Multilayer circuit board and preparation method thereof

Abstract

The invention discloses a multilayer circuit board and a preparation method thereof. The multilayer circuit board comprises a copper plate; the copper plate comprises two opposite surfaces; a copper layer stacking structure is arranged on any surface of the copper plate, the copper layer stacking structure comprises a second copper layer and at least one first copper layer, and the at least one first copper layer is located between the copper plate and the second copper layer; the first copper layer is provided with a first groove, the first groove penetrates through the first copper layer, the first groove is filled with a semi-cured material, the opening of the first groove is gradually increased along a first direction, and the first direction is a direction from the second copper layer to the copper plate. By adopting the technical scheme, the sectional area of the first copper layer can be maximized to improve the heat dissipation efficiency under the condition that the wiring structure of the second copper layer is not influenced.

Description

Technical Field

[0001] The present invention relates to the technical field of multilayer circuit boards, and in particular to a multilayer circuit board and a preparation method thereof. Background Art

[0002] With the advent of the big data era, the market demand for power management integrated circuits is becoming more and more widespread, and the problem of heat generation caused by high-speed computing is receiving more and more attention. Due to the requirements of smaller and smaller space layouts, the heat dissipation problem is more prominent, and the design of substrates tends to design thicker copper and more layers to ensure heat dissipation.

[0003] However, due to space limitations, existing circuit boards cannot reserve more heat dissipation copper space, resulting in poor heat dissipation effect. Summary of the invention

[0004] The invention provides a multi-layer circuit board and a preparation method thereof, so as to solve the problem of poor heat dissipation effect of the existing circuit board.

[0005] According to one aspect of the present invention, a multilayer circuit board is provided, comprising: a copper plate; the copper plate comprising two opposite surfaces; a copper layer stacking structure is arranged on any one surface of the copper plate, the copper layer stacking structure comprising a second copper layer and at least one first copper layer, the at least one first copper layer being located between the copper plate and the second copper layer; a first groove is opened in the first copper layer, the first groove passes through the first copper layer, the first groove is filled with a semi-cured material, and the opening of the first groove gradually increases along a first direction, the first direction being the direction in which the second copper layer points to the copper plate.

[0006] Optionally, the first groove includes a bottom opening close to the copper plate and a top opening away from the copper plate;

[0007] Along a second direction, a difference between a size of the top opening and a size of the bottom opening is greater than 50 μm, and the second direction is parallel to a radial direction of the groove.

[0008] Optionally, a plurality of second grooves are formed on a side of the second copper layer facing away from the copper plate, and at least one of the second grooves overlaps with the first groove in the first direction.

[0009] Optionally, the copper layer stacking structure includes N layers of the first copper layers stacked, N being greater than 1, wherein the first layer of the first copper layer is close to the copper plate, and the Nth layer of the first copper layer is close to the second copper layer;

[0010] The N layer and the first copper layer meet at least one of the following conditions:

[0011] 1) Along the second direction, the size of the first groove of the first copper layer of the i-th layer is smaller than the size of the first groove of the first copper layer of the N-th layer, and the second direction is parallel to the radial direction of the groove, 1≤i≤(N-1);

[0012] 2) the central axes of the first grooves of at least two layers of the first copper layers coincide with each other;

[0013] 3) The first grooves of at least two layers of the first copper layers have the same size.

[0014] Optionally, the surface flatness of the copper layer stacking structure is less than 0.008 mm.

[0015] Optionally, the copper plate is provided with a third groove, the third groove is filled with resin material, and along the first direction, a projection of at least one of the first grooves covers a projection of the third groove.

[0016] Optionally, along a third direction, the copper layer stacking structure includes at least a first side surface, the first side surface is serrated, a semi-cured layer is disposed on the first side surface, and the third direction is parallel to a plane where the copper plate is located.

[0017] According to another aspect of the present invention, a method for preparing a multilayer circuit board is provided, which is used to prepare the multilayer circuit board according to any embodiment of the present invention, and the preparation method comprises:

[0018] Provide copper plates;

[0019] Forming a plurality of semi-cured material blocks on the copper plate, wherein the semi-cured material blocks are in a regular trapezoidal shape along a first direction;

[0020] forming a first copper layer on the plurality of semi-cured material blocks, wherein the first copper layer is flush with the semi-cured material blocks;

[0021] A second copper layer is formed on the first copper layer.

