Multilayer circuit board and manufacturing method thereof, and display module

Abstract

The present application discloses a multilayer circuit board and a manufacturing method thereof, and a display module. Different from the existing multilayer circuit board in which two adjacent circuit layers are electrically connected by physically punching holes in a PCB board, the multilayer circuit board in which two adjacent circuit layers are electrically connected is achieved through a plurality of through holes filled with metal materials in a positive photoresist layer. Since a plurality of through holes penetrating the positive photoresist layer can be formed in batches through a single photolithography process, the positive photoresist layer between two adjacent circuit layers can be punched in batches, which is highly efficient and low in cost. Furthermore, the through holes penetrating the positive photoresist layer are not prone to residual debris, so that the two adjacent circuit layers can be effectively connected. The aperture of the through hole is also relatively uniform, and the aperture size can be relatively small, which is beneficial to improving the display effect of MiniLED and Micro LED and realizing miniaturization and thin design.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a multi-layer circuit board and a manufacturing method thereof, and a display module. Background Art

[0002] In the current context of the Internet of Everything, the quality requirements for display panels are getting higher and higher. Mini LED (Light Emitting Diode, LED) and Micro LED, as the future development direction of the display industry, have become the objects sought after by major display manufacturers. In order to achieve the ever-changing display effects of Mini LED and Micro LED, multi-layer circuits are required to transmit driving signals to Mini LED and Micro LED. Therefore, depositing multi-layer circuits on the substrate to form a multi-layer circuit board is a technical problem that must be overcome.

[0003] In existing multi-layer circuit boards, each circuit layer is made of a PCB (Printed Circuit Board, PCB) board, and multiple PCB boards are stacked to form a multi-layer circuit layer, and the two adjacent circuit layers are electrically connected by physically punching holes (such as laser drilling) on ​​the PCB board. However, the number of holes punched between the circuit layers corresponding to Mini LED and Micro LED is usually huge, but the existing technology cannot achieve batch punching of PCB boards between two adjacent circuit layers. Summary of the invention

[0004] In order to solve the above technical problems, the embodiments of the present application provide a multi-layer circuit board and a manufacturing method thereof, and a display module to realize batch punching between two adjacent circuit layers in a multi-layer circuit board.

[0005] To achieve the above objectives, the present application provides the following technical solutions:

[0006] A multilayer circuit board, comprising:

[0007] substrate;

[0008] A multilayer circuit layer located on one side of the substrate, the multilayer circuit layer includes the 1st circuit layer to the Nth circuit layer arranged in sequence along the direction away from the substrate, wherein a positive photoresist layer is arranged between the i-th circuit layer and the i+1-th circuit layer, the positive photoresist layer has a plurality of penetrating through holes, and the through holes are filled with metal material to electrically connect the i-th circuit layer and the i+1-th circuit layer, 1≤i≤N-1, N≥2.

[0009] Optionally, the substrate is a glass substrate, and a first primer layer is provided between the substrate and the first circuit layer, and the first primer layer is used to bond the substrate and the first circuit layer.

[0010] Optionally, the first primer layer is a mixed material layer of zirconium metal and indium tin oxide.

[0011] Optionally, a second coating layer is provided between the i-th circuit layer and the i+1-th circuit layer, and the second coating layer is located on the side of the positive photoresist layer close to the i+1-th circuit layer, and the second coating layer is used to bond the positive photoresist layer and the i+1-th circuit layer.

[0012] Optionally, the second primer layer is a mixed material layer of aluminum metal and chromium metal.

[0013] Optionally, the diameter of the through hole penetrating the positive photoresist layer is less than 100 μm.

[0014] A method for manufacturing a multilayer circuit board, comprising:

[0015] S1: providing a substrate;

[0016] S2: depositing a metal film layer on one side of the substrate;

[0017] S3: coating a negative photoresist layer on the side of the metal film layer facing away from the substrate, exposing the negative photoresist layer using a preset first photomask, and developing the exposed negative photoresist layer to form a preset pattern on the negative photoresist layer;

[0018] S4: using the negative photoresist layer with a preset pattern as a mask, etching the metal film layer to form a circuit layer, and removing the negative photoresist layer;

[0019] S5: coating a positive photoresist layer, exposing the positive photoresist layer using a preset second photomask, and developing the exposed positive photoresist layer to form a plurality of through holes penetrating the positive photoresist layer;

[0020] S6: depositing another metal film layer on the side of the positive photoresist layer facing away from the substrate, so that the through hole is filled with metal material;

[0021] S7: Return to step S3-S4, and form another circuit layer on the side of the positive photoresist layer away from the substrate;

[0022] Among them, steps S5-S7 are performed N-1 times until N circuit layers are formed on one side of the substrate and are arranged in sequence in a direction away from the substrate, and the i-th circuit layer and the i+1-th circuit layer are electrically connected through a through hole filled with metal material in the positive photoresist layer therebetween, 1≤i≤N-1, N≥2.

[0023] Optionally, the substrate is a glass substrate, and before step S2, the method further includes:

[0024] S8: depositing a first primer layer on one side of the substrate;

[0025] Step S2 includes:

[0026] Depositing a metal film layer on the side of the first bottom layer away from the substrate;

[0027] In step S4, the metal film layer is etched to form the first circuit layer, and the first primer layer is etched at the same time, so that the first primer layer adheres to the substrate and the first circuit layer.

[0028] Optionally, before performing step S6 each time, the method further includes:

[0029] S9: depositing a second primer layer on the side of the positive photoresist layer facing away from the substrate, and covering the sidewall of the through hole with the second primer layer;

[0030] Step S6 includes:

[0031] Depositing a metal film layer on the side of the second bottom layer away from the substrate so that the through hole is filled with metal material;

[0032] In step S4, when the metal film layer is etched to form the i+1th circuit layer, the second primer layer is etched at the same time so that the second primer layer adheres to the positive photoresist layer and the i+1th circuit layer.

