1. Graphic overlay
Printing color ink to transparent polymer back, once the screen completed and cut into shape. As a result, this layer becomes a color membrane layer, the graphic overlay is an integral part of the membrane switch. Because it can show the function, color, membrane type an operation position of the switch. It also plays a protective role.
1.1 Membrane material
First, our factory bases on the engineer’s previous experience. Then, we verify the user details. Finally, they will recommend several membrane materials. Most of them use polyester materials. There are three main materials that you can choose. In short, their related characteristics are as follows:
|Polyvinyl chloride (PVC)||Polycarbonate (PC)||Polyester (PET)|
|Chemical corrosion resistance||very good||general||good|
|Insulation performance||very good||poor||good|
|Window transparency||general||good||very good|
|Drum resolution||good||very good||very good|
|Temperature level||There are restrictions when pressing the drum||good||good|
1.2 Important design considerations
Each color (including background color) requires a different screen printing operation. What’s more, we print color inks on the lower surface of photosensitive materials. Color sorting, ink blending, and screen preparation required for each operation. Also, color has a certain effect on the price of the switch.
(1) A high-definition scanner can scan the original image and various logos. In short, high quality and high contrast “original maps” can reduce working hours.
(2) Customers provided the original drawing is helpful for the designer of our factory. When we gain the original drawing, it will be easier ensure quality and efficiency. Frist, we will take action on basis of the customer requirements and color labels. Then, our factory modulates ink color.
(3) Every line in the membrane drawing should be clear and coherent. Otherwise, it will bring great difficulties to silkscreen printing.
2. Circuit layer
Printing conductive silver ink on a non-conductive polyester material made the circuit layer. Since the representative polyester materials have high performance and strong thermal stability. Our company can also provide circuit boards of other boards.
The carbon layer provides more protection to the exposed circuitry. If necessary, the circuit also needs to insulate the UV insulation oil. Although the circuit between the two sets of cross lines through the bridge. But, the circuit often needs the UV insulation oil as Insulator. To prevent the line from being oxidized. Likewise, to prevent the conductive silver falling off. UV insulation oil should be applied as protection.
A simple circuit diagram only needs to use one complete single loop without the need for a bridge. Individual schemes can use with a single loop for complex wiring diagrams. With the constraints of the customer’s design, more complex wiring diagrams are created. The designer of our factory will provide the most reasonable solution for the engineer.
2.1 Double-chip circuit
This circuit is mainly used for matrix and x-y conversion output. The connection of one membrane switch panel is located on the lower line, and the other is located on the upper circuit layer.
2.2 A single piece of circuit with a bridge
When the two sets of lines cross, silk-screened UV ink should be printed between them. This the process will increase screen times, the cost will also increase. When designers redesign lines, they should try to avoid line crossings.
2.3 Double-sided PCB circuit board
Like the characteristics of the line can also be made on rigid PCB materials. The connection of the line is from one line plane to the other, and the trimming and silk screening process is also a necessary part of this technology.
3. Membrane switch outgoing line
The lead wires of one or more flexible circuit loops for connecting the connectors. This line can carry many loops, according to its width and slope areas need. Above all, our factory is in a leading position in the requirements of inclination.
3.1 Common misunderstanding
The lead wire is an independent and complete circuit that is led out by one or more circuit loops in the film. If the length of the lead wire is changed, it has a certain influence on the performance of the membrane switch. While, if you want to increase the performance of increasing the length of the lead wire. Then, you can achieve by increasing the width of the lead wire.
3.2 Design considerations
For each project, our company will design the lead line. According to the following factors:
(1) Circuit structure.
(2) The connector used by the customer.
(3) Requirements for shielding layer and coupling.
(4) Design of mechanical structure to ensure the perfect connection with other components.
(1) The lead wire cannot be folded at will, or the bending radius exceeds 2.5 mm.
(2) If the customer need the lead wire bending. Then, our company will provide reliable pressure and high temperature setting.
(3 )The lead wires do not have to be cut into straight lines. Likewise, they can trim into various shapes to meet the requirements of different assemblies.
(4) Since the lead wires are the extension portions of the circuit layers, they cannot leave below the switch contacts.
(5) Line insulation options:
The carbon protective layer is used to prevent silver oxidation. Similarly, the carbon protective layer ensures good connection between the line and the pin. What’s more, costs of printing on insulating wires with insulating oil is lower. In addition, our company will provide a layer of polyester to seal the conductive lines to ensure static and prevent wear.
Connectors, also known as connectors, are a major category of electronic components. Our membrane keypad is different from the common plug-in components on the market. because they have four differences. First at all, the limitation of the lead wire distance is special to other products. Secondly, the number of the lead wire is a special make. Third, the connection method is an original idea. In the end, the plugging force has a great difference. The user of the membrane switch is difficult to buy in the market. To this end, our company provides the user with the performance, characteristics, parameters. So when we obtained relevant data of the user in advance to make the product more perfect. Users can also choose the connection form that conforms to the product attributes (including high reliability, easy replacement, economy, etc.). According to the characteristics of their products, propose matching requirements for our company.
5. Connector type
It is a one-piece connector. The shape is like the socket, the lower end is a pin, which is directly soldered to the circuit board. And the upper end of the socket inserted into the film lead tape. The installation is directional, preventing the line sequence from reversed. Not applicable to the lead of the two-piece membrane switch.
Disadvantages: Frequent insertion and removal of conductors that may damage the leads.
Scope of application: It is popular and suitable for general electronic products.
(2) Locking type
Features a locking mechanism with a tensile strength of 40N or more
Two locking holes need to punch on the lead tape, which is inconvenient to install.
Scope of application: for products with anti-vibration requirements
(3) Rivet type
The metal rivet pin riveted to the film lead by a special riveting tool. and the rivet pin connected with the circuit board. There is no special socket, and the IC socket can use instead of directly soldered to the circuit board.
Disadvantages: Installation by welding is quite inconvenient.
Scope of application: It is cheap and suitable for low-value civilian products.
The metal hole terminal is riveted to the film lead tape by a special riveting tool, and is equipped with a corresponding molded case socket, and can be inserted and removed with the pin on the circuit board.
Disadvantages: The number of insertions and removals will be loose, which will affect the contact effect.
Scope of application: a wide range of applications
(5) 2-36 line FCI plugin
It is used for the localization of imported membrane switches and some of the more demanding membrane switches.
Scope of application: Suitable for high-end electronic products with high reliability.