[0022] Optionally, forming a plurality of semi-cured material blocks on the copper plate comprises:

[0023] A semi-cured film layer and a thin copper layer are sequentially formed on the copper plate and patterned, and a thin copper material block is provided on the semi-cured material block.

[0024] Optionally, forming a first copper layer on the plurality of semi-cured material blocks comprises:

[0025] Forming a first copper film layer by electroplating, wherein the thickness of the first copper film layer is greater than or equal to the thickness of the semi-cured material block;

[0026] The first copper film layer is thinned until the thin copper material block is removed.

[0027] The technical solution of the embodiment of the present invention is to set a copper layer stacking structure on the surface of the copper plate, so that the first copper layer and at least one second copper layer are stacked, and a first groove is opened in the first copper layer so that the first copper layer presents an inverted trapezoidal structure. The first copper layer stacking setting of the inverted trapezoidal structure can avoid the problem of interlayer alignment, thereby increasing the cross-sectional area of ​​the copper layer stacking structure, and the copper layer stacking structure can maximize the cross-sectional area of ​​the first copper layer without affecting the wiring structure of the second copper layer, thereby increasing the cross-sectional area of ​​the copper layer stacking structure and improving the heat dissipation efficiency. In addition, the copper layer stacking structures on the two surfaces of the copper plate that are relatively arranged are symmetrically distributed along the copper plate, which increases the symmetry of the multi-layer circuit board and further improves the heat dissipation effect.

[0028] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 is a schematic diagram of the structure of a first multi-layer circuit board provided according to an embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of the structure of a second multi-layer circuit board provided according to an embodiment of the present invention;

[0032] Figure 3 It is a schematic diagram of a conventional multi-layer circuit board structure;

[0033] Figure 4 is a schematic diagram of a first copper layer stacking structure provided according to an embodiment of the present invention;

[0034] Figure 5 is a schematic diagram of a second copper layer stacking structure provided according to an embodiment of the present invention;

[0035] Figure 6 is a schematic flow chart of a method for preparing a display panel provided according to an embodiment of the present invention;

[0036] Figure 7 It is a process flow chart of a method for preparing a display panel provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0038] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, any variation of the terms "including" and "having" is intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0039] Figure 1 is a schematic diagram of a multi-layer circuit board structure provided according to an embodiment of the present invention. Figure 1 As shown, the multi-layer circuit board structure includes: a copper plate 1; the copper plate 1 includes two opposite surfaces; on any one surface of the copper plate 1, a copper layer stacking structure 2 is arranged, the copper layer stacking structure 2 includes a second copper layer 22 and at least one first copper layer 21, and the at least one first copper layer 21 is located between the copper plate 1 and the second copper layer 22; the first copper layer 21 is provided with a first groove 23, the first groove 23 penetrates the first copper layer 21, the first groove 23 is filled with semi-cured material, and the opening of the first groove 23 gradually increases along the first direction -Z, and the first direction -Z is the direction in which the second copper layer 22 points to the copper plate 1.

[0040] In this embodiment, a copper layer stacking structure 2 is provided on the upper and lower surfaces of the copper plate 1. The copper plate 1 can be selected as a thin sheet of copper foil of 3OZ to 5OZ. The first direction -Z is parallel to the thickness direction of the copper plate 1. Along the first direction -Z, the copper plate 1 has two opposite surfaces, namely a first surface 101 and a second surface 102.

[0041] A copper layer stacking structure 2 is arranged on any surface of the copper plate 1, that is, a copper layer stacking structure 2 is arranged on the first surface 101 of the copper plate 1, and a copper layer stacking structure 2 is also arranged on the second surface 102 of the copper plate 1, and the copper layer stacking structure 2 on the first surface 101 and the copper layer stacking structure 2 on the second surface 102 are symmetrically distributed along the copper plate 1.

