Backlight module, preparation method thereof and display equipment

Abstract

The embodiment of the invention provides a backlight module, a preparation method of the backlight module and display equipment, and relates to the technical field of display, and the backlight module comprises a substrate, a plurality of light-emitting chips, a plurality of first binding pins, a flexible circuit board and a welding layer. The light-emitting chips are arranged on the substrate in an array mode and located in the main body area. The distance between every two adjacent light-emitting chips is smaller than or equal to 200 micrometers. The plurality of first binding pins are arranged on the substrate and located in the binding area. The flexible circuit board comprises a flexible substrate and a plurality of second binding pins; the welding layer is located between the flexible circuit board and the substrate; and the second binding pin is electrically connected with the first binding pin through the welding layer. According to the scheme, mounting of the light-emitting chip and binding of the flexible circuit board are integrated into the synchronous reflow soldering technology, the welding layer with the thickness smaller than or equal to 30 microns is formed, the connection reliability of the flexible circuit board and the substrate is improved, and finally the production efficiency and the product yield are improved.

Description

Technical Field

[0001] This application relates to the field of display technology, and in particular to a backlight module, its manufacturing method, and a display device. Background Technology

[0002] In the design of conventional Mini LED backlight panels, the electrical connection between the backlight panel substrate and the flexible circuit board is a core technological step. Existing technologies mainly employ two connection methods: anisotropic conductive adhesive bonding and thermoforming welding. However, both of these processes have limitations in practical applications. For example, anisotropic conductive adhesive bonding is highly dependent on the substrate material, and it is difficult to achieve stable and reliable curing on some high thermal conductivity substrates, affecting connection strength and long-term reliability. During the thermoforming welding process, the final state of the weld interface is easily affected by various factors, making it difficult to guarantee the reliability of the connection interface. Overall, existing bonding methods still have shortcomings in terms of connection reliability. Summary of the Invention

[0003] The purpose of this application is to provide a backlight module and its preparation method, as well as a display device. The aim is to integrate the mounting of the light-emitting chip and the bonding of the flexible circuit board into a synchronous reflow soldering process to form a solder layer with a thickness of less than or equal to 30 μm, thereby improving the connection reliability between the flexible circuit board and the substrate. This avoids reliability risks such as unstable contact resistance, poor connection or delamination caused by poor curing, and ultimately improves production efficiency and product yield.

[0004] To achieve the above objectives, the embodiments of this disclosure provide the following technical solutions: In a first aspect, a backlight module is provided, which includes a substrate, multiple light-emitting chips, multiple first bonding pins, a flexible circuit board, and a bonding layer.

[0005] The substrate has a main region and a bonding region located on one side of the main region. Multiple light-emitting chips are arranged in an array on the substrate and located within the main region; the spacing between two adjacent light-emitting chips is less than or equal to 200 μm. Multiple first bonding pins are disposed on the substrate and located within the bonding region. The flexible circuit board includes a flexible substrate and multiple second bonding pins disposed on the flexible substrate. The portion of the flexible substrate with the multiple second bonding pins is stacked with the bonding region of the substrate, and the surface of the flexible substrate with the multiple second bonding pins is close to the surface of the substrate with the multiple first bonding pins. A solder layer is located between the flexible circuit board and the substrate; the second bonding pins and the first bonding pins are electrically connected through the solder layer. The thickness of the solder layer is less than or equal to 30 μm; the thickness is the dimension of the solder layer in the direction perpendicular to the substrate.

[0006] In the backlight module provided in this application embodiment, the mounting of the light-emitting chip and the bonding of the flexible circuit board are completed simultaneously through the synchronous reflow soldering process. This allows the solder layer to obtain a dense structure of less than or equal to 30μm during the formation process, which simplifies the process flow. Moreover, the metal soldering solution has higher connection reliability and electrical stability compared to ACF adhesive bonding, thereby avoiding reliability problems such as unstable contact resistance, poor connection or delamination caused by poor curing of ACF adhesive. Ultimately, this improves production efficiency and product yield.

[0007] In some embodiments, the solder layer includes a bonding layer and two intermetallic compound layers, the two intermetallic compound layers being located between the first bonding pin and the bonding layer, and between the second bonding pin and the bonding layer, respectively; the dimension of each intermetallic compound layer in the direction perpendicular to the substrate is at least 10% of the thickness of the solder layer.

[0008] In some embodiments, the substrate includes a first sublayer and a second sublayer, the first sublayer being conductive and the second sublayer being electrically insulating, and a first bonding pin being disposed on the side of the second sublayer away from the first sublayer.

[0009] In some embodiments, a first opening is formed on the flexible circuit board, the first opening penetrating the second bonding pin; at least a portion of the solder layer also fills the first opening.

[0010] In some embodiments, the flexible circuit board further includes a plurality of third bonding pins, which correspond one-to-one with a plurality of second bonding pins and are stacked on top of each other, and the third bonding pins and the second bonding pins are respectively located on both sides of the flexible substrate.

[0011] The flexible circuit board has a second opening that passes through the second bonding pin, the flexible substrate, and the third bonding pin in sequence; at least part of the solder layer also fills the second opening.

[0012] In some embodiments, at least a portion of the solder layer is also located on the surface of the third bonding pin, which is remote from the second bonding pin, where the second opening is provided.

[0013] In some embodiments, the portion of the solder layer located on the surface of the third bonding pin away from the second bonding pin further includes a first sub-part and a second sub-part; the second sub-part is located between the third bonding pin and the first sub-part, and the second sub-part is an intermetallic compound.

[0014] In some embodiments, a plurality of third bonding pins are arranged in a direction parallel to the substrate; each third bonding pin has a second opening; the second openings on two adjacent third bonding pins are staggered in the orthographic projection of the reference surface; the reference surface is perpendicular to the substrate and perpendicular to the arrangement direction of the plurality of third bonding pins.

[0015] In some embodiments, the backlight module further includes a wiring layer and a solder mask layer. The wiring layer is disposed on a substrate, and a portion of the wiring layer forms first bonding pins. The solder mask layer is stacked on the side of the wiring layer away from the substrate. The solder mask layer has multiple first openings, each exposing a first bonding pin. Each of the multiple first openings corresponds one-to-one with a multiple of the first bonding pins, and adjacent first openings are spaced apart.

[0016] In some embodiments, the backlight module further includes a plurality of first identification units and a plurality of second identification units.

[0017] The system comprises a plurality of first identification portions disposed on a substrate, the plurality of first identification portions surrounding a region containing a plurality of first bonding pins, and at least two of the plurality of first identification portions being located diagonally opposite each other within the region containing the plurality of first bonding pins. A plurality of second identification portions are disposed on a flexible substrate, the plurality of second identification portions surrounding a region containing a plurality of second bonding pins, and are stacked in a one-to-one correspondence with the plurality of first identification portions; the second identification portions are made of a transparent material. The plurality of first identification portions and the plurality of second identification portions are configured to be aligned with each other such that the plurality of first bonding pins and the plurality of second bonding pins are stacked in a one-to-one correspondence.

[0018] Secondly, a method for preparing a backlight module is provided, comprising: setting welding material on a lamp board, stacking a flexible circuit board on a bonding area of ​​a substrate, and processing the welding material using a welding process to form a welding layer.

[0019] The light board includes a substrate and multiple first bonding pins. The substrate has a main area and a bonding area located on one side of the main area. The main area of ​​the substrate is configured to carry multiple light-emitting chips, and the spacing between two adjacent light-emitting chips is less than or equal to 200 μm. The multiple first bonding pins are disposed on the substrate and located within the bonding area. Soldering material is located on the first bonding pins. The flexible circuit board includes a flexible substrate and multiple second bonding pins disposed on the flexible substrate. The portion of the flexible substrate with the multiple second bonding pins is stacked with the bonding area of ​​the substrate, and the surface of the flexible substrate with the multiple second bonding pins is close to the surface of the substrate with the multiple first bonding pins. The multiple second bonding pins correspond one-to-one with the multiple first bonding pins and are stacked. The second bonding pins and the first bonding pins are electrically connected through a solder layer. The thickness of the solder layer is less than or equal to 30 μm, and the thickness is the dimension of the solder layer in the direction perpendicular to the substrate.

[0020] The fabrication method provided in this application simultaneously mounts the light-emitting chip and bonds the flexible circuit board in a single reflow soldering process, forming a dense solder layer with a thickness of less than or equal to 30 μm in a single soldering operation, thus simplifying the process flow. This method uses metal soldering instead of ACF adhesive bonding, achieving higher connection reliability and electrical stability. It effectively avoids reliability issues such as unstable contact resistance, incomplete connections, or delamination caused by poor ACF adhesive curing, thereby improving production efficiency and product yield.

[0021] In some embodiments, the preparation method further includes: setting a second welding material in the main body region, setting a plurality of light-emitting chips in the main body region, and processing the second welding material using a welding process to form a second welding layer.

[0022] The second welding material is located between the light-emitting chip and the substrate. The light-emitting chip and the substrate are electrically connected through the second welding layer. The formation of the welding layer and the formation of the second welding layer are performed simultaneously.