[0033] A display module, comprising a driving component, a multi-layer circuit board and a plurality of LED chips, wherein the multi-layer circuit board is any of the multi-layer circuit boards described above;

[0034] Among them, the driving component is electrically connected to one or more circuit layers in the multi-layer circuit board, the Nth circuit layer in the multi-layer circuit board is electrically connected to the multiple LED chips, and the driving component drives the multiple LED chips to emit light through the multi-layer circuit board.

[0035] Compared with the prior art, the above technical solution has the following advantages:

[0036] The multilayer circuit board provided in the embodiment of the present application comprises a substrate and N circuit layers arranged in sequence along a direction away from the substrate on one side of the substrate, wherein a positive photoresist layer is provided between the i-th circuit layer and the i+1-th circuit layer, and the positive photoresist layer has a plurality of through holes, and the through holes are filled with metal materials to electrically connect the i-th circuit layer and the i+1-th circuit layer. It can be seen that, unlike the existing multilayer circuit board in which two adjacent circuit layers are electrically connected by physically punching holes in the PCB board, in the multilayer circuit board provided in the embodiment of the present application, the electrical connection between the two adjacent circuit layers is achieved by a plurality of through holes filled with metal materials in the positive photoresist layer, and since the plurality of through holes in the positive photoresist layer can be formed in batches by a single photolithography process, the positive photoresist layer between the two adjacent circuit layers can be punched in batches, which is highly efficient and low in cost.

[0037] Moreover, after the PCB board is physically punched in the prior art, debris is very likely to remain in the hole, causing blockage, resulting in the inability of two adjacent circuit layers to be effectively connected. In the multi-layer circuit board provided in the embodiment of the present application, the electrical connection between the two adjacent circuit layers is achieved through a plurality of through holes filled with metal materials in the positive photoresist layer. Since the portion corresponding to the through hole in the positive photoresist layer can be completely developed in the photolithography process, it is not easy for debris to remain in the through hole that penetrates the positive photoresist layer, and it will not cause blockage, so that the two adjacent circuit layers can be effectively connected.

[0038] Moreover, it is difficult to ensure the uniformity of the aperture size by physically punching holes in PCB boards using the prior art, but Mini LED and Micro LED have extremely strict requirements on the aperture of the through holes between circuit layers. Any deviation in the aperture size will cause a deviation in the display effect. In the multilayer circuit board provided in the embodiment of the present application, the electrical connection between two adjacent circuit layers is achieved through a plurality of through holes filled with metal materials in the positive photoresist layer. Since the aperture of the through holes in the positive photoresist layer can be controlled by the photoresist pattern in the photolithography process, a plurality of through holes with uniform aperture can be formed in the positive photoresist layer, and the aperture size of the through holes can be smaller, which is beneficial to improving the display effect of Mini LED and Micro LED and realizing miniaturized design.

[0039] In addition, due to the large thickness of the PCB board, the thickness of the existing multi-layer circuit board is large, which is not conducive to a lightweight design. In the multi-layer circuit board provided in the embodiment of the present application, there is a positive photoresist layer between adjacent circuit layers, and the thickness of the positive photoresist layer can be set according to demand, which is conducive to achieving a lightweight design. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 A schematic diagram of the structure of a multilayer circuit board provided by one embodiment of the present application;

[0042] Figure 2 A cross-sectional schematic diagram of a multilayer circuit board provided by one embodiment of the present application;

[0043] Figure 3 A cross-sectional schematic diagram of a multilayer circuit board provided in another embodiment of the present application;

[0044] Figure 4 A schematic diagram of a process for manufacturing a multilayer circuit board provided in one embodiment of the present application;

[0045] Figure 5(a)-Figure 5(j) A schematic diagram of the structures corresponding to the various process steps in the method for manufacturing a multilayer circuit board provided in one embodiment of the present application;

[0046] Figure 6(a)-Figure 6(f) A schematic structural diagram corresponding to each process step in a method for manufacturing a multilayer circuit board provided in another embodiment of the present application;

[0047] Figure 7(a)-Figure 7(c) A schematic structural diagram corresponding to each process step in a method for manufacturing a multilayer circuit board provided in another embodiment of the present application;

[0048] Figure 8 A schematic diagram of the structure of a display module provided in one embodiment of the present application. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0050] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0051] Secondly, the present application is described in detail with reference to the schematic diagram. When describing the embodiments of the present application in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present application. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0052] As described in the background technology section, the number of holes punched between the circuit layers corresponding to MiniLED and Micro LED is usually huge, but the existing technology cannot achieve batch punching by physically punching holes in the PCB board between two adjacent circuit layers.

[0053] In view of this, an embodiment of the present application provides a multilayer circuit board 100, Figure 1 The structure diagram of the multilayer circuit board 100 provided in the embodiment of the present application is shown as follows: Figure 1 As shown, the multilayer circuit board 100 includes:

[0054] substrate 10;

[0055] The multi-layer circuit layer 20 is located on one side of the substrate 10, and the multi-layer circuit layer 20 includes a circuit layer extending in a direction away from the substrate 10 (eg Figure 1 The first circuit layer 20 to the Nth circuit layer 20 are arranged in sequence (in the middle Z direction), wherein a positive photoresist layer 30 is arranged between the i-th circuit layer 20 and the i+1-th circuit layer 20, and the positive photoresist layer 30 has a plurality of penetrating through holes 31, and the through holes 31 are filled with metal material to electrically connect the i-th circuit layer 20 and the i+1-th circuit layer 20, 1≤i≤N-1, N≥2.

[0056] Specific as Figure 1 As shown, along the direction away from the substrate 10 (such as Figure 1 In the Z direction), a positive photoresist layer 30 is arranged between the first circuit layer 20 and the second circuit layer 20, and the positive photoresist layer 30 has a plurality of through holes 31 penetrating therethrough, and the through holes 31 are filled with metal material, so that the first circuit layer 20 and the second circuit layer 20 are electrically connected through the through holes 31 filled with metal material in the positive photoresist layer 30 between the two. Similarly, the i-th circuit layer 20 and the i+1-th circuit layer 20 are electrically connected through the through holes 31 filled with metal material in the positive photoresist layer 30 between the two, and 1≤i≤N-1.

