Technical inspection requirements for membrane switches

The membrane switch is composed of a panel, an upper circuit, an insulating layer and a lower circuit. To touch the normally open switch, the two contacts of the membrane switch are normally disconnected. When an external force is applied to the contact of the membrane switch, the two normally open contacts are connected instantaneously. After the external force disappears, the switch contact will return to the normally open state. Usually, the upper circuit contacts bulge or add pan chips (feel good). Press the membrane switch, the contact of the upper circuit deforms downward and is connected with the electrode plate of the lower circuit. After the finger is released, the contact of the upper circuit bounces back, the circuit is disconnected, and the circuit triggers a signal. Haiwen membrane switch has strict structure, beautiful appearance and good sealing performance. It is damp proof and has a long service life (up to more than 1 million times). It is widely used in electronic communication, electronic measuring instruments, industrial control, medical equipment, automobile industry, instruments, household appliances, military equipment and other fields.

The finished membrane switch shall be inspected for conformity from the following aspects:

Material: substrate, silver paste, carbon ink, spacer, adhesive, reinforcing plate, insulation printing shall comply with the drawing.

Shape: the shape, conductor line, insulation treatment, lining plate combination, etc. shall conform to the drawing or provide physical samples.

appearance

Combined state: the surface shall be free of residual material chips, foreign matters, stains, bumps, grease attached to the surface and inside, fingerprints on the line, and burrs on the punched shape.

Scar: all lines and contacts shall be free of cut marks penetrating the meter (that is, the cut marks shall be cut from the line to the base material). Minor scratches shall not affect the impedance. The carbon ink surface is easy to have scratches, and the scratches shall not affect the line continuity.

Foreign matter: The line shall not have any foreign matter attached to it.

Line conductor

Conductor thickness: generally, the conductor thickness is controlled at 7-12 μ m. It shall be even and smooth.

Conductor defects and pinholes: one is allowed within each 50mm range according to the following graphic standards.

Carbon ink: the carbon ink covering the silver paste line should be fully covered with the silver paste with a thickness of 8-10 μ m. There shall be no obvious silver paste projection.

Breaking and short circuit: no breaking or short circuit of conductor is allowed.

Insulation printing

All membrane switch contact points must not have any insulating ink attached.

The insulating ink surface shall be flat to avoid any bubble or pinhole that may affect the insulating effect.

Adhesion strength: after the insulation ink is dry, the ink surfaces shall be pressed against each other for 24 hours to ensure that the insulation does not adhere to each other. Affix the pressure-sensitive adhesive tape and press it for 1 minute without bubbles, and then peel it quickly without ink falling off.

Jumper: All jumper parts shall meet the requirements of line conductor, and all jumper products shall pass 100% open/short circuit test and insulation resistance test. Ensure that there is no open circuit, short circuit and insulation resistance is greater than 500M Ω (500VDC1 min).

Mechanical properties

Punching burr and die bending dimension: the punching burr and die bending dimension shall not be greater than 0.2mm, and the position shall face the side without conductor.

Position deviation of upper and lower lines: the allowable deviation of the center positions of each switch contact of upper and lower lines is Ф 0.5mm.