[0023] In some embodiments, the light board further includes a plurality of first identification portions disposed on the substrate and arranged around the area where the plurality of first bonding pins are located, with at least two of the plurality of first identification portions located diagonally opposite to the area where the plurality of first bonding pins are located; the flexible circuit board further includes a plurality of second identification portions disposed on the flexible substrate and arranged around the area where the plurality of second bonding pins are located, with at least two of the plurality of second identification portions located diagonally opposite to the area where the plurality of second bonding pins are located.

[0024] The flexible circuit board stacked on the bonding area of ​​the substrate includes: identifying the positions of a first identification portion and a second identification portion; and attaching the flexible circuit board to the bonding area based on the positions of a plurality of first identification portions and a plurality of second identification portions.

[0025] In this configuration, multiple first identification units and multiple second identification units are aligned one-to-one, so that multiple first binding pins and multiple second binding pins are aligned one-to-one and stacked.

[0026] In some embodiments, the material of the second identification part is a transparent material, and the dimensions of the second identification part in the direction parallel to the substrate are all larger than the dimensions of the first identification part in the direction parallel to the substrate.

[0027] The process includes, after the flexible circuit board is stacked on the bonding area of ​​the substrate and before the welding process is used to form a welding layer, the method further includes: obtaining the offset of the geometric center of the first identification part relative to the geometric center of the corresponding second identification part; and adjusting the position of the flexible circuit board based on the offset being greater than a preset threshold. The preset threshold is one-third of the dimension of the first identification part in the direction parallel to the substrate.

[0028] In some embodiments, before applying the soldering material to the lamp board, the method further includes: placing a substrate on a base. After the flexible circuit board is stacked on the bonding area of ​​the substrate, and before the soldering material is processed using a soldering process to form a solder layer, the method further includes: stacking a cover sheet on the side of the lamp board and the flexible circuit board away from the base.

[0029] The cover has multiple second openings and multiple third openings; the second openings expose the light-emitting chip, and the third openings expose the areas where the first and second bonding pins are located; the cover is configured to fix the lamp board and the flexible circuit board between the base and the cover.

[0030] Thirdly, a display device is provided, comprising a display panel and a backlight module provided in any embodiment of the first aspect. The display panel is disposed on the light-emitting side of the backlight module.

[0031] The technical effects brought about by the display device in the third aspect can be seen in the technical effects brought about by the backlight module design in the first aspect, and will not be repeated here. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in this application, the accompanying drawings used in some embodiments of this application will be briefly described below. Obviously, the drawings described below are only drawings of some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings. In addition, the drawings described below can be regarded as schematic diagrams and are not intended to limit the actual size of the product, the actual flow of the method, the actual timing of the signals, etc. involved in the embodiments of this application.

[0033] Figure 1 A structural diagram of a backlight module provided in an embodiment of this application; Figure 2 A cross-sectional view of a backlight module provided in an embodiment of this application; Figure 3 for Figure 2 A magnified view of the corresponding binding area in the image; Figure 4 A top view of the first bonding pin and the second bonding pin provided in an embodiment of this application; Figure 5 for Figure 4 A cross-sectional view along the tangent line NN' in the middle; Figure 6 for Figure 5 The enlarged view of the area corresponding to the dashed box Q1 in the image; Figure 7 for Figure 6 The enlarged view corresponding to the dashed box Q2 in the image; Figure 8 for Figure 5 The enlarged view of the area corresponding to the dashed box Q3 in the image; Figure 9 A flowchart illustrating a method for fabricating a backlight module provided in an embodiment of this application; Figures 10-14 Another flowchart illustrating the fabrication method of the backlight module provided in this application embodiment; Figure 15 A physical image of a cover plate attachment substrate provided in an embodiment of this application; Figure 16 A top view of the substrate to which the cover plate is attached, provided in an embodiment of this application; Figure 17 Another flowchart illustrating the fabrication method of the backlight module provided in this application embodiment; Figure 18 A physical image of a flexible circuit board after reflow soldering, provided in an embodiment of this application; Figure 19 An X-ray confirmation image of the welding status of a flexible circuit board provided in an embodiment of this application; Figure 20 A comparison diagram of the solder paste state before soldering provided in an embodiment of this application; Figure 21 This is a schematic diagram of a display device provided in an embodiment of this application. Detailed Implementation

[0034] The technical solutions in some embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments provided in this disclosure are within the scope of protection of this disclosure.

[0035] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as open-ended and encompassing, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.

[0036] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0037] In describing some embodiments, the terms "coupled" and "connected," and their derivative expressions, may be used. The term "connected" should be interpreted broadly; for example, a "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection via an intermediate medium. The term "coupled," for example, indicates that two or more components have direct physical or electrical contact. The term "coupled" or "communicatively coupled" may also refer to two or more components that do not have direct contact with each other but still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the content of this document.

[0038] "At least one of A, B and C" has the same meaning as "at least one of A, B or C", both including the following combinations of A, B and C: only A, only B, only C, combinations of A and B, combinations of A and C, combinations of B and C, and combinations of A, B and C.

[0039] "A and / or B" includes the following three combinations: A only, B only, and a combination of A and B.

[0040] As used herein, depending on the context, the term “if” may optionally be interpreted as meaning “when”, “in the event of”, “in response to determination”, or “in response to detection”. Similarly, depending on the context, the phrase “if it is determined that…” or “if [the stated condition or event] is detected” may optionally be interpreted as meaning “in the event of determination that…”, “in response to determination that…”, “when [the stated condition or event] is detected”, or “in response to the detection of [the stated condition or event]”.

[0041] The use of “applies to” or “configured to” in this article implies an open and inclusive language that does not preclude applicability to or configuration to devices that perform additional tasks or steps.

[0042] In addition, the use of “based on” implies openness and inclusivity, because processes, steps, calculations or other actions “based on” one or more of the stated conditions or values ​​may in practice be based on additional conditions or values ​​beyond those stated.

[0043] As used herein, “about,” “approximately,” or “approximately” includes the stated value and the average value within an acceptable range of deviation from the given value, wherein the acceptable range of deviation is determined by a person skilled in the art taking into account the measurement under discussion and the error associated with the measurement of the given quantity (i.e., the limitations of the measurement system).

[0044] As used herein, “parallel,” “perpendicular,” and “equal” include the described situation and situations that are similar to the described situation, within an acceptable deviation range, which is determined by those skilled in the art taking into account the measurement under discussion and the errors associated with the measurement of a particular quantity (i.e., the limitations of the measurement system). For example, “parallel” includes absolute parallelism and approximate parallelism, where an acceptable deviation range for approximate parallelism may be, for example, within 5°; “perpendicular” includes absolute perpendicularity and approximate perpendicularity, where an acceptable deviation range for approximate perpendicularity may also be, for example, within 5°; “equal” includes absolute equality and approximate equality, where an acceptable deviation range for approximate equality may be, for example, a difference between the two equals being less than or equal to 5% of either one.

[0045] It should be understood that when a layer or element is referred to as being on another layer or substrate, it can mean that the layer or element is directly on the other layer or substrate, or that there is an intermediate layer between the layer or element and the other layer or substrate.

[0046] This document describes exemplary embodiments with reference to cross-sectional views and / or plan views, which are idealized exemplary drawings. In the drawings, the thickness of layers and the area of ​​regions are enlarged for clarity. Therefore, variations in shape relative to the drawings are contemplated due to, for example, manufacturing techniques and / or tolerances. Thus, exemplary embodiments should not be construed as being limited to the shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing processes. For example, etched areas shown as rectangular would typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to show the actual shapes of the areas of the device, nor are they intended to limit the scope of the exemplary embodiments.

[0047] This application provides a backlight module 100.

[0048] Figure 1 This is a structural diagram of a backlight module 100 provided in an embodiment of this application.

[0049] Figure 2 This is a cross-sectional view of a backlight module 100 provided in an embodiment of this application.

[0050] Figure 3 for Figure 2A magnified view of the area corresponding to binding zone 12 in the image.

[0051] Figure 4 A top view of the first bonding pin 3 and the second bonding pin 42 provided in the embodiments of this application.

[0052] In some embodiments, see Figure 1 The backlight module 100 includes a substrate 1, multiple light-emitting chips 2, multiple first bonding pins 3, a flexible circuit board 4, and a bonding layer 5.

[0053] See Figure 1 The substrate 1 has a main region 11 and a bonding region 12 located on one side of the main region 11. Multiple light-emitting chips 2 are arranged in an array on the substrate 1 and located within the main region 11; the spacing between two adjacent light-emitting chips 2 is less than or equal to 200 μm.

[0054] In the above structure, a backlight board is formed by a light-emitting chip 2 disposed on the substrate 1. The light-emitting chip 2 includes lamp beads (e.g., LEDs). In this embodiment, the spacing between adjacent LEDs is less than or equal to 200um, forming a Mini LED arrangement. Compared to a conventional backlight module 100, this spacing is significantly smaller than the conventional lamp bead spacing, allowing the light-emitting chip 2 to achieve high-density integration within the main body area 11. Based on this high-density arrangement, the backlight is divided into more independent controllable zones, thereby achieving fine local dimming and realizing the high contrast, high brightness uniformity, and delicate image quality performance unique to Mini LED backlighting.

