Electrostatic discharge (ESD) is what causes you to feel a shock when you first touch someone or something – your body generates and stores electric charge until you touch something that gives it the opportunity to discharge the built up energy. A person walking across a carpeted floor can generate up to 25,000 volts (25kv), even walking across vinyl tiles can generate and store several thousand volts in your body. Now imagine the next thing you touch is your microwave touch keypad, the charge may be transferred to the switch, this discharge may cause damage to the components within the assembled circuit if it is unprotected.
Fun fact: You can’t even feel an ESD shock when you touch something unless it is at least 4000 volts (4kv).
Preventing ESD from reaching an integrated circuit is critical, membrane switch manufacturers take ESD into consideration when designing parts by adding shielding into the switch. This ESD shield is conductive material that is between the circuit and the front of the product. Before production, an ESD simulator or discharge gun can be used to determine the effectiveness of the ESD shield on a membrane switch. Programmed voltages can be applied to the face of a switch while the circuit is monitored for any activity which may have been caused by the electrostatic discharge.
Check out this video of the ESD testing gun in action (don’t blink, it goes quick, even in SloMo)!
The ESD shielding is connected to earth ground in the customer’s final assembly. If someone with a charge would touch the switch, the electrostatic discharge would travel to the shield and then to earth ground – the discharge would not penetrate through to the internal electronic circuit board. This shielding protection is designed the same for indoor and outdoor applications. So next time you send some ESD into an electronic interface and it still functions properly, I’d be shocked if it wasn’t shielded.
Do you have an HMI that needs ESD protection? We’re here to help!