Back drilling processing method of circuit board and circuit board

Abstract

The present application discloses a backdrilling method for a circuit board and a circuit board, comprising: obtaining a circuit board to be backdrilled; wherein the circuit board to be backdrilled comprises a first conductive layer, a target signal layer, and a second conductive layer; drilling a pre-drilled hole at a preset position on the first conductive layer, and obtaining a first spacing between the first surface of the first conductive layer and a machine platform using a pre-drilling drill bit; drilling a through hole at the pre-drilled hole, and obtaining a second spacing between the second surface of the second conductive layer and the machine platform using a through hole drill bit; obtaining the thickness of the second conductive layer, and obtaining the actual thickness of the circuit board to be backdrilled based on the first spacing, the second spacing, and the thickness of the second conductive layer; calculating an actual control depth value based on the actual circuit thickness, and controlling the backdrilling drill bit to drill a backdrilled hole to the target signal layer at the through hole on the first surface to the actual control depth value. The present application can accurately detect the actual circuit board thickness while adding pre-drilling, thereby achieving high-precision control of the backdrilled stump length.

Description

Technical Field

[0001] The present application relates to the field of circuit board processing, and in particular to a back drilling processing method for a circuit board and a circuit board. Background Art

[0002] With the continuous advancement of the information industry, digital signal transmission speeds are increasing, and frequencies are rising. Maintaining signal integrity is becoming increasingly critical. Unused copper in a plated via in a circuit board (PCB) increases signal transmission losses. Furthermore, when the frequency of circuit signals reaches a certain level, the excess copper plating in this unused via acts as an antenna, radiating signals and interfering with surrounding signals. In severe cases, this can compromise signal integrity. Therefore, backdrilling is commonly used to remove as much excess copper as possible, thereby minimizing its impact on signal transmission in PCBs.

[0003] Currently, a pre-set backdrill depth is typically set, and then backdrilling the plated holes to that depth to remove excess copper. However, in actual production, due to various factors such as uneven board thickness and internal layer pattern design, backdrilling to remove residual copper based on the preset backdrill depth can result in insufficient backdrilling accuracy. This results in significant signal loss in the signal holes, making it difficult to meet the high-frequency and high-speed performance requirements of the product.

[0004] In the existing technology, the impact of uneven board thickness is reduced by detecting the board thickness when processing through holes and outputting the depth control value proportionally. However, when the circuit board is multi-layered, pre-drilling is often required before drilling the through holes to improve the hole position accuracy. However, how to accurately detect the board thickness after adding pre-drilling is a major problem in circuit board processing. Summary of the Invention

[0005] The main technical problem solved by the present application is to provide a backdrilling processing method for a circuit board and a circuit board. The method obtains a first distance between the first surface of the first conductive layer of the board to be backdrilled and the machine by pre-drilling, and obtains a second distance between the second surface of the second conductive layer of the board to be backdrilled and the machine by through-hole drilling. The actual thickness of the board to be backdrilled is calculated based on the first distance, the second distance and the thickness of the second conductive layer. This method can solve the problem of being unable to accurately detect the thickness of the circuit board after adding pre-drilling.

[0006] To solve the above technical problems, the first technical solution adopted in the present application is to provide a backdrilling processing method for a circuit board, comprising: obtaining a board to be backdrilled; wherein the board to be backdrilled includes a first conductive layer, a target signal layer, and a second conductive layer; wherein the first conductive layer, the target signal layer, and the second conductive layer are stacked in sequence; drilling a pre-drilled hole at a preset position of the first conductive layer, and obtaining a first spacing between a first surface of the first conductive layer and a machine platform by a pre-drilling drill bit; wherein the first surface is a side surface of the first conductive layer away from the target signal layer; drilling a through hole at the pre-drilled hole, and obtaining a second spacing between a second surface of the second conductive layer and the machine platform by a through hole drill bit; wherein the second surface is a side surface of the second conductive layer close to the target signal layer; obtaining a thickness of the second conductive layer, and obtaining an actual board thickness of the board to be backdrilled based on the first spacing, the second spacing, and the thickness of the second conductive layer; calculating an actual control depth value according to a preset ratio based on the actual board thickness, and controlling the backdrilling drill bit to drill a backdrill hole to the actual control depth value at the through hole on the first surface toward the target signal layer, without drilling through the target signal layer.

