A back-drilling method for printed circuit boards

Abstract

The application discloses a back drilling processing method of a printed circuit board. By means of segmented drilling, the drill bit is completely withdrawn outside the hole after each peck drilling, the smooth discharge of the hole debris is ensured, the hole plugging phenomenon is avoided, and the chip removal capacity is improved. Meanwhile, the segmented processing mode makes each processing segment in a low heat accumulation state, effectively avoids the high-temperature damage in continuous drilling, thereby ensuring the quality of the hole wall, making the hole wall more smooth, and being beneficial to the reliable transmission of high-speed signals. By selecting drill bits with different blade lengths and matching the processing segment depths, the cutting resistance is reduced, the service life of the drill bit is prolonged, and the tool replacement frequency caused by excessive wear is reduced. In addition, the accurate control of the segmented depth enables the back drilling depth to be finely adjusted, avoids problems such as over drilling and copper wire residue, and improves the processing precision.

Description

Technical Field

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

[0002] In modern high-frequency, high-speed AI server printed circuit boards (PCBs), back drilling is widely used to remove excess residual vias (stubs) to improve signal integrity and reduce parasitic inductance. However, existing back drilling methods face a series of technical challenges when dealing with thicker PCBs. In particular, for ultra-thick boards exceeding 3mm in thickness, existing back drilling technologies suffer from problems such as difficult chip removal, heat buildup during cutting, and poor hole wall quality.

[0003] Current back drilling processes primarily utilize a single drilling operation or a single drill bit. When processing thicker PCBs, this method is prone to chip accumulation within the holes, which cannot be effectively removed, leading to chip blockage and potentially causing complete hole clogging, thus affecting machining accuracy. Furthermore, prolonged drilling can generate cutting heat, resulting in rough or damaged hole walls, increasing the drill bit wear rate and reducing its lifespan.

[0004] In existing technologies, single-pass drilling for deep holes can easily lead to over-drilling or copper wire residue, affecting hole quality and impacting subsequent electrical performance. Poor hole wall quality also significantly reduces signal transmission reliability, failing to meet the requirements of high-performance PCBs. Therefore, improving chip removal capability and drill bit life while ensuring hole wall quality and depth accuracy is a key technical challenge that current back-drilling technology needs to address. Summary of the Invention

[0005] The purpose of this application is to provide a back-drilling method for printed circuit boards, which solves the technical problems of difficult chip removal and poor depth control accuracy in the back-drilling process of ultra-thick printed circuit boards in the prior art.

[0006] To achieve this objective, the present application adopts the following technical solution: A method for back-drilling a printed circuit board, comprising: Obtain the basic processing information of the circuit board to be processed, construct back drilling processing parameters based on the basic processing information, and obtain segmented processing data corresponding to the circuit board to be processed; Based on the segmented processing data, the target back drilling depth is segmented and set. The corresponding drill bit is selected according to the segmentation results to obtain the back drilling tool set corresponding to each segment. The back drill bit assembly is controlled to sequentially drill the circuit board to be processed in segments. After each segment is processed, the current drill bit is controlled to exit the hole to a preset height, and the drill bit corresponding to the next segment is called to continue processing, so as to obtain a back drill board that reaches the target back drill depth. The back drill plate is then finished with final holes to obtain the processed printed circuit board.

[0007] Further, the steps of obtaining the basic processing information of the circuit board to be processed, constructing back-drilling processing parameters based on the basic processing information, and obtaining segmented processing data corresponding to the circuit board to be processed include: The layer structure information, back drill hole information, target machining depth information, and residual hole segment control information of the circuit board to be processed are obtained to obtain the basic machining information; Calculate the target back-drilling depth corresponding to each back-drilling hole based on the aforementioned processing basic information to obtain depth data; Based on the machining basic information and depth data, the spindle speed, feed rate, single pecking depth, retraction height and dressing parameters are set to obtain the back drilling machining parameters; The back-drilling machining parameters are matched with the corresponding back-drilling holes to generate the segmented machining data.

