Functional backboard and light-emitting device

Abstract

The invention discloses a functional backboard and a light-emitting device, and relates to the technical field of display. A first flexible circuit board in the functional backboard is fixedly arranged on a second surface of a substrate through a first fitting structure. The first flexible circuit board is provided with a first area of a single-layer conductive structure and a second area of a double-layer conductive structure. Compared with a single-layer conductive structure, the double-layer conductive structure has the advantages that the proportion of the conductive material in unit space is higher, so that the expansion amount of the second area in the high-temperature process differs greatly from the expansion amount of the first fitting structure relative to the expansion amount of the first area. The thickness of the target part, located in the second area, of the first attaching structure is small, an expansion space can be provided for expansion of the attaching material of the first attaching structure, then the total expansion amount of the first attaching structure can be reduced, and the situation that the difference between the expansion amount of the first attaching structure and the expansion amount of the second area is too large is avoided; therefore, the possibility of warping of the functional backplane is reduced, and the yield of the functional backplane is improved.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a functional backplane and a light-emitting device. Background Art

[0002] Light-emitting devices are currently developing towards ultra-narrow borders or even borderless to increase the screen-to-body ratio.

[0003] In the related art, in order to increase the screen-to-body ratio of the light-emitting device, the electrode wiring on the side of the functional backplane used for light emission can usually be led to the other side of the functional backplane through the side wiring, and the first drive signal is provided to the electrode wiring of the functional backplane through the external circuit structure arranged on the other side. In order to realize the signal transmission between the side wiring and the external circuit structure, it is necessary to design a flexible circuit board on the other side of the functional backplane, and the flexible circuit board is connected to the side wiring and the external circuit structure, and the external circuit structure is connected to the electrode wiring through the side wiring connected to the flexible circuit board. In addition, the flexible circuit board can be bonded to the substrate of the functional backplane through the bonding structure to realize the fixed connection between the flexible circuit board and the substrate.

[0004] However, both sides of the functional backplane in the related art are prone to warping, and the yield of the functional backplane is low. Summary of the invention

[0005] The present application provides a functional backplane and a light-emitting device, which can solve the problem in the related art that the two sides of the functional backplane are prone to warping and the yield of the functional backplane is low. The technical solution is as follows:

[0006] In one aspect, a functional backplane is provided, the functional backplane comprising:

[0007] substrate;

[0008] a plurality of electronic components located on a first surface of the substrate;

[0009] a first connecting wire, one end of which is located on the first surface of the substrate and connected to the electronic component, and the other end of which is bent from the first surface of the substrate and located on the second surface of the substrate;

[0010] a first flexible circuit board and a first bonding structure, wherein the first flexible circuit board is located on a second surface of the substrate away from the plurality of electronic components, the first bonding structure is located between the substrate and the first flexible circuit board, the first flexible circuit board is fixedly arranged on the second surface of the substrate through the first bonding structure, the first flexible circuit board is connected to the other end of the first connecting wire, the first flexible circuit board is also connected to a first external circuit structure, and the first flexible circuit board is used to transmit a first driving signal provided by the first external circuit structure to the electronic component through the first connecting wire;

[0011] Among them, the first flexible circuit board has a first area and a second area, the first flexible circuit board includes a first conductive structure located in the first area, and a second conductive structure and a third conductive structure located in the second area and stacked; the first bonding structure has a plurality of target parts in the shape of strips located at least in the second area, and the thickness of the target part of the first bonding structure is less than the thickness of other parts of the first bonding structure except the target part.

[0012] Optionally, the plurality of target portions include a plurality of first grooves extending along the first direction and spaced apart in the second direction;

[0013] The first direction is an arrangement direction of the first regions and the second regions, and the second direction is perpendicular to the arrangement direction of the first regions and the second regions.

[0014] Optionally, the plurality of target portions further include a plurality of second grooves extending along the second direction and spaced apart in the second direction;

[0015] At least some of the plurality of second grooves are in communication with the first groove.

[0016] Optionally, the plurality of second grooves are located in a middle portion of the second area in the first direction.

[0017] Optionally, a distance between two adjacent first grooves along the second direction, and a distance between two adjacent second grooves along the second direction are both greater than or equal to 10 mm;

[0018] The width of the first groove ranges from 1 mm to 5 mm, the length of the first groove is equal to the length of the second area along the first direction, the width of the second groove ranges from 0.5 mm to 2 mm, and the length of the second groove is less than the spacing between two adjacent second grooves along the second direction.

[0019] Optionally, the plurality of target portions further include a third groove extending along the second direction, and the length of the third groove in the second direction is equal to the length of the first fitting structure in the second direction;

[0020] Wherein, the third groove is located at the boundary between the first area and the second area.

[0021] Optionally, the plurality of target portions include a plurality of fourth grooves extending along the first direction and spaced apart in the second direction, and a plurality of fifth grooves extending along the second direction and spaced apart in the first direction;

[0022] Wherein, the plurality of fourth grooves and the plurality of fifth grooves form a grid shape.

[0023] Optionally, the widths of the fourth groove and the fifth groove are both in the range of 100 microns to 150 microns, and the spacing between two adjacent fourth grooves in the second direction and the spacing between two adjacent fifth grooves in the first direction are both greater than or equal to 300 microns.

[0024] Optionally, the plurality of fourth grooves and the plurality of fifth grooves are also located in the first area.

[0025] Optionally, the first bonding structure includes a bonding material, and other parts of the first bonding structure except the target part are the parts of the first bonding structure having the bonding material, and the target part of the first bonding structure is the part of the first bonding structure not having the bonding material.

[0026] On the other hand, a functional backplane is provided, the functional backplane comprising:

[0027] substrate;

[0028] a plurality of electronic components on a first surface of the substrate;

[0029] a first connecting wire, one end of which is located on the first surface of the substrate and connected to the electronic component, and the other end of which is bent from the first surface of the substrate and located on the second surface of the substrate;

[0030] a first flexible circuit board and a first bonding structure, wherein the first flexible circuit board is located on a second surface of the substrate away from the plurality of electronic components, the first bonding structure is located between the substrate and the first flexible circuit board, the first flexible circuit board is fixedly arranged on the second surface of the substrate through the first bonding structure, the first flexible circuit board is connected to the other end of the first connecting wire, the first flexible circuit board is also connected to a first external circuit structure, and the first flexible circuit board is used to transmit a first driving signal provided by the first external circuit structure to the electronic component through the first connecting wire;

[0031] The first flexible circuit board has a first area and a second area, the first flexible circuit board includes a first conductive structure located in the first area, and a second conductive structure and a third conductive structure located in the second area and stacked, the first conductive structure, the second conductive structure and the third conductive structure are made of the same material; the first bonding structure includes a first part located in the first area and a second part located in the second area, and the difference between the thermal expansion coefficient of the material of the second part and the thermal expansion coefficient of the material of the first conductive structure is less than 1 part per million per degree Celsius.

[0032] Optionally, materials of the first conductive structure, the second conductive structure and the third conductive structure are all copper;

[0033] The material of the second portion has a coefficient of thermal expansion less than or equal to 20 parts per million per degree Celsius.

[0034] Optionally, the material of the second portion is different from the material of the first portion, and the thermal expansion coefficient of the material of the second portion is smaller than the thermal expansion coefficient of the material of the first portion.

[0035] Optionally, the functional backplane further includes:

[0036] a second connecting wire, one end of which is located on the first surface of the substrate and connected to the electronic component, and the other end of which is bent from the second surface of the substrate and located on the second surface of the substrate, the second surface being opposite to the first surface;

[0037] a second flexible circuit board and a second bonding structure, wherein the second flexible circuit board is located on a second surface of the substrate away from the electronic component, and the second flexible circuit board and the first flexible circuit board are spaced apart in a first direction, the second bonding structure is located between the substrate and the second flexible circuit board, the second flexible circuit board is fixedly arranged on the second surface of the substrate through the second bonding structure, the second flexible circuit board is connected to the other end of the second connecting wire, the second flexible circuit board is also connected to a second external circuit structure, and the second flexible circuit board is used to transmit a second driving signal provided by the second external circuit structure to the electronic component through the second connecting wire;

[0038] The second flexible circuit board includes a fourth conductive structure, and each region of the second bonding structure has the same thickness.

[0039] In yet another aspect, a light emitting device is provided, the light emitting device comprising: a power supply component and a functional backplane as described in the above aspect;

[0040] Wherein, the power supply component is used to supply power to the functional backplane.

