A method for back drilling of a circuit board and a circuit board

Abstract

The present application provides a backdrilling method for a circuit board and a circuit board. The backdrilling method provided by the present application first obtains a board to be backdrilled, and the board to be backdrilled includes metalized holes to be backdrilled, as well as a conductive circuit layer and a dielectric layer. Then, based on the backdrilled holes to be obtained and the dielectric layer, a region for calculating the residual copper rate is determined, and based on the region for calculating the residual copper rate, the backdrilling depth of the backdrilled holes is determined. The metalized holes to be backdrilled are backdrilled based on the backdrilling depth to obtain backdrilled holes. The backdrilling depth is calculated according to the position of the backdrilled holes and backdrilling is performed, reducing or even eliminating the Stub control error caused by uneven board thickness / dielectric thickness, thereby improving the backdrilling accuracy of backdrilling to remove residual stubs Stub.

Description

Technical Field

[0001] This application relates to the technical field of circuit boards, and particularly to a backdrilling method for circuit boards and a circuit board. Background Art

[0002] With the continuous promotion of the information industry, the speed of digital signal transmission is getting faster and faster, and the frequency is getting higher and higher. Ensuring the integrity of signals is becoming increasingly critical. A section of the copper in the via hole in the circuit board that is not used for signal transmission and is useless will increase the loss of signal transmission in the circuit board. And when the frequency of the circuit signal increases to a certain level, the excess copper plating of the useless copper in the via hole is equivalent to an antenna, generating signal radiation and interfering with other signals around it. In severe cases, it will damage the integrity of signal transmission. Therefore, the backdrilling processing method is usually used to drill off the excess copper plating as much as possible by backdrilling, so as to reduce its impact on the signal transmission of the via hole board.

[0003] However, for the currently commonly used depth-controlled backdrilling, due to various factors such as uneven board thickness and dielectric thickness, and irregular inner layer pattern design, the backdrilling accuracy of backdrilling to remove residual stubs according to the preset backdrilling depth is insufficient, resulting in a large signal loss in the signal holes, and it is difficult to meet the high-frequency and high-speed performance requirements of products.

[0004] Therefore, how to improve the backdrilling accuracy is a major problem in circuit board processing. Summary of the Invention

[0005] This application provides a backdrilling method for a circuit board and a circuit board to solve the problem of low backdrilling accuracy of backdrilling to remove residual stubs.

[0006] To solve the above technical problems, a technical solution adopted by this application is: to provide a backdrilling method for a circuit board, including: obtaining a board to be backdrilled, the board to be backdrilled including a via hole to be backdrilled, as well as a conductive circuit layer and a dielectric layer; determining a region for calculating the residual copper rate based on the to-be-obtained backdrilled hole and the dielectric layer; determining the backdrilling depth of the backdrilled hole based on the region for calculating the residual copper rate; and performing backdrilling on the via hole to be backdrilled based on the backdrilling depth to obtain a backdrilled hole.

[0007] Optionally, the step of determining the region for calculating the residual copper rate based on the to-be-obtained backdrilled hole and the dielectric layer includes: determining the region for calculating the residual copper rate based on the diameter of the to-be-obtained backdrilled hole and the material flow compensation value of the dielectric layer.

[0008] Optionally, the step of determining the backdrilling depth of the backdrilled hole based on the region for calculating the residual copper rate includes: within the region for calculating the residual copper rate, determining the thickness of each dielectric layer based on the flow filling of the dielectric layer; and determining the backdrilling depth of the backdrilled hole based on the thickness of the dielectric layer.

[0009] Optionally, within the region for calculating the copper residue rate, the step of determining the thickness of each dielectric layer based on the flow condition and filling condition of the dielectric layer includes: within the region for calculating the copper residue rate, determining the thickness of each dielectric layer based on the flow performance and filling condition of the dielectric layer, as well as the expansion and contraction condition of the dielectric layer.

[0010] Optionally, the to-be-back-drilled board includes a plurality of the to-be-back-drilled metallized holes; the step of determining the region for calculating the copper residue rate based on the to-be-obtained back-drilled holes and the dielectric layer includes: according to each to-be-back-drilled metallized hole and the dielectric layer, determining the region for calculating the copper residue rate corresponding to each to-be-back-drilled metallized hole; the step of determining the back-drilling depth of the to-be-back-drilled metallized hole based on the region for calculating the copper residue rate includes: based on the region for calculating the copper residue rate corresponding to each to-be-back-drilled metallized hole, determining the back-drilling depth of each to-be-back-drilled metallized hole.

