A touch display driver integrated circuit board and its fabrication method

Abstract

This application relates to an integrated touch display driver circuit board and its fabrication method, belonging to the field of circuit board fabrication technology. It includes a rigid board area and a flexible board area. The rigid board area has an inner signal area and a touch display area arranged sequentially from bottom to top. The touch display area has an isolation ground layer, a touch signal layer, a display signal layer, and a main ground layer arranged sequentially from bottom to top. A ground shielding layer is disposed between the touch signal layer and the display signal layer. The touch display area includes a flexible substrate. The display signal layer is disposed on the upper surface of the flexible substrate, and the touch signal layer is disposed on the lower surface of the flexible substrate. The ground shielding layer is disposed within the flexible substrate. The flexible board area has a second flexible conductive layer and a first flexible conductive layer arranged sequentially from bottom to top. The second flexible conductive layer is connected to the touch signal layer, and the first flexible conductive layer is connected to the display signal layer. A flexible shielding layer is disposed between the second and first flexible conductive layers, and the flexible shielding layer is electrically connected to the ground shielding layer.

Description

Technical Field

[0001] This application relates to the field of circuit board manufacturing technology, and in particular to an integrated touch display driver circuit board and its manufacturing method. Background Technology

[0002] In existing flexible display modules, touch functionality and display driving functionality are typically implemented on two separate PCBs (printed circuit boards) or FPCs (flexible printed circuit boards), and are electrically connected via connectors (such as board-to-board connectors) or soldering. This separate design has the following significant drawbacks: although there are technologies that integrate touch and display driving onto a single chip (TDDI), the wiring of its peripheral circuits (including power supply, memory, passive components, etc.) and the lines connecting the display screen and touch sensors still require complex layout on the PCB.

[0003] Existing technology relates to a method for manufacturing a rigid-flex circuit board, comprising the following steps: providing an inner circuit board, the inner circuit board including a circuit area and a non-circuit area, the non-circuit area forming two sets of target points, wherein the line connecting one set of target points intersects the line connecting the other set of target points perpendicularly to form a cross-shaped target point; forming an outer substrate on at least one side of the inner circuit board, at least one of the inner circuit board and the outer substrate being a flexible board, thereby obtaining a rigid-flex board; drilling holes in the rigid-flex board using the cross-shaped target point as a reference point; and fabricating the outer substrate to form an outer circuit board, thereby obtaining the rigid-flex circuit board.

[0004] The aforementioned and existing rigid-flex boards typically employ a design where the transition area between the rigid and flexible layers terminates with each layer material at the same vertical cross-section. During bending, stress is highly concentrated at this cross-section. Simultaneously, the touch signal layer and the display signal layer are usually located on different substrates, with a large physical distance between the two signal layers. This results in a large bending angle between the two signal layers during bending, making them prone to microcracks due to metal fatigue under repeated bending conditions, which affects the electrical continuity and transmission reliability of the circuit board. Summary of the Invention

[0005] This application provides an integrated touch display driver circuit board and its manufacturing method, which can solve the problem of excessive bending angle of the internal signal layer of existing circuit boards and excessive stress concentration.

[0006] The technical solution of this application is as follows: A touch display driver integrated circuit board, comprising: The rigid board area includes an inner signal area and a touch display area arranged sequentially from bottom to top. The touch display area includes an isolation ground layer, a touch signal layer, a display signal layer, and a main ground layer arranged sequentially from bottom to top. A ground shielding layer is provided between the touch signal layer and the display signal layer. The touch display area also includes a flexible substrate. The display signal layer is disposed on the upper surface of the flexible substrate, the touch signal layer is disposed on the lower surface of the flexible substrate, and the ground shielding layer is disposed in the flexible substrate. A flexible circuit board area is disposed on one side of the rigid circuit board area. The flexible circuit board area is provided with a second flexible conductive layer and a first flexible conductive layer from bottom to top. The second flexible conductive layer is connected to the touch signal layer, and the first flexible conductive layer is connected to the display signal layer. A flexible shielding layer is disposed between the second flexible conductive layer and the first flexible conductive layer. The flexible shielding layer is electrically connected to the ground shielding layer. The rigid board area and the flexible board area are interconnected and form a transition area at the connection point. In the transition area, the projections of the connection edge D1 between the second flexible conductive layer and the touch signal layer, the connection edge D2 between the flexible shielding layer and the ground shielding layer, and the connection edge D3 between the first flexible conductive layer and the display signal layer on the horizontal plane are arranged sequentially at intervals along the direction from the flexible board area to the rigid board area, forming a stepped distribution.

[0007] By adopting the above scheme, the termination positions of each layer of material in the transition zone, that is, the junction of the rigid plate area and the flexible plate area, are horizontally staggered, so that the cross-sectional stiffness of the transition zone changes in a gradient. Compared with the traditional vertically aligned cross-section design, this scheme disperses the stress concentration points generated during bending to three different cross-sectional positions, D1, D2, and D3, reducing the risk of sudden changes in cross-sectional stiffness and forming a stepped stress release mechanism. This reduces the accumulation of metal fatigue in the flexible conductive layer under repeated bending conditions, and improves the fracture resistance of the connecting transition zone and the mechanical reliability of the overall structure. Meanwhile, by placing the touch signal layer and the display signal layer on opposite sides of the same flexible substrate and separating them with a grounding shield, the excessive bending angle caused by the large distance between the touch signal layer and the display signal layer in conventional designs is avoided. This further reduces the risk of signal layer cracking and effectively isolates the electromagnetic interference of high-frequency display drive signals to weak touch sensing signals.

