Circuit board, preparation method thereof and backlight module

Abstract

The invention provides a circuit board and a preparation method thereof and a backlight module, the circuit board comprises a circuit substrate and a reflection structure layer located on at least one surface of the circuit substrate, the reflection structure layer covers at least part of a circuit layer of the circuit substrate, and the reflection structure layer comprises a reflection layer and a transparent photosensitive layer which are sequentially stacked on the surface of the circuit substrate. The transparent photosensitive layer covers the outer surface of the reflecting layer. According to the circuit board provided by the invention, the surface of the reflecting layer is coated with the transparent photosensitive layer, so that the thickness and flatness of the reflecting structure layer can be improved, the light loss is reduced, the reflectivity and uniformity are improved, the lateral erosion size of the bottom of the reflecting layer is reduced, and the risk that the reflecting layer falls off is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of backlight sources, in particular to a circuit board, a preparation method thereof and a backlight module. BACKGROUND

[0002] Mini LED backlight technology changes the side-in backlight to direct backlight, and arranges Mini LEDs on the whole surface to form a surface light source, so that the panel can accommodate more lamp beads under the condition of keeping the area unchanged, thereby realizing high-brightness display effect. In addition, the Mini LED backlight technology can realize independent control of multiple groups of lamp beads, and can flexibly adjust the brightness. Therefore, the Mini LED backlight technology is widely used in display devices such as mobile phones, televisions and computers, and has good application prospect.

[0003] However, the existing Mini LED backlight source has low reflectivity, high light loss, uneven reflection, and the solder mask layer is easy to fall off, and the like, which needs to be improved. SUMMARY

[0004] In view of this, in order to solve at least one of the above problems, it is necessary for the present application to provide a circuit board for Mini LED backlight module, which can improve the reflectivity and uniformity of the light source, reduce light loss, and the like.

[0005] In addition, it is also necessary for the present application to provide a preparation method of the foregoing circuit board and a backlight module using the foregoing circuit board.

[0006] The present application provides a circuit board, which comprises: a circuit substrate and a reflection structure layer, the circuit substrate comprises a base layer and a circuit layer arranged on at least one surface of the base layer, and the reflection structure layer is arranged on the surface of the base layer and covers at least part of the circuit layer, the reflection structure layer comprises a reflection layer and a transparent photosensitive layer arranged on the surface of the circuit substrate in sequence, and the transparent photosensitive layer covers the outer surface of the reflection layer.

[0007] In some possible embodiments, the side etching size of the reflection layer is less than or equal to 12.8 μm along the extension direction of the circuit board.

[0008] In some possible embodiments, the transparent photosensitive layer comprises an inner layer close to the reflection layer and an outer layer on the surface of the inner layer away from the reflection layer, the inner layer and the outer layer are an integral structure, and the refractive index of the outer layer is greater than that of the inner layer.

[0009] In some possible embodiments, the reflective layer is formed by curing a dry film or a wet film, the dry film or the wet film is white ink, the thickness of the reflective layer formed by the dry film is 30-60 μm, and the thickness of the reflective layer formed by the wet film is 22-45 μm; and the transparent photosensitive layer is formed by curing transparent photosensitive resin, and the thickness of the transparent photosensitive layer is 25-35 μm.

[0010] In some possible embodiments, when the reflective structure layer comprises the reflective layer formed by the dry film, the reflectivity of the reflective structure layer is greater than or equal to 93%; and when the reflective structure layer comprises the reflective layer formed by the wet film, the reflectivity of the reflective structure layer is greater than or equal to 87%.

[0011] In some possible embodiments, the circuit layer comprises a connection pad, the reflective structure layer is provided with an opening corresponding to the connection pad, part of the connection pad is exposed by the opening, and the circuit board further comprises an electronic component, the electronic component is located in the opening and electrically connected to the connection pad.

[0012] The embodiments of the present application further provide a preparation method of a circuit board, which comprises the following steps:

[0013] forming an ink layer on at least one surface of a circuit substrate;

[0014] forming a transparent photosensitive resin layer on the surface of the ink layer; and

[0015] curing the ink layer by irradiation to form a reflective layer, and curing the transparent photosensitive resin layer to form a transparent photosensitive layer covering the outer surface of the reflective layer, the transparent photosensitive layer and the reflective layer constituting a reflective structure layer, so as to obtain the circuit board.

