Analysis report on the causes of bright spots and poor bright lines in TFT lcd
As the core display component of modern electronic devices, the yield of LCD screens directly affects product performance and user experience Among them, Bright Spot and Bright Line LCD screens are two common types of defects This article will analyze i
Analysis of the reasons for poor bright spots and lines on LCD screens
As the core display component of modern electronic devices, the yield of LCD screens directly affects product performance and user experience. Among them, Bright Spot and Bright Line LCD screens are two common types of defects. This article will analyze its causes from the aspects of technology, materials, design, etc.
1.Analysis of the Causes of Bright Spots
Highlight refers to the phenomenon where a local area of the LCD screen continues to emit light even when displaying dark images, usually caused by the following reasons:
Foreign matter contamination in the liquid crystal layer
If the cleanliness is insufficient during the production process, dust or particles may adhere to the liquid crystal layer or TFT (thin film transistor) substrate, causing local electric field abnormalities and forming constantly bright pixels.
Impact stages: LCD infusion, substrate bonding process.
2. TFT array defects
The switching transistor of a certain pixel in the TFT array (such as TFT short circuit or open circuit) cannot control the deflection of liquid crystal molecules normally, resulting in the pixel continuing to conduct.
Common reasons: photolithography process deviations, etching residues, or abnormal electrode materials.
3. Poor packaging leads to light leakage
The backlight module is not tightly attached to the LCD panel, or the border sealant is unevenly applied, resulting in local light leakage and the formation of bright spots.
Typical case: uneven packaging pressure and insufficient glue curing.
4. Electrostatic breakdown (ESD)
During the production or handling process, static electricity is not effectively released, causing breakdown of internal circuits of TFT or driver IC, resulting in permanent damage to pixel points.
2、 Analysis of the Causes of Bright Line
Bright lines refer to one or more abnormal horizontal/vertical bright lines appearing on the screen, usually caused by circuit or structural damage:
1. Driver circuit malfunction
Row/column driver IC damage: Poor soldering of driver IC pins, internal circuit breakage, resulting in the inability to transmit the entire row or column signal normally.
Short circuit of signal line: The adjacent lines of the driving circuit (such as COF, FPC) are short circuited due to external compression or corrosion, triggering abnormal signal of the entire column.
2. Glass substrate circuit breakage
The ITO (indium tin oxide) wires on the substrate break due to mechanical stress (such as cutting, assembly pressure) or mismatched thermal expansion coefficients, causing longitudinal/transverse bright lines.
3. Polarizer or backlight structure damage
Scratches on polarizing film or local deformation of backlight guide plate may cause abnormal refraction of light, resulting in a visual effect similar to bright lines (to be distinguished from circuit issues).
4. External impact or aging
Falling or squeezing during use can cause internal circuit breakage, or long-term high temperature and high humidity environments can accelerate metal circuit corrosion, ultimately leading to bright wires.
3、 Common process risk points
1. Insufficient production cleanliness: Foreign object contamination is the main cause of highlights.
2. Equipment accuracy issues: Precision deviations in lithography and bonding machines can easily lead to defects in the circuit or TFT.
3. Material compatibility: The difference in thermal expansion coefficient between ITO and substrate may cause microcracks.
4. Failure of electrostatic protection: Insufficient ESD protection measures directly threaten circuit safety.
4、 Suggestions for improvement direction
1. Process optimization: Strengthen clean room control, optimize LCD infusion and packaging process parameters.
2. Detection upgrade: Introduce AOI (Automatic Optical Inspection) equipment to screen for early defects.
3. Material verification: Conduct reliability testing on key materials such as ITO and sealant.
4. Design redundancy: Increase the redundancy design of the drive circuit to reduce the risk of single point failure.
5、 Conclusion
The core causes of bright spots and poor bright lines in industrial LCD screens can be attributed to three categories: material defects, process fluctuations, and structural damage. By systematically analyzing potential risk points in the production process and improving the process and testing procedures accordingly, the yield and reliability of industrial LCD screens can be significantly improved.
industrial LCD screens ：https://www.idtdisplay.com/products/AUO_LCD_Displays/