[0055] For example, the light-emitting chip 2 may also include an IC, that is, both the LED and the IC are disposed on the substrate 1. The LED serves as a light-emitting unit to provide a backlight source, and the IC serves as a drive control unit to independently control the LED. Together, they constitute a complete light-emitting and driving assembly.

[0056] For example, the surface of the light-emitting chip 2 may be provided with a protective adhesive, which is used to protect the light-emitting chip 2 (such as an LED chip) from external environmental corrosion and to adjust the light pattern. Depending on the specific optical design requirements, the protective adhesive can be a flat adhesive structure to achieve a uniform light emission effect; or it can be a lens structure to control the light emission angle by focusing or diffusing, thereby meeting the optical requirements of different backlight modules 100.

[0057] See Figure 1 Multiple first bonding pins 3 are disposed on the substrate 1 and located within the bonding area 12. The multiple first bonding pins 3 of the bonding area 12 are used for electrical connection with external driving components (such as driving chips, driving circuit boards or flexible circuit boards 4).

[0058] Specifically, the first bonding pin 3 serves as the electrical interface between the substrate 1 and the external driver. The external driver element establishes a connection with the first bonding pin 3 through a bonding process, thereby transmitting control signals and driving currents to the light-emitting chips 2 on the substrate 1 to achieve independent control of each light-emitting chip 2. Based on this connection method, fine dimming in the Mini LED backlight solution can be achieved.

[0059] See Figure 1 , Figure 2 and Figure 3 The flexible circuit board 4 includes a flexible substrate 41 and a plurality of second bonding pins 42 disposed on the flexible substrate 41; the portion of the flexible substrate 41 with the plurality of second bonding pins 42 is stacked with the bonding area 12 of the substrate 1, and the surface A of the flexible substrate 41 with the plurality of second bonding pins 42 is close to the surface B of the substrate 1 with the plurality of first bonding pins 3.

[0060] That is, one end of a plurality of second bonding pins 42 on the flexible circuit board 4 is bonded to the bonding area 12 of the substrate 1, for example, see [reference]. Figure 1 By aligning and bonding the second bonding pin 42 of the flexible substrate 41 with the bonding area 12, the second bonding pin 42 and the corresponding first bonding pin 3 are pressed or welded together, thereby completing the electrical connection.

[0061] For example, the other end of the flexible circuit board 4 is also electrically connected to the PCB (printed circuit board), so that the external drive signals and power on the PCB are transmitted to the first bonding pin 3 on the substrate 1 via the flexible circuit board 4, thereby realizing independent control of multiple light-emitting chips 2 in the main body area 11.

[0062] It is worth noting that, Figure 1 Only the distribution of multiple first bonding pins 3 and multiple second bonding pins 42 is shown, and Figure 1 From a top-down perspective, the first bonding pin 3 and the second bonding pin 42 appear to overlap and be located in the same area on the bonding area 12 in the diagram; the detailed arrangement of each pin is not shown. For the specific arrangement of the first bonding pin 3 and the second bonding pin 42, please refer to [reference needed]. Figure 4 As shown.

[0063] For example, considering the effective soldering area of ​​the first bonding pin 3 and the second bonding pin 42 in subsequent processes and the risk of solder bridging and short circuits, the dimensions of the two can be specifically designed in this embodiment. To further improve the soldering compatibility between the first bonding pin 3 and the second bonding pin 42, they can adopt a uniform size design to ensure uniform solder distribution during the soldering process and avoid poor soldering or solder bridging and short circuits between adjacent pins due to size differences.

[0064] For example, see Figure 4 The length (i.e., the dimension in the second direction Y) of the first bonding pin 3 (or the second bonding pin 42) is greater than or equal to 1.5 mm, which can increase the effective solder removal distance; the width (i.e., the dimension in the first direction X) of the first bonding pin 3 (or the second bonding pin 42) is greater than or equal to 0.5 mm, which can increase the effective soldering area between the two; the spacing between two adjacent first bonding pins 3 (or second bonding pins 42) in the first direction X is greater than or equal to 0.3 mm, which prevents the risk of solder bridging between adjacent first bonding pins 3 (or second bonding pins 42).

[0065] See Figure 2 and Figure 3 The solder layer 5 is located between the flexible circuit board 4 and the substrate 1; the second bonding pin 42 and the first bonding pin 3 are electrically connected through the solder layer 5.

[0066] For example, the material of the solder layer 5 can be solder paste.

[0067] Specifically, solder paste can be applied to the surface of the first bonding pin 3 and / or the second bonding pin 42 by printing or dot coating, and the solder paste can be applied to the position where the light-emitting chip 2 is aligned and attached in the main body region 11. Subsequently, the solder paste is melted by a reflow soldering process. In the bonding region 12, the molten solder paste forms a reliable electrical connection and mechanical fixation between the first bonding pin 3 and the second bonding pin 42, i.e., the solder layer 5; at the same time, in the main body region 11, the molten solder paste fixes the light-emitting chip 2 to the substrate 1 and realizes electrical conduction.

[0068] For example, in this embodiment, the second bonding pin 42 of the flexible substrate 41 can be pre-aligned and bonded to the first bonding pin 3 of the bonding area 12, and then the bonding connection of the flexible circuit board 4 and the mounting of the light-emitting chip 2 can be completed simultaneously through the same reflow soldering process. During the reflow soldering process, the solder paste melts and forms the aforementioned solder layer 5 in the bonding area 12. This process simplifies the manufacturing process and improves the soldering quality and product reliability.

[0069] Among them, see Figure 2 and Figure 3 The thickness of the welding layer 5 is less than or equal to 30 μm; the thickness is the dimension of the welding layer 5 in the direction perpendicular to the substrate 1 (and the third direction Z).

[0070] For example, in other embodiments, when the flexible circuit board 4 is bonded using a hot bar bonding process, the resulting solder layer 5 is typically about 40 μm thick. In this solution, however, the thickness of the solder layer 5 can be controlled to 30 μm or less. A thinner solder layer 5 results in a denser intermetallic compound structure, lower contact resistance at the solder-pin interface, and less signal transmission loss. This significantly improves the performance of the high-density, high-frequency drive signal transmission required by the Mini LED backlight module 100 used in this solution. Simultaneously, a thinner solder layer 5 helps reduce interfacial thermal stress caused by mismatched coefficients of thermal expansion, improving the reliability of the bonding area 12 during long-term use.

[0071] It is worth noting that, unlike the bonding structures formed by anisotropic conductive adhesive or non-conductive adhesive in other embodiments, the solder layer 5 is a metal metallurgical bonding layer formed by solder paste through a soldering process. Its material properties, conductivity and reliability are superior to the ACF adhesive bonding structure.

[0072] For example, a simultaneous reflow soldering process can be used to simultaneously mount the light-emitting chip 2 and bond it to the flexible circuit board 4 to obtain the required thickness of the solder layer 5 in this embodiment.

[0073] In the backlight module 100 provided in this application embodiment, the mounting of the light-emitting chip 2 and the bonding of the flexible circuit board 4 are completed simultaneously through the synchronous reflow soldering process, so that the welding layer 5 obtains a dense structure of less than or equal to 30μm during the formation process. This simplifies the process flow, and the metal welding solution has higher connection reliability and electrical stability than ACF adhesive bonding, thereby avoiding reliability problems such as unstable contact resistance, poor connection or delamination caused by poor curing of ACF adhesive, and ultimately improving production efficiency and product yield.

[0074] Figure 5 for Figure 4 A cross-sectional view along the NN' tangent.

[0075] Figure 6 for Figure 5 The enlarged view of the area corresponding to the dashed box Q1 in the image.

[0076] Figure 7 for Figure 6 The enlarged view corresponding to the dashed box Q2 in the image.

[0077] Figure 8 for Figure 5 The enlarged view corresponding to the dashed box Q3 in the image.

[0078] in, Figures 5-8 All images are SEM (scanning electron microscope) images of sections of flexible circuit board 4 after one reflow soldering.

[0079] In some embodiments, see Figure 7 The solder layer 5 includes a connecting layer 51 and two intermetallic compound layers 52. The two intermetallic compound layers 52 are located between the first bonding pin 3 and the connecting layer 51, and between the second bonding pin 42 and the connecting layer 51, respectively. The dimension of each intermetallic compound layer 52 in the direction perpendicular to the substrate 1 is at least 10% of the thickness of the solder layer 5.

[0080] For example, the intermetallic compound layer 52 (i.e., the IMC alloy layer) is a core indicator of soldering quality. It is an intermediate compound layer formed by the reaction of solder paste with the first bonding pin 3 (or the second bonding pin 42) during soldering. Currently, it is known that the single-layer intermetallic compound layer 52 obtained by existing hot bar soldering methods accounts for approximately 6% of the thickness of the solder layer 5.

