Circuit board and its manufacturing method

Abstract

The present application provides a circuit board and a manufacturing method thereof. The circuit board includes: a plurality of core boards stacked on top of each other, wherein the surface of at least some of the core boards includes circuit layers; wherein, there are grooves penetrating through some of the core boards on the circuit board, and a conductive substance is formed in the grooves for connecting the circuit layers in at least two core boards; the dimension of the groove in the first direction on the cross-section of the groove is greater than the dimension in the second direction, so that the electroplating liquid can contact any part in the groove for electroplating to form a conductive substance. The present application improves the problem of insufficient space for chemical solution exchange during electroplating of holes by changing the shape of the grooves, thereby enhancing the electroplating ability of the holes and expanding the depth-to-width ratio of the holes.

Description

Technical Field

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

[0002] As a crucial electronic connector, PCBs (Printed Circuit Boards) are used in nearly all electronic products and are considered the "mother of electronic system products." Electronic products are currently showing two distinct trends: thinness, lightness, and compactness, and high speed and frequency. These trends are driving downstream PCB production toward high density, high integration, packaging, miniaturization, and multi-layering, leading to increasing demand for high-density multilayer boards and HDI (High Density Interconnect). High-density multilayer boards offer short wiring lengths, low circuit impedance, high-frequency operation, stable performance, and the ability to handle more complex functions. They represent an inevitable trend in the development of electronic technology toward high speed, high frequency, multi-function, and high capacity. In particular, the in-depth application of large-scale integrated circuits will further drive PCBs toward higher precision and higher layers.

[0003] HDI wiring density offers significant advantages over conventional multilayer boards, and its application in telecommunications backbone networks is increasing. The increasing density of communications network switches and routing products means less and less wiring space, requiring more signals to be transmitted within a limited space. Conventional multilayer boards are no longer able to meet this demand. High-density interconnect (HDI) boards are manufactured using a build-up method, with conventional multilayer boards serving as the core and layers layered on top. Through drilling and in-hole metallization processes, HDI interconnects the internal wiring layers of each layer. Compared to conventional multilayer boards with only through-holes, HDI utilizes precisely placed blind and buried vias to reduce the number of through-holes, conserving available PCB routing area and significantly increasing component density.

[0004] Currently, HDI technology can achieve cross-layer connections, such as L1-3 and L1-4 connections. The typical HDI plating capability in the industry is approximately 1:1, with some reaching 1.2:1. However, due to limitations in the exchange of plating solutions for blind vias, when the ratio exceeds 1.2:1, the electroplating metallization of the blind vias becomes a bottleneck, restricting HDI technology from achieving more interconnected layers within a relatively simple process flow. Summary of the Invention

[0005] The present invention mainly provides a circuit board to improve the wiring density of printed circuit board products.

[0006] A technical solution adopted by the present invention is to provide a circuit board, comprising:

[0007] A plurality of core boards are stacked, wherein at least a portion of the surfaces of the core boards include a circuit layer;

[0008] Among them, there are grooves penetrating through part of the core board on the circuit board, and conductive substances are formed in the grooves for connecting the circuit layers in at least two of the core boards;

[0009] The size of the groove in the first direction on the cross-section is larger than the size in the second direction, so that the electroplating liquid can contact any part of the groove for electroplating to form the conductive substance.

[0010] One technical solution adopted by the present invention is to provide a circuit board, including:

[0011] A plurality of core boards stacked, among which, the surfaces of at least some of the core boards include circuit layers;

[0012] Among them, a concave hole is formed on one surface of the circuit board, and a conductive substance is formed in the hole for connecting the circuit layers in at least two of the core boards;

[0013] The diameter of the hole near the opening position in the axial direction is larger than the diameter far from the opening position, so that there is enough space in the hole for electroplating to form the conductive substance.

[0014] One technical solution adopted by the present invention is to provide a circuit board, including:

[0015] A plurality of core boards stacked, and at least some of the surfaces of the core boards include circuit layers;

[0016] Among them, holes are formed in the circuit board in the thickness direction, and conductive substances are formed in the holes for connecting the circuit layers in at least two of the core boards;

[0017] The cross-section of the hole has different sizes in two different directions or different spatial sizes in the axial direction, so that the electroplating liquid enters from the position with a larger size to the position with a smaller size, and from the position with a larger axial space to the position with a smaller axial space to form the conductive substance.

