Manufacturing And Tests of Membrane Switches

Label:Membrane Switches

Apr 27, 202393810

Manufacturing And Tests of Membrane Switches

1. Manufacturing


Clean the surface of the membrane switch that needs treatment (the surface is required to be flat, rust-free, oil-free, and dust-free)


Inspect and compare the size (put the membrane switch to the place to be pasted, and compare the size and position to see if everything's good).


Peel off the centrifugal paper at the bottom about 10mm from the edge.


Put the membrane switch in the corresponding position. Then stick it to a part, and tear off the remaining centrifugal paper (under the condition that the angle is within 15 degrees). Stick it to the corresponding position in turn.


If it is necessary to place the centrifugal paper during the pasting process, place it on the reverse side to prevent it from sticking to other objects. Otherwise, it interferes the pasting.


Tips: Don't repeat pasting. Finish it at one time. the tearing angle must be within 15 degrees. When feeling the touch, place it flat on the table, then press it. You can't held it in the air to press. Otherwise, it decreases the service life of membrane switch.


2. Inspection And Tests


· Material inspection


Make sure that panels, substrates, silver paste, carbon ink, spacers, adhesives, reinforcement boards and insulating printing comply with the drawings.


· Identify shape


Make sure the shape, conductor circuit, insulation treatment, liner combination comply with the drawings or physical samples.


· Check size


The allowable range without tolerances in the drawings must meet the standards, and other sizes meet the requirements of the drawings.


· Check appearance


There is no obvious defects, such as missing letters, stains, light spots, deinking, scratches, transparent window overflow glue, residual glue, on graphic overlay. No deviation on printing overlay. No bubble on the combination of upper and lower line keys, combination of line and key sheet, panel and key. The stamping burr and extrusion size should not be greater than 0.2mm. The position should be towards the side without conductors.


· Check color


Compare the color with the sample or color card to see if there is any difference. If the color requirements are particularly strict, use a color difference meter to compare.


· Check ink adhesion


The ink is attached to the transparent tape. Press it by hand to ensure that there are no air bubbles. Then peel off quickly after 10 seconds. There must be no ink dripping.


After the insulating ink is dry, put the ink surfaces against each other and press heavily for 24 hours to ensure that the insulating surfaces do not stick to each other.


Use a pressure-sensitive tape to stick it with hand pressure without air bubbles for 1 minute, then peel it off quickly without ink falling off.


· Peel strength test


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


Folding strength test: After drying the silver paste and carbon ink circuit, measure the circuit resistance first. Then the circuit should be folded 180 degrees, and pressed with fingers for 2kg/2 seconds. Then return it to the plane.


Repeat the process back and forth 5 times, then measure the resistance. The increased resistance after folding 5 times does not exceed 3 times of the original value.


· Measure loop resistance


The value should not be greater than 100Ω. For the total length of the loop longer than 150cm and other special requirements, the loop resistance should be specified separately on the drawing. No disconnection or short circuit is allowed.


· Measure insulation resistance


In normal temperature and humidity environment, the insulation resistance of the conductor circuit is greater than 500MΩ (500VDC for 1 minute). After high temperature and constant humidity test and salt spray test, it should not be lower than 20MΩ.


· High temperature test


After the membrane switch is subjected to a high temperature of 55±2°C for 72 hours, the appearance meets the drawing requirements. After recovering for 2 hours under normal atmospheric conditions, the value should meet the requirements.


· Low temperature test


After the membrane switch is subjected to a low temperature of -10±3°C for 16 hours, it is recovered under normal atmospheric conditions for 2 hours. Wipe off the water drops on the surface. The resistance value should meet the requirements.


· Salt spray test


After the membrane switch is subjected to salt solution with 5% sodium chloride, the temperature in the test space should be 35±2°C (the connector is sealed) after 72 hours of salt spray test.


After 2 hours of recovery under normal atmospheric conditions, the insulation resistance meets the requirments.


· Constant damp heat test


The membrane switch is subjected to 40±2°C and a relative humidity of 93 (+2%–3%). After 96 hours of constant damp heat test, it should be recovered under normal atmospheric conditions for 2 hours. The insulation resistance, loop resistance and key force should meet the regulations.


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