Back-drilling method and circuit board

Abstract

The application discloses a back drilling method and a circuit board. The back drilling method comprises the following steps: providing a drilling device, wherein the drilling device comprises a first drill bit and a second drill bit, and the first drill bit and the second drill bit are different in size; providing a multilayer board, wherein the multilayer board is provided with a target layer; drilling a through hole in the multilayer board by using the first drill bit; performing first back drilling on the through hole from one side of the through hole by using the second drill bit, the second drill bit does not contact the target layer, and a first back drilling hole is obtained; performing second back drilling on the first back drilling hole from the one side of the through hole by using the second drill bit, the position of the second back drilling is different from that of the first back drilling, the second drill bit contacts the target layer, and a second back drilling hole is obtained. The position of the second back drilling is different from that of the first back drilling, so that the second back drilling removes one side of the target layer, and the other side of the target layer is reserved for wiring, and the signal reflection problem caused by the existence of a conductive residual pile in the circuit board processing process is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of circuit board technology, and in particular to a back-drilling method and a circuit board. Background Technology

[0002] In the manufacturing process of printed circuit boards, drilling is undoubtedly one of the key processes. For high-frequency and high-speed printed circuit boards, back drilling is extremely important. If the precision and specifications of the back drilling process are not well controlled, excess stubs will be generated. When the signal is transmitted to this point, it will return and cause resonance to reduce the signal. At the same time, it will cause reflection, scattering, and delay of signal transmission, which will bring difficulties to the control of signal integrity.

[0003] Current back-drilling technology can only minimize stub length. Creating zero-stub back-drilled holes from the drilling angle results in extremely poor yield and a high risk of drilling through the stub. Terminal transmission rates are also consistently limited by this; higher-frequency products must employ alternative solutions, such as high-density interconnect manufacturing methods. Therefore, a processing method that can improve the signal integrity problems caused by back-drilled stubs is particularly worthy of research and development. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a back-drilling method in which the second back-drilling is performed at a different position than the first back-drilling, so that the second back-drilling removes one side of the target layer, leaving the other side of the target layer for routing, effectively improving the signal reflection problem caused by the presence of conductive residual stakes during the circuit board manufacturing process.

[0005] This invention also proposes a circuit board.

[0006] According to a first aspect of the present invention, a back-drilling method includes the following steps: S1: providing a drilling device, the drilling device including a first drill bit and a second drill bit, the first drill bit and the second drill bit having different sizes; S2: providing a multilayer board, the multilayer board having a target layer disposed therein; S3: drilling a through hole in the multilayer board using the first drill bit; S4: performing a first back-drilling on the through hole from one side using the second drill bit, the second drill bit not contacting the target layer, to obtain the first back-drilled hole; S5: performing a second back-drilling on the first back-drilled hole from one side using the second drill bit, the second back-drilling being at a different position than the first back-drilling, and the second drill bit contacting the target layer, to obtain the second back-drilled hole.

[0007] According to the back drilling method for circuit boards of the present invention, the position of the second back drilling is different from that of the first back drilling, so that the second back drilling removes one side of the target layer, leaving the other side of the target layer for routing, which effectively improves the signal reflection problem caused by the presence of conductive residual stakes during the circuit board processing.

[0008] According to some embodiments of the present invention, before step S4, the method further includes: electroplating copper on the wall of the through hole to form a first metal layer on the wall of the through hole.

[0009] According to some embodiments of the present invention, in step S4, a conductive residual stake is connected to the target layer, the height of the conductive residual stake is L, the depth of the first back drilling is H1, the depth of the second back drilling is H2, and L, H1 and H2 satisfy the relationship: L≤H2-H1≤2L.

[0010] According to some embodiments of the present invention, the target layer is a copper layer.

[0011] According to some embodiments of the present invention, the target layer includes a routing area and a soldering area, wherein when the second drill bit is used to perform a second back-drilling on the first back-drilled hole from one side of the through hole, the second drill bit contacts the soldering area but does not contact the routing area.