[0016] In some possible embodiments, the step of curing the ink layer by irradiation to form a reflective layer, and curing the transparent photosensitive resin layer to form a transparent photosensitive layer covering the outer surface of the reflective layer comprises the following steps:

[0017] forming a patterned film on the surface of the transparent photosensitive layer, the patterned film having a pattern region and a gap region;

[0018] providing light of a first wavelength to cure the ink layer corresponding to the gap region to form the reflective layer, the first wavelength being 440 nm and 425 nm, and providing light of a second wavelength to cure the transparent photosensitive resin layer corresponding to the gap region to form the transparent photosensitive layer, the second wavelength being 405 nm, 385 nm and 365 nm;

[0019] removing the transparent photosensitive resin layer and the ink layer corresponding to the patterned film and the graphic area to form an opening, and part of the circuit layer is exposed by the opening; and

[0020] heating the transparent photosensitive layer after forming the opening, so that the transparent photosensitive layer extends to the sidewall of the opening, thereby obtaining the circuit board.

[0021] In some possible embodiments, the step of forming the ink layer on the surface of the at least one circuit layer of the circuit substrate comprises:

[0022] printing white ink on the surface of the at least one circuit layer of the circuit substrate to form the ink layer; or

[0023] pressing the ink layer on the surface of the at least one circuit layer of the circuit substrate by pressing.

[0024] The embodiment of the present application further provides a backlight module, which comprises a backlight plate, and the backlight plate comprises the circuit board or is prepared by the preparation method of the circuit board.

[0025] Compared with the prior art, the circuit board provided by the embodiment of the present application can improve the thickness and flatness of the reflection structure layer, reduce light loss, improve reflectivity and uniformity, and thus improve the brightness of the product using the circuit board, by adopting the "big package small" mode to form the reflection structure layer with a double-layer structure, and coating the transparent photosensitive layer on the surface of the reflection layer. Meanwhile, the size of the side etching of the bottom of the reflection layer is reduced (compared with the traditional solder mask layer, the size of the side etching is reduced by at least 45%), which can improve the bonding force between the reflection layer and the circuit substrate and reduce the risk of the reflection layer being pulled off. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The structural schematic diagram of the circuit board provided by an embodiment of the present application is shown.

[0027] Figure 2 The top view of the circuit board provided by an embodiment of the present application is shown.

[0028] Figure 3 The Figure 2 The enlarged view of part A in FIG. 6 is shown.

[0029] Figure 4 The sectional view of the circuit board provided by an embodiment of the present application is shown.

[0030] Figure 5 The Figure 4 The enlarged view of part B in FIG. 6 is shown.

[0031] Figure 6This is a comparison chart of the reflectivity of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 of the present application.

[0032] Figure 7 This is a structural diagram of a backlight module provided in one embodiment of the present application.

[0033] Figure 8 A flowchart of the preparation of a circuit board provided in one embodiment of the present application.

[0034] Figure 9 Schematic diagram of the curing process of the white ink layer and the transparent photosensitive resin layer under different exposure energies provided by one embodiment of the present application.

[0035] Figures 10A to 10K A schematic structural diagram of a circuit board manufacturing process provided in one embodiment of the present application.

[0036] Description of main component symbols

[0037] Circuit board 100

[0038] Circuit board 1

[0039] Grassroots 11

[0040] First surface 111

[0041] Second surface 112

[0042] Circuit layer 12

[0043] Connection pad 13

[0044] Reflective structure layer 2

[0045] Opening 21

[0046] Reflective layer 3

[0047] Transparent photosensitive layer 4

[0048] Inner layer 41

[0049] Outer layer 42

[0050] Substrate 10

[0051] Metal layer 20

[0052] Intermediate metal layer 30

[0053] White ink layer 40

[0054] Transparent photosensitive resin layer 50

[0055] Patterned film 60

[0056] Backlight module 200

[0057] Backlight plate 201

[0058] Outer frame 202

[0059] Extension direction a

[0060] The following detailed description will further describe the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0061] The technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments.

[0062] It should be noted that when an element is referred to as being "fixed" to another element, it can be directly on the other element or there can be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there can be an intervening element. When an element is referred to as being "provided on" another element, it can be directly provided on the other element or there can be an intervening element.

