Silver Flex, Flex Copper Circuit and Printing Circuit Board, which is the best choice for Membrane Switch?
Membrane switch is an excellent HMI. Through reasonable design, the product can not only be used in the navigation, military and even aerospace industries. What kind of Membrane Switch is a good product? Niceone-Keypad believes that the Membrane Switch, which can meet the actual needs of customers, can improve the efficiency and cost-effectiveness of operators, is a good HMI. Among them, Membrane Switch has three larger categories, Silver Flex Membrane Switch (PET Circuit Membrane Switch), Flex Copper Membrane Switch (FPC Membrane Switch), Printing Circuit Board Membrane switch (PCB Membrane Switch), and their advantages are different. Use The regions are also different. So who is the best choice? In order for you to make a choice, we have listed their respective characteristics and advantages.
1. What is Silver Flex Memrbane Switch?
The circuit of this kind of Membrane Switch uses Polyester front printing silver oil, carbon oil, and UV ink is called Silver Flex Membrane Switch (PET Circuit Membrane Switch). The resistance is generally less than 150 ohms. It is also possible to increase the silk screen space of the circuit by filling holes or jumping bridges to complete more complicated circuit strokes, but the resistance will increase a lot. The Silver Flex Membrane Switch can meet most of the use environments. The Silver Flex Membrane Switch has the prominent advantage of being affordable and cost-effective. Conventional thickness selection: 0.1-0.125mm.
2. What is Flex Copper Circuit Membrane Switch?
The circuit of the Membrane Switch uses PI to cover the copper foil and then uses etching technology to expose the copper foil and gold plating to form a complete circuit. It is called Flex Copper Circuit Membrane Switch. Because the circuit is copper foil, the resistance is less than 30 ohms, because you can use double Panel, or multi-panel method to increase wiring space. A complex electronic circuit stroke is formed in a small enough area, and the resistance will not increase. The Flex Copper Circuit Membrane Switch can operate very well even in harsh environments. Conventional thickness of the substrate: between 0.125-0.188mm. Common structural design:
- Single-sided – conductive traces one side of the film substrate
- Double-sided – conductive traces both sides of the film substrate
- Multi-Layer flex – a laminated “sandwich” of numerous layers with conductive traces
- Rigid-Flex – a laminated combination of a Copper Flex switch with a rigid FR4 PCB membrane switch
3. What is Printing Circuit Board Membrane Switch?
PCB Membrane Switch mainly uses a printed circuit board made of cloth/fiber and resin material. There are many types of laminates such as FR-4, CEM-4, G10, etc., but FR4 is relatively cost-effective and the most commonly used choice. Use acid-resistant welding layer technology to etch the exposed area only to protect the required lines and then plate the gold where needed, and the thickness needs to be determined according to the actual situation. PCB circuit has most of the characteristics of FPC circuit, but the thickness is relatively thick. It can also complete a more complicated line stroke in a narrow space, and the resistance is relatively low. It can also complete electronic instructions well in harsh environments. At the same time, PCB can weld more electronic components than FPC circuits.
Since most of the design and situation of Silver Flex Membrane Switch and Flex Copper Circuit Membrane Switch are similar, Niceone-Keypad hopes to put them together.
4. What are the common features of Silver Flex Membrane Switch and Flex Copper Circuit Membrane Switch?
One of the most obvious characteristics of Silver Flex Membrane Switch and Flex Copper Circuit Membrane Switch is that it is particularly thin and aesthetic. But this is only part of their many advantages. Unlike the mechanical switch, which is composed of copper and plastic, the printed circuit on the polyester of the Silver Flex Membrane Switch and the Flex Copper Circuit Membrane Switch are switches formed by etching the PI exposed copper foil. At the same time, the thickness range of Membrane Switch is between 0.5-2.0mm due to different structures, which is why this type of switch is called Membrane Switch.
The advantage is: save a lot of design space.
- Easy to clean
Another feature of Silver Flex Membrane Switch and Flex Copper Circuit Membrane Switch is that it is easy to clean. The main reason is that the Membrane Switch has a low profile surface and there is no gap problem. At the same time, the waterproof level of most Membrane Switches has reached IP65. Therefore, even the water impact of low water pressure will not have any functional impact on the Membrane Switch that reaches IP65.
The advantage is that even long-term use of dust particles will not cause additional damage to the Membrane Switch. If you choose the right material or even wipe with alcohol, the chemical substances will not have any effect on the Membrane Switch.
Below is the cleaned membrane switch. No matter the load, the surface thickness does not change much.
- Low cost
Compared with complex touch screens and expensive electromechanical switches, the cost of these two Membrane Switches is greatly reduced. And can meet most of the needs. But relatively speaking, most of the time the price of Flex Copper Circuit will be 50-60% higher than the price of Silver Printing circuit.
The advantage is: To make the most suitable product with the most suitable cost is conducive to reducing the cost while completing more work.
