Circuit board and manufacturing method thereof

Abstract

The invention relates to a circuit substrate and a manufacturing method thereof, a first via hole in the circuit substrate comprises a first through hole penetrating through the substrate and a first conductive part arranged on the inner wall of the first through hole, and a first conductive circuit is electrically connected with the first conductive part. The second via hole comprises a second through hole penetrating through the first insulating part, a third through hole penetrating through the second insulating part, a second conductive part arranged on the inner wall of the second through hole and a connecting pad arranged on the inner wall of the third through hole; the second conductive circuit is arranged on the surfaces of the connecting pad and the second insulating part; wherein the first conductive circuit is electrically isolated from the second conductive circuit through the first insulating layer. According to the manufacturing method of the circuit substrate, the manufacturing process is simplified, the material cost is saved, the production period is shortened, and the manufactured circuit substrate is thinner, higher in reliability and better in impedance continuity.

Description

Technical Field

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

[0002] Since the outer hole of the coaxial hole has shielding effect on the signal of the inner hole, the inner hole has better signal transmission capability. Therefore, this coaxial hole has many applications in signal conduction, especially in Internet Connection Sharing (ICs). Coaxial through-silicon-via is widely used. At present, it is relatively less used in printed circuit boards (PCBs), mainly in interposer products and millimeter wave laser (mm wave radar) backfeed design.

[0003] At present, the process of making coaxial holes in the PCB industry is complex, with a long production cycle, high material costs, and poor reliability. 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 propose a circuit substrate and a manufacturing method thereof, wherein the circuit substrate includes a coaxial hole. The manufacturing method is conducive to simplifying the manufacturing process, saving material costs, shortening the production cycle, and at the same time improving the reliability of the circuit substrate.

[0005] An embodiment of the present application provides a circuit substrate, the circuit substrate comprising a substrate, a first via, a first conductive circuit, a first insulating layer, a second via and a second conductive circuit, the first via comprising a first through hole penetrating the substrate and a first conductive portion arranged on the inner wall of the first through hole; the first conductive circuit is located on the surface of the substrate and electrically connected to the first conductive portion; the first insulating layer comprises a first insulating portion arranged in the first through hole, and a second insulating portion arranged on the surface of the first insulating portion and extending to the surface of the first conductive circuit; the second via comprises a second through hole penetrating the first insulating portion, a third through hole penetrating the second insulating portion and coaxially arranged with the second through hole, a second conductive portion arranged on the inner wall of the second through hole, and a connection pad arranged on the inner wall of the third through hole and electrically connected to the second conductive portion; the second conductive circuit is arranged on the surface of the connection pad and the second insulating portion; wherein the first conductive circuit is electrically isolated from the second conductive circuit by the first insulating layer.

[0006] In some possible embodiments, a surface of the connection pad facing away from the second conductive portion is flush with a surface of the second insulating portion facing away from the first insulating portion; or a surface of the connection pad facing away from the second conductive portion is lower than a surface of the second insulating portion facing away from the first insulating portion.

[0007] In some possible embodiments, along a thickness direction of the circuit substrate, a size of the first conductive portion is equal to a size of the second conductive portion.

[0008] In some possible embodiments, along the extension direction of the circuit substrate, the size of the connection pad is larger than the size of the second through hole and smaller than the size of the first through hole.

[0009] In some possible embodiments, the material of the first insulating layer includes insulating resin.

[0010] In some possible embodiments, a second insulating layer is provided in the second through hole provided with the second conductive portion and the third through hole provided with the connection pad.

[0011] The present application also provides a method for manufacturing a circuit substrate, comprising:

[0012] A first through hole is formed through the substrate, and a first metal layer is formed on an inner wall of the first through hole and on a surface of the substrate, wherein the first metal layer in the first through hole constitutes a first conductive portion;

[0013] forming a first insulating portion in the first through hole in which the first conductive portion is formed;

[0014] A second through hole is formed through the first insulating portion, a second conductive portion is formed on an inner wall of the second through hole, and a connection pad is formed on an end surface of the second conductive portion, wherein the connection pad extends to a portion of a surface of the first insulating portion;

[0015] forming a second insulating portion on a surface of the first insulating portion that is not covered by the connection pad, wherein the first insulating portion and the second insulating portion constitute a first insulating layer; and

[0016] A third metal layer is formed on the surface of the connecting pad and the second insulating portion, and the first metal layer located on the surface of the substrate is patterned to form a first conductive circuit electrically connected to the first conductive portion, and the third metal layer is patterned to form a second conductive circuit electrically connected to the connecting pad, wherein the first conductive circuit is electrically isolated from the second conductive circuit by the first insulating layer.

