A method for manufacturing a differential signal hole and a circuit board

Abstract

The application provides a differential signal hole manufacturing method and a circuit board. The differential signal hole manufacturing method comprises the following steps: obtaining a plurality of cured sheets and a plurality of pattern-processed core plates, machining a first slot and two second slots on the plurality of cured sheets and the core plates; laminating the core plates and the cured sheets in sequence to obtain a circuit substrate; machining a first blind slot at a target position of the first positioning slot and machining two second blind slots at target positions of the two second positioning slots; etching the first blind slot and the second blind slot; and then sequentially performing copper sinking, ink fading and washing, and resin filling in the first positioning slot, the second positioning slot, the first blind slot and the second blind slot, so that a differential signal hole is formed on the circuit substrate. The differential signal hole manufacturing method provided by the application can reduce the signal integrity problem occurring at the via hole, so that the circuit board can meet high-frequency and high-speed signal transmission.

Description

Technical Field

[0001] This invention belongs to the field of PCB technology, specifically relating to a method for manufacturing differential signal vias and a circuit board. Background Technology

[0002] With the development of 5G communication, the iteration of computing hardware in AI servers, and the increasing applications of millimeter-wave radar, printed circuit boards (PCBs) are moving towards high-speed, high-frequency signal transmission and high-density interconnection. In high-speed signal design, signals need to achieve layer switching through vias on the PCB. Existing via processing can be simplified as follows: drill holes of a certain size and depth on the PCB, and then chemically deposit copper to form a layer of copper on the inner wall of the hole, achieving electrical connection. Vias for transmitting differential signals are called differential vias, and typically consist of two vias.

[0003] In traditional via fabrication, interconnects at specific levels require the creation of through-holes followed by back-drilling. The residual spikes left by this back-drilling process cause signal reflections, ultimately increasing signal loss in the transmission line. Current technology reduces via spike reflections by fabricating deep microvias on the circuit board. Specifically, this involves creating mechanical blind vias, ablating them with a laser, and then electroplating them into deep microvias. However, this method is severely limited by the limitations of chemical exchange capabilities, hindering the development of deeper, high aspect ratio interconnects.

[0004] Therefore, there is an urgent need to develop a new method for processing differential signal holes that reduces interference signals from residual piles in the borehole, in order to solve the problems existing in the current technology and meet the needs of actual production. Summary of the Invention

[0005] This invention provides a method for manufacturing differential signal vias and a circuit board, which can reduce signal integrity problems at vias and meet the requirements of high-frequency and high-speed signal transmission.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: This invention provides a method for fabricating a differential signal aperture, comprising the following steps: Multiple cured sheets and multiple patterned core boards are obtained. A first slot and two second slots are processed on the multiple cured sheets and core boards. The two second slots are respectively arranged on both sides of the first slot. The first slot and / or the second slot of one of the core boards is a blind hole slot, and the remaining first slots and second slots are through hole slots. The core board and the cured sheet are stacked and laminated in sequence to obtain a circuit board. The first slot on the core board and the cured sheet are connected to form a first positioning groove, and the second slot on the core board and the cured sheet are connected to form a second positioning groove. Anti-plating ink is filled into the first positioning groove and the second positioning groove. A first blind groove is machined at the target position of the first positioning groove, and two second blind grooves are machined at the target positions of the two second positioning grooves. The first blind groove penetrates through the two second blind grooves. The depth of both the first blind groove and the second blind groove is less than the depth of the surface of the anti-plating ink. The first and second blind trenches are etched to retain the metal layer at the target location; then copper plating, ink removal, and resin filling are performed sequentially in the first positioning trench, the second positioning trench, the first blind trench, and the second blind trench to form differential signal holes on the circuit board.

[0007] Optionally, the first slot and the two second slots are arranged in parallel; And / or, two second blind slots are symmetrically arranged, each second blind slot passing through the first positioning slot and the two second positioning slots respectively, and extending in a direction away from the second positioning slots.

[0008] Optionally, the two second blind slots are arranged in an intersecting manner, with the first blind slot passing through the intersection of the two second blind slots, and the two second blind slots are arranged symmetrically about the axis of the first blind slot.

[0009] Optionally, the two second blind slots are arranged in parallel, and the center line connecting the first blind slot and the two second blind slots is arranged coaxially.

[0010] Optionally, the side edge of the first blind groove extends beyond the side edge of the first positioning groove and is located between the side edges of the two second positioning grooves away from the first positioning groove; the end edge of the first blind groove is located inside the first positioning groove. And / or, the first blind groove is coaxially arranged with the first positioning groove.