5. Why did you choose the relatively expensive Flex Copper Circuit Membrane Switch?
It sounds like the Silver Flex Membrane Switch is not much different from the Flex Copper Circuit Membrane Switch. So why did you choose the relatively expensive Flex Copper Circuit Membrane Switch?
In the past ten years of production and communication with customers and users, I found that Niceone-Keypad summarized these points. This is also the limitation of Silver Flex Membrane Switch, which makes the electrical performance unable to compare with Flex Copper Circuit Membrane Switch. . So even if it is expensive, we must choose Flex Copper Circuit Membrane Switch.
- Unable to lay out more lines in a limited area: Although the Silver Flex Membrane Switch can lay out more lines in the form of Bridging, if there are too many lines, you need to consider the Flex Copper Circuit Membrane Switch. Mainly out of two considerations: 1. Bridging will increase the resistance of Membrane Switch, which will cause circuit conduction problems. 2. It is not possible to lay out the circuit through Bridging, then you need to use a double panel or even a multi-panel for circuit layout. At the same time, Membrane Switch has more functions, most obvious when the product is small.
- The product needs to be used in extreme environments: If the product is a military product, the Membrane Switch is often used in deserts, under snow, or under high-frequency vibration. We would recommend Flex Copper Circuit more. Because Flex Copper Circuit can withstand extreme temperatures and high frequency vibration. However, electronic components such as LEDs that use conventional Polyester Circuit with high frequency vibration will be easier to peel off.
- When the product needs higher waterproof performance: Membrane Switch needs to consider how to be waterproof when used in the marine industry, food industry, and outdoor use. Due to the high humidity of offshore operations, some electronic devices in the food industry need to be cleaned frequently and kept clean, but outdoor use is mainly a rainy problem. So how is the conventional Membrane Switch waterproof? First, you can use Adhesive with better viscosity, second, choose Water Proof structure, and third, choose Flex Copper Circuit or Printing Circuit Board instead of Silver Polyester Circuit. Because the first two are fixed, but the third point allows The reason for the higher level of waterproof performance is to keep the line away from the edge, which means a higher safety distance. This is also a waterproof frame Membrane Switch designed by Niceone-Keypad for a marine company. In fact, the Membrane Switch must reach IP67, and the waterproof frame must be at least 3mm. However, due to space limitations, only 2.2mm PET is used at the beginning, and FPC can be used later. Up to 3mm. This is why Flex Copper Circuit should be considered when products need higher waterproof performance.
- High voltage and humid environment: The most dangerous place of high voltage and humidity is that it is easy to cause silver migration to the Silver Flex Membrane Switch. So in this kind of environment, you can consider Flex Copper Circuit or Printing Circuit Board instead of Silver Polyester Circuit. But if it can solve some problems, Silver Flex Membrane Switch can also be used.
- When the lead wire of the circuit is longer: When the lead wire of the Silver Flex Membrane Switch is larger than 150mm, the resistance is higher. When the Silver Flex Membrane Switch has LEDs that need to be lit, the LEDs will have low luminosity due to high resistance. When the resistance of the Silver Flex Membrane Switch is too high, the electronic Buttons will not be so sensitive. If the keys are not sensitive, it will lead to lack of functions, causing industrial accidents or medical accidents. So when the lead wire of Membrane Switch is larger than 150mm, Niceone-Keypad will recommend Flex Copper Circuit Membrane Switch.
- Need to weld more diverse components: Most of the time, the Silver Flex Membrane Switch can only weld LEDs and cannot weld all kinds of electronic components such as resistors, capacitors, sensors, etc. like Flex Copper Circuit. But when the product needs Membrane Switch to weld various electronic components, then Flex Copper Circuit Membrane switch will be selected instead of Silver Flex Membrane Switch. Copper Flex keyboard also has the ability to combine active and passive components The advantages of hard soldering into components make it an ideal choice in high-vibration and high-reliability environments.
- Need for higher reliability: Although no exact data is available to determine the reliability impact or life expectancy between the two designs, the feedback received indicates that the FPC design provides substantial reliability improvements. Specifically, the combination between the circuit pad and the two-color LED was improved by switching to the FPC design. Field data showed that the open circuit failure of this component was significantly reduced.
Extended knowledge: What is silver migration, why it occurs and how to prevent the silver migration problem of Membrane Switch?
In Membrane Switch, the silver paste and membrane switch after screen printing will cause the silver oil of Polyester Circuit to migrate around after long-term use. At the same time, under high pressure, high humidity and high temperature environment, this kind of situation will also occur in silver oil.
One often occurs in high voltage (the electric field potential difference, the higher the voltage, the more likely to cause such problems), and the second occurs in a humid environment. The third is due to the high temperature. Fourth, consider the impurity of Polyester and silver oil.
- Avoid using under high pressure, high humidity and high temperature environment.