[0041] The beneficial effects of the technical solution provided by this application include at least:

[0042] The present application provides a functional backplane and a light-emitting device, in which a first flexible circuit board is fixedly arranged on the second surface of a substrate through a first bonding structure. The first flexible circuit board has a first region of a single-layer conductive structure and a second region of a double-layer conductive structure. Since the proportion of conductive material in a unit space of a double-layer conductive structure is higher than that of a single-layer conductive structure, the expansion amount of the second region of the double-layer conductive structure during a high temperature process is greater than the expansion amount of the first region of the single-layer conductive structure, and is more different from the expansion amount of the first bonding structure. The present application designs the thickness of the target part located in the second region of the first bonding structure to be smaller, which can provide expansion space for the expansion of the bonding material of the first bonding structure, thereby reducing the total expansion amount of the first bonding structure. This can avoid the expansion amount of the first bonding structure being too large, resulting in a large difference in the expansion amount of the second region of the first flexible circuit board, thereby avoiding the possibility of warping of the functional backplane and improving the yield of the functional backplane. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 It is a cross-sectional view of a functional backplane provided by the related art;

[0045] Figure 2 It is a front view of a circuit board provided by the related technology;

[0046] Figure 3 It is a back top view of a circuit board provided by the related technology;

[0047] Figure 4 is a cross-sectional view of a functional backplane provided in an embodiment of the present application;

[0048] Figure 5 is a top view of a first flexible circuit board provided in an embodiment of the present application;

[0049] Figure 6 yes Figure 5 Cross-section along the MM direction;

[0050] Figure 7 It is a schematic diagram of laminating a first flexible circuit board onto a substrate using a first laminating structure provided in an embodiment of the present application;

[0051] Figure 8 is a schematic diagram of substrate warping provided in an embodiment of the present application;

[0052] Fig. 9 is a schematic diagram of a first flexible circuit board and a first bonding structure provided in an embodiment of the present application;

[0053] Fig.10 is a schematic diagram of another first flexible circuit board and a first bonding structure provided in an embodiment of the present application;

[0054] Fig.11 is a schematic diagram of another first flexible circuit board and a first bonding structure provided in an embodiment of the present application;

[0055] Fig.12 is a top view of a first surface of a functional backplane provided in an embodiment of the present application;

[0056] Fig.13 is a top view of a second surface of a functional backplane provided in an embodiment of the present application;

[0057] Fig.14 is a schematic diagram of another first flexible circuit board and a first bonding structure provided by an embodiment of the present application;

[0058] Fig.15 is a partial schematic diagram of a first bonding structure provided in an embodiment of the present application;

[0059] Fig.16is a schematic diagram of a release film provided in an embodiment of the present application;

[0060] Fig.17 is a schematic diagram of another release film provided in an embodiment of the present application;

[0061] Fig.18 is a schematic diagram of another first flexible circuit board and a first bonding structure provided in an embodiment of the present application;

[0062] Fig.19 It is a partial three-dimensional schematic diagram of a release film provided in an embodiment of the present application;

[0063] Fig. 20 is a schematic diagram of a first conductive layer of a first flexible circuit board provided in an embodiment of the present application;

[0064] Fig.21 is a schematic diagram of a second conductive layer of a first flexible circuit board provided in an embodiment of the present application;

[0065] Fig. 22 is a cross-sectional view of a first flexible circuit board provided in an embodiment of the present application;

[0066] Fig.23 is a partial schematic diagram of a first conductive layer of a first flexible circuit board provided in an embodiment of the present application;

[0067] Fig.24 is a partial schematic diagram of a first conductive layer of another first flexible circuit board provided in an embodiment of the present application;

[0068] Fig.25 yes Fig.21 A partial schematic diagram of

[0069] Fig.26 is a schematic diagram of a second flexible circuit board provided in an embodiment of the present application;

[0070] Fig. 27 This is a schematic diagram of another first flexible circuit board and a first bonding structure provided in an embodiment of the present application. DETAILED DESCRIPTION

[0071] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0072] Some embodiments of the present disclosure provide a light-emitting device, which includes a functional backplane and may also include other components. For example, it may include a circuit for providing an electrical signal to the functional backplane to drive the functional backplane to emit light. The circuit may be called a control circuit and may include a circuit board and / or an integrated circuit (IC) electrically connected to the functional backplane.

[0073] Optionally, the light-emitting device may further include a power supply component, which may be used to supply power to the functional backplane.

[0074] In some embodiments, the light emitting device may be a lighting device, in which case the light emitting device is used as a light source to achieve a lighting function. For example, the light emitting device may be a backlight module in a liquid crystal display device, a lamp for internal or external lighting, or various signal lights.

[0075] In other embodiments, the light-emitting device may be a display device, in which case the functional backplane is a display substrate for realizing the function of displaying an image (i.e., a picture). The light-emitting device may include a display or a product including a display. Among them, the display may be a flat panel display (Flat Panel Display, FPD), a micro display, etc. If divided according to whether the user can see the back of the display, the display may be a transparent display or an opaque display. If divided according to whether the display can be bent or curled, the display may be a flexible display or an ordinary display (which may be called a rigid display). For example, products including displays may include: computer monitors, televisions, billboards, laser printers with display functions, telephones, mobile phones, personal digital assistants (Personal Digital Assistant, PDA), laptop computers, digital cameras, camcorders, viewfinders, vehicles, large-area walls, theater screens or stadium signs, etc.

[0076] Some embodiments of the present disclosure provide a functional backplane, such as Figure 1 and Figure 2 As shown, the functional backplane 100 includes: a circuit board 101, and at least one electronic component 102 arranged on the circuit board 101. The electronic component 102 may include a micro light emitting diode, a micro integrated circuit chip, a micro sensor, a micro driver, etc., which are not limited here.

[0077] In some embodiments, taking the electronic component 102 as a micro-light emitting diode as an example, the functional backplane 100 can be used as a backlight source or a display device. In the case where the functional backplane 100 is used as a backlight source, a passive display panel can be used to display a full-color picture, such as a liquid crystal display panel (LCD). At this time, the functional backplane 100 as a whole can emit monochromatic light or polychromatic light (such as white light). By arranging multiple micro-light emitting diodes in a matrix and combining regional dimming technology, more sophisticated brightness control and higher color contrast can be achieved. In the case where the functional backplane 100 is used as a display device, the functional backplane 100 can be provided with micro-light emitting diodes that can emit light of different colors, which cooperate with each other to achieve the display of a full-color picture, which can have higher brightness and contrast.

[0078] At present, considering the process yield and manufacturing cost, when preparing large-size products, multiple functional back panels 100 can be spliced ​​together. In order to avoid the sense of separation between adjacent functional back panels due to splicing, which affects the user experience, the functional back panel is designed to have an ultra-narrow frame or even no frame to present a seamless splicing effect. This is the development direction in the field.

[0079] Micro-LED display technology is recognized as a very promising third-generation display technology, which is easier to implement small-size splicing technology to assemble infinitely larger size displays. Micro-LED displays can be Micro LED (MicroLight Emitting Diode) or mini LED (Mini Light Emitting Diode).

[0080] In order to achieve ultra-narrow border display, such as Figures 1 to 3 As shown, in the related art, two opposite surfaces of the substrate S of the circuit board 10 are provided with routing, specifically: the first surface of the substrate S is provided with a routing F1 for connecting to the electronic component 102, and the lead-out portion D of the routing F1 is led to the second surface of the substrate S through the side routing C, and is electrically connected to the routing F2 (such as at least one fan-out routing) provided on the second surface of the substrate S of the circuit board 101, such as making the binding area B on the second surface of the substrate S of the circuit board 10, thereby realizing a narrow frame design. However, routing is provided on both surfaces of the substrate S, which may easily cause scratches on one of the surface circuits during the manufacturing process, which is not conducive to ensuring the product yield and makes the production cost higher.

[0081] The first option, refer to Figure 4 The functional backplane 200 may include a substrate 201 , a plurality of electronic components 202 located on a first surface 201 a of the substrate 201 , a first connecting trace 203 , a first flexible circuit board 204 and a first bonding structure 205 .

[0082] The substrate 201 may be a glass substrate 201. Each of the electronic components 202 may include a pixel unit, and the pixel units included in the multiple electronic components 202 may have different colors. For example, the multiple electronic components 202 include a red (red, R) pixel unit, a green (green, G) pixel unit, and a blue (blue, B) pixel unit.

[0083] One end of the first connection trace 203 is located on the first surface 201a of the substrate 201 and is connected to the electronic component 202. The other end of the first connection trace 203 is bent from the first side surface 201c of the substrate 201 and is located on the second surface 201b of the substrate 201. That is, a portion of the first connection trace 203 is located on the first surface 201a of the substrate 201, a portion is located on the first side surface 201c of the substrate 201, and a portion is located on the second surface 201b of the substrate 201.

[0084] The first flexible circuit board 204 is located on the second surface 201b of the substrate 201 away from the plurality of electronic components 202 (the first surface 201a and the second surface 201b of the substrate 201 are two sides arranged opposite to each other). The first bonding structure 205 is located between the substrate 201 and the first flexible circuit board 204, and the first flexible circuit board 204 is fixedly arranged on the second surface 201b of the substrate 201 through the first bonding structure 205. The first flexible circuit board 204 is connected to the other end of the first connecting wire 203, and the first flexible circuit board 204 is also connected to the first external circuit structure 300. The first flexible circuit board 204 is used to transmit the first driving signal provided by the first external circuit structure 300 to the electronic component 202 through the first connecting wire 203.

[0085] That is, in the embodiment of the present application, by setting the first flexible circuit board 204 on the second surface 201b of the substrate 201, and connecting with the external circuit structure through the lines in the first flexible circuit board 204, it is possible to prepare the wiring only on the first surface 201a of the substrate 201, thereby avoiding the problem that the surface on which the wiring is prepared first is easily scratched during the process of preparing the surface for the wiring later, and the product yield can be ensured.