[0063] Referring to Figures 1 to 3 As shown in the drawings, the embodiments of the present application provide a circuit board 100, which comprises a circuit substrate 1 and a reflective structure layer 2 located on at least one surface of the circuit substrate 1. The circuit substrate 1 comprises a base layer 11 and a circuit layer 12 provided on at least one surface of the base layer 11, and the reflective structure layer 2 is located on the surface of the base layer 11 and covers at least part of the circuit layer 12. The reflective structure layer 2 comprises a reflective layer 3 and a transparent photosensitive layer 4 which are sequentially stacked on the surface of the circuit substrate 1, and the transparent photosensitive layer 4 covers the outer surface of the reflective layer 3. That is, the transparent photosensitive layer 4 covers the outer surface of the reflective layer 3 entirely, forming a double-layered reflective structure in which a large layer covers a small layer, which can effectively improve the reflectivity of the reflective structure layer 2.

[0064] The circuit substrate 1 can be a double-sided board or a multi-layer board. In some embodiments, the circuit substrate 1 is a double-sided board.

[0065] In some embodiments, the base layer 11 comprises a first surface 111 and a second surface 112 which are oppositely arranged, and the circuit layer 12 is provided on both the first surface 111 and the second surface 112. Meanwhile, the reflective structure layer 2 is provided on both the first surface 111 and the second surface 112, and covers the circuit layer 12 on the same side.

[0066] In some embodiments, the circuit layer 12 comprises a connection pad 13, the reflective structure layer 2 is provided with an opening 21 corresponding to the connection pad 13, and part of the connection pad 13 is exposed by the opening 21. The circuit board 100 further comprises an electronic element (not shown in the figure), which is located in the opening 21 and electrically connected to the connection pad 13. Specifically, the electronic element can be an active element or a passive element, for example, when the circuit board 100 is applied to a Mini LED backlight module, the electronic element can be an LED lamp bead.

[0067] In some embodiments, the base layer 11 can be formed of a material of an insulating layer of a conventional PCB board, for example, the material of the base layer 11 can be epoxy resin, Prepreg (PP), BT resin, Polyphenylene Oxide (PPO), polyimide (PI), Polyethylene Terephthalate (PET), and Polyethylene Naphthalate (PEN), etc. It can be understood that the base layer 11 can also be a glass substrate.

[0068] In some embodiments, the material of the circuit layer 12 can be copper. The circuit layer 12 further comprises a circuit 14 electrically connected to the connection pad 13.

[0069] The reflective structure layer 2 is formed by a double-layer structure of a reflective layer 3 and a transparent photosensitive layer 4 in a "big package small" manner, the reflective layer 3 can be formed by curing a white ink layer, and the transparent photosensitive layer 4 can be formed by curing a transparent photosensitive resin, specifically, the curing can be in the form of photocuring. The transparent photosensitive layer 4 is coated on the surface of the reflective layer 3, which can effectively improve the exposure energy and the refractive frequency. In addition, the coating of the transparent photosensitive layer 4 can improve the thickness and flatness of the reflective structure layer 2, and the edge will not appear a step structure, thereby effectively improving the reflectivity of the reflective structure layer 2.

[0070] In some embodiments, the thickness of the reflective layer 3 may vary depending on the molding method. For example, the reflective layer 3 may be formed by a dry method or a wet method. The dry method is to directly press a dry film (such as a white ink layer) on the surface of the circuit substrate 1. The thickness of the reflective layer 3 formed at this time may be 30 μm to 60 μm. The wet method is to form a wet film by printing white ink on the circuit board 1. The thickness of the reflective layer 3 formed at this time may be 22 μm to 45 μm. In some embodiments, the thickness of the transparent photosensitive layer 4 may be 25 μm to 35 μm. In some embodiments, the thickness of the reflective structure layer 2 may be the sum of the thicknesses of the reflective layer 3 and the transparent photosensitive layer 4. The double-layer stacking form can effectively increase the thickness of the reflective structure layer 2 and improve the reflectivity.

