A method for fabricating blind vias on a high-speed printed circuit board and the printed circuit board.

Abstract

This invention relates to the field of communication technology, and particularly to a method for fabricating blind vias on a high-speed printed circuit board and the printed circuit board itself. The method includes the following steps: providing an upper printed circuit board, a wiring layer, and a lower printed circuit board; laminating the upper printed circuit board, wiring layer, and lower printed circuit board together to form a multilayer printed circuit board; forming return vias penetrating the multilayer printed circuit board; forming signal vias connecting to the wiring layer on the multilayer printed circuit board; forming connection grooves on the multilayer printed circuit board to connect the signal vias and return vias; thermally melting the circuit board between the signal vias and the wiring layer to maximize the contact area between the signal vias and the wiring layer; electrically connecting the signal vias and return vias; severing the electrical connection between the signal vias and return vias; and filling the connection groove between the signal vias and return vias with a filling medium. This application can handle multilayer printed circuit boards of different thicknesses, increasing its practicality.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a method for manufacturing blind vias on a high-speed printed circuit board and the printed circuit board thereof. Background Technology

[0002] With the continuous improvement of high-speed interconnection link signal transmission rate, the signal integrity of printed circuit boards, as the carrier of devices and signal transmission, has an increasingly prominent impact on the electrical performance of communication systems. At the same time, in order to enable faster signal transmission, blind vias are usually opened inside the printed circuit board.

[0003] However, since the blind via fabrication method involves first drilling mechanically to the vicinity of the trace layer inside the printed circuit board, and then burning off the remaining dielectric with a laser to achieve zero tail post, the blind via fabricated by this method has electrolyte exchange problems, which makes it difficult to improve the thickness-to-diameter ratio of the electroplating. It can usually only achieve a depth of 10 mil (mil) and a thickness-to-diameter ratio of about 1:1, which is relative to the thickness of the printed circuit board, reaching up to 200 mil (mil). The current application of laser blind via is limited, and it is not possible to better perform electroplating inside the blind vias inside thicker printed circuit boards. Summary of the Invention

[0004] This invention discloses a method for fabricating blind vias on high-speed printed circuit boards and a printed circuit board, which is used to fabricate signal holes on printed circuit boards that enable high-speed signal transmission.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a method for fabricating blind vias on a high-speed printed circuit board, comprising the following steps:

[0007] S100: Provides an upper printed circuit board, a wiring layer and a lower printed circuit board, and laminates the upper printed circuit board, wiring layer and lower printed circuit board as a whole to form a multilayer printed circuit board;

[0008] S200: Forming a return hole through the multilayer printed circuit board on the multilayer printed circuit board;

[0009] S300: A signal via formed on a multilayer printed circuit board to the trace layer;

[0010] S400: A connection groove is formed on a multilayer printed circuit board to connect signal holes and return holes;

[0011] S500: Inside the signal via, the dielectric between the inner wall of the signal via and the trace layer is removed to precisely form the signal via on the surface of the trace layer.

[0012] S600: Through electroplating, the upper and lower printed circuit boards are electrically connected, and the signal holes and return holes are electrically connected.

[0013] S700: Disconnects the electrical connection between the signal port and the return port;

[0014] S800: Use a filling medium to fill the connection groove between the signal hole and the return hole.

[0015] In the aforementioned method for fabricating signal holes, this application first forms return vias and signal holes on a multilayer printed circuit board (PCB), and connects the return vias and signal holes via connecting grooves. Therefore, when dealing with thicker multilayer PCBs, this application first drills through the return vias on the PCB, then drills the signal holes into the trace layer, and connects the signal holes to the trace layer using laser burning technology. This allows the electrolyte to enter the connecting groove and the interior of the signal hole through the return vias, ensuring the flow of electrolyte among the three and achieving electroplating. This further enables electrical connection between the upper PCB, the trace layer, and the lower PCB, ensuring high-speed signal transmission. This application can handle multilayer PCBs of different thicknesses, achieving electroplating between signal holes and multilayer PCBs, thus increasing practicality.

[0016] In some embodiments, S200 specifically includes the following step: drilling a return hole through the multilayer printed circuit board using a mechanical drill.

