PCB back drilling method and PCB
By drilling a hole through the second plating layer from the second board side during PCB back drilling, and then drilling a hole of a preset depth with the second plating layer as the reference surface, the problem of inaccurate drilling depth control in traditional back drilling methods is solved, thereby improving PCB quality and signal transmission integrity.
Patent Information
- Application Number
- CN202210830568.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-07-15
- Publication Date
- 2025-12-12
- Estimated Expiration
- 2042-07-15
AI Technical Summary
Traditional back-drilling methods have difficulty precisely controlling the drilling depth when removing invalid sections on a PCB, resulting in drilling that is too deep or too shallow, which affects the quality of the PCB.
The method involves first drilling a second hole through the second plating layer on the substrate from the side of the second plate away from the target plate, then drilling a third hole from the side of the second plate away from the target plate, and finally drilling a fourth hole of a preset depth at the bottom of the third hole, using the surface of the second plating layer away from the first plate as the reference surface, to precisely remove the residual plating layer.
It improves PCB quality, ensures accurate removal of invalid segments, reduces drilling errors, and enhances the integrity of signal transmission.
Smart Images
Figure CN115209624B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of printed circuit board, and particularly relates to a PCB back drilling method and a PCB. BACKGROUND
[0002] In order to realize the electrical connection of each layer of circuit on the PCB, a metalized via is needed to be arranged on the PCB, and on part of the PCB, only the electrical signal transmission between part of the circuit layers can be realized through the metalized via, so that the excess metalized plating layer (i.e. invalid segment) in the metalized via needs to be removed to avoid the formation of parasitic capacitance and parasitic inductance by the invalid segment, which affects the integrity of high-speed signal transmission.
[0003] The traditional method for removing the invalid segment usually adopts a back drilling manner. During back drilling processing, the depth of the back drilling hole is not easy to control due to the influence of the drilling machine precision and the uniformity of the PCB thickness, and the PCB quality is affected by the broken signal layer caused by the over-deep drilling hole or the overlong residual invalid segment caused by the over-shallow drilling hole. SUMMARY
[0004] The present application provides a PCB back drilling method and a PCB to more accurately remove the residual invalid segment and improve the quality of the PCB.
[0005] Embodiments of the first aspect of the present application provide a PCB back drilling method, comprising:
[0006] A substrate is provided, the substrate comprising a target plate and first and second plates arranged on opposite sides of the target plate respectively, the substrate being provided with a first hole, the first hole penetrating through the substrate, the first hole comprising coaxial and communicating first and second sub-holes, the first sub-hole having a larger hole diameter than the second sub-hole, the first sub-hole penetrating through the first plate and the target plate, the first sub-hole hole wall, the first sub-hole hole bottom and the second sub-hole hole wall being respectively provided with first, second and third plating layers, the first plating layer electrically connecting the circuit of the first plate and the circuit of the target plate;
[0007] A second hole penetrating through the second plating layer is drilled on the substrate, the third plating layer and part of the second plating layer are removed, the second hole is coaxially arranged with the first hole, the second hole has a larger hole diameter than the second sub-hole, and the second hole has a smaller hole diameter than the first sub-hole;
[0008] A third hole is drilled on the substrate from the side of the second plate away from the target plate, the third hole extends to the surface of the remaining second plating layer away from the first plate, the third hole is coaxially arranged with the first hole, and the third hole has a larger hole diameter than the second hole;
[0009] With the surface of the remaining second plating layer away from the surface of the first plate as a first reference surface, a fourth hole of a first preset depth is drilled at the bottom of the third hole, the bottom of the fourth hole extends to the surface of the target plate away from the surface of the first plate.
[0010] In some embodiments, the fourth hole is coaxially arranged with the first hole, and the aperture of the fourth hole is greater than or equal to the aperture of the first sub-hole.