[0011] Optionally, before filling the first positioning groove, the second positioning groove, the first blind groove, and the second blind groove with resin, the circuit board may be electroplated.

[0012] Optionally, after filling the first positioning groove, the second positioning groove, the first blind groove, and the second blind groove with resin, the following step is further included: The circuit board is electroplated to form a second copper layer on its surface; Patterning is performed on the surface of the second copper layer to form a circuit pattern.

[0013] The present invention also provides a circuit board, including a circuit board substrate, wherein the circuit board substrate is provided with differential signal vias, two shielding layers, a first resin layer and two second resin layers, each of the shielding layers being disposed between the first resin layer and a second resin layer; each of the second resin layers having at least two differential signal vias on the side away from the shielding layer; the depth of the first resin layer being greater than the depth of the shielding layer and the differential signal vias.

[0014] Optionally, a first copper layer and a third resin layer are disposed inside the differential signal hole. The first copper layer is located at the bottom of the differential signal hole and is connected to the second resin layer. The third resin layer is located on the first copper layer and is integrally formed with the second resin layer. The shielding layer includes a second copper layer and a fourth resin layer. The second copper layer is located inside the circuit substrate and is connected to the first resin layer. The fourth resin layer is located on the second copper layer. The first resin layer, the second resin layer, the third resin layer, and the fourth resin layer are integrally formed.

[0015] The present invention also provides a circuit board, including a circuit board substrate, wherein a differential signal via is provided on the circuit board substrate, and the differential signal via is manufactured by the differential signal via manufacturing method described in any one of the above claims.

[0016] The method for fabricating differential signal vias provided by this invention involves laminating a cured wafer with first and second slots and a core board to form first and second positioning slots on a circuit board. The depths of the first and second blind slots are based on the depths of the first and second positioning slots, but are lower than the depth of the resist ink within the first and second positioning slots, resulting in a high aspect ratio for both. Simultaneously, the first and second blind slots are fabricated based on the first and second positioning slots to avoid the formation of via studs. Furthermore, after copper plating, ink stripping is performed to remove the copper layer formed on the first and second positioning slots, while retaining the copper layer on the first and second blind slots. This effectively separates the copper layer on the first blind slot by the first positioning slot, preventing mutual interference between the differential signal vias formed by the second blind slot. Therefore, the differential signal via structure fabricated by this method can reduce signal integrity issues at via locations, enabling the circuit board to meet the requirements of high-frequency and high-speed products. Attached Figure Description

[0017] Figure 1 This is a top view of the circuit board structure in step three of the method for fabricating a differential signal hole according to an embodiment of the present invention. Figure 2 This is a top view of the circuit board structure in step four of the method for fabricating a differential signal hole according to an embodiment of the present invention. Figure 3 This is a top view of the circuit board structure in step five of the method for fabricating a differential signal hole according to an embodiment of the present invention. Figure 4 This is a top view of the circuit board structure in step six of the method for fabricating a differential signal hole according to an embodiment of the present invention. Figure 5 yes Figure 4 Schematic diagram of the cross-sectional structure along the AA direction; Figure 6 This is a top view of the circuit board structure in step three of the method for fabricating a differential signal hole according to another embodiment of the present invention. Figure 7 This is a schematic diagram of the circuit board structure provided in an embodiment of the present invention.

[0018] The reference numerals in the accompanying drawings are as follows: 1. Circuit board; 11. Differential signal via; 12. Shielding layer; 21. First positioning groove; 22. Second positioning groove; 3. Anti-plating ink; 41. First blind groove; 42. Second blind groove; 5. First copper cladding layer; 51. First copper layer; 52. Second copper layer; 6. Resin; 61. First resin layer; 62. Second resin layer; 63. Third resin layer; 64. Fourth resin layer. Detailed Implementation

[0019] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0020] In the description of this invention, it should be understood that the terms "front," "rear," "vertical," "horizontal," "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship of the object being processed. They are used only for the convenience of describing this invention and for simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0021] See Figures 1-6 As shown, an embodiment of the present invention provides a method for fabricating a differential signal aperture, comprising the following steps: S1. Obtain multiple cured sheets and a patterned core board. Process a first slot and two second slots on the multiple cured sheets and the core board. The two second slots are respectively located on both sides of the first slot. One core board has a first slot and / or a second slot that is a blind hole slot, while the remaining first slots and second slots are through-hole slots. Specifically, one core board has a first slot that is a blind hole slot and a second slot that is a through-hole slot, while another core board has a first slot that is a through-hole slot and a second slot that is a blind hole slot. Alternatively, both the first slot and the second slot on one core board can be blind hole slots. The widths of the first slot and the second slot can be the same or different. The cured sheets are formed of resin.