[0008] Furthermore, the step of obtaining the layer structure information, back-drilled hole information, target machining depth information, and residual hole segment control information of the circuit board to be processed includes: Obtain the board thickness information, lamination structure information, and conductive layer distribution information of the circuit board to be processed to obtain the layer structure data; Obtain the hole position coordinates, hole diameter and corresponding hole number of each back drill hole to obtain back drill hole data; Based on the conductive layer distribution information and the back drill hole data, the target machining endpoint of each back drill hole is obtained, and the target machining depth information is obtained. Based on the preset residual hole segment range, residual hole segment control information corresponding to each back drill hole is generated.

[0009] Further, the step of segmenting the target back-drilling depth according to the segmented machining data, selecting the corresponding drill bit according to the segmentation results, and obtaining the back-drilling tool set corresponding to each segment includes: Read the target back drill depth and single pecking amount from the segmented processing data, and divide the target back drill depth into at least two processing segments according to the preset segmentation rules; Based on the depth data of each machining segment, obtain the corresponding tool cutting length range, select multiple drill bits with different cutting lengths from drill bits with the same hole diameter, and match the multiple drill bits with each machining segment. The corresponding drill bits are sorted according to the processing segment sequence to obtain the back drill tool set; The preset segmentation rule is to segment the target back drilling depth according to the target back drilling depth, the single pecking amount, and the cutting edge length of the corresponding machining segment.

[0010] Furthermore, the step of obtaining the corresponding tool cutting length range based on the segment depth data of each machining segment, and selecting multiple drill bits with different cutting lengths from drill bits with the same hole diameter, includes: Obtain the segment depth and cumulative depth corresponding to each processing segment to obtain the segment depth sequence; Based on the segmented depth sequence, at least two types of drill bits are determined from the first segment drill bit, the middle segment drill bit, and the last segment drill bit. The drill bit with a shorter cutting edge is set as the preceding machining segment, and the drill bit with a longer cutting edge is set as the following machining segment.

[0011] Furthermore, the step of controlling the back drill bit assembly to sequentially perform segmented drilling on the circuit board to be processed, and controlling the current drill bit to withdraw from the hole to a preset height after each segment is processed, and calling the drill bit corresponding to the next segment to continue processing, includes: The drill bit corresponding to the first processing segment is lowered to the starting position, and the first processing segment is drilled according to the corresponding processing parameters to form the first segment hole; After the first segmented hole is formed, the current drill bit is controlled to retract along the original path to the preset height to obtain the first continuous drilling channel; Call the drill bit corresponding to the next processing segment to enter the first continuous drilling channel, and execute the next segment pecking drill according to the processing parameters corresponding to the next processing segment to form the updated segmented hole; Repeat the retraction and drilling steps until a back drill plate is formed that reaches the target back drill depth.

[0012] Furthermore, after the step of lowering the drill bit corresponding to the first machining segment to the starting position, the method further includes: Before the current machining segment begins, the spindle speed and feed rate parameters corresponding to that segment are called, and the current drill bit is controlled to cut downwards to the set segment depth according to the spindle speed and feed rate. After reaching the set segment depth, record the current hole depth data and update the hole depth data to the processing record of the corresponding hole position; The spindle speed, feed rate, and depth parameters for the next machining segment are retrieved based on the machining record to form the drilling command for the next machining segment.

[0013] Furthermore, the step of setting the spindle speed, feed rate, single peck depth, retraction height, and dressing parameters based on the machining foundation information and depth data includes: The range of single-pecking depth is determined based on the plate thickness and lamination structure information in the layer structure data, and the hole diameter information in the back-drilled hole data; wherein, the single-pecking depth is 0.05mm to 0.15mm. Based on the cumulative hole depth change corresponding to the target back drilling depth, the spindle speed and feed rate are set for different machining segments respectively; The reciprocating stroke, number of repairs, and rotation parameters in the final hole finishing are set according to the segment depth corresponding to the final processing segment.

[0014] Further, the step of performing final hole finishing on the back drill plate to obtain the processed printed circuit board includes: The last section of the drill bit is called into the already formed back drill hole, and the last section of the drill bit is controlled to perform short-stroke reciprocating repair to obtain the initial repair hole. After the initial finishing hole is formed, the final drill bit is controlled to rotate and finish to form the final finishing hole, resulting in the processed printed circuit board.