[0086] Further, in the embodiment of the present application, the first conductive structure 2041 of the first flexible circuit board 204 may include a plurality of first signal lines, a portion of the plurality of first signal lines is connected to the second conductive structure 2042, and another portion of the first signal lines is connected to the third conductive structure 2043. An insulating layer a3 is provided between the second conductive structure 2042 and the third conductive structure 2043 to insulate the second conductive structure 2042 from the third conductive structure 2043.

[0087] One end of the first signal line can be connected to the other end of the first connection line 203, and the other end of the first signal line is connected to the second conductive structure 2042 or the third conductive structure 2043. In addition, the length occupied by the second conductive structure 2042 and the third conductive structure 2043 in the second direction Y is less than the length occupied by the plurality of first signal lines in the second direction Y.

[0088] Figure 5 It is a top view of the first flexible circuit board provided in an embodiment of the present application. Figure 6 yes Figure 5 Cross-section along the MM direction. Figure 5 and Figure 6 It can be seen that the first flexible circuit board 204 has a first area 204a and a second area 204b. The first flexible circuit board 204 includes a first conductive structure 2041 located in the first area 204a, and a second conductive structure 2042 and a third conductive structure 2043 located in the second area 204b and stacked. That is, the first area 204a is a single-layer conductive structure, and the second area 204b is a double-layer conductive structure. Figure 6 It is only used to illustrate the positional relationship among the first conductive structure 2041 , the second conductive structure 2042 and the third conductive structure 2043 , and does not represent the actual appearance of each conductive structure.

[0089] Generally, during the preparation of the functional backplane, reference Figure 7 After the first flexible circuit board 204 is bonded with the first bonding structure 205, it needs to be subjected to multiple high temperature treatments at 150°C (degrees Celsius) and once at 270°C. Figure 8 After the functional backplane 200 is subjected to high temperature treatment, the warping amount of the target area of ​​the substrate 201 (the target area is the projection area of ​​the second area 204b of the first flexible circuit board 204 on the substrate 201) reaches 170 μm (micrometers) to 200 μm.

[0090] Optionally, after the first flexible circuit board 204 is bonded with the first bonding structure 205, it can be subjected to high temperature treatment at 150°C three times and 270°C once. After the first bonding structure 205 bonds the first flexible circuit board 204, the first bonding structure 205 needs to be cured at a temperature of 150°C; after the first connecting wire 203 is formed, the material forming the first connecting wire 203 needs to be cured at a temperature of 150°C; after the protective layer for protecting the first connecting wire 203 is formed, the protective layer needs to be cured at a temperature of 150°C; and the fixed connection between the light emitting diode LED and the substrate needs to be achieved through a die bonding process at a temperature of 270°C.

[0091] The first flexible circuit board 204 mainly includes a polyimide (PI) layer, a polyethylene terephthalate (PET) layer and a conductive structure, wherein the material of the conductive structure can generally be copper foil. In some embodiments, the overall thermal expansion coefficient CTE of the first flexible circuit board 204 is 18ppm / ℃ to 22ppm / ℃. PPM refers to Parts Per Million, and ppm / ℃ can be used to indicate the expansion and contraction changes in volume, such as the volume expansion of a few parts per million for every 1℃ increase in temperature. For example, 18ppm / ℃ means that the volume expands by 18 parts per million for every 1℃ increase in temperature.

[0092] The CTE of PI material is 20ppm / ℃ to 30ppm / ℃, the CTE of PET material is 60ppm / ℃ to 80ppm / ℃, and the CTE of copper foil is 17.8ppm / ℃. Generally, the CTE of the bonding material of the first bonding structure 205 is 42ppm / ℃ to 134ppm / ℃. In a high-temperature process, the higher the temperature, the greater the expansion of the bonding material. When the difference between the expansion of the bonding material and the first flexible circuit board 204 is too large, the substrate 201 will be warped.

[0093] According to the structure of the first flexible circuit board 204, the first flexible circuit board 204 has a first region 204a of a single-layer conductive structure and a second region 204b of a double-layer conductive structure. In the case of using the same bonding material and the same thickness and plane area of ​​the bonding material in a unit space, the higher the percentage of copper content in a unit space (such as the higher percentage of copper content per unit area or per unit volume), the greater the difference in expansion amount from the bonding material during high temperature treatment, and the more serious the warping of the substrate 201.

[0094] Specifically, the force of copper expansion can pull and deform the first flexible circuit board 204 (for example, the size along the expansion direction becomes larger), while the force of the bonding material expansion can pull and deform the first bonding structure 205. However, at the same temperature, there is a difference between the magnitude of the force when copper expands and the magnitude of the force when the bonding material expands. For a certain unit space, at a certain temperature, the magnitude of the force when copper expands is positively correlated with the proportion of copper content of the first flexible circuit board 204 in the space. That is, if the first flexible circuit board 204 has a higher proportion of copper content in the space, the greater the force required for copper expansion per unit size, the smaller the thermal expansion coefficient, that is, the smaller the pulling deformation; if the first flexible circuit board 204 has a lower proportion of copper content in the space, the smaller the force required for copper expansion per unit size, the larger the thermal expansion coefficient, that is, the larger the pulling deformation.

[0095] In the embodiment of the present application, the thermal expansion coefficient of the bonding material is slightly different from the thermal expansion coefficient of the first region 204a of the single-layer conductive structure, but is significantly different from the thermal expansion coefficient of the second region 204b of the double-layer conductive structure. Therefore, if the thermal expansion coefficient of the bonding material remains unchanged in any unit space (i.e., the magnitude of the force when the bonding material expands remains unchanged), the pulling deformation amount of the second region 204b of the first flexible circuit board 204 and the pulling deformation amount of the first bonding structure 205 will differ significantly, and the pulling deformation amount of the first region 204a of the first flexible circuit board 204 and the pulling deformation amount of the first bonding structure 205 will differ slightly. Furthermore, the second region 204b of the double-layer conductive structure is more likely to warp than the first region 204a of the single-layer conductive structure, which in turn causes the portion of the functional backplane located in the second region 204b to be more likely to warp.

[0096] It should be noted that the expansion of an object is positively correlated with the thermal expansion coefficient of the material of the object. That is, at the same temperature, the greater the thermal expansion coefficient of the material of the object, the greater its deformation; the smaller the thermal expansion coefficient of the material of the object, the smaller its deformation.

[0097] Since the thermal expansion coefficient of the first flexible circuit board 204 is smaller than that of the bonding material of the first bonding structure 205, in order to reduce the possibility of warping of the functional backplane, the thermal expansion coefficients of the two can be made as close as possible or the expansion amount of the first bonding structure 205 can be reduced.

[0098] In the embodiments of the present application, Fig. 9 1 is a top view of a first bonding structure and a first flexible circuit board provided in an embodiment of the present application. Fig. 9The first bonding structure 205 has a plurality of strip-shaped target portions 205a at least located in the second region 204b. The thickness of the target portion 205a of the first bonding structure 205 is smaller than the thickness of other portions of the first bonding structure 205 except the target portion 205a.

[0099] In the subsequent high-temperature process of forming the functional backplane, since the thickness of the target portion 205a is relatively small, expansion space can be provided for the expansion of the bonding material of the first bonding structure 205. The expansion space can accommodate a portion of the expansion of the first bonding structure 205, thereby reducing the total expansion of the first bonding structure 205, avoiding excessive expansion of the first bonding structure 205 that results in a large difference in expansion with the second area 204b of the first flexible circuit board 204, thereby avoiding the possibility of warping of the functional backplane and improving the yield of the functional backplane.

[0100] In summary, the embodiment of the present application provides a functional backplane, in which the first flexible circuit board is fixedly arranged on the second surface of the substrate through the first bonding structure. The first flexible circuit board has a first area of ​​a single-layer conductive structure and a second area of ​​a double-layer conductive structure. Since the proportion of conductive material in a unit space of the double-layer conductive structure is higher than that of the single-layer conductive structure, the expansion amount of the second area of ​​the double-layer conductive structure during high temperature is greater than the expansion amount of the first area of ​​the single-layer conductive structure, and the expansion amount of the first bonding structure is more different. The present application designs the thickness of the target part located in the second area of ​​the first bonding structure to be smaller, which can provide expansion space for the expansion of the bonding material of the first bonding structure, thereby reducing the total expansion amount of the first bonding structure. In this way, it is possible to avoid the expansion amount of the first bonding structure being too large, resulting in a large difference in the expansion amount of the second area of ​​the first flexible circuit board, thereby avoiding the possibility of warping of the functional backplane and improving the yield of the functional backplane.

[0101] refer to Fig. 9 The plurality of target portions 205a include a plurality of first grooves C1 extending along a first direction X and spaced apart along a second direction Y. The first direction X is the arrangement direction of the first regions 204a and the second regions 204b, and the second direction Y is perpendicular to the arrangement directions of the first and second directions X and Y.

[0102] Generally, the functional back panel 10 is more likely to be warped in the second direction Y. Therefore, by designing a plurality of first grooves C1 extending along the first direction X and arranged along the second direction Y, it is possible to provide expansion space for the first fitting structure 205 in the second direction Y to a large extent, thereby reducing the total expansion amount of the first fitting structure 205 in the second direction Y. In this way, the possibility of the functional back panel being warped in the second direction Y can be reduced.

