Material type of membrane switch
Polyvinyl chloride (PVC) \ 60 ℃ \ 0.175 ~ 0.5/Smooth surface \ Stable to acid, alkali and salt at room temperature. It is of good wear resistance and flame resistance, self extinguishing, noise elimination, shock absorption and good electrical insulation, but poor thermal stability, low-cost common plaque and panels.
Polycarbonate (PC) \ - 60 ~ 120 ℃ \ 0.175 ~ 1.0 \ Smooth surface has the characteristics of high transmittance, low water absorption, good dimensional stability, excellent bending, tensile and compressive strength, excellent heat resistance, cold resistance, electrical insulation and atmospheric aging resistance, and poor drug resistance, poor fatigue durability and easy to produce stress cracking. The circuit of output interface terminal is generally made of carbon material and printed without protective coating. It is oxidized by air to form falling off layer gradually, which eventually leads to open circuit and the end of service life. This is where the membrane switch most likely to fail. It is mainly determined by the environment. Whether it is used or not, the physical damage time is 3 -10 year. Generally, it has the most extensive application range. In addition to meeting the requirements of most membrane switch panels, the high transmittance of glossy PC can meet the requirements of LCD windows.
Sanded polyester (PET) \ - 30 ~ 120 ℃ \ 0.1 ~ 0.2 glossy, which with good drug resistance, insoluble in general organic solvents, and alkali nonresistant. It has excellent mechanical properties, electrical properties, rigidity, hardness and the largest strength and toughness of thermoplastic, low water absorption, excellent wear resistance and friction resistance, and high dimensional stability. The tensile strength is on a par with that of aluminum membrane, much higher than that of PC and PVC. Because the surface is difficult to be processed into Matte type, it is cheaper and is the most ideal substrate for making membrane switch circuit. Among them, the textured PET which is more expensive is suitable for products with high surface requirements or LCD windows.
Material thickness of membrane switch
The plastic base material whose thickness is 0.25mm or less is called membrane. It is mainly used as the panel layer of membrane switch. The back of the panel is printed with various indicative patterns and words to indicate the operation area of the corresponding switch key position. The thickness selection depends on the size of the panel and the key. If the material is thick, the contact force is increased, and the response is slow; contrarily, the touch feeling is poor, and the resilience is not obvious. The plastic base material whose thickness is 0.25 mm or more is called plate, which is not suitable for forming solid key and it can be used as an indicative sign panel in the operation area without keys, or as a lining plate of membrane switch to improve its hardness.
Circuit layer substrate of membrane switch
The base material for making circuit shall be Polyester (PET) membrane. It has good insulation and heat resistance, high mechanical strength, transparency and air tightness, especially good fracture resistance and high elasticity. It is an ideal material for making membrane switch circuit.