Multilayer circuit boards and their manufacturing methods

Abstract

This invention proposes a method for manufacturing a multilayer circuit board. By setting a first groove and a second groove around a first blind via and a second blind via, respectively, conductive paste protruding from the first insulating layer and the second insulating layer are filled into the first groove and the second groove, respectively. This restricts the flow of the first and second conductive pastes, avoiding problems such as excessive overflow of conductive paste leading to short circuits due to connections with surrounding circuits, or the formation of capacitance between overflowing copper paste and the upper and lower copper layers. This is beneficial for high-density design of multilayer circuit boards and improves the quality of multilayer circuit boards. This invention also provides a multilayer circuit board prepared by the described method.

Description

Technical Field

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

[0002] Multilayer circuit boards (generally referring to 3 layers or more) mostly use conductive materials to plug vias to achieve interconnection of any layer, which can effectively reduce the manufacturing difficulty of circuit boards, shorten the manufacturing process of circuit boards, and is more environmentally friendly. Therefore, this technology has broad development prospects.

[0003] Currently, the commonly used conductive material is conductive paste. Conductive paste is an adhesive that has certain conductivity after curing or drying. It usually consists of a base resin and conductive particles as the main components. The conductive particles are bonded together by the adhesive effect of the base resin to form a conductive path. However, in actual high-temperature lamination processes, conductive paste is prone to overflow, causing short circuits between the layers and seriously affecting the quality of the circuit board. Summary of the Invention

[0004] In view of this, in order to overcome at least one of the above-mentioned defects, it is necessary to provide a method for manufacturing a circuit board.

[0005] It is also necessary to provide a circuit board manufactured using the aforementioned circuit board manufacturing method.

[0006] This invention provides a method for manufacturing a multilayer circuit board, the method comprising:

[0007] At least one first circuit board is provided, the first circuit board includes a first insulating layer and a first conductive line layer stacked thereon, the first insulating layer has a first blind hole and at least one first groove located around the first blind hole, the first blind hole has a first conductive paste block electrically connected to the first conductive line layer, and the first conductive paste block protrudes from the first insulating layer.

[0008] At least one second circuit board is provided, the second circuit board includes a stacked second insulating layer and a second conductive line layer, the second insulating layer has a second blind via and at least one second groove located around the second blind via, the second blind via has a second conductive paste block electrically connected to the second conductive line layer, and the second conductive paste block protrudes from the second insulating layer.

[0009] At least one first circuit board and at least one second circuit board are stacked to obtain an intermediate.

[0010] And, the intermediate body is pressed together so that the first conductive paste and the second conductive paste fill the first groove and the second groove respectively, wherein the first conductive paste located in the first blind hole forms a first conductive part, the first conductive paste located in the first groove forms a first overflow part, the second conductive paste located in the second blind hole forms a second conductive part, and the second conductive paste located in the second groove forms a second overflow part, thereby obtaining the multilayer circuit board.

[0011] In this embodiment of the application, the fabrication of the first circuit board includes:

[0012] A first circuit board is provided, the first circuit board including a first insulating layer and a first conductive circuit layer stacked thereon.

[0013] A first release film is formed on the first insulating layer.

[0014] At least one first blind hole is formed through the first insulating layer, and the first blind hole also penetrates the first release film. The diameter of the first blind hole gradually decreases from the first release film to the first insulating layer.

[0015] The first conductive paste block is obtained by filling each of the first blind holes with conductive paste, wherein the first conductive paste block includes a first end face away from the first conductive line layer.

[0016] At least one first groove is formed in the first insulating layer around the first end face, and the first groove penetrates the first release film.

[0017] In addition, the first release film is removed so that the first end face protrudes from the first insulating layer, thereby obtaining the first circuit board.

[0018] In this embodiment of the application, the fabrication of the second circuit board includes:

[0019] A second circuit board is provided, the second circuit board including a second insulating layer and a second conductive circuit layer stacked thereon.

[0020] A second release film is formed on the second insulating layer.

[0021] At least one second blind hole is formed through the second insulating layer, and the second blind hole also penetrates the second release film. The diameter of the second blind hole gradually decreases from the second release film to the second insulating layer.

