SMT process liquid crystal display module

SMT process is one of the manufacturing processes of LCD drive circuit board (PCB board).

SMT process is to use the mounting equipment to paste the mounting components (chips, resistors, capacitors, etc.) on the corresponding solder pads of PCB printed with solder paste, and realize a traditional installation mode through reflow equipment.Its components are soldered on PCB boards.

The advantages of SMT LCD are high reliability, while the disadvantages are large size and high cost, which limit the miniaturization of LCM.

The process consists of five steps: screen printing, patch, backflow, cleaning and testing.Due to the influence of mounting components (especially chip) size (package size), chip pin clearance number and equipment precision, SMT technology is suitable for processing PCB board with large area, and due to its bare solder joints, it is easy to be damaged, but easy to maintain.

Considering the cost and volume of products, IC manufacturers are reducing the output of QFP (a type of SMT) package. Therefore, the traditional SMT mode will be gradually replaced in future products.


COB (Chip On Board), that is, the Chip is bound On the PCB.

In this process, the bare chip is pasted directly on the designated position of PCB board with adhesive, the chip electrode is connected with the corresponding welding pad of PCB board with aluminum wire by welding machine, and then sealed and solidified with black glue, so as to realize the electrical and mechanical connection between chip and PCB electrode.The process consists of seven steps: adhesive, curing, pressure welding, testing, sealing, curing and testing.

COB process adopts small bare chip with high equipment precision, which is used to process PCB boards with more lines, thinner gaps and smaller area requirements. After welding pressure of the chip, it USES black glue to solidify and seal to protect the solder joint and welding line from external damage, with high reliability, but after damage, it cannot be repaired and can only be scrapped.


TAB liquid crystal module process


TAB (Tape Aotomated Bonding), which refers to the connection mode of anisotropic conductive glue, is a processing mode of connecting the screen with the driving circuit board through the hot pressing of ACF (Tape Carrier Package) IC packaged with TCP(Tape Carrier Package) at a certain temperature, pressure and time.It mainly includes four steps: ACF preloading, alignment inspection, main pressure and detection.


COG (Chip On Glass) is a Chip that is bonded directly to the Glass.

This process is designed in the LCD outer lead concentrate is small area will be dedicated LCD LSI - stick in the meantime, special chip IC with pressure wire welded together by the requirement, each endpoint sealing glue can't on casting a drop, and the input end of the IC is also designed in the LCD glass, lead and bonding to the same chip input endpoint, at this point, this chip has constituted a complete LCD LCD module.Usually connect the interface with FPC or conductive paper to facilitate the use of customers.The process mainly includes seven steps: screen setting, ACF setting, chip setting, alignment checking, chip pressure welding, adhesive sealing and testing.

This processing method can greatly reduce the volume of the whole TFT LCD Module, and is easy to produce in large quantities. It is suitable for LCD used in consumer electronic products, such as mobile phone, PDA, MP3 and other portable electronic products.With the promotion of IC manufacturer, COG will be the main connection mode between IC and LCD in the future.

COF(Chip On Film), that is, the Chip is directly installed On the flexible PCB, and then the flexible Film transmission belt is connected to the external lead of the liquid crystal display device with different guide electroglue.This connection mode has high integration, and the peripheral components can be installed on the flexible PCB together with IC.


Common lighting in LCM

Liquid crystal display device is a passive display device, it does not emit light itself, is dependent on the modulation of external light to achieve the display.External light liquid crystal display device display prerequisite.Therefore, in the assembly and use of liquid crystal display, lighting can be cleverly solved to ensure and improve the quality of liquid crystal display. Generally, lighting mode of liquid crystal display can be divided into natural light lighting mode and external light source setting mode.On the setting of external light source, it is divided into three categories: back light source, front light source and projection light source.

一. functions of backlight lighting technology:

1. The liquid crystal display device can be used in the environment with or without external light;

2. Improve the background brightness and display effect.


二. Common backlight:

LED backlighting features:

* easy brightness adjustment;

* is a common way of backlighting;

* there are four different layouts (shown below) to suit the lighting needs of different modules;

* other forms of layout can be designed according to customers.


EL- field luminescence characteristics:

* the backlight plate is very thin, generally less than 1mm, so it has little impact on the thickness of the whole LCM;

* under normal driving conditions, its initial brightness is high, its half-life is 5,000-8,000 hours;

* the standard color is blue-green, if you need other colors of EL backlight, please consult our company;

* EL backlight requires special inverter power supply;


CCFL- characteristics of cold cathode fluorescent lamp:

* high brightness, high power consumption;

* backlight required for large area display;

* color reduction is good;

* brightness can be adjusted;

* average brightness half-life is 20,000 hours;

* need corresponding inverter.


Common assembly mode of LCM:

COB_HSC (conductive paper connection without backlight)

COB_BZ_BL (iron frame with backlight)

COB_BZ (iron frame assembly without backlight)

COG_PIN (metal pin connection)

COG_HSC (conductive paper connection)

COG_FPC (FPC connection)

COG (without any connector)

TAB_HSC (conductive paper)

The TAB

COF package


SMT Process Liquid Crystal Display Module