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  • Electronic evaluation of new projects

    A. Assessment of interface definitions

    The individual PIN definitions coming out of the display must be consistent with the PIN definitions connected to the customer’s motherboard.
    The following is a 37pin interface definition
    Pin No. Symbol Description Note
    1 GND Ground —
    2 VCI(2.8V) Power Supply Input
    3 IOVCC(1.8V/2.8V) Power Supply Input
    4 /CS Chip select signal pin Input
    5 RS Register select signal pin Input
    6 /WR Write signal pin Input
    7 /RD Read signal pin Input
    8 /RESET Reset signal Input
    9 DB0 Data bus pin Input / Output
    10 DB1 Data bus pin Input / Output
    11 DB2 Data bus pin Input / Output
    12 DB3 Data bus pin Input / Output
    13 DB4 Data bus pin Input / Output
    14 DB5 Data bus pin Input / Output
    15 DB6 Data bus pin Input / Output
    16 DB7 Data bus pin Input / Output
    17 DB8 Data bus pin Input / Output
    18 DB9 Data bus pin Input / Output
    19 DB10 Data bus pin Input / Output
    20 DB11 Data bus pin Input / Output
    21 DB12 Data bus pin Input / Output
    22 DB13 Data bus pin Input / Output
    23 DB14 Data bus pin Input / Output
    24 DB15 Data bus pin Input / Output
    25 (LCM_ID) LCM Identify select pin Input
    26 Y-YD Touch panel down pin Input
    27 X-XR Touch panel right pin Input
    28 Y+YU Touch panel up pin Input
    29 X+XL Touch panel left pin Input
    30 LED-A LED anode for all LED Input
    31 LED-1 LED cathode for LED1 Input
    32 LED-2 LED cathode for LED2 Input
    33 LED-3 LED cathode for LED3 Input
    34 LED-4 LED cathode for LED4 Input
    35 GND Ground -.
    36 GND Ground -.
    37 IM0 Select the MPU system interface
    mode Input

    B. LCD Interface Method

    There are two common interface methods: CPU (also called MCU 8080 system) and RGB interface.
    CPU interface: is the most common mode for small and medium-size, generally 8080 system, parallel data transfer.
    It can be 8-bit, 9-bit, 16-bit, 18-bit, etc., easy and convenient to control, but requires GRAM.
    RGB interface: the large screen adopts more modes, the data transmission is also divided into 6, 16, 18 bit, etc., relatively speaking.
    Serial transmission of data is slower, but has the advantage of fewer interface signal lines and takes up fewer resources.

    C. Drive current-voltage confirmation

    Determine the drive voltage according to the LCD Panel and the SPEC of the IC, e.g. VDD, VCI, according to the backlight LED
    The control IC and the corresponding current and voltage values of the LEDs are determined in series or in parallel.

    D. FPA, PCB wiring space assessment

    Depending on the size of the product, determine whether the FPA, PCB meets the design requirements.
    Adequacy of the approximate component area.
    FPA minimum line width, and whether the line spacing meets the requirements.
    The PCB component space is sufficient.

    E. ESD assessment

    In addition to adding ESD-resistant circuits to the design, the product itself needs to be protected against static electricity. In particular. Protective measures at IC locations.

    Structural assessment of new projects

    In the pre-assessment design of a new project, we review the assessed project based on the inquiry provided by the client.
    The aim is to ensure the rationality of the design, the versatility of the main materials, the operability of the production process, and the reliability of the quality requirements. The assessment is generally divided into two parts, structural and electronic, to give the client some reasonable suggestions for improvement.
    Based on the final assessment, it is determined whether this new project can be established or not.

    Structural assessment of a new project


    A. Panel suitability assessment

    Select all panels that meet the required size (e.g. 2.8″ WQVGA).
    Select the appropriate panel based on the customer’s display requirements, type and AA size.

    B. Evaluate external dimensions

    According to the newly selected panel, confirm that the outline dimensions of the product meet the customer’s outline dimension requirements.
    The length, width, and thickness must not exceed the customer’s drawing requirements.
    Display area AA to the edge of the product must be dimensioned to meet customer drawing requirements, i.e., AA location is consistent with customer drawing requirements.

    C. Identification of Key Resources

    Based on the selected panel, select compatible driver ICs and ensure the availability of panels and ICs for mass production.
    Design of screen backlighting BLU, touch screen TP, circuit board FPA, PCB, etc. according to product form factor. Primary Resource.
    Design drawings must be changed if materials other than panels and ICs are not available.

