Membrane switch It is an operating system that integrates key functions, indicator elements, and the instrument panel into a single unit. ， Beautiful and lightweight, Excellent electrical conductivity , possessing Waterproof 、 Prevention Dust, Anti-static interference, etc. Characteristics ， Widely used in electronic communications, medical devices, industrial control, instrumentation, the automotive industry, Intelligent home Reside and other fields 。 The following is a brief introduction to the manufacturing process of membrane switches. 。

I. Engineering Design

Several Common Structures of Membrane Switches

                    

The structure of a membrane switch is divided into Panel layer 、 Adhesive layer, upper circuit, and interlayer (insulating layer) )、five structural layers, including the circuit layer and the adhesive backing. Panel layer generally Adopt thickness 0.25 Below mm of High toughness PET or PC transparent colorless sheet ， seal Brush Composed of patterns and text, Its Main function Yes Functions as a label and button ； face Generally glue Adopt 0.05 ---0. 15 mm thick of Strong double-sided adhesive, Attach the panel to Above Closely coupled circuit Adhesion; both the upper circuit and the lower circuit Adopt 0.125 mm thick (in some cases, it will be used 0.075 and 0.1 (mm in thickness) Resilience Sex Excellent High-quality polyester film (PET) ， Screen printing Conductive Silver paste and conductive Carbon slurry ， Drying and Aging To impart conductivity , for circuit outlet connector spacing less than At 1 mm, the gold fingers of the connector can easily pierce the silver paste, leading to defects. It is recommended to use a highly wear-resistant FPC for the entire circuit to eliminate such defects. ； Mezzanine is in Acts between the upper circuit and the lower circuit Insulation and Sticky The function of connection , generally using a thickness for 0.1 --0.2 5mm with PET of the substrate Double-sided tape ; the lowest level Adhesive backing , one must first consider its What material should it be bonded to? , select one that can bond with the adhesive surface Close proximity Strong adhesive double-sided Glue. A membrane switch is an integrated assembly, and all material selections must take into account the overall seal integrity. Sex , water resistance, insulation, and aging resistance, For outdoor membrane switches, it is also necessary to account for exposure to wind and rain, temperature fluctuations between winter and summer, and the strong ultraviolet radiation from sunlight. 。

Overall Design of the Membrane Switch by Engineering Personnel ， It is necessary to consider comprehensively and also... Taking both scientific rigor and manufacturing feasibility into account, Ensure that the manufactured products are stable, reliable, economical, and practical. 。

II. Printing

The printing of membrane switches is mostly carried out using screen printing.

The prepress stage of screen printing is Expose the plate ， Before plate-making, it is necessary to First Use Compare with the film reference sample to verify that the film is correct and undamaged. ， Check whether the screen mesh has been thoroughly cleaned and whether there are any Filth and Small damaged hole , under normal circumstances For circuit use 100T network Board, For panel use 120T screen printing stencil Sun-drying (especially fine ones will use it) 140T or 160T the mesh panel ) 。 Then Compare with the sample to determine whether the film is positive or negative exposure. Special attention must be paid to the circuit: the bottom circuit, insulating oil, and jumper wires should be exposed to sunlight on the positive side; the top circuit should be exposed on the reverse side; the shielding layer should be exposed on the positive side (printed on the front side of the top circuit). 。

Ink of Mixing is a crucial step in the silk-screen printing process, directly affecting Appearance quality of membrane switches Quality. Colorist It is essential to have a solid grasp of color theory and ink-mixing techniques. , to prepare the mixed ink Vivid colors, excellent brightness, and accurate hue.    
                     Rules of the Three Primary Colors' Variation

             

   Theoretically Any color can be created using the three primary colors. (magenta, yellow, cyan ) mixed in different proportions And Success, three kind When primary-color inks are mixed in equal amounts, they produce black. ( Approximation ) . Three kind By mixing primary-color inks in equal proportions and adding white ink in varying ratios, gray inks of different hues can be formulated. Three kind When primary inks are mixed in various proportions, they can produce a wide range of intermediate or composite colors, with the hue tending toward that of the primary ink present in the larger proportion. Mixing two primary inks in equal parts yields a standard intermediate color; mixing them in different ratios produces a variety of intermediate hues, each leaning toward the hue of the primary ink that is present in the greater proportion. Furthermore, adding white ink to any colored ink makes its hue appear brighter, whereas adding black ink darkens the hue.

