Attentions when using LCD
- Mar 29, 2018 -

               

1. To prevent excessive pressure: After the LCD is soldered to the circuit board, the LCD pin should not be subjected to force in principle, otherwise it may cause poor contact. If you must be forced, you must design a support leg that does not need to be conductive, or use a flexible, special-shaped leg, or use hard plastic to fix it.


2. Welding Notes: 1) The distance from the bottom of the glass to the soldering position of the PCB should not be less than 5mm, and the limit should not be less than 2mm. The soldering temperature is not higher than 260°C, otherwise the thermal shock of the liquid crystal panel will cause black spots in the molecular arrangement disorder. When the welding temperature reaches 350 degrees Celsius, a large proportion of black spots may occur after welding. And the welding time does not exceed 5 seconds in order to avoid burning the yellow polarizer. 2) Try not to stress the pins after soldering to avoid poor contact. If you must adjust the position of the LCD substrate or the pins, wait until the pins are naturally cooled to room temperature. Do not pull the LCD when it has not cooled down. 3) When welding the LCD, welders should wear finger covers or gloves to prevent hand sweat from corroding metal feet.


3. After the assembly is completed, the protective film on the polarizer must be removed.


4. Device moisture protection: 1) Since the LCD is low voltage and micro power consumption, the liquid crystal material has a very high resistivity of 10,000 megaohms. Therefore, the tiny conductive surface of the glass due to moisture will affect the display. 2) Do not condense moisture on the surface of the display screen. The condensation of water droplets on the surface of the display will cause the polarizer to be rapidly hydrolyzed, and the corners will rapidly decompose and decompose and spread to the center, resulting in failure to display.


5. Prevent scratches: As the LCD surface is a polarizer, it belongs to plastics. Therefore, the assembly and use should absolutely avoid scratching hard objects. There is a protective film on the polarizer on the LCD surface, and there is no protective film on the lower surface of the LCD without backlight, which is especially easy to be scratched.


6. To prevent the application of direct current: The smaller the DC component of the driving voltage, the better. It is better not to exceed 50mV or 1%. Applying excessive DC components for a long time will cause the liquid crystal to decompose and cause the electrode to electrochemically react and age. In the segment display, a frequency dividing circuit is often introduced in the oscillation circuit to ensure the square wave symmetry.


7. UV protection: All LCD screens in our company have UV protection function.


8. Use and storage within the specified temperature range: Since the liquid crystal state disappears beyond a certain temperature range, it must be used and stored within the specified temperature range. If the temperature is too high, the liquid crystal state disappears and becomes liquid. The display surface is black and does not work. Do not power on at this time. When the temperature returns to normal, the display surface will return to normal. If the temperature is too low, the liquid crystal state disappears and the ice becomes crystal. At this point it is possible to damage the alignment layer during the formation of crystals and cause permanent damage.


9. Prevent static interference: Due to the extremely low LCD operating voltage, the internal resistance is very large, and very little static electricity can cause display. Therefore, try not to put the LCD in an electrostatic environment. If you can't avoid it, you should design an anti-static circuit inside the LCD, or speed up the speed of the AC brush screen in the driver to eliminate static electricity.


10. The phenomenon of molecular diffusion: If the LCD screen shows, for example, a fixed content for a long period of time, say three to five years, then the molecular diffusion phenomenon will be formed, that is, there will be a distinct character in the display area. It is recommended that the program control let the LCD screen intermittently rest or refresh to avoid damage caused by keeping the posture for too long.


11. Low-temperature response speed: The lower the temperature, the higher the viscosity of the liquid crystal material, the slower the response speed and the longer the response time. For every 10 °C lower temperature, the response time will be extended by 3 times. Response time = rise time + fall time. When working at low temperature, the data refresh time of the driver should be greater than the response time of the LCD screen to ensure the normal display of the LCD screen.