[0042] The same-layer stacking structure 2 on the second surface 102 is taken as an example for detailed description. The copper layer stacking structure 2 includes a second copper layer 22 and at least one first copper layer 21. Figure 1 The optional copper layer stacking structure 2 includes a second copper layer 22 and a first copper layer 21. The first copper layer 21 is located between the copper plate 1 and the second copper layer 22. The first copper layer 21 is provided with a first groove 23. The first groove 23 runs through the first copper layer 21, and the first groove is filled with a semi-cured material. The semi-cured material refers to a material that is in a semi-solid state at room temperature, has a certain fluidity, and can be converted into a fully cured state after heating or cooling. Along the first direction -Z, the opening of the first groove 23 gradually increases, so that the first groove 23 presents a regular trapezoidal structure. Among them, the first direction -Z is the direction in which the second copper layer 22 points to the copper plate 1. Based on the above structure, the first copper layer 21 can present an inverted trapezoidal structure.

[0043] refer to Figure 2 The optional copper layer stack structure 2 includes at least one first copper layer 21 and one second copper layer 22 . Figure 2 The optional copper layer stacking structure 2 includes three layers of first copper layers 21, which are located between the copper plate 1 and the second copper layer 22, and are respectively the first layer of the first copper layer a, the second layer of the first copper layer b and the third layer of the first copper layer c. A first groove 23 is provided on each of the three layers of the first copper layer 21, and the first groove 23 runs through the first copper layer 21. The first groove 23 is filled with a semi-cured material, and the semi-cured material has an insulating property. By filling the semi-cured material in the through-type first groove 23, a stacked semi-cured layer structure is formed, and the stacked first copper layer 21 is divided into two partitions. The advantage of this is that the heat dissipation can be performed in partitions, further increasing the heat dissipation effect. The opening of the first groove 23 along the first direction -Z gradually increases so that the first groove 23 is a positive trapezoidal structure. Matching the positive trapezoidal structure of the first groove 23 is a multi-layer three-layer first copper layer 21 that is an inverted trapezoidal structure. The advantage of this arrangement is that the trapezoidal structure has better symmetry, which can make the heat dissipation more uniform and further improve the heat dissipation efficiency.

[0044] In addition, the third first copper layer c is in contact with the second copper layer 22, and the second copper layer 22 is limited by the surface wiring, and its cross-sectional area needs to be adjusted according to the surface wiring. Based on this, the cross-sectional area of ​​the third first copper layer c is affected by the second copper layer 22, while the second first copper layer b and the first first copper layer a are not subject to the above restrictions, and their cross-sectional areas can be made as large as possible to increase the cross-sectional area of ​​the copper layer stacking structure 2 and thus increase the heat dissipation effect.

[0045] Figure 3 This is a schematic diagram of a conventional multi-layer circuit board structure. Figure 3 As shown, there are three first copper layers 21 on one surface of the copper plate 1, wherein the first copper layers 21 are rectangular structures.

[0046] and Figure 2 compared to, Figure 2 The copper layer stacking structure 2 has a larger cross-sectional area and a better heat dissipation effect. Figure 3 As shown, when the first copper layer 21 is a rectangular structure, the long side of the second first copper layer b needs to be longer than the long side of the first first copper layer a to ensure interlayer alignment. However, such a structure will make the cross-sectional area of ​​the second first copper layer b smaller than the cross-sectional area of ​​the first first copper layer a. In the embodiment of the invention, the first copper layer 21 of the inverted trapezoidal structure is set, and it is only necessary that the long bottom side of the first copper layer 21 is longer than the short bottom side, so that the cross-sectional area of ​​the second first copper layer b and the first first copper layer a are the same, while meeting the interlayer alignment requirements, the cross-sectional area of ​​the copper layer stacking structure 2 is increased.

[0047] In the embodiment of the present invention, a copper layer stacking structure is arranged on the surface of a copper plate, so that a first copper layer and at least one second copper layer are stacked, and a first groove is opened in the first copper layer so that the first copper layer presents an inverted trapezoidal structure. The stacking arrangement of the first copper layer with an inverted trapezoidal structure can avoid the problem of interlayer alignment, thereby increasing the cross-sectional area of ​​the copper layer stacking structure, and the copper layer stacking structure can maximize the cross-sectional area of ​​the first copper layer without affecting the wiring structure of the second copper layer, thereby increasing the cross-sectional area of ​​the copper layer stacking structure and improving the heat dissipation efficiency. In addition, the copper layer stacking structures on the two surfaces of the copper plate that are arranged relatively are symmetrically distributed along the copper plate, which increases the symmetry of the multi-layer circuit board and further improves the heat dissipation effect.

