Circuit board and manufacturing method thereof

Abstract

The invention discloses a circuit board and a manufacturing method thereof, the circuit board comprises a first circuit layer, an insulating layer, a second circuit layer, a first conduction part and a conductive part, and the first circuit layer comprises a connecting pad; the insulating layer is located on the surface of the first circuit layer; the second circuit layer is located on the surface of the insulating layer, and a first through hole penetrates through the second circuit layer, the insulating layer and the connecting pad; the first conduction part penetrates through the first through hole, the first conduction part comprises a first part and a second part which are connected with each other, the first part is located in the first through hole, the second part protrudes out of the surface of the connecting pad, and the first conduction part is formed in an electroplating mode; the conductive portion covers the second portion and extends to a portion of the surface of the connection pad. According to the circuit board and the manufacturing method thereof, the second part protrudes out of the surface of the connecting pad, so that the connection reliability of the conduction part and the second part can be improved, the connection stability of an electronic element on the circuit board is further improved, and meanwhile, the size of the connecting pad can be effectively reduced.

Description

Circuit Board and its Manufacturing Method Technical Field

[0001] This application relates to the field of circuit board technology, and in particular to a circuit board and a method for manufacturing the same. Background Technology

[0002] With the development of electronic products, today's electronic products are trending towards thinner, smaller, and more functional designs, and semiconductor packaging technology has also developed different packaging types accordingly. Among them, ball grid array (BGA) packaging is an advanced semiconductor packaging technology. Its characteristic is that it uses a packaging substrate to house semiconductor components, and multiple solder balls arranged in a grid array are placed on the back of the packaging substrate. The entire package unit is soldered and electrically connected to external electronic devices through multiple solder balls, so that more input / output connections can be accommodated on the same unit area of ​​the carrier to meet the requirements of highly integrated semiconductor chips. In order to meet the development trend of thinner, smaller, more multifunctional, higher-speed, and higher-frequency semiconductor packages, chips have been developed towards finer lines and smaller apertures.

[0003] However, existing circuit board manufacturing processes cannot simultaneously produce circuit grades with significant differences in copper thickness; moreover, the contact area between electronic components and circuit boards is small, resulting in poor electrical connection stability. Summary of the Invention

[0004] In view of this, in order to solve at least one of the above problems, it is necessary to provide a circuit board.

[0005] In addition, this application also needs to provide a method for manufacturing a circuit board.

[0006] This application provides a circuit board, including: a first circuit layer, an insulating layer, a second circuit layer, a first conductive portion, and a conductive portion. The first circuit layer includes a connecting pad. The insulating layer is located on the surface of the first circuit layer. The second circuit layer is located on the surface of the insulating layer away from the first circuit layer, and a first through hole is provided through the second circuit layer, the insulating layer, and the connecting pad. The first conductive portion is disposed through the first through hole and includes a first part and a second part that are interconnected. The first part is located in the first through hole, and the second part protrudes from the surface of the connecting pad away from the second circuit layer. The first conductive portion is formed by electroplating. The conductive portion covers the second part and extends to a portion of the surface of the connecting pad.

[0007] In some possible embodiments, the surface of the second part is an arcuate surface.

[0008] In some possible embodiments, the size of the first conductive portion decreases sequentially along the extension direction of the circuit board from the first circuit layer to the second circuit layer.

[0009] In some possible embodiments, the linewidth of the first line layer is smaller than the linewidth of the second line layer, the line spacing of the first line layer is smaller than the line spacing of the second line layer, and / or the thickness of the first line layer is smaller than the thickness of the second line layer.

[0010] In some possible embodiments, at least one third circuit layer is provided on the surface of the second circuit layer away from the first circuit layer, and a second through hole communicating with the first through hole is provided through the third circuit layer. A second conductive part connected to the first conductive part is provided in the second through hole, so that the third circuit layer is electrically connected to the second circuit layer; and / or, the circuit board further includes electronic components electrically connected to the conductive part.

