A multilayer circuit board and its manufacturing method

Abstract

This invention relates to the field of circuit board technology and discloses a multilayer circuit board and its manufacturing method. The circuit board includes a metal layer, a circuit board structure, a film, and a filler layer. In practical use, the multilayer circuit board of this invention, through the setting of "a filler layer filling between the circuit board structure and the film" and "having a first copper layer with a first thickness, having a second copper layer with a second thickness, and having the first thickness at least four times the second thickness," enables the invention to improve the performance of the circuit board structure while simultaneously preventing uneven pressure or voids caused by thickness differences between different copper layers during the lamination of the circuit board structure with the metal layer, thereby improving the yield rate of the invention during manufacturing.

Description

Technical Field

[0001] This invention relates to the field of circuit board technology, and more specifically to a multilayer circuit board and its manufacturing method. Background Technology

[0002] With the continuous development of electronic technology and the continuous progress of electronic products, the demand for circuit board structures is also increasing. Correspondingly, circuit board structures are becoming more and more complex. For example, in order to increase the circuits on the circuit board, the circuit board structure has changed from a single-layer board structure to a multi-layer board structure. Or, in order to improve the performance of the circuit board structure, the industry has begun to adopt circuit board designs with metal circuit layers of different thicknesses or heights.

[0003] For circuit board structures with metal circuit layers of different thicknesses or heights, uneven pressure can easily occur during the lamination process due to differences in thickness or height. Thinner parts are prone to over-compression, while thicker parts are under-compressed, resulting in loose lamination or structural deformation of the circuit board structure. This can also easily lead to gaps between circuit board structures, ultimately reducing product yield and causing cost losses. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention provides a multilayer circuit board and a manufacturing method. The technical problem to be solved is that the existing circuit board structure with metal circuit layers of different thicknesses or heights is prone to problems such as loose bonding or deformation during the manufacturing process due to differences in height or thickness.

[0005] To solve the above technical problems, in a first aspect, the present invention provides the following technical solution: a multilayer circuit board, comprising:

[0006] A metal layer;

[0007] A circuit board structure includes a substrate and a first copper layer with a first thickness and a second copper layer with a second thickness formed on the same side of the substrate; the first copper layer and the second copper layer are disposed at intervals on the substrate, and the first thickness is at least four times the second thickness;

[0008] A film for connecting the metal layer and the first copper layer of the circuit board structure;

[0009] A filler layer is provided between the circuit board structure and the film.

[0010] In one embodiment of the first aspect, the first copper layer has a first top surface and a first bottom surface, the first bottom surface being attached to the substrate and the first top surface being attached to the film;

[0011] The second copper layer has a second top surface and a second bottom surface, the second bottom surface being attached to the substrate, and the second top surface being covered by the filler layer.

[0012] In one embodiment of the first aspect, the circuit board structure further includes a third copper layer, which is formed on the same side of the substrate as the first copper layer and the second copper layer, and is spaced apart from each other.

[0013] The third copper layer has a third thickness, which is between the first thickness and the second thickness.

[0014] In one embodiment of the first aspect, the third thickness is at least twice the second thickness, and the first thickness is at least twice the third thickness.

[0015] In one embodiment of the first aspect, the third copper layer has a third top surface and a third bottom surface, the third bottom surface being attached to the substrate, and the third top surface being covered by the filler layer.

[0016] In one embodiment of the first aspect, the metal layer is a patterned circuit layer.

[0017] In one embodiment of the first aspect, the filling thickness of the filling layer is the same as the first thickness.

[0018] In one embodiment of the first aspect, another first copper layer and another second copper layer are further provided on the other side of the substrate, the other first copper layer is connected to another metal layer through another film, and another filler layer is provided between the other film and the other side of the substrate.

[0019] In one embodiment of the first aspect, another third copper layer is provided on the other side of the substrate, and the other third copper layer, the other first copper layer and the other second copper layer are spaced apart from each other.