[0008] In one embodiment of this application, the inner signal region is provided with a bottom ground layer, a second inner signal layer, a signal shielding layer, a first inner signal layer and a power layer stacked from bottom to top. The power layer is located below the isolation ground layer, and adjacent conductive layers are isolated from each other by an insulating dielectric layer.

[0009] By adopting the above scheme and using a stacked design, a multi-layered, high-density interconnected independent wiring space is constructed. Through the overlapping of power layer, ground layer and signal shielding layer, a stable return path is provided and inter-layer crosstalk is shielded.

[0010] In one embodiment of this application, the projections of the touch signal layer, display signal layer and main ground layer on the horizontal plane at the ends away from the transition area are staggered to form a first stepped structure for electrical connection of the first IC; The projections of the first inner signal layer and the second inner signal layer away from the transition region on the horizontal plane are staggered to form a second stepped structure for electrical connection of the second IC.

[0011] By adopting the above scheme, the internal signal line layers can be directly exposed at the end of the rigid board area to form bonding surfaces of different depths. The first IC and the second IC do not need to use traditional vias to cross layers, but can directly bond to the signal planes of the corresponding depths. This eliminates the parasitic capacitance and parasitic inductance caused by vias, shortens the physical transmission path of high-frequency signals, and reduces signal attenuation. At the same time, the three-dimensional space of the Z-axis depth of the circuit board is utilized, providing a physical basis for reducing the overall height of the chip after mounting.

[0012] In one embodiment of this application, a groove is provided on the side of the touch display area away from the transition area, and the first IC and the second IC are embedded side by side in the groove and electrically connected.

[0013] By adopting the above scheme, the first IC and the second IC are embedded together in the recessed space inside the circuit board, so that the chip packaging thickness is absorbed by the thickness of the rigid board area itself, reducing the overall protrusion thickness of the circuit board including the IC and reducing the overall Z-axis height. In addition, the touch IC and the display IC are arranged side by side in the same physical cavity, shortening the interconnection lead length between the two chips and improving the high-speed collaborative communication efficiency of touch and display drivers.

[0014] In one embodiment of this application, the flexible circuit board region further includes an upper cover film and a lower cover film, wherein the upper cover film is disposed above the first flexible conductive layer and the lower cover film is disposed below the second flexible conductive layer.

[0015] By adopting the above solution, an insulating material is covered on the outer surface of the exposed flexible conductive layer, which provides physical protection against moisture, oxidation, and mechanical scratches for the fine circuits inside the flexible circuit board area. At the same time, the upper and lower covering films together with the inner flexible conductive layer and substrate form a symmetrical or nearly symmetrical stacked structure, which helps to keep the stress neutral layer near the flexible shielding layer when the board is bent, thereby further reducing the bending, tensile, and compressive stress on the outer conductive layer.

[0016] In one embodiment of this application, a subordinate rigid board area is further included. The subordinate rigid board area is provided with a second rigid layer, a signal output layer, an isolation layer, a signal receiving layer and a first rigid layer in sequence from bottom to top. One side of the signal output layer is connected to the second flexible conductive layer, the isolation layer is connected to the flexible shielding layer, and the signal receiving layer is connected to the first flexible conductive layer.

[0017] By adopting the above solution, the reinforcement of the subordinate rigid board area by the first rigid layer and the second rigid layer provides a support platform with sufficient mechanical strength for the mounting of external connectors or peripheral sensing components. This avoids point peeling and poor contact caused by direct insertion or force in the purely flexible area, and ensures the physical reliability of the signal input / output connection.

[0018] The second objective of this application is to provide a method for manufacturing an integrated touch display driver circuit board.

[0019] The technical solution is as follows: A method for fabricating an integrated touch display driver circuit board, comprising the following steps: S1: A display signal layer is formed on the upper surface of the flexible substrate, a touch signal layer is formed on the lower surface of the flexible substrate, and a grounding shielding layer is provided in the middle of the flexible substrate to obtain a flexible core board; S2: The bottom ground layer, the second inner signal layer, the signal shielding layer, the first inner signal layer and the power layer are stacked in sequence and then cured by pressing with a prepreg to form the inner signal area sub-board; S3: The flexible core board is placed in the middle layer, the main grounding layer is laminated on the top of the flexible core board, and the isolation grounding layer and the inner signal area sub-board are laminated in sequence below the flexible core board. The prepreg is pressed and cured within the preset rigid board area to form a whole laminate. The avoidance window boundaries of each layer of prepreg are progressively advanced in the horizontal direction, so that the projections of the subsequently formed connection edges D1, D2, and D3 on the horizontal plane are distributed in a stepped manner with intervals. S4: By using a controlled depth milling process, the rigid material layers above and below the flexible circuit board area are removed, so that the display signal layer and the touch signal layer are exposed in the flexible circuit board area, forming a first flexible conductive layer and a second flexible conductive layer respectively, and the grounding shielding layer is exposed in the flexible circuit board area to form a flexible shielding layer. S5: A cover film is attached above the first flexible conductive layer in the flexible board area, and a lower cover film is attached below the second flexible conductive layer; S6: At the end of the rigid board area away from the transition area, the conductive layer and dielectric layer of the preset area are removed layer by layer by controlled depth milling process to form a first step structure for electrical connection of the first IC and a second step structure for electrical connection of the second IC, and a groove is milled on the side of the touch display area away from the transition area. S7: The first IC and the second IC are embedded side by side into the groove and electrically connected to the first step structure and the second step structure, respectively.

