How to Provide a Good Membrane Switch to Customers?

As a Membrane Switch Supplier, How to Provide a Good Membrane Switch to Customers. Membrane Switch Inspection Methods and Steps

• Shape: shape, conductor line, insulation treatment, lining board combination, etc. should conform to the drawings or provide physical samples.

• Material: panel, substrate, silver paste, carbon ink, septum, adhesive, adhesive, reinforcement board, and insulation printing should comply with the drawings.

• Check the appearance quality: the scope of this inspection is wide.

• Panel: There must be no obvious defects (such as lack of strokes affecting the readability of characters; stains, light transmission points; deinking, color spots, scratches; transparent window overflow glue, residual glue, etc.); no deviation phenomenon (print sleeve Offset of plate ≤0.2mm; Offset of the key combination of upper and lower lines ≤0.5mm; Offset of a combination of circuit and key sheet, panel and face key ≤0.3mm; Offset of the blank area around the back of panel and circuit combination ≤0.2mm; Panel (The key bump and substrate offset ≤0.5mm).

• Lines: There must be no residual material chips, foreign objects, stains, irregularities and grease attached to the surface and inside, fingerprints on the lines, burrs on the edges of the finished shape; all lines and contacts must not have cut marks that penetrate through the surface The circuit is cut to the substrate), and the slight scratches are also based on the principle of not affecting its impedance. The scratches on the surface of the carbon ink are based on the principle of not affecting the conduction of the circuit. The circuit must not have any foreign objects attached to it.

• Conductive silver: The thickness of the silver paste is generally controlled at 7-12 μm, and should be uniform and smooth, without obvious defects and pinholes. No break or short circuit is allowed. Carbon ink: The carbon ink-covered on the silver paste line should ensure that the silver paste is completely covered. Its thickness is 8-10 μm, and there must be no obvious silver paste protruding.

• Insulation printing: All custom membrane switches keypads contact points must not have any insulation ink attached. The surface of the insulating ink should be flat to avoid any bubbles or pinholes and other defects that affect the insulating effect.

• Jumper: All jumper parts are in accordance with the requirements of the line conductor, and all jumper products must pass 100% open and short circuit tests and insulation resistance tests. Make sure that there is no open, short circuit, and insulation resistance should be greater than 500MΩ (500VDC for 1 minute).

• Stamping burr and die squeezing size: The stamping burr and squeeze bending size should not be greater than 0.2mm, and the position should be toward the side without a conductor.

• Check the color: use the visual method to compare with the sealing sample to see if there is any color difference. The color requirements are particularly strict.

•  Check the adhesion of the ink: the ink is attached by hand with transparent tape to ensure that there are no air bubbles after 10 seconds, and the ink is quickly peeled off, and there should be no ink drop. After the insulating ink is dried, the ink surfaces should be placed against each other and then pressed for 24 hours to ensure that the insulation does not stick to each other. After applying pressure-sensitive tape for 1 minute without air bubbles, it peeled off quickly and no ink fell off.

•  Bubbling quality: the height is equal and the strength is balanced. Flat type: 57 ~ 284g force, touch feeling: 170 ~ 397g force.

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

• Folding strength: after drying the silver paste, carbon ink circuit, or silver circuit covered carbon ink, the circuit resistance should be measured first, then the circuit should be folded 180 degrees, and the finger should be pressed 2kg / 2 seconds, Then make it back to the plane, so back and forth 5 times, and then measure its resistance. The increased resistance after folding 5 times does not exceed 300% of the original resistance.

• Hardness: Use a class H drawing pen to apply a 1kg thrust to the circuit at 45 degrees. The circuit must not peel off conductive ink or produce light.

• Dimensions: The allowable tolerances of the drawings without tolerances are shown in Table 1, and the rest are in compliance with the drawings.

General size (mm) Allowable tolerance (mm)

18 or less ± 0.2; 18-50 ± 0.3; 51-125 ± 0.4; 126-250 ± 0.5; 251 or more ± 0.6

• Loop resistance: The loop resistance value should not be greater than 100Ω. For loop lengths greater than 150cm and special requirements, the loop resistance is specified separately on the drawing.

• Insulation resistance: In a normal temperature and humidity environment, the insulation resistance of the conductor line is greater than 500MΩ (500VDC for 1 minute). After high temperature and constant humidity test and salt spray test, it should be no less than 20MΩ.

• Lifetime: The number of contact conduction for each button without reed should be 1 million times. The number of reeds and tactile conduction should be 500,000 times.

• High temperature: After the touch keypad membrane switch is subjected to a high temperature of 55 ± 2 ℃ for 72 hours, the appearance quality should be in accordance with the drawings. After recovering for 2 hours under normal atmospheric conditions, the measured insulation resistance value should meet the regulations.

• Low temperature: After the film is subjected to a low temperature of -10 ± 3 ℃ for 16 hours, recover under normal atmospheric conditions for 2 hours, wipe off the water droplets on the surface, and measure the resistance value of the return line in accordance with the regulations.

• Constant damp-heat: Membrane switch withstands 40 ± 2 ℃, relative humidity is 93 (+ 2% –3%), after 96 hours of constant damp heat test, recover under normal atmospheric conditions for 2 hours, measure insulation resistance, loop resistance 3. The button force should meet the regulations.

•  Salt spray test: The membrane switch is subjected to a salt solution of 5% sodium chloride, the temperature in the test space is 35 ± 2 ℃, (connector seal). After 72 hours of salt spray test, it is restored for 2 hours under normal atmospheric conditions, Insulation resistance should meet the regulations.