[0017] In some possible embodiments, the step of forming a second through hole through the first insulating portion, forming a second conductive portion on an inner wall of the second through hole, and forming a connection pad on an end surface of the second conductive portion, wherein the connection pad extends to a portion of the surface of the first insulating portion, specifically includes:

[0018] forming the second through hole through the first insulating portion;

[0019] forming a second metal layer on the inner wall of the second through hole, the second metal layer extending to the end surface of the first insulating portion, the second metal layer located in the second through hole constituting the second conductive portion, the second metal layer located on the end surfaces of the second conductive portion and the first insulating portion comprising a first portion and a second portion connected to each other, the first portion connected to the end surface of the second conductive portion; and

[0020] The second portion is removed to expose the first insulating portion, and the first portion constitutes the connection pad.

[0021] In some possible embodiments, in the step of forming the second metal layer on the inner wall of the second through hole, the second metal layer further extends to the surface of the first metal layer, and the second portion further includes the second metal layer located on the surface of the first metal layer;

[0022] In the step of forming the second insulating portion, the second insulating portion further extends to a surface of the first metal layer.

[0023] In some possible embodiments, after the step of forming the second metal layer on the inner wall of the second through hole, the manufacturing method further includes:

[0024] A second insulating layer is filled in the second through hole formed with the second metal layer.

[0025] Compared with the prior art, the manufacturing method of the circuit substrate provided in the embodiment of the present application has the following advantages:

[0026] Beneficial effects:

[0027] 1) The method of local metal reduction is mainly used to form a height difference between the connection pad and the first metal layer, and then the second insulating part is formed by local selective layer addition, so that the first via and the second via are separated in the horizontal direction. The whole board surface pressing process is not used, and only the area where the coaxial hole is required is processed. Compared with the PP pressing and post-pressing process of the whole board, the process of local metal reduction and local selective layer addition is conducive to reducing material costs and shortening manufacturing cycles.

[0028] 2) The insulating resin material filled in the stacked structure does not contain glass fiber, which can reduce the CAF problem, is also conducive to the thinning of the circuit substrate, and is conducive to the first conductive hole and the second conductive hole being close to the same length, increasing the signal shielding effect of the first conductive hole on the second conductive hole, and increasing the integrity of the signal transmission of the second conductive hole.

[0029] 3) When the dry film is partially covered with metal, the dry film coverage area should be larger than the area of ​​the second through hole. First, it can prevent the hole wall from being etched sideways during etching. Second, it can increase the distance between the second through hole and the corner of the first through hole, that is, the distance h1 of the dielectric layer at the corner, so that the dielectric layer distance h1 is close to the dielectric distance h2 in the coaxial hole, ensuring the continuity of the hole impedance. In addition, the embedded connection pad at the corner of the signal hole can increase the thickness of the metal layer at the corner, and the hole impedance can be adjusted downward to make it consistent with the impedance inside the hole, which also ensures the continuity of the hole impedance.

[0030] 4) The circuit substrate manufactured using the aforementioned circuit substrate manufacturing method is thinner, more reliable, and has better impedance continuity. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic cross-sectional structure diagram of a circuit substrate provided in one embodiment of the present application.

[0032] Figure 2 for Figure 1 Top view of the circuit board.

[0033] Figure 3 A schematic diagram of the manufacturing process of a circuit substrate provided in one embodiment of the present application.

[0034] Figure 4 It is a schematic diagram of forming a first through hole and a first metal layer in a substrate according to an embodiment of the present application.

[0035] Figure 5 For Figure 4 A schematic diagram showing a first insulating portion being filled in a first through hole.

[0036] Figure 6 For Figure 5 A schematic diagram showing a second through hole and a second metal layer formed on a first insulating portion.

[0037] Figure 7 For Figure 6 A schematic diagram of filling the second insulating layer in the second through hole is shown.