[0011] This application also provides a method for manufacturing a circuit board, comprising: forming a first circuit layer on at least one surface of a substrate, the first circuit layer including a connector pad; forming a second circuit layer on the surface of the first circuit layer, an insulating layer being disposed between the second circuit layer and the first circuit layer; forming a first through-hole through the second circuit layer, the insulating layer and the connector pad; forming a first conductive portion in the first through-hole by electroplating; the first conductive portion including a first part and a second part connected to each other; the first part being located in the first through-hole; and the second part protruding from the surface of the connector pad away from the second circuit layer and extending into the substrate; removing the substrate to expose the first circuit layer and the second part; and forming a conductive portion on the surface of the second part, the conductive portion covering the second part and extending to a portion of the surface of the connector pad, thereby obtaining the circuit board.

[0012] In some possible embodiments, after the step of removing the substrate, the method further includes: thinning the first circuit layer and removing the edges of the second portion to form an arcuate surface on the surface of the second portion.

[0013] In some possible embodiments, the substrate includes a carrier plate, and a separation film and a first metal layer sequentially disposed on at least one surface of the carrier plate, wherein the separation film is separable from the first metal layer. The step of forming a first circuit layer on at least one surface of the substrate includes: patterning the first metal layer to form the first circuit layer; the step of forming a second circuit layer on the surface of the first circuit layer includes: sequentially forming an insulating layer and a second metal layer on the surface of the first circuit layer; forming a first through-hole through the second metal layer, the insulating layer, the connecting pad and the separation film; electroplating a first conductive portion in the first through-hole; and patterning the second metal layer to form the second circuit layer.

[0014] In some possible embodiments, after the step of forming the second circuit layer on the surface of the first circuit layer, the method further includes: forming at least one third circuit layer on the surface of the second circuit layer away from the first circuit layer; forming a second through-hole communicating with the first through-hole through the third circuit layer; and electroplating a second conductive portion connected to the first conductive portion in the second through-hole, so that the third circuit layer is electrically connected to the second circuit layer.

[0015] In some possible embodiments, after the step of forming the conductive portion on the surface of the second portion, the method further includes: connecting electronic components to the conductive portion.

[0016] Compared with the prior art, the circuit board and its manufacturing method provided in this application can effectively improve the connection reliability between the conductive part and the second part by setting the second part of the first conductive part to protrude from the surface of the connecting pad, thereby improving the connection stability of electronic components on the circuit board. At the same time, it can also effectively reduce the size of the connecting pad, which is conducive to the development of the circuit board towards thinner and smaller size.

[0017] Furthermore, the first and second circuit layers can have different circuit levels, forming circuit boards with different circuit levels, which improves the design flexibility of circuit levels; the first and second circuit layers have a large difference in thickness, which enables the fabrication of circuits with large thickness differences, thus improving the design flexibility of circuit thickness.

[0018] In addition, the circuit board manufacturing method of this application embodiment uses a coreless substrate to manufacture the circuit board, which can improve the circuit density while ensuring the performance requirements of the circuit board. Moreover, the manufacturing method is simple and easy to operate, which is conducive to achieving large-scale mass production. Attached Figure Description

[0019] Figure 1 is a schematic diagram of the circuit board provided in an embodiment of this application.

[0020] Figure 2 is a flowchart of the method for manufacturing a circuit board according to an embodiment of this application.

[0021] Figure 3 is a schematic diagram of the structure of the dry film laminated on the substrate provided in the embodiment of this application.

[0022] Figure 4 is a schematic diagram of the structure of forming a circuit dry film from the dry film on the substrate in Figure 3.

[0023] Figure 5 is a schematic diagram of the structure of the first metal layer in Figure 4 patterned to form the first circuit layer.

[0024] Figure 6 is a schematic diagram of the structure for adding layers on the surface of the first circuit layer in Figure 5.

