1.Single membrane switch recognition
1.1.Introduction to the membrane switch
It consists of a certain elastic material (PET) and a conductive layer. This is a multi-layer planar non-self-locking button switch. It has an elastic insulating film with a conductive pattern (switch contact). It also has spacer elements that maintain a certain stroke. Moreover, the single membrane switch can be a combination of one or more switch contacts. Unlike traditional metal dome switch, It has good waterproof, dustproof, oil proof and anti-harmful gas erosion characteristics. Similarly, stable and reliable performance and high quality are some of the reasons why membrane switches are favored. The membrane panel can be washed and the characters are not damaged. The richness of color is the reason why the membrane switch can be quickly promoted. This also led to the metal dome switch gradually withdrawing from the stage of history.
Single membrane switches have been widely used in intelligent measuring instruments and medical instruments. Even CNC machines, electronic scales, can use membrane switches. Undoubtedly, single membrane switches can use in home appliances such as remote controls.
This is a process made of an elastic film. And the general elastic film is divided into PC, PET, HP. The typical membrane panel has a certain functional character index. And it can mark the button position. It is a decorative panel with a transparent display window.
1.3. Touch keypad membrane
It is composed of a membrane switch and a membrane panel. The single membrane switch includes a metal film, a touch screen, a metal dome, and a graphical interface. So, membrane keyboards are usually straightforward to operate.
1.4. Return line resistance (guide band resistance + contact resistance)
A contact on the membrane switch is turned on. Thus, the turned-on contact connects the resistance between the two leads.
The operating force applied to the membrane switch when the contacts are turned on.
2.The classification and advantages of membrane switches
According to the difference in structure, combination and process of the membrane switch, and the end product used by it is different from the crowd. Generally can divide into the following commonly used types.
2.1.Metal shrapnel type (pot piece)
Using shrapnel as the key contact surface, it has three distinct advantages:
1. The button feels good and the intensity is even.
2. You can hear a crisp sound during operation.
3. It can still be used normally under a high-temperature environment.
However, it also has an obvious drawback. When the lining has a bump or a curved arc that is too large, the shrapnel may be damaged. This can cause a short circuit or no rebound.
2.2.Hot pressing hand type (polyester button)
The button uses the typical membrane material to print the contact surface, and the bump is formed to form a resilience.
Its advantage is that the button life reaches more than one million and feels good. But, its use in high-temperature environments may cause the button to feel to weaken.
2.3.Flat touch type (no feel)
The contact surface does not use any secondary process. It can achieve a button life of more than 1 million times. Moreover, its contact area is large and easy to operate. However, its shortcomings are also very obvious, due to the lack of feeling, it is easy to cause misuse.
2.4. EL backlight type
An EL backlight is embedded in a conventional touch keypad membrane. Even in low-light areas can use this membrane switch, regardless of the site environment. regardless of the site environment. But, due to the high cost, and the EL needs to equip with a driver, the power supply 110v. This makes practical applications not much.
2.5.Light guide plate type
A light guide plate is embedded in a conventional film switch. It can also use a membrane switch in places where there is insufficient light. And make the switch as a whole more enjoyable. And its biggest advantage is that its cost is lower than the EL. But, it has the greatest advantage of the EL backlight type. The biggest drawback of the light guide plate type is its high thickness. This is only suitable for the embedded fixing method. Otherwise, it will affect all viewing of the switch.
2.6. PCB type
The membrane switch panels circuit layer uses a PCB (hard circuit board). It has low on-resistance and high precision circuitry. This should be the ideal one for membrane switches. But, it cannot be bent. As a result, the actual use of the application, the use of the scene is very limited.
2.7. FPC type
That is the membrane switch circuit layer uses FPC (Flexible Circuit Board). Compared with the PCB type, it has the advantages of low resistance and high precision of the circuit. At the same time, due to its flexible nature, it can be bent. This makes it better to meet the actual application. However, due to its high energy capability, the technical requirements are high. The cost of the investment is large, resulting in a higher cost.
3.Panel material for single membrane switch
A single membrane material is suitable for making a panel layer. According to its type, it can be generally divided into three types: PC, PVC, and PET. The sand surface and the smooth surface (transparent film) constitute the surface state.