[0020] By adopting the above scheme, this preparation method independently prepares the flexible core board and the inner rigid sub-board and then laminates them together as a whole board, ensuring the alignment accuracy of the multi-layer high-density circuit. At the same time, the controlled depth milling process is used to accurately remove the rigid dielectric and excess conductive layer in specific areas. This not only peels off the flexible board area with a consistent thickness in situ, but also forms a horizontally misaligned stress gradient buffer structure and grooves for direct chip connection. It does not require the introduction of complex special substrate thinning equipment. It directly utilizes the mature PCB subtractive manufacturing principle to realize a multi-step three-dimensional structure in the Z-axis direction, taking into account both the operability of the process implementation and the product yield.

[0021] In one embodiment of this application, step S8 is also included; S8: At the end of the flexible board area away from the rigid board area, a first rigid layer is laminated above the first flexible conductive layer, and a second rigid layer is laminated below the second flexible conductive layer. The first flexible conductive layer extends to form a signal receiving layer, the second flexible conductive layer extends to form a signal output layer, and the flexible shielding layer extends to form an isolation layer, thus forming the subordinate rigid board area.

[0022] By adopting the above solution, an integrated rigid interface area can be solidified in situ at the end of the flexible substrate in the same manufacturing cycle or continuous pressing process. This ensures the continuity of the signal layer from the flexible board area to the subordinate rigid board area, avoids the tolerance accumulation and interface impedance mutation caused by using external rigid boards for secondary pressing or welding, and improves the overall structural consistency of the board.

[0023] In one embodiment of this application, in step S6, the formation process of the first step structure is as follows: first, the main ground layer and the dielectric layer between it and the display signal layer are removed to expose the display signal layer as the first bonding surface; then, the display signal layer, the ground shield layer and the dielectric layer between them are further removed in the adjacent area to expose the touch signal layer as the second bonding surface. The formation process of the second step structure is as follows: first, the power layer and the dielectric layer below it are removed to expose the first inner signal layer as the third bonding surface, and then the first inner signal layer and the dielectric layer below it are further removed in the adjacent area to expose the second inner signal layer as the fourth bonding surface.

[0024] By adopting the above scheme, the physical thickness of the interlayer insulating dielectric layer itself is used as a stepped height difference. By peeling off the covering material layer by layer downwards without mechanically or chemically thinning the copper foil layer that serves as the bonding surface, the original copper thickness integrity and current carrying capacity of each signal layer bonding surface are ensured.

[0025] In one embodiment of this application, in step S3, the prepreg has a pre-opened clearance window in the flexible board area, so that after pressing and curing, the flexible core board remains flexible in the flexible board area and does not bond with the prepreg.

[0026] By adopting the above solution, it is ensured that the molten resin of the prepreg will not overflow and adhere to the surface of the flexible core board in the flexible board area under the high temperature and high pressure pressing conditions of the whole board. On the one hand, it provides a non-adhesive separation interface for subsequent milling processes, reducing the difficulty of peeling and the risk of substrate damage; on the other hand, it avoids the damage to the flexibility of the flexible board area caused by the residual rigid cured resin.

[0027] In summary, this application includes at least one of the following beneficial technical effects: by setting horizontally staggered connecting edges in the transition zone of the rigid-flexible bond, the stress concentration effect caused by the traditional vertical cutting surface is reduced, and the shear force during bending is dispersed to different cross sections for release, thereby improving the fatigue fracture resistance of the flexible conductive layer; at the same time, by using a grounding shielding layer to physically isolate the touch and display signal layers, a more compact stacked structure is set to reduce the bending radius, while effectively reducing the near-field interference of high-frequency display driving on weak touch signals, thus balancing mechanical lifespan and signal integrity.

[0028] By embedding the two ICs side by side in a recess in the rigid board area, the thickness of the board material is used to absorb the package height, reducing the overall Z-axis height of the circuit board. Combined with the stepped exposed signal step structure, the IC pins can be directly bonded to the inner layer signal plane, reducing the parasitic inductance and impedance discontinuity caused by traditional via cross-layer transmission. This not only shortens the physical path of signal transmission, but also improves the high-speed collaborative communication efficiency of touch response and display refresh.

[0029] By pre-setting avoidance windows on the prepreg, a non-bonded interface between rigid and flexible materials is constructed during the lamination stage, reducing the damage to the flexibility of the flexible board area caused by resin overflow. At the same time, by using controlled depth milling technology, the rigid capping layer can be peeled off and the stepped interconnect interface can be formed in the same step, avoiding the impact of traditional chemical etching on copper thickness consistency and improving product consistency and preparation yield. Attached Figure Description

[0030] Figure 1 This is a cross-sectional view of an integrated touch display driver circuit board provided in an embodiment of this application; Figure 2This is a cross-sectional view of the rigid board area of ​​an integrated touch display driver circuit board provided in the embodiments of this application; Figure 3 This is a cross-sectional view of the flexible circuit board area of ​​an integrated touch display driver circuit board provided in the embodiments of this application; Figure 4 This is a cross-sectional view of the transition area of ​​an integrated touch display driver circuit board provided in an embodiment of this application; Figure 5 This is a schematic diagram showing the connection between the first IC and the second IC of an integrated touch display driver circuit board provided in the embodiments of this application; Figure 6 This is a flowchart illustrating a method for fabricating an integrated touch display driver circuit board according to an embodiment of this application.