[0011] Optionally, the to-be-back-drilled board includes a target signal layer; wherein, the target signal layer is the signal layer corresponding to the current back-drilling task; the step of determining the back-drilling depth of the back-drilled hole based on the region for calculating the copper residue rate includes: based on the region for calculating the copper residue rate, determining a first spacing, wherein the first spacing is the spacing from the surface of the to-be-back-drilled side of the to-be-back-drilled board to the target signal layer; based on the first spacing, the drill tip compensation value, the copper thickness compensation value of the copper plating, and the target control value of the residual stub length of the metallized hole, determining the back-drilling depth of the back-drilled hole.

[0012] Optionally, the to-be-back-drilled board includes a conductive reference layer and a target signal layer; wherein, the target signal layer is the signal layer corresponding to the current back-drilling task; the step of determining the back-drilling depth of the back-drilled hole based on the region for calculating the copper residue rate includes: based on the region for calculating the copper residue rate, determining a second spacing, wherein the second spacing is the spacing between the conductive reference layer and the target signal layer; based on the second spacing, determining the back-drilling depth of the back-drilled hole.

[0013] Optionally, the step of determining the back-drilling depth of the back-drilled hole based on the second spacing includes: based on the second spacing, the drill tip compensation value, the copper thickness compensation value of the copper plating, and the target control value of the residual stub length of the metallized hole, determining the back-drilling depth of the back-drilled hole.

[0014] Optionally, the step of performing back-drilling on the to-be-back-drilled metallized hole based on the back-drilling depth to obtain the back-drilled hole includes: controlling the back-drilling bit to move from the surface of the to-be-back-drilled side of the to-be-back-drilled board towards the target signal layer for the first back-drilling until reaching the conductive reference layer, and obtaining the first back-drilling depth; retracting the back-drilling bit, and based on the first back-drilling depth, the second spacing, the drill tip compensation value, the copper thickness compensation value of the copper plating, and the target control value of the residual stub length of the metallized hole, determining the second back-drilling depth of the back-drilled hole; controlling the back-drilling bit to move from the surface of the to-be-back-drilled side towards the target signal layer with the second back-drilling depth to complete the second back-drilling.

[0015] Optionally, the conductive reference layer is the ground layer, power layer, or other signal layer of the board to be back-drilled.

[0016] To solve the above technical problems, another technical solution adopted in this application is: to provide a circuit board manufactured by the back-drilling method described in any one of the above.

[0017] The beneficial effects of this application are as follows: Different from the prior art, this application provides a back-drilling method for a circuit board. In this processing method, the board to be back-drilled is first obtained. The board to be back-drilled includes metalized holes to be back-drilled, a conductive circuit layer, and a dielectric layer. Then, based on the back-drilled holes to be obtained and the dielectric layer, the area for calculating the residual copper rate is determined. Based on the area for calculating the residual copper rate, the back-drilling depth of the back-drilled holes is determined. Based on the back-drilling depth, the metalized holes to be back-drilled are back-drilled to obtain back-drilled holes. The back-drilling depth is calculated according to the position of the back-drilled holes and back-drilling is performed, reducing or even eliminating the Stub control error caused by uneven board thickness / dielectric thickness, thereby improving the back-drilling accuracy of back-drilling to remove residual stubs. Description of the Drawings

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the following will briefly introduce the drawings required for the descriptions of the embodiments and the prior art. Obviously, the following drawings are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 is a schematic flowchart of the first embodiment of the back-drilling method for the circuit board provided by this application;

[0020] Figure 2 is a schematic diagram of an area for calculating the residual copper rate provided by this application;

[0021] Figure 3 is a schematic flowchart of a specific embodiment of S103;

[0022] Figure 4 is a schematic structural diagram of a specific embodiment of the back-drilled board provided by this application;

[0023] Figure 5 is a schematic flowchart of the second embodiment of the back-drilling method provided by this application;

[0024] Figure 6 is a schematic flowchart of the third embodiment of the back-drilling method provided by this application. Detailed Embodiments

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope of protection of this application.