[0048] In addition, the flatness of the surface of the copper layer stack structure 2 in the present application is less than 0.008 mm, and at least one first copper layer 21 is greater than 0.1 mm. In other words, Figure 2 As shown, when there are three first copper layers 21, the thickness of the three first copper layers 21 stacked together is greater than 0.1 mm.

[0049] The optional first groove 23 includes a bottom opening close to the copper plate 1 and a top opening away from the copper plate 1; along the second direction X, the difference between the size of the top opening and the size of the bottom opening is greater than 50 μm, and the second direction X is parallel to the radial direction of the groove.

[0050] Specifically, Figure 2 As shown, the first groove 23 is a regular trapezoidal structure, the bottom opening 231 of the first groove 23 is the short bottom side of the trapezoidal structure, the top opening 232 of the first groove 23 is the long bottom side of the trapezoidal structure, and the difference between the size Wa of the top opening and the size Wb of the bottom opening 231 is greater than 50 μm. In other words, the long bottom side of the trapezoidal structure is about 50 μm longer than the short bottom side.

[0051] The regular trapezoidal shape of the optional first groove is an isosceles trapezoid. Due to the symmetry of the trapezoidal structure, the long base is 25 μm longer than the short base, and correspondingly, the long base of the first copper layer 21 of the inverted trapezoidal structure is 25 μm longer than the short base.

[0052] In the process of circuit board manufacturing, considering the problem of inter-layer alignment, the latter layer is 25μm smaller than the previous layer on one side. This is an important pre-compensation measure to offset the natural expansion of electroplated copper and ensure the inter-layer alignment of multi-layer circuit boards.

[0053] It should be noted that the third-layer first copper layer 211 is affected by the wiring structure on the second copper layer 22 and is usually not on the same central axis as the second-layer first copper layer 212 and the first-layer first copper layer 211. Therefore, the interlayer alignment problem between it and the second-layer first copper layer 212 can be ignored.

[0054] In the embodiment of the present invention, the difference between the size of the top opening and the size of the bottom opening of the first groove is set to be greater than 50 μm, so that the long bottom side of the matching first copper layer is 25 μm longer than the short bottom side, thereby avoiding the problem of inter-layer alignment, thereby maximizing the cross-sectional area of ​​the first copper layer.

[0055] The second groove structure is described in the embodiment of the present invention. Figure 2 As shown, a plurality of second grooves 24 are formed on the side of the second copper layer 22 facing away from the copper plate 1 , and at least one of the second grooves 24 overlaps with the first groove 23 in the first direction −Z.

[0056] Specifically, the second groove 24 is a circuit structure generated by patterning the second copper layer 22 after the second copper layer 22 is manufactured. By arranging the second groove 24 to overlap with the first groove 23 in the first direction -Z, the problem of signal crosstalk caused by direct contact between the circuit wiring on the second copper layer 22 and the first copper layer 21 is avoided.

[0057] This embodiment further describes the first copper layer in the copper layer stacking structure. The copper layer stacking structure includes N first copper layers stacked, N is greater than 1, wherein the first first copper layer is close to the copper plate, and the Nth first copper layer is close to the second copper layer;

[0058] The first copper layer of the N layer meets at least one of the following conditions:

[0059] 1) Along the second direction, the size of the first groove of the i-th first copper layer is smaller than the size of the first groove of the N-th first copper layer, the second direction is parallel to the radial direction of the groove, 1≤i≤(N-1);

[0060] 2) the central axes of the first grooves of at least two first copper layers coincide with each other;

[0061] 3) The first grooves of at least two first copper layers have the same size.

[0062] The following describes different situations of the first peer layer through multiple embodiments.

[0063] Figure 4 Schematic diagram of the first copper layer stacking structure provided according to an embodiment of the present invention. Figure 4 As shown, N layers of first copper layers 21 may optionally satisfy the following conditions: along the second direction X, the size of the first groove 23 of the i-th first copper layer 21 is smaller than the size of the first groove 23 of the N-th first copper layer 21, the second direction X is parallel to the radial direction of the groove, 1≤i≤(N-1); the sizes of the first grooves 23 of at least two layers of first copper layers 21 are the same.