[0015] Furthermore, the step of obtaining a back drill plate that reaches the target back drill depth includes: After each processing segment is completed, obtain the actual hole depth data for the corresponding processing segment; The actual hole depth data is compared with the set segment depth corresponding to the processing segment to obtain the segment verification result; Based on the segmented verification results, the corresponding drill bits and processing parameters for the subsequent processing segments are called, and the subsequent segmented processing continues; When the actual hole depth reaches the target back drill depth, the back drill plate that has reached the target back drill depth is obtained.

[0016] Compared with the prior art, this application has the following beneficial effects: The back-drilling method for printed circuit boards disclosed in this application employs segmented drilling, with the drill bit completely withdrawn from the hole after each peck, ensuring smooth removal of debris and preventing hole blockage, thus improving chip removal capability. Simultaneously, the segmented processing method keeps each processing segment in a low-heat accumulation state, effectively avoiding high-temperature damage during continuous drilling, thereby ensuring the quality of the hole wall, making it smoother, and facilitating reliable transmission of high-speed signals. By selecting drill bits with different cutting lengths and matching them to the processing segment depth, not only is cutting resistance reduced, but the lifespan of the drill bits is also extended, reducing the frequency of tool replacement due to excessive wear. Furthermore, precise control of the segmented depth allows for more refined adjustment of the back-drilling depth, avoiding over-drilling and copper wire residue, and improving processing accuracy. In summary, this application improves the stability and reliability of PCB back-drilling processing, meeting the processing requirements of high-performance AI server circuit boards. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, 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.

[0018] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this application. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce.

[0019] Figure 1 This is a schematic diagram illustrating the overall steps of the back-drilling process for printed circuit boards. Detailed Implementation

[0020] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component centrally located at the same time.

[0022] The technical solution of this application will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] refer to Figure 1 This application provides a back-drilling method for printed circuit boards, comprising: S1: Obtain the basic processing information of the circuit board to be processed, construct back drilling processing parameters based on the basic processing information, and obtain segmented processing data corresponding to the circuit board to be processed; In step S1, the basic processing information of the circuit board to be processed is obtained, specifically the collection and measurement of various parameters of the circuit board. The layer structure information of the circuit board includes the thickness, material, and lamination structure of each layer. For example, the structure of the board can be single-layer, double-layer, or multi-layer. The arrangement of conductive and non-conductive layers between each layer determines the overall thickness and structural characteristics of the circuit board. This information can be obtained using CT scanning technology, scanning electron microscopy, or optical measurement systems to accurately determine the thickness and material properties of each layer. Back-drilled hole information includes the location, diameter, and number of each hole. Each hole on the circuit board is located, and the hole position information includes the coordinates and diameter of each back-drilled hole. This data can be obtained from CAD design drawings or extracted in real time by an automated scanning system. After obtaining the layer structure and hole position data, the target processing depth can be determined based on design requirements or circuit board standards, such as signal transmission requirements and electrical performance considerations. To ensure accurate back-drilling depth, the target depth can be set according to the function and conductivity requirements of the back-drilled holes, ensuring that excess copper segments can be effectively removed. Residual hole segment control information refers to the preset maximum residual hole segment range. Exceeding this range may affect electrical performance or even cause short circuits. Based on this fundamental information, back-drilling machining parameters are calculated and analyzed. These parameters mainly include spindle speed, feed rate, single-pass depth, retraction height, and dressing parameters. Spindle speed and feed rate settings are typically adjusted based on the hardness of the circuit board material, hole diameter, and depth requirements to ensure a balance between machining efficiency and hole wall quality. Single-pass depth is generally controlled between 0.05mm and 0.15mm. This value is chosen to maintain efficient drilling while avoiding excessive heat buildup, protecting the drill bit and circuit board surface from damage. The retraction height ensures smooth chip removal when the drill bit exits the hole, preventing blockage. Dressing parameters are settings for fine-tuning the hole wall during machining and are typically used in the final hole dressing stage. These machining parameters are matched with the corresponding back drill holes to generate segmented machining data corresponding to the circuit board to be machined. This data includes detailed information such as drilling depth, tool selection, and machining path for each segment, ensuring that each machining segment can be completed under optimal conditions.