The comprehensive index of physical and chemical properties of PC materials is better. The inks it adapts to are also more extensive. So, it has become the most common material for membrane switch panel applications. PC materials have the difference between sand and glossy. Because the tactile switches are mostly used in electronic products, so choose the sand surface material. Panels that operate as control systems are not expected to be subject to light interference. The sand-like surface is only reflective and does not produce bright reflections. At the same time, due to the disordered sand-like surface, it has the effect of shielding scratches. In contrast, glossy materials do not have the above characteristics.
As a glossy material, once printed on the back, the color will appear more vivid. In cases where the decorative requirements are strong and do not need to touch. Face panels are often chosen to make panels. Or because of the special needs of some display areas such as LCD screens. It is helpful to use a smooth material.
3.1 Material comparison of single membrane switches
The price of PVC film material is relatively low, about one-half of that of PC materials. If you produce civilian popular products. If you choose PVC materials, you can reduce production costs. At the same time, the PVC material has good elongation and can be processed by cold pressing. Glossy PVC sheets generally have a thickness of more than 0.5 mm. Both sides are protected by PET or glue paper. Most are used to make decorative panels. The PVC material of the sand surface is generally less than 0.3 mm thick. It is generally supplied in fixed length sheets without coils.
The surface state of the PET metal dome membrane is divided into a smooth surface and fine sand. This applies to products with high requirements for scratch protection. But the price is more expensive. PET film has a long life and good corrosion resistance. And its excellent insulation performance. This can be applied to the required instrumentation and home panels.
4.Technical requirements for single membrane switches
Its graphic overlay, conductive lines, must follow the drawings. Moreover, the insulation treatment and the lining combination must also follow the drawings. Unless a physical sample can provide. In addition, industrial control is important to the shape of the membrane switch. Especially when performing large-scale screen printing, it is mechanized due to snap action. In the event of a mistake, the situation will be very serious. However, with the advent of mechanical pages, the difficulty of industrial control has been reduced. However, artificial industrial control is still very important.
4.2 Material of single membrane switch
Silver paste and carbon ink should follow the provisions of the drawings. Adhesives, adhesives, reinforcing plates, and insulation printing should also follow the drawings.
4.3 Appearance of single membrane switch
1. The surface of the metal dome switch must have no residual material or foreign matter. Even stains, bumps, and grease adhering to the surface and inside must not remain. Similarly, the fingerprint on the line, the burr of the shape is to be cleaned.
2. The line must not have any foreign objects attached to it.
3. All lines and joints must not have cut through the table. Slight scratches are also based on the principle that the impedance is not affected. The surface of the carbon ink is easily scratched, and the scratches are not affected by the line conduction.
4.4. Line conductor of single membrane switch
1. The thickness of the conductor is generally controlled within 7-12 mm and should be uniform and smooth.
2. The conductor is not allowed to have any break or short circuit.
3. Carbon ink covering the silver paste line should ensure that the silver paste is completely covered. Its thickness is 8-10 mm, and there must be no obvious silver paste protruding.
4.5. Insulation printing
1. Do not have any insulating ink attached to all membrane switch contacts.
2. The surface of the insulating ink should be flat to avoid any defects such as bubbles or pinholes.
3. Adhesion strength, after the insulating ink, is dried. The ink faces were placed against each other and then pressed for 24 hours. After that, make sure that the insulation is not sticky. Adhesive with a sub-sensitive tape to remove no air bubbles for 1 minute. Then we have to peel off quickly. At the same time, there is no ink falling off.
4. All jumper sections are required by the line conductor. All jumper products are subject to 100% open, short circuit test and insulation resistance test. Make sure that there are no open, short, and insulation resistances greater than 500 MA.
4.6. Electrical performance
1. In a normal temperature and humidity environment, the insulation resistance of the conductive line is greater than 500 MA. In the high temperature and constant temperature test, the salt spray test should be no less than 20 MA.
2. The return line resistance value is no more than 100 MA. The total length of the return, a line is greater than 150cm and special requirements. The return line resistance is additionally specified on the drawing.
4.7. Environmental testing
The stock membrane switch is subjected to high temperatures of around 55 degrees Celsius. After that, it took 72 hours of high-temperature action. After switch capacitive touch, the quality of the inspection should be under 4.13