[0064] Specifically, Figure 4 As shown, i is equal to 1 for example, and N can be equal to 2 at this time. The first groove 23 on the first copper layer 21 of the first layer is smaller than the size of the first groove 23 of the second copper layer 21. This is because the cross-sectional area of ​​the second copper layer 21 is limited by the distribution of the circuits on the second copper layer 22, so that the cross-sectional area of ​​the second copper layer 21 is relatively small. Accordingly, the size of the first groove 23 on the second copper layer 21 is larger; while the cross-sectional area of ​​the first copper layer 21 of the first layer is not limited, and at this time, the entire space of the copper layer can be filled as much as possible, so that the first copper layer 21 is maximized. Accordingly, the size of the first groove 23 on the first copper layer 21 of the first layer is smaller. In this way, by fully utilizing the space of the first copper layer 21 of the first layer, the cross-sectional area of ​​the first copper layer 21 is increased, thereby increasing the heat dissipation efficiency. In addition, the first groove 23 on the first copper layer 21 of the first layer coincides with the central axis of the first groove 23 of the second copper layer 21, so that the first copper layer 21 is symmetrically distributed with the central axis of the first groove 23 as the symmetry axis, increasing the symmetry of the first copper layer 21, making the heat dissipation more uniform and further improving the heat dissipation effect.

[0065] Figure 5 Schematic diagram of a second copper layer stacking structure provided according to an embodiment of the present invention. Figure 5 As shown, the N first copper layers 21 satisfy the following conditions: the central axes of the first grooves 23 of at least two first copper layers 21 coincide with each other; and the sizes of the first grooves 23 of at least two first copper layers 21 are the same.

[0066] like Figure 5As shown, two identical first copper layers 21 are taken as an example for explanation, the central axes of the first grooves 23 of the two first copper layers 21 coincide with each other and the sizes of the first grooves 23 of the two first copper layers 21 are the same, and the central axes of the two first grooves 23 coincide with each other, thereby increasing the symmetry of the first copper layer 21, and the first grooves 23 are of a regular trapezoidal structure, so that the two first copper layers 21 matched therewith can be of an inverted trapezoidal structure, thereby increasing the cross-sectional area of ​​the first copper layer 21 while satisfying the interlayer alignment requirement between the two first copper layers 21.

[0067] like Figure 2 As shown, N first copper layers 21 satisfy the following conditions: 1) along the second direction X, the size of the first groove 23 of the i-th first copper layer 21 is smaller than the size of the first groove 23 of the N-th first copper layer 21, the second direction X is parallel to the radial direction of the groove, 1≤i≤(N-1); 2) the central axes of the first grooves 23 of at least two first copper layers 21 coincide; 3) the sizes of the first grooves 23 of at least two first copper layers 21 are the same.

[0068] Specifically, for case 1), take i=2 as an example, in which case N is equal to 3, along the second direction X, the size of the first groove 23 of the first copper layer 21 of the second layer is smaller than the size of the first groove 23 of the first copper layer 21 of the third layer; for case 2), the central axes of the first grooves 23 of the first layer, the second layer, and the third layer coincide; for case 3), the sizes of the first grooves 23 of the first layer and the second layer are the same. Therefore, Figure 2 The copper layer stacking structure 2 in the copper layer stacking structure 2 shown can meet the above three conditions. Therefore, the copper layer stacking structure 2 has good symmetry and more uniform heat dissipation, cleverly avoids the problem of reduced cross-sectional area caused by inter-layer alignment, and makes full use of the space of the first copper layer 21 to maximize the cross-sectional area of ​​the copper layer stacking structure 2, thereby increasing heat dissipation efficiency.

[0069] The embodiment of the present invention describes the case where the copper plate is divided into two parts. Figure 2 As shown, the copper plate 1 is provided with a third groove 3, and the third groove 3 is filled with resin material. Along the first direction -Z, the projection of at least one first groove 23 covers the projection of the third groove.