[0057] Different from the existing multi-layer circuit board, each circuit layer is made of a PCB board, and the electrical connection between two adjacent circuit layers is achieved by physically punching the PCB board (such as laser drilling), in the multi-layer circuit board 100 provided in the embodiment of the present application, except for the first circuit layer 20 located on the substrate 10, the other circuit layers 20 are all located on the positive photoresist layer 30, and the electrical connection between the two adjacent circuit layers 20 is achieved through the through hole 31 filled with metal material in the positive photoresist layer 30, that is, the positive photoresist layer 30 between the two adjacent circuit layers 20 in the multi-layer circuit board 100 provided in the embodiment of the present application has the same function as the PCB board between the two adjacent circuit layers in the existing multi-layer circuit board, both of which play the role of carrying the circuit layer and realizing the electrical connection between the two adjacent circuit layers. That is to say, in the multi-layer circuit board 100 provided in the embodiment of the present application, the positive photoresist layer 30 between the two adjacent circuit layers 20 is used to replace the PCB board between the two adjacent circuit layers in the existing multi-layer circuit board.

[0058] The through holes 31 penetrating the positive photoresist layer 30 can be realized by a photolithography process rather than physical drilling. Specifically, after coating the positive photoresist layer 30, the positive photoresist layer 30 can be exposed using a preset photoresist plate, and the exposed positive photoresist layer 30 can be developed to form a plurality of penetrating through holes in the positive photoresist layer 30. As long as the positions, number and aperture sizes of the through holes are designed in the preset photoresist plate, batch drilling of the positive photoresist layer 30 can be achieved in one photolithography process.

[0059] It should be noted that photoresist is usually exposed under ultraviolet light, and due to the characteristics of positive photoresist, the positive photoresist becomes particularly resistant to acid and alkali after exposure to ultraviolet light. Therefore, the multilayer circuit board 100 provided in the embodiment of the present application, since the positive photoresist layer 30 has been exposed to ultraviolet light during the manufacturing process, will not be deformed when inevitably exposed to ultraviolet light during use, and is also particularly resistant to acid and alkali, and has good reliability.

[0060] It should also be noted that the present application does not limit the number of layers of the circuit layer 20. Figure 1 Only two circuit layers 20 are shown, and the specific number of circuit layers 20 can be set according to actual needs.

[0061] It can be seen that, unlike the existing multi-layer circuit board in which electrical connection is achieved between two adjacent circuit layers by physically punching holes in the PCB board, in the multi-layer circuit board 100 provided in the embodiment of the present application, electrical connection between two adjacent circuit layers 20 is achieved through a plurality of through holes 31 filled with metal material in the positive photoresist layer 30. Since a plurality of penetrating through holes 31 in the positive photoresist layer 30 can be formed in batches through a single photolithography process, batch punching of the positive photoresist layer 30 between two adjacent circuit layers 20 can be achieved, which is extremely efficient and low-cost.

[0062] Moreover, after the prior art physically punches holes in the PCB board, it is very easy for debris to remain in the holes and cause blockage, resulting in the inability of two adjacent circuit layers to be effectively connected. In the multi-layer circuit board 100 provided in the embodiment of the present application, the electrical connection between the two adjacent circuit layers 20 is achieved through a plurality of through holes 31 filled with metal material in the positive photoresist layer 30. Since the portion of the positive photoresist layer 30 corresponding to the through hole 31 can be completely developed in the photolithography process, it is not easy for the through hole 31 penetrating the positive photoresist layer 30 to retain debris and cause blockage, so that the two adjacent circuit layers 20 can be effectively connected.

[0063] Moreover, it is difficult to ensure the uniformity of the aperture size by physically punching holes in PCB boards using the prior art, but MiniLED and Micro LED have extremely strict requirements on the aperture of the through holes between circuit layers. Any deviation in the aperture size will cause a deviation in the display effect. In the multilayer circuit board 100 provided in the embodiment of the present application, the electrical connection between two adjacent circuit layers 20 is achieved through a plurality of through holes 31 filled with metal material in the positive photoresist layer 30. Since the aperture of the through holes 31 in the positive photoresist layer 30 can be controlled by the photoresist pattern in the photolithography process, a plurality of through holes 31 with uniform aperture can be formed in the positive photoresist layer 30, and the aperture size of the through holes 31 can be smaller, which is beneficial to improving the display effect of Mini LED and Micro LED and realizing miniaturized design.

[0064] In addition, due to the large thickness of the PCB board, the thickness of the existing multi-layer circuit board is large, which is not conducive to a lightweight design. In the multi-layer circuit board 100 provided in the embodiment of the present application, there is a positive photoresist layer 30 between adjacent circuit layers 20, and the thickness of the positive photoresist layer 30 can be set according to demand, which is conducive to achieving a lightweight design.

[0065] In the embodiment of the present application, the circuit layer 20 may be a copper (Cu) circuit layer, but the present application does not limit this, and the circuit layer 20 may also be a circuit layer of other metals.

[0066] In the embodiment of the present application, the metal material filled in the through hole 31 in the positive photoresist layer 30 may be copper (Cu) metal, but the present application does not limit this. The metal material filled in the through hole 31 in the positive photoresist layer 30 may also be other metals besides copper (Cu) metal.

[0067] In the embodiment of the present application, the circuit patterns between different circuit layers 20 may be the same or different, depending on the specific situation.

[0068] In the embodiment of the present application, the substrate 10 may be a PCB board, a glass substrate, or a substrate made of other materials, depending on the specific circumstances.

[0069] Since the PCB board is easily deformed at high temperature, and the glass substrate is resistant to high temperature, therefore, optionally, in one embodiment of the present application, the substrate 10 is a glass substrate, so that the multi-layer circuit board 100 can be resistant to high temperature. However, when a metal film layer is deposited on the glass substrate 10 to form the circuit layer 20, there is a problem that the glass substrate 10 (insulating film layer) and the metal film layer are difficult to effectively combine, so that the circuit layer 20 is easy to fall off. Based on this, in this embodiment, if Figure 2 As shown, Figure 2 As shown in the cross-sectional schematic diagram of the multilayer circuit board 100 provided in the present embodiment, a first coating layer 40 is provided between the substrate 10 and the first wiring layer 20. The first coating layer 40 is used to bond the substrate 10 and the first wiring layer 20 so that the glass substrate 10 and the first wiring layer 20 are effectively combined to prevent the first wiring layer 20 from falling off the glass substrate 10.