[0022] The second conductive paste block is obtained by filling each of the second blind holes with conductive paste, wherein the second conductive paste block includes a second end face away from the second conductive line layer.

[0023] At least one second groove is formed in the second insulating layer around the second end face, and the second groove penetrates the second release film.

[0024] In addition, the second release film is removed so that the second end face protrudes from the second insulating layer, thereby obtaining the second circuit board.

[0025] In this embodiment of the application, the first groove is an annular groove that surrounds the first conductive paste block; and / or the second groove is an annular groove that surrounds the second conductive paste block.

[0026] In this embodiment of the application, there are multiple first grooves, which are concentrically arranged, and the depth of the multiple first grooves increases or decreases sequentially in the direction away from the first blind hole; and / or, there are multiple second grooves, which are concentrically arranged, and the depth of the multiple second grooves increases or decreases sequentially in the direction away from the second blind hole.

[0027] In this embodiment of the application, the number of the first grooves is multiple, and the cross-section of each first groove is at least one of rectangle, circle and trapezoid; and / or the number of the second grooves is multiple, and the cross-section of each second groove is at least one of rectangle, circle and trapezoid.

[0028] In this embodiment of the application, after the pressing step, both the first conductive paste block and the second conductive paste block are trapezoidal in shape.

[0029] The present invention also provides a multilayer circuit board, comprising at least one first circuit board and at least one second circuit board. The first circuit board includes a first insulating layer and a first conductive circuit layer stacked thereon. The first insulating layer has a first blind via and at least one first groove surrounding the first blind via. The first blind via has a first conductive portion, and the first groove has a first overflow portion. The first conductive portion is electrically connected to the first conductive circuit layer. The second circuit board includes a second insulating layer and a second conductive circuit layer stacked thereon. The second insulating layer has a second blind via and at least one second groove surrounding the second blind via. The second blind via has a second conductive portion, and the second groove has a second overflow portion. The second conductive portion is electrically connected to the second conductive circuit layer.

[0030] In this embodiment of the application, the first groove is an annular groove that surrounds the first conductive paste block; and / or the second groove is an annular groove that surrounds the second conductive paste block.

[0031] In this embodiment of the application, there are multiple first grooves, which are concentrically arranged, and the depth of the multiple first grooves increases or decreases sequentially in the direction away from the first blind hole; and / or there are multiple second grooves, which are concentrically arranged, and the depth of the multiple second grooves increases or decreases sequentially in the direction away from the second blind hole.

[0032] In this embodiment of the application, the number of the first grooves is multiple, and the cross-section of each first groove is at least one of rectangle, circle and trapezoid; and / or the number of the second grooves is multiple, and the cross-section of each second groove is at least one of rectangle, circle and trapezoid.

[0033] Compared to existing technologies, the multilayer circuit board manufacturing method provided by this invention involves setting a first groove and a second groove around the first and second blind vias, respectively. During the lamination process of the first and second circuit boards, the first conductive paste protruding from the first insulating layer and the second conductive paste protruding from the second insulating layer overflow and fill the first and second grooves, respectively. The first and second grooves restrict the flow of conductive paste, preventing excessive overflow and short circuits caused by the conductive paste connecting to surrounding circuits, or the overflowing copper paste forming capacitance with the upper and lower copper layers. Furthermore, it increases the contact area between the first conductive paste and the first insulating layer, and the second conductive paste and the second insulating layer, thereby increasing the adhesion between the first conductive paste and the first insulating layer, and the second conductive paste and the second insulating layer, respectively. This reduces the impact of heat treatment on the first and second conductive pastes, thus improving the reliability of the multilayer circuit board. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure after a first release film and a second release film are formed on a first circuit substrate and a second circuit substrate provided in an embodiment of the present invention.

[0035] Figure 2 Is Figure 1 The diagram shows the structure of the first circuit board and the second circuit board after the first blind via and the second blind via are respectively formed.

[0036] Figure 3 Is Figure 2 The diagram shows the structure after the first and second blind holes are filled with conductive paste to form a first conductive paste block and a second conductive paste block, respectively.

[0037] Figure 4 exist Figure 3The diagram shows the structure after the first and second grooves are formed on the first and second insulating layers.