[0007] Among them, the step of drilling a pre-drilled hole at a preset position of the first conductive layer and obtaining a first spacing between the first surface of the first conductive layer and the machine platform through a pre-drilling drill bit includes: drilling a pre-drilled hole at a preset position of the board to be back-drilled, and obtaining the first spacing when the drill tip of the pre-drilling drill bit contacts the first surface of the first conductive layer; the step of drilling a through hole at the pre-drilled hole and obtaining a second spacing between the second surface of the second conductive layer and the machine platform through a through hole drill bit includes: drilling a through hole at the pre-drilled hole, and obtaining the second spacing when the drill tip of the through hole drill bit contacts the second surface of the second conductive layer.

[0008] Among them, before the step of drilling a pre-drilled hole at a preset position of the first conductive layer and obtaining a first distance between the first surface of the first conductive layer and the machine platform through a pre-drilling drill bit, it also includes: obtaining a third distance between the drill tip of the pre-drilling drill bit and the machine platform; before the step of drilling a through hole at the pre-drilled hole and obtaining a second distance between the second surface of the second conductive layer and the machine platform through a through-hole drill bit, it also includes: obtaining a fourth distance between the drill tip of the through-hole drill bit and the machine platform.

[0009] Among them, the step of obtaining the thickness of the second conductive layer and obtaining the actual thickness of the board to be backdrilled based on the first spacing, the second spacing and the thickness of the second conductive layer also includes: obtaining the thickness of the second conductive layer and obtaining the actual thickness of the board to be backdrilled based on the first spacing, the second spacing, the third spacing, the fourth spacing and the thickness of the second conductive layer.

[0010] Among them, the steps of calculating the actual control depth value according to a preset ratio based on the actual board thickness, controlling the backdrill bit to drill a backdrill hole of the actual control depth value at the through hole on the first surface toward the target signal layer, and the backdrill hole does not drill through the target signal layer, include: obtaining the theoretical board thickness of the board to be backdrilled and the theoretical position of the target signal layer in the board to be backdrilled; determining the theoretical control depth value according to the theoretical board thickness and the theoretical position, and obtaining the ratio of the theoretical control depth value to the theoretical board thickness; calculating the actual control depth value based on the actual board thickness and the ratio of the theoretical control depth value to the theoretical board thickness, controlling the backdrill bit to drill a backdrill hole of the actual control depth value at the through hole on the first surface toward the target signal layer, and the backdrill hole does not drill through the target signal layer.

[0011] The diameter of the pre-drilled hole is not larger than the diameter of the through hole.

[0012] The diameter of the pre-drilled hole is not less than the difference between the diameter of the through hole and a set value.

[0013] The diameter of the back-drilled hole is larger than the diameter of the through hole.

[0014] After drilling a through hole at the pre-drilled hole and obtaining a second distance between the second surface of the second conductive layer and the machine platform through a through hole drill bit, the method further includes: copper plating the back-drilled board to form a metallized through hole.

[0015] In order to solve the above technical problems, the second technical solution adopted in this application is to provide a circuit board, which is manufactured by the above-mentioned back drilling processing method.

[0016] The beneficial effect of the present application is that, different from the prior art, the present application provides a backdrilling processing method for a circuit board and a circuit board, which obtains a first distance between the first surface of the first conductive layer of the board to be backdrilled and the machine platform by pre-drilling, and obtains a second distance between the second surface of the second conductive layer of the board to be backdrilled and the machine platform by through-hole drilling, and calculates the actual thickness of the board to be backdrilled based on the first distance, the second distance and the thickness of the second conductive layer, thereby improving the detection accuracy of the actual board thickness, and then determining the actual control depth value based on the obtained actual board thickness, which can reduce the drilling error caused by uneven board thickness at different positions of the circuit board, thereby improving the backdrilling accuracy of the circuit board and achieving high-precision control of the backdrilled residual pile length. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1This is a flow chart of a first embodiment of the backdrilling method for a circuit board of the present application;