[0103] As an optional implementation, Fig.10 is a top view of another first bonding structure and a first flexible circuit board provided in an embodiment of the present application. Fig.10 The plurality of target portions 205a further include a plurality of second grooves C2 extending along the second direction Y and spaced apart in the second direction Y. At least some of the second grooves C2 among the plurality of second grooves C2 are in communication with the first groove C1.

[0104] By providing a plurality of second grooves C2, expansion space can be further provided for the expansion of the first bonding structure 205, thereby reducing the total expansion amount of the first bonding structure 205. This can further reduce the possibility of warping of the functional backplane 10.

[0105] Optionally, the plurality of second grooves C2 may be located in the middle of the second region 204b in the first direction X to avoid affecting the bonding effect of a portion of the first bonding structure 205 located at the plurality of second grooves C2 away from the first region 204a due to its shorter length in the first direction X.

[0106] As another optional implementation, Fig.11 2 is a top view of another first bonding structure and a first flexible circuit board provided in an embodiment of the present application. Fig.11 The plurality of target portions 205a further include a third groove C3 extending along the second direction Y. The length of the third groove C3 in the second direction Y is equal to the length of the first bonding structure 205 in the second direction Y. The third groove C3 is located at the boundary between the first region 204a and the second region 204b.

[0107] By providing the third groove C3, an expansion space can be further provided for the expansion of the first bonding structure 205, thereby reducing the total expansion amount of the first bonding structure 205. This can further reduce the possibility of warping of the functional backplane.

[0108] Optionally, since the third groove C3 is located at the boundary between the first area 204a and the second area 204b, the length of the portion of the first bonding structure 205 located at the plurality of second grooves C2 away from the first area 204a in the first direction X can be larger (equal to the length of the second area 204b in the first direction X), thereby ensuring the bonding effect of the first bonding structure 205.

[0109] In the examples of this application, refer to Fig.12 and Fig.13The functional backplane 10 further includes a plurality of first connection pads 206 located on the first surface 201a of the substrate 201, and a plurality of second connection pads 207 located on the second surface 201b of the substrate 201 and corresponding to the plurality of first connection pads 206. In addition, the functional backplane 10 further includes a plurality of first connection traces 203 corresponding to the plurality of first connection pads 206 and the plurality of second connection pads 207. One end of each first connection trace 203 is connected to the electronic component 202 through a corresponding first connection pad 206, and the other end is connected to the first flexible circuit board 204 through a corresponding second connection pad 207.

[0110] Optionally, a plurality of first connection pads 206 are arranged at intervals in the second direction Y, and a plurality of second connection pads 207 are arranged at intervals in the second direction Y, thereby avoiding short circuits between different electrodes.

[0111] In order to ensure that each second connection pad 207 can be connected to the first flexible circuit board 204, it is necessary to make the length of the first flexible circuit board 204 in the second direction Y greater than or equal to the length occupied by the plurality of second connection pads 207 in the second direction Y. Of course, the length of the first flexible circuit board 204 in the second direction Y needs to be less than the length of the substrate 201 in the second direction Y.

[0112] Optional, reference Figure 5 The minimum value Amin of the length A of the first flexible circuit board 204 in the second direction Y is equal to the length occupied by the plurality of second connection pads 207 in the second direction Y. The maximum value Amax of A is equal to the length of the substrate 201 in the second direction Y minus 30 μm (micrometers).

[0113] In addition, since the first signal line in the first flexible circuit board 204 needs to be designed for line collection, the length B of the first flexible circuit board 204 in the first direction X may be in the range of 20 μm to 50 μm.

[0114] In the embodiment of the present application, according to the signal transmission resistance and reliability design requirements of the first flexible circuit board 204, the length C of the first region 204a in the first direction X must be greater than or equal to 1 / 3 of the length B of the first flexible circuit board 204 in the first direction X, and must be less than or equal to the length B of the first flexible circuit board 204 in the first direction X minus 10 mm (millimeter). That is, the minimum value Cmin of the length C of the first region 204a in the first direction X is (1 / 3×B) mm, and the maximum value Cmax is (B-10) mm.

[0115] Accordingly, the length D of the second area 204b in the first direction X needs to be greater than or equal to 10mm, and needs to be less than or equal to 2 / 3 of the length B of the first flexible circuit board 204 in the first direction X. That is, the minimum value Dmin of the length D of the second area 204b in the first direction X is 10mm, and the maximum value Dmax is (2 / 3×B) mm. The reason why the length D of the second area 204b in the first direction X needs to be greater than or equal to 10mm is that if the length D is less than 10mm, the signal transmission resistance will be too large, which will cause the temperature to be too high. Too high a temperature will be detrimental to the reliability and the reliability will be low.

[0116] In the embodiment of the present application, under the premise of ensuring that the first flexible circuit board 204 is not affected when transmitting signals, the length D of the second area 204b of the double-layer conductive structure in the first direction X is reduced as much as possible, which can reduce the design amount of the double-layer conductive structure, thereby reducing the area of ​​the region where warping occurs, and minimizing the possibility of warping. That is, the length D of the second area 204b in the first direction X can be a minimum value of 10mm, and the length D of the first area 204a in the first direction X can be a maximum value of (B-10)mm.

[0117] Optionally, in order to ensure that the first bonding structure 205 realizes effective bonding between the substrate 201 and the first flexible circuit board 204, the spacing E between two adjacent first grooves C1 along the second direction Y cannot be too small, otherwise the portion of the first bonding structure 205 located between the two first grooves C1 will be isolated from other portions, thereby affecting the bonding effect here. Fig. 9 , the distance E between two adjacent first grooves C1 along the second direction Y may be greater than or equal to 10 mm.

[0118] In addition, the first grooves C1 are evenly arranged within the length range of the first fitting structure 205 in the second direction Y. For example, the distance between any two adjacent first grooves C1 along the second direction Y is the same.

[0119] Optional, reference Fig. 9, the length F of the first groove C1 in the second direction Y (i.e., the width of the first groove C1) can be designed according to the expansion of the bonding adhesive and the required size for stress release. For example, the expansion of the bonding material of the first bonding structure 205 at high temperature can be calculated based on its thermal expansion coefficient. When the high temperature reaches up to 270°C, the expansion of the first bonding structure 205 can reach 0.7mm, and considering that a certain space is required for stress release, the minimum value Fmin of the width F of the first groove C1 needs to be greater than 0.7mm, for example, it can be 1mm. As for the maximum value Fmax of the width F of the first groove C1, considering that the width of the first groove C1 is too wide, it will affect the bonding effect and cause the surface to be uneven after bonding, so the maximum value Fmax of the width F of the first groove C1 is set to 5mm. That is, the range of the width F of the first groove C1 satisfies: 1mm≤F≤5mm.

[0120] Optional, reference Fig.10 , the length G of the second groove C2 in the first direction X (i.e., the width of the second groove C2) and the length G of the third groove C3 in the first direction X (i.e., the width of the third groove C3) can also be designed according to the expansion amount of the bonding adhesive and the required size for stress release. Since the width of the groove extending along the second direction Y must not only take into account the expansion, but also the bonding effect of the part of the groove away from the first area 204a, the minimum value Gmin of the width of the groove extending along the second direction Y can be designed to be less than 0.7mm, for example, 0.5mm. Although a width of 0.5mm may be difficult to allow for the expansion amount of the bonding adhesive, the functional backplane is not prone to warping in the second direction Y, and a width of 0.5mm also has a certain expansion space, so it has little effect on the accommodation of the expansion. As for the maximum value Gmax of the width G, considering that the width of the groove is too wide, it will affect the bonding effect and cause the surface to be uneven after bonding, the maximum value Gmax of the width G of the groove is set to 2mm. That is, the width G of the second groove C2 and the width G of the third groove C3 satisfy the following range: 1 mm ≤ G ≤ 2 mm.

[0121] For the design of the length H (the length of the second groove C2) of the second groove C2 in the second direction Y, since the length of the second region 204b in the first direction X is compressed to 10 mm, in order to avoid the length I of the part of the first fitting structure 205 located away from the first region 204a in the second groove C2 in the first direction X being too small, resulting in too small a fitting area at the bottom and thus a deteriorated fitting effect, it is necessary to design the length H of the second groove C2 to be less than the spacing E between two adjacent first grooves C1 in the second direction Y, that is, H < E. Through this design, it can be ensured that there are connected parts on both sides of the first fitting structure 205 in the second groove C2, and it will not cause the part of the first fitting structure 205 located away from the first region 204a in the second groove C2 to be an island fitting.

[0122] Optionally, referring to Fig.10 , the distance I between the boundary of the second groove C2 away from the first region 204a and the boundary of the first fitting structure 205 away from the first region 204a can range from 4 mm ≤ I ≤ 4.75 mm. The maximum value Imax of I = 4.75 mm is calculated based on the condition that the midlines of the second groove C2 and the second region 204b are collinear, and the width D of the second region 204b in the first direction X = 10 mm, and the width G of the second groove C2 = 0.5 mm (the calculation method is 10 / 2 - 0.5 / 2 = 4.75 mm).