[0071] In some embodiments, when forming the opening 21 on the reflective structure layer 2, a patterning process is required, and etching is usually used to remove part of the reflective structure layer 2. At this time, the etching solution will cause a side etching process on the bottom of the reflective layer 3 near the base layer 11. In traditional backlight panels, the side etching of the reflective layer is more serious, and the size of the side etching is larger, usually more than 23μm, which will affect the bonding strength between the reflective layer and the base layer, causing the reflective layer to fall off under tension. In this embodiment, Figure 4 As shown, the reflective structure layer 2 is formed by a double-layer stack of a reflective layer 3 and a transparent photosensitive layer 4, wherein the reflective layer 3 and the transparent photosensitive layer 4 are stacked in a "big-wrapped-small" manner. During the etching process of the opening 21, the side etching size L of the reflective layer 3 along the extension direction a of the circuit board 100 is relatively small and can reach below 12.8 μm, which is nearly 45% smaller than the side etching size in the traditional backlight panel.

[0072] In some embodiments, the transparent photosensitive layer 4 may include an inner layer 41 close to the reflective layer 3 and an outer layer 42 located on the surface of the inner layer 41 away from the reflective layer 3, wherein the inner layer 41 and the outer layer 42 are an integral structure, and the refractive index of the outer layer 42 is greater than that of the inner layer 41. Figure 5 As shown, due to the difference between the inner layer 41 and the outer layer 42 during the three-wavelength curing of the transparent photosensitive resin, the refractive index of the outer layer 42 is larger than that of the inner layer 41, which can increase the refraction of light and thus improve the reflectivity of the overall reflective structure layer 2.

[0073] The following verifies that the reflective structure layer 2 in the circuit board 100 provided by the embodiments of the present application has higher reflectivity through specific examples. Among them, example 1 is to form a reflective layer 3 by curing a white ink layer in the form of a dry film, and a transparent photosensitive layer 4 is coated on the reflective layer 3 to form a double-layered reflective structure layer 2; the difference between comparative example 1 and example 1 is that the transparent photosensitive layer 4 is not arranged; example 2 is to form a reflective layer 3 by curing a white ink layer in the form of a wet film, and a transparent photosensitive layer 4 is coated on the reflective layer 3 to form a double-layered reflective structure layer 2; the difference between comparative example 2 and example 2 is that the transparent photosensitive layer 4 is not arranged. As shown in Figure 6 , compared with comparative example 1, the reflectivity of example 1 is increased by 2.12%, and compared with comparative example 2, the reflectivity of example 2 is increased by 2.38%. It can be seen that after the transparent photosensitive layer 4 is coated on the reflective layer 3, the reflectivity of the overall reflective structure layer 2 can be effectively improved. The reflective layer 3 formed by the dry film can make the reflectivity of the final reflective structure layer 2 reach more than 93%, and the reflective layer 3 formed by the wet film can make the reflectivity of the final reflective structure layer 2 reach more than 87%, which is obviously higher than the reflectivity of the conventional Mini LED backlight plate (usually the reflectivity of the dry film method is less than 89%, and the reflectivity of the wet film method is less than 85%).

[0074] Please refer to Figure 7 , the present application also provides a backlight module 200, which comprises a backlight plate 201, and the backlight plate 201 comprises the circuit board 100 as described above, and the opening of the circuit board 100 is welded with an LED lamp. In addition, the backlight plate 201 further comprises an outer frame 202 for carrying the circuit board 100. In some embodiments, the backlight module 200 can further comprise a diffusion sheet or other optical film material.

[0075] The circuit board 100 provided by the embodiments of the present application can improve the thickness and flatness of the reflective structure layer 2 by adopting the "big package small" method to form a double-layered reflective structure layer 2, coating a transparent photosensitive layer 4 on the surface of the reflective layer 3, reduce light loss, improve reflectivity (reflectivity more than 93%) and uniformity, and thus improve the brightness of the product using the circuit board 100. At the same time, it can also reduce the size of the side etching of the bottom of the reflective layer 3 (compared with the traditional solder mask layer, the size of the side etching is reduced by at least 45%), which can improve the bonding force between the reflective layer 3 and the circuit substrate 1, and reduce the risk of the reflective layer 3 being pulled off.

[0076] Please refer to Figure 8 , please refer to Figure 1 The present application also provides a preparation method of the aforementioned circuit board 100, which comprises the following steps:

[0077] Step S1, forming an ink layer on the surface of at least one circuit layer 12 of the circuit board 1.

