Test Specification of LCD Display
LCD Display, full name of Liquid Crystal Display, is a flat display technology. It mainly uses liquid crystal materials to control the transmission and blocking of light, so as to achieve the display of images. The structure of the LCD usually includes two parallel glass substrates, with a liquid crystal box in the middle, and the polarized light of each pixel is controlled by the rotation direction of the liquid crystal molecules through the voltage, so as to achieve the purpose of imaging. LCD displays are widely used in TV, computer monitors, mobile phones, tablet computers and other devices.
At present, the common liquid crystal display devices are Twisted Nematic (TN), Super Twisted Nematic (Super Twisted Nematic), STN), DSTN(Double layer TN) and color Thin Film Transistors (TFT). The first three kinds of manufacturing basic principles are the same, become passive matrix liquid crystal, and TFT is more complex, because of the retention of memory, and called active matrix liquid crystal.
Due to liquid crystal display has the advantages of small space, thin panel thickness, light weight, flat right-angle display, low power consumption, no electromagnetic radiation, no thermal radiation, it gradually replaces the traditional CRT image tube monitor.
LCD displays basically have four display modes: reflection, reflection transmission conversion, projection, transmission.
(1) The reflection type liquid crystal display itself does not emit light, through the light source in the space into the LCD panel, and then by its reflective plate will reflect the light to the eyes of people;
(2) The reflection transmission conversion type can be used as a reflection type when the light source in the space is sufficient, and the light source in the space is used as lighting when the light is not enough;
(3) Projection type is to use the principle of similar movie playback, the use of projected light department to project the image displayed by the liquid crystal display to the remote larger screen;
(4) The transmission type liquid crystal display completely uses the hidden light source as lighting.
Relevant Test Conditions:
Item
Temperature
Time
Other
High temperature storage
60℃,30%RH
120 hours
Note 1
Low temperature storage
-20℃
120 hours
Note 1
High temperature and high humidity
40℃,95%RH (non-invasive)
120 hours
Note 1
High-temperature operation
40℃,30%RH.
120 hours
Standard voltage
Temperature shock
-20℃(30min)↓25℃(10min)↓20℃(30min)↓25℃(10min)
10cycle
Note 1
Mechanical vibration
—
—
Frequency: 5-500hz, acceleration: 1.0g, amplitude: 1.0mm, duration: 15mins, twice in X,Y,Z direction.
Item
Temperature
Time
Other
Note 1: The tested module should be placed at normal (15 ~ 35℃,45 ~ 65%RH) for one hour before testing
Instructions:
Early temperature cycle tests only look at the air temperature of the test furnace. At present, according to the requirements of relevant international norms, the temperature variability of the temperature cycle test refers not to the air temperature but the surface temperature of the product to be tested (such as the air temperature variability of the test furnace is 15°C/min, but the actual temperature variability measured on the surface of the product to be tested may only be 10~11°C/min), and the temperature variability that will rise and cool down also needs symmetry, repeatability (the rise and cooling waveform of each cycle is the same), and linear (the temperature change and cooling speed of different loads is the same). In addition, lead-free solder joints and part life assessment in advanced semiconductor manufacturing processes also have many requirements for temperature cycle testing and temperature shock, so its importance can be seen (such as: JEDEC-22A-104F-2020, IPC9701A-2006, MIL-883K-2016). The relevant international specifications for electric vehicles and automotive electronics, their main test are also based on the temperature cycle test of the surface of the product (such as :S016750, AEC-0100, LV124, GMW3172).
Specification for the product to be tested surface temperature cycle control requirements:
1. The smaller the difference between the sample surface temperature and the air temperature, the better.
2. Temperature cycle rise and fall must be over temperature (exceed the set value, but not exceed the upper limit required by the specification).
3. The surface of the sample is immersed in the shortest time. Time (soaking time is different from residence time).
Thermal stress testing machine (TSC)of LAB COMPANION in the temperature cycle test of the product to be tested surface temperature control features:
1. You can choose [air temperature] or [temperature control of the product to be tested] to meet the requirements of different specifications.
2. The temperature change rate can be selected [equal temperature] or [average temperature], which meets the requirements of different specifications.
3. The deviation of temperature variability between heating and cooling can be set separately.
4. Overtemperature deviation can be set to meet the requirements of the specification.
5.[temperature cycle] and [temperature shock] can be selected table temperature control.
IPC requirements for temperature cycle test of products:
PCB requirements: The maximum temperature of the temperature cycle should be 25°C lower than the glass transfer point temperature (Tg) value of the PCB board.
PCBA requirements: The temperature variability is 15°C/min.
Requirements for solder:
1. When the temperature cycle is below -20 °C, above 110 °C, or contains the above two conditions at the same time, more than one damage mechanism may occur to the solder lead welding connection. These mechanisms tend to accelerate each other, leading to early failure.
2. In the process of slow temperature change, the difference between the sample temperature and the air temperature in the test area should be within a few degrees.
Requirements for vehicle regulations: According to AECQ-104, TC3(40°C←→+125°C) or TC4(-55°C←→+125°C) is used in accordance with the environment of the engine room of the car.
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