[0018] One technical solution adopted by the present invention is to provide a circuit board, including:

[0019] A plurality of core boards stacked, among which, the surfaces of at least some of the core boards include circuit layers;

[0020] Among them, there are holes penetrating through part of the core board on the circuit board, and conductive substances are formed in the holes for connecting the circuit layers in at least two of the core boards;

[0021] Among them, the size of the cross-section of the hole in the first direction is larger than the size in the second direction, and the ratio of the depth of the hole to the size in the first direction is less than 1.2; or

[0022] The dimension of the hole in the first direction of the cross-section is equal to the dimension in the second direction, and the ratio of the depth of the hole to the dimension in the first direction or the dimension in the second direction is less than 2.

[0023] One technical solution adopted by the present invention is to provide a method for manufacturing a circuit board, including:

[0024] Providing a plurality of core boards stacked, and the surface of the core board includes a circuit layer;

[0025] Providing a slot penetrating through part of the core boards on the circuit board;

[0026] Forming a conductive substance in the slot to connect the circuit layers in at least two of the core boards;

[0027] Wherein, the dimension of the slot in the first direction of the cross-section is greater than the dimension in the second direction.

[0028] The circuit board provided by the present invention includes: a plurality of core boards stacked, wherein the surface of at least part of the core boards includes a circuit layer; there is a slot penetrating through part of the core boards on the circuit board, and a conductive substance is formed in the slot for connecting the circuit layers in at least two of the core boards; wherein, the dimension of the slot in the first direction of the cross-section is greater than the dimension in the second direction. Compared with the traditional circular via hole, the depth-to-width ratio of the slot is reduced, which can enable the electroplating solution to contact any part in the slot, improving the electroplating ability. Description of the Drawings

[0029] Figure 1a is a schematic structural diagram of the first embodiment of the circuit board of the present invention;

[0030] Figure 1b is a schematic structural diagram of the cross-section of the slot of the circuit board of the present invention;

[0031] Figure 2 is a schematic structural diagram of the second embodiment of the circuit board of the present invention;

[0032] Figure 3a is a schematic structural diagram of the second embodiment of the circuit board of the present invention;

[0033] Figure 3b is a schematic structural diagram of the third embodiment of the circuit board of the present invention;

[0034] Figure 4a is a schematic structural diagram of the fourth embodiment of the circuit board of the present invention;

[0035] Figure 4b is a schematic structural diagram of the fifth embodiment of the circuit board of the present invention;

[0036] Figures 5 - 6It is a schematic flowchart of the first embodiment of the method for manufacturing the circuit board of the present invention;

[0037] Figure 7 It is a schematic flowchart of the second embodiment of the method for manufacturing the circuit board of the present invention. Detailed implementation manners

[0038] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0039] The terms "first", "second", "third", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0040] When the aspect ratio of the blind hole (the depth of the blind hole is greater than the diameter of the blind hole opening) is relatively large, when electroplating solution is introduced into the blind hole, a vacuum environment is likely to be formed at the bottom of the blind hole, resulting in the inability of the electroplating solution to flow at the bottom of the blind hole, making it impossible to fill the conductive material at the bottom of the blind hole and incomplete metallization. For this, the present application proposes the following solutions to improve the problem of solution exchange during blind hole electroplating, enhance the blind hole electroplating ability, and enable the blind hole to be completely electroplated even under high aspect ratio conditions.

[0041] The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

[0042] Please refer to Figure 1a , which is a schematic structural diagram of the first embodiment of the circuit board of the present invention, including: a plurality of core boards 11, 12 stacked, and the surfaces of at least some of the core boards 11, 12 include circuit layers 111, 121; wherein, there is a groove 13 penetrating through at least some of the core boards 11, 12 on the circuit board, and a conductive material is formed in the groove 13 for connecting the circuit layers 111, 121 in at least two of the core boards 11, 12.

