LCM product inspection standards and inspection methods
1. LCM product inspection standards: (1) Inspection conditions:
The environmental conditions should be set as (normal temperature) 20~25℃, (under normal temperature) 65%±5%RH (humidity).
②The tool for testing the lighting is a 20W fluorescent lamp, which is 50cm above the work surface (product), and the visual distance is more than 30cm.
(2) Inspection standards:
The inspection is mainly based on batch sampling, and the sampling standard is based on GB2828-93. 2. Some commonly used terms in LCM inspection:
(1) Black dots, black lines
① It displays dark spots and dark linear spots when power is on, and the liquid crystal drive voltage will not change significantly when it changes. ②It shows dark linear spots when power is applied, and the LCD driving voltage changes greatly when it changes.
(2) White spots
Light-colored spots are displayed when power is applied, and there is no major change when the liquid crystal driving voltage changes. ②It displays light-colored spots when power is applied, and large changes occur when the liquid crystal drive voltage changes. (3) White line
①The light-colored linear spots are displayed when power is applied, and the liquid crystal drive voltage does not change greatly when the driving voltage is changed. ②It displays light-colored linear spots when power is applied, and large changes occur when the liquid crystal drive voltage changes. (4) Blue dot
It displays very dark spots when power is applied, and large changes occur when the liquid crystal drive changes. (5) Vertical line (vertical line) defect
When the power is turned on, the longitudinal (usually short axis) line is not bright and lightly displayed. (6) Horizontal line defects
When the power is turned on, the horizontal (usually the long axis) line is not bright and shallow. (7) Cross line defect
When the power is turned on, the intersection of the horizontal and vertical lines does not light up. 3. Inspection scope:
(1) General visual inspection:
All external dimensions of LCM (each device).
②The appearance of the polarizer of LCM LCD and the color uniformity of the screen. The appearance of the polarizer includes: scratches, indentations, bubbles and dirt. ③Flux, solder joints missed soldering, false soldering, insufficient solder, bridging, overflow (too much material).
The appearance of the LCM shell, whether the electroplating paint is even, whether there are scratches, peeling paint. ⑤The uniformity of the leads between the components and whether there are scratches.
⑥Whether the solder mask on the PCB board has fallen off (there are size restrictions), and whether the circuit copper foil is scratched. ⑦The degree of screw fastening and shell foot fastening.
(2) Power-on display check:
① Input voltage, operating frequency, current consumption, LCD contrast and response speed.
②When the power is applied (according to the standard input voltage), the viewing angle range and the display graphics have the above-mentioned defects and graphics misalignment. 4. LCM sampling environment test:
Before the LCM leaves the factory, various environmental tests must be sampled. The items include: ①High temperature power on, high temperature (40°C, 60°C) placement test.
②Power on at low voltage and place test at low temperature (0°C or -20C). ③High temperature and humidity, power on and store.
④ Vibration test.
The above temperature and test are controlled within a certain period.
5.LCM product inspection method:
LCM product inspection is carried out in several situations. According to the quantity of inspection, there are inspection-free, full inspection, and sampling inspection. According to the inspection method, there are self-inspection, mutual inspection and special inspection. According to the inspection methods, there are physical and chemical inspections and sensory inspections.
(1) Sensory inspection:
Sensory inspection of LCM, that is, visual inspection of the LCM shell for scratches and electroplating; whether there are scratches on the surface of the LCD screen and whether there are air bubbles. Whether the components and screws on the PCB are defective (including leads); visual inspection items also include: solder joint flux, whether the solder mask falls off, and the color of the LCD screen.
(2) Physical and chemical inspection:
LCM physical and chemical testing is to use mechanical, electronic or chemical measuring tools as a means to determine the physical and chemical properties of LCM. like:
①Use a vernier caliper and a magnifying glass to detect the length of scratches, the number of bubbles and the size of the polarizer on the LCD screen. These are all limited in number and size in the criteria for determining defects.
②A magnifying glass can also be used to check the solder joints on the PCB of the LCM: whether there is missing solder, false solder, insufficient solder, solder overflow, bridge, etc. Use a microscope to inspect: PCB board graphics (gold-plated layer), whether the circuit is defective, connection, short circuit, open circuit.
④ Use self-made testing tooling to test the performance of LCM electrical appliances according to the test instructions in the special standard document. like:
Display power-on inspection, check the LCD screen, under standard input voltage, whether its viewing angle range, display graphics, color depth meet the test standards, and whether there are black dots, white dots, and white lines in the display area. During the power-on display process, the rated input voltage and current consumption should be tested with a multimeter in accordance with the "Hangzhou Jingxian LCD Specification"; and the operating frequency should be tested with an oscilloscope to check whether it meets the "Hangzhou Jingxian LCD Specification".