[0017] In some embodiments, S300 specifically includes the following steps: using a mechanical drill to drill a signal hole through the upper printed circuit board on the multilayer printed circuit board, and the signal hole is connected to the trace layer.

[0018] In some embodiments, S400 specifically includes the following step: drilling a hole between the signal hole and the return hole using a conventional mechanical drill to form the connecting groove.

[0019] In some embodiments, S600 specifically includes the following steps: electroplating the signal hole and the return hole with an electrolyte to form a conductive layer for electrically connecting the trace layer and the upper printed circuit board and the lower printed circuit board, while the signal hole and the return hole are electrically connected through the conductive layer.

[0020] In some embodiments, S700 specifically includes the following steps: using a mechanical drill to drill through the conductive layer of the connection groove in the area covered by the orthographic projection of the multilayer printed circuit board.

[0021] In some embodiments, the opening radius C of both the signal hole and the return hole satisfies the following range: 180° < C < 360°.

[0022] In some embodiments, S800 specifically includes the following steps: using a mechanical drill to remove the burrs from the sidewall of the connecting groove so that the sidewall of the connecting groove is regular.

[0023] In some embodiments, the filling medium comprises resin.

[0024] In a second aspect, the present invention also provides a printed circuit board applied to the blind via fabrication method of high-speed flexible circuit board as described in any of the above claims, comprising: a multilayer printed circuit board, a return via, a signal via, and a filling medium;

[0025] The multilayer printed circuit board includes an upper printed circuit board, a wiring layer, and a lower printed circuit board. The upper printed circuit board and the lower printed circuit board are respectively disposed on opposite sides of the wiring layer. The return vias sequentially pass through the upper printed circuit board, the wiring layer, and the lower printed circuit board. The signal vias pass through the upper printed circuit board and communicate with the wiring layer. A connecting groove is provided between the return vias and the signal vias, and the filling medium is disposed inside the connecting groove. Attached Figure Description

[0026] Figure 1 This is a schematic flowchart of a high-speed blind hole fabrication method provided in an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram illustrating the specific process of the high-speed blind hole fabrication method provided in an embodiment of the present invention;

[0028] Figure 3 A top view of the signal hole and return hole provided in the embodiment of the present invention after fabrication, without the filling medium installed;

[0029] Figure 4 A top view of the signal hole and return hole after they have been fabricated, and the filling medium is installed, according to an embodiment of the present invention.

[0030] Figure 5 A schematic diagram of the portion of a multilayer printed circuit board inside which no filling medium is installed, provided in an embodiment of the present invention.

[0031] Figure 6 This is a partial schematic diagram of the filling medium installed inside a multilayer printed circuit board according to an embodiment of the present invention.

[0032] Among them: 1-multilayer printed circuit board, 11-upper layer printed circuit board, 12-trace layer, 13-lower layer printed circuit board, 2-return hole, 3-signal hole, 4-conducting layer, 5-connection groove, 6-filling medium. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] like Figures 1-6 As shown, in a first aspect, the present invention provides a method for manufacturing high-speed blind vias on a printed circuit board, comprising the following steps:

[0035] S100: Provide an upper printed circuit board 11, a wiring layer 12 and a lower printed circuit board 13, and press the upper printed circuit board 11, the wiring layer 12 and the lower printed circuit board 13 together to form a multilayer printed circuit board 1.

[0036] S200: A return hole 2 is formed on the multilayer printed circuit board 1, penetrating the multilayer printed circuit board 1;

[0037] S300: A signal hole 3 is formed on the multilayer printed circuit board 1 to the trace layer 12;

[0038] S400: A connecting groove 5 is formed on the multilayer printed circuit board 1 to connect the signal hole 3 and the return hole 2;

[0039] S500: Inside the signal hole 3, the inner wall of the signal hole 3 and the dielectric between it and the wiring layer 12 are removed to precisely form the signal hole 3 on the surface of the wiring layer 12.

[0040] S600: Electroplating enables electrical connection between the upper printed circuit board 11 and the lower printed circuit board 13, while signal hole 3 and return hole 2 are electrically connected.

[0041] S700: Disconnect the electrical connection between signal hole 3 and return hole 2;

[0042] S800: Use filling medium 6 to fill the connecting groove 5 between signal hole 3 and return hole 2.