[0038] Figure 8 For Figure 7 The schematic diagram of the partial selective application of dry film on the second metal layer is shown.

[0039] Fig. 9 To remove Figure 8 A schematic diagram showing a second portion of the second metal layer being used to form an opening.

[0040] Fig.10 For Fig. 9 A schematic diagram of filling the opening with a second insulating portion is shown.

[0041] Fig.11 For Fig.10 The schematic diagram shows that a third metal layer is formed on the connection pad and the surface of the second insulating portion.

[0042] Main component symbols

[0043] Circuit board 100

[0044] Base plate 1,50

[0045] Dielectric layer 11

[0046] Circuit layer 12,13

[0047] First via 2

[0048] First through hole 21

[0049] The first conductive portion 22

[0050] First conductive circuit 3

[0051] Second via 4

[0052] The second through hole 41

[0053] The third through hole 42

[0054] The second conductive portion 43

[0055] Connection pad 44

[0056] Second conductive path 5

[0057] First insulating layer 6

[0058] First insulating portion 61

[0059] Second insulating portion 62

[0060] Second insulating layer 7

[0061] The first metal layer 10

[0062] The second metal layer 20

[0063] Part 1201

[0064] Part II 202

[0065] Opening 30

[0066] The third metal layer 40

[0067] Metal layer 501,502

[0068] Opening area A

[0069] Non-opening area B

[0070] Corner a,b

[0071] Direction x,z

[0072] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0073] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0074] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0075] It should be noted that, in the present application, if used, the terms "first", "second", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, "multiple" means two or more. Positional terms such as "upper", "lower", "left", and "right" are defined relative to the orientation of the components schematically placed in the accompanying drawings. It should be understood that these directional terms are relative concepts. They are used for description and clarification relative to, and they may change accordingly according to changes in the orientation of the components placed in the accompanying drawings. The term "direction" includes unidirectional or bidirectional along the straight line where the direction is located, and cannot be simply understood as unidirectional along the straight line where the direction is located.

[0076] In this application, if used, unless otherwise expressly specified and limited, the term "connection" should be understood in a broad sense, for example, "connection" can be fixed connection, detachable connection, or integrated; can be directly connected or indirectly connected through an intermediate medium. The term "and / or" used herein includes any and all combinations of one or more of the relevant listed items.

[0077] It will be understood that when a layer, region or component is referred to as being “on” another layer, region or component, it can be directly or indirectly on the other layer, region or component. That is, for example, intervening layers, regions or components may be present.

[0078] At present, the coaxial hole process produced by the PCB industry usually separates the inner hole and the outer hole in the horizontal direction by pressing the PP dielectric layer to achieve vertical and horizontal connection and conduction, so that the inner hole is connected to the outer hole area, and the inner hole can horizontally conduct other circuits or components. Studies have found that due to the presence of glass fiber in the pressed PP dielectric layer, the conductive anodic filament (CAF) leakage from layer to layer and hole to hole is increased, reducing the reliability of the product; moreover, due to the external pressure of the PP dielectric layer, the length of the inner hole is always greater than the length of the outer hole, which will affect the continuity of signal shielding and impedance; in addition, the aforementioned method has a complex process flow, a long manufacturing cycle, and a laminated PP dielectric layer, and the material cost is relatively high.

[0079] In order to solve the above problems, the embodiment of the present application provides a circuit substrate and a manufacturing method thereof, wherein the circuit substrate includes a coaxial hole, and the manufacturing method is conducive to simplifying the manufacturing process, saving material costs, shortening the production cycle, and improving the reliability of the circuit substrate. The circuit substrate can be used, but is not limited to, in PCB products related to coaxial holes.

[0080] See also Figure 1 and Figure 2 The circuit substrate 100 includes a substrate 1, a first conductive hole 2, a first conductive circuit 3, a first insulating layer 6, a second conductive hole 4 and a second conductive circuit 5. The first conductive hole 2 includes: a first through hole 21 penetrating the substrate 1, and a first conductive portion 22 provided on the inner wall of the first through hole 21. The first conductive circuit 3 is located on the surface of the substrate 1 and electrically connected to the first conductive portion 22. The first insulating layer 6 includes a first insulating portion 61 provided in the first through hole 21, and a second insulating portion 62 provided on the surface of the first insulating portion 61 and extending to the surface of the first conductive circuit 3. The second conductive hole 4 includes a second through hole 41 penetrating the first insulating portion 61, a third through hole 42 penetrating the second insulating portion 62 and coaxially provided with the second through hole 41, a second conductive portion 43 provided on the inner wall of the second through hole 41, and a connection pad 44 provided on the inner wall of the third through hole 42 and electrically connected to the second conductive portion 43. The second conductive circuit 5 is provided on the connection pad 44 and the surface of the second insulating portion 62. The first conductive circuit 3 is electrically isolated from the second conductive circuit 5 by the first insulating layer 6 .

