Can you imagine if you carry a laptop around with a load of exposed wires? Luckily, someone invented printed circuit boards(PCB) to make our lives easier. It is, in fact, a wire wrapping technology. With this technology, at each connection point, it only needs a small gauge wire wrapped around a post. So the printed circuit board is more durable and changeable, and it can save a lot of space. Now PCB has become the premium solution for various electronic applications. Thanks to the PCB membrane switch, it makes our electronic devices smaller and more reliable.
What is a PCB membrane switch/ membrane PCB?
The printed circuit board works as rigid support and provides electrical pathways. And the circuit is integrated by the conductive copper traces, connecting varied electronic components. Normally, the substrate material is fiberglass, also know as” FR4”. As for the solder mask is acid-resistant and it is screen printed onto the cooper-clad, leaving exposed area etched away. But for the exposed copper area, it needs metal-plated protection from getting corroded. And the gold plated option is the best for some harsh conditions use.
This technology allows all the electronic components to connect internally without any wires. So PCB simplifies the integrated circuit design as well as the membrane switch design. Membrane PCB costs more, but it is able to accommodate more complex and dense circuit patterns. The PCB membrane switch construction utilizes PCB as a support, with the graphic overlay on the front and some displays assembly on the back. With the PCB designs, the membrane PCB can incorporate LED, LCD, resistors, diodes, and other components highly reliably.
Based on the type of the circuit layer, there are two other different types of membrane keyboards.
Silver flex membrane switches are silver flexible circuit based. As the poly layer is flexible, so it is well-known as the silver flex membrane. Generally, using silver ink printed onto the polyester layers can get a space-saving design. And the silver ink works as a very good conductive material.
Copper flex membrane switch construction utilizes copper flex circuits as the substrate, also noted as rigid flex circuits. It lets the thin copper sheet laminated to the flexible film (polyester and polyamide). Hence, this type is a standard rigid flex construction. And it is good for smaller designs when requiring dense circuit patterns within limited space.
PCB switch design options
PCB switch design combines the printed circuit board with graphic overlay perfectly.
For the part of graphic overlays (user interface)designs:
- The buttons on the graphic overlays can be pillow embossed, rim embossed or debossed.
- It can be digitally printed for sampling, while screen printed for production.
- Different textures and surface finishes are available.
- Incorporate LED and other display windows are also possible.
- It can have non tactile feel or tactile feel with polyester or metal domes.
For the part of PCB membrane switches designed options:
- It can be single-layered, double-layered or multi-layered.
- The metal plating options can be gold plated, nickel plated or tin-lead plated. With gold plated pads and domes the PCB membrane switches can have high reliability.
- SMT soldering (Surface mount technology) or through-hole mounting soldering? Surface mount technology will make the switch circuit board smaller with a low profile. And this type of soldering requires a high temperature. As for through-hole mounting, the integrated circuit will be bigger and easier to solder.
Dome switch PCB
Like the silver flex membrane switches, the PCB membrane switches can be tactile and non-tactile. With the tactile dome switches, you can get strong snap feedback. And The clicking feel is from the tactile dome, which is made of polyester or metal. Yet you can barely get a solid response with a non-tactile switch. And the metal dome switch PCB is more popular due to its crisp snap. For most uses, metal dome switch material is stainless steel. Moreover, metal domes are momentary switch contacts. When used together with membrane PCB, they work as open tactile switches.
The pressure-sensitive tape is perfect to place the tactile metal domes onto the PCB. And this is how open tactile switches work. When pushed, the tactile metal domes deforms to contact the secondary pathway to close the circuit. While released, the metal dome will snap back to its relaxed state to open the circuit.
Tactile dome shapes
The tactile metal domes can fit any custom size shape. And the professional manufacturer HaiSong industry can incorporate different shapes into a wide range of applications. The dome shape selection depends on the device types and the designs for the user interface. And here are four common shapes, round, four-leg, triangle, and oblong.
Circle metal domes
Circle metal domes are well-known for round metal snap domes. But they are only obtainable for two or more layers of circuit boards. Circle metal dome PCB takes less space than the four-leg domes, so it is good for compact PCB designs. And they have more extended life cycles compared with triangle domes.
Four-leg metal domes
Four-leg metal domes, also noted as cross metal domes are suitable to mount on single or double sided circuits. These circuits can be membrane PCB, FPC and silver flex membranes. And It is possible to place both negative and positive traces on the same side of circuits below the dome. Cross metal domes benefit rubber keypad with better tactile feel than round and oblong domes. As well They feature prolonging life cycles and the actuations can be over 1 million. Four-leg domes are a bit higher so they have very high trip forces.
Triangle metal domes
Triangle metal domes are common in dome switches designed for mounting on single or double sided circuits too. Only if there is a via running through the circuit layer. They are suitable for small, portable devices if requiring a good clicking feel. Also, the trip forces can be up to 6kg, so the triangle domes are ideal for heavy force PCB switch design. Plus, They fit for high temperature use too. As their legs can directly insert to the hole on the circuit layer with tape free.
Oblong Metal Domes
Oblong Metal Domes are in an oval shape. They are designed for mounting on the membrane switch circuit which is double sided. And the long, narrow space can benefit from this type of domes. Oblong metal domes are the perfect choice for a low profile tactile membrane switch too.
Some of the metal snap domes(momentary switch contacts) above are available for dome array. It helps to lower the cost and fasten the assembly time, which means shorter lead times. Dome arrays can offer the rubber keypad with good tactile feedback as well. Thus, they are the prime choice for membrane keyboards.
Advantages of the metal dome PCB membrane switch construction
- They can provide a strong tactile feel to indicate the user that the activation is completed.
- Qualified tactile metal domes allow the dome switch PCB to have the long-lasting life cycles. Especially when they are in use for the high temperature condition.
- They are available in various shapes and sizes to meet the demand for custom size shape.
- Varied actuation forces are possible to meet the custom specifications.
- Dome materials are optional, stainless steel, nickel plated or even gold plated are available for harsh environment.
To learn more about PCB membrane switch design and the construction, Contact HuaiSong industry now. As a professional manufacturer, we can provide custom membranes with high reliability to meet the specific needs. Good service, high quality, short lead times, you can always find what you need here.