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How to customize a suitable membrane keypad product?
2024-09-02 10:02:29
What are the most important considerations when designing membrane switches?
Membrane switch is an operating system that integrates key functions, indicating elements, and instrument panels. It consists of four parts: panel, upper circuit, isolation layer, and lower circuit. When the membrane switch is pressed, the contact of the upper circuit deforms downward and contacts the plate of the lower circuit. When the finger is released, the contact of the upper circuit rebounds, the circuit is disconnected, and the loop triggers a signal. The membrane switch has a rigorous structure, beautiful appearance, and good sealing. It is moisture-proof and has a long service life. It is widely used in electronic communications, electronic measurement instruments, industrial control, medical equipment, automotive industry, smart toys, household appliances and other fields.
Membrane switch, also known as touch keyboard, adopts an overall sealed structure composed of multiple layers of plane. It is a new type of electronic component that integrates optics, mechanics and electricity by sealing key switches, panels, markings, symbol displays and linings together. It is a fundamental change in the appearance and structure of electronic products. It can replace the keys of conventional discrete components and perform the tasks of the operating system more reliably.
Membrane switches have good waterproof, dust-proof, oil-proof, and anti-corrosion of harmful gases, stable and reliable performance, light weight, small size, long life, easy assembly, the panel can be washed without damaging the characters, rich colors, beautiful and generous, etc. Use membrane switches to make your products more contemporary. Main types of membrane switches The membrane switch panel is an electronic component that integrates switch functions and decorative functions, consisting of a rigid or flexible printed circuit board as the base, with buttons with or without feel installed, and covered with a plastic (polycarbonate PC, polyester PET, etc.) film panel printed with colorful decorative patterns. It is a new type of human-computer dialogue interface. The connection between the switch circuit and the whole machine can be completed by welding or plugging.
Film Panel
The film panel is a decorative panel with certain functional character indications made of elastic film (PVC/PC/PET). It has excellent characteristics such as waterproof, dust-proof, friction-resistant, and non-fading. It is currently widely used in household appliances, communication equipment, instruments, industrial control and other fields.
The printing process of the film panel is divided into front and back printing, which are used on film panels of different materials and types. It can be roughly divided into flat type and drum type.
The flat film panel is the simplest type of panel. It mainly uses different colors of text, lines, and color blocks to indicate or distinguish each functional part. Users can choose different film materials and double-sided adhesives according to their needs.
The drum type film panel is a new and more beautiful and practical panel developed on the basis of the flat film panel. Its production process is that on the basis of the ordinary panel, through a pressing mold, the panel is hot-pressed to make the key part slightly convex to form a three-dimensional key. This three-dimensional key can not only accurately give the range of the key body, improve the recognition speed, and make the operator's sense of touch more sensitive, but also enhance the decorative effect of the product appearance.
How should the thickness of circuit film be considered?
As the film of the circuit layer, considering the separation and rebound of the switch contacts and the reliability of the lead to the connector plug or riveting, the thickness of the circuit material should be selected between 0.125 mm and 0.15 mm. If it is too thin, the rebound will be weak and the separation of the contacts will be slow. If it is too thick, the action will be slow and the operation will increase. From the specific situation, the thickness of the film is also related to the following factors.
(1)Key size
When the key body is large, such as when the diagonal length or the diameter of the round key is greater than 12 mm, a 0.15 mm thick film is selected. The film is slightly thicker and has a strong rebound. After the key body is pressed many times, the film tends to relax less, thus ensuring the normal operation of the contact.
(2) The thickness of the isolation layer
The thinner the isolation layer, the thicker the circuit substrate film should be. Too thin a film is prone to contact self-contamination.
(3) The shape of the key body
Flat-type keys allow the use of slightly thicker films, and the film used for circuit contact bubbling is generally 0.125 mm thick. Only when the diameter of the bubble ball is large and the chord height of the ball top is small, a thicker film should be used.
Membrane Switch
There are many different forms and structures of buttons in membrane switch devices. The basic performance of buttons, such as travel, operating force and mechanical life, is mainly determined by the type and material of the button. Membrane switches include single-chip circuit switches and double-chip circuit switches.
