With the rapid development of science and technology, touch screen technology has been widely used in intelligent homes, public information query, multimedia information systems, medical instruments, industrial automation, entertainment and catering and many other fields. Touch screen as an interactive input device, the user only need to use a finger or light pen touch screen location can control the operation of the computer, its simple operation, the use of flexible features make more people use the computer.
However, the touch screen in the use of the process may encounter the problem of electrostatic discharge (ESD), static electricity in our daily lives everywhere, our body and around with a high electrostatic voltage. The hazards of static electricity have an impact on all walks of life, especially in electronic products, electrostatic discharge (ESD) problem is particularly prominent.ESD performance directly affects the electrical performance of electronic products and even service life. For the touch screen, electrostatic discharge may lead to touch ports, data transmission lines, power supply and shielding lines and other critical parts of the damage, thus affecting the stability and reliability of the product.
Anti-static design methods for touch panels
1. Protective measures at the design stage
1.1 Circuit design
Protection diodes: add transient voltage suppression diodes (TVS diodes) or electrostatic protection diodes on key circuit nodes to clamp the electrostatic voltage and prevent excessive electrostatic voltage from entering the circuit.
Filter circuit: design a suitable filter circuit (such as RC filter), slow down the rise time of the electrostatic discharge pulse, reduce its impact on the circuit.
Ground design: Ensure that the circuit board has a good grounding design to reduce the impedance of the electrostatic current path, to ensure that the static electricity can be quickly discharged.
Multi-layer board design: Using a multi-layer PCB board, the ground and power layers can be arranged separately to form a better electromagnetic shielding effect.
Shielding layer: Increase the shielding layer on the PCB board, especially in the critical circuit area, can effectively shield the electrostatic interference.
Signal line arrangement: the signal line is as short as possible and away from high electrostatic areas to avoid the formation of electrostatic coupling.
1.2 Physical structure design
Anti-static coating: coating the touch screen shell and key components with anti-static coating can effectively reduce the surface resistance and prevent static electricity accumulation.
Anti-static packaging: Use anti-static packaging materials (such as anti-static bags, anti-static foam) to protect the touch screen during transportation and storage.
Anti-static work clothes: Use anti-static work clothes and tools on the production line to ensure that operators wear anti-static hand rings and work on anti-static workstations.
Environmental control: Control the humidity of the production environment and keep it between 40% and 60% to help reduce the generation and accumulation of static electricity.
Conductive or anti-static materials: the use of conductive or anti-static materials to make the shell of the touch screen, can effectively prevent the accumulation of static electricity and discharge.
Metal shielding: adding a metal shielding layer inside the casing can shield the external electrostatic interference.
Good grounding: Ensure that the touch screen casing and internal circuitry have a good grounding design, so that static electricity can be quickly discharged through the grounding path.
Avoid high static environments: Try to avoid installing the touch screen in high static environments (e.g. near high voltage power lines or dry areas).
2. Electrostatic discharge test
In order to ensure that the anti-static design effect of the touch screen, need to carry out rigorous electrostatic discharge test. These tests are designed to ensure the stability and reliability of the touch screen in the actual use of the environment, to avoid failure or damage caused by electrostatic problems.
2.1 Electrostatic discharge (ESD) test
Human Body Model (HBM): Simulates the electrostatic discharge when a person touches the touch screen. Usually a few thousand volts of high voltage is applied to see if the touch screen can work properly.
Machine Model (MM): Simulates the electrostatic discharge when the machine or equipment touches the touch screen.
Charging Device Model (CDM): Simulates the electrostatic discharge when the touch screen itself is charged and touches other objects.
2.2 Air Discharge Test: Use an electrostatic discharge gun to discharge air on the surface of the touch screen to test its ability to resist electrostatic interference. The discharge voltage is usually between a few thousand volts and tens of thousands of volts.
2.3 Contact Discharge Test: The electrostatic discharge gun directly contacts the specified points of the touch screen for discharge to evaluate its anti-static capability and product reliability.
2.4 Static Induction Test: Simulate the working condition of the touch screen in the electrostatic environment to assess its ability to resist static induction.
2.5 Electrostatic shielding performance test: Detect whether the touch screen has effective electrostatic shielding ability to protect the internal circuitry.
The antistatic design of the touch screen is a comprehensive project involving circuit design, physical structure design, testing and verification and other aspects. By taking effective static protection measures at the design stage, such as adding protection diodes, designing filtering circuits, optimizing the ground design, using antistatic coatings and packaging materials, controlling the humidity of the production environment, etc., the damage caused by static electricity to the touch screen can be greatly reduced. At the same time, through strict electrostatic discharge test, can ensure that the touch screen in a variety of electrostatic environment, anti-interference ability to improve product stability and reliability.