[0011] In some embodiments, before providing a substrate, the PCB back drilling method further comprises:
[0012] Drilling a through hole on the substrate, the through hole penetrating through the first plate, the target plate and the second plate;
[0013] Drilling the first sub-hole at the through hole of the substrate from the side of the first plate away from the target plate, the aperture of the first sub-hole being greater than the aperture of the through hole, and the remaining through hole being a second sub-hole;
[0014] Carrying out a metallization process on the first sub-hole and the second sub-hole, so that the first plating layer, the second plating layer and the third plating layer are respectively formed on the hole wall of the first sub-hole, the hole bottom of the first sub-hole and the hole wall of the second sub-hole.
[0015] In some embodiments, the first sub-hole includes a first processing hole and a second processing hole connected in communication, and the target plate includes a target copper layer, the first sub-hole is drilled on the substrate from the side of the first plate away from the target plate, and the first sub-hole penetrates through the first plate and the target plate, specifically comprising:
[0016] Drilling the first processing hole on the substrate from the side of the first plate away from the target plate, the first processing hole penetrating through the first plate;
[0017] With the side of the target copper layer close to the first plate as a second reference surface, drilling the second processing hole of a second preset depth at the bottom of the first processing hole from the side of the first plate away from the target plate, the second processing hole penetrating through the target copper layer.
[0018] In some embodiments, with the surface of the remaining second plating layer away from the surface of the first plate as a first reference surface, a fourth hole of a first preset depth is drilled at the bottom of the third hole, the bottom of the fourth hole extends to the surface of the target plate away from the surface of the first plate.
[0019] Using a depth control drill machine with a conductive detection function, the drill bit of the depth control drill machine is inserted into the bottom of the third hole;
[0020] When the drill tip of the drill contacts the surface of the second plating layer away from the first plate, drilling of the fourth hole is started until the fourth hole reaches the first preset depth.
[0021] In some embodiments, the second plate includes a barrier copper layer, and the second plate has a keep-out area; before drilling a third hole in the substrate from a side of the second plate away from the target plate, the PCB back drilling method further includes: removing the barrier copper layer in the keep-out area; when drilling the third hole in the substrate from the side of the second plate away from the target plate, the third hole is located in the keep-out area.
[0022] In some embodiments, the barrier copper layer in the keep-out area is removed by etching or laser burning.
[0023] In some embodiments, the same alignment target is used when drilling the second hole in the substrate from the side of the second plate away from the target plate and when drilling the third hole in the substrate from the side of the second plate away from the target plate.
[0024] In some embodiments, the alignment target is arranged as a plurality of through holes at the edge of the substrate.
[0025] Embodiments of the second aspect of the application provide a PCB, which is processed by the PCB back drilling method as described in the first aspect.
[0026] The PCB back drilling method provided by the embodiments of the application has the beneficial effects that: by drilling a second hole in the substrate from a side of a second plate away from a target plate, removing a third plating layer and part of a second plating layer, drilling a third hole in the substrate from the side of the second plate away from the target plate so that the third hole extends to a surface of the second plating layer away from a first plate, and finally drilling a fourth hole in the third hole to a first preset depth with the surface of the second plating layer away from the first plate as a first reference surface and removing the remaining second plating layer, the residual second plating layer and the third plating layer can be removed more accurately, and the quality of the PCB is improved.
[0027] The PCB provided by the application has the beneficial effects compared with the prior art, which are the same as the beneficial effects of the PCB back drilling method provided by the application compared with the prior art, and will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS
[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0029] Figure 1 This is a flowchart of a PCB back-drilling method in one embodiment of this application;
[0030] Figure 2 (a) is a schematic diagram of the substrate structure after drilling through holes in one embodiment of this application;
[0031] Figure 2 (b) in the middle is Figure 2 The schematic diagram of the structure after drilling the first sub-hole on the substrate shown in (a) is shown in the figure;
[0032] Figure 3 (a) in the text refers to Figure 2 The schematic diagram of the structure after metallization of the first and second sub-holes on the substrate shown in (b) is shown in the figure.