[0070] Specifically, Figure 2As shown, there is a third groove 3 on the copper plate 1. The third groove 3 penetrates the copper plate 1 in order to divide the copper plate 1 into two parts to achieve zoned heat dissipation. The third groove 3 is filled with a resin material, wherein the resin material may be an epoxy resin. The resin material has insulating properties that can insulate the two parts of the copper plate 1 from each other. Along the first direction -Z, the projections of the three first copper layers 21 all cover the projection of the third groove, so that the third groove 3 and the first groove 23 together divide the first copper layer on the surface of the copper plate 1 into two equally divided zones, thereby avoiding heat concentration for zoned heat dissipation and further improving the heat dissipation efficiency.

[0071] In an embodiment of the present invention, a third groove is provided on a copper plate, and the third groove is filled with resin material to divide the copper plate into two equal parts, and the projection of at least one first groove covers the projection of the third groove, so that the first groove and the third groove divide the first copper layer and the copper plate into two equal parts for partitioned heat dissipation to improve the heat dissipation effect.

[0072] Based on the above embodiment, this embodiment describes the arrangement of a semi-cured layer on the first side surface of the copper layer stack structure, along the third direction -X, such as Figure 2 As shown, the copper layer stacking structure 2 at least includes a first side surface 4, the first side surface 4 is serrated, a semi-cured layer 5 is arranged on the first side surface 4, and the third direction -X is parallel to the plane where the copper plate 1 is located.

[0073] Specifically, Figure 2 As shown, along the third direction -X, the first side surface 4, that is, the edge of the three-layer stacked first copper layer 21, since the three-layer first copper layer 21 are all inverted trapezoidal structures, the edge of the three-layer stacked first copper layer 21 is serrated, and a matching semi-cured layer 5 is arranged on the first side surface 4 to prevent the edge of the first copper layer 21 from being directly exposed, thereby protecting the first copper layer 21.

[0074] In the embodiment of the present invention, a semi-cured layer is disposed on the side wall of the first surface 101 to protect the first copper layer 21 and prevent it from being directly exposed, thereby enhancing the overall performance of the circuit board.

[0075] Based on the above inventive concept, an embodiment of the present invention further provides a method for preparing a multi-layer circuit board. Figure 6 is a schematic flow chart of a method for preparing a display panel according to an embodiment of the present invention, such as Figure 6 As shown, the method for preparing the display panel includes:

[0076] S110, provide copper plate;

[0077] S120, forming a plurality of semi-cured material blocks on the copper plate;

[0078] S130, forming a first copper layer on the plurality of semi-cured material blocks;

[0079] S140, forming a second copper layer on the first copper layer.

[0080] The preparation method can be applied to manufacture the display panel described in any of the above embodiments.

[0081] The embodiment of the present invention provides a copper plate, forms multiple semi-cured material blocks on the copper plate, forms a first copper layer on the multiple semi-cured material blocks, and then forms a second copper layer on the first copper layer to manufacture a multi-layer circuit board. The multi-layer circuit board has good symmetry and more uniform heat dissipation, cleverly avoids the problem of reduced cross-sectional area caused by inter-layer alignment, fully utilizes the space of the first copper layer to maximize the cross-sectional area of ​​the copper layer stacking structure, and increases the heat dissipation efficiency of the multi-layer circuit board.

[0082] The following will be described through a specific preparation scheme. Figure 6 The preparation method shown is described in detail. Figure 7 It is a process flow chart of a method for preparing a display panel provided according to an embodiment of the present invention. Figure 7 As shown, the preparation method comprises:

[0083] S110. Provide a copper plate.

[0084] The embodiment of the present invention manufactures the circuit board through the advanced printed circuit board manufacturing process Modified Semi-Additive Process (MSAP). The copper plate 1 can be 3OZ to 5OZ copper foil, which represents a copper foil material with a thickness between 105 microns and 175 microns, and is often used in circuit boards with high current or requiring high conductivity. This thicker copper foil can not only carry higher current, but also has better heat dissipation performance and mechanical strength.

[0085] Optionally, after providing the copper plate 1, the copper plate 1 may be grooved to form a through groove and filled with resin material to divide the copper plate 1 into two parts. In this embodiment, the copper plate 1 is divided into two parts for illustration only. In the actual manufacturing process, the copper plate 1 may be divided into a plurality of parts according to the design requirements of the circuit board, and the specific number of parts is not limited.