[0026] The terms "first", "second", and "third" in this application are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", and "third" may explicitly or implicitly include at least one of such features. In the description of this application, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically and clearly defined. All directional indications (such as up, down, left, right, front, back...) in the embodiments of this application are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally further include steps or units not listed, or may optionally further include other steps or units inherent to these processes, methods, products, or devices.

[0027] Referring to "embodiments" herein means that the specific features, structures, or characteristics described in connection with the embodiments may be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that, without conflict, the embodiments described herein may be combined with other embodiments. The following will be described in detail through specific embodiments respectively.

[0028] The circuit boards in this application include flexible printed circuit boards (FPCs), rigid printed circuit boards (RPCBs), rigid-flex printed circuit boards, etc., and can be multi-layer boards. When the circuit board is a multi-layer board, since the thickness of each layer of the multi-layer board may be uneven, and during the manufacturing process of the multi-layer board, uneven inner layer pattern design and processing, multi-layer board lamination, and uneven dielectric layer thickness will all cause the thickness of the circuit board to be uneven, and will also cause the thickness of the circuit board at different locations to be drilled to be different. In this case, when performing a back-drilling operation on multiple holes to be back-drilled on a circuit board according to a preset depth, the remaining stub length of the back-drilled hole may be too long, too short, or even the target signal layer may be drilled through, resulting in poor back-drilling accuracy, large signal loss in the signal hole, and even inability to function as a signal hole normally. Based on this, this application provides a back-drilling processing method and a circuit board for a circuit board to improve the back-drilling accuracy of removing remaining stubs.

[0029] Participate Figure 1 , Figure 1 is a schematic flowchart of the first embodiment of the back-drilling processing method of the circuit board provided in this application. The specific steps include:

[0030] S101: Obtain a board to be back-drilled, which includes a metalized hole to be back-drilled, as well as a conductive circuit layer and a dielectric layer.

[0031] In this step, the board to be back-drilled is a circuit board, which may include multiple conductive circuit layers and dielectric layers, as well as metalized holes to be back-drilled, where the metalized holes to be back-drilled can penetrate at least one conductive circuit layer and at least one dielectric layer. The specific manufacturing of this board to be back-drilled, including forming a conductive circuit layer, laminating each board of the conductive circuit layer with a dielectric layer, and drilling and metallizing the hole wall, etc., are all conventional circuit board processing operations and will not be described in this application.

[0032] The obtained board to be back-drilled will be used for step S102.

[0033] S102: Based on the back-drilled hole to be obtained and the dielectric layer, determine the area for calculating the residual copper rate.

[0034] On the board to be back-drilled, based on the back-drilled hole to be obtained and the dielectric layer at the back-drilled hole to be obtained, determine the area for calculating the residual copper rate corresponding to the back-drilled hole to be obtained.

[0035] Specifically, the area for calculating the residual copper rate can be determined based on the diameter of the back-drilled hole to be obtained and the material flow compensation value of the dielectric layer.

[0036] In a specific embodiment, the area for calculating the residual copper rate is circular. Refer to Figure 2 , Figure 2This is a schematic diagram of the residual copper rate calculation area provided by this application. The diameter of the residual copper rate calculation area is D, and D = d + W, where d is the back drill hole diameter and W is the flow compensation coefficient of the dielectric layer material. Specifically, the material of the dielectric layer can be prepreg resin, and then the resin flow compensation coefficient W is related to the properties of the resin itself. If the same resin model is used for the dielectric layer in the board to be back drilled, then W is a fixed value. Moreover, the resin flow compensation coefficient W is related to the dynamic viscosity of the resin. The smaller the dynamic viscosity, the stronger the resin fluidity, and the larger the value of the resin flow compensation coefficient W. In addition, the resin flow compensation coefficient W should be greater than 1.5d, that is, greater than 1.5 times the back drill hole diameter, to equalize the local calculation error.

[0037] S103: Based on the area for residual copper rate calculation, determine the back drill depth of the back drill hole.

[0038] Based on the area for residual copper rate calculation, for example, within a circular range with a diameter of D, determine the back drill depth of the back drill hole to be obtained, which can also be called depth control.

[0039] Specifically, refer to Figure 3 , Figure 3 This is a schematic flowchart of a specific embodiment of S103.