[0043] In the above-described method for fabricating the signal hole 3, a return hole 2 and a signal hole 3 are first formed on the multilayer printed circuit board 1, and the return hole 2 and the signal hole 3 are connected by a connecting groove 5. Therefore, when dealing with a thicker multilayer printed circuit board 1, this application first drills through the return hole 2 on the multilayer printed circuit board 1, and then drills the signal hole 3 into the position of the wiring layer 12. The signal hole 3 is then connected to the wiring layer 12 by laser burning technology, so that the electrolyte can enter the connecting groove 5 and the interior of the signal hole 3 through the return hole 2, ensuring the flow of electrolyte among the three and realizing electroplating. This further realizes the electrical connection between the upper printed circuit board 11, the wiring layer 12 and the lower printed circuit board 13, ensuring that the signal can be transmitted at high speed. This application can handle multilayer printed circuit boards 1 of different thicknesses and realizes electroplating between the signal hole 3 and the multilayer printed circuit board 1, increasing its practicality.

[0044] In one possible implementation, S200 specifically includes the following steps: using a mechanical drill to drill a reflow hole 2 through the multilayer printed circuit board 1. In this application, the size of the reflow hole 2 can be changed according to actual needs. In the process of changing the diameter of the reflow hole 2, this application can use mechanical drills of different diameters to drill the hole. This application does not specifically limit the drill bit or the like used for drilling. It should be noted that the distance between the center of the reflow hole 2 and the center of the signal hole 3 is generally less than 40 mils, with a typical value of 24 mils. However, the above distance can be changed according to actual needs, and this application does not make specific limitations.

[0045] In one possible implementation, S300 specifically includes the following steps: a signal hole 3 penetrating the upper printed circuit board 11 is drilled on the multilayer printed circuit board 1 using a mechanical drill, and the signal hole 3 is connected to the trace layer 12. The signal hole 3 mainly plays the role of transmitting signals in the multilayer printed circuit board 1, so it needs to be connected to the trace layer 12 in the multilayer printed circuit board 1. When the thickness of the multilayer printed circuit board 1 is relatively thick, the laser burning technology cannot penetrate the multilayer printed circuit board 1. Therefore, it is necessary to first penetrate the multilayer printed circuit board 1 by mechanical drilling, and then use the laser burning technology to remove the medium between the signal hole 3 and the trace layer 12. At the same time, since the copper on the trace layer 12 can block the laser, the via can be accurately stopped at the trace layer 12 to achieve zero tail post.

[0046] In one possible implementation, S400 specifically includes the following steps: drilling a hole between the signal hole 3 and the return hole 2 using a conventional mechanical drill to form a connecting groove 5. In the above steps, in order to facilitate the flow of electrolyte between the signal hole 3 and the return hole 2, it is necessary to connect the signal hole 3 and the return hole 2. The method adopted in this application is to use a mechanical drill to drill a hole and connect the signal hole 3 and the return hole 2 using a gourd-shaped hole method to further form a connecting groove 5, which facilitates the flow of electrolyte.

[0047] In one possible implementation, refer to Figure 5 The S600 specifically includes the following steps: Electroplating the signal via 3 and the return via 2 with an electrolyte to form a conductive layer 4, which provides electrical connection between the trace layer 12, the upper printed circuit board 11, and the lower printed circuit board 13. Simultaneously, the signal via 3 and the return via 2 are electrically connected through the conductive layer 4. Specifically, this can be achieved as follows: Figure 5 As shown, the direction of electrolyte flow is indicated by arrow A in the figure, that is, from the lower printed circuit board 13 to the upper printed circuit board 11. During the electroplating process described above, the metal in the electrolyte adheres to the sidewall of the return hole 2-connection groove 5-signal hole 3, forming a conductive layer 4. The conductive layer 4 located inside the inner sidewall of the return hole 2-connection groove 5-signal hole 3 is used to electrically connect the upper printed circuit board 11 and the lower printed circuit board 13, facilitating signal transmission. It is worth noting that since the electroplated conductive layer 4 has a certain thickness, the conductive layer 4 will partially protrude from the upper surface of the upper printed circuit board 11. However, in actual operation, the protruding thickness does not affect the actual use.