[0025] Figure 7 is a schematic diagram of the structure that forms the first through hole by penetrating the first circuit layer, the insulating layer and the second metal layer in Figure 6.

[0026] Figure 8 is a schematic diagram of the structure in which the first conductive part is formed by electroplating in the first through hole in Figure 7.

[0027] Figure 9 is a schematic diagram of the structure in which the second metal layer in Figure 8 is formed into the second circuit layer.

[0028] Figure 10 is a schematic diagram of the structure in which layers are added to the surface of the second circuit layer in Figure 9.

[0029] Figure 11 is a schematic diagram of the structure of removing the substrate in Figure 10 to achieve board separation.

[0030] Figure 12 is a schematic diagram of the structure of the first line layer and the first conductive part of Figure 11 being rapidly etched.

[0031] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0032] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0033] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. When a component is said to be "set on" another component, it can be directly set on the other component or there may be an intervening component.

[0034] Referring to Figure 1, this application embodiment provides a circuit board 100, which includes: a first circuit layer 1, an insulating layer 2 located on the surface of the first circuit layer 1, a second circuit layer 3 located on the surface of the insulating layer 2 away from the first circuit layer 1, a first conductive portion 4, and a conductive portion 5. The first circuit layer 1 includes a connecting pad 11. A first through-hole 7 is provided through the second circuit layer 3, the insulating layer 2, and the connecting pad 11. The first conductive portion 4 is disposed through the first through-hole 7 and is formed by electroplating. The first conductive portion 4 includes a first portion 41 and a second portion 42 interconnected, the first portion 41 being located within the first through-hole 7, and the second portion 42 protruding from the surface of the connecting pad 11 away from the second circuit layer 3. The conductive portion 5 covers the second portion 42 and extends to a portion of the surface of the connecting pad 11.

[0035] The circuit board 100 may further include electronic components 6, and conductive portions 5 are used to connect the electronic components 6. By providing a second portion 42 of the first conductive portion 4 that protrudes from the connecting pad 11 and by having the conductive portion 5 cover the second portion 42, the contact area between the conductive portion 5 and the second portion 42 can be increased, thereby effectively improving the bonding strength of the electronic components 5 on the circuit board 100 and enhancing the connection stability of the electronic components 6. In addition, the protruding second portion 42 design reduces the area occupied by the conductive portion 5 on the connecting pad 11, effectively reducing the size of the connecting pad 11.

[0036] In some embodiments, the surface of the second part 42 is an arc-shaped surface, that is, the end face of the second part 42 is an arc-shaped surface, which can increase the contact area between the second part 42 and the conductive part 5, thereby improving the connection reliability between the conductive part 5 and the second part 42.

[0037] In some embodiments, along the direction from the first circuit layer 1 to the second circuit layer 3, the size of the first conductive portion 4 decreases sequentially along the extension direction a of the circuit board 100, thereby forming a trapezoidal cross-section. The narrow end of the first conductive portion 4 passes through the connecting pad 11, which helps to reduce the size of the connecting pad 11. In addition, the wide end of the first conductive portion 4 passes through the second circuit layer 3, which facilitates electrical connection with other add-on circuits and improves the accuracy of blind via stacking. Corresponding to the first conductive portion 4, along the direction from the first circuit layer 1 to the second circuit layer 3, the inner diameter of the first through hole 7 decreases sequentially to form a trapezoidal structure. The large-size end of the first through hole 7 is opened in the second circuit layer 3, and the small-size end is opened in the connecting pad 11, which helps to reduce the size of the connecting pad 11.

[0038] In some embodiments, the aperture of the first through hole 7 can be between 60μm and 150μm. If the aperture is too large, it is not easy to fill the first through hole 7 when electroplating the first conductive part 4, and the thickness uniformity of the first conductive part 4 is poor.

