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LCD Module Assembly Types

Blaze Display Technology Co., Ltd. | Updated: Oct 21, 2015

  【R&D Department of Blaze Display】Assembly types refers to how LCD controller/driver IC chips are mounted. The most common types are SMT, COB, TAB and COG. There are also other variants based on the these types.

SMT (Surface Mount Technology)

    Using quad flat packages on printed circuit boards is the most popular in LCD industry, and is available for mass production of most LCD modules. It remains the most reliable and robust method for LCD assembly.    Plastic Quad Flat Package (QFP) represents itself as a flat rectangular integrated circuit package with its leads projecting from all four sides of the package.

COB (Chip On Board)

    COB is a popular IC mounting method that provides wire bonding as the direct attachment of bare die to laminated printed circuit boards. The LCD driveris formatted into an area on the PCB. Electrical connections are made by micro diameter gold wires. The entire area is then covered with epoxy. Most of our LCD modules use COBmounting method.

    Advantages

  • Very compact

  • Space savings over SMT assembly.

  • Cost savvy compared with SMT, since there is no plastic package

TAB (Tape Automated Bonding)

 

    LCD controller and/or driver electronics are encapsulated in a thin, hard bubble package, of which the drive leads extend from the bubble package on a thin plastic substrate. The adhesive along the edges is used to attach the TAB to the LCD glass and/or PCB.
 
 TAB mounting method uses the same type of integrated circuits as COG technology - Gold Bumped Flip Chips. After this type of IC chip is produced, a gold bump is placed on the IC chip and then sealed onto the polymide board. (This procedure is called ILB or Inner Lead Bonding) and is how the TCP IC is produced.
 
  Advantages

  • Offers compactness (IC and its interfacing circuitry can be bent behind the LCD glass panel).

  • Some times more cost-effective than COG, if a designer has to integrate a keypad or indicator around the display.

  • The active area is centered (differently from COG).

  • Can provide interfacing at very fine pitches.

    Disadvantages

  • The bonding area is weak. Less reliable than COG.

  • More expensive than COG. Even though TAB LCD modules use the same type of IC as COG, tape automated bonding requires a package.

COG (Chip On Glass)

    COG is one of the high-tech mounting methods that uses gold bump or flip chip ICs, and implemented in most compact applications. COG integrated circuits were first introduced by Epson. In flip-chip mounting, the IC chip is not packaged but is mounted directly onto the PCB as a bare chip. Because there is no package, the mounted footprint of the IC can be minimized, along with the required size of the PCB. This technology reduces the mounting area and is better suited to handling high-speed or high-frequency signals.

    Advantages

  • Very space economical. COG LCD modules can be as thin as 2 mm.

  • Cost effective over COB, especially in graphic LCD modules, because much less IC´s are required.

  • More reliable than TAB, because of the weakness in the bond area of TAB.

    Disadvantages

  • COG can only be used at a certain resolution level where the lines are not too fine. At very fine pitches COG becomes difficult to test, and TAB is the preferred approach.

  • It may be more cost-effective to use TAB or COB, if a designer has to integrate a keypad or indicator around the display. 
    The active area is not centered within the outline but offset, because of the area where the circuits are.

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