[0019] Figure 2 This is a structural diagram of an embodiment of a board to be back-drilled provided by the present application;

[0020] Figure 3 is a structural diagram of an embodiment of a board to be back-drilled after pre-drilling in step S12;

[0021] Figure 4 2 is a schematic structural diagram of an embodiment of a board to be back-drilled after the through hole is drilled in step S13;

[0022] Figure 5 yes Figure 1 A flow chart of a specific implementation of step S15;

[0023] Figure 6 This is a schematic structural diagram of an embodiment of a circuit board provided by this application;

[0024] Figure 7 It is a flow chart of another embodiment of the back drilling method for a circuit board of the present application. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0026] The terms used in the examples of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms "a," "the," and "the" used in the examples of this application and the appended claims are also intended to include plural forms. Unless otherwise clearly indicated above, "a plurality" generally includes at least two, but does not exclude the inclusion of at least one.

[0027] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0028] It should be understood that the terms "comprises," "comprising," or any other variations used herein are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0029] The circuit boards in this application include printed circuit boards, PCB boards, FPC circuit boards, etc., and can be multi-layer boards. When the circuit boards are multi-layer boards, the thickness of each layer in the multi-layer board may be uneven. In addition, during the multi-layer board manufacturing process, the inner layer graphic design and processing, as well as the multi-layer board lamination, can lead to uneven thickness of the circuit board. This can also lead to uneven distances between the surface conductive layer on the side used for backdrilling and the target signal layer corresponding to the current backdrilling task.

[0030] In this case, conventional backdrilling to a preset depth can result in the backdrilled hole being too long or too short, or even drilling through the target signal layer. This can lead to poor backdrilling accuracy, significant signal loss, or even failure to function properly. Existing techniques mitigate the impact of uneven board thickness by detecting board thickness during through-hole processing and outputting a proportional depth control value. However, for multi-layer PCBs, pre-drilling is often required before drilling through-holes to improve hole position accuracy. However, accurately detecting board thickness after pre-drilling is a major challenge in PCB processing.

[0031] Based on the above situation, the present application provides a backdrilling processing method for a circuit board and a circuit board, which obtains a first distance between the first surface of the first conductive layer of the board to be backdrilled and the machine through pre-drilling, and obtains a second distance between the second surface of the second conductive layer of the board to be backdrilled and the machine through through-hole drilling, and calculates the actual thickness of the board to be backdrilled based on the first distance, the second distance and the thickness of the second conductive layer, which can solve the problem of not being able to accurately detect the thickness of the circuit board after adding pre-drilling.

[0032] See also Figure 1 , Figure 1 This is a flow chart of an embodiment of the back drilling method of the circuit board of the present application. Figure 1 As shown, in this embodiment, the method includes:

[0033] S11: Obtain a board to be back-drilled; wherein the board to be back-drilled includes a first conductive layer, a target signal layer, and a second conductive layer; wherein the first conductive layer, the target signal layer, and the second conductive layer are stacked in sequence.

[0034] In this embodiment, the board to be back-drilled is obtained by lamination.

[0035] Lamination refers to a method of combining two or more layers of the same or different materials into a whole by applying heat and pressure with or without adhesives.

[0036] In this embodiment, the board to be backdrilled may have multiple signal layers, and the target signal layer is the signal layer corresponding to the current backdrilling task.

[0037] Specifically, see Figure 2 , Figure 2 It is a structural schematic diagram of an embodiment of a board to be back-drilled provided in this application.

[0038] like Figure 2 As shown, the backdrilled board 20 includes a first conductive layer 21, a target signal layer 23, and a second conductive layer 22. The first conductive layer 21, the target signal layer 23, and the second conductive layer 22 are stacked in sequence. A first surface 201 is the surface of the first conductive layer 21 away from the target signal layer 23, and a second surface 202 is the surface of the second conductive layer 22 closer to the target signal layer 23.