[0123] Furthermore, referring to Fig.10 , the spacing J between two adjacent second grooves C2 in the second direction Y is greater than or equal to 10 mm, thereby ensuring the continuity of the first fitting structure 205 and ensuring the fitting effect. Within the length range of the first fitting structure 205 in the second direction Y, the second grooves C2 are evenly arranged. For example, the distance between any two adjacent second grooves C2 along the second direction Y is the same.

[0124] In addition, in order to ensure the fitting effect of the first fitting structure 205, the length of the first fitting structure 205 along the first direction X is equal to the length of the first flexible circuit board 204 along the first direction X. That is, referring to Fig.11 , the length K of the third groove C3 in the second direction Y can be equal to the length A of the first flexible circuit board 204 in the second direction Y, that is, K = A.

[0125] In the embodiment of the present application, as Fig. 9 , designing the first groove C1 extending in the first direction X can increase the expansion amount of the fitting material of the first fitting structure 205 under high-temperature processes, effectively solving the problem that the difference in the thermal expansion coefficients between the first flexible circuit board 204 and the fitting material of the first fitting structure 205 is large, resulting in the first flexible circuit board 204 pulling the substrate 201 and causing the functional backplane to warp in the second direction Y.

[0126] Fig.10 Design scheme Fig. 9 The second groove C2 extending along the second direction Y is added, which can increase the expansion amount of the bonding material of the first bonding structure 205 in the length direction (first direction X) of the first flexible circuit board 204 and also increase the expansion amount of the first flexible circuit board 204 in the width direction (second direction Y). Fig.11 The design solution places the groove extending along the second direction Y at the junction of the first area 204a and the second area 204b, and its length K is the same as the length A of the first flexible circuit board 204, that is, the third groove C3 runs through the entire first bonding structure 205. In this way, the bonding material of the first area 204a can be isolated from the bonding material of the second area 204b, avoiding the joint effect of expansion and contraction of the two areas and stress release under high temperature. Figures 9 and 10 In order to illustrate the positional relationship between the first flexible circuit board 204 and the first bonding structure 205 , the first bonding structure 205 is drawn on the first flexible circuit board 204 .

[0127] As another optional implementation, refer to Fig.14 and Fig.15 The plurality of target portions 205a include a plurality of fourth grooves C4 extending along the first direction X and spaced apart in the second direction Y, and a plurality of fifth grooves C5 extending along the second direction Y and spaced apart in the first direction X. The plurality of fourth grooves C4 and the plurality of fifth grooves C5 form a grid shape. Fig.14 Lines are used to illustrate the fourth groove C4 and the fifth groove C5.

[0128] During the preparation of the first bonding structure 205, an uncured bonding material is first formed, and then a grid-shaped release film is attached to one side of the bonding material, and finally the release film is pressed by pressure to obtain the grid-shaped first bonding structure 205. The fourth groove C4 and the fifth groove C5 in the first bonding structure 205 are both obtained by pressing the release film. The horizontal and vertical intersecting grooves can provide expansion space for the first bonding structure 205.

[0129] In the examples of this application, refer to Fig.16 The part of the release film located in the first area 204a can be a smooth plane, and the part located in the second area 204b can be a textured surface. Then, the first area 204a of the first bonding structure 205 can be a flat bonding part, and the second area 204b can form a plurality of fourth grooves C4 and a plurality of fifth grooves C5 to provide expansion space for high temperature expansion. Or, refer to Fig.17 The portion of the release film located in the first region 204a may also be a textured film, that is, Fig.18, the plurality of fourth grooves C4 and the plurality of fifth grooves C5 may also be located in the first region 204a. This method can not only provide expansion space for the expansion of the bonding material in the second region 204b, but also provide expansion space for the expansion of the bonding material in the first region 204a.

[0130] Optional, reference Fig.19 The release film may have a plurality of first protrusions in a strip shape and a plurality of second protrusions in a strip shape. The plurality of first protrusions and the plurality of second protrusions are vertically arranged. The plurality of first protrusions may be used to form a plurality of fourth grooves C4, and the plurality of second protrusions may be used to form a plurality of fifth grooves C5.

[0131] The width of the first protrusion affects the width of the fourth groove C4, the width of the second protrusion affects the width of the fifth groove C5, and the spacing between adjacent first protrusions affects the spacing between adjacent fourth grooves C4, and the spacing between adjacent second protrusions affects the spacing between adjacent fifth grooves C5.

[0132] For example, the width P of the first protrusion and the second protrusion ranges from 100 μm to 150 μm, and the width of the fourth groove C4 and the fifth groove C5 ranges from 100 μm to 150 μm. The spacing Q between adjacent first protrusions and the spacing Q between adjacent second protrusions are both greater than or equal to 100 μm, and the spacing between two fourth grooves C4 in the second direction Y and the spacing between two adjacent fifth grooves C5 in the first direction X are both greater than or equal to 300 μm.

[0133] In addition, in order to form the fourth groove C4 and the fifth groove C5 by the first protrusion and the second protrusion through the release film pressing, the height T of the first protrusion and the second protrusion can be greater than or equal to 1 / 2 of the thickness of the first bonding structure 205, and less than or equal to the thickness of the first bonding structure 205. For example, assuming that the thickness of the first bonding structure 205 is 20 μm, the height N of the first protrusion and the second protrusion satisfies: 10 μm≤N≤20 μm.

[0134] In the embodiment of the present application, the first bonding structure 205 includes a bonding material, and the other parts of the first bonding structure 205 except the target part 205a are the parts of the first bonding structure 205 having the bonding material, and the target part 205a of the first bonding structure 205 is the part of the first bonding structure 205 not having the bonding material. That is, in the above-mentioned embodiments, the first groove C1, the second groove C2, the third groove C3, the fourth groove C4 and the fifth groove C5 can be through grooves.

[0135] In the examples of this application, refer to Fig.12 and Fig.13The functional backplane 10 further includes: a second connecting wire 208, a second flexible circuit board 209 and a second bonding structure (not shown in the figure).

[0136] Among them, one end of the second connecting line 208 is located on the first surface 201a of the substrate 201 and is connected to the electronic component 202. The other end of the second connecting line 208 is bent from the second surface 201d of the substrate 201 and is located on the second surface 201b of the substrate 201. The second surface 201d and the first side surface 201c are opposite to each other.

[0137] The second flexible circuit board 209 is located on the second surface 201b of the substrate 201 away from the electronic component 202, and the second flexible circuit board 209 and the first flexible circuit board 204 are spaced apart in the first direction X. The second bonding structure is located between the substrate 201 and the second flexible circuit board 209, and the second flexible circuit board 209 is fixedly arranged on the second surface 201b of the substrate 201 through the second bonding structure. In addition, the second flexible circuit board 209 is connected to the other end of the second connecting wire 208, and the second flexible circuit board 209 is also connected to the second external circuit structure. The second flexible circuit board 209 is used to transmit the second driving signal provided by the second external circuit structure to the electronic component 202 through the second connecting wire 208.

[0138] Optionally, the second flexible circuit board 209 includes a fourth conductive structure, that is, the second flexible circuit board 209 is not divided into a single-layer conductive structure area and a double-layer conductive structure area, and all areas of the second flexible circuit board 209 are designed with a single-layer conductive structure. Therefore, there is no need to design a special structure for the second bonding structure, and the thickness of each area of ​​the second bonding structure is the same. In other words, the second bonding structure does not need to design the target portion 205a.

[0139] Of course, in order to prevent the substrate 201 from warping in the area where the second flexible circuit board 209 is located, the second bonding structure can also be designed with reference to the first bonding structure 205, that is, by designing the groove to provide expansion space for the expansion of the bonding material. The embodiment of the present application does not limit the specific implementation of the second bonding structure.

[0140] Further, the functional backplane 10 also includes a plurality of third connection pads 210 located on the first surface 201a of the substrate 201, and a plurality of fourth connection pads 211 located on the second surface 201b of the substrate 201 and corresponding one-to-one with the plurality of third connection pads 210. In addition, the functional backplane 10 also includes a plurality of second connection traces 208 corresponding to the plurality of third connection pads 210 and the plurality of fourth connection pads 211. One end of each second connection trace 208 is connected to the electronic component 202 through a corresponding third connection pad 210, and the other end is connected to the second flexible circuit board 209 through a corresponding fourth connection pad 211.

[0141] Optionally, a plurality of third connection pads 210 are arranged at intervals in the second direction Y, and a plurality of fourth connection pads 211 are arranged at intervals in the second direction Y, thereby avoiding short circuits between different electrodes.

[0142] In the embodiment of the present application, the first flexible circuit board 204 and the second flexible circuit board 209 both include a main body structure and a branch structure. For each of the first flexible circuit board 204 and the second flexible circuit board 208, since the end of the branch structure of the flexible circuit board away from the side needs to be connected to the external circuit structure, the bonding structure cannot be set in the area where the branch structure of the flexible circuit board is located. For example, for the first flexible circuit board 204, the orthographic projection of the first bonding structure 205 on the first flexible circuit board 204 can be located in the area where the main body structure of the first flexible circuit board 204 is located, and not in the area where the branch structure of the first flexible circuit board 204 is located.