[0033] Figure 3 (b) in the middle is Figure 3 The schematic diagram of the structure after drilling a second hole in the substrate shown in (a) is shown in the figure;
[0034] Figure 4 Is Figure 3 (b) shows a schematic diagram of the structure after drilling the fourth hole in the substrate;
[0035] Figure 5 Is Figure 2 The diagram in (a) shows the first sub-hole, the second hole, the third hole, and the fourth hole drilled on the substrate.
[0036] The markings in the diagram mean:
[0037] 100, Substrate; 10, Target board; 11, Target copper layer; 20, First board; 21, First copper layer; 30, Second board; 31, Barrier copper layer; 40, First hole; 41, First sub-hole; 411, First plating layer; 412, Second plating layer; 42, Second sub-hole; 421, Third plating layer; 50, Second hole; 60, Third hole; 70, Through hole. Detailed Implementation
[0038] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.
[0039] It is to be noted that when an element is referred to as being "fixed" or "set" on another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or indirectly connected to the other element.
[0040] In addition, the terms "first", "second", "third", etc. are used only to describe purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.
[0041] In the description of the present application, the reference "one embodiment", "some embodiments" or "embodiments" means that the specific features, structures or characteristics described in connection with the embodiment are included in one or more embodiments of the present application. Therefore, the statements "in one embodiment", "in some embodiments", "in other some embodiments", "in other some embodiments" and the like appearing in the description are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized. In addition, in one or more embodiments, specific features, structures or characteristics can be combined in any suitable manner.
[0042] In order to illustrate the technical solutions of the present application, the following will be described in combination with specific drawings and embodiments.
[0043] Please refer to Figure 1 , Figure 3 (a) and Figure 5 , the embodiment of the first aspect of the present application provides a PCB back drilling method, comprising:
[0044] S100: providing a substrate 100, the substrate 100 includes a target plate 10 and a first plate 20 and a second plate 30 respectively arranged on the opposite sides of the target plate 10, the substrate 100 is provided with a first hole 40, the first hole 40 penetrates the substrate 100, the first hole 40 includes coaxial and communicating first sub-hole 41 and second sub-hole 42, the aperture of the first sub-hole 41 is larger than the aperture of the second sub-hole 42, the first sub-hole 41 penetrates the first plate 20 and the target plate 10, the hole wall of the first sub-hole 41, the hole bottom of the first sub-hole 41 and the hole wall of the second sub-hole 42 are respectively provided with first plating layer 411, second plating layer 412 and third plating layer 421, the first plating layer 411 is electrically connected with the circuit of the first plate 20 and the circuit of the target plate 10.
[0045] Specifically, the substrate 100 can be a circuit board after the conventional process flow of cutting, inner layer circuit pattern, inner layer AOI detection and pressing, etc. The first hole 40 is a metallized through hole, the first sub-hole 41 has a hole diameter of d2, the second sub-hole 42 has a hole diameter of d1, the first sub-hole 41 penetrates the first plate 20 and the target plate 10 but does not penetrate the second plate 30, so the second plating layer 412, the third plating layer 421 and the part of the first plating layer 411 located on the side of the target plate 10 away from the first plate 20 are invalid sections that will form parasitic capacitance and parasitic inductance, and the height of the invalid section is h1. The invalid section will affect the integrity of high-speed signal transmission in the circuit board.
[0046] It can be understood that the first plate 20 and the second plate 30 can be provided with multiple layers of circuit lines, and the first plating layer 411, the second plating layer 412 and the third plating layer 421 are all metal plating layers that can conduct electricity.
[0047] S200: Drill a second hole 50 penetrating the second plating layer 412 on the substrate 100, remove the third plating layer 421 and part of the second plating layer 412, the second hole 50 is coaxially arranged with the first hole 40, the hole diameter of the second hole 50 is greater than the hole diameter of the second sub-hole 42, and the hole diameter of the second hole 50 is less than the hole diameter of the first sub-hole 41.