[0039] The first surface 201 includes at least one preset position 204 , and the preset position 204 is a position set for pre-drilling.

[0040] S12: Drill a pre-drilled hole at a preset position of the first conductive layer, and obtain a first distance between the first surface of the first conductive layer and the machine platform through a pre-drilling drill bit; wherein the first surface is a side surface of the first conductive layer away from the target signal layer.

[0041] In this embodiment, a pre-drilled hole is drilled at a preset position of the board to be back-drilled, and the first spacing is obtained when the drill tip of the pre-drilling drill bit contacts the first surface of the first conductive layer.

[0042] Specifically, when the drill tip of the pre-drilling drill bit contacts the first surface of the first conductive layer, the height value of the first surface relative to the machine platform at this time is recorded by the laser acquisition spindle and recorded as the first distance.

[0043] Furthermore, there can be multiple preset positions. When pre-drilling holes at multiple preset positions, the system will record multiple first spacings and assign values ​​to the first spacings at the corresponding back-drilled holes to facilitate subsequent plate thickness calculations.

[0044] Understandably, due to the short blade length and high rigidity of the pre-drill, the position and depth of the pre-drilled hole are less deviated from the preset position. However, due to the long blade length and low rigidity of the through-hole drill, directly drilling the through-hole may cause the through-hole to deviate significantly from the preset position. Therefore, when the board to be back-drilled is a multi-layer board, it is necessary to add pre-drilling to form the pre-drilled hole. During subsequent through-hole processing, the through-hole drill is guided by the pre-drilled hole to improve the hole position accuracy. In addition, due to the presence of the pre-drilled hole, the subsequent through-hole drill bit cannot accurately capture the height of the first surface relative to the machine when the drill tip contacts the pre-drilled hole. Therefore, it is necessary to capture the height value of the first surface relative to the machine when the drill tip of the pre-drill drill bit just contacts the first surface, so as to facilitate the subsequent accurate calculation of the actual thickness of the board to be back-drilled.

[0045] Specifically, see Figure 3 , Figure 3 1 is a structural diagram of an embodiment of a board to be back-drilled after pre-drilling in step S12.

[0046] like Figure 3 As shown, the backdrilled board 30 includes a first conductive layer 21, a target signal layer 23, and a second conductive layer 22. The first conductive layer 21, the target signal layer 23, and the second conductive layer 22 are stacked in sequence. The first surface 201 is the surface of the first conductive layer 21 away from the target signal layer 23, and the second surface 202 is the surface of the second conductive layer 22 closer to the target signal layer 23.

[0047] Among them, the first surface 201 includes at least one pre-drilled hole 301. When the drill tip of the pre-drill drill bit contacts the first surface 201 of the first conductive layer 21, the height value of the first surface 201 relative to the machine 101 at this time is recorded by the laser acquisition spindle and recorded as the first distance Z1.

[0048] S13: Drilling a through hole at the pre-drilled hole, and obtaining a second distance between the second surface of the second conductive layer and the machine platform through a through hole drill bit; wherein the second surface is a side surface of the second conductive layer close to the target signal layer.

[0049] In this embodiment, a through hole is drilled at the pre-drilled hole, and the second spacing is obtained when the drill tip of the through hole drill bit contacts the second surface of the second conductive layer.

[0050] Specifically, when the drill tip of the through-hole drill bit contacts the second surface of the second conductive layer, the height value of the second surface relative to the machine platform at this time is recorded by the laser acquisition spindle and recorded as the second distance.

[0051] In this embodiment, the diameter of the pre-drilled hole is not larger than the diameter of the through hole, and the diameter of the pre-drilled hole is not smaller than the difference between the diameter of the through hole and a set value.

[0052] The set value is 0.05 mm. In other embodiments, the set value may also be 0.03, 0.04 or other values, which are not limited in this application.