[0038] Figure 5 This is a schematic diagram of the structure of the first blind hole and the first groove provided in an embodiment of the present invention.

[0039] Figure 6 This is a schematic diagram of the structure of the first groove and the second groove provided in another embodiment of the present invention.

[0040] Figure 7 and Figure 8 This is a structural schematic diagram of the first and second grooves provided in another embodiment.

[0041] Figure 9 It is Figure 4 The diagram shows the structure after the first and second stripping membranes have been removed.

[0042] Figure 10 It is Figure 9 The diagram shows the structure of a multilayer circuit board obtained by stacking and pressing the first and second circuit boards together.

[0043] Figure 11 This is a schematic diagram of the structure of a multilayer circuit board provided in another embodiment of the present invention.

[0044] Explanation of main component symbols

[0045] Multilayer circuit board 100, 200

[0046] First circuit board 10

[0047] First insulating layer 101

[0048] First conductive circuit layer 102

[0049] Second circuit board 20

[0050] Second insulating layer 201

[0051] Second conductive circuit layer 202

[0052] Connecting pad 2021

[0053] First peeling film 30

[0054] Second peeling film 40

[0055] First blind hole 50

[0056] Second blind hole 51

[0057] First conductive paste block 60

[0058] First end face 601

[0059] Second conductive paste block 61

[0060] Second end face 611

[0061] First groove 70, 72

[0062] Second grooves 71, 73

[0063] First circuit board 80

[0064] Second circuit board 81

[0065] First conductive part 90

[0066] First overflow section 91

[0067] Second conductive part 92

[0068] Second overflow section 93

[0069] First connecting part 94

[0070] Second connecting part 95

[0071] First overflow zone A

[0072] Second overflow zone B

[0073] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0074] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0076] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0077] A preferred embodiment of the present invention provides a method for manufacturing a multilayer circuit board, comprising the following steps:

[0078] Step S1, please refer to Figure 1 It provides at least one first circuit board 10 and at least one second circuit board 20.

[0079] In this embodiment, the first circuit board 10 includes a first insulating layer 101 and a first conductive line layer 102 stacked together, the first conductive line layer 102 being formed on the surface of the first insulating layer 101. The second circuit board 20 includes a second insulating layer 201 and a second conductive line layer 202 stacked together, the second conductive line layer 202 being embedded within the second insulating layer 201. The second conductive line layer 202 includes a plurality of connecting pads 2021. In this embodiment, two first circuit boards 10 and two second circuit boards 20 are provided.

[0080] The materials of both the first insulating layer 101 and the second insulating layer 201 can be selected from one of the following resins: epoxy resin, prepreg (PP), BT resin, polyphenylene ether (PPO), polyimide (PI), polyethylene terephthalate (PET), and polyethylene naphthalate (PEN). In this embodiment, both the first insulating layer 101 and the second insulating layer 201 are made of prepreg.

[0081] In this embodiment, the thickness T of both the first insulating layer 101 and the second insulating layer 201 is 5 to 150 micrometers.

[0082] Step S2: A first release film 30 and a second release film 40 are formed on the first insulating layer 101 and the second insulating layer 201, respectively.

[0083] In this embodiment, the thickness of both the first peeling film 30 and the second peeling film 40 is about 25 micrometers.

[0084] In this embodiment, both the first release film 30 and the second release film 40 are PET films.

[0085] Step S3, please refer to Figure 2 A first blind hole 50 is formed in the first circuit substrate 10, penetrating the first insulating layer 101, and the first blind hole 50 also penetrates the first release film 30. A second blind hole 51 is formed in the second circuit substrate 20, penetrating the second insulating layer 201, and the second blind hole 51 also penetrates the second release film 40.

[0086] The diameter of the first blind hole 50 gradually decreases from the first release film 30 to the first insulating layer 101, and the diameter of the second blind hole 51 gradually decreases from the second release film 40 to the second insulating layer 201.

[0087] The radius of the end of the first blind via 50 furthest from the first conductive layer 102 (i.e., the maximum radius of the first blind via 50) is approximately the same as the radius of the end of the second blind via 51 furthest from the second conductive layer 202 (i.e., the maximum radius of the second blind via 51). Figure 9 As shown, the radius of the blind hole is defined as R, and the radius R is 50 to 150 micrometers.