[0039] In some embodiments, the linewidth of the first circuit layer 1 is smaller than the linewidth of the second circuit layer 3, and the line spacing of the first circuit layer 1 is smaller than the line spacing of the second circuit layer 3. For example, the linewidth / line spacing of the first circuit layer 1 can reach 10μm / 10μm, while the linewidth / line spacing of the second circuit layer 3 can reach 30μm / 30μm, forming an asymmetric circuit board with a large difference in circuit level. Traditional circuit board manufacturing processes require that the circuit levels on both sides of the circuit board be consistent. Compared with traditional circuit board manufacturing methods, the circuit board 100 of this application embodiment can realize a first circuit layer 1 and a second circuit layer 3 with different circuit levels, especially circuits with a large difference in linewidth / line spacing, improving the design flexibility of circuit levels.

[0040] In some embodiments, the thickness of the first circuit layer 1 is less than the thickness of the second circuit layer 3. For example, the thickness difference between the first circuit layer 1 and the second circuit layer 3 can exceed 7 μm. Traditional circuit board manufacturing processes require that the copper thickness of the circuit surfaces on both sides of the circuit board be equal or the thickness difference not exceed 7 μm. Compared with traditional circuit board manufacturing methods, the circuit board 100 of this application embodiment can realize the fabrication of circuits with large thickness differences, improving the design flexibility of different circuit layers in the circuit board 100.

[0041] The circuit board 100 further includes at least one third circuit layer 8 disposed on the surface of the second circuit layer 3 away from the first circuit layer 1. A second through-hole 81 communicating with the first through-hole 7 is provided through the third circuit layer 8. A second conductive part 9 connected to the first conductive part 4 is provided within the second through-hole 81, so that the third circuit layer 8 is electrically connected to the second circuit layer 3. More layers of circuitry can be fabricated by adding layers to meet the multifunctional needs of the circuit board 100.

[0042] In some embodiments, along the direction from the third circuit layer 8 to the second circuit layer 3, the inner diameter of the second through hole 81 decreases sequentially, forming a trapezoidal cross-section. The size of the second conductive portion 9 decreases sequentially along the extension direction a of the circuit board 100, so that the cross-section of the second conductive portion 9 forms a trapezoidal shape. The narrow end of the second through hole 81 is connected to the wide end of the first through hole 7, resulting in higher hole alignment. At the same time, the narrow end of the second conductive portion 9 contacts the wide end of the first conductive portion 4, enabling sufficient contact and forming a stable electrical conductive structure.

[0043] In some embodiments, the aperture of the second through hole 81 can be between 75 μm and 125 μm.

[0044] Please refer to Figure 2, and together with Figures 3 to 12, this application embodiment also provides a method for manufacturing the aforementioned circuit board 100. The manufacturing method includes: step S1, as shown in Figures 3 to 5, forming a first circuit layer 1 on at least one surface of the substrate 10, the first circuit layer 1 including a connection pad 11.

[0045] The specific steps for forming the first circuit layer 1 include: Step S11, as shown in FIG3, providing a substrate 10, the substrate 10 being a detachable substrate, including a carrier plate 101, and a separation film 102 and a first metal layer 103 sequentially disposed on at least one surface of the carrier plate 101, wherein the first metal layer 103 is separable from the separation film layer 102.

[0046] In some embodiments, the thickness of the separation membrane 102 may be 2~15 μm.

[0047] In some embodiments, the substrate 10 is a double-sided substrate, which can be used to form two circuit boards 100, effectively improving production efficiency.

[0048] Step S12, as shown in Figures 3 and 4, involves laminating a dry film 20 onto the surface of the first metal layer 103 and patterning the dry film 20 to form a circuit dry film 30.

[0049] The method for patterning dry film 20 specifically includes steps such as exposure and development for circuit fabrication.

[0050] Step S13, as shown in FIG5, remove the first metal layer 103 exposed by the dry film gap 301 of the circuit dry film 30 to form the first circuit layer 1.

[0051] In some embodiments, the first metal layer 103 exposed by the dry film gap 301 can be partially removed by chemical etching to form the first circuit layer 1. In other embodiments, the first metal layer 103 exposed by the dry film gap 301 can also be partially removed by laser ablation to form the first circuit layer 1.