    D. Display Requirements

    Determine the surface brightness, average degree, and color of the entire display module according to the customer’s requirements for display effects.
    Display color: 65K, 262K, 1600W.
    Viewing angle: normal viewing angle, super wide viewing angle, full viewing angle.

    E. Connectivity evaluation

    The signal interface method confirms compliance with the design processing requirements.
    There are generally two connection methods: soldering (including hot rod) and CON connectors (ZIF, B2B).
    FPAs are appropriately located to facilitate the evaluation of processing, etc.

    F. Evaluate material supplier’s processing capabilities

    The ability of the existing suppliers of each material to meet design drawing requirements.
    For example, FPA minimum line width, line spacing, surface treatment capability, SMT accuracy.
    For example, the minimum processing capability of materials such as thin-walled backlight frames, high-brightness LEDs, and the latest high-brightness enhancement films.
    Certified use, light guide plate V-cut technology, Frame and BZ integrated injection molding technology, etc.
    And mass production is possible.
    For example, TP minimum linearity, surface strength, number of clicks, and number of scribes to meet the requirements.

    G. Productivity assessment of product assembly process

    Whether the production process level of the factory can meet the requirements of the drawings and meet the mass production during processing.
    For example, whether the accuracy of the bonding machine can guarantee the bonding effect of the IC.
    For example, the accuracy of the polarizer’s attached bias.
    For example, whether the degree of control of the solder is high.

    H. Comprehensive Evaluation and Recommendations

    Based on our design and production experience, we can carry out a thorough evaluation of the product’s structure, giving the customer a
    The company has suggested a number of improvements to optimize the design and production of its products.
    For example, increasing the BZ to improve the strength of the product.
    For example, to design positioning posts to position the product during assembly.
    For example, designing the first pin around the FPA to protect the Dummy pin.

    LCM common defects and quality standards

    A. Description of main parts
    Item Criterion Remark
    1. FPCA The criterion for chip component solder point: IPC-A-610C CLASS 2 on general occasion。 Vision inspection / Microscope
    2. Backlight 2.1 Defect of no light is unaccepted。
    2.2 The brightness (test with BM-7 equipment ) and power consumption must meet SPEC
    3. Bezel Any damage, distortion and other solder sparks on the bezel surface is unaccepted。
    4. FPC 4.1 Criterion for bending and crease. In picture 22, “a” is the angle composed of the extended lines of the crease. This angle must be more than 90 degrees.
    4.2 The area of the crack, damage, foreign material and the air bubble is not allowed to be more than 1/5 of that of the enhancing film.
    4.3 Golden finger should not be scraped obviously; Any stain and foreign on the finger is unaccepted.
    Vision inspection / Microscope
    5. LCD screen 5.1 A protective plaster should be stuck to the screen based on the SPEC.
    5.2 Any dust, fingermark, stain, or other foreign material on the screen surface that can not be got rid of with a soft cloth or air gun is unaccepted.
    5.3 The Defect of no display is unaccepted.
    5.4 Defect of lack of line or cross-talk is unaccepted.
    5.5 Abnormal chroma, brightness, and contrast (compared with golden Sample and SPEC parameter) are unaccepted
    5.6 Uneven backlight (compared with golden Sample) or dark area is unaccepted.
    5.7 Response time of menu change must meet SPEC.
    5.8The LCD screen shift amount should not be more than 0.2mm based on the SPEC.
    5.9The criterion should be loosened in judging the defect in the area out of the screen.
    Vision inspection
    B. Visual failure
    Inspection item Criterion Remark
    Liner matter
    Width (mm) Length (mm) QTY
    W≤0.1 / Ignore
    0.1/W≤0.2 L≤5 3
    W>0.2 / 0
    Width (mm) Length (mm) QTY
    W≤0.03 / Ignore
    0.03m/W≤0.05 L≤5 2
    0.05m/W≤0.1 L≤2 2
    W>0.1mm or L>2mm 0
    As liner
    Fisheye on film/Dent on film and Air bubble
    Size (mm) QTY
    D≤0.2 Ignore
    0.2<D≤0.4 5
    0.4<D≤0.5 2
    D>0.5 0
    Size (mm) QTY
    D≤0.15 Ignore
    0.15<D≤0.2 3
    0.2<D≤0.3 1
    D>0.3 0
    As fish eye
    Chip and crack Corner Chip X≤3mm Y≤3mm Z≤T
    General Chip X≤3mm Y≤3mm Z≤T
    X≤5mm Y≤1mm Z≤T
    Crack 0
    C. TFT bad dot matrix
    Defect Mode Acceptable Judgment Criteria
    Dot Type Quantity (ea)
    Bright Dot Random (Red, Blue, Green) 1
    2 or more adjacent dot defects 0
    Dark Dot Dark dot 3
    2 adjacent dots 1
    3 or more adjacent dots 0
    D.?Reliability assurance
    No. Items Specification
    1 High Temp storage 70°C, 160hr
    2 Low Temp storage -20°C, 160hr
    3 High Temp operation 60°C, 160hr
    4 Low Temp operation -20°C, 160hr
    5 Humidity storage 60°C, 90%, 160hr
    6 Humidity operation 60°C, 90%, 160hr
    7 Thermal Shock -10°C (30min) ~60°C (30min) 20 cycle