[0088] In this embodiment, the radius R is approximately 100 micrometers.

[0089] In this embodiment, both the first blind hole 50 and the second blind hole 51 are formed by laser drilling.

[0090] For step S4, please refer to [link / reference]. Figure 3 Conductive paste is filled into each of the first blind holes 50 and each of the second blind holes 51, and then cured to obtain a first conductive paste block 60 and a second conductive paste block 61 that are electrically connected to the first conductive circuit layer 102 and the second conductive circuit layer 202, respectively.

[0091] The first conductive paste block 60 includes a first end face 601 that is away from the first conductive circuit layer 102, and the second conductive paste block 61 includes a second end face 611 that is away from the second conductive circuit layer 202.

[0092] In this embodiment, both the first conductive paste block 60 and the second conductive paste block 61 are trapezoidal.

[0093] In this embodiment, the conductive paste can be solder paste or copper paste, etc. Specifically, the conductive paste is solder paste.

[0094] For step S5, please refer to [link / reference]. Figure 4 A first groove 70 is formed in the first insulating layer 101 around the first end face 601, and the first groove 70 penetrates the first release film 30; a second groove 71 is formed in the second insulating layer 201 around the second end face 611, and the second groove 71 penetrates the second release film 40.

[0095] The first end face 601 forms a first overflow area A around the projection area of ​​the first insulating layer 101 along the thickness direction of the first circuit substrate 10, and the first groove 70 is located in the first overflow area A; the second end face 611 forms a second overflow area B around the projection area of ​​the second insulating layer 201 along the thickness direction of the second circuit substrate 20, and the second groove 71 is located in the second overflow area B. In this embodiment, only a portion of the first insulating layer 101 and a portion of the second insulating layer 201 are removed by laser drilling in the first overflow area A and the second overflow area B, respectively, thereby forming the first groove 70 and the second groove 71. The first insulating layer 101 of the laser-drilled layer is made of a single material, the process is simple, the timeliness is good, the alignment requirement is low, and the requirements for the laser drilling equipment are low.

[0096] Please see Figures 4 to 8 In this invention, the shape, opening size, depth, arrangement, and spacing between the first groove 70 and the second groove 71 can be specifically designed according to actual needs.

[0097] Please see Figure 4 and Figure 5 In this embodiment, the first groove 70 can be an annular groove, and the first groove 70 surrounds the first conductive paste block 60. The second groove 71 can be an annular groove, and the second groove 71 surrounds the second conductive paste block 61.

[0098] Please refer to it again. Figure 4 and Figure 5 In this embodiment, there are multiple first grooves 70, which are concentrically arranged, and the depth of the multiple first grooves 70 decreases sequentially in the direction away from the first end face 601. There are also multiple second grooves 71, which are concentrically arranged, and the depth of the multiple second grooves 71 decreases sequentially in the direction away from the second end face 611.

[0099] Please see Figure 6 In another embodiment, there are multiple first grooves 70, which are concentrically arranged, and the depth of the multiple first grooves 70 increases sequentially in the direction away from the first end face 601. There are also multiple second grooves 71, which are concentrically arranged, and the depth of the multiple second grooves 71 increases sequentially in the direction away from the second end face 611. It is understood that the first grooves 70 of different depths can also be arranged irregularly, and the second grooves 71 of different depths can also be arranged irregularly. The spacing between two adjacent first grooves 70 and the spacing between two second grooves 71 can be designed according to actual needs.

[0100] Please see Figure 7 and Figure 8 In another embodiment, there are multiple first grooves 72, and the cross-section of each first groove 72 can be at least one of rectangle, circle, and trapezoid. The multiple first grooves 72 can be distributed within the first overflow area A, and the multiple first grooves 72 are arranged around the first conductive paste block 60. In this embodiment, there can also be multiple second grooves 73, and the cross-section of each second groove 73 can be at least one of rectangle, circle, and trapezoid. The multiple second grooves 73 can be distributed within the second overflow area B, and the multiple second grooves 73 are arranged around the second conductive paste block 61. In this embodiment, by designing the first grooves 72 and the second grooves 73 as small-sized grooves, and with no special requirements on the size and shape of the grooves, the precision requirements are low, and molding is convenient.