[0070] It should be noted that Figure 2 The two-layer circuit layer 20 is used as an example for demonstration, and the specific number of circuit layers 20 can be set according to actual needs. Figure 2 As shown, when a metal film layer is deposited on the positive photoresist layer 30 to prepare the circuit layer 20 , the metal film layer will fill the through hole 31 , so that the through hole 31 is filled with metal material.

[0071] Based on the above embodiment, optionally, in one embodiment of the present application, the first coating layer 40 is a mixed material layer of zirconium metal (Zr) and indium tin oxide (ITO). The inventor verified through experiments that when the first coating layer 40 is a mixed material layer of zirconium metal (Zr) and indium tin oxide (ITO), the glass substrate 10 and the first circuit layer 20 can be effectively combined.

[0072] It should be noted that, in the actual process of manufacturing the multi-layer circuit board 100, when the positive photoresist layer 30 is coated on the circuit layer 20, the circuit layer 20 and the positive photoresist layer 30 are well bonded, and when the metal film layer is sputtered and deposited on the positive photoresist layer 30 to manufacture the circuit layer, the metal film layer sputtered and deposited on the positive photoresist layer 30 has insufficient adhesion due to the high sputtering temperature. In order to prevent the circuit layer 20 deposited on the positive photoresist layer 30 from falling off, optionally, in one embodiment of the present application, as Figure 3 As shown, Figure 3 The cross-sectional view of the multi-layer circuit board 100 provided in this embodiment shows that in the i-th circuit layer 20 (for example Figure 3 The first circuit layer 20) and the i+1th circuit layer 20 (e.g. Figure 3 A second base layer 50 is also provided between the positive photoresist layer 30 and the second circuit layer 20. The second base layer 50 is located near the positive photoresist layer 30 and the i+1th circuit layer 20 (for example Figure 3 The second wiring layer 20) is located on one side of the positive photoresist layer 50 and the i+1th wiring layer 20 (eg Figure 3 The positive photoresist layer 30 is used to bond the positive photoresist layer 30 and the i+1th circuit layer 20 , so that the positive photoresist layer 30 and the i+1th circuit layer 20 are effectively combined to prevent the i+1th circuit layer 20 from falling off from the positive photoresist layer 30 .

[0073] Furthermore, considering that the positive photoresist layer 30 between two adjacent circuit layers 20 is made of a liquid substrate, the positive photoresist layer 30 will contain more or less moisture. In particular, after the multi-layer circuit board 100 is manufactured, a constant temperature and humidity test is usually required. If the positive photoresist layer 30 is not protected from water, some moisture will inevitably recombine with the positive photoresist layer 30 during the constant temperature and humidity test. Therefore, in this embodiment, the second primer layer 50 provided between the positive photoresist layer 50 and the i+1th circuit layer 20 can not only effectively combine the positive photoresist layer 30 and the i+1th circuit layer 20, but also serve as a waterproof film layer for the positive photoresist layer 30 to prevent the positive photoresist layer 30 from being penetrated by moisture and impacting and damaging the i+1th circuit layer 20.

[0074] It should be noted that Figure 3 The two-layer circuit layer 20 is used as an example for demonstration, and the specific number of circuit layers 20 can be set according to actual needs. Figure 3As shown, when the second primer layer 50 is deposited on the positive photoresist layer 30, the second primer layer 50 will cover the side walls of the through hole 31 and the exposed circuit layer 20 of the through hole 31. Then, when the metal film layer is deposited to fill the through hole 31 and prepare the circuit layer 20, the metal material filled in the through hole 31 and the positive photoresist layer 30 are also bonded together by the second primer layer 50, and the positive photoresist layer 30 is prevented from being penetrated by moisture and impacting and damaging the i+1th circuit layer 20.

[0075] It should also be noted that Figure 3 The through hole 31 is shown to be filled with metal material, but the present application does not limit whether the through hole 31 is filled with metal material. In fact, the metal material filled in the through hole 31 only needs to electrically connect the upper and lower circuit layers.

[0076] Based on the above embodiment, optionally, in one embodiment of the present application, the second base layer 50 is a mixed material layer of aluminum (Al) metal and chromium (Cr) metal.

[0077] The inventors verified through experiments that since the positive photoresist layer 30 contains more or less moisture, and the metal film layer needs to be deposited under vacuum when depositing on the positive photoresist layer 30, it is very difficult to find a primer material that can effectively combine with the positive photoresist layer 30 containing moisture during the vacuum coating process. In this embodiment, when the second primer layer 50 is a mixed material layer of aluminum (Al) metal and chromium (Cr) metal, the positive photoresist layer 30 and the i+1th circuit layer 20 can be effectively combined to prevent the i+1th circuit layer 20 from falling off the positive photoresist layer 30.

[0078] Moreover, in the present embodiment, since the chromium (Cr) metal surface is easily passivated and has strong anti-oxidation ability and strong corrosion resistance, and since the aluminum (Al) metal surface is easy to form an Al2O3 passivation layer and has excellent gas barrier and moisture barrier properties, the second base layer 50 is a mixed material layer of aluminum (Al) metal and chromium (Cr) metal, which can have a good barrier effect against oxygen and water vapor, and effectively prevent moisture from damaging the positive photoresist layer 30, thereby having a good protective effect on the positive photoresist layer 30.

[0079] On the basis of any of the above embodiments, since the aperture of the through hole in the positive photoresist layer can be controlled by the photoresist pattern in the photolithography process, optionally, in one embodiment of the present application, the aperture of the through hole penetrating the positive photoresist layer is less than 100 μm, while the existing technology of physically punching a PCB board cannot achieve a through hole with such a small aperture size.

[0080] The present application also provides a method for manufacturing a multilayer circuit board. Figure 4The flowchart of the method for manufacturing a multilayer circuit board provided in the embodiment of the present application is shown as follows: Figure 4 As shown, the method includes:

[0081] S1: As shown in FIG. 5( a ), a substrate 10 is provided.