[0048] Specifically, please refer to (b) in Figure 3 , the second hole 50 penetrating the second plating layer 412 can be drilled on the substrate 100 from the side of the second plate 30 away from the target plate 10 or the side of the first plate 20 away from the target plate 10, the hole diameter of the second hole 50 is d3, after drilling the second hole 50, the third plating layer 421 and the second plating layer 412 with a height of h2 are removed, as shown in Figure 5 h2 = 1 / 2(d3-d1) / tanα, α is half of the drill tip angle of the depth control drill used to drill the second hole 50, and the invalid section on the substrate 100 only remains another part of the second plating layer 412 with a height of h3 and part of the first plating layer 411 located on the side of the target plate 10 away from the first plate 20.
[0049] S300: Drill a third hole 60 on the substrate 100 from the side of the second plate 30 away from the target plate 10, the third hole 60 extends to the surface of the remaining second plating layer 412 away from the first plate 20, the third hole 60 is coaxially arranged with the first hole 40, and the hole diameter of the third hole 60 is greater than the hole diameter of the second hole 50.
[0050] Specifically, please refer to Figure 4 , the hole diameter of the third hole 60 is d4.
[0051] S400: taking the remaining second plating layer 412 away from the surface of the first plate 20 as the first reference surface, drilling a fourth hole of a first preset depth at the bottom of the third hole 60, and removing the remaining second plating layer 412, the bottom of the fourth hole extending to the surface of the target plate 10 away from the first plate 20.
[0052] Specifically, since the fourth hole of the first preset depth is drilled at the bottom of the third hole 60 with the remaining second plating layer 412 away from the surface of the first plate 20 as the first reference surface, the influence of the uniformity of the substrate 100 thickness and the influence of the drilling machine precision can be reduced, the drilling precision of the fourth hole is improved, and the bottom of the fourth hole is ensured to extend more accurately to the surface of the target plate 10 away from the first plate 20, and the remaining second plating layer 412 is removed without damaging the target plate 10.
[0053] It can be understood that the first preset depth can be set in advance, that is, the distance between the second plating layer 412 away from the surface of the first plate 20 and the surface of the target plate 10 away from the first plate 20 is directly calculated by a theoretical value, or it can also be determined after sampling and measuring a plurality of substrates 100, such as providing a plurality of samples of substrates 100 without drilling the third hole 60, cutting the plurality of samples of substrates 100 to measure the distance between the second plating layer 412 away from the surface of the first plate 20 and the surface of the target plate 10 away from the first plate 20, obtaining a plurality of first measurement values, and then taking the average value of the plurality of first measurement values as the first preset depth. In this way, the value of the first preset depth can be more accurate.
[0054] It can be understood that the fourth hole and the third hole 60 can be coaxial or non-coaxial. The fourth hole and the third hole 60 can be drilled together, that is, the third hole 60 is drilled on the substrate 100 from the side of the second plate 30 away from the target plate 10 using a depth control drill machine, the bottom of the third hole 60 extends to the surface of the second plating layer 412 away from the first plate 20, and then the fourth hole of the first preset depth is drilled at the bottom of the third hole 60 with the remaining second plating layer 412 away from the surface of the first plate 20 as the first reference surface. At this time, the diameter of the third hole 60 is equal to the diameter of the fourth hole, and the third hole 60 and the fourth hole are coaxial.
[0055] The PCB back drilling method provided by the embodiments of the present application can drill the second hole 50 on the substrate 100 from the side of the second plate 30 away from the target plate 10, remove the third plating layer 421 and part of the second plating layer 412, drill the third hole 60 on the substrate 100 from the side of the second plate 30 away from the target plate 10, so that the third hole 60 extends to the surface of the second plating layer 412 away from the first plate 20, and finally drill the fourth hole with a first preset depth at the bottom of the third hole 60 with the surface of the second plating layer 412 away from the first plate 20 as a first reference surface, and remove the remaining second plating layer 412, so that the remaining second plating layer 412 and the third plating layer 421 can be removed more accurately, and the quality of the PCB is improved.