[0043] Among them, the core boards 11 and 12 are both copper-clad laminates. Copper-clad laminates are the basic materials for manufacturing circuit boards, including a base substrate and a copper foil covering the substrate. The base substrate is made by impregnating materials such as paper substrates, fiberglass cloth substrates, synthetic fiber cloth substrates, non-woven fabric substrates, and composite substrates with resin to form bonding sheets, which are made by combining multiple bonding sheets. A copper foil is covered on one or both sides of the fabricated base substrate, and then hot-pressed and cured to make the copper-clad laminate. The circuit layers 111 and 121 are provided on the copper foils on the surfaces of the core boards 11 and 12.

[0044] In the prior art, the holes connecting the circuit layers are generally circular. In this embodiment, the traditional circular holes are stretched in one direction to change the shape of the holes, making them into the shape of the groove 13 as shown in Figure 1b Figure. Specifically, the dimension of the groove 13 in the first direction on the cross-section is larger than the dimension in the second direction. In one embodiment, the cross-sectional shape of the groove 13 can also be oval, etc., as long as the electroplating solution can contact any part of the groove 13 when entering the groove 13 for electroplating. Specifically, in one embodiment, the ratio of the depth of the groove 13 to the dimension of the groove 13 in the first direction on the cross-section is less than 1.2.

[0045] In this embodiment, when changing the shape of the groove 13, the cross-sectional area of the groove 13 is increased as much as possible. Then, under the condition of the same depth, the aspect ratio (the ratio of the depth of the groove to the major axis of the groove) is reduced to improve the electroplating ability, so that any position of the groove 13 can contact the electroplating solution during electroplating to form a conductive substance. In one embodiment, the conductive substance is copper.

[0046] In this embodiment, the opening position of the groove 13 is located on the circuit layer 111 on the surface of the circuit board, the bottom of the groove 13 overlaps with the circuit layer 121 in the middle layer of the circuit board, the groove 13 is filled with a conductive substance, and the groove 13 connects the circuit layer 111 on the surface of the circuit board with the circuit layer 121 in the middle layer of the circuit board.

[0047] In this embodiment, the opening position of the groove 13 is located on the circuit layer 111 on the surface of the circuit board, the bottom is located in the middle of the circuit board and overlaps with the circuit layer 121 of the core board 12 in the middle of the circuit board, so as to electrically connect the circuit layer 111 and the circuit layer 121 through the conductive substance in the groove 13. In this embodiment, there is one groove formed by the groove 13 for connecting the circuit layers, so the circuits on the circuit layer 111 and the circuit layer 121 are each electrically conductive.

[0048] In one embodiment, the groove 13 is located in the middle of the circuit board. Specifically, as shown in Figure 2As shown in the figure, it is a schematic structural diagram of the second embodiment of the circuit board of the present invention. The opening position of the groove 13 overlaps with the circuit layer 112, the bottom of the groove 13 overlaps with the circuit layer 122, and the groove 13 is filled with a conductive substance to electrically connect the circuit layer 112 of the core board 11 and the circuit layer 122 of the core board 12.

[0049] It should be noted that when electroplating and filling the conductive substance in the groove 13, the conductive substance should be flush with the opening position of the groove 13.

[0050] Same as the first embodiment, the bottom of the groove 13 is located on one of the circuit layers of the core board 12. Specifically, the bottom of the groove 13 overlaps with the circuit layer 122, and the circuits on the circuit layer 122 are connected to each other, that is, the circuits on the circuit layer 122 are electrically connected. In one embodiment, the circuits on the circuit layer 122 can also be not connected to each other, such as Figure 4b as shown.

[0051] In this embodiment, by changing the shape of the groove 13 and increasing the cross-sectional area of the groove 13, the depth-to-width ratio is further reduced to improve the electroplating ability of the blind hole, expand the depth-to-width ratio of the blind hole, and further increase the wiring density of the printed circuit board product.

[0052] Please refer to Figure 3a , which is a schematic structural diagram of the third embodiment of the circuit board of the present application. The bottom of the groove 13 of the circuit board has a boss 14, and a blind hole is formed between the boss 14 and the opposite side wall of the groove 13. In order to prevent incomplete electroplating at other positions (such as the blind hole) outside the position of the boss 14 at the bottom of the groove 13 and ensure that all positions can contact the conductive substance, the thickness of the boss 14 is limited within the range of a preset threshold value, that is, the ratio of the height of the boss 14 to the diameter of the blind hole is less than the preset threshold value. The preset threshold value is the value that can make the electroplating solution enter the groove 13 and contact any position of the groove 13 including the wall of the blind hole, that is, the depth-to-width ratio threshold value that can just make the electroplating solution enter any position of the groove 13. Specifically, in one embodiment, the ratio of the height of the boss 14 to the diameter of the blind hole is less than 1.