[0048] In one possible implementation, S700 specifically includes the following steps: using a mechanical drill, drilling through the conductive layer 4 of the area covered by the orthographic projection of the connection groove 5 onto the multilayer printed circuit board 1. This step involves manually cutting off the conductive layer 4 on the sidewall of the connection groove 5 and filling it with a filling medium 6, further cutting off the electrical connection between the return hole 2 and the signal hole 3 to avoid short circuits during use. It should be noted that the filling medium 6 in this application is only used to fill the connection groove 5, and whether or how the signal hole 3 and the return hole 2 are filled during use depends on the actual needs of the next step. This application does not make specific limitations in this regard.

[0049] In one possible implementation, refer to Figure 3 , Figure 4This includes ensuring that the opening arc C of both the signal hole 3 and the return hole 2 meets the following range: 180° < C < 360°. In the above steps, due to the different sizes of the mechanical drills used, the opening arc C of the signal hole 3 and the return hole 2 will be different. However, the opening arc C must be greater than 180° to facilitate better electrical connection between the signal hole 3 and the wiring layer 12, and to facilitate high-speed signal transmission.

[0050] In one possible implementation, S800 specifically includes the following steps: using a mechanical drill to remove the burrs on the sidewall of the connection groove 5 to make the sidewall of the connection groove 5 regular. In the above steps, before closing the connection groove 5, the burrs on the sidewall of the connection groove 5 need to be removed, so that the solid medium filling medium 6 can seal the connection groove 5, and facilitate further wiring processing on the surface of the multilayer printed circuit board 1.

[0051] In one possible implementation, the filling medium 6 includes resin, and the use of an insulating filling medium 6 can prevent short circuits in the conductive layer 4.

[0052] To make the solutions provided in the embodiments of the present invention easier to understand, the method for fabricating blind vias on high-speed printed circuit boards provided in the embodiments of the present invention will be described in detail below through a specific embodiment, such as... Figure 2 As shown, the process includes the following steps:

[0053] S001: Provide an upper printed circuit board, a wiring layer and a lower printed circuit board, and press the upper printed circuit board, wiring layer and lower printed circuit board together to form a multilayer printed circuit board, and execute S002.

[0054] S002: Use a mechanical drill to form a return hole through the multilayer printed circuit board, and then execute S003;

[0055] S003: A signal hole is drilled through the upper printed circuit board using a mechanical drill in a multilayer printed circuit board. The signal hole is connected to the trace layer through the upper printed circuit board. S004 is executed.

[0056] S004: Use a conventional mechanical drill to drill holes between signal holes and return holes on a multilayer printed circuit board to form a connection groove, and perform S005.

[0057] S005: Inside the signal hole, the inner wall of the signal hole and the dielectric between it and the trace layer are removed by laser ablation technology to accurately form the signal hole on the surface of the trace layer, and then S006 is executed.

[0058] S006: Electrolyte is introduced through the end of the reflux hole near the lower printed circuit board to electroplate the signal hole and reflux hole as a whole to form a conductive layer, and then S007 is executed.

[0059] S007: Use a mechanical drill to drill through the conductive layer of the connection slot in the area covered by the orthographic projection of the multilayer printed circuit board, and then perform S008.

[0060] S008: Use a mechanical drill to remove the burrs from the sidewalls of the connecting groove to make the sidewalls of the connecting groove regular, and use a filling medium to fill the connecting groove between the signal hole and the return hole, then proceed to S009.

[0061] S009: Proceed to the next step on the upper printed circuit board.