Screen printing Breakup printing (sample printing), semi-automatic machine printing (small batches), and automatic machine printing. Install network Edition Previous First, we need to Compare the sample to verify that the screen frame is correct, that the screen film is undamaged, and that it has not been exposed upside down. ( Special attention to the circuit ). During the printing process, the registered color alignment of the printed products must be repeatedly checked to ensure consistency and accuracy, and to detect any issues such as smearing, dried-up screens, or dust accumulation. Any problems found must be addressed promptly. Machine adjustment Correct. Every step must involve repeated checks to ensure the product is flawless, fostering the good habit of self-inspection. , at the same time Ensure the workshop and workstations are kept clean and tidy. , camp Choose a harmonious and efficient work environment.

III. Assembly

Assembly is subdivided into processes such as punching, blistering, spring insertion, lamination, forming, and terminal crimping.

Punching is a critical factor for precise bubble formation; inaccurate hole positioning can cause the bubble key to be off-center and result in warping during molding, leading to defective products. Once the hole-position sampling settings are properly configured, it is essential to verify that the punched holes are centered (the hole-position deviation must not exceed (0.05 mm); if it fails, resample.

Bubble quality This is closely related to the quality and precision of the mold: if the curvature of the mold’s keycaps is too conical, the panel is prone to bubbling and may fail to spring back; if the curvature is too pronounced, the panel will bubble and feel unpleasant to the touch. Therefore, each keycap must have… Height ( 0.3~ 0.5 mm) Equal, intensity ( 16 0~39 0 G-force ) Balance.

Membrane switches typically use nickel-plated domes (buzzer domes). ), when high stability of the resistor and high key sensitivity are required, gold-plated spring contacts may be used (in special cases, gold-plated terminals are also employed). Before installing the spring contacts (domed contacts), first arrange them properly. Use tweezers to pick up the shrapnel and place it on Electricity Ensure that the button positions on the circuit board are centered. After placing each shrapnel, use tweezers to press it down to confirm there is no double-shrapnel phenomenon; if double shrapnel occurs, The situation arises, of the membrane switch The feel will noticeably become heavier, or even completely lose its feel. 。

Lamination is the central step in the assembly of a membrane switch, involving the bonding of each structural layer into a single integrated unit. First, the spacer layer is laminated to the bottom circuit; then the top and bottom circuits are aligned and laminated together (for switches with contact springs, the springs are first embedded in the key cavities of the spacer layer, followed by lamination of the spring-retaining layer). Next, adhesive is applied to the front side of the top circuit and adhesive backing is applied to the back side of the bottom circuit; if If the LED routing is a separate structural layer, then it is necessary to LED First punch holes in the translucent areas, then apply the adhesive. LED Route the wiring layers and apply adhesive backing to the reverse side; finally, affix the face panel (for panels with transparent windows and lamp holes, first cut out the adhesive layer in those areas). At every step of the bonding process, pay close attention. No bubbles or foreign matter allowed. ， Colloids cannot wrinkle (see specific details in “ Film Switch Assembly Techniques 》 One article )。

Stamping Forming has strict dimensional requirements. For small-batch products, die-cutting molds can be used, with random dimension checks performed at irregular intervals using calipers to verify accuracy and inspect for mold deformation; it is best to conduct trial fittings of the housing. If mold deformation is detected, production should be immediately halted and a new mold fabricated. For larger-volume production, steel molds are preferred, as they exhibit minimal deformation and deliver more precise dimensions. Depending on the specific circumstances and customer requirements, Permissible Tolerances for Dimensions Not Indicated on the Drawing General Such as Next:

General size (mm) Permissible Tolerance (mm)

Under 18 plus or minus 0.1

18-50   ±0. 15

51-125   ±0. 2

126-250   ±0. 3

251 or above plus or minus 0.4

Film switch after stamping and forming The burr and die-induced bending dimensions shall not exceed 0.2mm， Furthermore, the position should face the side without conductors.

Golden Finger PI N Distance to Yes 2.54mm， Generally, terminals must be crimped and a black housing installed. ( There are very few requirements. 1.27mmPI N Distance to Terminal punching )， Terminals are divided into male and female types. Big Majority Membrane switch to hit mother end 。 PI N Distance to for 1.27 mm, 1. 0 mm, 0 .5mm, General Do not strike the terminal. In Golden Finger back Face mask Above Strengthening, Position 1 for Strengthening General Pingqi Golden Finger Carbon Pulp Stick at Golden Finger back Face, Special The situation is as specified.