[0143] Furthermore, in the embodiment of the present application, the first flexible circuit board 204 has a first area 204a and a second area 204b, which may mean that both the main structure and the branch structure of the first flexible circuit board 204 have a first area and a second area. That is, both the main structure and the branch structure of the first flexible circuit board 204 have an area of ​​a single-layer conductive structure and an area of ​​a double-layer conductive structure.

[0144] like Fig.12 In the embodiment, the first flexible circuit board 204 includes a first branch structure Z1 and a second branch structure Z2, and the second flexible circuit board 209 includes a third branch structure Z3. The ends of the first branch structure Z1 and the second branch structure Z2 away from the first side surface 201c can be used to connect to the first external circuit structure, and the end of the third branch structure Z3 away from the second side surface 201d can be used to connect to the second external circuit structure.

[0145] refer to Fig. 20 and Fig. 22 The first flexible circuit board 204 includes a first conductive layer a1, an insulating layer a3, and a second conductive layer a2 which are stacked in sequence. The first flexible circuit board 204 has a first region 204a and a second region 204b, a first conductive structure 2041 is located in the first region 204a, and a second conductive structure 2042 and a third conductive structure 2043 are located in the second region 204b. Specifically, the first conductive structure 2041 can be located in either the first conductive layer a1 or the second conductive layer a2, the second conductive structure 2042 is located in one of the first conductive layer a1 and the second conductive layer a2, and the third conductive structure 2043 is located in the other of the first conductive layer a1 and the second conductive layer a2.

[0146] The first conductive structure 2041 may include a plurality of first signal lines 20411, one end of each first signal line 20411 is connected to the other end of the first connecting line; a portion of the plurality of first signal lines 20411 is connected to the second conductive structure 2042, and another portion of the first signal lines 20411 is connected to the third conductive structure 2043. At least one first signal line 20411 may be disposed in the same layer as the second conductive structure 2042, and a portion of the plurality of first signal lines 20411 may be directly connected to the second conductive structure 2042; at least one first signal line 20411 is connected to the third conductive structure 2043 through a via in the insulating layer a3. Alternatively, at least one first signal line 20411 may be disposed in the same layer as the third conductive structure 2043, and at least one first signal line 20411 may be directly connected to the third conductive structure 2043, and at least one first signal line 20411 is connected to the second conductive structure 2042 through a via in the insulating layer a3.

[0147] In the embodiment of the present application, the second conductive structure 2042 of the first flexible circuit board 204 is located in the first conductive layer a1, the third conductive structure 2043 is located in the second conductive layer a2, and there is an insulating layer a3 between the first conductive layer a1 and the second conductive layer a2. Among them, the second conductive structure 2042 specifically includes a first signal part a11, a second signal part a12 and a third signal part a13; the third conductive structure 2043 specifically includes a fourth signal part a21 and a fifth signal part a22. Among them, the first signal part a11, the third signal part a13 and the fourth signal part a21 are all used to transmit a third constant voltage signal, and the third constant voltage signal can be a ground signal. The second signal part a12 is used to transmit a first constant voltage signal, and the fifth signal part a22 can be used to transmit a second constant voltage signal. The first constant voltage signal and the second constant voltage signal can both be high-level signals.

[0148] Optionally, each of the first signal portion a11, the second signal portion a12, the third signal portion a13, the fourth signal portion a21 and the fifth signal portion a22 is a sheet-like structure, and different signal portions are spaced apart from each other.

[0149] In the examples of this application, refer to Fig.23 , taking the case where the plurality of first signal lines 20411 are located in the first conductive layer a1 as an example. The plurality of first signal lines 20411 include a first sub-signal line L1, a second sub-signal line L2, and a third sub-signal line L3. Among them, the first sub-signal line L1 can be directly connected to the second signal portion a12 of the first conductive layer a1. The second sub-signal line L2 is connected to the fifth signal portion a22 of the second conductive layer a2 through a via in the insulating layer a3. The third sub-signal line L3 is connected to the fourth signal portion a21 of the second conductive layer a2 through a via in the insulating layer a3.

[0150] refer to Fig. 20 The first conductive layer a1 includes two first signal parts a11, two second signal parts a12 and two third signal parts a13. Each first signal part a11 and each third signal part a13 are used to transmit a third constant voltage signal. Fig. 20 There is a gap between the third signal portion a13 and the first signal portion a11 of the second branch structure Z2. The gap can be used to set a test line, and the test line is located in the first conductive layer a1.

[0151] Combination Fig.21 The second conductive layer a2 includes a fourth signal portion a21 and two fifth signal portions a22. The fifth signal portion a22 is in a T-shaped structure, and the fourth signal portion a21 surrounds the fifth signal portion a22 to form an integral structure.

[0152] In the examples of this application, refer to Fig.24 The second signal portion a12 has a first sub-portion a121 located between the first signal portion a11 and the third signal portion a13, a second sub-portion a122 located near the first region 204a of the first signal portion a11, and a third sub-portion a123 located near the first region 204a of the third signal portion a13.

[0153] The third sub-signal line L3 located in the first conductive layer a1 is connected to the fourth signal part a21 located in the second conductive layer a2, and the first signal part a11, the third signal part a13 and the fourth signal part a21 are all used to transmit the third constant voltage signal. Among them, the third sub-signal line L3 is connected to the fourth signal part a21 of the second conductive layer a2 through a via hole in the insulating layer a3, thereby realizing that the fourth signal part a21 transmits the third constant voltage signal. In addition, since the first signal part a11 and the third signal part a13 located in the first conductive layer a1 both have a facing area with the fourth signal part a21 located in the second conductive layer a2, a via hole can be set at a specific position of the insulating layer a3 between the first conductive layer a1 and the second conductive layer a2, so that the first signal part a11 and the third signal part a13 are connected to the fourth signal part a21 through the via hole, thereby realizing that the first signal part a11 and the third signal part a13 transmit the third constant voltage signal.

[0154] Fig.25 yes Fig.21 A partial enlarged schematic diagram of the dotted box area. Fig.25In order to realize the connection between the first flexible circuit board 204 and the first external circuit structure 300, the first region 204a of the first flexible circuit board 204 also includes an end region located in the first branch structure Z1 and the second branch structure Z2 away from the first side surface 201c, and the end region has a plurality of first strip electrodes R extending along the first direction X and arranged at equal intervals along the second direction Y. The first external circuit structure 300 is connected to the first flexible circuit board 204 through the plurality of first strip electrodes R. The plurality of first strip electrodes R are all located in the second conductive layer a2.

[0155] The first type of strip electrodes R1 and the fourth signal part a21 among the multiple first strip electrodes R are both located in the second conductive layer a2, so the two can be directly connected to form an integrated structure. The multiple second type of strip electrodes R2 and the fifth signal part a22 are both located in the second conductive layer a2, so the two can also be directly connected to form an integrated structure.

[0156] However, the third type of strip electrode R3 among the plurality of first strip electrodes R is connected to the second signal portion a12. Since the second signal portion a12 for transmitting the first constant voltage signal is located in the first conductive layer a1, the two need to be connected through the via V in the insulating layer a3.

[0157] It should be noted that, in order to achieve the connection between the plurality of first signal lines 20411 and the other end of the first connection line, the surface of the end of the first signal line 20411 close to the first side surface 201c needs to be exposed, and the exposed portion can constitute the second connection pad 207. The first connection line 203 is directly in contact with the second connection pad 207 to achieve connection.

[0158] refer to Fig.26 , the fourth conductive structure 2091 in the second flexible circuit board 209 may include a plurality of second signal lines 20911. One end of each second signal line 20911 is connected to the other end of the second connection line 208, and the other end is connected to the second external circuit structure. Thus, the second external circuit structure can transmit signals to the plurality of second signal lines 20911.

[0159] The second flexible circuit board 209 includes only one conductive layer, which includes a plurality of second signal lines 20911. In order to achieve the connection between the plurality of second signal lines 20911 and the second connection trace 208, it is necessary to expose the surface of the end of the second signal line close to the second side 201d, and the exposed portion can constitute the fourth connection pad 211. The first connection trace 203 is directly in contact with the fourth connection pad 211 to achieve connection. In addition, the second flexible circuit board 209 also includes a plurality of second strip electrodes located at the end of the third branch structure Z3 away from the second side 201d, extending along the first direction X and arranged at equal intervals along the second direction Y. The second external circuit structure is connected to the second flexible circuit board 209 through the plurality of second strip electrodes.

[0160] In summary, the embodiment of the present application provides a functional backplane, in which the first flexible circuit board is fixedly arranged on the second surface of the substrate in the display panel through the first bonding structure. The first flexible circuit board has a first area of ​​a single-layer conductive structure and a second area of ​​a double-layer conductive structure. Compared with the single-layer conductive structure, the double-layer conductive structure has a higher proportion of conductive material per unit space. Therefore, during the high temperature process, the expansion amount of the second area of ​​the double-layer conductive structure is greater than the expansion amount of the first area of ​​the single-layer conductive structure, and the expansion amount of the first bonding structure is more different. The present application designs the thickness of the target part located in the second area of ​​the first bonding structure to be smaller, which can provide expansion space for the expansion of the bonding material of the first bonding structure, thereby reducing the total expansion amount of the first bonding structure. In this way, it is possible to avoid the expansion amount of the first bonding structure being too large, resulting in a large difference in the expansion amount of the second area of ​​the first flexible circuit board, thereby avoiding the possibility of warping of the functional backplane and improving the yield of the functional backplane.