[0082] In practical applications, the substrate 10 needs to be cleaned by a cleaning machine.

[0083] S2: As shown in FIG. 5( b ), a metal film layer 21 is deposited on one side of the substrate 10 .

[0084] Optionally, the thickness of the metal film layer 21 may be 1 μm-10 μm, but the present application does not limit this and it depends on specific circumstances.

[0085] Optionally, the metal film layer 21 may be a copper (Cu) metal film layer, but the present application does not limit this and it depends on specific circumstances.

[0086] S3: As shown in FIG. 5( c ), a negative photoresist layer 60 is coated on the side of the metal film layer 21 facing away from the substrate 10 , and then as shown in FIG. 5( d ), the negative photoresist layer 60 is exposed using a preset first photomask, and the exposed negative photoresist layer 60 is developed to form a preset pattern in the negative photoresist layer 60 .

[0087] Optionally, the thickness of the negative photoresist layer 60 may be 2 μm-5 μm, but the present application does not limit this and it depends on specific circumstances.

[0088] Specifically, after the negative photoresist layer 60 is coated on the side of the metal film layer 21 facing away from the substrate 10, the negative photoresist layer 60 is baked at a temperature of 100°C to 130°C for 5min-10min to discharge a large amount of moisture in the negative photoresist layer 60; then, the negative photoresist layer 60 is exposed using a preset first photomask, and the exposure energy can be 100mj~200mj; then, the exposed negative photoresist layer 60 is developed using potassium hydroxide (KOH) or ammonium hydroxide (NH4OH) solution to form a preset pattern in the negative photoresist layer 60; then, the negative photoresist layer 60 needs to be solid-baked at a temperature of 120°C to 160°C for 5min~30min to discharge the moisture in the negative photoresist layer 60 again.

[0089] S4: As shown in FIG. 5( e ), the metal film layer 21 is etched using the negative photoresist layer 60 having a preset pattern as a mask to form a circuit layer 20 , and then as shown in FIG. 5( f ), the negative photoresist layer 60 is removed.

[0090] Specifically, when the metal film layer 21 is a copper (Cu) metal film layer, a negative photoresist layer 60 having a preset pattern is used as a mask, and the metal film layer 21 is etched using a copper etching solution to form a circuit layer 20, wherein the copper etching solution may have a ratio of nitric acid: 10%-15%, phosphoric acid: 35%-65%, and acetic acid: 2%-8%.

[0091] When removing the negative photoresist layer 60 , a potassium hydroxide (KOH) solution may be used to remove the negative photoresist layer 60 , so that the pattern of the circuit layer 20 is revealed.

[0092] S5: As shown in FIG. 5( g ), a positive photoresist layer 30 is coated, and then as shown in FIG. 5( h ), the positive photoresist layer 30 is exposed using a preset second photomask, and the exposed positive photoresist layer 30 is developed to form a plurality of penetrating through holes 31 in the positive photoresist layer 30 .

[0093] Specifically, after coating the positive photoresist layer 30, the positive photoresist layer 30 is baked at a temperature of 150°C to 240°C for 5min-10min to discharge a large amount of moisture in the positive photoresist layer 30; then, the positive photoresist layer 30 is exposed using a preset second photomask, and the exposure energy can be 200mj to 500mj; then, the exposed positive photoresist layer 60 is developed using potassium hydroxide (KOH) or ammonium hydroxide (NH4OH) solution to remove the positive photoresist corresponding to the through hole 31 to form the through hole 31.

[0094] S6: As shown in FIG. 5( i ), a metal film layer 21 is deposited on the side of the positive photoresist layer 30 facing away from the substrate 10 , so that the through hole 31 is filled with metal material.

[0095] It should be noted that when depositing the metal film layer 21 on the side of the positive photoresist layer 30 facing away from the substrate 10, direct current should be used for vacuum evaporation as much as possible, and low power (such as less than 1000W) should be used as much as possible to deposit the metal film layer 21 to avoid the deposited metal film layer particles from damaging the positive photoresist layer 30 in a vacuum environment.

[0096] S7: Return to step S3-S4, as shown in FIG5(j), another circuit layer 20 is formed on the side of the positive photoresist layer 30 facing away from the substrate 10.

[0097] Among them, steps S5-S7 are performed N-1 times until N circuit layers 20 are arranged in sequence along the direction away from the substrate 10 (Z direction) on one side of the substrate 10, and the i-th circuit layer 20 and the i+1-th circuit layer 20 are electrically connected through the through hole 31 filled with metal material in the positive photoresist layer 30 therebetween, 1≤i≤N-1, N≥2, and finally the following is obtained: Figure 1 The structure of the multi-layer wiring board 100 is shown.

[0098] Specific as Figure 1 As shown, along the direction away from the substrate 10 (such as Figure 1 In the Z direction), a positive photoresist layer 30 is arranged between the first circuit layer 20 and the second circuit layer 20, and the positive photoresist layer 30 has a plurality of through holes 31 penetrating therethrough, and the through holes 31 are filled with metal material, so that the first circuit layer 20 and the second circuit layer 20 are electrically connected through the through holes 31 filled with metal material in the positive photoresist layer 30 between the two. Similarly, the i-th circuit layer 20 and the i+1-th circuit layer 20 are electrically connected through the through holes 31 filled with metal material in the positive photoresist layer 30 between the two, and 1≤i≤N-1.

[0099] It should be noted that photoresist is usually exposed under ultraviolet light, and due to the characteristics of positive photoresist, the positive photoresist becomes particularly resistant to acid and alkali after exposure to ultraviolet light. Therefore, the multilayer circuit board 100 manufactured using the method provided in the embodiment of the present application, since the positive photoresist layer 30 has been exposed to ultraviolet light during the manufacturing process, will not be deformed when inevitably exposed to ultraviolet light during use, and is also particularly resistant to acid and alkali, and has good reliability.

[0100] It should also be noted that the present application does not limit the number of layers of the circuit layer 20. Figure 1 Only two circuit layers 20 are shown, and the specific number of circuit layers 20 can be set according to actual needs.

