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

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 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 and 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.