Tactile Surface Mount, PCB Tact Switch

Selection method of tact switch
The factors affecting the quality of tact switches are mainly determined by factors such as the protection, weldability, conduction reliability, life, feel, production process and installation size of tact switches. The first is the base material of the pin. The base material of the pin of the tact switch is brass or phosphor copper (the low-grade one is iron). In order to reduce the contact resistance, the pins are basically silver-plated, because silver will be oxidized when it encounters SO2 gas in the air, which directly affects the solderability and contact resistance of the switch. Therefore, high-quality tact switches must first be controlled in place in terms of the silver-plating thickness of the base material of the pin terminal and the silver-plating process. The order of silver plating on the market is as follows:
Silver plating thickness: 0.3um or more (rear silver), 0.2um (thin silver), 0.1um (white plating)
Silver plating process: the base material is pre-plated with nickel and then plated with silver, the base material is pre-plated with copper and then plated with silver, and the base material is directly plated with silver. Whether the base material is treated with a protective agent after silver plating or whether the switch is dustproof and waterproof is very important. Otherwise, even with the best silver plating treatment, the switch will be oxidized.
Secondly, the key influencing factor of conduction reliability is the structure of the contact point, because the function of the tact switch is the contact conduction between the contact point and the shrapnel. Then the larger the contact surface of the contact point, the better, and the contact surface is determined by the structure. There are roughly three types of structures on the market, the order of pros and cons is as follows:
Large bubble (crater type) “O-type contact”, slotted type “2-point contact”, flat-bubble type “1-point contact”

Third, the life and feel are determined by the stroke of the light touch switch and the cooperation of the shrapnel. The shorter the stroke, the lighter the sound, the longer the life, and the longer the stroke, the opposite. In the case of a fixed shrapnel process, the life of the tact switch is mainly determined by the stroke or sound;
In addition, the key factor determining the life of the shrapnel is the stamping technology. The stamping technology of Japan and Taiwan is already very popular in China. Therefore, in the case of technological improvement, the import requirements for materials are reduced. For example, there are four main types of 160gf shrapnel life in the market: about 50,000 times (domestic phosphor bronze or relatively backward stamping technology), about 100,000 times, and more than 200,000 times (stainless steel).

The fourth is the production process of light touch switches. After the accessories are available, it is the assembly process that ultimately affects the quality. The assembly process depends on factors such as the management capabilities of the production company, employees’ quality awareness, and quality assurance capabilities. The quality of the final product produced by different guarantee capabilities must be different, and the market assembly methods include manual and machine. The machine assembly cost is low but the product quality is low. The cost of manual assembly is high but the quality is also high.
The fifth is the factory inspection of the tact switch. The method and items of factory inspection also affect the quality of the final tact switch, such as whether the appearance, feel, conduction, resistance and other items are random or full inspection. For example, some large factories require that the scrap rate be measured in PPM or zero defects. After the full inspection is set up in the factory inspection, procedures such as random inspection or quality inspection must be set up.

Life test of tact switch
The main test is the number of opening and closing until it breaks. If you don’t need to manually use a small motor to drive the eccentric opening and closing switch, use a counter to record the number of times! This switch requires safety certification. If the product is sold in China, CQC is used. For foreign countries, it depends on which country the specific sales go to, such as UL in the United States, CUL in Canada, and safety certifications such as VDE, ENEC, and TUV in European countries. Life of domestic shrapnel: 50,000 to 70,000 times. Life of imported shrapnel with silver on one side: more than 100,000 times. Stainless steel shrapnel has a long life of more than 500,000 times.

Estructura del interruptor táctil
Los interruptores táctiles se dividen en dos categorías: los que utilizan lengüetas de metal como contactos de interruptor se denominan interruptores táctiles, con una resistencia de contacto pequeña y un grupo de 20mn. Se siente bien en la mano y tiene un sonido nítido de “tic”. Un interruptor que utiliza goma conductora como ruta de contacto se denomina interruptor de goma conductora. El interruptor se siente bien, pero la resistencia de contacto es grande, generalmente 100-300n. La estructura del interruptor táctil de luz es para moverse hacia abajo por el botón, de modo que la lengüeta de contacto o el bloque de goma conductora haga contacto con la pieza de soldadura para formar un camino.
La fuerza de operación del interruptor táctil ligero está relacionada con el estado de la lengüeta de metal. La fuerza inicial es proporcional a la distancia que se comprime la caña. Cuando la lengüeta de metal se comprime del 5% al 70%, la fuerza de operación disminuye repentinamente, acompañada de un sonido de “tic”. Los interruptores de goma conductora generalmente tienen dos estructuras. La curva de fuerza operativa varía mucho con la geometría del bloque de caucho.
Humedad relativa: <95%
Voltaje nominal: 12V
Corriente nominal: 50mA
Temperatura: -25~70℃

Aplicación del interruptor táctil
TV a color, TV en blanco y negro, equipo de audio, grabadora de video, cámara de video, computadora, máquina de juegos, máquina de fax, walkie-talkie, bastón, dispositivo de control de máquina herramienta, fotocopiadora, impresora, instrumento electrónico, medidor y otros electrodomésticos.
Comportamiento mecánico:
Fuerza de funcionamiento: 1N, 1,6 N, 2,5 N;
elasticidad (control interno);
Cambiar la vida: 300.000 veces, 500.000 veces, 1 millón de veces.