[0053] It is understandable that after pre-drilling, the copper at the preset position is reduced, and the copper area contacted by the through-hole drill becomes smaller, which will affect the through-hole drill's detection of the drilling position. Therefore, setting the aperture of the pre-drilled hole to be close to the size of the through-hole can play a good guiding role for the through-hole drill, so that the through-hole drill can perform through-hole processing based on the pre-drilled hole, avoiding the influence of the subsequent drilling signal due to the weakening of the surface copper signal.

[0054] Furthermore, after the through holes are drilled, copper plating is performed on the back-drilled board to form metallized through holes, wherein the metallized through holes are signal transmission holes.

[0055] Specifically, see Figure 4 , Figure 4 1 is a schematic structural diagram of an embodiment of a board to be back-drilled after the through holes are drilled in step S13.

[0056] like Figure 4 As shown, the backdrilled board 40 includes a first conductive layer 21, a target signal layer 23, and a second conductive layer 22. The first conductive layer 21, the target signal layer 23, and the second conductive layer 22 are stacked in sequence. A first surface 201 is the surface of the first conductive layer 21 away from the target signal layer 23, and a second surface 202 is the surface of the second conductive layer 22 closer to the target signal layer 23.

[0057] Among them, the back-drilled board 40 includes at least one through hole 302. When the drill tip of the through-hole drill bit contacts the second surface 202 of the second conductive layer 22, the height value of the second surface 202 relative to the machine 101 at this time is recorded by the laser acquisition spindle and recorded as the second distance Z2.

[0058] The relationship between the diameter d of the through hole 302 and the diameter w of the pre-drilled hole 301 is:

[0059] d-0.05mm≤w≤d

[0060] S14: Obtain the thickness of the second conductive layer, and obtain the actual thickness of the board to be backdrilled based on the first spacing, the second spacing, and the thickness of the second conductive layer.

[0061] Specifically, see Figure 4 , the thickness of the second conductive layer 22 is h, then the actual thickness of the backdrilled board 30 is:

[0062] T=Z1-Z2+h

[0063] It can be understood that by obtaining a first distance Z1 between the first surface 201 of the first conductive layer 21 of the board to be back-drilled 30 and the machine 101 through pre-drilling, and obtaining a second distance Z2 between the second surface 202 of the second conductive layer 22 of the board to be back-drilled 30 and the machine 101 through through-hole drilling, and calculating the actual thickness T of the board to be back-drilled 30 based on the first distance Z1, the second distance Z2, and the thickness h of the second conductive layer 22, the accuracy of detecting the actual board thickness T can be improved.

[0064] S15: Calculating an actual depth control value according to a preset ratio based on the actual board thickness, and controlling the backdrilling drill bit to drill a backdrill hole of the actual depth control value at the through hole of the first surface toward the target signal layer, without drilling through the target signal layer.

[0065] Specifically, see Figure 5 , Figure 5 yes Figure 1 Schematic diagram of a specific implementation of step S15 in FIG. Figure 5 As shown, the steps of calculating the actual control depth value according to a preset ratio based on the actual board thickness, controlling the back drilling bit to drill a back drilling hole to the actual control depth value at the through hole on the first surface toward the target signal layer, and the back drilling hole does not penetrate the target signal layer, include:

[0066] S51: Obtaining a theoretical thickness of the board to be back-drilled and a theoretical position of a target signal layer in the board to be back-drilled.

[0067] S52: Determine a theoretical depth control value according to the theoretical plate thickness and the theoretical position, and obtain a ratio of the theoretical depth control value to the theoretical plate thickness.

[0068] Specifically, the theoretical controlled depth value is the back drilling depth preset according to the theoretical plate thickness and the theoretical position.

[0069] In this embodiment, the theoretical controlled depth value is the maximum depth of the backdrilling hole without drilling through the target signal layer. In other embodiments, the theoretical controlled depth value is other depths of the backdrilling hole without drilling through the target signal layer, which is not limited in this application.

[0070] It can be understood that when the theoretical controlled depth value is the maximum depth at which the backdrilling does not penetrate the target signal layer, useless copper in the metallized through hole can be removed to the maximum extent, thereby reducing its impact on the signal transmission of the metallized through hole plate.