[0031] Explanation of reference numerals in the attached diagram: 1. Rigid board area; 11. Touch display area; 111. Isolation ground layer; 112. Touch signal layer; 113. Display signal layer; 114. Main ground layer; 115. Ground shield layer; 116. Groove; 12. Inner layer signal area; 121. Bottom ground layer; 122. Second inner layer signal layer; 123. Signal shield layer; 124. First inner layer signal layer; 125. Power layer; 2. Flexible board area; 21. Second flexible conductive layer; 22. First flexible conductive layer; 23. Flexible shield layer; 24. Upper cover film; 25. Lower cover film; 3. Transition area; 4. First IC; 5. Second IC; 6. Subordinate rigid board area; 61. Second rigid layer; 62. Signal output layer; 63. Isolation layer; 64. Signal receiving layer; 65. First rigid layer. Detailed Implementation

[0032] The following is in conjunction with the appendix Figures 1-6 This application provides a more detailed description of an integrated touch display driver circuit board and its fabrication method.

[0033] The integrated touch display driver circuit board provided in this application embodiment includes: a rigid board area 1 and a flexible board area 2.

[0034] The rigid board area 1 has an inner signal area 12 and a touch display area 11 arranged sequentially from bottom to top inside the rigid board area 1. The touch display area 11 has an isolation grounding layer 111, a touch signal layer 112, a display signal layer 113 and a main grounding layer 114 arranged sequentially from bottom to top. A grounding shielding layer 115 is arranged between the touch signal layer 112 and the display signal layer 113. The touch display area 11 also includes a flexible substrate. The display signal layer 113 is disposed on the upper surface of the flexible substrate, the touch signal layer 112 is disposed on the lower surface of the flexible substrate, and the grounding shielding layer 115 is disposed in the flexible substrate. The flexible circuit board area 2 is disposed on one side of the rigid circuit board area 1. The flexible circuit board area 2 is provided with a second flexible conductive layer 21 and a first flexible conductive layer 22 from bottom to top. The second flexible conductive layer 21 is connected to the touch signal layer 112, and the first flexible conductive layer 22 is connected to the display signal layer 113. A flexible shielding layer 23 is disposed between the second flexible conductive layer 21 and the first flexible conductive layer 22. The flexible shielding layer 23 is electrically connected to the ground shielding layer 115. The rigid board area 1 and the flexible board area 2 are interconnected and form a transition area 3 at the connection point. In the transition area 3, the projections of the connection line D1 between the second flexible conductive layer 21 and the touch signal layer 112, the connection line D2 between the flexible shielding layer 23 and the ground shielding layer 115, and the connection line D3 between the first flexible conductive layer 22 and the display signal layer 113 on the horizontal plane are arranged sequentially at intervals along the direction from the flexible board area 2 to the rigid board area 1, forming a stepped distribution.

[0035] In this embodiment, the overall thickness of the rigid board area 1 can be 0.8mm to 1.2mm, and the overall thickness of the flexible board area 2 can be 0.10mm to 0.20mm.

[0036] The flexible substrate is made of polyimide (PI) film with a thickness of 12.5 μm to 25 μm. The conductive lines of the touch signal layer 112 and the display signal layer 113 are made of rolled copper foil with a thickness of 9 μm to 18 μm. Rolled copper foil is chosen instead of electrolytic copper foil because the grain structure of rolled copper foil is fibrous along the rolling direction, which has better fatigue fracture resistance under repeated bending conditions.

[0037] The grounding shielding layer 115 is a copper foil or conductive paste layer embedded in the middle of the flexible substrate, with a thickness of 9μm to 12μm.

[0038] The horizontal length of the transition zone 3 along the direction from the flexible board area 2 to the rigid board area 1 is 1.0mm to 3.0mm. The horizontal distance between connecting edge lines D1 and D2 is 0.3mm to 1.0mm, and the horizontal distance between connecting edge lines D2 and D3 is 0.3mm to 1.0mm. Additionally, it should be noted that the principle for setting the above spacing is as follows: if the spacing is too small, the stress release effect of each layer's termination surface will be insufficient; if the spacing is too large, the area occupied by the transition zone 3 will increase, which is not conducive to the miniaturization of the entire board. The actual value needs to be determined comprehensively based on the overall board layer thickness and the minimum bending radius of the soft board area 2, generally ensuring that the spacing between adjacent connecting edges is not less than 3 times the thickness of the corresponding rigid material layer.

[0039] The inner signal region 12 is provided with a bottom ground layer 121, a second inner signal layer 122, a signal shielding layer 123, a first inner signal layer 124 and a power layer 125 stacked from bottom to top. The power layer 125 is located below the isolation ground layer 111, and adjacent conductive layers are isolated from each other by an insulating dielectric layer.

[0040] In this embodiment, each conductive layer of the inner signal region 12 can be made of electrolytic copper foil with a thickness of 18μm to 35μm. Since the inner signal region 12 is located inside the rigid board region 1 and does not bear bending, it is not required to use rolled copper foil.

[0041] An insulating dielectric layer is provided between each conductive layer. The insulating dielectric layer is made of FR-4 grade glass fiber reinforced epoxy resin substrate, and the thickness of a single dielectric layer is 60μm to 100μm.