[0081] See also Figure 1, the substrate 1 may be a single-layer dielectric layer, or a multi-layer substrate including at least one dielectric layer and at least one circuit layer. In some embodiments, the substrate 1 may be a multi-layer substrate, but is not limited thereto. The substrate 1 specifically includes: a dielectric layer 11, and circuit layers 12 and 13 located on two opposite surfaces of the dielectric layer 11. The surface of the circuit layer 12 facing away from the dielectric layer 11 constitutes the upper surface of the substrate 1, and the surface of the circuit layer 13 facing away from the dielectric layer 11 constitutes the lower surface of the substrate 1. Specifically, the first through hole 21 may be set through the upper surface and the lower surface of the substrate 1.

[0082] Specifically, the substrate 1 has an opening area A and a non-opening area B connected to the outer edge of the opening area A, wherein the first via 2 and the second via 4 are both located in the opening area A. The metal layer 12 and the metal layer 13 are located in the non-opening area B. The first via 2 and the second via 4 are electrically isolated from each other, and the first via 2 and the second via 4 can be electrically connected to the circuit layers 12 and 13 to achieve different conduction purposes.

[0083] Specifically, the patterns of the first conductive circuit 3 and the second conductive circuit 5 can be designed according to the requirements, and horizontal conduction can be achieved, or vertical conduction such as connection between circuit boards or connection between circuit boards and components can be achieved. In some embodiments, the second via 4 is used for signal transmission, that is, the second conductive circuit 5 can be a signal line, but it is not limited to this. The first via 2 can be used for grounding and play a role in signal shielding, so that the second via 4 has a better signal transmission capability, but it is not limited to this. The first through hole 21 and the second through hole 41 can be coaxially arranged, so that the first through hole 2 and the second through hole 4 together constitute a coaxial conductive through hole (coaxial via) structure, and it can be in the form of a through hole, a buried hole or a blind hole, but it is not limited to this. It can be understood that in other embodiments, the first through hole 21 and the second through hole 41 can also be non-coaxially arranged, so that the first through hole 2 and the second through hole 4 together constitute a non-coaxial conductive through hole structure. It is also understandable that in other embodiments, a plurality of second through holes 41 may be disposed in one first through hole 21 , so that a plurality of second through holes 4 are formed in the first conductive hole 2 .

[0084] In some embodiments, the dielectric layer 11 may be formed of a dielectric material, and the specific thickness is set according to the actual requirements of the circuit substrate 100 .

[0085] Please refer again Figure 1 Along the thickness direction z of the circuit substrate 100, the length of the first conductive portion 22 is substantially equal to the length of the second conductive portion 43, which can increase the signal shielding effect of the first conductive hole 2 (i.e., the outer hole) on the second conductive hole 4 (i.e., the inner hole), thereby increasing the integrity of the signal transmission of the second conductive hole 4.

[0086] Along the extension direction x of the circuit substrate 100, the size of the connection pad 44 is larger than the size of the second through hole 41 and smaller than the size of the first through hole 21. The inner diameter of the third through hole 42 can be controlled to make the inner diameter of the third through hole 42 larger than the inner diameter of the second through hole 41, so as to adjust the area of ​​the connection pad 44 beyond the second conductive portion 43. By appropriately increasing the area of ​​the connection pad 44, the distance between the inner hole corner a of the second conductive hole 4 (e.g., the signal hole) and the outer hole corner b of the first conductive hole 2 (e.g., the shielding hole) can be reduced, that is, the dielectric distance h1 at the corner can be reduced, so that the dielectric distance h1 at the corner is close to the dielectric distance h2 in the coaxial hole, thereby ensuring the continuity of the hole impedance.