[0081] For example, the connection layer 51 is the portion remaining after the solder paste reacts with the metal first bonding pin 3 (or the second bonding pin 42) during soldering to form an intermetallic compound layer 52. The connection layer 51 and the two intermetallic compound layers 52 together constitute the solder layer 5, which is used to connect the first bonding pin 3 and the second bonding pin 42.

[0082] For example, such as Figures 5-7 As shown, the thickness of the solder layer 5 (i.e., the distance in the third direction Z between the surfaces of the first bonding pin 3 and the second bonding pin 42 that are close to each other) is measured to be approximately 25 μm to 30 μm; Figure 7 As shown, the first bonding pin 3 and the second bonding pin 42 react with solder paste to generate an intermetallic compound layer 52 of about 3μm to 4μm. Based on this, it is calculated that the single-layer intermetallic compound layer 52 (i.e., the intermetallic compound layer 52 between the first bonding pin 3 and the connection layer 51, or the intermetallic compound layer 52 between the second bonding pin 42 and the connection layer 51) accounts for about 10% to 16% of the thickness of the solder layer 5.

[0083] For example, in actual reliability verification, the pull-out force test after soldering of the flexible circuit board 4 is usually performed on the bonding strength between a single-sided pin and the solder layer 5, that is, mainly examining the interface bonding quality on one side of the first bonding pin 3 or the second bonding pin 42. Therefore, the proportion of the thickness of the single-layer intermetallic compound layer 52 (i.e., the IMC layer between the first bonding pin 3 and the connecting layer 51, or the IMC layer between the second bonding pin 42 and the connecting layer 51) to the total thickness of the solder layer 5 can intuitively reflect the degree of reaction and bonding state of the interface on that side, providing a reference for the interface bonding strength.

[0084] Compared to existing thermocompression bonding solutions, the proportion of the single-layer intermetallic compound layer 52 in this embodiment is higher, indicating that the chemical reaction between the solder paste and the pins is more complete, and the bonding strength and conductivity reliability of the solder interface are effectively improved.

[0085] For example, see Figure 5 At the location of the flexible substrate 41, that is, at least one side of the flexible substrate 41, a PI protective layer (polyimide protective layer) can also be provided. This protective layer is used to protect the conductive film layer (such as Cu layer) on the flexible substrate 41 from oxidation and scratch damage, while enhancing the bending resistance of the flexible circuit board 4 and improving its structural stability and service life during the bonding process with the substrate 1.

[0086] For example, the surface of the flexible substrate 41 is also provided with green solder mask (i.e., solder resist ink). The green solder mask covers the surface of the conductive circuit layer (such as the copper layer) of the flexible substrate 41, and plays an insulating protection role to prevent the circuit from oxidizing, short-circuiting or being corroded by the external environment.

[0087] In some embodiments, see Figure 3 The substrate 1 includes a first sublayer 13 and a second sublayer 14. The first sublayer 13 is conductive, and the second sublayer 14 is electrically insulating. The first bonding pin 3 is disposed on the side of the second sublayer 14 away from the first sublayer.

[0088] For example, the first sublayer 13 may be made of aluminum substrate 1 or other materials with higher thermal conductivity than conventional substrates such as glass and FR4 (the thermal conductivity of aluminum is about 200 W / (m·K), which is much higher than that of glass substrate 1.3 W / (m·K) and FR4 0.3 W / (m·K)).

[0089] When the substrate 1 uses a first sublayer 13 with high thermal conductivity, if anisotropic conductive adhesive (ACF) is used for bonding, the heat from the hot press head will be quickly diffused and dissipated by the aluminum substrate 1 with high thermal conductivity before it is transferred to the ACF adhesive layer. This makes it difficult for the ACF adhesive to reach the required curing temperature, resulting in incomplete curing and unreliable bonding.

[0090] In this embodiment, a solder layer 5 is used for bonding. The solder paste is melted through the soldering process to form a bonding layer between the metals. The heating method is more uniform, and the instantaneous heat demand of metal soldering has good process compatibility with the heat dissipation capacity of the substrate 1. It can effectively avoid the heat loss problem caused by the high thermal conductivity substrate 1, ensure that the bonding area 12 obtains a stable and reliable electrical connection, and avoid the defects of ACF bonding on the high thermal conductivity substrate 1, such as process limitations and poor curing reliability.

[0091] In other embodiments, some Al substrates 1 are connected to the PCB via CNT connectors to drive the light-emitting chips 2 on the Al substrate 1. However, CNT connectors have certain physical dimensions, which not only increases the bezel area of ​​the backlight module 100, but also, due to their thickness, when the optical film is directly bonded to the backlight board, the thickness of the CNT will create a gap between the film and the protective adhesive of the light-emitting chip 2. This gap constitutes a certain optical distance (OD), making it difficult to achieve the ideal zero optical distance (0 OD) bonding state.

[0092] In contrast, this embodiment uses a flexible circuit board 4 to bond and connect with the Al substrate 1, which eliminates the physical space occupied by the connector. This reduces the frame width and avoids the OD gap caused by the connector thickness, providing a structural basis for achieving 0 OD bonding.

[0093] In some embodiments, see Figure 4 The flexible circuit board 4 has a first opening P1 through which the second bonding pin 42 passes; at least part of the solder layer 5 is also filled in the first opening P1.

[0094] Specifically, the first opening P1 provides drainage space for excess solder during soldering, allowing molten solder paste to partially flow into the first opening P1 during the soldering process. This reduces the accumulation of solder between the second bonding pin 42 and the first bonding pin 3, avoiding the risk of short circuit due to excessive solder or abnormal increase in the thickness of the solder layer 5, thereby improving the soldering reliability of the bonding area 12.

[0095] In some embodiments, see Figure 2 , Figure 3 and Figure 5 The flexible circuit board 4 also includes a plurality of third bonding pins 43, which correspond one-to-one with a plurality of second bonding pins 42 and are stacked, and the third bonding pins and the second bonding pins 42 are respectively located on both sides of the flexible substrate 41.

[0096] That is, such as Figure 3 As shown, the flexible substrate 41 has two surfaces that are arranged opposite each other along the thickness direction (i.e., the third direction Z). As can be seen from the above, the surface A with a plurality of second bonding pins 42 and the surface B of the substrate 1 with a plurality of first bonding pins 3 are close to each other, and the other surface C where the third bonding pins 43 are located is set away from the substrate 1, forming a double-sided pin structure of the flexible circuit board 4.

[0097] Among them, see Figure 4 and Figure 5The flexible circuit board 4 has a second opening P2, which passes through the second bonding pin 42, the flexible substrate 41 and the third bonding pin 43 in sequence; at least part of the solder layer 5 is also filled in the second opening P2.

[0098] Specifically, the second opening P2 provides a drainage space for excess solder during soldering, allowing the molten solder paste to be guided through the second opening P2 in the thickness direction (i.e., the third direction Z). This structure can more effectively guide excess solder to the back side of the flexible circuit board 4, thereby further reducing the accumulation of solder between the second bonding pin 42 and the first bonding pin 3, avoiding the risk of short circuit due to excessive solder or abnormal increase in the thickness of the solder layer 5. At the same time, the filling of the second opening P2 with solder enhances the bonding strength of the second bonding pin 42, the flexible substrate 41 and the third bonding pin 43 in the thickness direction, thereby improving the soldering reliability of the bonding area 12.

[0099] In some embodiments, see Figure 2 , Figure 3 , Figure 5 and Figure 6 At least a portion of the solder layer 5 is also located on the surface of the third bonding pin 43, which has a second opening P2, away from the second bonding pin 42.

[0100] Specifically, during the soldering process, after the molten solder paste fills the second opening P2, some of the solder overflows to one side of the surface of the third bonding pin 43 and spreads along the surface, forming an additional soldering coverage area, which further improves the soldering reliability of the bonding area 12 and prevents the surface oxidation of the third bonding pin 43 during long-term use.

[0101] In some embodiments, see Figure 8 The portion of the solder layer 5 located on the surface of the third bonding pin 43 away from the second bonding pin 42 also includes a first sub-part 53 and a second sub-part 54; the second sub-part 54 is located between the third bonding pin 43 and the first sub-part 53, and the second sub-part is an intermetallic compound.

[0102] For example, such as Figure 8As shown, the combined thickness of the first sub-part 53 and the second sub-part 54 is approximately 3μm to 4μm. That is, after the solder overflowing from the second opening P2 is soldered to the third bonding pin 43, the thickness of the resulting solder layer 5 is approximately 3μm to 4μm. The second sub-part 54 (i.e., the intermetallic compound) is located between the third bonding pin 43 and the first sub-part 53, and its thickness is approximately 1μm. This structure not only further enhances the solder pull-out force of the flexible circuit board 4 and improves the soldering reliability of the bonding area 12, but also forms a dense cover on the surface of the third bonding pin 43 through the intermetallic compound layer 52, effectively preventing surface oxidation of the third bonding pin 43 during long-term use or reliability testing, thereby ensuring the long-term stability of the electrical connection.