[0022] S2, the core board and the cured sheet are sequentially stacked and laminated to obtain the circuit board 1. The first slots on the core board and the cured sheet are connected to form a first positioning groove 21, and the second slots on the core board and the cured sheet are connected to form a second positioning groove 22. The first positioning groove 21 and the second positioning groove 22 are filled with anti-plating ink 3. Specifically, during lamination, the first slots are arranged correspondingly to each other, and the second slots are arranged correspondingly to each other. The length and depth of the first positioning groove 21 and the second positioning groove 22 can be the same or different, and the depth of filling with anti-plating ink 3 can also be the same or different.

[0023] S3, a first blind trench 41 is machined at the target position of the first positioning groove 21, and two second blind trenches 42 are machined at the target positions of the two second positioning grooves 22. Specifically, the bottoms of the first blind trench 41 and the two second blind trenches 42 are located in the cured sheet layer. The first blind trench 41 penetrates the two second blind trenches 42, increasing the chemical exchange capacity between the first blind trench 41, the second blind trench 42, the first positioning groove 21, and the second positioning groove 22, so that copper plating can be completed and the reliability of interconnection can be guaranteed. Specifically, the depths of the first blind trench 41 and the second blind trench 42 can be the same or different.

[0024] The depths of the first blind groove 41 and the second blind groove 42 are both less than the depth of the surface of the anti-plating ink 3, so as to prevent the anti-plating ink 3 from flowing into the first blind groove 41 and the second blind groove 42 and causing ink loss; S4, etch the first blind trench 41 and the second blind trench 42 to burn off the solidified layer, exposing the copper surface at the bottom of the first blind trench 41 and the second blind trench 42, while retaining the metal layer at the target position; then, perform copper plating in the first positioning trench 21, the second positioning trench 22, the first blind trench 41 and the second blind trench 42, forming a first copper plating layer 5 in the first positioning trench 21, the second positioning trench 22, the first blind trench 41 and the second blind trench 42; S5, the circuit board 1 is stripped of ink to remove the first copper plating layer 5 on the first positioning groove 21 and the second positioning groove 22. The first copper plating layer 5 on the first blind groove 41 and the second blind groove 42 is retained because no anti-plating ink 3 is applied. At the same time, the first blind groove 41 is divided into two by the first positioning groove 21 due to the removal of the first copper plating layer 5 on the first positioning groove 21, and the second blind groove 42 is formed by the removal of the first copper plating layer 5 on the second positioning groove 22, thus forming independent differential signal holes 11. The structure formed by the first blind groove 41 provides a shielding effect for the two pairs of differential signal holes 11 and avoids mutual interference between the differential signal holes 11.

[0025] S6, the first positioning groove 21, the second positioning groove 22, the first blind groove 41 and the second blind groove 42 are filled with resin 6, and a differential signal hole 11 is formed on the circuit board 1.

[0026] In this embodiment, by laminating a cured sheet and a core board with first and second slots, a first positioning slot 21 and a second positioning slot 22 are formed on the circuit board 1. The depths of the first blind slot 41 and the second blind slot 42 are based on the depths of the first positioning slot 21 and the second positioning slot 22, and are lower than the depth of the anti-plating ink 3 within the first positioning slot 21 and the second positioning slot 22, resulting in a high aspect ratio for the first positioning slot 21 and the second positioning slot 22. Simultaneously, the first blind slot 41 and the second blind slot 42 are processed based on the first positioning slot 21 and the second positioning slot 22 to avoid the formation of via residual pins. Furthermore, after forming the first copper plating layer 5, ink stripping is performed to remove the first copper plating layer 5 from the first positioning slot 21 and the second positioning slot 22, while retaining the first copper plating layer 5 on the first blind slot 41 and the second blind slot 42. This separates the first copper plating layer 5 on the first blind slot 41 into two parts by the first positioning slot 21, preventing mutual interference between the differential signal vias 11 formed by the second blind slot 42. Therefore, the differential signal via 11 structure produced by this method can reduce signal integrity problems at the via, enabling the circuit board to meet the requirements of high-frequency and high-speed products.

[0027] like Figure 1 As shown, in one embodiment of the present invention, the first slot and the two second slots are arranged in parallel; Two second blind slots 42 are symmetrically arranged. Each second blind slot 42 passes through the first positioning slot 21 and the two second positioning slots 22 respectively, and extends in a direction away from the second positioning slots 22, so as to be separated into independent signal holes by the second positioning slots 22.