[0012] According to some embodiments of the present invention, after step S5, the method further includes: S6: filling the second back drill hole with resin.

[0013] According to some embodiments of the present invention, after step S6, the method further includes: S7: performing copper plating on the multilayer board to form a second metal layer on one side of the multilayer board.

[0014] According to some embodiments of the present invention, after step S7, the method further includes: forming an outer layer pattern on the second metal layer.

[0015] The circuit board according to a second aspect of the present invention is manufactured according to the back-drilling method described above.

[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0018] Figure 1 This is a flowchart of a back-drilling method according to an embodiment of the present invention;

[0019] Figure 2This is a schematic diagram of the structure of a multilayer board according to an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of drilling through holes in a multilayer board according to an embodiment of the present invention;

[0021] Figure 4 This is a schematic diagram of copper plating in through-holes according to an embodiment of the present invention;

[0022] Figure 5 This is a schematic diagram of the first back drilling of a through hole according to an embodiment of the present invention;

[0023] Figure 6 This is a schematic diagram of the second back drilling of the through hole according to an embodiment of the present invention;

[0024] Figure 7 This is a schematic diagram of filling the second back-drilled hole with resin according to an embodiment of the present invention;

[0025] Figure 8 This is a schematic diagram of copper covering a multilayer board according to an embodiment of the present invention.

[0026] Figure label:

[0027] 10. Multilayer board; 11. Target layer; 12. Through hole; 13. First back drill hole; 14. Second back drill hole; 15. First metal layer; 16. Conductive residual stake; 17. Second metal layer. Detailed Implementation

[0028] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. The embodiments of the present invention are described in detail below.

[0029] The following is for reference. Figures 1-8 The back-drilling method according to an embodiment of the present invention is described, and a circuit board manufactured according to the back-drilling method described above is also proposed.

[0030] according to Figure 1 As shown, the back-drilling method includes the following steps:

[0031] S1: Provide drilling equipment, which includes a first drill bit and a second drill bit, the first drill bit and the second drill bit being of different sizes.

[0032] The first drill bit is used to drill through hole 12, and the second drill bit is used for back drilling. Therefore, the size of the second drill bit is larger than the size of the first drill bit.

[0033] S2: Provide a multilayer board 10, in which a target layer 11 is provided.

[0034] like Figure 2As shown, the multilayer board 10 can be laid out in layers, allowing signal traces of different functional modules to be placed on different layers. This improves circuit performance and reduces signal interference. Through lamination, signal lines, power lines, and ground lines can be laid between different layers, forming a good signal loop and improving the rigidity and durability of the circuit board.

[0035] The multilayer board 10 includes a first segment and a second segment. The first segment includes at least two layers, and the second segment includes at least two layers. The first segment and the second segment are arranged along the stacking direction of the multilayer board 10. A target layer 11 is disposed between the first segment and the second segment. The target layer 11 is sandwiched between the first segment and the second segment.

[0036] S3: Use the first drill bit to drill through holes 12 in the multilayer board 10.

[0037] like Figure 3 As shown, the first drill bit passes through the first section, the target layer 11 and the second section to drill a through hole 12 in the multilayer board 10. The through hole 12 penetrates the multilayer board 10 along the stacking direction of the multilayer board 10.

[0038] S4: Use a second drill bit to perform a first back-drill from one side of the through hole 12. The second drill bit does not contact the target layer 11 to obtain the first back-drilled hole 13.

[0039] like Figure 5 As shown, the second drill bit performs back drilling on the multilayer board 10, that is, the second drill bit passes through the second section from one side of the through hole 12 until it is close to the target layer 11, and the second drill bit does not contact the target layer 11. The second drill bit removes the second section as much as possible so that the conductive residual pile 16 between the target layer 11 and the second section is as short as possible.