   

                

IV. Detection

     Appearance Panel with a membrane switch No obvious defects are allowed. ， If a character is missing strokes , varying in thickness; there are in the background color blocks Stains, light-transmitting spots 、 Deinking, discoloration, scratches ； Transparent window Unclear ( F150 and F200PET seal Ultraviolet Special precautions for window fluid), Excess glue, residual glue, etc. ； No deviation phenomenon ( Printing registration misalignment less than or equal to 0.15 mm ； Key combination for toggling online/offline is misaligned. less than or equal to 0.3 mm ； Misalignment between the circuitry and keycaps, and between the panel and keys. less than or equal to 0.3mm； Misalignment of the blank areas around the perimeter after panel and wiring assembly less than or equal to 0.2mm； Bubbling at the panel button area and substrate misalignment less than or equal to 0.5mm ) 。

    Functional testing requirements for membrane switches 100% full inspection; no open circuits, short circuits, or poor insulation allowed; with LED There must be no lights. LED Leakage current phenomenon, with resistance LED It will soon become necrotic. Each key on the membrane switch The loop resistance shall not exceed 8 0Ω, for loop lengths greater than 400m m and There is Special Requirement: Loop Resistance of As otherwise specified on the drawings. In a normal temperature and humidity environment, the conductor circuit interval The insulation resistance is greater than 5000K Ω ( 500VDC1 minutes). After high-temperature and constant-humidity testing, as well as salt-spray testing, it shall not be less than 2000 K Omega.

 

 

Lifespan Test requirement: single Button In Under a 2N pressing force, Contact conduction of The number of times should Greater than 1 million times With Above (Able to be tested for special requirements 2 million times) 。 However, inspect the keycaps for deformation or damage, and carefully peel back the structural layers to check for internal damage, wear, or other defects. Lifespan The testing was conducted only over a relatively short time period and did not account for the full duration of actual use or changes in the operating environment.

High Low Warm Test, put Membrane switch Stick it to the housing, and after one week, place it in the oven, setting the temperature to 60 degrees Celsius Constant temperature ( plus or minus 2 degrees Celsius ) ， After After 72 hours of high-temperature exposure, After removing from the oven and letting it cool , measure Whether the test power performance is Compliant with regulations Has the external dimension changed? Are there any cracks or delamination in the adhesive? 。 Similarly, place it in the freezer. To endure -20 degrees Celsius Constant temperature ( plus or minus 2 degrees Celsius ) , lasting 120 After exposure to low temperatures for a few hours, After removing from the freezer and allowing to return to room temperature , wipe off the water droplets on the surface, and measure Whether the test power performance is Compliant with regulations Has the external dimension changed? Are there any cracks or delamination in the adhesive? 。 Requirements Acid- and alkali-resistant Salt of the product, put Membrane switch Place into the one containing 5% of Acid and alkali Salt solution, After removal, high- and low-temperature testing is conducted, ultimately Measure Test whether all electrical performance parameters and appearance are Complies with the regulations.

V. Packaging and Warehousing

  The key to packaging and warehousing is to avoid excessive pressure; multiple products must never be stacked flat. All items must be stored upright, and when packing, consider placing smaller boxes inside larger ones, so that Prevent key failure due to prolonged heavy pressure 。 The leads of the membrane switch must be properly protected. Avoid film switch leads Qualify There is a possibility of bending under any circumstances, and at the same time the warehouse must to do Good Moisture-proof 、 Dust-proof treatment; the surrounding air contains no acidic, alkaline, or other corrosive gases.

VI. Key Points Parameters

　　⒈ Operating voltage: ≤50 VDC

　　⒉ Operating current: ≤100 mA

　　3. Contact resistance: 0.5–10 Ω

　　4. Insulation resistance: ≥100 MΩ (100 V DC)

　　5. Base material withstand voltage: 2k VD C

　　6. Rebound time: ≤6 ms

7. Loop resistance: ≤ 8 0Ω ( Single-key return line length Within 40 cm)

8. Insulating ink withstand voltage: 100 VDC

　  9. Reliability and service life: >1 million times

　 10. Buttons Force degree ：160 ~ 4 50g of force

　　11. Operating temperature: – 3 0℃～+ 5 0°C

　　12. Storage temperature: – 2 0℃～+ 4 5°C Wet degree 95% ± 5%