Usually, the buttons on membrane switches only use color to express the position, shape and size of the key body. In this way, the accuracy of the operation can only be identified by the operator's vision. Since there is no appropriate feedback information to indicate whether the finger is pressed within the effective range of the switch to make the switch operate, it affects the confidence in monitoring the entire machine and the speed of operation. A membrane switch that makes the switch key body slightly raised and slightly higher than the panel to form a three-dimensional shape is called a three-dimensional key switch. The three-dimensional key can not only accurately give the range of the key body, improve the recognition speed, and make the operator's sense of touch more sensitive, but also enhance the decorative effect of the product appearance.
Switches can be classified into the following three main tactile structures according to their characteristics (Classification 1):
Metal dome button:
Metal dome buttons use formed metal domes, which are arranged inside the switch structure. The domes have button connectors to form an electrical circuit.
Advantages:
(1) This structure has good tactile properties.
(2) The service life is very long even under high temperature conditions.
Disadvantages:
(1) When used on soft panels, the panel may be damaged if it bends in the raised area.
(2) This structure is best used for printed circuit boards or rigid panels.
Polyester buttons:
Polyester buttons are buttons with raised edges rolled out of the circuit layer in the membrane switch structure. This structure is very durable and has a smaller stroke than metal dome buttons. In some applications, polyester buttons can be rolled into the mask layer, which can reduce the total number of layers of the membrane switch. The operating force of the button is related to the material thickness, button diameter and button raised height.
Advantages:
(1) Very durable
(2) Can be used millions of times
Disadvantages:
(1) Maximum operating temperature is about 50 degrees Celsius
Non-sensitive buttons:
The non-tactile switch has no tactile feeling. This type of operation panel usually uses other methods to indicate the operating status of the switch.
Advantages:
(1) Long service life (can be used tens of millions of times).
(2) Large effective area.
(3) Lowest price among all switch types
Disadvantages:
(1) No feel.
(2) If the mask layer has bulges, it is recommended not to use this type of switch.
Patch membrane switch refers to the extensive use of patch technology on the basis of membrane switch, which adds corresponding control devices to the original single switch, effectively reduces the space, increases the technological content of membrane switch, makes the whole machine small, miniaturized, integrated, and makes membrane switch reach a new level, with unlimited scenery.
In addition:
Basic types of membrane panel switch buttons (classification method 2)
1. Flat non-touch type
2. Film convex touch type
3. Metal spring convex touch type
4. Nameplate dome touch type
5. Add luminous membrane switch
Membrane key switch performance parametersTechnical parameter
Electrical properties：
1. Working voltage: ≤ 50V (DC)
2. Working current: ≤ 100mA
3. Contact resistance: 0.5 ~ 10 Ω
4. Insulation resistance: ≥ 100m Ω (100V / DC)
5. Base material withstand voltage: 2KV (DC)
6. rebound time: ≤ 6ms
7. loop resistance: 50 Ω, 150 Ω, 350 Ω, or as required by the user.
8.Insulation ink withstand voltage: 100V / DC
Mechanical properties：
1. Reliability service life: > 1 million times
2. Closing displacement: 0.1-0.4mm (tactile type) 0.4-1.0mm (tactile type)
3. Reference force: 15-750g
4. Migration of conductive silver paste: 10M Ω / 50VDC between two wires after 56 hours at 55 ℃, 90% temperature
5. There is no oxidation and impurity on the silver pulp line
6. silver paste line width ≥ 0.3mm, minimum interval 0.3mm, line burr < 1 / 3, line gap < 1 / 4 line width
7. pin spacing standard 2.54 2.50 1.27 1.25 1.0 0.5mm
8.The curvature resistance of outgoing line shall be continuously rolled 80 times with d = 10 mm steel rod.
Environmental performance
1. Working temperature: - 20 ℃ ~ + 70 ℃
2. Storage temperature: - 40 ℃ - + 85 ℃ 95% ± 5%
3. Atmospheric pressure: 86 ～ 106kpa
Printing index
1. The printing size deviation is ± 0.10 mm, and the shape sideline is not clear and the deviation is ± 0.1 mm
2. The chromatic deviation is ± 0.11mm/100mm, and the insulating ink is completely covered with silver paste line
3. No ink scattered, no incomplete handwriting
4. Color difference shall not be greater than level II
5. No crease or paint peeling
6. the transparent window is transparent and clean, with uniform color, without scratches, pinholes and impurities.
For more information,please contact us:
SHENZHEN CHANGMAI TECHNOLOGY Co.,LTD
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