[0020] Secondly, the present invention also provides a method for manufacturing a multilayer circuit board, comprising the following steps:

[0021] S1: Provide a circuit board structure and a dry film, wherein the circuit board structure includes a substrate and a copper sheet disposed on one side of the substrate;

[0022] S2: On the side of the copper sheet facing away from the substrate, a dry film is attached to the area designated as the first copper layer;

[0023] S3: Perform a thin copper process on the copper sheet to make the surface of the copper sheet facing away from the substrate stepped;

[0024] S4: Remove the dry film that was attached to the copper sheet in step S2;

[0025] S5: On the side of the copper sheet facing away from the substrate, a dry film is attached to a region that is pre-defined as a first copper layer and a second copper layer; wherein the regions on the copper sheet pre-defined as the first copper layer and the second copper layer are spaced apart.

[0026] S6: Perform a second thin copper process on the copper sheet to remove the area on the copper sheet where no dry film is applied, thereby exposing the surface of the substrate to form the first copper layer and the second copper layer, and the thickness of the first copper layer is at least four times the thickness of the second copper layer.

[0027] S7: Remove the dry film that was adhered to the copper sheet in step S5;

[0028] S8: A filler material is applied to the side of the substrate on which the copper sheet is disposed to form a filler layer. The filler layer encapsulates the second copper layer and has the same thickness as the first copper layer.

[0029] S9: The metal layer is laminated onto the filler layer and the first copper layer using a film;

[0030] S10: The metal layer is processed to form a patterned circuit layer.

[0031] The beneficial effects of this invention compared with the prior art are as follows: The multilayer circuit board of this invention, through the setting of "a filler layer filling between the circuit board structure and the film" and "having a first copper layer with a first thickness, having a second copper layer with a second thickness, and having the first thickness at least four times the second thickness", enables this invention to improve the performance of the circuit board structure, while also making it less likely to cause uneven pressure or voids due to the thickness difference between different copper layers when the circuit board structure is pressed with the metal layer, thereby improving the yield of this invention in the manufacturing process. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the circuit board structure of the present invention in Embodiment 1;

[0033] Figure 2 This is a schematic diagram of the circuit board structure of the present invention in Embodiment 2;

[0034] Figure 3 This is a schematic diagram of the circuit board structure of the present invention in Embodiment 3;

[0035] Figure 4 This is a schematic diagram of the dry film lamination structure in step S2 of Example 4;

[0036] Figure 5 This is a schematic diagram of the dry film lamination structure in step S5 of Example 4;

[0037] Figure 6This is a schematic diagram of the dry film lamination structure during the fabrication of the third copper layer in Example 4;

[0038] Figure 7 This is a schematic diagram of the structure after the first to third copper layers have been fabricated in Example 4;

[0039] Figure 8 To remove Figure 7 A schematic diagram of the dry film structure in the diagram;

[0040] Figure 9 In order to be in Figure 8 A structural diagram showing the completed filling layer.

[0041] Figure 10 In order to be in Figure 9 A schematic diagram of the structure for fabricating film and metal layers on the structure.

[0042] 100a: Multilayer circuit board

[0043] 1: Metal layer;

[0044] 2: Circuit board structure; 21: Substrate; 211: Top surface; 212: Bottom surface

[0045] 22: First copper layer; 221: First top surface; 222: First bottom surface;

[0046] 23: Second copper layer; 231: Second top surface; 232: Second bottom surface;

[0047] 3: Film;

[0048] 4: Fill layer; 41: Top fill layer; 42: Bottom fill layer;

[0049] T1: First thickness; T2: Second thickness; T3: Third thickness; T4: Filling thickness. Detailed Implementation

[0050] The following specific embodiments illustrate the implementation of the "multilayer circuit board" disclosed in this invention. Those skilled in the art can understand the advantages and effects of this invention from the content disclosed in this specification. This invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this invention. Furthermore, the accompanying drawings are for simple illustration only and are not depictions of actual dimensions, as stated in advance. The following embodiments will further describe the relevant technical content of this invention in detail, but the disclosed content is not intended to limit the scope of protection of this invention.

[0051] It should be understood that while terms such as "first," "second," and "third" may be used in this document to describe various components or signals, these components or signals should not be limited by these terms. These terms are primarily used to distinguish one component from another, or one signal from another. Furthermore, the term "or" as used herein should, as appropriate, include any combination of one or more of the related listed items.