Rendimiento eléctrico:
Resistencia de contacto: 100mΩ (real <20mΩ);
Tiempo de fluctuación: 5ms (real <1ms);
Vida útil del interruptor eléctrico: 300.000 veces, 500.000 veces, 1 millón de veces.

Performance test of tact switch
Mainly test the solder resistance, cold resistance, temperature resistance and humidity resistance of light touch switches.
1. Solder resistance test:
1. Solderability test of tact switch:
Method: Soak the soldering pin into the tin pool about 2mm deep, the test temperature is about 230±5℃, and the holding time is 3±0.5 seconds.
Result: More than 80% of the soaked solder fillets will be covered by tin.
2. Solder resistance test:
Method: The temperature of the solder in the soldering furnace is controlled at 260±5°C, and the time of the furnace soldering is kept at 5±1 seconds (substrate)
When hand soldering, the temperature is controlled at 350±30°C, and the time is 3±0.5 seconds, but abnormal pressure cannot be applied to the soldering feet.
Result: The switch has no deformation and can meet the electrical performance. Application of abnormal pressure voids the result.
2. Cold resistance test of tact switch:
Method: Place it in a temperature environment of minus 20±3°C for 4 days, then put it in a normal environment, and test it after 30 minutes.
Results: The contact resistance and insulation resistance were within the standard range, and there was no sign of damage to the switch performance.
3. High temperature resistance test of tact switch:
Method: Store the product at 280±30°C for 2-3 minutes, take it out, and test its feel and resistance after cooling down.
Result: resistance, gram force rebound, shape, etc.; none showed any signs of damage. The performance of the switch is still intact
4. Humidity resistance test of tact switch:
Method: Put it in the environment of 40±2℃, 90-95% RH for 4 days, then put it in the normal environment, and test it after 30 minutes.
Results: The contact resistance and insulation resistance were within the standard range, and there was no sign of damage to the switch performance.
5. Temperature alternating test of tact switch
In different temperature environments, after five cycles, put it in the normal environment for 30 minutes before testing;

The contrast and difference of tact switch
The tact switch mainly includes: stamping-injection molding-cleaning-assembly-molding-inspection and other processes. The process of membrane switch is mainly: screen printing – die cutting – assembly – testing and other processes. Both have very high requirements on the production environment. Relatively speaking, the use of workshops with higher dust-proof levels will guarantee product quality. Membrane switches require high precision and precise coordination of parts, and are also very picky about the appearance and color of the product. The tact switch requires a higher degree of precision, because the cooperation of various parts directly affects the performance and feel of the product, and the requirements for the performance of the product are very high. But the appearance and color of the product are not as picky as membrane switches. The cost and price of light touch switches are relatively low, and there will be no major price adjustments due to fluctuations in raw materials in the market; while membrane switches are relatively expensive and bulky, and are greatly affected by raw material prices. Tact switches and membrane switches are both functional switches. The light touch switch is used when the switch button is lightly pressed to turn on the switch, and the switch can be turned off when the hand is released. Its internal structure is realized by the spring of the metal shrapnel under force. Membrane switch is a key switch with its own circuit. Usually the uppermost layer is a panel with text or patterns composed of materials such as PET or PC. The lower layer is the conductive line. The middle layer is in the form of an analog switch and acts as an isolation, double-sided adhesive made of PET material. The bottom part is usually the contacts and connecting lines on the PET material. When the key position of the surface layer is pressed with a finger, the key contact point contacts the corresponding part of the contact point of the lower layer position to form a current connection.
The light touch switch is small in size and is a standard part. The size and related parameters must be combined with industry standards, and the color is relatively simple. Membrane switches can be customized in different sizes, appearances and colors according to customer requirements, which are more convenient and flexible to use. The membrane switch has good flexibility, closed structure and waterproof structure, and better adaptability to the environment. The light touch switch cannot produce functions independently, and must be used in conjunction with the PCB circuit board to form a complete opening control system. The membrane switch integrates the panels, switches, and conductive lines together to form a complete control system independently, and can provide customers with an overall switch solution.

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