and capped via hole

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) Min 0.20 / 0.10
Max 0.60 / 0.50
Material Thickness (mm) Min 1.00
Max 2.40
Outer StartCopper Thickness (µm) Min 12
Max NA
UL certification No
IPC-4761 via protection type VII – Filled and Capped
Via-in-Pad application Yes
  • 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
  • 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

Via fill graphic
Filling
Via plugging top graphic
Plugging
Via plugging top and bottom graphic
Plugging

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