270

Ultra-low Profile Dome Key

B3D

Structure

■ Matrix Adhesive

The surface structure of this adhesive has grid-shaped slits, as

shown in the following cross-sectional diagram. These slits provide

both ventilation and dust-proofing, which is required for contact dome

operation.

■ Circular Contact

When contact dome keys are attached to the PCB, any PCB dust or

foreign particles will tend to collect in the center of the key when it is

pressed. Therefore, poor contact occurs easily in keys that provide

contact at the center point only.

The circular contact construction provides contact along the circumference of

a circle, thus preventing poor contact by avoiding the center point.

Recommended Contact Form

PET film (white)

(with matrix adhesive)

Polyurethane

rubber film (with adhesive)

Stainless steel

contact dome

(circular contact)

15

µm

Slits

Matrix (acrylic)

adhesive: 25

µm

Cover film

Cylindrical protrusion

Contact along

circle circumference

(circular contact)

Contact at center point

Conventional models

Contact dome resistant to

foreign matter (circular contact)

4 mm Diameter Contact Dome (B3D-4112)

Resist (30 to 50

µm)

2.8 dia.

1.8 dia.

5.2 dia.

Gold-plated nickel

2.0

1.2

0.4

2.8 dia.

1.8 dia.

5.2 dia.

Gold-plated nickel

Single-side PCB

Multilayer PCB

5 mm Diameter Contact Dome (B3D-5112)

Resist (30 to 50

µm)

3.8 dia.

2.3 dia.

6.2 dia.

Gold-plated nickel

2.0

1.2

0.4

3.8 dia.

2.3 dia.

6.2 dia.

Gold-plated nickel

Single-side PCB

Multilayer PCB