- Choose a better Polyester such as DK10, DK11 is a good choice.
- Choose a better silver oil ink.
- Select Flex Copper Circuit or Printing Circuit Board as the circuit. But the cost will increase relatively.
- It can increase the tightness of Membrane Switch. At the same time, adding carbon ink and UV ink to the silver oil at the Tail position will increase some resistance, but it is also a good solution for silver migration.
- Choose 2.54mm if the pitch is greater than 1.0mm.
Silver migration often occurs, and the damage to the product is great. Niceone-Keypad feels that if your product is unavoidable to use it in a high-pressure, high-humidity and high-temperature environment. The best option is Flex Copper Circuit even if the cost increases. This benefit can make your electronic products have a longer lifespan without electrical accidents.
So if the customer still needs to use the Silver Flex Membrane Switch and the lead wire is larger than 150mm, is there any way to alleviate the problem of excessive resistance?
The answer is yes.
- Silver oil needs ink with higher conductivity. In this way, the resistance will be relatively reduced by 10-15%
- The line width of silver oil is as wide as possible.
- Using nickel-plated or gold-plated Metal Dome will make Membrane Switch more stable.
- Reasonable route planning (professional engineers are required to design routes)
- Reduce the form of Bridging or perforation. Otherwise, the resistance will increase further.
Isn’t there any advantage to the Silver Flex Membrane Switch? Yes, the unit price of Silver Flex Membrane Switch is much cheaper than Flex Copper Circuit Membrane Switch if it can satisfy customers’ use.
Since Printing Circuit Board Membrane Switch and Flex Copper Circuit Membrane Switch have similar functions, the reason for using the basic selection is similar to that of Flex Copper Circuit Membrane Switch. Niceone-Keypad will not elaborate too much here.
6. What is the difference between Flex Copper Circuit Membrane Switch and Printing Circuit Board Membrane Switch?
When to choose Flex Copper Circuit Membrane Switch?
- When customers need to choose to bend the Membrane Switch slightly, Flex Copper Circuit Membrane Switch is a good choice.
- When the user needs the thickness of Membrane Switch to be thinner. Usually the circuit thickness of a single PCB will reach 0.4mm. Therefore, Flex Copper Circuit Membrane Switch is often chosen.
When do I need to choose Printing Circuit Board Membrane Switch?
- When the user needs a thicker Membrane Switch. Choosing the PCB Membrane Switch will reduce the cost correspondingly, because the thickness of the PCB can be selected thicker materials to save the cost of the back panel.
- A large number of electronic components need to be welded, but FPC cannot be welded, such as RJ45 connectors.
7. Some functional parameters of Silver Flex, Flex Copper Circuit and Printing Circuit Board?
- Tail width: Various types of customization can be made according to user needs, generally stainless steel molds or CNC molds are used for punching. PCB chooses a variety of connectors most of the time, but rubber cable is not the only choice. For details, please contact Niceone-Keypad.
- Tactile Feedback: Basically the same. Because it is not the line that affects Tactile Feedback. In fact, Metal Dome, Embossing shape, Tooling, design structure, etc.
- Circuit resistance: Most of the time, the circuit of the Silver Flex Membrane Switch is qualified as long as the product is less than 150 ohms. However, due to the customer’s cost budget and design issues, some Silver Flex Membrane Switches will not affect the use even if the resistance is greater than 150 ohms. The words are also acceptable. The biggest advantage of Flex Copper Circuit and Printing Circuit Board as a circuit is its low resistance. No matter how long the lead wire is, the resistance of both circuits can be controlled below 10 ohms. But the resistance and Metal Dome also affect each other. Generally, nickel-plated and gold-plated shrapnel are more helpful to stabilize the resistance.
- Ordinary trace width: The limit of PET trace width is 0.3mm. In Niceone-tech, the FPC PCB circuit width is normally 0.3mm. But the minimum limit width can be 0.08mm. But relative to the line width, the line width is actually better to choose as wide as possible. The main reason is the resistance problem.
- You can choose the shielding layer structure: ESD, EMI or RFI can be used in these three Membrane Switches. It can effectively prevent the loss of functions caused by static electricity on the surface of the membrane switch. Niceone-Keypad uses a shielding layer on the third layer of the membrane switch and leads out the ground wire. The main principle is to use the method of electromagnetic shielding to shield the electrostatic electromagnetic interference in the environment, thereby reducing and eliminating electromagnetic interference from space. It is also possible to use PI instead of a printed shielding layer or even a waterproof frame to form a closed loop to eliminate electromagnetics.
- Electrical performance: Loop resistance: The loop resistance of the switch is a function of the width and length of the trace. In most applications, the maximum loop resistance is less than 100 ohms. Open circuit resistance: 50 megohms minimum Contact rating: 100 mA, 28 VDC maximum Maximum load: 1.5 VA nominal Contact bounce: 5 ms nominal Operating temperature: -20°C to +75°C