    LCM Production Checksheet

    No ?Inspection ?results
    1 Model using ACF
    2 First, check sample COG whether there are enough 5 effective conductive particles per BUMP
    3 First inspection sample COG BUMP and ITO PAD alignment
    4 First inspection sample IC back microscopy, no scratches on the back of the IC
    5 COG Actual state temperature and time in accordance with ACF specifications
    6 IC BUMP does not press on the overline between ITO PAD
    1 Model using ACF
    2 Heat bonding temperature/time in accordance with ACF specifications
    3 FPA Pull >600gram F/cm
    4 FPA gold finger and TFT ITO recombined more than 2/3 in the first inspection sample
    5 5 active conductive particles on the ITO corresponding to each FPA gold finger
    6 DP190 Adhesive edge width <1.5 mm, height not to exceed the glass surface, and can completely cover the FPC
    Goldfinger leaking after the thermal break
    Welding backlight/TP
    1 Backlighting, TP welding positioning and joint height control
    2 FPA pads are guaranteed to leak 0.5 mm during soldering to ensure adequate soldering
    3 Insulation paper just the right size to cover the solder joint or PAD bit
    4 No components must be attached to the back of the pads of the BL/TP on the TFT FPA in order to prevent the soldering of the elements pieces of welding joints that are deficient assemble.
    1 TP should be assembled with good adhesion and not produce TP warping, displacement, etc. (If the TP backing is a water glue, fix it with 406 drops of glue after assembly)
    2 Whether TP assembly requires special fixtures to meet the positioning accuracy requirements specified in the drawing
    3 The inaccessibility of the edge of the polarizer to the VA after assembly
    4 No uneven bright spots/lines in the background light after assembly
    5 The gap between the glass surface of TP and the polarized sheet of TFT after assembly is >0.2mm; Press strongly with a pen on the adjacent area of the TP surface without any watermarking; after removal, all areas will not
    Watermark must remain.
    6 Backlighting is appropriate for the TFT and does not produce visible edges or shaded rows phenomenon
    7 The block (BZ) is properly matched to the TP and does not have the potential to cause the TP to crack.
    8 Components on FPA (after bending) must not interfere with the backlight
    9 FPA bending and dismantling of the positioning method to ensure that the finished drawing of the positioning size and error of the seek (Consider using an assembly positioning jig if there is no positioning mark on the product)
    10 Iron frame with backlight will not come loose after assembly
    11 After assembly, there are no gaps between TP, BL, TFT for dust intake.
    12 Backlit LBL backed with conductive cloth, double-sided tape, labels, positioning tape, etc. under pressure. No shading of the display and no pulling up of the backlight adhesive paper.
    13 IC (with RTV adhesive) must not be higher than the backlit bezel after assembly
    14 After assembly, the height of the polarized sheet on the TFT should not be higher than the backlight frame
    15 FPA Bending shall not be shorted directly to the iron frame with exposed copper parts.
    16 Shell openings or sides must not have a blade stabbing into the FPA face to prevent a short circuit.
    17 TP Pull Tape Tear Film Very Tolerant to Remove Film
    18 Full product size (key size with *) checked (5 pieces)
    19 No light leakage within the inner TP screen edge after assembly
    20 For products with the iron casing, the BL+TFT+ iron casing needs to be bent in 3 pieces, such as IC. If cracking occurs, a sponge adhesive of the appropriate thickness will be applied to the IC or outside (against FPA)
    1 Drop test results PASS


    LCM production process flow

    LCM production process flow

    The LCD module production process consists of the following steps.