[0040] S5: A second drill bit is used to perform a second back-drilling on the first back-drilled hole 13 from one side of the through hole 12. The position of the second back-drilling is different from that of the first back-drilling, and the second drill bit contacts the target layer 11 to obtain the second back-drilled hole 14.

[0041] according to Figure 6 As shown, the second drill bit performs a second back-drilling on the first back-drilled hole 13, based on the first back-drilling. By moving the second drill bit, the position of the second back-drilling is offset from that of the first back-drilling, and the depth of the second back-drilling is greater than that of the first back-drilling. This allows the second drill bit to contact the target layer 11, and the second drill bit removes part of the target layer 11, forming a stepped conductive stud 16 between the second section and the target layer 11. This effectively removes the conductive stud 16 on the side of the target layer 11 used for welding, while retaining the other side of the target layer 11 for routing. This effectively reduces the signal loss of the conductive stud 16 to the via, thus enabling the product to meet the requirements of high-frequency and high-speed products.

[0042] Pads are provided on the target layer 11. The second drill bit is offset towards one side of the target layer 11 to remove a portion of the target layer 11 on that side, while the other side of the target layer 11 remains intact and is used for traces. This reduces interference signals from conductive studs 16 within the vias, effectively improving signal reflection problems caused by the presence of conductive studs 16 during circuit board manufacturing and enhancing the processing capabilities of high-speed and high-frequency products.

[0043] like Figure 4 As shown, before step S4, the method further includes: electroplating copper on the wall of the through hole 12 to form a first metal layer 15 on the wall of the through hole 12. Specifically, after drilling the through hole 12 and before the first back drilling, copper needs to be electroplated on the wall of the through hole 12. The first metal layer 15 can be a copper layer to ensure the reliability of the interconnection of the inner layer circuits, meet the interlayer interconnection requirements of the circuit board, and greatly increase the flexibility of the interlayer interconnection density.

[0044] According to some embodiments of the present invention, in step S4, the target layer 11 is connected to a conductive residual stake 16, the height of the conductive residual stake 16 is L, the depth of the first back drilling is H1, and the depth of the second back drilling is H2. L, H1, and H2 satisfy the relationship: L≤H2-H1≤2L. Specifically, after the first back drilling, during the process of the second drill bit removing the second section, it is impossible to completely remove all residues. Therefore, the second section still has a conductive residual stake 16 remaining, which is the residual part of the first metal layer 15 in the second section area. The difference between the depth of the second back drilling and the depth of the first back drilling is less than twice the height of the conductive residual stake 16 but greater than one times the height of the conductive residual stake 16. That is, in addition to removing the conductive residual stake 16 on one side of the target layer 11, the second back drilling will also remove part of the target layer 11. The other side of the target layer 11 is used for wiring, so the unremoved conductive residual stake 16 has little impact on signal transmission. Therefore, reducing the interference signal effect of conductive residual 16 in the via can effectively improve the signal reflection problem caused by the presence of conductive residual 16 in the circuit board processing, and improve the processing capability of high-speed and high-frequency products.

[0045] In some embodiments, the target layer 11 is a copper layer. That is, the target layer 11 is a conductive layer, and the target layer 11 is connected to the first metal layer 15 in the via 12, so that the first segment in the via 12 can be electrically connected to the target layer 11.

[0046] In some embodiments, the target layer 11 includes a routing area and a soldering area. When the second drill bit performs a second back-drilling on the first back-drilled hole 13 from one side of the through hole 12, the second drill bit contacts the soldering area but not the routing area. Specifically, the target layer 11 is divided into a routing area and a soldering area. When the second drill bit performs the second back-drilling, the second drill bit moves toward the soldering area so that the position of the second back-drilling is offset from the position of the first back-drilling. The second drill bit removes the conductive residual stake 16 corresponding to the soldering area. The interference of the conductive residual stake 16 corresponding to the routing area on signal transmission is negligible, thereby effectively improving the signal reflection problem caused by the presence of conductive residual stake 16 in the circuit board processing process and improving the processing capability of high-speed and high-frequency products.