[0042] The isolation grounding layer 111 is located between the touch display area 11 and the inner signal area 12. Its function is to electrically isolate the ground loop coupling between the high-sensitivity analog signal circuit of the touch display area 11 and the digital signal circuit of the inner signal area 12, so as to prevent digital switching noise from being injected into the touch signal layer 112 through the common ground path.

[0043] The power layer 125 adopts a large-area copper plating design with a copper foil thickness of 35μm to 70μm to meet the current carrying capacity required for power supply to the driver IC and reduce power impedance.

[0044] The projections of the touch signal layer 112, display signal layer 113 and main ground layer 114 away from the transition area 3 on the horizontal plane are staggered to form a first step structure for electrical connection of the first IC4. The projections of the first inner signal layer 124 and the second inner signal layer 122 away from the transition region 3 on the horizontal plane are staggered to form a second step structure for electrical connection of the second IC5.

[0045] In this embodiment, the first step structure includes a first mating surface and a second mating surface.

[0046] The first bonding surface is the copper foil surface of the display signal layer 113 exposed after removing the main ground layer 114 and the dielectric layer between it and the display signal layer 113. The second bonding surface is the copper foil surface of the touch signal layer 112 exposed after further removing the display signal layer 113, the ground shield layer 115 and the dielectric layer between them in the area adjacent to the first bonding surface. The second bonding surface is the copper foil surface of the touch signal layer 112 exposed after further removing the display signal layer 113 and the dielectric below it in the area adjacent to the first bonding surface.

[0047] The horizontal offset between the first bonding surface and the second bonding surface is 0.3 mm to 0.8 mm, and the vertical height difference depends on the cumulative thickness of the corresponding dielectric layer and copper foil layer, which is usually 60 μm to 150 μm.

[0048] The second step structure includes a third joint surface and a fourth joint surface.

[0049] The third bonding surface is the copper foil surface of the first inner signal layer 124 exposed after the power layer 125 and its covering medium are removed, and the fourth bonding surface is the copper foil surface of the second inner signal layer 122 exposed after the first inner signal layer 124 and its underlying medium are further removed in the region adjacent to the third bonding surface.

[0050] The design principles for the horizontal offset and vertical height difference between the third and fourth joint surfaces are the same as those for the first step structure.

[0051] In addition, the exposed copper foil surfaces of the first, second, third, and fourth bonding surfaces need to be surface treated before electrical connection. The surface treatment method is selected from at least one of electroless nickel-gold plating (ENIG), organic solder resist (OSP), or electroless nickel-palladium-gold plating (ENEPIG). Among them, electroless nickel-palladium-gold plating is preferred, with a nickel layer thickness of 3μm to 5μm, a palladium layer thickness of 0.05μm to 0.1μm, and a gold layer thickness of 0.03μm to 0.08μm, so as to balance the solder wettability of wire bonding and long-term storage oxidation resistance.

[0052] In this embodiment, the first IC4 is a Touch Display Driver Integrated Chip (TDDI) or a separate Display Driver IC, and the second IC5 is a Touch Controller IC or a Timing Controller (TCON).

[0053] The electrical connection between the first IC4 and the first step structure, and between the second IC5 and the second step structure, can be at least one of gold wire bonding, copper wire bonding, or flip chip bonding.

[0054] When using wire bonding, the diameter of the bonding wire is 18μm to 25μm, the size of the bonding pad is not less than 60μm × 60μm, and the center-to-center distance between adjacent pads is not less than 45μm.

[0055] A groove 116 is provided on the side of the touch display area 11 away from the transition area 3. The first IC4 and the second IC5 are embedded side by side in the groove 116 and are electrically connected.

[0056] In this embodiment, the groove 116 is formed by controlled depth milling. The depth of the groove 116 is determined according to the package thickness of the embedded IC die, and is usually 0.15mm to 0.40mm, so that after the IC is embedded, its top surface is flush with or 0 to 50μm below the surface of the rigid board area 1.

[0057] The flatness tolerance of the bottom surface of groove 116 is controlled within ±20μm to ensure that the bottom surface of the chip is fully attached to the bottom of the groove.

[0058] In this embodiment, after the first IC4 and the second IC5 are embedded in the groove 116, the back of the chip is fixed to the bottom of the groove 116 by a conductive or non-conductive adhesive film.

[0059] When there is a grounding pad on the back of the chip, a conductive adhesive film is used to achieve a heat dissipation grounding path on the back metal surface; when there are no electrical requirements on the back of the chip, a non-conductive adhesive film can be used. The curing temperature of the conductive adhesive film is 150℃~180℃, and the curing time is 30min~60min.

[0060] The minimum horizontal distance between the first IC4 and the second IC5 is not less than 0.2mm. If high-speed interconnection and communication are required between the two chips, interconnection lines can be pre-laid on the copper foil layer at the bottom of the groove 116, or direct signal jumpers between the chips can be achieved through wire bonding.

[0061] The flexible circuit board area 2 further includes an upper cover film 24 and a lower cover film 25. The upper cover film 24 is disposed above the first flexible conductive layer 22, and the lower cover film 25 is disposed below the second flexible conductive layer 21.

[0062] In this embodiment, both the upper cover film 24 and the lower cover film 25 are polyimide (PI) based cover films, which are composite films with a PI film layer and an epoxy or acrylic adhesive layer.