[0101] Step S6, please refer to Figure 9 The first stripping film 30 and the second stripping film 40 are removed respectively, so that the first end face 601 and the second end face 611 protrude from the first insulating layer 101 and the second insulating layer 201 respectively, to obtain the first circuit board 80 and the second circuit board 81.

[0102] Step S7: Stack at least one first circuit board 80 and at least one second circuit board 81 to obtain an intermediate body (not shown).

[0103] In this embodiment, one first circuit board 80, two second circuit boards 81, and one first circuit board 80 are stacked sequentially. Specifically, the first end face 601 of one of the first circuit boards 80 corresponds one-to-one with the second end face 611 of one of the second circuit boards 81, and the first end face 601 of the other first circuit board 80 corresponds one-to-one with the connecting pad 2021 of the other second circuit board 81.

[0104] Step S8, please refer to Figure 10 The intermediate body is pressed together so that the first conductive paste block 60 and the second conductive paste block 61 fill the first groove 70 and the second groove 71 respectively. The first conductive paste block 60 located in the first blind hole forms a first conductive part 90, the first conductive paste block 60 located in the first groove 70 forms a first overflow part 91, the second conductive paste block 61 located in the second blind hole forms a second conductive part 92, and the second conductive paste block 61 located in the second groove 71 forms a second overflow part 93, thereby obtaining the multilayer circuit board 100.

[0105] In this embodiment, after the pressing step, the portion of the first conductive paste 60 protruding from the first insulating layer 101 and the portion of the second conductive paste 61 protruding from the second insulating layer 201 are respectively squeezed and filled into the first groove 70 and the second groove 71. The first conductive part 90 located in the first blind hole is connected to the first overflow part 91 located in the first groove 70, and the second conductive part 92 located in the second blind hole is connected to the second overflow part 93 located in the second groove 71.

[0106] In this embodiment, a first conductive portion 90 in one of the first circuit boards 80 is bonded to a second conductive portion 92 in one of the second circuit boards 81 to electrically connect the first conductive circuit layer 102 and the second conductive circuit layer 202. A second conductive portion 92 in another second circuit board 81 is bonded to a connecting pad 2021 of one of the second conductive circuit layers 202 to electrically connect the two second conductive circuit layers 202. A first conductive portion 90 in another first circuit board 80 is bonded to a connecting pad 2021 of the other second conductive circuit layer 202 to electrically connect the first conductive circuit layer 102 and the second conductive circuit layer 202.

[0107] Please see Figure 10 Combined with reference Figure 3 In this embodiment, the radius r of the first end face 601 is approximately equal to the radius of the first blind hole 50, approximately 100 micrometers. The thickness H of the portion of the first conductive paste block 60 protruding from the first insulating layer 101 is equal to the thickness of the PET, approximately 25 μm. The structural dimensions of the second blind hole 51 and the second conductive paste block 61 are approximately the same as those of the first blind hole 50 and the first conductive paste block 60. Therefore, the volume V of the portion of the first conductive paste block 60 protruding from the first insulating layer 101 and the volume V of the portion of the second conductive paste block 61 protruding from the second insulating layer 201 are approximately equal, where V = PET thickness * area of ​​the first end face 601 or the second end face 611 = 25 μm * 3.14 * 100 μm * 100 μm = 785000 μm. 3 When the first conductive paste block 60 and the second conductive paste block 61 are stacked together, the total volume V of the protruding copper paste... 总 :2*V=2*785000=1570000μm 3 Assuming the first groove 70 and the second groove 71 are not present, the overflow copper paste thickness is 8–10 μm. In this case, the overflow range of the copper paste is R. 溢 Then V 总 =3.14*R 溢 2Therefore, it can be deduced that the copper paste overflow range is approximately 707μm, and the maximum distance between the copper paste overflow edge and the blind via edge is approximately 607μm. Within this range, the overflowing copper paste can easily connect with surrounding circuits, causing a short circuit, or the overflowing copper paste can form a capacitance with the upper and lower copper layers.