[0071] S53: Calculating an actual control depth value based on the actual board thickness and the ratio of the theoretical control depth value to the theoretical board thickness, and controlling the back drill bit to drill a back drill hole of the actual control depth value at the through hole on the first surface toward the target signal layer, without drilling through the target signal layer.

[0072] Specifically, the ratio of the actual plate thickness to the actual controlled depth value is equal to the ratio of the theoretical controlled depth value to the theoretical plate thickness. Therefore, the actual controlled depth value can be calculated based on the actual plate thickness and the ratio of the theoretical controlled depth value to the theoretical plate thickness.

[0073] It can be understood that when the detection accuracy of the actual board thickness is high, the actual control depth value obtained is also relatively accurate. Controlling the back-drilling drill bit for back-drilling according to the accurate actual control depth value can reduce the drilling error caused by uneven board thickness at different positions of the circuit board, thereby improving the back-drilling accuracy of the circuit board and achieving high-precision control of the length of the back-drilled residual pile.

[0074] In this embodiment, the diameter of the back-drilled hole is larger than the diameter of the through hole.

[0075] It can be understood that only when the aperture of the back-drilled hole is larger than the aperture of the through hole can the back-drilled hole completely remove the corresponding section of useless hole copper in the metallized through hole that is not used for signal transmission, thereby reducing the signal transmission loss in the circuit board to ensure signal integrity.

[0076] Specifically, see Figure 6 , Figure 6 It is a structural schematic diagram of an embodiment of a circuit board provided in this application.

[0077] like Figure 6 As shown, circuit board 50 includes a first conductive layer 21, a target signal layer 23, and a second conductive layer 22. The first conductive layer 21, the target signal layer 23, and the second conductive layer 22 are stacked in sequence. A first surface 201 is a side of the first conductive layer 21 away from the target signal layer 23, and a second surface 202 is a side of the second conductive layer 22 closer to the target signal layer 23.

[0078] The circuit board 50 includes at least one back-drilled hole 303. The diameter D of the back-drilled hole 303 is larger than the diameter d of the through hole 302. The actual controlled depth H of the back-drilled hole 303 is calculated as follows:

[0079] H = (theoretical control depth value / theoretical plate thickness) × T

[0080] Different from the existing technology, this embodiment adds pre-drilling before drilling through holes, which can improve the hole position accuracy, and obtains the first distance between the first surface of the first conductive layer of the board to be back-drilled and the machine through pre-drilling, and obtains the second distance between the second surface of the second conductive layer of the board to be back-drilled and the machine through through-hole drilling, and calculates the actual thickness of the board to be back-drilled based on the first distance, the second distance and the thickness of the second conductive layer, which can improve the detection accuracy of the actual board thickness, and then determine the actual control depth value according to the actual board thickness obtained, which can reduce the drilling error caused by uneven board thickness at different positions of the circuit board, thereby improving the back-drilling accuracy of the circuit board and achieving high-precision control of the length of the back-drilled residual pile.

[0081] See also Figure 7 , Figure 7 This is a flow chart of another embodiment of the back drilling method for the circuit board of the present application. Figure 7 As shown, in this embodiment, the method includes:

[0082] S71: Acquire a board to be back-drilled; wherein the board to be back-drilled comprises a first conductive layer, a target signal layer, and a second conductive layer; wherein the first conductive layer, the target signal layer, and the second conductive layer are stacked in sequence.

[0083] In this embodiment, the board to be back-drilled is obtained by lamination.

[0084] In this embodiment, the board to be backdrilled may have multiple signal layers, and the target signal layer is the signal layer corresponding to the current backdrilling task.

[0085] S72: Obtain a third distance between the drill tip of the pre-drilling drill bit and the machine platform.

[0086] Before pre-drilling and through-hole drilling, the relative positions of the pre-drill drill bit and the through-hole drill bit are the same, but the positions of the drill collars of the two may deviate, which in turn leads to a height difference between the drill tips of the two relative to the laser detection spindle. Therefore, it is necessary to use the laser detection spindle to grasp the third distance between the drill tip of the pre-drill drill bit and the machine before pre-drilling, and then use the laser detection spindle to grasp the fourth distance between the drill tip of the through-hole drill bit and the machine before through-hole drilling.