[0040] S301: Within the area for residual copper rate calculation, first determine the thickness of each dielectric layer based on the flow filling of the dielectric layer.

[0041] Specifically, in this step, within the area for residual copper rate calculation, based on the flow performance and filling situation of the dielectric layer, as well as the expansion and contraction situation of the dielectric layer, determine the thickness of each dielectric layer. For example, within a circular range with a diameter of D, when the dielectric layer is made of prepreg resin material, use the method of resin flow filling the copper - deficient part to increase the expansion - contraction ratio compensation and reduce the expansion - contraction error of the material after different processes, so as to determine the thickness of each dielectric layer, that is, the dielectric thickness. Of course, the area for residual copper rate calculation is not limited to a circle, and can also be regular shapes such as a square or a rectangle.

[0042] S302: Based on the thickness of the dielectric layer, determine the back drill depth of the back drill hole.

[0043] After obtaining the thickness of each dielectric layer, determine the back drill depth of the back drill hole.

[0044] In a specific embodiment, refer to Figure 4 , Figure 4 This is a schematic structural diagram of a specific embodiment of the back drill board provided by this application.

[0045] The board to be back drilled 10 is placed on the PCB drilling machine table 20. Specifically, the PCB drilling machine table 20 includes a machine table board 21, a backing plate 22, and a cover plate 23.

[0046] The backing plate 22 is disposed on one surface of the machine table plate 21, and the plate 10 to be back-drilled is placed on the surface of the backing plate 22 away from the machine table plate 21. A cover plate 23 is disposed on the surface of the plate 10 to be back-drilled away from the backing plate 22. When drilling, the back-drilling bit starts controlled-depth back-drilling from the surface of the cover plate 23 away from the plate 10 to be back-drilled. Among them, the plate 10 to be back-drilled includes a target signal layer 11, and the target signal layer 11 is the signal layer corresponding to the current back-drilling task.

[0047] Within the area for calculating the residual copper rate, a first spacing is determined, where the first spacing is the spacing from the surface of the plate 10 to be back-drilled to the target signal layer. Then, based on the first spacing, the drill tip compensation value, the copper plating thickness compensation value, and the target control value of the length of the residual stub of the metallized hole, the back-drilling depth of the back-drilled hole is determined. In this specific embodiment, since a cover plate 23 is provided on the surface of the plate 10 to be back-drilled for back-drilling, the cover plate 23 is used as the starting reference surface for back-drilling. Therefore, the first spacing H is the sum of the thicknesses from the cover plate 23 to the target signal layer 11, or the spacing from the surface of the cover plate 23 away from the plate 10 to be back-drilled to the target signal layer 11. That is, the first spacing H increases by the thickness of the cover plate 23.

[0048] Specifically, the magnitude of the back-drilling depth of the back-drilled hole, that is, the magnitude calculation formula of the controlled-depth value Z is Z = H - Stub + Z d +Z c +Z e ; where Stub is the target control value of the length of the residual stub of the metallized hole, Z d is the drill tip compensation value (related to factors such as the diameter of the through hole and the drill tip angle of the back-drilling bit), Z c is the copper plating thickness compensation value, and Z e is the board thickness compensation value. Specifically, Z e is the difference between the thickness of the cover plate used during back-drilling and the thickness value of the cover plate for through-hole drilling before the metallized hole of the metallized hole to be back-drilled. Here, the cover plate thickness is the theoretical value. If the same cover plate is used for the above two drilling operations, then Z e is zero.

[0049] S104: Based on the back-drilling depth, perform back-drilling on the metallized hole to be back-drilled to obtain a back-drilled hole.

[0050] Based on the back-drilling depth of the back-drilled hole calculated in S103, control the back-drilling bit to move from the surface of the plate to be back-drilled for back-drilling towards the target signal layer.

[0051] Combined with Figure 4 , then control the back-drilling bit to start from the surface of the cover plate 23 away from the plate 10 to be back-drilled and move towards the target signal layer with the back-drilling depth Z to complete back-drilling, so that the back-drilling does not drill through the target signal layer to obtain a back-drilled hole.