[0108] The present invention creates a first groove 70 and a second groove 71 around the first blind hole 50 and the second blind hole 51, respectively. During the pressing process of the first circuit board 80 and the second circuit board 81, the first conductive paste block 60 protruding from the first insulating layer 101 and the second conductive paste block 61 protruding from the second insulating layer 201 overflow and fill the first groove 70 and the second groove 71, respectively. This can avoid the problem of short circuit caused by excessive overflow of conductive paste connecting with the surrounding circuits or the phenomenon of overflowing copper paste forming a capacitor with the upper and lower copper layers.

[0109] Please see Figure 10 An embodiment of the present invention also provides a multilayer circuit board 100, which includes at least one first circuit board 80 and at least one second circuit board 81. The first circuit board 80 includes a first insulating layer 101 and a first conductive circuit layer 102 stacked together. The first insulating layer 101 has a first blind via 50 and at least one first groove 70 surrounding the first blind via 50. The first blind via 50 has a first conductive portion 90, and the first groove 70 has a first overflow portion 91. The first conductive portion 90 is electrically connected to the first conductive circuit layer 102. The second circuit board 81 includes a second insulating layer 201 and a second conductive circuit layer 202 stacked together. The second insulating layer 201 has a second blind via 51 and at least one second groove 71 surrounding the second blind via 51. The second blind via 51 has a second conductive portion 92, and the second groove 71 has a second overflow portion 93. The second conductive portion 92 is electrically connected to the second conductive circuit layer 202.

[0110] In this embodiment, the material of the first insulating layer 101 can be selected from one of the following resins: epoxy resin, prepreg (PP), BT resin, polyphenylene ether (PPO), polyimide (PI), polyethylene terephthalate (PET), and polyethylene naphthalate (PEN). In this embodiment, the material of the first insulating layer 101 is polypropylene.

[0111] In this embodiment, the material of the second insulating layer 201 can be selected from resins such as epoxy resin, prepreg (PP), BT resin, polyphenylene ether (PPO), polyimide (PI), polyethylene terephthalate (PET), and polyethylene naphthalate (PEN). In this embodiment, the material of the first insulating layer 101 is polypropylene.

[0112] In this embodiment, the thickness T of both the first insulating layer 101 and the second insulating layer 201 is 5 to 150 micrometers.

[0113] In this embodiment, the diameter of the first blind hole 50 gradually decreases from the first release film 30 to the first insulating layer 101, and the diameter of the second blind hole 51 gradually decreases from the second release film 40 to the second insulating layer 201.

[0114] Please see Figures 4 to 8 In this invention, the shape, opening size, depth, arrangement, and spacing between the first groove 70 and the second groove 71 can be specifically designed according to actual needs.

[0115] Please see Figure 4 and Figure 5 In this embodiment, the first groove 70 can be an annular groove, and the first groove 70 surrounds the first blind hole 50. The second groove 71 can be an annular groove, and the second groove 71 surrounds the second blind hole 51.

[0116] Please refer to it again. Figure 4 and Figure 5 In this embodiment, there are multiple first grooves 70, which are concentrically arranged, and the depth of the multiple first grooves 70 decreases sequentially in the direction away from the first blind hole 50. There are also multiple second grooves 71, which are concentrically arranged, and the depth of the multiple second grooves 71 decreases sequentially in the direction away from the second blind hole 51.

[0117] Please see Figure 6In another embodiment, there are multiple first grooves 70, which are concentrically arranged, and the depth of the multiple first grooves 70 increases sequentially in the direction away from the first blind hole 50. There are also multiple second grooves 71, which are concentrically arranged, and the depth of the multiple second grooves 71 increases sequentially in the direction away from the second blind hole 51. It is understood that the first grooves 70 of different depths can also be arranged irregularly, and the second grooves 71 of different depths can also be arranged irregularly. The spacing between two adjacent first grooves 70 and the spacing between two second grooves 71 can be designed according to actual needs.