[0052] Step S2, as shown in Figures 6 to 9, a second circuit layer 3 is formed on the surface of the first circuit layer 1. An insulating layer 2 is provided between the second circuit layer 3 and the first circuit layer 1. A first through hole 7 is formed through the second circuit layer 3, the insulating layer 2 and the connecting pad 11. A first conductive portion 4 is formed in the first through hole 7 by electroplating. The first conductive portion 4 includes a first part 41 and a second part 42 that are connected to each other. The first part 41 is located in the first through hole 7, and the second part 42 protrudes from the connecting pad 11 away from the surface of the second circuit layer 3 and extends into the substrate 10.

[0053] The second part 42 of the first conductive part 4 protrudes from the connecting pad 11, which can be used to fix the subsequently formed conductive part 5, playing an anchoring role, thereby improving the connection reliability between the conductive part 5 and the first conductive part 4 (as shown in Figure 1).

[0054] The specific steps for forming the second circuit layer 3 include: step S21, as shown in FIG6, forming an insulating layer 2 and a second metal layer 40 sequentially on the surface of the first circuit layer 1.

[0055] Specifically, the insulating layer 2 and the second metal layer 40 are pressed together on the surface of the first circuit layer 1 by a pressing method.

[0056] In step S22, as shown in FIG7, the first through hole 7 is formed by penetrating the second metal layer 40, the insulating layer 2, the connecting pad 11, and the separation membrane 102, and the surface of the carrier plate 101 is exposed through the first through hole 7. In this embodiment, when the first through hole 7 penetrates the separation membrane 102, the carrier plate 101 can act as a laser blocking layer, so that the bottoms of different first through holes 7 are at the same height, so that the height of the first conductive part 4 protruding from the connecting pad 11 remains consistent. It is understood that in other embodiments, the first through hole 7 may not penetrate the separation membrane 102.

[0057] The first through hole 7 is formed by laser drilling, and the diameter of the first through hole 7 is between 75μm and 125μm. Controlling the hole size within this range helps to reduce the size of the connecting pad 11, and also helps to fill the first through hole 7 during subsequent electroplating, thereby improving the thickness uniformity of the first conductive part 4.

[0058] In some embodiments, the inner diameter of the first through hole 7 decreases sequentially from the second metal layer 40 to the carrier plate 101, forming a hole with a trapezoidal cross-section. The narrow end of the first through hole 7 penetrates the connecting pad 11 of the first circuit layer 1, which can effectively reduce the size of the connecting pad 11. The wide end of the first through hole 7 penetrates the second metal layer 40 to facilitate subsequent electroplating in the first through hole 7.

[0059] Step S23, as shown in FIG8, the first conductive part 4 is formed by electroplating in the first through hole 7.

[0060] By electroplating and using vertical VCP to fill the holes, the thickness uniformity of the first conductive part 4 can be improved, and the surface uniformity of the first circuit layer 1 and the second circuit layer 3 can also be improved, with the surface uniformity of the circuit layer reaching more than 95%.

[0061] Step S24, as shown in FIG9, the second metal layer 40 is patterned to form the second circuit layer 3.

[0062] Specifically, the second metal layer 40 is formed into the second circuit layer 3 through exposure, development, etching, and other methods.

[0063] Following step S24, more circuits can be further formed on the surface of the second circuit layer 3 by adding layers as needed. Specifically, this includes the following steps: Step S25, as shown in Figure 10, forming at least one third circuit layer 8 on the surface of the second circuit layer 3 away from the first circuit layer 1. The third circuit layer 8 and the second circuit layer 3 are separated by another insulating layer 2.

[0064] Step S26, as shown in Figure 10, forms a second through hole 81 that communicates with the first through hole 7 by penetrating the third circuit layer 8.

