design of silicone keypads for hazardous or difficult situations
I have listed here some of the main design factors that can be used to protect the keyboard and the instruments it operates on.
Us ul-if necessary-
Use 94 specifications.
Most silicone rubber will reach UL-94-HB.
In short, this specifies the rubber, and if ignited in a horizontal position, will
Go out quickly.
Most silicone rubber is hard to burn in nature.
The more stringent specification is UL-94-V1.
At this level, the specification requires that when in a vertical position, the rubber does not continue to burn when ignited, and the residual fire does not continue to shine at any time.
This is a tough game. ©The cis of UL specification introduces the testing system in detail. If the UL-94-
Grade V1 is required and must be aware that this has an impact on other physical properties as the polymer must be loaded with flame retardant.
This usually breaks down into the ability to resist water entry or UV rays.
Water is prevented from entering the contact area of the PC board by simply installing a mechanical compression seal around the keyboard, thus achieving waterproofing.
Make a compression seal, a bead around 0.
The surrounding radius is 5mm M, compressed and sealed.
Alternatively, a raised bead can be added on the lower side of the face.
If there is no sealing surface, then bonding the keyboard to the PC board with a double sided adhesive may be the best way to seal.
The effects of UV rays can cause discoloration of pigments used in silicone rubber and legendary inks.
The base polymer silicone has excellent UV resistance.
If the keyboard will be used outdoors, especially in a sunny climate like California, then this should be clearly stated on the drawing.
Electrical problems if static electricity has the risk of damaging electrical components, then there will be anti-static electricity
The static grade of the silicone should be specified as this will prevent the accumulation of charge.
It is feasible to make the keyboard conductive, because the extra load of the conductive additive will reduce the physical performance.
In general, silicone rubber does not resist the continuous contact of oil and solvent, although there is no problem with the usual alcohol, it can be expected to degrade.
If the presence of a solvent is inevitable, different polymers should be considered in addition to silica gel.
Fluorine silicone rubber is effective for many solvents.
This has a disadvantage as a keyboard because it can\'t be printed.
A certain degree of solvent resistance is achieved by spraying the keyboard with polyurethane or parylene coating.
Parylene coating is an expensive process that doubles the price of a silicone keyboard.
VandalismI heard that the worst thing about the silicone keyboard is the control panel next to the first class seat on a long flight and passengers have enough time to fiddle with it!
Keys can be distinguished by nails or birds.
The solution to this problem is to protect the key with a plastic or metal cover.
The cap can be provided as a component with a keyboard or can be designed under facia.
If impact damage is to be prevented, the key to the cap should be limited by the design.
The PC board should be very strong or supported below by a metal plate.
I hope it\'s an unusual danger.
One of the cases that we had to design before was when the predicted bomb exploded, the keyboard used on the battlefield. The problem (only problem! )
Heat flashes can cause certain legendary pigments to absorb heat and burn.
The answer is to use colors and pigments that are not easy to absorb heat.
I just hope the operator is also heat resistant.
These notes are just an auxiliary memoir to show some questions and possible solutions.
I believe there are more problems and situations, and there are more ways to solve them.