[0078] Step S2, forming a transparent photosensitive resin layer on the surface of the ink layer.

[0079] Step S3, curing the ink layer by light to form a reflective layer 3, and curing the transparent photosensitive resin layer to form a transparent photosensitive layer 4 covering the outer surface of the reflective layer 3, the transparent photosensitive layer 4 and the reflective layer 3 constitute a reflective structure layer 2, thereby obtaining the circuit board 100.

[0080] In some embodiments, step S3 comprises:

[0081] Step S31, forming a patterned film on the surface of the transparent photosensitive layer 4, the patterned film has a pattern area and a gap area.

[0082] Step S32, providing light of a first wavelength to cure the ink layer corresponding to the gap area to form the reflective layer 3, the first wavelength is 440 nm and 425 nm in turn; and providing light of a second wavelength to cure the transparent photosensitive resin layer corresponding to the gap area to form the transparent photosensitive layer 4, the second wavelength is 405 nm, 385 nm and 365 nm in turn.

[0083] Specifically, this step is an exposure step. During the exposure process, the part of the ink layer and the photosensitive resin layer not covered by the patterned film is cured under the light of different wavelengths, and the part of the ink layer and the photosensitive resin layer covered by the patterned film is not cured, so as to be removed subsequently.

[0084] Step S33, removing the transparent photosensitive resin layer and the ink layer corresponding to the patterned film and the pattern area to form an opening 21, part of the circuit layer 12 is exposed by the opening 21.

[0085] Step S34, heating the transparent photosensitive layer 4 after forming the opening 21, so that the transparent photosensitive layer 4 extends to the sidewall of the opening 21, thereby obtaining the circuit board 100.

[0086] After the opening 21 is formed, the transparent photosensitive layer 4 is preheated (the temperature can be around 60±2°C) to soften and undergo a secondary melt, allowing it to flow to the sidewalls of the opening 21 to cover the reflective layer 3 exposed by the opening 21. Furthermore, the transparent photosensitive layer 4 can also fill the area where undercuts have occurred at the bottom of the reflective layer 3 to improve the bonding strength between the reflective layer 3 and the circuit substrate 1 and reduce the risk of the reflective layer 3 being pulled off due to tension. It is understood that the fluidity of the secondary melted transparent photosensitive layer 4 does not need to be too high. When heating the transparent photosensitive layer 4, the degree of fluidity of the transparent photosensitive layer 4 can be controlled by controlling the temperature and heating time, etc., to avoid affecting the overall performance of the transparent photosensitive layer 4.

[0087] See also Figure 9 As shown, during the curing process, two types of wavelengths of light are required to achieve simultaneous curing of the reflective layer 3 and the transparent photosensitive layer 4. The white ink layer needs to be exposed with long wavelengths. In this embodiment, long wavelengths of 425nm and 440nm are used to cure the white ink layer. The dual long waves can penetrate into the bottom of the white ink layer, thereby achieving full curing of the white ink layer and improving the curing degree of the reflective layer 3, so as to reduce the influence of the etching solution on the reflective layer 3 during the subsequent etching process, especially reducing the degree of side etching of the reflective layer 3. The transparent photosensitive resin layer needs to be exposed with short wavelengths. In this embodiment, three wavelengths of 365nm, 385nm, and 405nm are used to cure the transparent photosensitive resin. The three wavelengths can fully cure the transparent photosensitive resin located on the outside. As shown Figure 8 As shown, when light is emitted, the refractive index of the light wave increases due to the difference in refractive index when it enters the object, increasing the frequency of the refracted light wave and enhancing curing. After development, the transparent photosensitive layer 4 is preheated to cause a secondary melting process and flow to the sidewalls of the opening 21, forming a double-layer structure with a "large layer enclosing a small layer." Furthermore, using three wavelengths to cure the transparent photosensitive resin layer allows the inner and outer layers 41, 42 of the transparent photosensitive resin to cure to different degrees, resulting in layers 41 and 42 with varying refractive indices. This increases the refraction of light by the outer layer 42, further improving reflectivity.