[0087] The surface of the connection pad 44 facing away from the second conductive part 43 is flush with the surface of the second insulating part 62 facing away from the first insulating part 61. Alternatively, the surface of the connection pad 44 facing away from the second conductive part 43 is lower than the surface of the second insulating part 62 facing away from the first insulating part 61. By embedding the connection pad 44 in the second insulating part 62, the thickness of the connection pad 44 at the corner a can be increased, and the orifice impedance can be lowered to make the orifice impedance consistent with the impedance inside the hole, and the continuity of the orifice impedance can also be ensured.

[0088] The material of the first insulating layer 6 can be insulating resin, wherein the material of the first insulating portion 61 can be insulating resin, and the material of the second insulating portion 62 can also be insulating resin. Filling the insulating resin material in the first through hole 21 facilitates the filling of the first through hole 21, and it is easier to form the second through hole 41 on the resin material. The second insulating portion 62 is filled with insulating resin. Compared with the traditional laminated PP sheet, the insulating resin material does not contain glass fiber, which can reduce the CAF problem and is conducive to the thinning of the circuit substrate 100. In addition, filling the insulating resin to form the second insulating portion 62 can better control the thickness of the second insulating portion 62, which is conducive to further realizing that the first conductive portion 22 in the first conductive hole 2 (i.e., the outer hole) is equal in length to the second conductive portion 43 in the second conductive hole 4 (i.e., the inner hole), increasing the signal shielding effect of the outer hole on the inner hole, thereby increasing the signal transmission integrity of the second conductive hole 4.

[0089] In addition, the second insulating portion 62 and the connection pad 44 are formed only in a part of the opening area A, and there is no need for whole-board lamination and layer-building processing, which is beneficial to improving the utilization rate of the non-opening area B and the rationality of the circuit layout.

[0090] Please refer again Figure 1 A second insulating layer 7 is provided in the second through hole 41 having the second conductive portion 43 and the third through hole 42 having the connection pad 44. The second insulating layer 7 may be made of insulating resin. By filling the second insulating layer 7 in the second through hole 4, the strength of the circuit substrate 100 can be improved.

[0091] See also Figure 3The present application also provides a method for manufacturing the aforementioned circuit substrate 100, the manufacturing method comprising the following steps:

[0092] Step S1, see also Figure 4 A first through hole 21 is formed through the substrate 50 , and a first metal layer 10 is formed on the inner wall of the first through hole 21 and the surface of the substrate 1 , wherein the first metal layer 10 located in the first through hole 21 constitutes a first conductive portion 22 .

[0093] The first through hole 21 and the first conductive portion 22 constitute a first conductive hole 2 .

[0094] The difference between the substrate 50 and the aforementioned substrate 1 is that the substrate 50 is the original board of the substrate 1, which can be a dielectric layer or a multilayer board. Specifically, in this embodiment, the substrate 50 is a double-sided copper-clad board, including a dielectric layer 11 and metal layers 501 and 502 located on two opposite surfaces of the dielectric layer 11, and a first through hole 21 is opened through the upper and lower surfaces of the substrate 50. For example, the first through hole 21 can be formed by mechanical punching. The aperture size and shape of the first through hole 21 are processed as needed. In this embodiment, the first through hole 21 is a circular through hole.

[0095] The manufacturing method of the first metal layer 10 may be that after forming the hole, the inner wall of the through hole is metallized, and the first metal layer 10 with a certain thickness is formed on the inner wall of the first through hole 21, and the first metal layer 10 may extend to the surface of the metal layers 501 and 502. The hole wall metallization method includes but is not limited to chemical copper deposition, black hole, organic conductive film, and electrochemical deposition.

[0096] Step S2, also refer to Figure 5 , a first insulating portion 61 is formed in the first through hole 21 where the first conductive portion 22 is formed.

[0097] Specifically, the first insulating portion 61 is formed in the first through hole 21 formed with the first conductive portion 22 by filling and curing the first insulating portion 61, and the outer hole is filled. In addition, the two outer surfaces of the first insulating portion 61 need to be polished and leveled so that the two outer surfaces of the second insulating portion 62 are flush with the outer surface of the substrate 50.