[0024] S2: The target back drilling depth is segmented according to the segmented processing data, and the corresponding drill bit is selected according to the segmentation results to obtain the back drilling tool set corresponding to each segment. In step S2, the target back-drilling depth is segmented based on the segmented machining data. This segmentation is to rationally divide the target back-drilling depth, ensuring that each machining segment can be completed within a short cutting time while maintaining machining accuracy. Based on the circuit board thickness, hole diameter variations, chip removal requirements, and drill bit length limitations, the target back-drilling depth is divided into several continuous machining segments. The depth design of each segment needs to balance cutting heat control, chip removal efficiency, and the effective cutting bit length. Shallower machining segments are located at the front to reduce cutting load and improve positioning accuracy, while deeper segments are located at the rear, requiring drill bits with longer cutting bits to meet the cutting needs at deeper locations. After determining the depth of each machining segment, a drill bit corresponding to each segment is selected. Since the depth of each segment is different, the required drill bit cutting bit length also varies. For shallower segments, selecting a drill bit with a shorter cutting bit length improves drill bit rigidity and cutting accuracy; for deeper segments, selecting a drill bit with a longer cutting bit length ensures smooth cutting of deeper holes while maintaining hole diameter consistency. The selection of drill bits is not only based on the cutting edge length, but also on the material and coating of the drill bit to ensure its wear resistance and high temperature resistance in different processing stages, and to effectively reduce damage to the hole wall.

[0025] S3: Control the back drill bit group to sequentially perform segmented drilling on the circuit board to be processed. After each segment is processed, control the current drill bit to exit the hole to a preset height, and call the drill bit corresponding to the next segment to continue processing, so as to obtain a back drill plate that reaches the target back drill depth. In step S3, the back drill bit assembly is controlled to sequentially perform segmented drilling on the circuit board to be processed. Each drill bit performs drilling within its corresponding segment depth, ensuring that each drill precisely reaches the set depth while maintaining the safety and durability of the drill bit and the circuit board. During drilling, the feed rate, spindle speed, and depth of cut are strictly controlled for each drill bit. The depth of cut can be set from 0.05mm to 0.15mm. This range is optimized based on the material properties of the circuit board and the durability of the drill bit, ensuring efficient drilling while avoiding excessive heat buildup and ensuring hole wall quality. After each segment is completed, the drill bit is completely withdrawn from the hole to a preset height. This preset height is a safe withdrawal height; complete withdrawal is for chip removal and heat dissipation, leaving sufficient space in the hole to remove debris and prevent chip buildup that could cause blockage. After each segment is processed, the drill bit is withdrawn to a set retraction height, allowing the drill bit for the next segment to be scheduled and quickly enter the hole formed by the previous segment for further processing. Once inside the borehole, the drill bit continues drilling according to the depth and machining requirements of the next segment, ensuring that each segment is completed under optimal conditions. This method ensures low cutting resistance in each segment, avoids heat buildup inside the hole, reduces drill bit wear, and effectively improves the stability and accuracy of the entire machining process. The segmented pecking drilling method effectively solves the problems of high temperature buildup and chip removal difficulties caused by prolonged continuous drilling, improving drilling efficiency and ensuring hole wall quality. Tool parameters such as spindle speed, feed rate, and depth of cut can be flexibly adjusted for each segment according to specific machining requirements, optimizing the working environment of each drilling segment, reducing cutting heat generation, and extending drill bit life.

[0026] S4: Perform final hole finishing on the back drill plate to obtain the processed printed circuit board; In step S4, the printed circuit board after back-drilling requires final hole finishing to ensure smooth hole walls, remove any minute residues, and improve the overall quality of the hole walls. The purpose of final hole finishing is to remove any burrs, copper shavings, and other debris that may remain inside and on the hole walls through fine machining, ensuring smoother, cleaner hole walls and reducing the amount of fine copper wire residue. Final hole finishing can be performed using short-stroke reciprocating drilling or high-speed rotary finishing. Short-stroke reciprocating drilling involves the drill bit making small up-and-down movements inside the hole, removing minute burrs and residues from the hole walls and bottom through slight cutting. High-speed rotary finishing involves the drill bit rotating rapidly within the hole at a higher speed to remove minute debris and further clean the hole walls. Both methods can be selected based on processing needs; when high hole wall quality is required, a combination of both methods is used for fine finishing. The finishing step helps improve hole wall quality, effectively removing defects and ensuring the smoothness and precision of the hole walls. Final hole finishing also effectively reduces the potential electrical short-circuit risk caused by copper wire residue. During back drilling, the accumulation of debris can create tiny copper wires inside the holes. These wires are often difficult to detect during electrical testing, but they can pose a risk of short circuits. Final hole finishing can completely remove these tiny copper wires and debris, reducing the risk of short circuits caused by copper residue and thus improving the reliability and safety of the circuit board.