[0056] As one of the modes that can be implemented, the fourth hole with a first preset depth is drilled at the bottom of the third hole 60 with the surface of the remaining second plating layer 412 away from the first plate 20 as a first reference surface, and the remaining second plating layer 412 is removed, and specifically includes the following steps.
[0057] In the first step, the depth control drill machine with a conductive detection function is used, and the drill bit of the depth control drill machine is inserted into the bottom of the third hole 60.
[0058] In the second step, when the drill tip of the drill bit contacts the surface of the second plating layer 412 away from the first plate 20, the fourth hole is started to be drilled until the fourth hole has a first preset depth.
[0059] Specifically, when the conductive detection system on the depth control drill machine detects that the drill tip of the drill bit contacts the surface of the second plating layer 412 away from the first plate 20, the conductive detection system feeds back a signal to the control system on the depth control drill machine, the control system reads and records the height position of the drill bit at this time, and then the motor on the depth control drill machine continues to drive the drill bit to feed downward, and when the feeding distance is the first preset depth, the Z-axis motor stops feeding. In this way, the depth of the fourth hole can be accurately controlled, so that the remaining second plating layer 412 can be removed more accurately, and the remaining invalid section is less.
[0060] Please refer to (b) in Figure 3 In some embodiments, the second plate 30 includes a barrier copper layer 31, and the second plate 30 has an avoidance area. Before the third hole 60 is drilled on the substrate 100 from the side of the second plate 30 away from the target plate 10, the PCB back drilling method further includes removing the barrier copper layer 31 in the avoidance area.
[0061] When the third hole 60 is drilled on the substrate 100 from the side of the second plate 30 away from the target plate 10, the third hole 60 is located in the avoidance area.
[0062] By using the above scheme, the conductive detection system will only feed back a signal to the control system on the depth control drill when the drill tip on the depth control drill contacts the second plating layer 412 away from the surface of the first plate 20.
[0063] In this embodiment, the barrier copper layer 31 in the avoidance area is removed by etching or laser burning.
[0064] It can be understood that if multiple layers of barrier copper layers 31 are arranged in a spaced manner, all barrier copper layers 31 located in the avoidance area are removed.
[0065] Please refer to Figure 4 In some embodiments, in order to simultaneously remove the part of the first plating layer 411 on the target plate 10 away from the first plate 20, the fourth hole is coaxially arranged with the first hole 40, and the aperture of the fourth hole is greater than or equal to the aperture of the first sub-hole 41. In this way, after the fourth hole is drilled, the remaining part of the second plating layer 412 with a height of h3 on the substrate 100 and the part of the first plating layer 411 on the target plate 10 away from the first plate 20 can be removed together and accurately, and the target plate 10 will not be damaged.
[0066] Please refer to Figure 2 (a) of Figure 2 (b) of Figure 3 (a) and Figure 5 In some embodiments, before providing a substrate 100, the PCB back drilling method further comprises:
[0067] First, a through hole 70 is drilled on the substrate 100, and the through hole 70 penetrates the first plate 20, the target plate 10 and the second plate 30.
[0068] Specifically, the through hole 70 penetrating the first plate 20, the target plate 10 and the second plate 30 can be drilled on the substrate 100 from the side of the second plate 30 away from the target plate 10 or the side of the first plate 20 away from the target plate 10, and the aperture of the through hole 70 is d1.
[0069] Secondly, the first sub-hole 41 is drilled at the through hole 70 of the substrate 100 from the side of the first plate 20 away from the target plate 10, and the aperture of the first sub-hole 41 is greater than the aperture of the through hole 70, and the remaining through hole 70 is the second sub-hole 42.
