Inspections And Tests of Membrane Switch

Label:Membrane Switch

Nov 16, 20232640

Inspections And Tests of Membrane Switch

1. Shape

 

Many things, such as appearance, conductor lines, insulation treatment, liner combination, etc., should all comply with the drawings or the prototypes.

 

2. Materials

 

Graphic overlays, substrates, silver paste, carbon ink, spacers, adhesives, reinforcing plates, and insulation printing should comply with the drawings.


 

3. Visual inspection

 

The surface must be clean. The trimmed edges should be straight and beautiful. No chips, missing corners, burrs, distortions and other defects are allowed.

 

4. Quality

 

There are few things to talk about.

 

Graphic overlay

 

There should be no obvious defects (such as the text size, thickness of lines, missing strokes that affect readability, stains, light-transmitting spots, deinking, scratches, glue overflow on transparent window, residual glue, etc.). No misalignment or deviation (printing plate deviation ≤ 0.2 mm. Upper and lower line key combination deviation ≤ 0.5 mm. Line and key, panel and button combination deviation ≤ 0.3 mm. The deviation between the bubbles at the panel keys and the substrate ≤ 0.05cm).

 

Circuits

 

There must be no residual material scraps, foreign matter, stains, bumps and grease attached to the surface and inside, fingerprints on the circuits, burrs on the edges of the finished product. All circuits and contacts must not have cuts that penetrate the inside and outside. Slight scratches should not affect its impedance as a rule. Scratches on the surface of carbon ink should not affect the conduction of the circuit.

 

Conductive silver

 

Generally, the thickness of silver paste is controlled at 7-12μm. It should be uniform and smooth, without obvious defects or pinholes. No broken or short circuit is allowed.

 

Carbon ink

 

The carbon ink should ensure that the silver paste is completely covered. The thickness is 8-10μm, and there should be no obvious protrusion of the silver paste.

 

Insulating printing

 

All membrane switch contact points must not have any insulating ink attached. The insulating ink surface should be smooth to avoid any defects such as bubbles and pinholes that affect the insulation.

 

Jump wire

 

It's in accordance with line conductor requirements. All jumper products are subject to 100% open / short circuit tests and insulation resistance tests. The insulation resistance should be greater than 500MΩ (500VDC for 1 minute). Punching burrs and bending dimensions should not be larger than 0.02cm, and the position should be toward the side without conductors.

 

5. Check color

 

Use visual inspection to ensure that the color and position comply with the requirements of the drawing or relevant technical documents. Compare with the sealed prototype to see if there is any color difference. There should be no obvious different shades of color in the same batch of printed matter. The color should be uniform and of various colors. The lines should be clear and regular. No printing defects such as odd-colored spots are allowed within each color band.

 

6. Check ink adhesion

 

The ink is attached with transparent tape and pressed by hand to ensure that there are no bubbles and then peeled off quickly after 10 seconds. There must be no ink falling. After the insulating ink is dry, place the ink surfaces against each other and press hard for 24 hours to ensure that the insulating surfaces do not stick to each other. Use pressure-sensitive tape to attach it by hand without bubbles for 1 minute, then peel it off quickly without any ink falling off. Wipe the handwriting and patterns of self-adhesive printed matter with a damp cloth for 15 seconds, and then wipe with a gasoline cloth for 15 seconds. The handwriting and patterns should still be clear and legible (except for hot stamping products and film-attached products).

 

7. Bubble quality

 

There are equal height and balanced strength. Flat type: 57~284g force, touch feeling: 170~397g force.

 

8. Peel strength

 

The peel strength of the glue should not be less than 8N/25mm.


 

9. Folding strength

 

After drying silver paste, the silver paste circuit is covered with carbon ink. Measure the circuit resistance first. Then the circuit should be folded 180 degrees, and 2kg/2 of pressure should be applied with fingers. Then return it to a flat surface. Repeat this for 5 times, and then measure the resistance. The increased resistance after folding 5 times does not exceed 300% of the original value.

 

10. Adhesion durability

 

Clean the panel with organic solution, such as acetone, and then try to stick it on the panel for 24 hours. There should be no lifting or falling off by visual inspection.


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