[0052] The backdrilling method of this embodiment first obtains a to-be-backdrilled board, then determines the area for calculating the residual copper ratio based on the to-be-obtained backdrilled holes and dielectric layers, and determines the backdrilling depth of the backdrilled holes based on the area for calculating the residual copper ratio corresponding to the to-be-obtained backdrilled holes. The to-be-backdrilled metallized holes are backdrilled based on the backdrilling depth to obtain backdrilled holes, thereby improving the backdrilling accuracy of removing residual stubs. Moreover, through the backdrilling method in this embodiment, the stub control error caused by the uneven thickness of each layer of the board and the dielectric layer is reduced or even eliminated, realizing high-precision control of the backdrilled stub.

[0053] When the to-be-backdrilled board includes multiple to-be-backdrilled metallized holes, the backdrilling method provided by this application refers to Figure 5 , Figure 5 which is a schematic flowchart of the second embodiment of the backdrilling method provided by this application. Specifically, it includes:

[0054] S501: Obtain the to-be-backdrilled board, which includes multiple to-be-backdrilled metallized holes, as well as a conductive circuit layer and a dielectric layer.

[0055] S502: Determine the area for calculating the residual copper ratio corresponding to each to-be-backdrilled metallized hole according to each to-be-backdrilled metallized hole and the dielectric layer.

[0056] S503: Determine the backdrilling depth of each to-be-backdrilled metallized hole based on the area for calculating the residual copper ratio corresponding to each to-be-backdrilled metallized hole.

[0057] S504: Perform backdrilling one by one based on the backdrilling depth of each to-be-backdrilled metallized hole to obtain multiple backdrilled holes.

[0058] The specific operations of steps S501 - S504 can refer to steps S101 - S104 and will not be elaborated here. Based on the first embodiment, this embodiment realizes high-precision depth control backdrilling of multiple to-be-backdrilled holes on one to-be-backdrilled board.

[0059] In this embodiment, by matching the area for calculating the residual copper ratio for each to-be-backdrilled hole on the to-be-backdrilled board and calculating the thickness of each dielectric layer at the position of each to-be-backdrilled hole, the dielectric thickness change at the position of each to-be-backdrilled hole during different backdrilling processes is considered, and the depth control depth of each backdrilled hole is calculated. The depth control depth takes into account the changes in board thickness and dielectric thickness. According to the depth control depth of each backdrilled hole, the corresponding to-be-backdrilled holes are drilled with depth control one by one to obtain multiple backdrilled holes. The backdrilling method in this embodiment eliminates the depth control depth error caused by the uneven board thickness and dielectric thickness on the same to-be-backdrilled board and the different changes in board thickness and dielectric thickness caused by different operations at different positions, improves the backdrilling accuracy, and realizes high-precision control of the backdrilled stub.

[0060] Refer to Figure 6, Figure 6 It is a schematic flow chart of the third embodiment of the back drilling method provided by this application. Specifically, it includes:

[0061] S601: Obtain a to-be-back-drilled board, which includes to-be-back-drilled metallized holes, a dielectric layer, a conductive reference layer, and a target signal layer; among them, the target signal layer is the signal layer corresponding to the current back drilling task.

[0062] In this embodiment, the conductive reference layer can be additionally provided, or an existing metal conductive layer in the circuit board can be used. For example, it can be a ground layer, a power layer, or other signal layers in the circuit board. That is, the original ground layer or power layer or other signal layer connected to the metallized hole can be set not to be connected to the metallized hole during the processing of the circuit board, or the ground layer or power layer or other signal layer that is not connected to the metallized hole can be directly used as the conductive layer.

[0063] S602: Based on the to-be-obtained back drill holes and the dielectric layer, determine the area for calculating the residual copper ratio.

[0064] For the description of this step, reference can be made to the description of S102, which will not be elaborated here.

[0065] S603: Based on the area for calculating the residual copper ratio, determine a second spacing, where the second spacing is the spacing between the conductive reference layer and the target signal layer.

[0066] Combined with Figure 4 , in addition to the target signal layer 11, the to-be-back-drilled board 10 further includes a conductive reference layer 12. The target signal layer 11 is the signal layer corresponding to the current back drilling task, and the conductive reference layer 12 is disposed between the surface conductive layer on the side for back drilling and the target signal layer 11. The second spacing h is the spacing between the target signal layer 11 and the conductive reference layer 12. In the area for calculating the residual copper ratio, the method of using resin flow to fill the copper-deficient part is adopted to increase the shrinkage and expansion ratio compensation to reduce the shrinkage and expansion error of the material after different manufacturing processes. Considering the changes in the dielectric thickness and the board thickness, the second spacing h is calculated. [[ID=2,4]]

[0067] S604: Based on the second spacing, determine the back drill depth of the back drill hole.

