We have mentioned that the principle of FOG hot press is to bond ACF and explode another ACF conductive particle at a certain temperature, pressure and time to solidify ACF adhesive, so as to realize mechanical connection and electrical conduction between liquid crystal glass or PCB and flexible circuit board (FPC).
The simple understanding is to replace the faulty drive soft wire (COF), and the equipment used in this process is called a hot press.
First, the following are the problems we often encounter. In fact, COF (the technology of connecting chips to FPC soft-wires is called COF, and we are also used to using LCD-driven soft-wires as COF) causes the following main faults:
1. Black screen: COF power supply short circuit, DC-DC circuit into a protective state after short circuit, the main voltage has no output, the whole machine stops working, the fault phenomenon is black screen.
2. Line or band: For example, according to the resolution of 1024*768, the driving electrode of source driver is 1024*3 (a pixel unit consists of three RGB pixels)= a total of 3072 driving electrodes. If these electrodes are divided into four regions driven by four COFs, each COF driving pin is 768, and the width of the pin is usually 0.0. Between 05mm and 0.01, it is thinner than hair. If contact is bad or open circuit breaks, the corresponding pins will lose drive, and the screen will appear bright lines, dark lines, large area of bad will form bright or dark bands.
3. Colour band, dark band, interference: What we are talking about here is that a single driving area has an image but the image is not normal, the color bias or brightness is abnormal or the color interference; the source driver driver (also known as data driver, vertical driver, source driver or X-axis driver), because X is good at expressing an English letter, we are used to it. It is called X-axis. In addition to the connection with the panel electrode, the other end is connected with the PCB end, which is also bonded by ACF and formed by hot pressing to form an on-line circuit. The PCB end provides power supply for the source driver, signal transmission and gammma gamma voltage, etc.
Abnormal A. LVDS signal: color interference or discoloration.
B. Gamma voltage anomaly: gray scale and color anomaly.
C. Abnormal power supply: dark band or not working (if power supply or STH output open circuit, look at the location of the driver, will affect the driving work behind, resulting in a large area of failure)
Most of the above are caused by poor PCB end (not excluding the COF drive itself fault), just remove the PCB end and clean it again, paste ACF glue and press it again by hot press.
4. X-axis regional anomalies: X-axis scanning depends on the design of different manufacturers. It can scan from left to right, or from right to left, or from middle to both sides. Either way, it is a relay running mode, just like an athlete passing a baton to another sport after a lap. He was asked to finish the next lap... a lap is equivalent to a COF working area, and the baton is equivalent to STH (STH source source driving start pulse, equivalent to gate driving STV signal). If the last athlete had fallen before he finished the lap, the latter athlete could not wait for the baton to run! That is to say, the rear COF drivers will not work properly, so the whole screen will not work or the front can work, and the back will not work properly (flashing, jumping, black and black).
5. Flower screen: slow response, drawing, flickering, jumping, deformation, disorder, black screen
Gate driverr driver/gate driver/Y-axis driver. At present, the signal power supply driven by gate driverr in LCD panel is driven by PCB through COF and ITO along the edge of the panel, and finally arrives at gate driverr. Any link in the whole circuit may cause errors in scanning timing, slow image response, wire drawing and flickering. Vibration, jump, deformation, disorder, black screen protection stop working, etc.
In addition, we mentioned above what failures can not be repaired, here we also reply, we usually receive calls from some customers, ask if the broken screen can be repaired? Unified reply here, this really can not be repaired!!!
A. Screen leakage can not be repaired, even if repaired by special means can not stand the use, soon the problem is still!
B.Y axis is driven by non-discrete external COF, the corresponding area is usually not repairable, but this is not absolute, individual can be repaired by special means.
C. Short circuit or open circuit inside the screen: Compared with the overall failure rate, it has a relatively low proportion of failure (can be repaired by laser, but the price is very expensive, imported laser must be used, the current domestic technology level is limited, repaired faults quickly, not durable! We only import, we can contact our company. We do not stock this kind of equipment, we need to pay a certain proportion of deposit before production.
Crossroads - X and Y are short-circuited at some intersection point to form two vertical and horizontal lines. A bright spot can be seen at the intersection point.
Big and small headlines - X or Y are short-circuited somewhere with the back panel (VCOM), and the line near the COF driver is relatively not obvious, the closer the short-circuited point line is, the more obvious it is.
Half-line - X or Y open at some point, the second half of the open circuit can not get signal power supply, so the second half does not work, forming a half-line.
More technical problems of LCD maintenance, please call our company, purchase equipment tuition free, we have a large number of LCD screens in maintenance every day, the practice of true knowledge! uuuuuuuuuuu Chuangli Friends look forward to your visit!!