[0103] In some embodiments, see Figure 4 Multiple third bonding pins 43 are arranged in a direction parallel to the substrate 1; each third bonding pin 43 has a second opening P2; the second openings P2 on two adjacent third bonding pins 43 are staggered in the orthographic projection of the reference plane; the reference plane is perpendicular to the substrate 1 and perpendicular to the arrangement direction of the multiple third bonding pins 43 (i.e., the first direction X).

[0104] As described above, the second opening P2 sequentially penetrates the second bonding pin 42, the flexible substrate 41, and the third bonding pin 43. After excess solder fills the second opening P2, it overflows onto the surface of the third bonding pin 43 and is soldered to it. By staggering the second openings P2 on adjacent third bonding pins 43 in the orthographic projection of a reference plane perpendicular to the arrangement direction, the solder overflowing from the second opening P2 forms a misalignment between adjacent third bonding pins 43. This avoids bridging and short circuits between adjacent third bonding pins 43 due to excessive solder overflow, further reducing the risk of solder bridging. At the same time, it ensures sufficient connection between each third bonding pin 43 and the solder layer 5, improving the soldering reliability of the flexible circuit board 4.

[0105] In some embodiments, the backlight module 100 further includes a wiring layer 6 and a solder mask layer 7. The wiring layer 6 is disposed on the substrate 1, and a portion of the wiring layer 6 forms a first bonding pin 3.

[0106] For example, the wiring layer 6 can be a copper layer, which forms the required circuit pattern through processes such as etching. Some of the patterned areas serve as first bonding pins 3 for bonding and connection with the flexible circuit board 4, or some of the pattern located in the main body area 11 is used to achieve electrical connection with the light-emitting chip 2.

[0107] In this embodiment, see Figure 2 , Figure 3 and Figure 4The solder mask layer 7 is stacked on the side of the trace layer 6 away from the substrate 1. Because the structural details of the pin bonding section are quite complex, Figure 2 and Figure 3 The diagram only shows the solder mask layer 7 of the main body area 11, which does not mean that the bonding area 12 does not have a solder mask layer 7.

[0108] In this embodiment, see Figure 4 The solder mask layer 7 has multiple first openings W1, each first opening W1 exposing a first bonding pin 3. The multiple first openings W1 correspond one-to-one with the multiple first bonding pins 3, and adjacent first openings W1 are spaced apart.

[0109] For example, the solder mask layer 7 can be white oil (i.e. solder mask ink), which covers the surface of the trace layer 6 and forms a first opening W1 by opening a window to expose the first bonding pin 3 to be soldered. The adjacent first bonding pins 3 are separated by white oil, which plays an insulating protection role and prevents short circuits from occurring during soldering.

[0110] For example, the distance between the boundary of the first opening W1 and the boundary of the first bonding pin 3 in a direction parallel to the substrate 1 is greater than or equal to 0.03 mm, to ensure that the first bonding pin 3 is fully exposed, while avoiding an excessively large opening that would cause adjacent first bonding pins 3 to be too close together, thus increasing the risk of solder bridging. It is worth noting that this size is relatively small, currently... Figure 4 Although not explicitly shown in the diagram, this spacing is an objective reality in the actual structure, ensuring the welding reliability of the welding area.

[0111] In some embodiments, see Figure 4 The backlight module 100 also includes a plurality of first identification units 81 and a plurality of second identification units 82.

[0112] In this configuration, a plurality of first identification portions 81 are disposed on the substrate 1, surrounding the area where a plurality of first bonding pins 3 are located, with at least two of the first identification portions 81 located diagonally opposite each other in the area where the plurality of first bonding pins 3 are located. A plurality of second identification portions 82 are disposed on the flexible substrate 41, surrounding the area where a plurality of second bonding pins 42 are located, and are stacked in a one-to-one correspondence with the plurality of first identification portions 81. The plurality of first identification portions 81 and the plurality of second identification portions 82 are configured to be aligned with each other such that the plurality of first bonding pins 3 and the plurality of second bonding pins 42 are stacked in a one-to-one correspondence.

[0113] Specifically, the orthographic projection of the first identification part 81 on the substrate 1 overlaps with the orthographic projection of the second identification part 82 on the substrate 1; in the direction parallel to the substrate 1, the size of the second identification part 82 is larger than the size of the first identification part 81.

[0114] For example, see Figure 4 , Figure 4 This is a planar unfolded view of the substrate 1 and the flexible circuit board 4 before bonding. Rectangular identification portions are provided at the lower left and upper right corners of both boards. Specifically, the first identification portion 81 is a rectangular pattern of 0.1mm × 0.1mm, and the second identification portion 82 is a rectangular pattern of 0.3mm × 0.3mm.

[0115] For example, the first identification part 81 can be a Cu pad, that is, a metal identification mark formed by patterning a copper layer, which has high reflectivity and identification contrast. The second identification part 82 can be a hollow structure or made of a visible material, which facilitates the capture and alignment by an optical identification system during the bonding process.

[0116] For example, when the offset of the geometric center of the first identification part 81 relative to the geometric center of the corresponding second identification part 82 is less than or equal to one-third of the dimension of the first identification part 81 in the direction parallel to the substrate 1 (first direction X or second direction Y), it can be proven that the alignment accuracy between the first bonding pin 3 and the second bonding pin 42 meets the welding requirements, ensuring that the two can be accurately stacked and achieve a reliable electrical connection.

[0117] This embodiment can use two marking parts to detect the alignment accuracy of the first bonding pin 3 and the second bonding pin 42 before soldering, and can make repeated adjustments to the attachment of the flexible circuit board 4 in a timely manner; in addition, the first identification part 81 and the second identification part 82 can be obtained by the substrate 1 and the flexible circuit board 4 themselves, without the need to add additional materials or process steps.

[0118] For example, without damaging other structures of the substrate 1, the solder resist layer 7 or solder resist ink / coating material at the location of the first identification part 81 can be scraped off to expose the internal copper layer as the first identification part 81; or, at the location of the second identification part 82, the flexible substrate 41 can be perforated or scraped off to form a light-transmitting or identifiable marking structure in that area. This ensures the reliability of the alignment detection before bonding while avoiding the cost burden and increased process complexity brought about by adding new materials, thereby effectively improving the overall process efficiency and soldering yield while ensuring accurate alignment of the first bonding pin 3 and the second bonding pin 42.

[0119] In some embodiments, the material of the second identification part 82 is a transparent material, for example, transparent resin. Using a transparent material for the second identification part 82 allows the optical identification system to directly capture the underlying first identification part 81 through the second identification part 82 during bonding alignment, achieving more intuitive and accurate alignment detection. This method avoids alignment deviations caused by structural obstruction or light refraction between identification parts, effectively improving the alignment accuracy of the first bonding pin 3 and the second bonding pin 42. Simultaneously, the transparent resin material has good adhesion to the flexible substrate 41, further improving the convenience and reliability of bonding alignment while ensuring the structural integrity of the flexible circuit board 4, thus providing a more accurate alignment basis for subsequent soldering processes.

[0120] Figure 9 This is a flowchart illustrating a method for fabricating a backlight module 100 provided in an embodiment of this application.

[0121] This application also provides a method for manufacturing a backlight module 100, see below. Figure 9 The preparation method includes steps S1 to S3: S1: Apply welding material to the lamp panel 10.

[0122] Among them, see Figure 2 and Figure 3 The lamp board 10 includes a substrate 1 and a plurality of first bonding pins 3. The substrate 1 has a main body region 11 and a bonding region 12 located on one side of the main body region 11. The main body region 11 of the substrate 1 is configured to carry a plurality of light-emitting chips 2, and the spacing between two adjacent light-emitting chips 2 is less than or equal to 200 μm. The plurality of first bonding pins 3 are disposed on the substrate 1 and located within the bonding region 12. Soldering material is located on the first bonding pins 3.

[0123] S2: A flexible circuit board 4 is stacked on the bonding area 12 of the substrate 1.

[0124] Among them, see Figure 2 and Figure 3 The flexible circuit board 4 includes a flexible substrate 41 and a plurality of second bonding pins 42 disposed on the flexible substrate 41. The portion of the flexible substrate 41 with the plurality of second bonding pins 42 is stacked with the bonding area 12 of the substrate 1, and the surface A of the flexible substrate 41 with the plurality of second bonding pins 42 is close to the surface B of the substrate 1 with the plurality of first bonding pins 3. The plurality of second bonding pins 42 and the plurality of first bonding pins 3 correspond one-to-one and are stacked.

[0125] S3: Welding process is used to treat the welding materials to form a weld layer 5.

[0126] Among them, see Figure 2 and Figure 3The second bonding pin 42 is electrically connected to the first bonding pin 3 through the solder layer 5; the thickness of the solder layer 5 is less than or equal to 30 μm; the thickness is the dimension of the solder layer 5 in the direction perpendicular to the substrate 1 (and the third direction Z).