    A. Cleaning the Panel

    Attach by hand

    B. Attachment of polarizers


    Semi-automatic machine attachment

    C. COG Bonding


    ACF AttachmentACF Attachment img


    D. FPA HS thermal pressure


    FPA HSFPA HS thermal pressure


    E. Insulating glue coating


    Insulating glue coating

    F. Assembly of BLU


    Assembly BLU

    G. Assembly of BZ


    Assembly BZ

    H. Assembly of TP


    Assembly TP

    I. Assembly of PCBs


    Assembly PCB

    J. Assembly of other auxiliary materials


    Assembly accessories

    K. Electrical characteristics testing


    Electrical characteristics testing

    L. Appearance and OQA inspection

    M. Packing for shipment

    Introduction to LCM structure

    Introduction to LCM structure


    1. TP

    Touch Panel touch screens, commonly 4-wire resistive touch screens. The user can use the stylus directly or fingers to operate.

    2. TFT Panel

    The panel that provides the display for the entire display module and is the most important component of the display module, the panel performance determines its display effect, high resolution, high contrast, high color reproduction, correspondingly fast time, transparent
    The characteristics of the over type, semi-permeable type, etc.

    Display size development

    The generation change of the LCD Panel plant is divided by the size of its glass substrate. 1st Generation TFT-LCD
    The glass substrate size of the production line is 300mm×400mm-320mm×400mm, and then the glass substrate size of each generation of the factory has increased compared to the previous generation, and in the third generation, it is 5XXmm×6XXmm, 6XXmm×7
    The XXmm is a 3.5-generation line, the 4-generation line is 6XXmm×8XXmm-7XXmm×9XXmm (also classified as a 4.5-generation line), and the 5-generation line is available in 1000mm×1200mm and 1100mm×1250mm sizes.


    Take Corning, the world’s largest glass substrate manufacturer, as an example, the dimensions of its glass substrates for each generation are as follows:
    G8: 2160mm×2460mm
    G7: 1870mm x 2200mm
    G6: 1500mm x 1800mm
    G5: 1100mm x 1250mm
    G4: 680mm x 880mm (Image)
    G3: 550mm x 650mm
    G2: 370mm x 470mm
    G1: 300mm×400mm



    Major suppliers of display screens

    At present, LCD panel suppliers are mainly from Japan, Korea, and Taiwan, with only Beijing Jingdong in mainland China
    Fang BOE, Shanghai Broadcasting Corporation, Shenzhen Tianma has a production line.

    Japan: TMD, SHARP, NEC, Sanyo, Kyocera, Toshiba, etc.
    Korea: Samsung, LPL.
    Introduction and Design of Small and Medium Size LCD Module Page 19
    Taiwan: AUO, CMO, TPO, CPT, Hanstar, PVI, etc.
    Hong Kong: Varitronix Varitronix (Mono, STN), Truly.
    Mainland China: BOE, SVA.

    3. BZ

    BZ, commonly known as Bezel, is a stainless steel SUS304 series material. Thicknesses commonly 0.1, 0.15, 0.2.
    0.3, 0.5mm, or other thickness.
    The main role of BZ is to strengthen the structure of the LCD module, protect the corresponding parts, reduce the impact of external forces, etc.
    Usually, where construction, thickness and price allow, the upper and lower iron frames can be designed so that the entire product can be
    Within the protection of an iron frame.

    4. BLU

    The Back Light Unit is a backlight that serves primarily to illuminate a non-self-illuminated Panel. small and medium-sized ruler
    The inch basically uses various colors of the LED light source, now, in the large size also began to use LED backlight, such as LED pen
    Notebooks, LED LCD TVs.

    5. FPA

    Flexible Printed Board Assembly. is usually divided into three types: hardboard, soft board, and soft-rigid combination board.
    The main function of the FPA flexible circuit board is to connect the display to the motherboard and to install the peripheral power of each IC.
    The circuit components, as well as other components designed. It can be bent and flexed according to design requirements, thin thickness.
    Lightweight and easy processing.

    6. PCB

    Printed Circuit Board rigid board. The main function is to connect the display to the motherboard and install other components or connected to other parts. Usually, you can do 4 layers, 8 layers, 10 layers, 20 layers of lines, etc.

    7. Duct tape

    There are generally three kinds of tapes: adhesive tape with one or two sides, insulating tape, and conductive tape. Design
    The required material does not need to be of the appropriate performance and thickness.
    The tape in the picture above is the double-sided tape used to connect the backlight to the PCB board.

    8. Accessories

    Conductive cloth, foam, tape, or some non-essential materials specified by the customer are collectively referred to as auxiliary materials. Depending on the design
    The design or assembly is done on request or at the request of the customer.

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