[0053] In this embodiment, the boss 14 is located on one side of the bottom of the groove 13 and is connected to the side wall of the groove 13. The part of the bottom of the groove 13 without the boss 14 on the other side forms a blind hole with the side wall of the boss. In addition, the remaining positions of the bottom of the groove 13 except the position of the boss 14 overlap with the circuit layer 121. After electroplating in the groove 13 to fill the groove 13 with the conductive substance, the conductive substance is flush with the opening position of the groove 13, and the conductive substance contacts the circuit layer 121 on the bottom surface of the groove 13 to electrically connect the circuit layer 111 at the opening position of the groove 13 and the circuit layer 121 at the bottom of the groove 13.

[0054] In this embodiment, there is one boss 14. In other embodiments, there may be multiple bosses 14, such as Figure 3b As shown in the schematic structural diagram of the fourth embodiment of the circuit board of the present invention, the boss 14 includes 141 and 142. The bosses 141 and 142 are located on both sides of the bottom of the groove 13 and are connected to the side walls of the groove 13, and there is no connection between the bosses 141 and 142. Similar to the second embodiment, in this embodiment, the rest of the bottom of the groove 13 except for the positions of the bosses 141 and 142 overlaps with the circuit layer 121.

[0055] The above Figure 1a , Figure 2 , Figure 3a and Figure 3b In the embodiments shown, there is one hole formed by the groove 13 for connecting the circuit layer 111 and the circuit layer 121 or the circuit layer 112 and the circuit layer 122. Therefore, the circuits on the circuit layer 111, the circuit layer 121, the circuit layer 112, and the circuit layer 122 are interconnected. It should be noted that the groove 13 and the groove with the boss 14 in the above embodiments, for example, can all be located in the middle of the circuit board as shown in Figure 2 As shown.

[0056] Please refer to Figure 4a , which is the schematic structural diagram of the fifth embodiment of the circuit board of the present invention. In this embodiment, the boss 143 is located in the middle of the bottom of the groove 13 and is connected to the side wall of the groove in one direction and not connected to the side wall in the other direction. An insulating material is formed above the boss 143 to divide the groove 13 into non-electrically connected first blind hole 131 and second blind hole 132, and conductive materials are located in the first blind hole 131 and the second blind hole 132.

[0057] In this embodiment, the bottom of the groove 13 is located on one of the circuit layers 121 on the core board 12 and at least partially overlaps with the circuit layer 121. Specifically, the bottoms of the first blind hole 131 and the second blind hole 132 in the groove 13 are both located on the circuit layer 121.

[0058] In this embodiment, the networks of the first blind hole 131 and the second blind hole 132 are disconnected to form two independent holes. Further, the circuit layer 121 includes non-conductive circuits 1211 and 1212. The conductive material at the bottom of the first blind hole 131 contacts the circuit 1211, and the conductive material at the bottom of the second blind hole 132 contacts the circuit 1212. In one embodiment, the circuits at the position of the circuit layer 111 corresponding to the first blind hole 131 and the second blind hole 132 at the opening position of the groove 13 may also be non-conductive.

[0059] In this embodiment, the bottom of the groove 13 is located on one of the circuit layers 121 of the core board 12, and the bottoms of the first blind hole 131 and the second blind hole 132 are located on one of the circuit layers 121 of the core board 12. In another embodiment, the groove 13 includes staggered multi-layer bottoms, and the staggered multi-layer bottoms are respectively located on multiple circuit layers of several core boards. Specifically, please refer to Figure 4b , which is a schematic structural diagram of the sixth embodiment of the circuit board of the present invention. In this embodiment, the staggered multi-layer bottoms of the groove 13 are respectively located on two circuit layers 121 and 122 of the circuit board. Further, the bottom of the first blind hole 131 overlaps with the circuit layer 121, the bottom of the second blind hole 132 overlaps with the circuit layer 122, and the conductive material in the first blind hole 131 contacts the circuit layer 121 to electrically connect the circuit layer 111 at the opening position of the first blind hole 131 to the circuit layer 121 at the bottom of the first blind hole 131. The conductive material in the second blind hole 132 contacts the circuit layer 122 to electrically connect the circuit layer 111 at the opening position of the second blind hole 132 to the circuit layer 122 at the bottom of the second blind hole 132. In one embodiment, the circuits at the positions corresponding to the first blind hole 131 and the second blind hole 132 in the circuit layer 111 at the opening positions of the first blind hole 131 and the second blind hole 132 may also be not connected to each other.