[0065] Step S27, as shown in FIG10, a second conductive part 9 connected to the first conductive part 4 is formed by electroplating in the second through hole 81, so that the third circuit layer 8 is electrically connected to the second circuit layer 3.

[0066] Layering is achieved through lamination, and the thickness tolerance of the laminated plate can be controlled within ±25μm, which can effectively control the uniformity of the thickness of the added layer.

[0067] In some embodiments, along the direction from the third circuit layer 8 to the second circuit layer 3, the inner diameter of the second through hole 81 decreases sequentially, forming a trapezoidal cross-section. The size of the second conductive portion 9 decreases sequentially along the extension direction a of the circuit board 100, so that the cross-section of the second conductive portion 9 forms a trapezoidal shape. The narrow end of the second through hole 81 is connected to the wide end of the first through hole 7, resulting in higher alignment accuracy for each layer of holes and a hole stacking accuracy within 10 μm. At the same time, the narrow end of the second conductive portion 9 contacts the wide end of the first conductive portion 4, enabling sufficient contact and forming a stable electrical conductive structure.

[0068] Step S3, as shown in FIG11, remove the substrate 10 to expose the first circuit layer 1 and the second portion 42.

[0069] Since the separation membrane 102 and the first circuit layer 1 are separable, when removing the substrate 10, the carrier plate 101 and the separation membrane 102 can be removed.

[0070] After step S3, the method further includes step S30, as shown in FIG12, thinning the first circuit layer 1 and removing the edges of the second part 42 so that the surface of the second part 42 forms an arc-shaped surface.

[0071] By rapidly etching away residual metal, the accuracy of the first circuit layer 1 can be improved.

[0072] In addition, rapid etching can remove the surface edges of the second part 42, forming an arc-shaped surface. Since the etch rate of the protruding edges of the second part 42 is faster, they will be preferentially etched away during the thinning of the first circuit layer 1, forming an arc-shaped surface. This can further increase the contact area between the second part 42 and the subsequently formed conductive part 5 (as shown in Figure 1), and further improve the connection reliability between the conductive part 5 and the second part 42.

[0073] Step S4, as shown in FIG1, a conductive portion 5 is formed on the surface of the second portion 42, the conductive portion 5 covering the second portion 42 and extending to a portion of the surface of the connecting pad 11.

[0074] The conductive part 5 can be formed by curing solder paste. When applying solder paste, the solder paste is mainly applied to the second part 42. Through the flow of the solder paste, a portion will flow onto the surface of the connecting pad 11, thereby forming a conductive part 5 that covers the second part 42 and extends to part of the connecting pad 11.

[0075] Step S5, as shown in Figure 1, connect electronic components 6 to the conductive part 5 to obtain the circuit board 100.

[0076] By extending the second part 42 into the conductive part 5, the area of ​​the connecting pad 11 can be reduced, and the connection reliability between the conductive part 5 and the second part 42 can be effectively improved, thereby improving the connection reliability of the electronic component 6 on the circuit board 100 and improving the connection stability of the electronic component 6.

[0077] Compared to existing technologies, the circuit board 100 and its manufacturing method provided in this application, by setting the second part 42 of the first conductive part 4 to protrude from the surface of the connecting pad 11, can effectively improve the connection reliability between the conductive part 5 and the second part 42, thereby improving the connection stability of the electronic component 6 on the circuit board 100. Simultaneously, it can effectively reduce the size of the connecting pad 11, which is beneficial for the development of the circuit board 100 towards thinner and smaller designs. The circuit levels of the first circuit layer 1 and the second circuit layer 3 can be different, forming circuit boards 100 with different circuit levels, improving the design flexibility of circuit levels. Moreover, the significant difference in thickness between the first circuit layer 1 and the second circuit layer 3 enables the fabrication of circuits with large thickness differences, improving the design flexibility of circuit thickness. The circuit board 100 in this application embodiment is manufactured using a coreless substrate 10, which, while ensuring the performance requirements of the circuit board 100, can increase the circuit density. Furthermore, the manufacturing method is simple and easy to operate, facilitating large-scale mass production.