[0127] In the preparation method provided in this application embodiment, by simultaneously mounting the light-emitting chip 2 and bonding it to the flexible circuit board 4 in a single reflow soldering process, a dense solder layer 5 with a thickness of less than or equal to 30 μm can be formed in a single soldering process, simplifying the process flow. This method uses metal soldering instead of ACF adhesive bonding, which can achieve higher connection reliability and electrical stability, effectively avoiding reliability problems such as unstable contact resistance, incomplete connection, or delamination caused by poor curing of ACF adhesive, thereby improving production efficiency and product yield.

[0128] Figures 10-13 Another flowchart of the preparation method of the backlight module 100 provided in the embodiments of this application.

[0129] In some embodiments, see Figure 10 The preparation method also includes: S1': Set a second welding material in the main body area 11.

[0130] S2': Multiple light-emitting chips 2 are set in the main body area 11.

[0131] The second welding material is located between the light-emitting chip 2 and the substrate 1.

[0132] S3': The second welding layer is formed by processing the second welding material using a welding process.

[0133] The light-emitting chip 2 and the substrate 1 are electrically connected through a second bonding layer. That is, the second bonding layer not only mechanically fixes the light-emitting chip 2 to the substrate 1, but also conducts electricity between the electrodes of the light-emitting chip 2 and the wiring layer 6 on the substrate 1, thereby providing driving signals and power to the light-emitting chip 2.

[0134] In this embodiment, the formation of the welding layer 5 (the welding structure of the bonding area 12) and the formation of the second welding layer (the welding structure of the main body area 11) are carried out simultaneously, that is, steps S3 and S3' are completed simultaneously using the same welding process.

[0135] For example, the above-mentioned synchronous process can also be that the solder application in steps S1 and S1' is synchronized, that is, while applying solder paste between the first bonding pin 3 of the bonding area 12 and the second bonding pin 42 of the flexible circuit board 4, solder paste is also applied at the mounting position of the light-emitting chip 2 in the main body area 11, and both share the same reflow soldering process. Alternatively, by way of example, secondly, the alignment synchronization in steps S2 and S2', that is, the second bonding pin 42 of the flexible circuit board 4 is aligned and attached to the first bonding pin 3 of the substrate 1 in advance, and the light-emitting chip 2 is aligned and attached to the corresponding position of the main body area 11, and then the two are sent together to the reflow soldering equipment for one soldering.

[0136] This embodiment pre-aligns and attaches the second bonding pin 42 of the flexible circuit board 4 with the first bonding pin 3 of the substrate 1, and then performs a reflow soldering process together with the light-emitting chip 2. This process can maintain good fluidity and wettability of the solder during reflow, thereby effectively improving the welding quality and ultimately enhancing the welding strength and overall reliability between the flexible circuit board 4 and the substrate 1.

[0137] In some embodiments, the alignment synchronization in steps S2 and S2' is specifically performed by an identification machine or a pick-and-place machine with identification function to complete the alignment and placement. In the bonding area 12, the identification machine (or the image acquisition unit of the pick-and-place machine) identifies multiple first bonding pins 3 on the substrate 1 and multiple second bonding pins 42 on the flexible circuit board 4, matches the relative positions of the first bonding pins 3 and the second bonding pins 42 according to the identification results, and adjusts the position of the flexible circuit board 4 so that the multiple first bonding pins 3 and the multiple second bonding pins 42 are aligned one by one. Then, the pick-and-place machine is used to attach the aligned flexible circuit board 4 to the bonding area 12 of the substrate 1.

[0138] Furthermore, in the main body area 11, the same identification machine (or the image acquisition unit of the pick-and-place machine) identifies the target mounting position and the pin position of the light-emitting chip 2 within the main body area 11 of the substrate 1, and uses the pick-and-place machine to attach the light-emitting chip 2 to the corresponding pad in the main body area 11. In this manner, the same pick-and-place machine sequentially or alternately completes the alignment and mounting of the flexible circuit board 4 and the mounting of the light-emitting chip 2, realizing the synchronous reuse of the alignment process. This ensures the mounting accuracy of the two components while reducing equipment investment and process flow, thus improving the overall process efficiency.

[0139] In some embodiments, see Figure 4 As described above, the lamp board 10 also includes a plurality of first identification parts 81, which are disposed on the substrate 1 and arranged around the area where the plurality of first bonding pins 3 are located. At least two of the plurality of first identification parts 81 are located diagonally opposite to the area where the plurality of first bonding pins 3 are located. The flexible circuit board 4 also includes a plurality of second identification parts 82, which are disposed on the flexible substrate 41 and arranged around the area where the plurality of second bonding pins 42 are located. At least two of the plurality of second identification parts 82 are located diagonally opposite to the area where the plurality of second bonding pins 42 are located.

[0140] Among them, see Figure 11Step S2: Laminating the flexible circuit board 4 on the bonding area 12 of the substrate 1 includes steps S21 to S22: S21: Identify the positions of the first identification unit 81 and the second identification unit 82.

[0141] Specifically, the image acquisition unit built into the pick-and-place machine is used to capture the position information of the first identification part 81 on the periphery of the bonding area 12 on the substrate 1 and the corresponding second identification part 82 on the flexible circuit board 4.

[0142] S22: Based on the positions of the multiple first identification parts 81 and the multiple second identification parts 82, the flexible circuit board 4 is attached to the bonding area 12.

[0143] In this configuration, multiple first identification units 81 and multiple second identification units 82 are aligned one-to-one, so that multiple first binding pins 3 and multiple second binding pins 42 are aligned one-to-one and stacked.

[0144] Specifically, after identification, the pick-and-place machine calculates the offset of the geometric center of the first identification part 81 relative to the geometric center of the corresponding second identification part 82 based on the identification result. When this offset is greater than a preset threshold (i.e., one-third of the dimension of the first identification part 81 in the direction parallel to the substrate 1), it indicates insufficient alignment accuracy. The pick-and-place machine promptly adjusts the position of the flexible circuit board 4 until the offset meets the requirements, and then attaches the flexible circuit board 4 to the bonding area 12. This adjustment process is completed before reflow soldering, allowing for rework of the attachment of the flexible circuit board 4, thereby avoiding poor soldering due to alignment deviation, improving alignment accuracy and soldering quality, and ultimately enhancing the soldering strength between the flexible circuit board 4 and the substrate 1 and the overall process reliability.

[0145] It is worth noting that the identification and attachment processes of the first identification unit 81 and the second identification unit 82 reuse the aforementioned identification and attachment equipment for the light-emitting chip 2. That is, the same attachment equipment is used not only to complete the alignment and attachment of the flexible circuit board 4 and the identification and attachment of the light-emitting chip 2, but also to check and inspect the alignment of the flexible circuit board 4 and make adjustments. By reusing equipment, the investment in production line equipment and process flow can be reduced, and alignment errors introduced by differences in positioning references between different equipment can be avoided, further improving overall attachment accuracy and process efficiency.

[0146] In some embodiments, see Figure 4 The material of the second identification part 82 is transparent, and the dimensions of the second identification part 82 in the direction parallel to the substrate 1 are all larger than the dimensions of the first identification part 81 in the direction parallel to the substrate 1.

[0147] Among them, see Figure 12After step S2: laminating the flexible circuit board 4 on the bonding area 12 of the substrate 1, and before step S3: processing the welding material using a welding process to form the welding layer 5, steps S301 to S302 are also included: S301: Obtain the offset of the geometric center of the first recognition unit 81 relative to the geometric center of the corresponding second recognition unit 82.

[0148] Specifically, since the second recognition unit 82 is made of transparent material and is larger than the first recognition unit 81, the optical recognition system can clearly capture the outline of the lower first recognition unit 81 through the second recognition unit 82, calculate the geometric center position of the two respectively through the image processing algorithm, and then obtain the offset.

[0149] S302: Adjust the position of flexible circuit board 4 based on the offset being greater than the preset threshold.

[0150] The preset threshold is one-third of the size of the first identification part 81 in the direction parallel to the substrate 1.

[0151] If the offset exceeds the threshold, it indicates that the alignment accuracy between the first bonding pin 3 and the second bonding pin 42 is insufficient. At this time, the position of the flexible circuit board 4 can be finely adjusted by a pick-and-place machine or alignment platform until the offset meets the requirements.

[0152] Through the above steps, this embodiment can detect and rework the alignment status of the second bonding pin 42 and the first bonding pin 3 before reflow soldering, avoiding poor soldering due to alignment deviations entering the soldering process. Since the adjustment operation is completed before soldering, it does not need to destroy the formed solder structure, ensuring the feasibility of rework and effectively improving the alignment accuracy and soldering quality, ultimately enhancing the soldering strength between the flexible circuit board 4 and the substrate 1 and the overall process reliability.

[0153] Figure 15 This is a physical image of a cover plate 92 attached to a substrate 1, as provided in an embodiment of this application.

[0154] Figure 16 This is a top view of the cover plate 92 attached to the substrate 1 in an embodiment of this application.

[0155] In some embodiments, see Figure 13 Step S1: Before applying welding material to the lamp board 10, the following steps are also included: S10: See also Figure 2 Place the substrate 1 on the base 91.