[0060] In the above Embodiments 3 to 6, the groove 13 can be located in the middle of the circuit board as in Embodiment 2. And in Embodiments 1 to 6 of the present application, by changing the shape of the traditional hole from circular to a shape with an elongated cross-section, so that the size of the cross-section in the first direction is larger than that in the second direction, the cross-sectional area is increased to a certain extent, and thus the aspect ratio is reduced and the electroplating ability is improved.

[0061] In another embodiment of the present application, the shape of the hole may not be changed, and it can still be set as circular, and the diameter at the axial opening position is made larger than that at the position far from the opening. However, in this embodiment, the diameter of the hole needs to be increased as much as possible so that there is enough space in the hole for electroplating. Specifically, the ratio of the depth of the hole to the diameter at the opening position of the hole is less than 2.

[0062] In one embodiment, if the hole is circular and the cross-sectional area is large enough, in order to further ensure that the electroplating solution has enough exchange space, a boss as described in Embodiments 2 to 5 above can also be provided at the bottom of the hole to reduce the aspect ratio of the hole at the bottom of the hole, so that any part in the air can contact the conductive material during electroplating.

[0063] The present application also provides a manufacturing method of the circuit board described in the above Embodiments 1 to 6. Please refer to Figure 5 , which is a schematic flowchart of the manufacturing method of Embodiments 1 to 4 of the present application, and includes:

[0064] Step S41: Provide a plurality of core boards arranged in a stacked manner, and the surface of the core board includes a circuit layer.

[0065] Provide a fabricated circuit board. Generally, a circuit board is usually composed of core boards arranged in a stacked manner, and the surface of the core board has a circuit layer. Among them, the core board is a copper clad laminate, which is the basic material for fabricating a circuit board, including a base board and a copper foil covering the base. The base board is made by impregnating materials such as paper base board, fiberglass cloth base board, synthetic fiber cloth base board, non-woven fabric base board, and composite base board with resin to make bonding sheets, and is made by combining multiple bonding sheets. Then, a copper foil is covered on one side or both sides of the fabricated base board, and then hot-pressed and cured to make a copper clad laminate. The circuit layer is arranged on the copper foil on the surface of the core board. When the core boards are stacked, they are hot-pressed through prepregs to make a circuit board.

[0066] Step S42: Set a slot on the circuit board that penetrates through some of the core boards.

[0067] Usually, when connecting the circuits on the outermost layer of the circuit board, through holes penetrating the circuit board are set on the outermost layer of the circuit board. And if the outer layer of the circuit board needs to be connected to the inner layer or the inner layer to the inner layer, blind holes penetrating from the outer layer to the specified inner layer or blind holes penetrating from the specified inner layer to another specified inner layer are set on the circuit board, and then electroplating is carried out in the blind holes to make them conductive. Since the bottom of the blind hole is closed, when the circuit layer that the blind hole needs to conduct is relatively deep, due to the limitation of the aspect ratio, the electroplating solution cannot enter the bottom of the blind hole during electroplating. Therefore, in this application, to overcome this problem, the common circular blind holes are changed to slots, and the dimension of the slot in the first direction on the cross-section of the slot is larger than the dimension in the second direction. In one embodiment, the depth of the slot and the dimension of the slot in the first direction on the cross-section of the slot are less than 1.2.

[0068] Step S43: Form a conductive substance in the slot to connect the circuit layers in at least two of the core boards.

[0069] After setting the slot, if the slot is to electrically connect the connected circuits, a conductive substance needs to be set in the slot. Specifically, electroplating is carried out in the slot to make the electroplating liquid enter the slot and contact any part of the slot, thereby forming a conductive substance. In one embodiment, the slot can be filled with a conductive substance, and in another embodiment, only the side walls of the slot can have a conductive substance.