[0086] S120, forming a plurality of semi-cured material blocks on the copper plate.

[0087] Wherein, along the first direction -Z, the semi-cured material block is in a right trapezoidal shape.

[0088] Optionally, a plurality of semi-cured material blocks 6 are formed on the copper plate 1 , including: sequentially forming a semi-cured film layer and a thin copper layer on the copper plate 1 , and patterning them, wherein the semi-cured material blocks 6 have thin copper material blocks 7 .

[0089] Specifically, a semi-cured material layer and a thin copper are sequentially arranged on two surfaces of the copper plate 1 that are arranged opposite to each other and pressed together to form a semi-cured film layer and a thin copper layer. Among them, the semi-cured material layer is a PP layer, which is a thin sheet material impregnated with resin and cured to an intermediate degree. Ingredients: It is mainly composed of epoxy resin, hardener, accelerator, solvent, filler, etc., and glass fiber is used as a reinforcing material. Then the semi-cured film layer is patterned, that is, laser grooves are burned on the semi-cured film layer, wherein laser groove burning refers to the process of using laser technology to make precise grooves on the surface or inside of the material. Through laser groove burning, an inverted trapezoidal blind groove is opened on the semi-cured film layer, so that the remaining semi-cured film layer forms a plurality of semi-cured material blocks 6 of regular trapezoidal shape, and at this time, the semi-cured material block 6 has a thin copper material block 7. In addition, along the first direction -Z, the projection of the semi-cured material block 6 covers the projection of the groove on the copper plate 1.

[0090] S130, forming a first copper layer on the plurality of semi-cured material blocks.

[0091] The first copper layer is flush with the semi-cured material block.

[0092] Optionally, forming the first copper layer 21 on the plurality of semi-cured material blocks 6 includes: forming a first copper film layer by electroplating, wherein the thickness of the first copper film layer is greater than or equal to the thickness of the semi-cured material block 6; and thinning the first copper film layer until the thin copper material block 7 is removed.

[0093] Specifically, it is first necessary to apply a dry film coating on the semi-cured material block 6 to prevent electroplated copper from being deposited on the semi-cured material block 6. Then, electroplating copper is filled in the inverted trapezoidal grooves formed by multiple semi-cured material blocks 6 to form a first copper film layer. The thickness of the first copper film layer formed at this time is greater than or equal to the thickness of the semi-cured material block 6. Further, the dry film can be removed by chemical stripping or spraying, and the first copper film layer and the semi-cured material block 6 are flash-etched for thinning until the thin copper material block 7 is removed to remove the rough surface of the first copper layer 21 to ensure the subsequent processing quality. Finally, the first copper layer 21 flush with the semi-cured material block 6 is formed.

[0094] It should be noted that multiple layers of the first copper layer 21 can be repeatedly formed on the copper plate 1 according to actual conditions, that is, in the present application, a semi-cured film layer can be formed by laminating a PP layer on the first copper layer 21 multiple times, and then a blind groove is formed by laser burning grooves on the semi-cured film layer, and finally a copper-filled multi-layer stacking method is performed to generate the first copper layer 21. In addition, in the process of manufacturing a multi-layer circuit board, the present application needs to perform multiple grooving to form multiple shallow blind grooves when forming the first copper layer 21 of the multi-layer stack. Compared with the existing method of making a circuit board by making a deep blind groove once, electroplating and filling copper, and grinding multiple times after electroplating, on the one hand, it can avoid the risk of residual glue at the bottom when laser deep blind grooves are formed, and on the other hand, the shallow blind grooves set in the multi-layer stacking can produce a deeper blind groove of the product. The embodiment of the present invention does not limit the number of layers of the first copper layer 21.

[0095] S140, forming a second copper layer on the first copper layer.

[0096] Specifically, the second copper layer 22, which is the outer circuit layer, is formed integrally with the first copper layer 21. Before the first copper layer 21 is formed, a dry film is firstly coated on a plurality of semi-cured material blocks 6 to pattern the outer circuits, and then copper is electroplated to form electroplated copper at locations where there is no dry film, thereby forming the second copper layer 22.