[0068] Specifically, the back drill depth of the back drill hole can be determined based on the second spacing, the drill tip compensation value, the copper plating thickness compensation value, and the target control value of the residual stub length of the metallized hole.

[0069] In a specific embodiment, combined with Figure 4 , the back drill depth of the second back drilling is Z' = Z1 - Z2 + h - Stub + Z d +Z c +Z e; where Z1 is the surface copper detection height, i.e., the detection distance from the cover plate 23 to the machine table plate 21; Z2 is the conductive reference layer copper detection height, or the detection distance between the conductive reference layer 12 and the machine table plate 21; Stub is the target control value of the length of the metallized hole stub, and Z d is the drill tip compensation value (related to factors such as the through-hole diameter and the drill tip angle of the back drill bit), and Z c is the copper plating thickness compensation value, and Z e is the board thickness compensation value. Specifically, Z e is the difference between the cover plate thickness used during back drilling and the cover plate thickness value of the through-hole drilling before the metallized hole to be back drilled. Here, the cover plate thickness is the theoretical value. If the same cover plate is used for the two drillings above, then Z e is zero. Among them, the value of (Z1 - Z2) is the actual detection depth when drilling to the conductive reference layer 12 during the first back drilling.

[0070] In this embodiment, the back drilling is divided into two times. Then, before this step, it also includes: controlling the back drill bit to move from the surface of the plate to be back drilled on the side for back drilling towards the target signal layer for the first back drilling until reaching the conductive reference layer, and obtaining the first back drilling depth. The first back drilling depth is the actual detection depth. After obtaining the actually detected first back drilling depth, based on the first back drilling depth, the second spacing, the drill tip compensation value, the copper plating thickness compensation value, and the target control value of the length of the metallized hole stub, determine the second back drilling depth of the back drilled hole.

[0071] S605: Perform back drilling on the metallized hole to be back drilled based on the back drilling depth to obtain a back drilled hole.

[0072] In the previous step, after drilling to the conductive reference layer and obtaining the first back drilling depth, retract the back drill bit. Then control the back drill bit to move from the surface on the side for back drilling towards the target signal layer with the calculated second back drilling depth to complete the second back drilling, thereby realizing back drilling on the metallized hole to be back drilled and obtaining a back drilled hole.

[0073] In this embodiment, a conductive reference layer is provided between the surface conductive layer on the side for back drilling and the target signal layer. Then, the distances between the conductive reference layer and the surface conductive layer on the side for back drilling, as well as between the conductive reference layer and the target signal layer, can be set accordingly according to specific circumstances. For example, the conductive reference layer can be set at a position closer to the target signal layer, that is to say, the distance between the conductive reference layer and the surface conductive layer on the side for back drilling is greater than the distance between the conductive reference layer and the target signal layer. In this case, since the depth of the first back drilling is the actual measured downward depth from the surface conductive layer on the side for back drilling until the drill bit touches the conductive reference layer, and the greater the actually measured first back drilling depth, the smaller the depth of back drilling from the conductive reference layer to the target signal layer, and the less affected the back drilling is by the board thickness error. The thickness error of the positive board is reduced to the board dielectric thickness error from the conductive reference layer to the target signal layer, thereby improving the back drilling accuracy and the Stub control accuracy. Further, by setting the area for calculating the residual copper rate, the corresponding back drilling depth is calculated for each hole to be back drilled, and the dielectric thickness change at each position of the back drilled hole during different back drilling processes is calculated. In particular, by using the conductive reference layer position detection and the board dielectric thickness calculation between the conductive reference layer and the target signal layer, the depth control depth of each back drilled hole with the change of board thickness / dielectric thickness is obtained, realizing the high-precision control of the back drilled Stub.

[0074] This application also provides a circuit board manufactured by the above back drilling processing method. The back drilling processing method provided by this application can reduce the influence of the board dielectric thickness on the back drilling processing, has high back drilling processing accuracy, can obtain signal holes with smaller metallized hole stub lengths (also called back drilling Stub lengths), reduce the signal loss of the signal holes, and meet the high-frequency and high-speed performance requirements of the product.