[0070] Please refer to Figure 6 , Step S42 specifically includes:

[0071] Step S421: Open a slot on the circuit board, and the bottom of the slot is not connected to the circuit layer to be connected.

[0072] A slot is formed on the circuit board by using a mechanical drill or a mechanical milling machine. Since the precision of the mechanical drill or the mechanical milling machine is not high, in order to avoid damaging the circuit layer during the formation of the slot, when using the mechanical drill or the mechanical milling machine to form the slot, the bottom of the slot is not connected to the circuit layer, that is, there is a certain thickness between the circuit layer and the bottom of the slot.

[0073] Step S422: Process the bottom of the slot so that a part of the bottom of the slot is connected to the circuit layer to be connected, and the other part forms a boss.

[0074] The bottom of the slot is processed by using a laser drill so that the bottom of the slot is connected to the circuit layer to be connected. During this process, a part of the bottom of the slot can be connected to the circuit layer to be connected, and the other part forms a boss. In this way, the depth-to-width ratio of the bottom of the slot can be further reduced by the boss, or the boss can be removed.

[0075] In this embodiment, the fabricated slot is one and is used to connect two different circuit layers, and the circuits on each circuit layer are electrically connected.

[0076] Please refer to Figure 7 , which is the method for fabricating the circuit board described in Embodiments 3 to 4 of the present application. Compared with Figure 6 , the difference is that after step S43, this method further includes:

[0077] Step S431: Cover a protective layer on the surface of the conductive material.

[0078] Specifically, after electroplating and filling the conductive material in the slot, electroplating is performed on the surface of the conductive material exposed on the surface of the slot to form a protective layer covering the conductive material. In this embodiment, the material of the protective layer is tin.

[0079] Step S432: Remove the protective layer at the position corresponding to the boss on the surface of the conductive material.

[0080] The protective layer at the position corresponding to the boss on the surface of the conductive material is removed by using a laser to expose the conductive material corresponding to the position of the boss.

[0081] Step S433: Remove the conductive material exposed above the boss to divide the slot into a first blind hole and a second blind hole.

[0082] The conductive material exposed above the boss is removed by using alkaline etching to divide the slot into a first blind hole and a second blind hole. The first blind hole and the second blind hole are filled with the conductive material. At this time, when removing the conductive material above the boss, the protective layer can protect the integrity of the conductive material in the first blind hole and the second blind hole and will not affect the electrical conductivity of the first blind hole and the second blind hole.

[0083] Step S434: Fill an insulating material above the boss to electrically disconnect the first blind hole and the second blind hole.

[0084] Fill an insulating material above the boss to further electrically disconnect the first blind hole and the second blind hole.

[0085] In this embodiment, the first blind hole and the second blind hole are independent holes. It should be noted that when the bottoms of the first blind hole and the second blind hole penetrate through the same layer of circuit layer, the circuits contacted by the conductive materials at the bottom of the first blind hole and the circuits contacted by the conductive materials at the bottom of the second blind hole are not connected to each other. When the bottoms of the first blind hole and the second blind hole penetrate through different layers of circuit layers, the circuit layers contacted by the conductive materials at the bottoms of the first blind hole and the second blind hole are different layers.

[0086] In this embodiment, only some related structures of the circuit board are described, and other structures are the same as those of the circuit board in the prior art, and will not be elaborated here.

[0087] The present invention changes the aspect ratio of the holes used to connect circuit layers. Specifically, on the one hand, the shape of the hole is changed so that the dimension of its cross-section in the first direction is larger than the dimension in the second direction to form a groove, and the ratio of the depth of the groove to the dimension in the first direction is less than 1.2, thereby reducing the aspect ratio and enabling the bottom of the groove to have sufficient space for electroplating, so that the electroplating solution can contact any position in the groove. On the other hand, without changing the shape of the hole, the hole is circular, but the ratio of the depth of the hole to the diameter of the hole is less than 2, so that the hole has sufficient space for electroplating to form a conductive material. The present invention can, on the one hand, improve the electroplating ability of blind holes, and on the other hand, can also improve the product wiring density of printed circuit boards.