[0088] If openings 21 are required in the reflective structure layer 2, a cover film must be formed on the transparent photosensitive resin layer before step S31. After step S32, development, windowing, and post-baking steps are required. Exposure, development, and windowing of the cover film, white ink layer, and transparent photosensitive resin layer are performed simultaneously, simplifying the process, improving efficiency, and saving labor costs.

[0089] The following provides specific manufacturing processes of two circuit boards 100 based on different molding methods of the reflective layer 3 .

[0090] For the first process (wet process), please refer toFigures 10A to 10K , and refer to Figure 1 :

[0091] Step S101, as Figure 10A As shown, a substrate 10 is provided. The substrate 10 includes a base layer 11 and metal layers 20 located on two opposite surfaces of the base layer 11.

[0092] Step S102, as Figure 10B and Figure 10C As shown, the substrate 10 is drilled and copper is reduced / brown.

[0093] Step S103, as Figure 10D and Figure 10E As shown, the copper-reduced / brown-plated substrate 10 is subjected to horizontal electroplating and hole-filling electroplating to form intermediate metal layers 30 on two opposite surfaces of the base layer 11 .

[0094] Step S104, as Figures 10F to 101 As shown, the intermediate metal layer 30 is patterned to form a circuit layer 12 to obtain a circuit substrate 1 .

[0095] Step S105, as Figure 10J As shown, white ink is printed on two opposite surfaces of the base layer 11 of the circuit substrate 1 and pre-baked to form a white ink layer 40 .

[0096] Step S106, as Figure 10K As shown, a transparent photosensitive resin layer 50 is formed on the surface of the white ink layer 40 by lamination.

[0097] Step S107, as Figure 10K As shown, a patterned film 60 is laminated on the surface of the transparent photosensitive resin layer 50 , and the patterned film 60 has a pattern area and a gap area.

[0098] Specifically, the graphic area of ​​the patterned film 60 can block the portions of the transparent photosensitive resin layer 50 and the white ink layer 40 where openings are required, and the other portions are exposed from the gap area.

[0099] Step S108, as Figure 10K As shown, the intermediate circuit board covered with the patterned film 60 is exposed to light, so that the white ink layer 40 corresponding to the gap area is cured to form the reflective layer 3, and the transparent photosensitive resin layer 50 corresponding to the gap area is cured to form the transparent photosensitive layer 4.

[0100] In step S109 , the patterned film 60 is removed, and at the same time, the white ink layer 40 and the transparent photosensitive resin layer 50 corresponding to the gap area are etched away by development to form an opening 21 penetrating the reflective structure layer 2 .

[0101] Step S110, as Figure 10K, combined with Figure 1 As shown, after the opening 21 is formed, the transparent photosensitive layer 4 is preheated to extend to the sidewall of the opening 21 to cover the portion of the reflective layer 3 exposed by the opening 21 , thereby obtaining the circuit board 100 .

[0102] For the specific exposure wavelength, please refer to the above description of step S3, which will not be elaborated here.

[0103] The second process (dry process) differs from the first process in that the white ink layer 40 is formed in a different manner. In this embodiment, the white ink layer 40 is directly pressed onto the surface of the base layer 11 of the circuit substrate 1 without pre-baking.

[0104] The method for preparing the circuit board 100 provided in the embodiment of the present application utilizes dual-wavelength curing of the white ink layer, which allows for more complete curing of the white ink layer, particularly penetrating the bottom of the white ink layer, thereby improving the curing degree of the bottom layer and reducing the extent of undercutting of the reflective layer 3 during subsequent etching. Furthermore, the method utilizes three wavelengths to cure the transparent photosensitive resin layer, achieving full curing of the outer transparent photosensitive resin layer, thereby forming an inner layer 41 and an outer layer 42 with different degrees of curing in the transparent photosensitive layer 4. The refraction of light by the outer layer 52 increases the reflectivity of the overall reflective structure layer 2. Furthermore, by preheating the transparent photosensitive layer 4, a secondary melting of the transparent photosensitive layer 4 occurs, allowing the transparent photosensitive layer 4 to cover the portion of the reflective layer 3 exposed by the opening 21, forming a "large-enclosing-small" double-layer structure. This reduces the appearance of stepped structures on the sidewalls of the reflective layer 3, which can affect reflectivity. It also enhances the bonding strength between the reflective layer 3 and the circuit substrate 1, reducing the risk of the reflective structure layer 2 being pulled off. In addition, the reflective structure layer 2 and the opening 21 can be formed by a single exposure, development and window opening, which simplifies the process, improves efficiency and saves labor costs.