[0156] For example, the base 91 can be a support platform or carrier base plate for fixing the lamp panel 10 and providing support.

[0157] See Figure 15After step S2 (laminating the flexible circuit board 4 on the bonding area 12 of the substrate 1) and before step S3 (processing the welding material using a welding process to form the welding layer 5), the following is also included: Step S220: See Figure 2 A cover sheet 92 is stacked on the side of the lamp board 10 and the flexible circuit board 4 away from the base 91.

[0158] Among them, see Figure 2 The cover plate 92 has multiple second openings W2 and multiple third openings W3; the second openings W2 expose the light-emitting chip 2, and the third openings W3 expose the area where the first binding pin 3 and the second binding pin 42 are located; the cover plate 92 is configured to fix the lamp board 10 and the flexible circuit board 4 between the base 91 and the cover plate 92.

[0159] For example, the cover 92 can be configured as a full-coverage structure, covering the entire area above the lamp board 10 and the flexible circuit board 4.

[0160] For example, the cover plate 92 and the base 91 can be combined to form a carrier. The cover plate 92 and the base 91 can have magnetic attraction, for example, by using a built-in magnet or magnetic material to achieve mutual attraction and fixation; other methods such as snap-fit ​​or locking can also be used for fixation. Through the cooperation of the cover plate 92 and the base 91, the lamp board 10 and the flexible circuit board 4 can be clamped and fixed between them, preventing warping of the substrate 1 and the flexible circuit board 4 in subsequent processes, thereby ensuring the mounting accuracy of the light-emitting chip 2 and avoiding the phenomenon of increased warping of the aluminum substrate 1 after reflow soldering at high temperatures, ensuring process stability.

[0161] Specifically, see Figure 2 To avoid interference during chip assembly, the cover plate 92 has a second opening W2 (i.e., a through-hole) at the chip assembly location, exposing the light-emitting chip 2 within the second opening W2. This prevents the cover plate 92 from directly contacting the light-emitting chip 2 and causing damage or positional displacement. Simultaneously, a third opening W3 is formed above the bonding area 12, exposing the area containing the first bonding pin 3 and the second bonding pin 42. This prevents the cover plate 92 from directly pressing against this area, causing solder paste to overflow and potentially leading to short circuits between adjacent pins. For non-soldering areas such as the PI layer and solder mask area between the second bonding pin 42 and the flexible substrate 41, the cover plate 92 presses and fixes them to the base 91.

[0162] During the reflow soldering process, the solder paste exhibits certain thixotropic and viscous properties after being heated. Its viscosity will cause the second bonding pin 42 to adhere to the first bonding pin 3. At the same time, the cover plate 92 presses and fixes the large non-soldering area of ​​the flexible circuit board 4, effectively preventing the flexible circuit board 4 from shifting due to the reflow air in the reflow oven, thereby ensuring soldering accuracy and reliability.

[0163] Figure 17Another flowchart of the preparation method of the backlight module 100 provided in the embodiments of this application.

[0164] For example, see Figure 17 To illustrate the implementation of the above process in detail, the following is an embodiment involving specific preparation steps of the backlight module 100.

[0165] like Figure 17 As shown, during the solder paste printing stage, solder paste is printed together on the pads of the light-emitting chips 2 (including LEDs and ICs) on the same side of the first bonding pin 3. Then, the solder paste printing quality is inspected using an SPI (Solder Solder Paste Thickness Gauge) to ensure that the solder paste thickness and molding meet the process requirements. The second bonding pin 42 is aligned and attached to the bonding area 12 of the substrate 1, and then a cover plate 92 is used to press the substrate 1 and the flexible circuit board 4. This cover plate 92 can fix the substrate 1 to ensure subsequent component assembly accuracy and prevent the substrate 1 from warping due to high temperatures in the reflow oven. On the other hand, the cover plate 92 can fix and press the flexible circuit board 4 to prevent it from shifting during reflow. Next, die bonding is performed, and the light-emitting chips 2 and other components are mounted on the corresponding pad positions in the main body area 11. Then, the reflow soldering process is completed in one pass. After soldering, cooling is performed, and the soldering quality is inspected by AOI (Automated Optical Inspection). Finally, the source line connection status and lighting function are confirmed to ensure that the electrical performance of the backlight module 100 meets the requirements.

[0166] The above process integrates the bonding process between the flexible circuit board 4 and the substrate 1 into the SMT (Surface Mount Technology) process segment. This process segment was originally used to complete the solder paste application, placement, and reflow soldering of the light-emitting chip 2 (including LEDs, ICs, and other components). In this embodiment, the bonding of the flexible circuit board 4 and the placement of the light-emitting chip 2 are performed simultaneously. That is, after the second bonding pin 42 of the flexible circuit board 4 is aligned and bonded to the first bonding pin 3 of the substrate 1, it is placed together with the already placed light-emitting chip 2 in the reflow oven for one-time soldering.

[0167] This integrated process effectively avoids the problem of poor ACF curing caused by excessive heat dissipation in ACF (Anisotropic Conductive Adhesive) bonding of high thermal conductivity aluminum substrates. Furthermore, the reflow soldering process forms the solder layer 5 through uniform heating, making it insensitive to substrate heat dissipation. Secondly, compared to the Hot bar (thermo-press soldering) method, which requires an additional thermo-press bonding and secondary melting soldering after chip mounting, this embodiment combines the two soldering processes into one, significantly reducing the risk of thermal stress damage and soldering defects at the solder interface caused by secondary heating. Regardless of the substrate 1 or soldering material used, this process eliminates a separate bonding step, thereby improving production efficiency and soldering yield, reducing equipment investment, and effectively lowering production costs.

[0168] Figure 18 This is a physical image of the flexible circuit board 4 after reflow soldering, as provided in the embodiments of this application.

[0169] Figure 19 An X-ray confirmation image of the welding state of the flexible circuit board 4 provided in an embodiment of this application.

[0170] For example, by integrating the bonding process between the flexible circuit board 4 and the substrate 1 into the SMT (Surface Mount Technology) process segment through the above embodiments, the resulting welding result is as follows: Figure 5 , Figure 18 , Figure 19 As shown. See also Figure 5 The second bonding pin 42 is connected to the first bonding pin 3 by a solder layer 5, and there are no obvious severe voids visible within the solder layer 5. (See reference...) Figure 18 After the flexible circuit board 4 is soldered in one reflow soldering cycle, excess solder can be effectively discharged through the solder vents (such as the first opening P1 or the second opening P2) during the melting process, preventing solder buildup. Simultaneously, the flexible circuit board 4 material itself has good temperature resistance and can withstand the peak temperature of the reflow oven (240℃~260℃). After reflow soldering, it was confirmed that the flexible circuit board 4 has no obvious wrinkles or defects. (See reference...) Figure 19 X-ray inspection confirmed that the soldering condition was good, with no obvious solder bridging or short circuits, and the void ratio of solder layer 5 met the process requirements. This indicates that the above embodiment can achieve stable and reliable soldering quality in a single reflow soldering process.

[0171] Figure 20 This is a comparison diagram of the solder paste state before soldering provided in an embodiment of this application.

[0172] For example, Figure 20 (a) is the printed solder paste required for soldering in this embodiment, which has a uniform and delicate surface and good fluidity; Figure 20 (b) is the solder paste used in the Hot bar scheme before the flexible circuit board 4 is soldered to the substrate 1. The solder paste has been reflowed during the SMT process stage when the light-emitting chip 2 is mounted, and the solder paste has been completely shaped and lost its fluidity.

[0173] Understandably, the fluid solder paste used in this solution helps to fully wet the interface between the first bonding pin 3 and the second bonding pin 42 during a single reflow soldering process, promoting the full growth of the intermetallic compound layer 52, thereby forming a dense and thickness-controllable solder layer 5. It also enables the obtaining of a solder structure with a higher proportion of intermetallic compound layer 52 and higher soldering reliability, effectively improving the connection reliability of the bonding area 12.

[0174] Figure 21This is a schematic diagram of a display device 1000 provided in an embodiment of this application.

[0175] This application also provides a display device 1000, see reference. Figure 21 The display device 1000 includes a display panel 200 and a backlight module 100. The display panel 200 is disposed on the light-emitting side of the backlight module 100.

[0176] That is, the display panel 200 can be stacked on the side surface of the backlight module 100 where the light-emitting chip 2 is disposed. The light emitted by the backlight module 100 is incident on the display panel 200 and forms an image after being modulated by the display panel 200.

[0177] For example, a reflective layer is also provided between the display panel 200 and the backlight module 100. The reflective layer may be ink or a reflective sheet, which is used to reflect part of the light to the display panel 200, thereby reducing light loss, improving the overall light output brightness, and thus improving the display quality of the display panel 200.

[0178] For example, see Figure 1 The display device 1000 may also include a PCB (printed circuit board), which can be bonded to the other end of the flexible circuit board 4 to provide drive signals and power to the flexible circuit board 4, and then transmit them to the light-emitting chip 2 on the substrate 1 through the solder layer 5 of the first bonding pin 3 and the second bonding pin 42.