[0097] The embodiment of the present invention provides a copper plate, forms multiple semi-cured material blocks on the copper plate, forms a first copper layer on the multiple semi-cured material blocks, and then forms a second copper layer on the first copper layer to manufacture a multi-layer circuit board. The multi-layer circuit board has good symmetry and more uniform heat dissipation, cleverly avoids the problem of reduced cross-sectional area caused by inter-layer alignment, fully utilizes the space of the first copper layer to maximize the cross-sectional area of ​​the copper layer stacking structure, and increases the heat dissipation efficiency of the multi-layer circuit board. In addition, the surface flatness of the multi-layer circuit board manufactured by the above method is less than 0.008mm, and the blind groove depth is greater than 0.1mm.

[0098] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0099] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-layer circuit board, characterized in that: include: Copper plate; The copper plate includes two opposite surfaces; A copper layer stacking structure is provided on any one surface of the copper plate, wherein the copper layer stacking structure includes a second copper layer and at least one first copper layer, and the at least one first copper layer is located between the copper plate and the second copper layer; The first copper layer is provided with a first groove, which penetrates the first copper layer and is filled with semi-cured material. The opening of the first groove gradually increases along a first direction, and the first direction is the direction in which the second copper layer points to the copper plate.

2. The multilayer circuit board according to claim 1, characterized in that: The first groove includes a bottom opening close to the copper plate and a top opening away from the copper plate; Along a second direction, a difference between a size of the top opening and a size of the bottom opening is greater than 50 μm, and the second direction is parallel to a radial direction of the groove.

3. The multi-layer circuit board according to claim 1, characterized in that: A plurality of second grooves are formed on a side of the second copper layer facing away from the copper plate, and at least one of the second grooves overlaps with the first groove in the first direction.

4. The multi-layer circuit board according to claim 1, characterized in that: The copper layer stacking structure comprises N layers of the first copper layers stacked, N being greater than 1, wherein the first layer of the first copper layer is close to the copper plate, and the Nth layer of the first copper layer is close to the second copper layer; The N layer and the first copper layer meet at least one of the following conditions: 1) Along the second direction, the size of the first groove of the first copper layer of the i-th layer is smaller than the size of the first groove of the first copper layer of the N-th layer, and the second direction is parallel to the radial direction of the groove, 1≤i≤(N-1); 2) the central axes of the first grooves of at least two layers of the first copper layers coincide with each other; 3) The first grooves of at least two layers of the first copper layers have the same size.

5. The multi-layer circuit board according to claim 1, characterized in that: The surface flatness of the copper layer stacking structure is less than 0.008 mm. The at least one first copper layer is larger than 0.1 mm.

6. The multi-layer circuit board according to claim 1, characterized in that: The copper plate is provided with a third groove, and the third groove is filled with a resin material. Along the first direction, a projection of at least one of the first grooves covers a projection of the third groove.

7. The multi-layer circuit board according to claim 1, characterized in that: Along the third direction, the copper layer stacking structure includes at least a first side surface, the first side surface is serrated, a semi-cured layer is arranged on the first side surface, and the third direction is parallel to the plane where the copper plate is located.

8. A method for preparing a multilayer circuit board, used for preparing the multilayer circuit board according to any one of claims 1 to 6, characterized in that: The preparation method comprises: Provide copper plates; Forming a plurality of semi-cured material blocks on the copper plate, wherein the semi-cured material blocks are in a regular trapezoidal shape along a first direction; forming a first copper layer on the plurality of semi-cured material blocks, wherein the first copper layer is flush with the semi-cured material blocks; A second copper layer is formed on the first copper layer.

9. The preparation method according to claim 7, characterized in that: Forming a plurality of semi-cured material blocks on the copper plate comprises: A semi-cured film layer and a thin copper layer are sequentially formed on the copper plate and patterned, and a thin copper material block is provided on the semi-cured material block.

10. The preparation method according to claim 9, characterized in that: Forming a first copper layer on the plurality of semi-cured material blocks comprises: Forming a first copper film layer by electroplating, wherein the thickness of the first copper film layer is greater than or equal to the thickness of the semi-cured material block; The first copper film layer is thinned until the thin copper material block is removed.

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