[0052] Example 1

[0053] like Figure 1 As shown, a multilayer circuit board 100a includes:

[0054] A metal layer 1;

[0055] A circuit board structure 2 includes a substrate 21 and a first copper layer 22 with a first thickness T1 and a second copper layer 23 with a second thickness T2 formed on the same side of the substrate 21. The first copper layer 22 and the second copper layer 23 are disposed at intervals on the substrate 21, and the first thickness T1 is at least four times the second thickness T2; that is, the first copper layer 22 and the second copper layer 23 have different thicknesses, and the first thickness T1 of the first copper layer 22 is greater than the second thickness T2 of the second copper layer 23. In this embodiment, the first thickness T1 is described as four times the second thickness T2, but this invention is not limited thereto.

[0056] A film 3 is used to connect the metal layer 1 and the first copper layer 22 of the circuit board structure 2;

[0057] A filler layer 4 is filled between the circuit board structure 2 and the film 3 so that the film 3 and the metal layer 1 can be pressed flat and tightly onto the circuit board structure 2, and so that gaps are not easily generated between the circuit board structure 2 and the film 3.

[0058] Specifically, in this embodiment, the metal layer 1 is disposed on one side of the film 3, and the metal layer 1 and the circuit board structure 2 are spaced apart; that is, the metal layer 1 and the circuit board structure 2 are pressed together by the film 3.

[0059] Specifically, in this embodiment, the metal layer 1 is a patterned circuit layer. More specifically, the metal layer 1 can be further processed (e.g., thin copper processing or etching) to form a patterned circuit layer, thus meeting the different requirements of backend manufacturers for the multilayer circuit board 100a.

[0060] Specifically, in this embodiment, the substrate 21 has an upper plate surface 211 and a lower plate surface 212 located on opposite sides. The first copper layer 22 and the second copper layer 23 are jointly disposed on the upper plate surface 211 of the substrate 21, and the first copper layer 22 and the second copper layer 23 are not adjacent; that is, neither side of the first copper layer 22 is connected to either side of the second copper layer 23. It should be noted that in other embodiments not shown in this work, the first copper layer 22 and the second copper layer 23 may also be jointly disposed on the lower plate surface 212 of the substrate 21.

[0061] In addition, in this embodiment, a plurality of metal circuit layers 213 may be further provided inside the substrate 21, and the number of the plurality of metal circuit layers 213 can be increased or decreased as needed.

[0062] Specifically, in this embodiment, the portion of the upper surface 211 of the circuit board structure 2 that does not have the first copper layer 22 is coated with a filler material, and the filler material covers the portion of the second copper layer 23 that is not connected to the substrate 21, and all the filler material forms the final filler layer 4.

[0063] In detail, the material of the filler layer 4 is resin ink. The filler layer 4 has a filler thickness T4, which is equal to the first thickness T1. Specifically, the filler layer 4 has a filler top surface 41 and a filler bottom surface 42, and the distance from the filler top surface 41 to the filler bottom surface 42 (that is, the distance from the filler top surface 41 to the upper surface 211 of the substrate 21) is the filler thickness T4.

[0064] The film 3 is disposed between the metal layer 1 and the circuit board structure 2; that is, the film 3 is used to connect the metal layer 1 and the circuit board structure 2. In this embodiment, the film 3 is preferably made of an insulating prepreg material (PP) composed of glass fiber material and epoxy resin, but is not limited thereto.

[0065] Specifically, in this embodiment, the first copper layer 22 has a first top surface 221 and a first bottom surface 222, and the second copper layer 23 has a second top surface 231 and a second bottom surface 232. The first bottom surface 222, the second bottom surface 232 and the filling bottom surface 42 are attached to the substrate 21, the first top surface 221 and the filling top surface 41 are attached to the film 3 (that is, the first top surface 221 is preferably coplanar with the filling top surface 41), and the second top surface 231 is covered by the filling layer 4 (that is, the second copper layer 23 is embedded in the filling layer 4).