[0098] Step S3, see also Figures 6 to 9 A second through hole 41 is formed through the first insulating portion 61 , a second conductive portion 43 is formed on the inner wall of the second through hole 41 , and a connecting pad 44 is formed on the end surface of the second conductive portion 43 , and the connecting pad 44 extends to a portion of the surface of the first insulating portion 61 .

[0099] The second through hole 41 , the second conductive portion 43 and the connecting pad 44 constitute a second conductive hole 4 .

[0100] The method for forming the second conductive portion 43 and the connection pad 44 specifically includes the following steps:

[0101] Step S31, as Figure 6 As shown, the second through hole 41 is formed through the first insulating portion 61 .

[0102] Specifically, the second through hole 41 is drilled on the first insulating portion 61 by machining, and the hole diameter is processed as needed.

[0103] Step S32, as Figure 6 As shown, a second metal layer 20 is formed on the inner wall of the second through hole 41, and the second metal layer 20 extends to the end face of the first insulating part 61. The second metal layer 20 located in the second through hole 41 constitutes a second conductive part 43. The second metal layer 20 located on the end faces of the second conductive part 43 and the first insulating part 61 includes a first part 201 and a second part 202 that are connected to each other, and the first part 201 is connected to the end face of the second conductive part 43.

[0104] Specifically, a second metal layer 20 of a desired thickness is formed on the end faces of the second through hole 41 and the first insulating portion 61 by hole wall metallization, wherein the "end face" refers to the surface on the same side as the upper surface or lower surface of the substrate 50. The hole wall metallization method includes but is not limited to chemical copper deposition, black hole, organic conductive film, electrochemical deposition and the like.

[0105] It can be understood that the second metal layer 20 may also extend onto the surface of the first metal layer 10 , and in this case, the second portion 202 also includes a portion of the second metal layer 20 located on the first metal layer 10 .

[0106] like Figure 7 As shown, in some embodiments, after forming the second metal layer 20, the preparation method further includes: forming a second insulating layer 7 in the second through hole 41 forming the second metal layer 20. Specifically, the second insulating layer 7 can be formed in the second through hole 41 by filling and curing an insulating resin or a composite. The outer surface of the second insulating layer 7 is ground flat by grinding.

[0107] Step S33, as Figure 8 and Fig. 9 As shown, the second portion 202 is removed to form an opening 30 , the first insulating portion 61 is exposed in the opening 30 , and the first portion 201 constitutes the connection pad 44 .

[0108] Specifically, the second portion 202 of the second metal layer 20 is etched away by coating and etching.

[0109] The first step, such as Figure 8As shown, the area where the second through hole 41 of the opening area A is located is selectively covered with a dry film, and at the same time, the non-opening area B that does not need to be processed is also covered, wherein the area corresponding to the second through hole 41 is covered to be larger than a certain area of ​​the second through hole 41, firstly, to prevent the subsequent metal etching process from side etching to the hole wall, and secondly, to increase the hole opening distance of the second through hole 41, reduce the distance between the inner hole corner of the second through hole and the outer hole corner of the first through hole 21, and thus reduce the dielectric layer distance h1 at the corner (such as Figure 1 As shown). The selective covering of the dry film can be achieved by selectively pasting the dry film or pasting the entire dry film and then exposing and developing. In this step, the covered area corresponding to the second through hole 41 corresponds to the second portion 202 of the second metal layer 20, thereby exposing the first portion 201 of the second metal layer 20.

[0110] The second step is, Fig. 9 As shown, the area not covered by the dry film (ie, the second portion 202 of the second metal layer 20) is removed with liquid medicine. The depth of metal removal in this step can be controlled by controlling the concentration, temperature and line speed of the liquid medicine.

[0111] The third step is Fig. 9 As shown, the covering dry film is removed, and the remaining first portion 201 located in the area of ​​the second through hole 41 constitutes the connection pad 44 .

[0112] Step S4, also refer to Fig.10 A second insulating portion 62 is formed on the surface of the first insulating portion 61 that is not covered by the connection pad 44 , and the first insulating portion 61 and the second insulating portion 62 constitute a first insulating layer 6 .