[0070] Finally, the first sub-hole 41 and the second sub-hole 42 are subjected to a metalization treatment, so that the first plating layer 411, the second plating layer 412 and the third plating layer 421 are respectively formed on the hole wall of the first sub-hole 41, the hole bottom of the first sub-hole 41 and the hole wall of the second sub-hole 42.
[0071] Specifically, the first sub-hole 41 and the second sub-hole 42 can be subjected to a metalization treatment in a manner of copper plating, so as to form a first plating layer 411, a second plating layer 412 and a third plating layer 421 with a preset thickness on the hole wall of the first sub-hole 41, the hole bottom of the first sub-hole 41 and the hole wall of the second sub-hole 42 respectively, but not limited thereto. In the embodiment, the first plating layer 411, the second plating layer 412 and the third plating layer 421 are all copper layers.
[0072] Please refer to Figure 2 (a) in Figure 2 (b) in Figure 3 (a) and Figure 5 In some embodiments, the first sub-hole 41 includes a first processing hole and a second processing hole connected to each other, and the target plate 10 includes a target copper layer 11. The first sub-hole 41 is drilled from the side of the first plate 20 away from the target plate 10 on the substrate 100, and the first sub-hole 41 penetrates the first plate 20 and the target plate 10, specifically including:
[0073] First, the first processing hole is drilled from the side of the first plate 20 away from the target plate 10 on the substrate 100, and the first processing hole penetrates the first plate 20.
[0074] Specifically, the first processing hole extends to the side of the target copper layer 11 close to the first plate 20.
[0075] Second, the second processing hole with a second preset depth is drilled from the bottom of the first processing hole from the side of the first plate 20 away from the target plate 10, with the side of the target copper layer 11 close to the first plate 20 as a second reference surface, and the second processing hole penetrates the target copper layer 11.
[0076] By adopting the above scheme, the precision when drilling the second processing hole can be higher, so as to more accurately ensure that the first sub-hole 41 penetrates the first plate 20 and the target plate 10, and reduce the influence of the thickness uniformity of the substrate 100 and the influence of the drilling machine precision.
[0077] It can be understood that the first processing hole and the second processing hole can be drilled together, that is, a depth control drilling machine is used to first drill the first processing hole from the side of the first plate 20 away from the target plate 10 on the substrate 100, and the first processing hole penetrates the first plate 20, and then the second processing hole with a second preset depth is drilled from the bottom of the first sub-hole 41 from the side of the first plate 20 away from the target plate 10, with the side of the target copper layer 11 close to the first plate 20 as a second reference surface. At this time, the hole diameter of the first processing hole is equal to the hole diameter of the second processing hole, and the first processing hole and the second processing hole are coaxially arranged.
[0078] It can be understood that the second preset depth can be set in advance, that is, the distance between the side of the target copper layer 11 close to the first plate 20 and the surface of the target plate 10 away from the first plate 20 is directly calculated by a theoretical value, or the second preset depth can also be determined by sampling and measuring a plurality of substrates 100. For example, a plurality of samples of substrates 100 without first processing holes are provided, the plurality of samples of substrates 100 are cut to measure the distance between the side of the target copper layer 11 close to the first plate 20 and the surface of the target plate 10 away from the first plate 20, a plurality of second measurement values are obtained, and the average value of the plurality of second measurement values is taken as the second preset depth. In this way, the setting value of the second preset depth can be more accurate.
[0079] As one of the ways that can be implemented, the side of the target copper layer 11 close to the first plate 20 is taken as the second reference surface, and a second processing hole with a second preset depth is drilled from the side of the first plate 20 away from the target plate 10 at the bottom of the first processing hole. Specifically, the method comprises the following steps:
[0080] Firstly, a depth control drill machine with a conductive detection function is used, and the drill bit of the depth control drill machine is inserted into the bottom of the first processing hole.
[0081] Secondly, when the drill tip of the drill bit contacts the side of the target copper layer 11 close to the first plate 20, the second processing hole with the second preset depth is started to be drilled.