[0066] Accordingly, the film 3 is connected to the circuit board structure 2 through the first copper layer 22; and the filler layer 4 fills the gap caused by the different thickness difference between the first copper layer 22 and the second copper layer 23. At the same time, the film 3 and the filler layer 4 can prevent the metal layer 1 from directly contacting the first copper layer 22 and the second copper layer 23.

[0067] In conjunction with the above, the multilayer circuit board 100a in this embodiment, through the configuration of "a filling layer 4 filling between the circuit board structure 2 and the film 3" and "making the first copper layer 22 have a first thickness T1, making the second copper layer 23 have a second thickness T2, and making the first thickness T1 at least four times the second thickness T2", enables the present invention to improve the performance of the circuit board structure, while also making the circuit board structure 2 less prone to uneven pressure or gaps due to the thickness difference between different copper layers when pressed with the metal layer 1, thereby improving the yield of the present invention in the manufacturing process.

[0068] Example 2

[0069] like Figure 2 As shown, this embodiment provides a circuit board 100b with another structure. Since this embodiment is similar to the first embodiment described above, the similarities between the two embodiments will not be repeated. The differences between this embodiment and the first embodiment described above are roughly as follows:

[0070] In this embodiment, the circuit board structure 2 further includes a third copper layer 24, which is formed on the same side of the substrate 21 as the first copper layer 22 and the second copper layer 23, and is spaced apart from each other.

[0071] The third copper layer 24 has a third thickness T3, and the third thickness T2 is between the first thickness T1 and the second thickness T2.

[0072] More specifically, in this embodiment, the third thickness T3 is at least twice the second thickness T2, and the first thickness T1 is at least twice the third thickness T3.

[0073] Additionally, the third copper layer 24 has a third top surface 241 and a third bottom surface 242. The third top surface 241 is covered by the filler layer 4 (that is, the third copper layer 24 is embedded in the filler layer 4), and the third bottom surface 242 is attached to the substrate 21. In this embodiment, the third thickness T3 is described as twice the second thickness T2, and the first thickness T1 is twice the third thickness T3, but this invention is not limited thereto.

[0074] Example 3

[0075] like Figure 3 As shown, this embodiment provides a multilayer circuit board 100c with another structure, in Figure 3In this embodiment, the upper surface 211 of the substrate 21 has the same structural configuration as in Embodiment 2, and is provided with a copper layer 22, a second copper layer 23, a third copper layer 24 and a filler layer 4; the thickness relationship and positional relationship of the first copper layer 22, the second copper layer 23, the third copper layer 24 and the filler layer 4 are the same as in Embodiment 2, and will not be described here. Similarly, the positional relationship of the first copper layer 22, the second copper layer 23, the third copper layer 24, the filler layer 4, the film 3 and the metal layer 1 are the same as in Embodiment 2, and will not be described here.

[0076] Unlike Embodiment 2, another first copper layer 22, another second copper layer 23 and another third copper layer 24 are also provided on the other side of the substrate 21, namely the lower plate surface 212 of the substrate 21. The other first copper layer 22 is connected to the other metal layer 1 through another film 3. Another filler layer 4 is also provided between the other film 3 and the other layer of the substrate 21.

[0077] Similarly, in this embodiment, another first copper layer 22 also has a first thickness T1, another second copper layer 23 also has a second thickness T2, another third copper layer 24 also has a third thickness T3, and another filler layer 4 also has a filler thickness T4.

[0078] In one embodiment, one side of the substrate 21 may be provided with a first copper layer 22 and a second copper layer 23 as in the embodiment, while the other side of the substrate 21 may be provided with another first copper layer 22 and another second copper layer 23.