[0088] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied to other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A circuit board, characterized in that, The circuit board includes: A plurality of core boards stacked, wherein at least part of the surface of the core boards includes circuit layers; Wherein, there is a slot on the circuit board that penetrates through part of the core boards, and a conductive substance is formed in the slot for connecting the circuit layers in at least two of the core boards; The size of the slot in the first direction on the cross-section of the slot is larger than the size in the second direction, so that the electroplating liquid can contact any part in the slot for electroplating to form the conductive substance; the ratio of the depth of the slot to the size of the slot in the first direction on the cross-section of the slot is less than 1.2; the slot is a blind slot, and there is a boss at the bottom of the slot, and a blind hole is formed between the side wall of the boss and the opposite side wall of the slot, and the ratio of the height of the boss to the diameter of the blind hole is less than 1; the slot includes staggered multi-layer bottoms, and the staggered multi-layer bottoms are respectively located on multiple circuit layers of a plurality of core boards; The number of the bosses is one, and the boss is located in the center of the bottom of the slot, so that a first blind hole and a second blind hole are formed at the bottom of the slot; the conductive substance is located in the first blind hole and the second blind hole, and an insulating substance is formed above the boss to electrically insulate the first blind hole and the second blind hole; wherein, the conductive substances on the bottom surfaces of the first blind hole and the second blind hole contact different layer circuit layers.

2. The circuit board according to claim 1, wherein The bottom of the slot is located on one of the circuit layers of the plurality of core boards and at least partially overlaps with the circuit layer.

3. The circuit board according to claim 2, wherein The conductive substance covers the boss and is flush with the open end of the slot.

4. A circuit board, characterized in that, The circuit board includes: A plurality of core boards stacked, and at least part of the surface of the core boards includes circuit layers; Wherein, a hole is formed in the circuit board in the thickness direction, and a conductive substance is formed in the hole for connecting the circuit layers in at least two of the core boards; The sizes of the cross-section of the hole in two different directions are different, or the spatial sizes in the axial direction are different, so that the electroplating liquid enters from the position with the larger size to the position with the smaller size, and from the position with the larger axial space to the position with the smaller axial space, to form the conductive substance; the ratio of the size of the hole in the thickness direction to the larger size of the cross-section of the hole is less than 1.2; The hole includes staggered multi-layer bottoms, and the staggered multi-layer bottoms are respectively located on multiple circuit layers of a plurality of core boards; the bottom of the hole at least partially overlaps with the circuit layer; At least part of the bottom of the hole has a boss, the boss is located at the middle position of the bottom of the hole, and divides the hole into a non-connected first blind hole and a second blind hole, the conductive substance is located in the first blind hole and the second blind hole, and an insulating substance is formed above the boss to electrically insulate the first blind hole and the second blind hole; wherein, the conductive substances on the bottom surfaces of the first blind hole and the second blind hole contact different layer circuit layers; A blind hole is formed between the side wall of the boss and the opposite side wall of the hole, and the ratio of the height of the boss to the diameter of the blind hole is less than 1.

5. A method for manufacturing a circuit board, which is used to prepare the circuit board according to any one of claims 1-3, characterized in that, Including: Providing a plurality of core boards stacked, and the surface of the core boards includes circuit layers; Providing a slot on the circuit board that penetrates through part of the core boards; A conductive material is formed in the groove to connect the circuit layers in at least two of the core boards; Wherein, the dimension of the groove in the first direction on the cross-section is larger than the dimension in the second direction.

6. The manufacturing method according to claim 5, wherein The step of forming a groove penetrating through part of the core boards on the circuit board specifically includes: A groove is formed on the circuit board, and the bottom of the groove is not communicated with the circuit layer to be connected; The bottom of the groove is processed so that part of the bottom of the groove is communicated to the circuit layer to be connected, and the other part forms a boss.

7. The manufacturing method according to claim 5, wherein After the step of forming a conductive material in the groove to connect the circuit layers in at least two of the core boards, the following steps are further included: A protective layer is covered on the surface of the conductive material; The protective layer at the position corresponding to the boss on the surface of the conductive material is removed; The conductive material exposed above the boss is removed to divide the groove into a first blind hole and a second blind hole; An insulating material is formed above the boss to electrically insulate the first blind hole and the second blind hole.

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