[0063] The PI film layer has a thickness of 12.5 μm, the adhesive layer has a thickness of 15 μm to 25 μm, and the total thickness of the cover film has a thickness of 25 μm to 37.5 μm. The material specifications and thickness of the upper cover film 24 and the lower cover film 25 are preferably the same, so that the cross-sectional structure of the flexible board area 2 forms a symmetrical or approximately symmetrical stacked configuration relative to the plane where the flexible shielding layer 23 is located, thereby constraining the stress neutral plane during bending to the vicinity of the flexible shielding layer 23.

[0064] It also includes a subordinate rigid plate area 6, in which a second rigid layer 61, a signal output layer 62, an isolation layer 63, a signal receiving layer 64 and a first rigid layer 65 are arranged sequentially from bottom to top inside the subordinate rigid plate area 6. One side of the signal output layer 62 is connected to the second flexible conductive layer 21, the isolation layer 63 is connected to the flexible shielding layer 23, and the signal receiving layer 64 is connected to the first flexible conductive layer 22.

[0065] In this embodiment, both the first rigid layer 65 and the second rigid layer 61 are made of FR-4 rigid substrate with a single layer thickness of 0.1mm to 0.3mm. Their function is to provide the mechanical support rigidity required for mounting the connector in the subordinate rigid board area 6.

[0066] It should be noted that the signal output layer 62 and the signal receiving layer 64 are natural extensions of the same flexible copper foil layer as the second flexible conductive layer 21 and the first flexible conductive layer 22 in the flexible board area 2, respectively. That is, they are physically part of the same continuous trace and there is no welding or crimping interface.

[0067] The second objective of this application is to provide a method for manufacturing an integrated touch display driver circuit board.

[0068] The technical solution is as follows: A method for fabricating an integrated touch display driver circuit board, comprising the following steps: S1: A display signal layer 113 is formed on the upper surface of the flexible substrate, a touch signal layer 112 is formed on the lower surface of the flexible substrate, and a grounding shielding layer 115 is provided in the middle of the flexible substrate to obtain a flexible core board. S2: The bottom ground layer 121, the second inner signal layer 122, the signal shielding layer 123, the first inner signal layer 124 and the power layer 125 are stacked in sequence and then pressed and cured by prepreg to form the inner signal area sub-board. S3: The flexible core board is placed in the middle layer, the main grounding layer 114 is laminated on the top of the flexible core board, and the isolation grounding layer 111 and the inner signal area sub-board are laminated sequentially on the bottom of the flexible core board. The prepreg is pressed and cured within the preset rigid board area 1 to form a whole laminate. The avoidance window boundaries of each layer of prepreg are progressively advanced in the horizontal direction, so that the projections of the subsequently formed connection edges D1, D2, and D3 on the horizontal plane are distributed in a stepped manner with intervals. S4: By using a controlled depth milling process, the rigid material layers above and below the flexible circuit board area 2 are removed, so that the display signal layer 113 and the touch signal layer 112 are exposed in the flexible circuit board area 2, forming the first flexible conductive layer 22 and the second flexible conductive layer 21 respectively, and the grounding shielding layer 115 is exposed in the flexible circuit board area 2 to form a flexible shielding layer 23. S5: A cover film 24 is attached above the first flexible conductive layer 22 in the flexible board area 2, and a lower cover film 25 is attached below the second flexible conductive layer 21. S6: At the end of the rigid plate area 1 away from the transition area 3, the conductive layer and dielectric layer of the preset area are removed layer by layer by controlled depth milling process to form a first step structure for electrical connection of the first IC4 and a second step structure for electrical connection of the second IC5, and a groove 116 is milled on the side of the touch display area 11 away from the transition area 3. S7: The first IC4 and the second IC5 are embedded side by side into the groove 116 and electrically connected to the first step structure and the second step structure, respectively.

[0069] In this embodiment, in step S1, the flexible substrate is a double-sided flexible copper clad laminate (FCCL), the substrate layer is a polyimide film with a thickness of 12.5μm to 25μm, and the surface copper is rolled copper foil (RA copper foil) with a thickness of 9μm to 18μm.

[0070] The grounding shielding layer 115 can be formed by embedding copper foil in the intermediate layer of the PI substrate during the film-making stage, with a thickness of 5μm to 12μm.

[0071] The circuit patterning of the display signal layer 113 and the touch signal layer 112 adopts the subtractive method (etching method) or the semi-additive method (SAP / mSAP). The minimum line width / line spacing is determined according to the design rules. The typical line width / line spacing of the touch signal layer 112 is 30μm / 30μm to 50μm / 50μm, and the typical line width / line spacing of the display signal layer 113 is 20μm / 20μm to 40μm / 40μm.

[0072] In step S2, the inner signal area sub-board is laminated using FR-4 prepreg with a resin content of 55% to 65% and a single sheet thickness of 50 μm to 120 μm after curing. The specific number of laminates is determined based on the thickness of the target dielectric layer.

[0073] In step S3, during the lamination of the entire board, the prepreg used to connect the flexible core board with the upper and lower rigid layers is also FR-4 prepreg or low-flow prepreg.

[0074] Within the preset flexible board area 2, each prepreg has an avoidance window pre-cut by die-cutting or laser cutting. The window size is recessed inward by 0.5mm to 1.5mm along each side from the actual boundary of the flexible board area 2. This recess is used to compensate for edge overflow caused by resin flow during the pressing process, ensuring that the actual boundary of the prepreg after curing matches the designed boundary of the rigid board area 1.

[0075] In addition, the surface of the flexible core board within the prepreg window can be pre-covered with a peelable release film, made of polytetrafluoroethylene (PTFE) film or PET film coated with silicone release agent, to further prevent a small amount of overflowing resin from adhering to the flexible core board.