[0101] It can be seen that, unlike the existing multi-layer circuit board in which electrical connection is achieved between two adjacent circuit layers by physically punching holes in the PCB board, in the multi-layer circuit board 100 manufactured using the method provided in the embodiment of the present application, electrical connection between two adjacent circuit layers 20 is achieved through a plurality of through holes 31 filled with metal material in the positive photoresist layer 30. Since the plurality of penetrating through holes 31 in the positive photoresist layer 30 can be formed in batches through a single photolithography process, batch punching of the positive photoresist layer 30 between two adjacent circuit layers 20 can be achieved, which is extremely efficient and low-cost.

[0102] Moreover, after the prior art physically punches holes in the PCB board, it is very easy for debris to remain in the holes and cause blockage, resulting in the inability of two adjacent circuit layers to be effectively connected. In the multi-layer circuit board 100 prepared by the method provided in the embodiment of the present application, the electrical connection between the two adjacent circuit layers 20 is achieved through a plurality of through holes 31 filled with metal material in the positive photoresist layer 30. Since the portion of the positive photoresist layer 30 corresponding to the through hole 31 can be completely developed in the photolithography process, it is not easy for the through hole 31 penetrating the positive photoresist layer 30 to retain debris and cause blockage, so that the two adjacent circuit layers 20 can be effectively connected.

[0103] Moreover, it is difficult to ensure the uniformity of the aperture size by physically punching holes in PCB boards using the prior art, but Mini LED and Micro LED have extremely strict requirements on the aperture of the through holes between circuit layers. Any deviation in the aperture size will cause a deviation in the display effect. In the multilayer circuit board 100 provided by the embodiment of the present application, the electrical connection between two adjacent circuit layers 20 is achieved through a plurality of through holes 31 filled with metal material in the positive photoresist layer 30. Since the aperture of the through holes 31 in the positive photoresist layer 30 can be controlled by the photoresist pattern in the photolithography process, a plurality of through holes 31 with uniform aperture can be formed in the positive photoresist layer 30, and the aperture size of the through holes 31 can be smaller, which is beneficial to improving the display effect of Mini LED and MicroLED and realizing miniaturized design.

[0104] In addition, due to the large thickness of the PCB board, the thickness of the existing multi-layer circuit board is large, which is not conducive to a lightweight design. In the multi-layer circuit board 100 manufactured using the method provided in the embodiment of the present application, there is a positive photoresist layer 30 between adjacent circuit layers 20, and the thickness of the positive photoresist layer 30 can be set according to demand, which is conducive to achieving a lightweight design.

[0105] In the embodiment of the present application, the metal material filled in the through hole 31 in the positive photoresist layer 30 may be copper (Cu) metal, but the present application does not limit this. The metal material filled in the through hole 31 in the positive photoresist layer 30 may also be other metals besides copper (Cu) metal.

[0106] In the embodiment of the present application, the circuit patterns between different circuit layers 20 may be the same or different, depending on the specific situation.

[0107] In the embodiment of the present application, the substrate 10 may be a PCB board, a glass substrate, or a substrate made of other materials, depending on the specific circumstances.

[0108] Since the PCB board is easily deformed at high temperatures, and the glass substrate is resistant to high temperatures, optionally, in one embodiment of the present application, the substrate 10 is a glass substrate, so that the multi-layer circuit board 100 can be resistant to high temperatures. When a metal film layer is deposited on the glass substrate 10 to form the circuit layer 20, there is a problem that the glass substrate 10 (insulating film layer) and the metal film layer are difficult to effectively combine, so that the circuit layer 20 is easy to fall off. Therefore, on the basis that the substrate 10 is a glass substrate, optionally, in one embodiment of the present application, before step S2, that is, on the basis of the substrate structure shown in FIG. 5(a), the method further includes:

[0109] S8: As shown in FIG. 6( a ), a first primer layer 40 is deposited on one side of the substrate 10 .

[0110] At this time, step S2 includes:

[0111] As shown in FIG. 6( b ), a metal film layer 21 is deposited on the side of the first base layer 40 facing away from the substrate 10 .

[0112] In step S3, as shown in FIG6(c), a negative photoresist layer 60 is coated on the side of the metal film layer 21 facing away from the substrate 10, the negative photoresist layer 60 is exposed using a preset first photomask, and the exposed negative photoresist layer 60 is developed to form a preset pattern in the negative photoresist layer 60.

[0113] In step S4, as shown in FIG6(d), the metal film layer 21 is etched using the negative photoresist layer 60 having a preset pattern as a mask to form the first circuit layer 20. At the same time, the first base layer 40 is etched so that the first base layer 40 is bonded to the substrate 10 and the first circuit layer 20, and the negative photoresist layer 60 is removed.

[0114] In step S5 , as shown in FIG. 6( e ), a positive photoresist layer 30 is coated, the positive photoresist layer 30 is exposed using a preset second photomask, and the exposed positive photoresist layer 30 is developed to form a plurality of penetrating through holes 31 in the positive photoresist layer 30 .

[0115] In step S6 , as shown in FIG. 6( f ), a metal film layer 21 is deposited on the side of the positive photoresist layer 30 facing away from the substrate 10 , so that the through hole 31 is filled with metal material.

[0116] In step S7, the process returns to step S3-S4. Specifically, a negative photoresist layer 60 is coated on the side of the metal film layer 21 facing away from the substrate 10, and the negative photoresist layer 60 is exposed using a preset first photomask. The exposed negative photoresist layer 60 is developed to form a preset pattern on the negative photoresist layer 60. Then, the metal film layer 21 is etched using the negative photoresist layer 60 having the preset pattern as a mask to form a circuit layer 20, and the negative photoresist layer 60 is removed to obtain the following. Figure 2 The structure of the multi-layer wiring board 100 is shown.

[0117] It should be noted that Figure 2 Two circuit layers 20 are taken as an example for demonstration, and the specific number of circuit layers 20 can be set according to actual needs.

