This coating is also called EMI (electromagnetic interference) shielding paint.

This coating uses an electrically-conductive coating as the main ingredient, which prevents electromagnetic interference and provides EMC (electromagnetic compatibility).

A bandwidth between 10 kHz and 500 MHz of electromagnetic waves is particularly important to information technology devices. Since the 1980s, the United States and Germany have strengthened the EMI regulations on digital devices.

One of the reasons for this is the trend of adopting plastic materials for the equipment casing.

Plastic materials are the major choice for digital equipment casing because they are not only lightweight and economical but also have superior productivity, design, and electric insulation.

However, their electrical insulating properties incapable of providing the shielding effect for electromagnetic waves drove the industry to tighten the regulations.

The EMI regulations define the category based on the application: "Class A" for industrial and commercial equipment; "Class B" for residential applications.

In addition, noises generated from these are classified as "conductive noises", which are transmitted from power/signal cables of the equipment and "radiation noises", which are emitted directly from the internal component of the equipment into space.

The source of electromagnetic wave generation is shown in [Table 1].

[Table 1] Source of electromagnetic wave generation

In order to shield electromagnetic waves, apply the electrically-conductive coatings.

The paints are available in Ag, Ni, Ag-Cu, and Cu formulas. All of these are suitable for plastics as they are a low-temperature curing type.

Thermoplastic acrylic, thermosetting acrylic, epoxy, and phenol resins are used for the binders.

The properties of the coatings are shown in [Table 2].

[Table 2] Electrical properties of the electromagnetic shielding paints