[0079] Example 4

[0080] This embodiment also provides a method for manufacturing a multilayer circuit board, wherein the multilayer circuit board includes at least one metal layer 1 and a circuit board structure 2, and the method for manufacturing the multilayer circuit board enables the circuit board structure 2 to have diverse copper layer thicknesses; simultaneously, a filler layer 4 and a film 3 enable the circuit board structure 2 to be tightly bonded to the metal layer 1, including the following steps:

[0081] S1: Provides circuit board structure 2 and dry film 200, such as Figure 4 As shown, the circuit board structure 2 includes a substrate 21 and a copper sheet 25 disposed on one side of the substrate 21; it should also be noted that, for further explanation, Figure 4 Copper sheets 25 are respectively provided on both sides of the substrate 21. When it is necessary to provide metal layers 1 on both sides of the substrate 21, refer to the specific map. Figures 4-10 Correspondingly, in a certain embodiment, in step S1, copper sheets 35 can be provided on both sides of the substrate 21.

[0082] When only the metal layer 1 needs to be provided on the upper side of the substrate 21, Figures 4-10 The structure on the lower plate surface 222 of the substrate 21 can be removed;

[0083] S2: Similarly, as Figure 4 As shown, on the side of the copper sheet 25 facing away from the substrate 21, the dry film 200 is attached to the area that is preset as the first copper layer 22;

[0084] S3: Perform a thin copper coating or etching operation on the copper sheet 25, so that the surface of the copper sheet 25 facing away from the substrate 21 is stepped. At this time, the structure of the circuit board structure 2 and the structure of the copper sheet 25 are as follows. Figure 5 As shown;

[0085] S4: Remove the dry film 200 that was attached to the copper sheet 25 in step S2;

[0086] S5: As Figure 5 As shown, on the side of the copper sheet 25 facing away from the substrate 21, a dry film 200 is attached to the area that is preset as the first copper layer 22 and the second copper layer 23; wherein the areas of the first copper layer 22 and the second copper layer 23 on the copper sheet 25 are arranged at intervals.

[0087] S6: Perform a second thin copper process on the copper sheet 25 to remove the area on the copper sheet 25 where the dry film 200 is not provided, so that the surface of part of the substrate 21 is exposed, thereby forming a first copper layer 22 and a second copper layer 23, and the thickness of the first copper layer 22 is at least four times the thickness of the second copper layer 23.

[0088] In one embodiment, when a third copper layer 24 needs to be fabricated on the substrate 21, during the secondary thin copper operation in step S6, the thin copper termination surface does not contact the upper plate surface 211 of the substrate 21. Then, the dry film 200 on the copper sheet 25 is removed. Next, on the side of the copper sheet 25 facing away from the substrate 21, the dry film 200 is attached to the area designated as the first copper layer 22, the second copper layer 23, and the third copper layer 24. The structure at this time is as follows: Figure 6 As shown, the copper sheet 25 is then subjected to three thin copper processing steps to remove the areas on the copper sheet 25 where the dry film 200 is not applied, exposing a portion of the surface of the substrate 21, thereby forming the first copper layer 22, the second copper layer 23, and the third copper layer 24. The structure at this point is as follows: Figure 7 As shown, the thickness and positional relationships of the first copper layer 22, the second copper layer 23, and the third copper layer 24 are as described above;

[0089] S7: Remove the dry film 200 adhered to the copper sheet 25 in step S5; when the third copper layer 24 needs to be fabricated in step S6, remove the dry film from step S6. The corresponding structure at this time is as follows. Figure 8 As shown;

[0090] S8: A filler material is applied to the side of the substrate 21 where the copper sheet 25 is located, forming a filler layer 4. The filler layer 4 surrounds the second copper layer 23, and its thickness is the same as that of the first copper layer 22. The structure at this time is as follows: Figure 9 As shown; in addition, the filler material can be resin ink; the thickness and positional relationship of the first copper layer 22, the second copper layer 34, the third copper layer 24 and the filler layer 4 are as described above;

[0091] S9: The metal layer 1 is pressed onto the filler layer 4 and the first copper layer 22 using the film 3. The structure at this point is as follows: Figure 10 As shown, in Figure 10 In this embodiment, the film 3 is disposed between the metal layer 1 and the circuit board structure 2; that is, the film 3 is used to connect the metal layer 1 and the circuit board structure 2. In this embodiment, the film 3 is preferably made of an insulating prepreg material (PP) composed of glass fiber material and epoxy resin;

[0092] S10: Process metal layer 1 to form a patterned circuit layer.