[0118] Based on the above embodiment, optionally, in one embodiment of the present application, the first coating layer 40 is a mixed material layer of zirconium metal (Zr) and indium tin oxide (ITO). The inventor verified through experiments that when the first coating layer 40 is a mixed material layer of zirconium metal (Zr) and indium tin oxide (ITO), the glass substrate 10 and the first circuit layer 20 can be effectively combined.

[0119] It should be noted that, in the actual process of manufacturing the multi-layer circuit board 100, when the positive photoresist layer 30 is coated on the circuit layer 20, the circuit layer 20 and the positive photoresist layer 30 are well combined, and when the metal film layer is sputtered and deposited on the positive photoresist layer 30 to manufacture the circuit layer, due to the high sputtering temperature, the metal film layer sputtered and deposited on the positive photoresist layer 30 has insufficient adhesion. In order to prevent the circuit layer 20 deposited on the positive photoresist layer 30 from falling off, optionally, in one embodiment of the present application, before each step S6 is performed, that is, on the basis of the structure shown in FIG. 5(h) or FIG. 6(e), the following description is based on the structure shown in FIG. 6(e), and the method further includes:

[0120] S9: As shown in FIG. 7( a ), a second primer layer 50 is deposited on the side of the positive photoresist layer 30 facing away from the substrate 10 , and the sidewall of the through hole 31 is covered with the second primer layer 50 . At this time, the circuit layer 20 exposed by the through hole 31 is also covered with the second primer layer 50 .

[0121] At this time, step S6 includes:

[0122] As shown in FIG. 7( b ), a metal film layer 21 is deposited on the side of the second base layer 50 facing away from the substrate 10 , so that the through hole 31 is filled with metal material.

[0123] In step S7, the process returns to step S3-S4. Specifically, as shown in FIG. 7(c), a negative photoresist layer 60 is coated on the side of the metal film layer 21 facing away from the substrate 10, and the negative photoresist layer 60 is exposed using a preset first photomask. The exposed negative photoresist layer 60 is developed to form a preset pattern on the negative photoresist layer 60. Then, as shown in FIG. Figure 3 As shown, the negative photoresist layer 60 having a preset pattern is used as a mask to etch the metal film layer 21 to form the i+1th circuit layer 20 (eg Figure 3 At the same time, the second bottom layer 50 is also etched to make the second bottom layer 50 adhere to the positive photoresist layer 30 and the i+1th circuit layer 20 (for example Figure 3 The positive photoresist layer 30 and the (i+1)-th circuit layer 20 are effectively combined to prevent the (i+1)-th circuit layer 20 from falling off from the positive photoresist layer 30.

[0124] Furthermore, considering that the positive photoresist layer 30 between two adjacent circuit layers 20 is made of a liquid substrate, the positive photoresist layer 30 will contain more or less moisture. In particular, after the multi-layer circuit board 100 is manufactured, a constant temperature and humidity test is usually required. If the positive photoresist layer 30 is not protected from water, some moisture will inevitably recombine with the positive photoresist layer 30 during the constant temperature and humidity test. Therefore, in the present embodiment, the second primer layer 50 provided between the positive photoresist layer 50 and the i+1th circuit layer 20 can not only effectively combine the positive photoresist layer 30 and the i+1th circuit layer 20, but also serve as a waterproof film layer for the positive photoresist layer 30 to prevent the positive photoresist layer 30 from being penetrated by moisture and impacting and damaging the i+1th circuit layer 20.

[0125] It should be noted that Figure 3 The two-layer circuit layer 20 is used as an example for demonstration, and the specific number of circuit layers 20 can be set according to actual needs. Figure 3 As shown, when the second primer layer 50 is deposited on the positive photoresist layer 30, the second primer layer 50 will cover the side walls of the through hole 31 and the exposed circuit layer 20 of the through hole 31. Then, when the metal film layer is deposited to fill the through hole 31 and prepare the circuit layer 20, the metal material filled in the through hole 31 and the positive photoresist layer 30 are also bonded together by the second primer layer 50, and the positive photoresist layer 30 is prevented from being penetrated by moisture and impacting and damaging the i+1th circuit layer 20.

[0126] It should also be noted that Figure 3 The through hole 31 is shown to be filled with metal material, but the present application does not limit whether the through hole 31 is filled with metal material. In fact, the metal material filled in the through hole 31 only needs to electrically connect the upper and lower circuit layers.

[0127] On the basis of the above-mentioned embodiment, optionally, in one embodiment of the present application, the second primer layer 50 is a mixed material layer of aluminum (Al) metal and chromium (Cr) metal. The inventor verified through experiments that since the positive photoresist layer 30 contains more or less moisture inside, and the metal film layer needs to be plated under vacuum when depositing on the positive photoresist layer 30, and it is very difficult to find a primer material that can be effectively combined with the positive photoresist layer 30 containing moisture during the vacuum coating process, in this embodiment, when the second primer layer 50 is a mixed material layer of aluminum (Al) metal and chromium (Cr) metal, the positive photoresist layer 30 can be effectively combined with the i+1th circuit layer 20, preventing the i+1th circuit layer 20 from falling off from the positive photoresist layer 30.

[0128] Moreover, in the present embodiment, since the chromium (Cr) metal surface is easily passivated and has strong anti-oxidation ability and strong corrosion resistance, and since the aluminum (Al) metal surface is easy to form an Al2O3 passivation layer and has excellent gas barrier and moisture barrier properties, the second base layer 50 is a mixed material layer of aluminum (Al) metal and chromium (Cr) metal, which can have a good barrier effect against oxygen and water vapor, and effectively prevent moisture from damaging the positive photoresist layer 30, thereby having a good protective effect on the positive photoresist layer 30.

[0129] Based on any of the above embodiments, since the aperture of the through hole in the positive photoresist layer can be controlled by the photoresist pattern in the photolithography process, optionally, in one embodiment of the present application, Figure 2 and Figure 3 As shown, the aperture d of the through hole penetrating the positive photoresist layer is less than 100 μm, while the physical drilling of the PCB board in the prior art cannot realize a through hole with such a small aperture size.