[0087] S73: Drill a pre-drilled hole at a preset position of the first conductive layer, and obtain a first distance between the first surface of the first conductive layer and the machine platform through a pre-drilling drill bit; wherein the first surface is a side surface of the first conductive layer away from the target signal layer.

[0088] In this embodiment, a pre-drilled hole is drilled at a preset position of the board to be back-drilled, and the first spacing is obtained when the drill tip of the pre-drilling drill bit contacts the first surface of the first conductive layer.

[0089] Specifically, when the drill tip of the pre-drilling drill bit contacts the first surface of the first conductive layer, the height value of the first surface relative to the machine platform at this time is recorded by the laser acquisition spindle and recorded as the first distance.

[0090] S74: Obtain a fourth distance between the drill tip of the through-hole drill bit and the machine platform.

[0091] S75: Drilling a through hole at the pre-drilled hole, and obtaining a second distance between the second surface of the second conductive layer and the machine platform through a through hole drill bit; wherein the second surface is a side surface of the second conductive layer close to the target signal layer.

[0092] In this embodiment, a through hole is drilled at the pre-drilled hole, and the second spacing is obtained when the drill tip of the through hole drill bit contacts the second surface of the second conductive layer.

[0093] Specifically, when the drill tip of the through-hole drill bit contacts the second surface of the second conductive layer, the height value of the second surface relative to the machine platform at this time is recorded by the laser acquisition spindle and recorded as the second distance.

[0094] In this embodiment, the diameter of the pre-drilled hole is not larger than the diameter of the through hole, and the diameter of the pre-drilled hole is not smaller than the difference between the diameter of the through hole and a set value.

[0095] S76: Obtain the thickness of the second conductive layer, and obtain the actual thickness of the board to be backdrilled based on the first spacing, the second spacing, the third spacing, the fourth spacing, and the thickness of the second conductive layer.

[0096] In this embodiment, the actual plate thickness is calculated using the following formula:

[0097] T=(Z1-Z2)+(Z3-Z4)+h

[0098] Wherein, T is the actual plate thickness, Z1 is the first spacing, Z2 is the second spacing, Z3 is the third spacing, Z4 is the fourth spacing, and h is the thickness of the second conductive layer.

[0099] It can be understood that by using laser to detect the height difference between the spindle grabbing the pre-drilling drill bit and the drill tip of the through-hole drill bit relative to the spindle, the height difference can be compensated, thereby further improving the calculation accuracy of the actual plate thickness.

[0100] S77: Calculating an actual depth control value according to a preset ratio based on the actual board thickness, and controlling the backdrill drill bit to drill a backdrill hole of the actual depth control value at the through hole of the first surface toward the target signal layer, without drilling through the target signal layer.

[0101] Different from the existing technology, this embodiment adds pre-drilling before drilling through holes, which can improve the hole position accuracy. The first distance between the first surface of the first conductive layer of the board to be back-drilled and the machine is obtained by pre-drilling, and the second distance between the second surface of the second conductive layer of the board to be back-drilled and the machine is obtained by through-hole drilling. In addition, before pre-drilling and before through-hole drilling, the third distance between the drill tip of the pre-drilling drill bit and the machine and the fourth distance between the drill tip of the through-hole drill bit and the machine are obtained respectively. The actual thickness of the board to be back-drilled is calculated based on the first distance, the second distance, the third distance, the fourth distance and the thickness of the second conductive layer. This can compensate for the height difference and further improve the calculation accuracy of the actual board thickness. Then, the actual control depth value is determined according to the actual board thickness obtained, which can reduce the drilling error caused by uneven board thickness at different positions of the circuit board, thereby improving the back-drilling accuracy of the circuit board and achieving high-precision control of the length of the back-drilled residual pile.

[0102] Correspondingly, the present application provides a circuit board, which is manufactured by the above-mentioned back drilling processing method. Figure 6 , I will not go into details here.