[0082] Specifically, when the conductive detection system on the depth control drill machine detects that the drill tip of the drill bit contacts the side of the target copper layer 11 close to the first plate 20, the conductive detection system feeds back a signal to the control system on the depth control drill machine, and the control system reads and records the height position of the drill bit at this time. Then, the motor on the depth control drill machine continues to drive the drill bit to feed downward, and when the feeding distance is the second preset depth, the Z-axis motor stops feeding. In this way, the depth of the second processing hole can be accurately controlled.
[0083] Please refer to (b) in Figure 2 In some embodiments, the first plate 20 includes a first copper layer 21, and the first plate 20 has a first area.
[0084] Before drilling the first processing hole on the substrate 100 plate from the side of the first plate 20 away from the target plate 10, the drilling method further comprises: removing the first copper layer 21 in the first area; and when the first processing hole is drilled on the substrate 100 plate from the side of the first plate 20 away from the target plate 10, the first processing hole is located in the first area.
[0085] By adopting the above scheme, the conductive detection system can only feed back a signal to the control system on the depth control drill machine when the drill tip of the drill bit on the depth control drill machine contacts the side of the target copper layer 11 close to the first plate 20.
[0086] In the embodiment, the first copper layer 21 of the first region can be removed by etching or laser burning.
[0087] Please refer to Figure 3 (b) and Figure 4 In some embodiments, the same alignment target (not shown in the figure) is used when drilling the second hole 50 through the second plating layer 412 on the substrate 100 from the side of the second plate 30 away from the target plate 10 and when drilling the third hole 60 on the substrate 100 from the side of the second plate 30 away from the target plate 10. In this way, the offset between the axis of the drilled second hole 50 and the axis of the third hole 60 can be minimized.
[0088] Optionally, the alignment target described above is also used when drilling the through hole 70, the first processing hole and the second processing hole on the substrate 100.
[0089] In the embodiment, the alignment target is set as a plurality of through holes 70 at the edge of the substrate 100. In this way, more accurate alignment can be achieved when drilling the second hole 50 through the second plating layer 412 on the substrate 100 from the side of the second plate 30 away from the target plate 10 and when drilling the third hole 60 on the substrate 100 from the side of the second plate 30 away from the target plate 10, and the impact on the circuit on the substrate 100 can be reduced.
[0090] Optionally, the number of through holes 70 is more than 3.
[0091] The embodiment of the second aspect of the application provides a PCB processed by the PCB back drilling method of the first aspect.
[0092] The PCB provided by the embodiment of the application can be more accurately processed, and the quality of the PCB is higher.
[0093] The above examples are only used to illustrate the technical solutions of the present application, but not limit the same; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent ones; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.
Claims
1. A PCB back drilling method characterized by, The application relates to a PCB back drilling method. The PCB back drilling method comprises the following steps: providing a substrate, wherein the substrate comprises a target plate and a first plate and a second plate arranged on opposite sides of the target plate respectively, a first hole is arranged on the substrate, the first hole penetrates the substrate, the first hole comprises coaxial and communicating first and second sub-holes, the first sub-hole has a larger aperture than the second sub-hole, the first sub-hole penetrates the first plate and the target plate, a first plating layer, a second plating layer and a third plating layer are arranged on the hole wall of the first sub-hole, the hole bottom of the first sub-hole and the hole wall of the second sub-hole respectively, and the first plating layer is electrically connected to the circuit of the first plate and the circuit of the target plate; drilling a second hole penetrating the second plating layer on the substrate, the third plating layer and part of the second plating layer are removed, the second hole is coaxial with the first hole, the aperture of the second hole is larger than that of the second sub-hole, and the aperture of the second hole is smaller than that of the first sub-hole; drilling a third hole on the substrate from the side of the second plate away from the target plate, the third hole extends to the surface of the remaining second plating layer away from the first plate, the third hole is coaxial with the first hole, and the aperture of the third hole is larger than that of the second hole; 2. The PCB back drilling method of claim 1, wherein, taking the surface of the remaining second plating layer away from the first plate as a first reference surface, drilling a fourth hole with a first preset depth at the bottom of the third hole, removing the remaining second plating layer, the bottom of the fourth hole extends to the surface of the target plate away from the first plate, the aperture of the third hole is equal to that of the fourth hole, and the third hole is coaxial with the fourth hole; wherein the first preset depth is the distance between the surface of the second plating layer away from the first plate and the surface of the target plate away from the first plate calculated by a theoretical value; or providing a plurality of samples of the substrate without drilling the third hole, cutting the samples of the substrate to measure the distance between the surface of the second plating layer away from the first plate and the surface of the target plate away from the first plate, obtaining a plurality of first measurement values, and taking the average value of the first measurement values as the first preset depth.