[0161] In the second solution, the embodiment of the present application further provides a functional backplane, in which the design of the substrate 201, the electronic component 202, the first connecting trace 203 and the first flexible circuit board 204 in the functional backplane 10 is the same as that of the first solution described above. The difference lies in the design of the first bonding structure 205.

[0162] In the examples of this application, refer to Fig. 27 The first bonding structure 205 includes a first portion 2051 located in the first region 204a and a second portion 2052 located in the second region 204b. The difference between the thermal expansion coefficient CTE of the material of the second portion 2052 and the thermal expansion coefficient CTE of the material of the first conductive structure 2041 (or the second conductive structure 2042) in the first flexible circuit board 204 is less than 3 ppm / °C.

[0163] That is, in the embodiment of the present application, in the second area 204b of the double-layer conductive structure, the second part 2052 of the first bonding structure 205 can use a high-viscosity (viscosity ≥ 1000gf) pressure-sensitive adhesive with a smaller thermal expansion coefficient, thereby reducing the difference in the thermal expansion coefficient between the second area 204b of the first flexible circuit board 204 and the thermal expansion coefficient of the second part 2052 of the first bonding structure 205, thereby avoiding the warping of the substrate 201 caused by excessive difference in expansion at high temperature.

[0164] Optionally, the material of the first conductive structure 2041 and the second conductive structure 2042 is copper, and the thermal expansion coefficient of copper is 17.8 ppm / °C. The thermal expansion coefficient CTE of the material of the second portion 2052 is less than or equal to 20 ppm / °C. Thus, the difference between the thermal expansion coefficient CTE of the material of the second portion 2052 and the thermal expansion coefficient CTE of the material of the first conductive structure 2041 (or the second conductive structure 2042) in the first flexible circuit board 204 can be less than 3 ppm / °C.

[0165] The embodiment of the present application does not specifically limit the material of the second portion 2052 of the first bonding structure 205 , and only needs to satisfy the requirements that the coefficient of thermal expansion CTE is less than or equal to 20 ppm / ° C. and the adhesive force is greater than or equal to 1000 gf.

[0166] The material of the second portion 2052 is different from the material of the first portion 2051, and the thermal expansion coefficient of the material of the second portion 2052 is smaller than the thermal expansion coefficient of the material of the first portion 2051. In this case, since the proportion of copper in the first region 204a of the single-layer conductive structure of the first flexible circuit board 204 is relatively small, and the proportion of copper in the second region 204b of the double-layer conductive structure is relatively large, the thermal expansion coefficient CTE of the first region 204a is greater than the thermal expansion coefficient CTE of the second region 204b.

[0167] Therefore, by designing the thermal expansion coefficient of the material of the second portion 2052 to be smaller than the thermal expansion coefficient of the material of the first portion 2051, the thermal expansion coefficient of the material of the second portion 2052 can be made close to the thermal expansion coefficient CTE of the second region 204b, and the thermal expansion coefficient of the material of the first portion 2051 can be made close to the thermal expansion coefficient CTE of the first region 204a. This design can avoid the warping of the substrate 201 caused by the large difference in expansion between the two regions at high temperature.

[0168] In the embodiment of the present application, other relevant features of the substrate 201, the electronic component 202, the first connecting trace 203 and the first flexible circuit board 204 can refer to the specific description of the first solution mentioned above, and the embodiment of the present application will not be repeated here.

[0169] In summary, an embodiment of the present application provides a functional backplane, in which a first flexible circuit board is fixedly arranged on the second surface of a substrate in a display panel through a first bonding structure. The first flexible circuit board has a first region of a single-layer conductive structure and a second region of a double-layer conductive structure. Since the proportion of conductive material per unit space of the double-layer conductive structure is higher than that of the single-layer conductive structure, the expansion amount of the second region of the double-layer conductive structure during high temperature is greater than the expansion amount of the first region of the single-layer conductive structure, and is more different from the expansion amount of the first bonding structure. The difference between the thermal expansion coefficient of the second part of the first bonding structure located in the second region and the thermal expansion coefficient of the material of the first flexible circuit board in the present application is less than 3ppm / ℃, which can avoid the expansion amount of the first bonding structure and the expansion amount of the second region of the first flexible circuit board from being too different, thereby avoiding the possibility of warping of the functional backplane and improving the yield of the functional backplane.

[0170] In an embodiment of the present application, a method for preparing a functional backplane includes:

[0171] Step S1 : forming a driving film layer and pads on the first surface 201 a of the substrate 201 , and providing a film layer for connecting the first connection pad 206 and the third connection pad 210 to the first connection trace 203 and the second connection trace 208 .

[0172] In consideration of the wiring resistance and the effective connection area, the length of the first connection pad 206 and the second connection pad 207 ranges from 0.08 mm (millimeter) to 0.2 mm, and the width is greater than 0.06 mm. The length direction of the connection pad is the arrangement direction of the first area 204a and the second area 204b in the first flexible circuit board 204, and the width direction is perpendicular to the arrangement direction of the first area 204a and the second area 204b.

[0173] Step S2: cutting off the process edge of the substrate 201 according to the required size of the final product to obtain a size suitable for splicing.

[0174] Usually, when the product substrate 201 is manufactured, the product size is not the final required size, and is generally 5 mm or more larger. Therefore, the process edge needs to be cut off to obtain the final product size.

[0175] Step S3 : attaching the first flexible circuit board 204 to the second surface 201 b of the substrate 201 by using the first bonding structure 205 , and attaching the second flexible circuit board 209 to the second surface 201 b of the substrate 201 by using the second bonding structure.

[0176] Among them, the second connection pad 207 connected to the first flexible circuit board 204 corresponds one-to-one with the first connection pad 206 of the first surface 201a in the second direction Y, and the fourth connection pad 211 connected to the second flexible circuit board 209 corresponds one-to-one with the third connection pad 210 of the first surface 201a in the second direction Y, thereby facilitating the connection of the first connection pad 207 of the first surface 201a and the second connection pad 207 of the second surface 201b through the first connection trace 203, and facilitating the connection of the third connection pad 210 of the first surface 201a and the fourth connection pad 211 of the second surface 201b through the second connection trace 208.

[0177] By designing the first flexible circuit board 204 on the second surface 201b of the substrate 201, it is possible to facilitate the first signal line connected to the first connecting line 203 to be designed for winding. In addition, by designing the second flexible circuit board 209 on the second surface 201b of the substrate 201, it is possible to facilitate the second signal line connected to the second connecting line 2083 to be designed for winding.

[0178] Among them, reference Fig.26 Taking the second flexible circuit board 209 as an example, the portion of the second signal line close to the side surface 201c of the substrate 201 occupies a larger length in the second direction Y; after winding, the portion of the second signal line away from the side surface of the substrate 201 occupies a smaller length in the second direction Y. That is, the winding design can reduce the space occupied by the signal line in the second direction Y.

[0179] Step S4 , forming the first connection wiring 203 and the second connection wiring 208 by printing, thereby achieving conduction between the first connection pad 206 and the second connection pad 207 , and achieving conduction between the third connection pad 210 and the fourth connection pad 211 .

[0180] Optionally, the materials of the first connection wiring 203 and the second connection wiring 208 may both be metals, such as copper (Cu), titanium (Ti), silver (Ag), aluminum (Al), etc. or alloys thereof.

[0181] Step S5, performing high temperature curing treatment on the first connecting wire 203 and the second connecting wire 208.

[0182] The temperature during the high temperature curing treatment of the first connection wiring 203 and the second connection wiring 208 may be greater than or equal to 150° C., and the time may be greater than or equal to 30 minutes. That is, the temperature is ≥150° C., and the time is ≥30 minutes.

[0183] Step S6: forming a protective layer.

[0184] A protective layer is formed by printing on the side of the first connection wiring 203 and the second connection wiring 208 away from the substrate 201 to prevent scratches and bumps from damaging the wiring and causing defects.

[0185] Step S7, performing high temperature curing treatment on the protective layer.

[0186] When the protective layer is subjected to high temperature curing treatment, the temperature is gradually increased from below 60°C to 150°C. Moreover, when the temperature is greater than 150°C, the temperature needs to be kept constant for more than 30 minutes. That is, the temperature is ≥150°C and the time is ≥30 minutes.

[0187] Step S8: Use a light emitting diode LED to perform die bonding on the first surface 201 a of the substrate 201 to achieve connection between the LED and the pad.

[0188] Step S9 , binding and connecting the first external circuit structure 300 and the first flexible circuit board 204 , and binding and connecting the second external circuit structure and the second flexible circuit board 209 .

[0189] The first external circuit structure 300 and the second external circuit structure can be used to provide different driving signals. Optionally, the first external circuit structure 300 is used to provide a power supply signal. The second external circuit structure is used to transmit a display signal (which can be understood as a signal that tells it to display a certain pattern, a data signal).

[0190] Step S10: blackening and encapsulating the first surface 201a of the substrate 201 to obtain an encapsulation layer, thereby achieving effects such as increased contrast and uniform display.