[0113] Specifically, in the previous step, the second part 202 of the second metal layer 20 is removed by reducing the surface metal, and an opening 30 is formed. The second insulating part 62 is formed by filling the opening 30 with an insulating resin or a composite and curing it, wherein the second insulating part 62 fills the opening 30 completely. The surface of the second insulating part 62 can be leveled by grinding so that the outer surface of the second insulating part 62 is flush with the outer surface of the connecting pad 44, thereby realizing that the connecting pad 44 of the second via 4 is embedded in the second insulating part 62.

[0114] This step uses the method of reducing the surface metal to form a height difference between the connection pad 44 and the first metal layer 10, and then forms the second insulating part 62 by resin filling, so that the first conductive hole 2 and the second conductive hole 4 are electrically isolated in the horizontal direction. Here, local selective layering is used to form this structure, and the process of pressing the PP on the whole board is not used. Only the connection area of ​​this structure is processed. Compared with the PP pressing and post-pressing process of the whole board, the process of reducing the surface metal and filling with resin has certain advantages in material cost and production time. Moreover, compared with the whole board pressing of PP sheets, the second insulating part 62 formed by filling with insulating resin can be made thinner, which is conducive to the thinning of the circuit substrate, the outer hole and the inner hole are close to the same length, and the signal shielding of the outer hole to the inner hole is increased, and the signal transmission integrity is increased.

[0115] Step S5, refer to Fig.11 and Figure 1 , a third metal layer 40 is formed on the surface of the connecting pad 44 and the second insulating portion 62, and the first metal layer 10 located on the surface of the substrate 50 is patterned to form a first conductive circuit 3 electrically connected to the first conductive portion 22, and the third metal layer 40 is patterned to form a second conductive circuit 5 electrically connected to the connecting pad 44, wherein the first conductive circuit 3 is electrically isolated from the second conductive circuit 5 by the first insulating layer 6.

[0116] Specifically, metallization is performed on the second insulating portion 62 and the metal surface to form a third metal layer 40. It can be understood that the metal surface here includes the connection pad 44 and the metal layer located in the non-opening area B. Among them, the conductive layer can be deposited by chemical copper deposition, black hole, organic conductive film, etc. and then electroplated to thicken. Finally, the first conductive circuit 3, the second conductive circuit 5, and the circuit layer 6 located in the non-opening area B are formed through patterning processes such as lamination, exposure, development, and etching.

[0117] It is understandable that after the patterning process, the circuit substrate 100 may be subjected to solder mask treatment.

[0118] In summary, the method for manufacturing the circuit substrate 100 provided in the embodiment of the present application has the following beneficial effects:

[0119] 1) The method of local metal reduction is mainly adopted to form a height difference between the connection pad 44 and the first metal layer 10, and then the second insulating part 62 is formed by local selective layer addition, so that the first conductive hole 2 and the second conductive hole 4 are separated in the horizontal direction. The whole board surface pressing process is not used, and only the area where the coaxial hole is required is processed. Compared with the PP pressing and post-pressing process of the whole board, the process of local metal reduction and local selective layer addition is conducive to reducing material costs and shortening manufacturing cycles.

[0120] 2) The insulating resin material filled in the stacked structure does not contain glass fiber, which can reduce the CAF problem, and is also beneficial to the thinning of the circuit substrate 100. It is also beneficial to make the first conductive hole 2 and the second conductive hole 4 close to the same length, thereby increasing the signal shielding effect of the first conductive hole 2 on the second conductive hole 4 and increasing the integrity of the signal transmission of the second conductive hole 4.

[0121] 3) When the dry film is partially covered with metal, the dry film coverage area should be larger than the area of ​​the second through hole 41. First, it can prevent the hole wall from being etched sideways during etching. Second, it can increase the hole mouth distance of the second conductive hole 4 and reduce the distance from the corner a of the second conductive hole 4 to the corner b of the first conductive hole 2, that is, the dielectric layer distance h1 at the corner, so that the dielectric layer distance h1 is close to the dielectric distance h2 in the coaxial hole, ensuring the continuity of the hole mouth impedance. In addition, the embedded connection pad 44 at the corner of the signal hole can increase the thickness of the metal layer at the corner, and the hole mouth impedance can be adjusted downward to make it consistent with the impedance inside the hole, which also ensures the continuity of the hole mouth impedance.

[0122] 4) The circuit substrate 100 manufactured using the aforementioned circuit substrate 100 manufacturing method is thinner, more reliable, and has better impedance continuity.