3. The PCB back drilling method of claim 1, wherein, The fourth hole is coaxial with the first hole, and the aperture of the fourth hole is larger than or equal to that of the first sub-hole. Before providing the substrate, the PCB back drilling method further comprises: drilling a through hole on the substrate, wherein the through hole penetrates the first plate, the target plate and the second plate; drilling the first sub-hole on the through hole of the substrate from the side of the first plate away from the target plate, wherein the aperture of the first sub-hole is larger than that of the through hole, and the remaining through hole is a second sub-hole; carrying out a metallization treatment on the first sub-hole and the second sub-hole, so that the first plating layer, the second plating layer and the third plating layer are respectively formed on the hole wall of the first sub-hole, the hole bottom of the first sub-hole and the hole wall of the second sub-hole.
4. The PCB back drilling method of claim 3, wherein, The first sub-hole includes a first processing hole and a second processing hole in communication, and the target plate includes a target copper layer; a first sub-hole is drilled on the substrate from a side of the first plate away from the target plate, the first sub-hole penetrating through the first plate and the target plate, and specifically including: A first processing hole is drilled on the substrate from a side of the first plate away from the target plate, the first processing hole penetrating through the first plate; A second processing hole with a second preset depth is drilled on the bottom of the first processing hole from a side of the first plate away from the target plate with the target copper layer close to the first plate as a second reference surface, the second processing hole penetrating through the target copper layer.
5. The PCB back drilling method of claim 1, wherein, A fourth hole with a first preset depth is drilled on the bottom of the third hole with a surface of the remaining second plating layer away from the first plate as a first reference surface, and the remaining second plating layer is removed, and specifically including: A depth control drill machine with a conductive detection function is used, and a drill bit of the depth control drill machine is inserted into the bottom of the third hole; When a drill tip of the drill bit contacts a surface of the second plating layer away from the first plate, the fourth hole is drilled until the fourth hole has the first preset depth.
6. The PCB back drilling method of claim 5, wherein, The second plate includes a barrier copper layer, and the second plate has an avoidance area; before a third hole is drilled on the substrate from a side of the second plate away from the target plate, the PCB back drilling method further includes: removing the barrier copper layer in the avoidance area; when the third hole is drilled on the substrate from a side of the second plate away from the target plate, the third hole is located in the avoidance area.
7. The PCB back drilling method of claim 6, wherein, The barrier copper layer in the avoidance area is removed by etching or laser burning.
8. The PCB back drilling method according to any one of claims 1 to 7, characterized in that, A same alignment target is used when a second hole penetrating through the second plating layer is drilled on the substrate from a side of the second plate away from the target plate and when the third hole is drilled on the substrate from a side of the second plate away from the target plate.
9. The PCB back drilling method of claim 8, wherein, The alignment target is arranged as a plurality of through holes at an edge of the substrate.
10. A PCB characterized by, The PCB is processed by the PCB back drilling method according to any one of claims 1 to 9.
Citation Information
Patent Citations
Drilling method for multilayer plate
CN106735387A
PCB manufacturing method and PCB
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