1. There are two contact methods for the realization of the silicone button function
1) The silicone button is pressed on the DOME sheet (guozi sheet)
Usually used in mobile phones, children's watch mobile phones, waterproof mobile phones and other waterproof equipment.
2) The silica gel button adds a conductive base, a black conductive carbon particle, to achieve loop conduction
Usually used in remote control, computer keyboard, special equipment.
The structural design principles of the two methods are the same, and the fixation of the keys and the matching clearance and stroke must be ensured.
2. The structure of the silica gel remote control button (conductive base)
The button cap is made of large particles and solid, and the contact is a black conductive base, which is integrated by injection molding. So what should be paid attention to when designing this button structure?
The most important thing is the feel of the button press and rebound. Since there is no DOME chip to achieve rebound, the silicone design needs to rebound by itself. The detailed principle is shown in the figure below:
Note that when the button cap is pressed against the conductive base, a thin-walled inclined surface needs to be designed. The angle of the inner inclined surface is within 45 degrees, and the thickness of the inclined wall is between 0.3-0.6. Normally, 0.5. It should be noted that the opening under the conductive base is larger than the button cap.
1) The width of A should be 2 times larger than the width of B on one side of the size of C. If the thickness of C is 0.5, then the width of one side should be 1.0;
2) D is the pressing stroke, usually between 0.3-0.5;
3) The thickness of the black conductive base is generally about 0.4 to 0.6 mm.
The conductive base can be designed in any shape, and the conductive method of the conductive base can also be determined according to actual needs.
There are three main ways to conduct the conductive base of the silica gel button:
1) Conductive carbon particles realize the conductivity of the silica gel button remote control. The advantage of this kind of conductive method is that the conductive layer is thicker, usually about 0.4-0.6mm, and the conductive resistance is low, below 100Ω. However, the shape of the conductive base is required to be regular, usually 0.5 times a perfect circle.
2) The screen printing conductive carbon oil realizes the conductivity of the silicone button remote control. The advantage of this method is that there is no specific requirement on the shape of the conductive base and can be any shape. However, the thickness of the conductive layer is thinner than the conductive carbon particles, generally about 0.2 to 0.3 mm, and the conductive resistance is also relatively higher than that of the conductive carbon particles.
3) The conductive base is pasted with metal particles to realize the conductivity of the silica gel button remote control. The advantage of this kind of conductive method is that the conductive resistance can reach nearly 0Ω, and the surface of the metal particles is gold-plated, which can effectively resist oxidation. Like conductive carbon particles, metal particles require that the shape of the conductive base is usually 0.5 times a perfect circle with a thickness of about 0.2-0.5, but the production cost is much higher than that of carbon particles.
3. Pure silicone press DOME sheet
The contact design parameters of the silicone button contact and the DOME sheet are the same as the P+R button design parameters. The only difference is the thickness of the silicone at A, which is usually designed between 0.3-0.5. If the manufacturer says that it is too thin and difficult to form, it needs When it is increased to 1.0, the structure of the silica gel is changed to the same as a silica gel button with a conductive base.
It not only guarantees the strength of the molded silicone but also the feel of the buttons. This kind of pure silicone pressing button structure is usually used in the two-color injection waterproof button structure, but the material is changed to TPE or TPU. Or the DOME chip is replaced with mechanical key components, the specific method needs to be selected according to the actual situation.
4. Elastic wall hard rubber buttons
What is an elastic wall hard glue button?
Use one fulcrum or two fulcrums to make a long-distance rib position to realize elastic movement and realize the pressing function.
The elastic wall button is usually pressed on the mechanical button components, or on the DOME chip, or on the switch.
The components can already achieve the pressing function, and only a flat surface is required to contact with the structure design, and the structure of the button is also determined by the appearance design.
Scheme A: Double pivot elastic wall button
Two uniform elastic walls, with a circumference of 8-30, a thickness of 0.7-1.2, and a width of 2.0-3.0, are fixed on the shell material by two side hot melt columns.
This type of button has a relatively balanced feel when pressed, and the gap between the button and the shell material will be much more even after assembly. The disadvantage is that it requires enough space. The specific definition needs to be based on the actual space of the product. The longer the length, the smaller the pressing force. .
Scheme B: Single pivot elastic wall button
An elastic wall, wall force perimeter between 5-15, thickness between 0.7-1.2, and width 1.5-3.0, is fixed on the shell material by a hot melt column.
When this button is pressed, the feel is slightly shifted. You need to place the contact on the top of the arm. The farther the better, because when the button is pressed, the wall force with the link is greater than the force without the link. The touch will feel very blunt if the contacts are too close.
The second is the fit gap of the keys, the unilateral should be about 0.15-0.3 (excluding the key reduction and draft), otherwise, it is easy to jam the keys.
Solution C: One-piece elastic wall conjoined button
An elastic wall, the perimeter of the wall force is between 5-8, the thickness is between 0.7-1.2, and the width is 2.0-3.0. The key circle is hollowed out, and the hollowed-out width is between 0.7-1.5, which is defined according to the structural space.
This kind of button method only needs to ensure that the buttons are in contact with the components, and the hand feel is relatively balanced. The only disadvantage is that the button cap has a large slope, 5-7 degrees, and fits with the shell, with a large gap. It is usually used in displays. The bottom or the top of the electronic device, which is not directly visible.
Next, get to know the five-way swing button, one button can control 5 function keys.
This kind of button structure design only needs to make a card position and snap the swing head of the button into the button cap. There is no special fixing requirement. The only thing to pay attention to is that the swing head should have enough clearance with the surroundings during the swing, which is usually between 1.0-2.0, depending on the length of the swing head arm.
refer：
https://www.sohu.com/a/230255533_100121785
http://bbs.16rd.com/thread-465390-1-1.html