[0179] Simultaneously, the PCB can also be electrically connected to the driving circuit (such as the source driver chip or gate driver circuit) of the display panel 200, thereby providing display driving signals to the display panel 200. Through the above connection method, the PCB, as a centralized signal and power distribution unit, realizes unified driving control of the backlight module 100 and the display panel 200, which helps to simplify the wiring structure of the display device 1000 and improve the integration and reliability of electrical connections.

[0180] For example, the display device 1000 can be a consumer electronics product, an in-vehicle electronic product, or any other device that requires a display function. Consumer electronics products include mobile phones, tablets, laptops, e-readers, personal computers (PCs), personal digital assistants (PDAs), desktop monitors, smart wearable products (e.g., smartwatches, smart bracelets), virtual reality (VR) terminal devices, and augmented reality (AR) terminal devices. In-vehicle electronic products include in-vehicle navigation systems and in-vehicle display terminals.

[0181] It is understood that the features and effects of each component in the backlight module 100 can be referred to the description of each component and corresponding effects of the backlight module 100 in any of the foregoing embodiments, and will not be repeated here.

[0182] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A backlight module, characterized in that, include: The substrate has a main body region and a bonding region located on one side of the main body region; Multiple light-emitting chips are arrayed on the substrate and located within the main body area; The spacing between two adjacent light-emitting chips is less than or equal to 200μm; Multiple first bonding pins are disposed on the substrate and located within the bonding area; A flexible circuit board includes a flexible substrate and a plurality of second bonding pins disposed on the flexible substrate. The portion of the flexible substrate with the plurality of second bonding pins is stacked with a bonding area of ​​the substrate, and the surface of the flexible substrate with the plurality of second bonding pins is close to the surface of the substrate with the plurality of first bonding pins. A solder layer is at least partially located between the flexible circuit board and the substrate; the second bonding pin is electrically connected to the first bonding pin through the solder layer; Wherein, the thickness of the welding layer is less than or equal to 30 μm; the thickness is the dimension of the welding layer in the direction perpendicular to the substrate.

2. The backlight module according to claim 1, characterized in that, The solder layer includes a bonding layer and two intermetallic compound layers, the two intermetallic compound layers being located between the first bonding pin and the bonding layer, and between the second bonding pin and the bonding layer, respectively. Each of the intermetallic compound layers has a dimension in the direction perpendicular to the substrate that is at least 10% of the thickness of the solder layer.

3. The backlight module according to claim 1, characterized in that, The substrate includes a first sublayer and a second sublayer, the first sublayer being conductive and the second sublayer being electrically insulating, and the first bonding pin being disposed on the side of the second sublayer away from the first sublayer.

4. The backlight module according to claim 1, characterized in that, The flexible circuit board has a first opening that penetrates the second bonding pin; at least a portion of the solder layer is also filled in the first opening.

5. The backlight module according to claim 1, characterized in that, The flexible circuit board also includes a plurality of third bonding pins, which correspond one-to-one with the plurality of second bonding pins and are stacked on top of each other, and the third bonding pins and the second bonding pins are respectively located on both sides of the flexible substrate; The flexible circuit board has a second opening that passes through the second bonding pin, the flexible substrate, and the third bonding pin in sequence; at least a portion of the solder layer is also filled in the second opening.

6. The backlight module according to claim 5, characterized in that, At least a portion of the solder layer is also located on the surface of the third bonding pin, which has the second opening, away from the second bonding pin.

7. The backlight module according to claim 6, characterized in that, The portion of the solder layer located on the surface of the third bonding pin away from the second bonding pin further includes a first sub-part and a second sub-part; the second sub-part is located between the third bonding pin and the first sub-part, and the second sub-part is an intermetallic compound.

8. The backlight module according to claim 5, characterized in that, The plurality of third bonding pins are arranged in a direction parallel to the substrate; each of the third bonding pins has a second opening; the second openings on two adjacent third bonding pins are staggered in the orthographic projection of the reference plane; the reference plane is perpendicular to the substrate and perpendicular to the arrangement direction of the plurality of third bonding pins.

9. The backlight module according to claim 1, characterized in that, Also includes: A wiring layer is disposed on the substrate, and a portion of the wiring layer forms the first bonding pin; A solder mask layer is stacked on the side of the trace layer away from the substrate. The solder mask layer has a plurality of first openings, each of which exposes a first bonding pin. The plurality of first openings correspond one-to-one with the plurality of first bonding pins, and adjacent first openings are spaced apart.

10. The backlight module according to claim 1, characterized in that, Also includes: A plurality of first identification portions are disposed on the substrate, the plurality of first identification portions being disposed around the region where the plurality of first bonding pins are located, and at least two of the plurality of first identification portions are respectively located diagonally opposite to the region where the plurality of first bonding pins are located; Multiple second identification parts are disposed on the flexible substrate, the multiple second identification parts are disposed around the area where the multiple second bonding pins are located, and are stacked one-to-one with the multiple first identification parts; the material of the second identification parts is a transparent material; The plurality of first identification parts and the plurality of second identification parts are configured to be aligned with each other such that the plurality of first binding pins and the plurality of second binding pins correspond one-to-one and are stacked.

11. A method for manufacturing a backlight module, characterized in that, include: A welding material is provided on the lamp board; the lamp board includes a substrate and a plurality of first bonding pins, the substrate having a main body area and a bonding area located on one side of the main body area; The main area of ​​the substrate is configured to carry a plurality of light-emitting chips, the spacing between two adjacent light-emitting chips being less than or equal to 200 μm; the plurality of first bonding pins are disposed on the substrate and located within the bonding area; The welding material is located on the first bonding pin; A flexible circuit board is stacked on the bonding area of ​​the substrate; the flexible circuit board includes a flexible substrate and a plurality of second bonding pins disposed on the flexible substrate, the portion of the flexible substrate having the plurality of second bonding pins is stacked with the bonding area of ​​the substrate, and the surface of the flexible substrate having the plurality of second bonding pins is close to the surface of the substrate having the plurality of first bonding pins; the plurality of second bonding pins correspond one-to-one with the plurality of first bonding pins and are stacked; The welding material is processed using a welding process to form a welding layer; the second bonding pin and the first bonding pin are electrically connected through the welding layer; the thickness of the welding layer is less than or equal to 30 μm; the thickness is the dimension of the welding layer in the direction perpendicular to the substrate.

12. The preparation method according to claim 11, characterized in that, Also includes: A second welding material is applied to the main body area; The plurality of light-emitting chips are disposed in the main body area; The second welding material is located between the light-emitting chip and the substrate; The second welding material is processed using a welding process to form a second welding layer; the light-emitting chip and the substrate are electrically connected through the second welding layer. The formation of the first welding layer and the formation of the second welding layer are carried out simultaneously.

13. The preparation method according to claim 12, characterized in that, The lamp board further includes a plurality of first identification portions disposed on the substrate and surrounding the area where the plurality of first bonding pins are located, with at least two of the plurality of first identification portions located diagonally opposite to the area where the plurality of first bonding pins are located; the flexible circuit board further includes a plurality of second identification portions disposed on the flexible substrate and surrounding the area where the plurality of second bonding pins are located, with at least two of the plurality of second identification portions located diagonally opposite to the area where the plurality of second bonding pins are located; The flexible circuit board laminated on the bonding area of ​​the substrate includes: Identify the positions of the first identification unit and the second identification unit; Based on the positions of the plurality of first identification parts and the plurality of second identification parts, the flexible circuit board is attached to the bonding area; the plurality of first identification parts and the plurality of second identification parts are aligned one-to-one, so that the plurality of first bonding pins and the plurality of second bonding pins correspond one-to-one and are stacked.

14. The preparation method according to claim 13, characterized in that, The material of the second identification part is transparent, and the dimensions of the second identification part in the direction parallel to the substrate are all larger than the dimensions of the first identification part in the direction parallel to the substrate. Wherein, after the flexible circuit board is stacked on the bonding area of ​​the substrate, and before the welding process is used to form the welding layer with the welding material, the method further includes: Obtain the offset of the geometric center of the first recognition unit relative to the geometric center of the corresponding second recognition unit; Based on the offset being greater than a preset threshold, the position of the flexible circuit board is adjusted; the preset threshold is one-third of the size of the first identification part in the direction parallel to the substrate.

15. The preparation method according to claim 11, characterized in that, Before applying the welding material to the lamp panel, the process also includes: Place the substrate on the base; After the flexible circuit board is stacked on the bonding area of ​​the substrate, and before the welding process is used to form the welding layer with the welding material, the method further includes: A cover sheet is stacked on the side of the lamp board and the flexible circuit board away from the base; the cover sheet has a plurality of second openings and a plurality of third openings; the second openings expose the light-emitting chip, and the third openings expose the areas where the first bonding pin and the second bonding pin are located; the cover sheet is configured to fix the lamp board and the flexible circuit board between the base and the cover sheet.

16. A display device, characterized in that, include: The backlight module as described in any one of claims 1 to 10; The display panel is located on the light-emitting side of the backlight module.

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