[0076] In step S4, controlled depth milling is performed using a mechanical milling cutter or a laser milling method.

[0077] In step S3, it should be noted that the stepped distribution of connecting edges D1, D2, and D3 is actually predetermined in the lamination stage of step S3 by the difference in the boundary position of the prepreg window of each layer. That is, the window boundary of the upper main grounding layer 114 corresponding to the prepreg is located closest to the center of the rigid board area 1, the interface corresponding to the grounding shielding layer 115 is next, and the window boundary of the lower isolation grounding layer 111 corresponding to the prepreg is located closest to the flexible board area 2. Thus, after milling and uncovering, the horizontal staggered distribution of the three connecting edges D1, D2, and D3 is naturally formed.

[0078] In practice, the offset of the window boundary of the three-layer prepreg corresponds to the design values ​​of the D1-D2 spacing and the D2-D3 spacing, respectively.

[0079] In steps S6 and S7, when milling the stepped structure at controlled depth, the same equipment and process type as in step S4 are used. When milling layer by layer, the surface of each copper foil layer is used as the depth stop reference. After each step surface is milled, the depth is checked. Only after confirming that the deviation between the actual milling depth and the design value is within ±20μm can the next level of milling be carried out.

[0080] The formation process of the first step structure is as follows: first, the main ground layer 114 and the dielectric layer between it and the display signal layer 113 are removed to expose the display signal layer 113 as the first bonding surface; then, the display signal layer 113, the ground shield layer 115 and the dielectric layer between them are further removed in the adjacent area to expose the touch signal layer 112 as the second bonding surface. The formation process of the second step structure is as follows: first, the power layer 125 and the dielectric layer below it are removed to expose the first inner signal layer 124 as the third bonding surface, and then the first inner signal layer 124 and the dielectric layer below it are further removed in the adjacent area to expose the second inner signal layer 122 as the fourth bonding surface.

[0081] In step S3, the prepreg has a clearance window pre-opened in the flexible board area 2 so that after pressing and curing, the flexible core board remains flexible in the flexible board area 2 and does not bond with the prepreg.

[0082] In this embodiment, during the pressing process, in order to prevent the flexible core board in the soft board area 2 from undergoing local deformation or wrinkling under high pressure due to the lack of semi-cured sheet support, a compressible silicone rubber liner or aluminum foil liner can be temporarily filled in the avoidance window area as a pressure equalization medium. The liner is removed together with the isolation protective film after pressing is completed.

[0083] In summary, by integrating the touch signal layer 112 and the display signal layer 113 onto the upper and lower surfaces of the same flexible core board, and setting a grounding shielding layer 115 between them, electromagnetic isolation between the signal layers is achieved while reducing the physical distance between the two signal layers. This results in a smaller radius of curvature and a gentler bending angle when the entire board is bent in the rigid-flex transition zone 3, reducing the risk of stress concentration in the conductive layer and metal fatigue caused by bending. The horizontal staggered design of the three connecting edges in the transition zone 3 further decomposes the abrupt change in cross-sectional stiffness into multi-level gradient release, improving the connection reliability under repeated bending conditions. The combination of the stepped chip direct connection structure and the embedded mounting method eliminates the signal loss link of the intermediate via interconnection in the traditional design, and incorporates the chip packaging height into the board thickness, achieving simultaneous optimization of electrical performance and Z-axis space utilization. The fabrication method is based on a mature rigid-flex board lamination and controlled-depth milling process system. Through pre-windowing of the prepreg and a step-by-step milling strategy, the above-mentioned complex stacked structure was processed without introducing special equipment or materials, demonstrating industrial feasibility.

[0084] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A touch display driver integrated circuit board, characterized in that, include: The rigid board area (1) has an inner signal area (12) and a touch display area (11) arranged sequentially from bottom to top inside the rigid board area (1). The touch display area (11) has an isolation grounding layer (111), a touch signal layer (112), a display signal layer (113) and a main grounding layer (114) arranged sequentially from bottom to top. A grounding shielding layer (115) is arranged between the touch signal layer (112) and the display signal layer (113). The touch display area (11) also includes a flexible substrate. The display signal layer (113) is disposed on the upper surface of the flexible substrate, the touch signal layer (112) is disposed on the lower surface of the flexible substrate, and the grounding shielding layer (115) is disposed in the flexible substrate. A flexible circuit board area (2) is disposed on one side of the rigid circuit board area (1). The flexible circuit board area (2) is provided with a second flexible conductive layer (21) and a first flexible conductive layer (22) from bottom to top. The second flexible conductive layer (21) is connected to the touch signal layer (112), and the first flexible conductive layer (22) is connected to the display signal layer (113). A flexible shielding layer (23) is disposed between the second flexible conductive layer (21) and the first flexible conductive layer (22). The flexible shielding layer (23) is electrically connected to the ground shielding layer (115). The rigid board area (1) and the flexible board area (2) are connected to each other and form a transition area (3) at the connection. In the transition area (3), the projections of the connection line D1 between the second flexible conductive layer (21) and the touch signal layer (112), the connection line D2 between the flexible shielding layer (23) and the ground shielding layer (115), and the connection line D3 between the first flexible conductive layer (22) and the display signal layer (113) on the horizontal plane are arranged sequentially at intervals along the direction from the flexible board area (2) to the rigid board area (1), forming a stepped distribution.