[0075] The above are only the embodiments of this application, and do not limit the patent scope of this application accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of this application, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of this application by the same token.

Claims

1. A method for back drilling of a circuit board, characterized in that, Including: Obtaining a to-be-back-drilled board, where the to-be-back-drilled board includes to-be-back-drilled metallized holes, as well as a conductive circuit layer and a dielectric layer; The to-be-back-drilled board includes a plurality of the to-be-back-drilled metallized holes; Based on the to-be-obtained back-drilled holes and the dielectric layer, determining an area for calculating the copper residue rate, including: according to each of the to-be-back-drilled metallized holes and the dielectric layer, determining an area for calculating the copper residue rate corresponding to each of the to-be-back-drilled metallized holes; Based on the area for calculating the copper residue rate, determining the back-drilling depth of the back-drilled holes, including: based on the area for calculating the copper residue rate corresponding to each of the to-be-back-drilled metallized holes, determining the back-drilling depth of each of the to-be-back-drilled metallized holes; Performing back-drilling on the to-be-back-drilled metallized holes based on the back-drilling depth to obtain the back-drilled holes; Among them, the step of determining the area for calculating the copper residue rate based on the to-be-obtained back-drilled holes and the dielectric layer includes: based on the diameter of the to-be-obtained back-drilled holes and the material flow compensation value of the dielectric layer, determining the area for calculating the copper residue rate; The step of determining the back-drilling depth of the back-drilled holes based on the area for calculating the copper residue rate includes: within the area for calculating the copper residue rate, based on the flow filling of the dielectric layer, determining the thickness of each layer of the dielectric layer; based on the thickness of the dielectric layer, determining the back-drilling depth of the back-drilled holes; The step of determining the thickness of each layer of the dielectric layer based on the flow filling of the dielectric layer within the area for calculating the copper residue rate includes: within the area for calculating the copper residue rate, based on the flow performance and filling situation of the dielectric layer, as well as the expansion and contraction situation of the dielectric layer, determining the thickness of each layer of the dielectric layer.

2. The back drilling method according to claim 1, characterized in that, The to-be-back-drilled board includes a target signal layer; among them, the target signal layer is the signal layer corresponding to the current back-drilling task; The step of determining the back-drilling depth of the back-drilled holes based on the area for calculating the copper residue rate includes: Based on the area for calculating the copper residue rate, determining a first spacing, where the first spacing is the spacing from the to-be-back-drilled side surface of the to-be-back-drilled board to the target signal layer; Based on the first spacing, the drill tip compensation value, the copper plating thickness compensation value, and the target control value of the metallized hole stub length, determining the back-drilling depth of the back-drilled holes.

3. The back drilling method according to claim 1, wherein The to-be-back-drilled board includes a conductive reference layer and a target signal layer; among them, the target signal layer is the signal layer corresponding to the current back-drilling task; The step of determining the back-drilling depth of the back-drilled holes based on the area for calculating the copper residue rate includes: Based on the area for calculating the copper residue rate, determining a second spacing, where the second spacing is the spacing between the conductive reference layer and the target signal layer; Based on the second spacing, determining the back-drilling depth of the back-drilled holes.

4. The back drilling method according to claim 3, characterized in that, The step of determining the back-drilling depth of the back-drilled holes based on the second spacing includes: Based on the second spacing, the drill tip compensation value, the copper plating thickness compensation value, and the target control value of the metallized hole stub length, determining the back-drilling depth of the back-drilled holes.

5. The back drilling method according to claim 4, wherein The step of performing back-drilling on the to-be-back-drilled metallized holes based on the back-drilling depth to obtain the back-drilled holes includes: Control the backdrill bit to move from the surface of the board to be backdrilled on the side for backdrilling towards the target signal layer for the first backdrilling, drill to the conductive reference layer, and obtain the first backdrilling depth; Retract the backdrill bit, and determine the second backdrilling depth of the backdrilled hole based on the first backdrilling depth, the second spacing, the drill tip compensation value, the copper plating thickness compensation value, and the target control value of the length of the metalized hole stub; Control the backdrill bit to move from the surface of the side for backdrilling towards the target signal layer with the second backdrilling depth to complete the second backdrilling.

Images