[0103] The above description is only an implementation method of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A back drilling method for a circuit board, characterized in that: include: Obtaining a board to be back-drilled; wherein the board to be back-drilled comprises a first conductive layer, a target signal layer, and a second conductive layer; wherein the first conductive layer, the target signal layer, and the second conductive layer are stacked in sequence; Drilling a pre-drilled hole at a preset position of the first conductive layer and obtaining a first distance between the first surface of the first conductive layer and the machine platform using a pre-drilling drill bit, including: drilling the pre-drilled hole at the preset position of the board to be back-drilled, and obtaining the first distance when the drill tip of the pre-drilling drill bit contacts the first surface of the first conductive layer; wherein the first surface is a side surface of the first conductive layer away from the target signal layer; Drilling a through hole at the pre-drilled hole and obtaining a second distance between the second surface of the second conductive layer and the machine platform using a through hole drill bit, including: drilling the through hole at the pre-drilled hole and obtaining the second distance when the drill tip of the through hole drill bit contacts the second surface of the second conductive layer; wherein the second surface is a side surface of the second conductive layer close to the target signal layer; Obtaining a thickness of the second conductive layer, and obtaining an actual thickness of the board to be backdrilled based on the first spacing, the second spacing, and the thickness of the second conductive layer; An actual depth control value is calculated based on the actual board thickness according to a preset ratio, and a backdrill drill bit is controlled to drill a backdrill hole of the actual depth control value toward the target signal layer at the through hole of the first surface, without drilling through the target signal layer.

2. The back drilling method according to claim 1, wherein: Before the step of drilling a pre-drilled hole at a preset position of the first conductive layer and obtaining a first distance between the first surface of the first conductive layer and the machine platform by a pre-drilling drill bit, the method further includes: Obtaining a third distance between the drill tip of the pre-drilling drill bit and the machine platform; Before the step of drilling a through hole at the pre-drilled hole and obtaining a second distance between the second surface of the second conductive layer and the machine platform by a through hole drill bit, the method further includes: A fourth distance between the drill tip of the through-hole drill bit and the machine platform is obtained.

3. The back drilling method according to claim 2, wherein: The step of obtaining the thickness of the second conductive layer and obtaining the actual thickness of the board to be backdrilled based on the first spacing, the second spacing, and the thickness of the second conductive layer further includes: The thickness of the second conductive layer is obtained, and the actual thickness of the board to be backdrilled is obtained based on the first spacing, the second spacing, the third spacing, the fourth spacing, and the thickness of the second conductive layer.

4. The back drilling method according to claim 1, wherein: The step of calculating an actual control depth value according to a preset ratio based on the actual board thickness, controlling a backdrill drill bit to drill a backdrill hole of the actual control depth value toward the target signal layer at the through hole of the first surface, and the backdrill hole does not penetrate the target signal layer, includes: Obtaining a theoretical thickness of the board to be back-drilled and a theoretical position of the target signal layer in the board to be back-drilled; Determine a theoretical depth control value according to the theoretical plate thickness and the theoretical position, and obtain a ratio of the theoretical depth control value to the theoretical plate thickness; The actual control depth value is calculated based on the actual board thickness and the ratio of the theoretical control depth value to the theoretical board thickness, and the back drill bit is controlled to drill the back drill hole of the actual control depth value toward the target signal layer at the through hole of the first surface, and the back drill hole does not penetrate the target signal layer.

5. The back drilling method according to claim 1, wherein: The diameter of the pre-drilled hole is no larger than the diameter of the through hole.

6. The back drilling method according to claim 5, wherein: The diameter of the pre-drilled hole is not less than the difference between the diameter of the through hole and a set value.

7. The back drilling method according to claim 1, wherein: The diameter of the back-drilled hole is larger than the diameter of the through hole.

8. The back drilling method according to claim 1, wherein: After the step of drilling a through hole at the pre-drilled hole and obtaining a second distance between the second surface of the second conductive layer and the machine platform by using a through hole drill bit, the method further includes: The backdrilled board is subjected to copper electroplating to form metallized through holes.

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

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