Precautions for outdoor application of membrane switch
author: Joey
2022-12-28
Electronics and variable outdoor elements are notoriously poor mixes. Can't we just get along? Of course we can, just need some planning to make sure everyone is happy
Since the graphics are mounted on the front of the membrane panels, they are subject to a lot of abuse and are directly exposed to the elements. In almost all cases, people choose to use polyester over polycarbonate graphics because of its better flex durability (compared to tactile domes), chemical and abrasion resistance, and dielectric strength (used in for anti-ESD).
UTC manufacturers produce graphic polyester grades with special textures to resist scuffs and scratches. Other grades protect against extreme temperatures, high humidity, and the sun's harsh UV rays. UV protection helps graphic and clear windows maintain their clarity and color by resisting fading or yellowing over time.
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The body of a membrane switch consists of a layer of PSA (pressure sensitive adhesive). If the edges of these layers are exposed to elements (water, liquids, dust, etc.), these elements may pass through the layers, and fluctuations in temperature and humidity will accelerate this. If the part is outside, this needs to be taken into account during the design process. One solution is to use a shim material to protect the edge of the switch; preferably the most aggressive adhesive available if possible. In this regard, VHB (Very High Bond) tape can serve as a good sealing mechanism, but the correct VHB and thickness must be chosen to adhere to the switch and case. Correct choice of adhesive is necessary to protect electronics!
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It is critical to consider the position of the tail on the switch and the housing. Any design engineer would recommend designing the tails inside the part, meaning the tails and the conductive circuitry are printed on the same piece of polyester. If glued tails are preferred, it is recommended to use gaskets or consider filling the tail slots in the housing with RTV (room temperature vulcanizing) silicone to keep contaminants from reaching the electronics.
An improved gasket replacement is to provide a heat seal adhesive that removes any air trapped between the layers. The bond should "wet out" and provide an interface that keeps contaminants away from the switch. This process adds cost, but it can be good insurance when parts must be placed outside.
Since the graphics are mounted on the front of the membrane panels, they are subject to a lot of abuse and are directly exposed to the elements. In almost all cases, people choose to use polyester over polycarbonate graphics because of its better flex durability (compared to tactile domes), chemical and abrasion resistance, and dielectric strength (used in for anti-ESD).
UTC manufacturers produce graphic polyester grades with special textures to resist scuffs and scratches. Other grades protect against extreme temperatures, high humidity, and the sun's harsh UV rays. UV protection helps graphic and clear windows maintain their clarity and color by resisting fading or yellowing over time.
cloud
The body of a membrane switch consists of a layer of PSA (pressure sensitive adhesive). If the edges of these layers are exposed to elements (water, liquids, dust, etc.), these elements may pass through the layers, and fluctuations in temperature and humidity will accelerate this. If the part is outside, this needs to be taken into account during the design process. One solution is to use a shim material to protect the edge of the switch; preferably the most aggressive adhesive available if possible. In this regard, VHB (Very High Bond) tape can serve as a good sealing mechanism, but the correct VHB and thickness must be chosen to adhere to the switch and case. Correct choice of adhesive is necessary to protect electronics!
shield
It is critical to consider the position of the tail on the switch and the housing. Any design engineer would recommend designing the tails inside the part, meaning the tails and the conductive circuitry are printed on the same piece of polyester. If glued tails are preferred, it is recommended to use gaskets or consider filling the tail slots in the housing with RTV (room temperature vulcanizing) silicone to keep contaminants from reaching the electronics.
An improved gasket replacement is to provide a heat seal adhesive that removes any air trapped between the layers. The bond should "wet out" and provide an interface that keeps contaminants away from the switch. This process adds cost, but it can be good insurance when parts must be placed outside.
As mentioned earlier, the printed circuit is only one layer that makes up a membrane switch. With experience in all stages of manufacturing high-quality membrane switches, UTC is your one-stop partner. In addition to printed circuit layers, we can also assist with material selection, printed graphic overlays, assembly, and more.
Remember, these switches are sensitive electronic devices and are subject to damage from flexing, rough handling, or improper storage.If you need to use membrane switches in various complex situations, UTC engineering staff provides these recommendations as a basic set of guidelines for all membrane switch customers. There may be particularly complex switch designs that require additional handling or storage precautions. UTC will provide its customers with additional advice as required.
