The structural design of the product causes bright spots on the LCD screen
Date:2025-10-14
The structural design of the product causes bright spots on the LCD screen
Issues in product structural design or assembly are a very important and common cause of bright spots on LCD screens.
Below, I will provide a detailed explanation of the underlying principles, common structural issues, and preventive measures.
Basic Principle: Why do structural issues lead to bright spots?
The liquid crystal display itself is a highly precise layered structure, primarily composed of a backlight module, liquid crystal layer, color filter, and polarizing film. Among these, the backlight module is responsible for providing uniform light.
The key to uniformity: A normal liquid crystal display requires the light emitted by the backlight module to pass uniformly across the entire screen. Any localized physical pressure on the internal structure of the screen (especially the light guide plate and diffusion film in the backlight module) will disrupt this uniformity.
Pressure causes deformation: When structural components outside the screen (such as the casing, frame, support, or screw posts) exert uneven pressure on the screen itself, this force is transmitted to the internal light guide plate and optical films.
Deformation causes optical abnormalities:
After the light guide plate is compressed, its precise dot structure will change, causing abnormal scattering of light in that area, resulting in a brighter point or area than other areas, which is what we see as a "bright spot".
Optical film sheets (such as diffusion films and brightening films) that are compressed can produce wrinkles or permanent deformation, which can also change the direction of the optical path, forming bright spots or optical phenomena similar to water streaks.
Simply put, bright spots can be seen as local optical scars caused by being "bumped" or "pushed" inside the screen.
Common structural issues that cause bright spots in products
The shell or frame design is too tight/the tolerance control is improper
Problem description: The clearance between the front and back cases of mobile phones, laptops, or monitors, or between the metal frame and the screen, is too small. After assembling and locking the screws, excessive clamping force will directly squeeze the edges of the screen or the panel body.
Consequence: Bright spots are prone to appear at the edges of the screen or corresponding screw holes.
Excessive torque of screws or unreasonable design of screw posts
Problem description: The screws that fix the screen module or housing are tightened too tightly (excessive torque). Alternatively, the positioning of the screw post may be inaccurate or the height may be inconsistent, resulting in one screw post abnormally pressing against the back of the screen.
Consequence: A very typical circular or cross shaped bright spot is generated in the screen area corresponding to the screw position.
Design defects in internal support structure
Problem description: In order to pursue slimness, there is insufficient "buffer space" left for the screen inside the device. If the height calculation of internal components (such as batteries, components on the motherboard), reinforcement ribs, or support frames is incorrect, they may hit the back of the screen when the device is subjected to normal external forces (such as being squeezed in a bag or holding the phone with one hand).
Consequence: Irregular bright spots appear in the middle area of the screen, which is particularly common in lightweight devices.
Improper operation during assembly process
Problem description: Although strictly speaking, this is not a "design" issue, it is related to structural assembly. When workers are assembling, if the screen is not placed flat in the middle frame, or if there are foreign objects (such as small screws, debris) left between the screen and the shell, it will create huge pressure points in the local area.
Consequence: irregular shaped and randomly located bright spots are generated.
The impact of thermal expansion and contraction
Problem description: The thermal expansion coefficients of different materials (such as metal, plastic, glass) in the equipment are different. If this is not taken into account in the structural design, the degree of expansion and contraction of different components may vary during drastic temperature changes, which may cause local pressure on the originally normal structure at specific temperatures.
Consequence: Some bright spots may appear or worsen in high or low temperature environments, and then decrease or disappear after returning to room temperature.
How to prevent and improve?
For product design and manufacturers, avoiding such problems requires multiple efforts:
Accurate structural design and tolerance analysis: During the design phase, precise gap and tolerance analysis is performed using CAD software to ensure sufficient buffer space between the screen and surrounding structures.
Reasonable screw column and support design: Avoid aligning the support point directly with the sensitive area of the screen (such as the center of the LCD box), and adopt a limit structure to disperse pressure.
Strict assembly process control: Standard screw torque is specified and implemented to ensure a standardized assembly process and prevent foreign objects from falling in.
Adequate reliability testing: Prior to mass production, mechanical stress testing (such as extrusion, torsion, drop testing), high and low temperature cycling testing, and early detection of potential structural defects are conducted.
Use cushioning materials: Use high-quality foam, silicone pads, and other cushioning materials between the screen and the casing/internal structure to absorb and disperse pressure.
summary
Although the bright spots on the LCD screen may seem like a quality issue with the screen itself, a large part of the root cause lies in the product's structural design, manufacturing tolerance control, and assembly process. When a device experiences a common issue of bright spots, the first thing to be suspected is whether its structural design has defects.
For ordinary users, if your device has bright spots and is within the warranty period, you should contact after-sales service as soon as possible for inspection and repair, as this is usually considered a product quality issue.
AUO LCD Display：https://www.auo-lcd.com/products/auo-lcd-screen/