[0047] like Figure 7 As shown, after step S5, the process further includes: S6: Filling the second back-drilled hole 14 with resin. That is, after the second back drilling, resin is filled into the second back-drilled hole 14. Using resin to plug the holes reduces the distance between them, solving the problem of wires and wiring. After baking, the resin cures, and its surface is flush with the surface of the multilayer board 10, facilitating subsequent copper plating.

[0048] like Figure 8 As shown, after step S6, the process further includes: S7: applying copper plating to the multilayer board 10 to form a second metal layer 17 on one side of the multilayer board 10. Specifically, after filling the second back-drilled hole 14 with resin and baking to cure it, copper plating is performed on the non-back-drilled side of the multilayer board 10 to form a second metal layer 17 on one side of the multilayer board 10.

[0049] Furthermore, after step S7, the method further includes: fabricating an outer layer pattern on the second metal layer 17. The outer layer pattern is fabricated on the surface of the multilayer board 10 for subsequent soldering.

[0050] According to a second aspect embodiment of the present invention, a circuit board is manufactured using the back-drilling method described above. Two back-drilling operations are employed to reduce the impact of conductive residual spikes 16 on signal transmission. The second back-drilling operation is performed at a different location than the first, so that one side of the target layer 11 is removed during the second back-drilling, while the other side of the target layer 11 is retained for routing, effectively improving the signal reflection problem caused by the presence of conductive residual spikes 16 during circuit board manufacturing.

[0051] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0052] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0053] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A back-drilling method, characterized in that, Includes the following steps: S1: Provide drilling equipment, the drilling equipment including: a first drill bit and a second drill bit, the first drill bit and the second drill bit having different sizes; S2: Provide a multilayer board (10), wherein a target layer (11) is provided in the multilayer board (10); S3: Use the first drill bit to drill through holes (12) in the multilayer board (10); S4: The second drill bit is used to perform a first back drill from one side of the through hole (12), and the second drill bit does not contact the target layer (11) to obtain the first back drill hole (13). S5: Using the second drill bit, the first back drill hole (13) is back drilled a second time from one side of the through hole (12). The position of the second back drill is different from that of the first back drill, and the drill bit contacts the target layer (11) to obtain the second back drill hole (14).

2. The back drilling method according to claim 1, characterized in that, Before step S3, the following is also included: Copper is electroplated on the wall of the through hole (12) to form a first metal layer (15) on the wall of the through hole (12).

3. The back drilling method according to claim 2, characterized in that, In step S3, the target layer (11) is connected to a conductive residual pile (16), the height of the conductive residual pile (16) is L, the depth of the first back drilling is H1, the depth of the second back drilling is H2, and L, H1 and H2 satisfy the relationship: L≤H2-H1≤2L.

4. The back drilling method according to claim 1, characterized in that, The target layer (11) is a copper layer.

5. The back-drilling method according to claim 1, characterized in that, The target layer (11) includes a wiring area and a welding area. When the second drill bit is used to perform a second back-drilling on the first back-drilled hole (13) from one side of the through hole (12), the second drill bit contacts the welding area but does not contact the wiring area.

6. The back drilling method according to claim 1, characterized in that, After step S4, the method further includes: S5: Fill the second back drill hole (14) with resin.

7. The back drilling method according to claim 2, characterized in that, After step S5, the method further includes: S6: Perform copper plating on the multilayer board (10) to form a second metal layer (17) on one side of the multilayer board (10).

8. The back-drilling method according to claim 7, characterized in that, After step S6, the following also includes: An outer layer pattern is created on the second metal layer (17).

9. A circuit board, characterized in that, It is manufactured by the back-drilling method according to any one of claims 1-8.

Images