Claims

1. A circuit board, characterized in that, include: A first wiring layer, the first wiring layer including a connection pad; An insulating layer is located on the surface of the first circuit layer; A second circuit layer is located on the surface of the insulating layer away from the first circuit layer, and a first through hole is provided through the second circuit layer, the insulating layer, and the connecting pad; a first conductive portion is provided through the first through hole, and the first conductive portion includes a first part and a second part that are connected to each other, the first part is located in the first through hole, and the second part protrudes from the surface of the connecting pad away from the second circuit layer, and the first conductive portion is formed by electroplating; and a conductive portion covers the second part and extends to a portion of the surface of the connecting pad.

2. The circuit board as described in claim 1, characterized in that, The surface of the second part is curved.

3. The circuit board as described in claim 1, characterized in that, Along the direction from the first circuit layer to the second circuit layer, the size of the first conductive portion decreases sequentially along the extension direction of the circuit board.

4. The circuit board as described in claim 1, characterized in that, The line width of the first line layer is smaller than the line width of the second line layer, and the line spacing of the first line layer is smaller than the line spacing of the second line layer.

5. The circuit board as described in claim 1, characterized in that, At least one third circuit layer is provided on the surface of the second circuit layer away from the first circuit layer, and a second through hole communicating with the first through hole is provided through the third circuit layer. A second conductive part connected to the first conductive part is provided in the second through hole, so that the third circuit layer is electrically connected to the second circuit layer; and / or the circuit board further includes electronic components electrically connected to the conductive part.

6. A method for manufacturing a circuit board, characterized in that, include: A first circuit layer is formed on at least one surface of a substrate, the first circuit layer including a connector pad; a second circuit layer is formed on the surface of the first circuit layer, an insulating layer is provided between the second circuit layer and the first circuit layer, a first through hole is formed through the second circuit layer, the insulating layer and the connector pad, a first conductive portion is formed in the first through hole by electroplating, the first conductive portion includes a first part and a second part that are connected to each other, the first part is located in the first through hole, and the second part protrudes from the connector pad away from the surface of the second circuit layer and extends into the substrate; Remove the substrate to expose the first circuit layer and the second portion; A conductive portion is formed on the surface of the second portion, the conductive portion covering the second portion and extending to a portion of the surface of the connecting pad, thereby obtaining the circuit board.

7. The method for manufacturing a circuit board as described in claim 6, characterized in that, After removing the substrate, the method further includes: thinning the first circuit layer and removing the edges of the second portion to form an arc-shaped surface on the surface of the second portion.

8. The method for manufacturing a circuit board as described in claim 6, characterized in that, The substrate includes a carrier plate, and a separation film and a first metal layer sequentially disposed on at least one surface of the carrier plate. The separation film is separable from the first metal layer. The step of forming a first circuit layer on at least one surface of the substrate includes: patterning the first metal layer to form the first circuit layer. The step of forming a second circuit layer on the surface of the first circuit layer includes: sequentially forming an insulating layer and a second metal layer on the surface of the first circuit layer; forming a first through-hole through the second metal layer, the insulating layer, the connecting pad, and the separation film; electroplating a first conductive portion in the first through-hole; and patterning the second metal layer to form the second circuit layer.

9. The method for manufacturing a circuit board as described in claim 6, characterized in that, After the step of forming the second circuit layer on the surface of the first circuit layer, the method further includes: forming at least one third circuit layer on the surface of the second circuit layer away from the first circuit layer; forming a second through hole communicating with the first through hole through the third circuit layer; and electroplating a second conductive portion connected to the first conductive portion in the second through hole, so that the third circuit layer is electrically connected to the second circuit layer.

10. The method for manufacturing a circuit board as described in claim 6, characterized in that, After the step of forming the conductive portion on the surface of the second portion, the method further includes: connecting electronic components to the conductive portion.

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