[0191] The terms used in the embodiments of this application are only used to explain the embodiments of this application, and are not intended to limit this application. Unless otherwise defined, the technical terms or scientific terms used in the embodiments of this application should be the common meanings understood by people with general skills in the field to which this application belongs.

[0192] The terms used in the implementation mode of the present application are only used to explain the embodiments of the present application, and are not intended to limit the present application. Unless otherwise defined, the technical terms or scientific terms used in the implementation mode of the present application should be the common meanings understood by people with ordinary skills in the field to which the present application belongs. The words "first", "second", "third" and similar words used in the patent application specification and claims of the present application do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "one" do not indicate a quantity limit, but indicate that there is at least one. Words such as "include" or "include" and similar words mean that the elements or objects appearing in front of "include" or "include" include the elements or objects listed after "include" or "include" and their equivalents, and do not exclude other elements or objects. Words such as "connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0193] The above description is only an optional embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A functional backplane, characterized in that: The functional backplane (200) comprises: substrate(201); A plurality of electronic components (202) located on a first surface (201a) of the substrate (201); A first connecting wire (203), one end of the first connecting wire (203) being located on a first surface (201a) of the substrate (201) and connected to the electronic component (202), and the other end of the first connecting wire (203) being bent from the first surface (201c) of the substrate (201) and being located on a second surface (201b) of the substrate (201); a first flexible circuit board (204) and a first bonding structure (205), wherein the first flexible circuit board (204) is located on a second surface (201b) of the substrate (201) away from the plurality of electronic components (202), the first bonding structure (205) is located between the substrate (201) and the first flexible circuit board (204), the first flexible circuit board (204) is fixedly arranged on the second surface (201b) of the substrate (201) through the first bonding structure (205), the first flexible circuit board (204) is connected to the other end of the first connecting wire (203), the first flexible circuit board (204) is also connected to a first external circuit structure (300), and the first flexible circuit board (204) is used to transmit a first driving signal provided by the first external circuit structure (300) to the electronic component (202) through the first connecting wire (203); The first flexible circuit board (204) has a first area (204a) and a second area (204b), and the first flexible circuit board (204) includes a first conductive structure (2041) located in the first area (204a), and a second conductive structure (2042) and a third conductive structure (2043) located in the second area (204b) and stacked; the first bonding structure (205) has a plurality of target portions (205a) in a strip shape located at least in the second area (204b), and the thickness of the target portion (205a) of the first bonding structure (205) is less than the thickness of other portions of the first bonding structure (205) except the target portion (205a).

2. The functional backplane according to claim 1, characterized in that: The plurality of target portions (205a) include a plurality of first grooves (C1) extending along a first direction (X) and spaced apart in a second direction (Y); The first direction (X) is the arrangement direction of the first region (204a) and the second region (204b), and the second direction (Y) is perpendicular to the arrangement direction of the first region (204a) and the second region (204b).

3. The functional backplane according to claim 2, characterized in that: The plurality of target portions (205a) further include a plurality of second grooves (C2) extending along the second direction (Y) and spaced apart in the second direction (Y); At least some of the second grooves (C2) among the plurality of second grooves (C2) are in communication with the first groove (C1).

4. The functional backplane according to claim 3, characterized in that: The plurality of second grooves (C2) are located in the middle of the second area (204b) in the first direction (X).

5. The functional backplane according to claim 3, characterized in that: The spacing between two adjacent first grooves (C1) along the second direction (Y) and the spacing between two adjacent second grooves (C2) along the second direction (Y) are both greater than or equal to 10 mm; The width of the first groove (C1) ranges from 1 mm to 5 mm, the length of the first groove (C1) is equal to the length of the second area (204b) along the first direction (X), the width of the second groove (C2) ranges from 0.5 mm to 2 mm, and the length of the second groove (C2) is less than the spacing between two adjacent second grooves (C2) along the second direction (Y).

6. The functional backplane according to claim 2, characterized in that: The plurality of target portions (205a) further include a third groove (C3) extending along a second direction (Y), wherein a length of the third groove (C3) in the second direction (Y) is equal to a length of the first fitting structure (205) in the second direction (Y); Wherein, the third groove (C3) is located at the boundary between the first area (204a) and the second area (204b).

7. The functional backplane according to claim 1, characterized in that: The plurality of target portions (205a) include a plurality of fourth grooves (C4) extending along the first direction (X) and arranged at intervals in the second direction (Y), and a plurality of fifth grooves (C5) extending along the second direction (Y) and arranged at intervals in the first direction (X); Wherein, the plurality of fourth grooves (C4) and the plurality of fifth grooves (C5) form a grid shape.

8. The functional backplane according to claim 7, characterized in that: The widths of the fourth groove (C4) and the fifth groove (C5) are both in the range of 100 microns to 150 microns, and the spacing between two adjacent fourth grooves (C4) in the second direction (Y) and the spacing between two adjacent fifth grooves (C5) in the first direction (X) are both greater than or equal to 300 microns.

9. The functional backplane according to claim 7, characterized in that: The plurality of fourth grooves (C4) and the plurality of fifth grooves (C5) are also located in the first region (204a).

10. The functional backplane according to any one of claims 1 to 9, characterized in that: The first bonding structure (205) includes a bonding material, and other parts of the first bonding structure (205) except the target part (205a) are the parts of the first bonding structure (205) having the bonding material, and the target part (205a) of the first bonding structure (205) is the part of the first bonding structure (205) not having the bonding material.

11. A functional backplane, characterized in that: The functional backplane (200) comprises: substrate(201); A plurality of electronic components (202) on a first surface (201a) of the substrate (201); A first connecting wire (203), one end of the first connecting wire (203) being located on a first surface (201a) of the substrate (201) and connected to the electronic component (202), and the other end of the first connecting wire (203) being bent from the first surface (201c) of the substrate (201) and being located on a second surface (201b) of the substrate (201); a first flexible circuit board (204) and a first bonding structure (205), wherein the first flexible circuit board (204) is located on a second surface (201b) of the substrate (201) away from the plurality of electronic components (202), the first bonding structure (205) is located between the substrate (201) and the first flexible circuit board (204), the first flexible circuit board (204) is fixedly arranged on the second surface (201b) of the substrate (201) through the first bonding structure (205), the first flexible circuit board (204) is connected to the other end of the first connecting wire (203), the first flexible circuit board (204) is also connected to a first external circuit structure (300), and the first flexible circuit board (204) is used to transmit a first driving signal provided by the first external circuit structure (300) to the electronic component (202) through the first connecting wire (203); The first flexible circuit board (204) has a first region (204a) and a second region (204b), the first flexible circuit board (204) comprises a first conductive structure (2041) located in the first region (204a), and a second conductive structure (2042) and a third conductive structure (2043) located in the second region (204b) and stacked, the first conductive structure (2041), the second conductive structure (2042) and the third conductive structure (2043) being made of the same material; the first bonding structure (205) comprises a first portion (2051) located in the first region (204a) and a second portion (2052) located in the second region (204b), the difference between the thermal expansion coefficient of the material of the second portion (2052) and the thermal expansion coefficient of the material of the first conductive structure (2041) being less than 1 part per million per degree Celsius.

12. The functional backplane according to claim 11, characterized in that: The first conductive structure (2041), the second conductive structure (2042) and the third conductive structure (2043) are all made of copper; The coefficient of thermal expansion of the material of the second portion (2052) is less than or equal to 20 parts per million per degree Celsius.

13. The functional backplane according to claim 11, characterized in that: The material of the second part (2052) is different from the material of the first part (2051), and the thermal expansion coefficient of the material of the second part (2052) is smaller than the thermal expansion coefficient of the material of the first part (2051).

14. The functional backplane according to any one of claims 1 to 9 and 11 to 13, characterized in that: The functional backplane (200) further comprises: A second connecting wire (208), one end of the second connecting wire (208) being located on the first surface (201a) of the substrate (201) and connected to the electronic component (202), the other end of the second connecting wire (208) being bent from the second surface (201d) of the substrate (201) and being located on the second surface (201b) of the substrate (201), the second surface (201d) and the first surface (201c) being located opposite to each other; a second flexible circuit board (209) and a second bonding structure, wherein the second flexible circuit board (209) is located on a second surface (201b) of the substrate (201) away from the electronic component (202), and the second flexible circuit board (209) and the first flexible circuit board (204) are spaced apart in a first direction (X), the second bonding structure is located between the substrate (201) and the second flexible circuit board (209), the second flexible circuit board (209) is fixedly arranged on the second surface (201b) of the substrate (201) through the second bonding structure, the second flexible circuit board (209) is connected to the other end of the second connecting wire (208), the second flexible circuit board (209) is also connected to a second external circuit structure, and the second flexible circuit board (209) is used to transmit a second driving signal provided by the second external circuit structure to the electronic component (202) through the second connecting wire (208); The second flexible circuit board (209) comprises a fourth conductive structure, and the thickness of each region of the second bonding structure is the same.

15. A light emitting device, characterized in that: The light emitting device comprises: a power supply component and a functional backplane as claimed in any one of claims 1 to 14; Wherein, the power supply component is used to supply power to the functional backplane.

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