Claims

1. A circuit board, characterized by, The application relates to a circuit board and a manufacturing method thereof. The circuit board comprises a circuit substrate and a reflective structure layer, the circuit substrate comprises a base layer and a circuit layer arranged on at least one surface of the base layer, and the reflective structure layer is arranged on the surface of the base layer and covers at least part of the circuit layer, wherein the reflective structure layer comprises a reflective layer and a transparent photosensitive layer arranged on the surface of the circuit substrate in sequence, and the transparent photosensitive layer covers the outer surface of the reflective layer.

2. The circuit board of claim 1, wherein, The side etching size of the reflective layer is less than or equal to 12.8 microns along the extension direction of the circuit board.

3. The circuit board of claim 1, wherein, The transparent photosensitive layer comprises an inner layer close to the reflective layer and an outer layer arranged on the surface of the inner layer away from the reflective layer, the inner layer and the outer layer are in an integrated structure, and the refractive index of the outer layer is greater than that of the inner layer.

4. The circuit board of claim 1, wherein, The reflective layer is formed by curing a dry film or a wet film, the material of the dry film or the wet film is white ink, the thickness of the reflective layer formed by the dry film is 30-60 microns, the thickness of the reflective layer formed by the wet film is 22-45 microns, and the transparent photosensitive layer is formed by curing transparent photosensitive resin, and the thickness of the transparent photosensitive layer is 25-35 microns.

5. The circuit board of claim 4, wherein, When the reflective structure layer comprises the reflective layer formed by the dry film, the reflectivity of the reflective structure layer is greater than or equal to 93%. When the reflective structure layer comprises the reflective layer formed by the wet film, the reflectivity of the reflective structure layer is greater than or equal to 87%.

6. The circuit board of claim 1, wherein, The circuit layer comprises a connecting pad, the reflective structure layer is provided with an opening corresponding to the connecting pad, part of the connecting pad is exposed by the opening, and the circuit board further comprises an electronic element, the electronic element is arranged in the opening and electrically connected to the connecting pad.

7. A method of manufacturing a circuit board, characterized by, The application relates to a circuit board and a manufacturing method thereof. An ink layer is formed on at least one surface of a circuit layer of a circuit substrate. A transparent photosensitive resin layer is formed on the surface of the ink layer. And The ink layer is cured to form a reflective layer by light irradiation, the transparent photosensitive resin layer is cured to form a transparent photosensitive layer covering the outer surface of the reflective layer, the transparent photosensitive layer and the reflective layer constitute a reflective structure layer, and thus the circuit board is obtained.

8. The method of manufacturing a circuit board according to claim 7, wherein The step of curing the ink layer to form a reflective layer and curing the transparent photosensitive resin layer to form a transparent photosensitive layer covering the outer surface of the reflective layer by light irradiation comprises the following steps. A patterned film is formed on the surface of the transparent photosensitive layer, the patterned film has a pattern area and a gap area. First light with a first wavelength is provided to cure the ink layer corresponding to the gap area to form the reflective layer, the first wavelength is 440 nm and 425 nm, second light with a second wavelength is provided to cure the transparent photosensitive resin layer corresponding to the gap area to form the transparent photosensitive layer, the second wavelength is 405 nm, 385 nm and 365 nm. The transparent photosensitive resin layer and the ink layer corresponding to the pattern area of the patterned film are removed to form an opening, part of the circuit layer is exposed by the opening; and The transparent photosensitive layer after the opening is formed is heated to extend the transparent photosensitive layer to the sidewall of the opening, and thus the circuit board is obtained.

9. The method of manufacturing a circuit board according to claim 8, wherein The step of forming an ink layer on the surface of at least one circuit layer of the circuit substrate includes: printing white ink on the surface of at least one circuit layer of the circuit substrate to form the ink layer; or pressing the ink layer on the surface of at least one circuit layer of the circuit substrate by pressing.

10. A backlight module, characterized in that, A backlight panel comprising a circuit board as claimed in any one of claims 1 to 6 or a circuit board prepared by the method of preparing a circuit board as claimed in any one of claims 7 to 9.

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