[0093] Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this invention. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A multilayer circuit board, characterized in that, include: A metal layer (1); A circuit board structure (2) includes a substrate (21) and a first copper layer (22) with a first thickness and a second copper layer (23) with a second thickness formed on the same side of the substrate (21); the first copper layer (22) and the second copper layer (23) are disposed at intervals on the substrate (21), and the first thickness is at least four times the second thickness; A film (3) is used to connect the metal layer (1) and the first copper layer (22) of the circuit board structure (2). A filler layer (4) is filled between the circuit board structure (2) and the film (3); The first copper layer (22) has a first top surface (221) and a first bottom surface (222), the first bottom surface (222) is attached to the substrate (21), and the first top surface (221) is attached to the film (3); The second copper layer (23) has a second top surface (231) and a second bottom surface (232), the second bottom surface (232) is attached to the substrate (21), and the second top surface (231) is covered by the filler layer (4); The circuit board structure (2) further includes a third copper layer (24), which is formed on the same side of the substrate (21) as the first copper layer (22) and the second copper layer (23) and is spaced apart from each other; The third copper layer (24) has a third thickness, which is between the first thickness and the second thickness; The filling thickness of the filling layer (4) is the same as the first thickness; The filler layer (4) is made of resin ink.

2. A multilayer circuit board according to claim 1, characterized in that, The third thickness is at least twice the second thickness, and the first thickness is at least twice the third thickness.

3. A multilayer circuit board according to claim 1, characterized in that, The third copper layer (24) has a third top surface (241) and a third bottom surface (242), the third bottom surface (242) is attached to the substrate (21), and the third top surface (241) is covered by the filler layer (4).

4. A multilayer circuit board according to claim 1, characterized in that, The metal layer (1) is a patterned circuit layer.

5. A multilayer circuit board according to claim 1, characterized in that, The film (3) is made of an insulating prepreg composed of glass fiber material and epoxy resin.

6. A multilayer circuit board according to any one of claims 1-5, characterized in that, Another first copper layer (22) and another second copper layer (23) are provided on the other side of the substrate (21). The other first copper layer (22) is connected to another metal layer (1) through another film (3). Another filler layer (4) is provided between the other film (3) and the other side of the substrate (21).

7. A multilayer circuit board according to claim 6, characterized in that, Another third copper layer (24) is provided on the other side of the substrate (21), and the other third copper layer (24), the other first copper layer (22) and the other second copper layer (23) are spaced apart from each other.

8. A method for manufacturing a multilayer circuit board, characterized in that, Includes the following steps: S1: Provide a circuit board structure (2) and a dry film (200), the circuit board structure (2) including a substrate (21) and a copper sheet (25) disposed on one side of the substrate (21). S2: On the side of the copper sheet (25) facing away from the substrate (21), a dry film (200) is attached to the area that is preset as the first copper layer (22); S3: Perform a thin copper process on the copper sheet (25) so that the surface of the copper sheet (25) away from the substrate (21) is stepped; S4: Remove the dry film (200) that was attached to the copper sheet (25) in step S2; S5: On the side of the copper sheet (25) facing away from the substrate (21), a dry film (200) is attached to the area that is preset as a first copper layer (22) and a second copper layer (23); wherein the areas of the first copper layer (22) and the second copper layer (23) on the copper sheet (25) are spaced apart; S6: Perform a second thin copper operation on the copper sheet (25) to remove the area on the copper sheet (25) where no dry film (200) is provided, so that the surface of part of the substrate (21) is exposed, thereby forming the first copper layer (22) and the second copper layer (23), and the thickness of the first copper layer (22) is at least four times the thickness of the second copper layer (23). S7: Remove the dry film (200) that was adhered to the copper sheet (25) in step S5; S8: Apply a filler material to one side of the substrate (21) where the copper sheet (25) is provided to form a filler layer (4). The filler layer (4) wraps the second copper layer (23) and has the same thickness as the first copper layer (22). S9: The metal layer (1) is pressed onto the filler layer (4) and the first copper layer (22) using a film (3); S10: The metal layer (1) is processed to form a patterned circuit layer.

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