[0028] like Figure 1In one embodiment of the present invention, two second blind trenches 42 are arranged intersectingly, and a first blind trench 41 passes through the intersection of the two second blind trenches 42, with the two second blind trenches 42 arranged symmetrically about the axis of the first blind trench 41. The intersecting arrangement of the two second blind trenches 42 and the first blind trench 41 passing through the intersection of the two second blind trenches 42 increase the chemical exchange capacity, enabling copper plating to be completed and ensuring the reliability of the interconnection.

[0029] like Figure 6 In one embodiment of the present invention, the two second blind slots 42 are arranged in parallel, and the center line connecting the first blind slot 41 and the two second blind slots 42 is coaxially arranged, so that the differential signal apertures 11 formed by the second blind slots 42 are symmetrical to each other, so as to ensure signal integrity and reduce electromagnetic interference.

[0030] like Figure 1 As shown, in one embodiment of the present invention, the end of each second blind slot 42 is equidistant from the edge of the adjacent second positioning slot 22, such that the differential signal holes 11 formed by the second blind slots 42 are symmetrical to each other, so as to ensure signal integrity and reduce electromagnetic interference.

[0031] like Figure 1 As shown, in one embodiment of the present invention, the first blind groove 41 and the first positioning groove 21 are arranged coaxially so that the first blind groove 41 is evenly divided into two by the first positioning groove 21, thereby avoiding mutual interference between the differential signal holes 11 formed by the second blind groove 42.

[0032] like Figure 1 As shown, in one embodiment of the present invention, the side edge of the first blind groove 41 extends out of the side edge of the first positioning groove 21 and is located between the side edges of the two second positioning grooves 22 away from the first positioning groove 21, so as to form a shielding layer 12 between the differential signal holes 11; the end edge of the first blind groove 41 is located inside the first positioning groove 21 to prevent the ends of the first blind groove 41 from being electrically connected to each other through the first copper layer after subsequent ink rinsing.

[0033] In one embodiment of the present invention, before filling the first positioning groove 21, the second positioning groove 22, the first blind groove 41 and the second blind groove 42 with resin 6, the circuit board 1 is further electroplated to increase the thickness of the first copper layer 5 in the first blind groove 41 and the second blind groove 42 to meet the current flow requirements.

[0034] like Figure 7 As shown, in one embodiment of the present invention, after filling the first positioning groove 21, the second positioning groove 22, the first blind groove 41 and the second blind groove 42 with resin 6, the following steps are further included: S7, Electroplating is performed on the circuit substrate 1, and a second copper plating layer is formed on the surface of the circuit substrate 1; S8, perform pattern processing on the surface of the second copper-clad layer to form a circuit pattern.

[0035] Furthermore, in the subsequent circuit board processing, the circuit board 1 with the circuit pattern is subjected to solder masking and character processing to obtain the finished circuit board.

[0036] like Figure 5 As shown, an embodiment of the present invention also provides a circuit board, including a circuit board 1. The circuit board 1 has differential signal vias 11, two shielding layers 12, a first resin layer 61, and two second resin layers 62 disposed therein. Each shielding layer 12 is disposed between the first resin layer 61 and one second resin layer 62. At least two differential signal vias 11 are disposed on the side of each second resin layer 62 away from the shielding layer 12. By disposing of shielding layers 12 between the differential signal vias 11, mutual interference between the differential signal vias 11 is avoided. Specifically, the two shielding layers 12 are arranged symmetrically about the axis of the first resin layer 61, and the differential signal vias 11 are arranged symmetrically about the axis of the first resin layer 61. By disposing of the second resin layers 62, the differential signal vias 11 are isolated from the shielding layers 12, making the differential signal vias 11 independent.

[0037] In one embodiment of the present invention, the depth of the first resin layer 61 is greater than the depth of the shielding layer 12 and the differential signal hole 11.

[0038] In one embodiment of the present invention, a first copper layer 51 and a third resin layer 63 are disposed inside the differential signal hole 11. The first copper layer 51 is located at the bottom of the differential signal hole 11 and is connected to the second resin layer 62. The third resin layer 63 is located on the first copper layer 51 and is integrally formed with the second resin layer 62. The shielding layer 12 includes a second copper layer 52 and a fourth resin layer 64. The second copper layer 52 is located inside the circuit board 1 and is connected to the first resin layer 61. The fourth resin layer 64 is located on the second copper layer 52. The first resin layer 61, the second resin layer 62, the third resin layer 63 and the fourth resin layer 64 are integrally formed.