2. The integrated touch display driver circuit board according to claim 1, characterized in that: The inner signal region (12) is provided with a bottom ground layer (121), a second inner signal layer (122), a signal shielding layer (123), a first inner signal layer (124), and a power layer (125) stacked from bottom to top. The power layer (125) is located below the isolation ground layer (111), and adjacent conductive layers are isolated from each other by an insulating dielectric layer.

3. The integrated touch display driver circuit board according to claim 2, characterized in that: The projections of the touch signal layer (112), display signal layer (113) and main ground layer (114) away from the transition area (3) on the horizontal plane are staggered to form a first step structure for electrical connection of the first IC (4); The projections of the first inner signal layer (124) and the second inner signal layer (122) away from the transition region (3) on the horizontal plane are staggered to form a second step structure for electrical connection of the second IC (5).

4. The integrated touch display driver circuit board according to claim 3, characterized in that: The touch display area (11) has a groove (116) on the side away from the transition area (3). The first IC (4) and the second IC (5) are embedded side by side in the groove (116) and are electrically connected.

5. The integrated touch display driver circuit board according to claim 1, characterized in that: The flexible circuit board area (2) further includes an upper cover film (24) and a lower cover film (25). The upper cover film (24) is disposed above the first flexible conductive layer (22), and the lower cover film (25) is disposed below the second flexible conductive layer (21).

6. The integrated touch display driver circuit board according to claim 1, characterized in that: It also includes a subordinate rigid plate area (6), in which a second rigid layer (61), a signal output layer (62), an isolation layer (63), a signal receiving layer (64) and a first rigid layer (65) are arranged sequentially from bottom to top inside the subordinate rigid plate area (6). One side of the signal output layer (62) is connected to the second flexible conductive layer (21), the isolation layer (63) is connected to the flexible shielding layer (23), and the signal receiving layer (64) is connected to the first flexible conductive layer (22).

7. A method for manufacturing an integrated touch display driver circuit board, characterized in that, Includes the following steps: S1: A display signal layer (113) is formed on the upper surface of the flexible substrate, a touch signal layer (112) is formed on the lower surface of the flexible substrate, and a grounding shield layer (115) is provided in the middle of the flexible substrate to obtain a flexible core board. S2: The bottom ground layer (121), the second inner signal layer (122), the signal shielding layer (123), the first inner signal layer (124) and the power layer (125) are stacked in sequence and then cured by pressing with a prepreg to form the inner signal area sub-board; S3: The flexible core board is placed in the middle layer, the main grounding layer (114) is laminated on the top of the flexible core board, and the isolation grounding layer (111) and the inner signal area sub-board are laminated sequentially below the flexible core board. The prepreg is pressed and cured within the preset rigid board area (1) to form a whole board laminate. The avoidance window boundaries of each layer of prepreg are progressively advanced in the horizontal direction, so that the projections of the subsequently formed connection edges D1, D2, and D3 on the horizontal plane are distributed in a stepped manner with intervals. S4: By using a controlled depth milling process, the rigid material layers above and below the flexible circuit board area (2) are removed, so that the display signal layer (113) and the touch signal layer (112) are exposed in the flexible circuit board area (2), forming a first flexible conductive layer (22) and a second flexible conductive layer (21) respectively. The grounding shielding layer (115) is exposed in the flexible circuit board area (2) to form a flexible shielding layer (23). S5: A cover film (24) is attached above the first flexible conductive layer (22) in the flexible board area (2), and a lower cover film (25) is attached below the second flexible conductive layer (21); S6: At one end of the rigid plate area (1) away from the transition area (3), the conductive layer and dielectric layer of the preset area are removed layer by layer by controlled depth milling process to form a first step structure for electrical connection of the first IC (4) and a second step structure for electrical connection of the second IC (5), and a groove (116) is milled on the side of the touch display area (11) away from the transition area (3). S7: The first IC (4) and the second IC (5) are embedded side by side into the groove (116) and electrically connected to the first step structure and the second step structure respectively.

8. The integrated touch display driver circuit board according to claim 7, characterized in that: It also includes step S8; S8: At one end of the flexible board area (2) away from the rigid board area (1), a first rigid layer (65) is laminated above the first flexible conductive layer (22), and a second rigid layer (61) is laminated below the second flexible conductive layer (21). The first flexible conductive layer (22) extends to form a signal receiving layer (64), the second flexible conductive layer (21) extends to form a signal output layer (62), and the flexible shielding layer (23) extends to form an isolation layer (63), thus forming the subordinate rigid board area (6).

9. The integrated touch display driver circuit board according to claim 7, characterized in that: In step S6, the formation process of the first step structure is as follows: first, the main ground layer (114) and the dielectric layer between it and the display signal layer (113) are removed to expose the display signal layer (113) as the first bonding surface; then, the display signal layer (113), the ground shield layer (115) and the dielectric layer between them are further removed in the adjacent area to expose the touch signal layer (112) as the second bonding surface. The formation process of the second step structure is as follows: first, the power layer (125) and the dielectric layer below it are removed to expose the first inner signal layer (124) as the third bonding surface, and then the first inner signal layer (124) and the dielectric layer below it are further removed in the adjacent area to expose the second inner signal layer (122) as the fourth bonding surface.

10. The integrated touch display driver circuit board according to claim 7, characterized in that: In step S3, the prepreg has a clearance window pre-opened in the flexible board area (2) so that after pressing and curing, the flexible core board remains flexible in the flexible board area (2) and does not bond with the prepreg.

Images