[0118] Please see Figure 7 and Figure 8 In another embodiment, there are multiple first grooves 72, and the cross-section of each first groove 72 can be at least one of rectangular, circular, and trapezoidal shapes. Multiple first grooves 72 can be distributed around the first blind hole 50, and are arranged around the first blind hole 50. In this embodiment, there can also be multiple second grooves 73, and the cross-section of each second groove 73 can be at least one of rectangular, circular, and trapezoidal shapes. Multiple second grooves 73 can be distributed within the second blind hole 51, and are arranged around the second blind hole 51. In this embodiment, by designing the first grooves 72 and the second grooves 73 as small-sized grooves, and with no special requirements on the size and shape of the grooves, low precision requirements, and easy molding, the advantages are achieved.

[0119] In this embodiment, the second conductive line layer 202 includes a plurality of connection pads 2021.

[0120] In this embodiment, the first circuit board 80 has two layers, and there are two second circuit boards 81. The first conductive part 90 in one of the first circuit boards 80 is bonded to the second conductive part 92 in one of the second circuit boards 81 to electrically connect the first conductive circuit layer 102 and the second conductive circuit layer 202. The second conductive part 92 in the other second circuit board 81 is bonded to the connecting pad 2021 of one of the second conductive circuit layers 202 to electrically connect the two second conductive circuit layers 202. The first conductive part 90 in the other first circuit board 80 is bonded to the connecting pad 2021 of the other second conductive circuit layer 202 to electrically connect the first conductive circuit layer 102 and the second conductive circuit layer 202.

[0121] Please see Figure 11Another embodiment of the present invention provides a multilayer circuit board 200, wherein the first circuit board 80 of the multilayer circuit board 200 further includes a first connection portion 94, and the first conductive portion 90 and the first overflow portion 91 are connected through the first connection portion 94. The second circuit board 81 further includes a second connection portion 95, and the second conductive portion 92 and the second overflow portion 93 are connected through the second connection portion 94.

[0122] In summary, the method for preparing a multilayer circuit board provided by the present invention involves setting a first groove 70 and a second groove 71 around the first blind via 50 and the second blind via 51, respectively. During the pressing process of the first circuit board 80 and the second circuit board 81, the first conductive paste block 60 protruding from the first insulating layer 101 and the second conductive paste block 61 protruding from the second insulating layer 201 overflow and fill into the first groove 70 and the second groove 71, respectively. The first groove 70 and the second groove 71 can restrict the flow of conductive paste, which can avoid the problem of short circuit caused by excessive overflow of conductive paste connecting with surrounding circuits or the phenomenon of overflowing copper paste forming capacitance with the upper and lower copper layers. Furthermore, it can increase the contact area between the first conductive paste 60 and the first insulating layer 101, and the contact area between the second conductive paste 61 and the second insulating layer 201, thereby increasing the adhesion between the first conductive paste 60 and the first insulating layer 101, and the adhesion between the second conductive paste 61 and the second insulating layer 201, respectively, reducing the impact of hot and cold treatment on the first conductive paste 60 and the second conductive paste 61, thereby improving the reliability of the multilayer circuit board 100.

Claims

1. A method for manufacturing a multilayer circuit board, characterized in that, include: At least one first circuit board is provided. The first circuit board includes a first insulating layer and a first conductive line layer stacked together. The first insulating layer has a first blind via and at least one first groove located around the first blind via. The first blind via has a first conductive paste block electrically connected to the first conductive line layer. The first conductive paste block protrudes from the first insulating layer. The first groove is an annular groove that surrounds the first conductive paste block. There are multiple first grooves. The multiple first grooves are concentrically arranged. The depth of the multiple first grooves increases or decreases sequentially in the direction away from the first blind via. At least one second circuit board is provided. The second circuit board includes a stacked second insulating layer and a second conductive line layer. The second insulating layer has a second blind via and at least one second groove around the second blind via. The second blind via has a second conductive paste block electrically connected to the second conductive line layer. The second conductive paste block protrudes from the second insulating layer. The second groove is an annular groove that surrounds the second conductive paste block. There are multiple second grooves. The multiple second grooves are concentrically arranged. The depth of the multiple second grooves increases or decreases sequentially in the direction away from the second blind via. By stacking at least one first circuit board and at least one second circuit board, an intermediate is obtained; and The intermediate body is pressed together so that the first conductive paste and the second conductive paste fill the first groove and the second groove respectively. The first conductive paste located in the first blind hole forms a first conductive part, the first conductive paste located in the first groove forms a first overflow part, the second conductive paste located in the second blind hole forms a second conductive part, and the second conductive paste located in the second groove forms a second overflow part, thereby obtaining the multilayer circuit board.