Claims

1. A circuit substrate, characterized in that: include: substrate; A first conductive hole, comprising a first through hole penetrating the substrate and a first conductive portion disposed on an inner wall of the first through hole; A first conductive circuit is located on the surface of the substrate and is electrically connected to the first conductive part; A first insulating layer includes a first insulating portion disposed in the first through hole, and a second insulating portion disposed on a surface of the first insulating portion and extending to a surface of the first conductive line; The second conductive via comprises a second through hole passing through the first insulating portion, a third through hole passing through the second insulating portion and coaxially disposed with the second through hole, a second conductive portion disposed on an inner wall of the second through hole, and a connection pad disposed on an inner wall of the third through hole and electrically connected to the second conductive portion; as well as A second conductive circuit is provided on the surface of the connection pad and the second insulating portion, Wherein, the first conductive circuit is electrically isolated from the second conductive circuit by the first insulating layer.

2. The circuit substrate according to claim 1, characterized in that: The surface of the connection pad facing away from the second conductive portion is flush with the surface of the second insulating portion facing away from the first insulating portion; Alternatively, a surface of the connection pad facing away from the second conductive portion is lower than a surface of the second insulating portion facing away from the first insulating portion.

3. The circuit substrate according to claim 1, wherein: Along the thickness direction of the circuit substrate, the size of the first conductive portion is equal to the size of the second conductive portion.

4. The circuit substrate according to claim 1, characterized in that: Along the extension direction of the circuit substrate, the size of the connection pad is larger than the size of the second through hole and smaller than the size of the first through hole.

5. The circuit substrate according to claim 1, characterized in that: The material of the first insulating layer includes insulating resin.

6. The circuit substrate according to claim 1, characterized in that: A second insulating layer is provided in the second through hole provided with the second conductive portion and the third through hole provided with the connection pad.

7. A method for manufacturing a circuit substrate, characterized in that: include: A first through hole is formed through the substrate, and a first metal layer is formed on an inner wall of the first through hole and on a surface of the substrate, wherein the first metal layer in the first through hole constitutes a first conductive portion; forming a first insulating portion in the first through hole in which the first conductive portion is formed; A second through hole is formed through the first insulating portion, a second conductive portion is formed on an inner wall of the second through hole, and a connection pad is formed on an end surface of the second conductive portion, wherein the connection pad extends to a portion of a surface of the first insulating portion; forming a second insulating portion on a surface of the first insulating portion that is not covered by the connection pad, wherein the first insulating portion and the second insulating portion constitute a first insulating layer; and A third metal layer is formed on the surface of the connecting pad and the second insulating portion, and the first metal layer located on the surface of the substrate is patterned to form a first conductive circuit electrically connected to the first conductive portion, and the third metal layer is patterned to form a second conductive circuit electrically connected to the connecting pad, wherein the first conductive circuit is electrically isolated from the second conductive circuit by the first insulating layer.

8. The method for manufacturing a circuit substrate according to claim 7, wherein: The step of forming a second through hole through the first insulating portion, forming a second conductive portion on an inner wall of the second through hole, and forming a connection pad on an end surface of the second conductive portion, wherein the connection pad extends to a portion of the surface of the first insulating portion, specifically includes: forming the second through hole through the first insulating portion; forming a second metal layer on the inner wall of the second through hole, the second metal layer extending to the end surface of the first insulating portion, the second metal layer located in the second through hole constituting the second conductive portion, the second metal layer located on the end surfaces of the second conductive portion and the first insulating portion comprising a first portion and a second portion connected to each other, the first portion connected to the end surface of the second conductive portion; and The second portion is removed to expose the first insulating portion, and the first portion constitutes the connection pad.

9. The method for manufacturing a circuit substrate according to claim 8, characterized in that: In the step of forming the second metal layer on the inner wall of the second through hole, the second metal layer further extends to the surface of the first metal layer, and the second portion further includes the second metal layer located on the surface of the first metal layer; In the step of forming the second insulating portion, the second insulating portion further extends to a surface of the first metal layer.

10. The method for manufacturing a circuit substrate according to claim 8, wherein: After the step of forming the second metal layer on the inner wall of the second through hole, the manufacturing method further includes: A second insulating layer is filled in the second through hole formed with the second metal layer.

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