EMI Coating

Introduction to EMI Coating?

Electronic equipment emits a certain degree of electromagnetic radiation. EMI shielding countermeasures are often used to suppress the emission of these electromagnetic noises to the outside of the electronic equipment. Different shielding materials have different shielding effects on noise of different frequencies. The following figure describes a shielding effect of several common materials.

Figure 1 Shielding effect of several common materials

EMI Shielding Type

There are two types of front EMI shielding:

Transparent Conductive Coating, often used for products with high light transmittance
EMI Mesh, have better shielding

Table 1 EMI shielding comparison

	Transparent Conductive Coating	EMI Mesh
Sheet Resistance	5~10 ohm/sq	<1 ohm/sq
Transmissivity	80%-90%	70%-80%
Attenuation	20~40db	30~60db
Effective Attenuation Range (MHz)	20-1000	10-10000
-	Good optical properties	Moderate optical properties
-	Low to moderate EMI shielding	Excellent EMI shielding

Transparent Conductive Coating

The most common transparent conductive coating is ITO (indium tin oxide) coating. This is an ideal choice when the display requires high-quality optical properties. The light transmittance can reach 80-90%. The most commonly used method is Coated Glass and Coated Film. Coated Glass directly coats the ITO coating on the glass of the display or touch screen. Coated Film coats the ITO coating on a PET film. When applied, the coated film is attached to the object to be shielded.

ITO Coated Glass

High quality conductive coating on glass for EMI/ RF shielding.

Specifications

Vacuum deposited ITO (indium tin oxide) coating index matched to specification are offered in various levels
ITO coatings on glass offer high quality optical properties and optical shielding effectiveness
ITO coatings glass is offered as a laminated filter or single pane glass
Additional coating such as anti-reflection and anti-glare are also available
Levels of ITO offered on glass are as follows: ≥ 5 ohms/sq

ITO Coated Films (Transparent Conductive Films)

Multi-layer transparent conductive coatings on flexible PET film.

ITO Coated Glass

Specifications

High visible transmission with low resistance
Reduce EMI/ IR from display surface
Film can be laminated to touch screens, glass or acrylic
Levels of ITO/ EMI shielding film offered: ≥ 8-10 ohms/sq

EMI Mesh

ITO Coated Glass

EMI Mesh provides excellent EMI shielding. Typical EMI mesh is woven into a matrix pattern from stainless steel wire or copper wire. The matrix density is in units of OPI (Openings per inch). For example, 60 OPI means there are 60 openings per inch. The smaller the OPI value, the better the EMI shielding effect.

Wire Mesh EMI Shielding

Wire mesh EMI shielding is used for optical shielding of electronic displays.

Specifications

Wire mesh is ≥ 1 ohms/sq
80 or 100 opi 9openings per inch)
Stainless steel or copper base
Stainless steel wire diameter - .0012” (31 μm)
Copper wire diameter - .0022” (56 μm)
Mesh can be laminated in between optical substrates or to rear surface of touch screen
Mesh can be applied to metal frames secured with gasket material

Application EMI Mesh

Winmate can apply EMI mesh coating to its display by request. Most common application is for military product line.