[0062] In one possible implementation, refer to Figure 5 , Figure 6 Secondly, the present invention also provides a printed circuit board applied to the high-speed blind via fabrication method as described in any of the above claims, comprising: a multilayer printed circuit board 1, a return via 2, a signal via 3, and a filling medium 6;

[0063] The multilayer printed circuit board 1 includes an upper printed circuit board 11, a wiring layer 12, and a lower printed circuit board 13. The upper printed circuit board 11 and the lower printed circuit board 13 are respectively located on opposite sides of the wiring layer 12. A return via 2 sequentially passes through the upper printed circuit board 11, the wiring layer 12, and the lower printed circuit board 13. A signal via 3 passes through the upper printed circuit board 11 and communicates with the wiring layer 12. A connecting groove 5 is provided between the return via 2 and the signal via 3, and a filling medium 6 is disposed inside the connecting groove 5. (See reference for details.) Figure 5 , Figure 6 In this figure, the signal hole 3 produced by the above method is shown in the figure. The signal hole 3 produced by this method can realize the zero tail post of the signal hole 3 to the greatest extent, so that the signal can be transmitted at high speed to the greatest extent.

[0064] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method of making a high speed printed circuit board blind via, comprising: The method comprises the following steps: S100: providing an upper layer printed circuit board, a wiring layer and a lower layer printed circuit board, and integrally pressing the upper layer printed circuit board, the wiring layer and the lower layer printed circuit board to form a multi-layer printed circuit board; S200: forming a reflow hole penetrating through the multi-layer printed circuit board on the multi-layer printed circuit board; S300: forming a signal hole to the wiring layer on the multi-layer printed circuit board; S400: forming a connecting groove on the multi-layer printed circuit board for connecting the signal hole and the reflow hole; S500: removing the medium between the inner side wall of the signal hole and the wiring layer to form the signal hole on the surface of the wiring layer; S600: realizing the electrical connection of the upper layer printed circuit board and the lower layer printed circuit board by electroplating, while the signal hole and the reflow hole are electrically connected; specifically comprising the following steps: integrally electroplating the signal hole and the reflow hole by electrolyte to form a conductive layer for electrically connecting the wiring layer and the upper layer printed circuit board and the lower layer printed circuit board, while the signal hole and the reflow hole are electrically connected through the conductive layer; S700: cutting off the electrical connection between the signal hole and the reflow hole; S800: filling the connecting groove between the signal hole and the reflow hole with a filling medium.

2. The method of claim 1, wherein The S200 specifically comprises the following steps: using a mechanical drill to drill the reflow hole penetrating through the multi-layer printed circuit board on the multi-layer printed circuit board.

3. The method of claim 1, wherein the high speed printed circuit board blind via manufacturing method is characterized by, The S300 specifically comprises the following steps: using a mechanical drill to drill the signal hole penetrating through the upper layer printed circuit board on the multi-layer printed circuit board, and the signal hole is connected with the wiring layer.

4. The method of claim 1, wherein the high speed printed circuit board blind via manufacturing method is characterized by, The S400 specifically comprises the following steps: using a conventional mechanical drill to punch a hole between the signal hole and the reflow hole to form the connecting groove.

5. The method of claim 4, wherein the step of forming the blind via comprises the steps of: forming a first via in the first dielectric layer; and forming a second via in the second dielectric layer, the second via being aligned with the first via. The S700 specifically comprises the following steps: using a mechanical drill to drill the connecting groove in the conductive layer covered by the orthographic projection of the multi-layer printed circuit board.

6. The method of claim 1, wherein The method comprises the following steps: The opening arc C of the signal hole and the reflow hole satisfies the following range: 180° 7. The method of claim 1, wherein the high speed printed circuit board blind via manufacturing method is characterized by, The S800 specifically comprises the following steps: using a mechanical drill to remove burrs of the connecting groove side wall to make the connecting groove side wall regular.

8. The method of claim 1, wherein the high speed printed circuit board blind via manufacturing method is characterized by, The filling medium comprises resin.

9. A printed circuit board to be used in the method for manufacturing blind holes of a high-speed printed circuit board according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: The multi-layer printed circuit board, the reflow hole, the signal hole and the filling medium; The multi-layer printed circuit board comprises an upper layer printed circuit board, a wiring layer and a lower layer printed circuit board, wherein the upper layer printed circuit board and the lower layer printed circuit board are respectively arranged on the two sides of the wiring layer away from each other, the reflow hole penetrates through the upper layer printed circuit board, the wiring layer and the lower layer printed circuit board in sequence, the signal hole penetrates through the upper layer printed circuit board and communicates with the wiring layer, the connecting groove is arranged between the reflow hole and the signal hole, and the filling medium is arranged in the interior of the connecting groove.

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