2. The method for manufacturing a multilayer circuit board as described in claim 1, characterized in that, The fabrication of the first circuit board includes: A first circuit board is provided, the first circuit board including a first insulating layer and a first conductive circuit layer stacked thereon; A first release film is formed on the first insulating layer; At least one first blind hole is formed through the first insulating layer, and the first blind hole also penetrates the first release film. The diameter of the first blind hole gradually decreases from the first release film to the first insulating layer. The first conductive paste block is obtained by filling each of the first blind holes with conductive paste, wherein the first conductive paste block includes a first end face away from the first conductive line layer; At least one first groove is formed in the first insulating layer around the first end face, the first groove penetrating the first release film; and Remove the first release film so that the first end face protrudes beyond the first insulating layer, thereby obtaining the first circuit board.

3. The method for manufacturing a multilayer circuit board as described in claim 1, characterized in that, The fabrication of the second circuit board includes: A second circuit board is provided, the second circuit board including a stacked second insulating layer and a second conductive circuit layer; A second release film is formed on the second insulating layer; At least one second blind hole is formed through the second insulating layer, and the second blind hole also penetrates the second release film. The diameter of the second blind hole gradually decreases from the second release film to the second insulating layer. The second conductive paste block is obtained by filling each of the second blind holes with conductive paste, wherein the second conductive paste block includes a second end face away from the second conductive line layer; At least one second groove is formed in the second insulating layer around the second end face, the second groove penetrating the second release film; and Remove the second release film so that the second end face protrudes from the second insulating layer, thereby obtaining the second circuit board.

4. The method for manufacturing a multilayer circuit board as described in claim 1, characterized in that, The number of the first grooves is multiple, and the cross-section of each first groove is at least one of rectangular, circular, and trapezoidal shapes; and / or The number of the second grooves is multiple, and the cross-section of each second groove is at least one of rectangular, circular and trapezoidal.

5. The method for manufacturing a multilayer circuit board as described in claim 1, characterized in that, After the pressing step, both the first conductive paste block and the second conductive paste block are trapezoidal in shape.

6. A multilayer circuit board, characterized in that, include: At least one first circuit board, the first circuit board including a first insulating layer and a first conductive line layer stacked together, the first insulating layer having a first blind hole and at least one first groove around the first blind hole, the first blind hole having a first conductive portion, the first groove having a first overflow portion, the first conductive portion being electrically connected to the first conductive line layer, the first groove being an annular groove surrounding the first conductive portion, the number of the first grooves being multiple, the multiple first grooves being concentrically arranged, the depth of the multiple first grooves increasing or decreasing sequentially in the direction away from the first blind hole, the first conductive portion being formed by a first conductive paste block located in the first blind hole, the portion of the first conductive paste block filled in the first groove after being pressed together forming the first overflow portion; At least one second circuit board, the second circuit board including a stacked second insulating layer and a second conductive line layer, the second insulating layer having a second blind via and at least one second groove around the second blind via, the second blind via having a second conductive portion inside the second blind via, the second groove having a second overflow portion inside the second groove, the second conductive portion being electrically connected to the second conductive line layer, the second groove being an annular groove surrounding the second conductive portion, the number of the second grooves being multiple, the multiple second grooves being concentrically arranged, the depth of the multiple second grooves increasing or decreasing sequentially in the direction away from the second blind via, the second conductive portion being formed by a second conductive paste block located inside the second blind via, the portion of the second conductive paste block filled in the second groove after being pressed together forming the second overflow portion.

7. The multilayer circuit board as described in claim 6, characterized in that, The number of the first grooves is multiple, and the cross-section of each first groove is at least one of rectangular, circular, and trapezoidal shapes; and / or The number of the second grooves is multiple, and the cross-section of each second groove is at least one of rectangular, circular and trapezoidal.

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