[0130] The embodiment of the present application further provides a display module 1000, Figure 8 1 shows a schematic diagram of the structure of the display module 1000 provided in the embodiment of the present application. Figure 8 As shown, the display module 1000 includes a driving component 200, a multi-layer circuit board 100 and a plurality of LED chips 300, and the multi-layer circuit board 100 is any of the multi-layer circuit boards described above.

[0131] Among them, the driving component 200 is electrically connected to one or more circuit layers 20 in the multi-layer circuit board 100, the Nth circuit layer 20 in the multi-layer circuit board 100 is electrically connected to multiple LED chips 300, and the driving component 200 drives the multiple LED chips 300 to emit light through the multi-layer circuit board 100.

[0132] Since the multilayer wiring board 100 has been described in detail in the above embodiments, it will not be described again here.

[0133] In summary, the multilayer circuit board and its manufacturing method and display module provided in the embodiments of the present application are different from the existing multilayer circuit board in which the electrical connection between two adjacent circuit layers is achieved by physically punching a PCB board. The electrical connection between two adjacent circuit layers in the multilayer circuit board is achieved through a plurality of through holes filled with metal materials in the positive photoresist layer. Since the plurality of penetrating through holes in the positive photoresist layer can be formed in batches through a single photolithography process, the positive photoresist layer between two adjacent circuit layers can be punched in batches, which is highly efficient and low-cost. Moreover, the penetrating through holes in the positive photoresist layer are not prone to residual debris, so that the two adjacent circuit layers can be effectively connected, and the aperture of the through hole is relatively uniform, and the aperture size can be smaller, which is beneficial to improving the display effect of Mini LED and Micro LED and realizing miniaturization and thin design.

[0134] The various parts in this manual are described in a combination of parallel and progressive ways. Each part focuses on the differences from other parts, and the same or similar parts between the various parts can be referenced to each other.

[0135] With respect to the above description of the disclosed embodiments, the features described in the embodiments in this specification may be replaced or combined with each other, so that professionals in the field can implement or use the present application. Various modifications to these embodiments will be apparent to professionals in the field, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multilayer circuit board, characterized in that: include: substrate; A multi-layer circuit layer located on one side of the substrate, the multi-layer circuit layer includes a 1st circuit layer to an Nth circuit layer arranged in sequence along a direction away from the substrate, wherein a positive photoresist layer is arranged between the i-th circuit layer and the i+1-th circuit layer, the positive photoresist layer is made of a liquid substrate, the positive photoresist layer has a plurality of through holes, and the through holes are filled with a metal material to electrically connect the i-th circuit layer and the i+1-th circuit layer, 1≤i≤N-1, N≥2; A second primer layer is further provided between the i-th circuit layer and the i+1-th circuit layer, the second primer layer is located on a side of the positive photoresist layer close to the i+1-th circuit layer, the second primer layer is used to bond the positive photoresist layer and the i+1-th circuit layer, and also serves as a waterproof film layer of the positive photoresist layer; the second primer layer is a mixed material layer of aluminum metal and chromium metal; The substrate is a glass substrate, and a first primer layer is provided between the substrate and the first circuit layer, and the first primer layer is used to bond the substrate and the first circuit layer; the first primer layer is a mixed material layer of zirconium metal and indium tin oxide.

2. The multilayer circuit board according to claim 1, characterized in that: The diameter of the through hole penetrating the positive photoresist layer is less than 100 μm.

3. A method for manufacturing a multilayer circuit board, characterized in that: include: S1: providing a substrate; S2: depositing a metal film layer on one side of the substrate; S3: coating a negative photoresist layer on the side of the metal film layer facing away from the substrate, exposing the negative photoresist layer using a preset first photomask, and developing the exposed negative photoresist layer to form a preset pattern on the negative photoresist layer; S4: using the negative photoresist layer with a preset pattern as a mask, etching the metal film layer to form a circuit layer, and removing the negative photoresist layer; S5: coating a positive photoresist layer with a liquid substrate, baking the positive photoresist layer, expelling moisture from the positive photoresist layer, exposing the positive photoresist layer with a preset second photomask, and developing the exposed positive photoresist layer to form a plurality of through holes in the positive photoresist layer; S6: depositing another metal film layer on the side of the positive photoresist layer facing away from the substrate, so that the through hole is filled with metal material; S7: Return to step S3-S4, and form another circuit layer on the side of the positive photoresist layer facing away from the substrate; Steps S5 to S7 are performed N-1 times until N circuit layers are formed on one side of the substrate and arranged in sequence in a direction away from the substrate, and the i-th circuit layer and the i+1-th circuit layer are electrically connected through a through hole filled with a metal material in the positive photoresist layer therebetween, 1≤i≤N-1, N≥2; The substrate is a glass substrate. Before step S2, the method further includes: S8: depositing a first primer layer on one side of the substrate; Step S2 includes: Depositing a metal film layer on the side of the first bottom layer away from the substrate; In step S4, when the metal film layer is etched to form the first circuit layer, the first primer layer is etched at the same time so that the first primer layer adheres to the substrate and the first circuit layer; the first primer layer is a mixed material layer of zirconium metal and indium tin oxide; Before each step S6 is performed, the method further comprises: S9: depositing a second primer layer on the side of the positive photoresist layer facing away from the substrate, and covering the sidewall of the through hole with the second primer layer; Step S6 includes: Depositing a metal film layer on the side of the second bottom layer away from the substrate so that the through hole is filled with metal material; In step S4, when the metal film layer is etched to form the i+1th circuit layer, the second base layer is etched at the same time, so that the second base layer adheres to the positive photoresist layer and the i+1th circuit layer, and the second base layer also serves as a waterproof film layer of the positive photoresist layer; the second base layer is a mixed material layer of aluminum metal and chromium metal.

4. A display module, characterized in that: It comprises a driving component, a multi-layer circuit board and a plurality of LED chips, wherein the multi-layer circuit board is the multi-layer circuit board according to claim 1 or 2; Among them, the driving component is electrically connected to one or more circuit layers in the multi-layer circuit board, the Nth circuit layer in the multi-layer circuit board is electrically connected to the multiple LED chips, and the driving component drives the multiple LED chips to emit light through the multi-layer circuit board.

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