[0039] An embodiment of the present invention also provides a circuit board, including a circuit board 1, wherein a differential signal hole 11 is provided on the circuit board 1, and the differential signal hole 11 is manufactured by the method for manufacturing differential signal hole 11 described in any one of the above claims.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a differential signal aperture, characterized in that, Includes the following steps: Multiple cured sheets and multiple patterned core boards are obtained. A first slot and two second slots are processed on the multiple cured sheets and core boards. The two second slots are respectively arranged on both sides of the first slot. The first slot and / or the second slot of one of the core boards is a blind hole slot, and the remaining first slots and second slots are through hole slots. The core board and the cured sheet are stacked and laminated in sequence to obtain a circuit board. The first slot on the core board and the cured sheet are connected to form a first positioning groove, and the second slot on the core board and the cured sheet are connected to form a second positioning groove. Anti-plating ink is filled into the first positioning groove and the second positioning groove. A first blind groove is machined at the target position of the first positioning groove, and two second blind grooves are machined at the target positions of the two second positioning grooves. The first blind groove penetrates the two second blind grooves. The depth of both the first blind groove and the second blind groove is less than the depth of the surface of the anti-plating ink. The side edge of the first blind groove extends beyond the side edge of the first positioning groove and is located between the side edges of the two second positioning grooves away from the first positioning groove. The end edge of the first blind groove is located inside the first positioning groove. The two second blind grooves are symmetrically arranged, and each second blind groove penetrates the first positioning groove and the two second positioning grooves respectively, and extends in a direction away from the second positioning groove. The first and second blind trenches are etched to ablate the solidified layer, exposing the copper surface at the bottom of the first and second blind trenches while retaining the metal layer at the target location. Then, copper plating is performed sequentially in the first positioning trench, the second positioning trench, the first blind trench, and the second blind trench, forming a first copper plating layer. The circuit board is then stripped of ink to remove the first copper plating layer on the first positioning trench and the second positioning trench. Resin is then filled into the first positioning trench, the second positioning trench, the first blind trench, and the second blind trench, forming differential signal holes on the circuit board.

2. The method for fabricating a differential signal aperture according to claim 1, characterized in that, The first slot and the two second slots are arranged in parallel.

3. The method for fabricating a differential signal aperture according to claim 2, characterized in that, The two second blind slots are arranged intersectingly, and the first blind slot passes through the intersection of the two second blind slots, and the two second blind slots are arranged symmetrically about the axis of the first blind slot.

4. The method for fabricating a differential signal aperture according to claim 2, characterized in that, The two second blind slots are arranged in parallel, and the center line connecting the first blind slot and the two second blind slots is arranged coaxially.

5. The method for fabricating a differential signal aperture according to claim 1, characterized in that, The first blind groove is coaxially aligned with the first positioning groove.

6. The method for fabricating a differential signal aperture according to claim 1, characterized in that, Before filling the first positioning groove, the second positioning groove, the first blind groove and the second blind groove with resin, the circuit board is electroplated.

7. The method for fabricating a differential signal aperture according to claim 1, characterized in that, After filling the first positioning groove, the second positioning groove, the first blind groove, and the second blind groove with resin, the following steps are also included: The circuit board is electroplated to form a second copper layer on its surface; Patterning is performed on the surface of the second copper layer to form a circuit pattern.

8. A circuit board, characterized in that, The circuit board includes a differential signal via, two shielding layers, a first resin layer, and two second resin layers. Each shielding layer is disposed between the first resin layer and a second resin layer. Each second resin layer has at least two differential signal vias on its side away from the shielding layer. The depth of the first resin layer is greater than the depth of the shielding layer and the differential signal vias. The differential signal aperture is manufactured by the method for manufacturing a differential signal aperture according to any one of claims 1-7.

9. The circuit board according to claim 8, characterized in that, The differential signal hole is provided with a first copper layer and a third resin layer. The first copper layer is located at the bottom of the differential signal hole and is connected to the second resin layer. The third resin layer is located on the first copper layer and is integrally formed with the second resin layer. The shielding layer includes a second copper layer and a fourth resin layer. The second copper layer is located inside the circuit substrate and is connected to the first resin layer. The fourth resin layer is located on the second copper layer. The first resin layer, the second resin layer, the third resin layer, and the fourth resin layer are integrally formed.

10. A circuit board, characterized in that, The device includes a circuit board on which differential signal vias are provided, the differential signal vias being manufactured by the method for manufacturing differential signal vias according to any one of claims 1-7.

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