[0027] In one optional embodiment, referring to Table 1, comparative examples were selected for performance testing. In this performance test, the performance of this embodiment (segmented machining method) was compared with that of two prior art technologies (Prior Art 1: single-pass drilling, Prior Art 2: single-drill bit method) under the same test conditions. All compared circuit boards were 5mm thick AI server printed circuit boards, and aspects such as chip removal capability, cutting heat accumulation, and hole wall quality during the drilling process were observed. Uniform test conditions refer to using the same drilling equipment, similar drill bit types, and the same circuit board materials to ensure the comparability of test results. Regarding the feed rate, this embodiment was set to 0.1mm / s, the same as Prior Art 2 (0.1mm / s), but different from Prior Art 1's 0.2mm / s. Higher feed rates may increase cutting heat accumulation during drilling, especially when drilling thicker PCBs, where heat is more difficult to dissipate, easily leading to rough hole walls and accelerated drill bit wear. Lower feed rates help to better control cutting heat and maintain drill bit stability and hole wall smoothness. Therefore, this embodiment and prior art 2 employ a lower feed rate setting to avoid the heat buildup problem in prior art 1. The spindle speed is set to 6000 rpm in this embodiment, which is higher than that of prior art 2 (5500 rpm) and prior art 1 (5000 rpm). A higher spindle speed can improve drilling efficiency, but it also increases cutting heat generation, thus requiring a balance with an appropriate feed rate. Prior art 1, due to its lower speed, may be slightly less efficient in machining, while the higher speed of prior art 2 may lead to greater heat buildup, especially during long-term drilling of deep holes, potentially resulting in poor hole wall quality. By combining a higher speed with an appropriate feed rate, this embodiment can better control cutting heat, ensuring both machining efficiency and hole wall quality. Regarding the single-pass depth of cut, this embodiment is set to 0.1 mm, the same as prior art 2, while prior art 1 is set to 0.15 mm. A larger depth of cut helps improve machining efficiency, but excessive depth of cut can lead to heat buildup and increased drill wear. A relatively small peck depth (e.g., 0.1 mm) helps reduce cutting heat, ensures a smoother hole wall, avoids hole wall roughness, and is suitable for thicker PCBs. Compared with prior art 1, the peck depth of this embodiment is smaller, thus better controlling the hole wall quality. Hole wall smoothness (Ra value) is an important indicator for evaluating the quality of back drilling; the smaller the value, the smoother the hole wall. The hole wall smoothness of this embodiment is 0.5 µm, which is significantly better than prior art 1 (1.2 µm) and prior art 2 (1.5 µm). This embodiment uses a segmented machining method, resulting in a shallower drilling depth in each segment, thereby effectively reducing the accumulation of cutting heat and avoiding problems such as hole wall roughness and micro-copper wire residue.In contrast, the existing technology 1 uses a single drilling method, which easily leads to long drilling time and heat accumulation, resulting in poor hole wall smoothness; while the existing technology 2 uses a single drill bit, which also makes it difficult to effectively control the smoothness of the hole wall.

[0028] In summary, the comparative test results show that this embodiment has significant advantages over existing technologies in terms of hole wall smoothness, chip removal capability, and drill bit life. In the case of segmented machining, the drilling depth of each segment is relatively small, avoiding the problems of heat buildup and poor hole wall quality caused by prolonged drilling. Therefore, this embodiment can effectively improve hole wall smoothness, reduce drill bit wear, and thus improve drilling accuracy and machining stability.

[0029] Table 1: In one embodiment, the step of obtaining the basic processing information of the circuit board to be processed, constructing back-drilling processing parameters based on the basic processing information, and obtaining segmented processing data corresponding to the circuit board to be processed includes: The layer structure information, back drill hole information, target machining depth information, and residual hole segment control information of the circuit board to be processed are obtained to obtain the basic machining information; Calculate the target back-drilling depth corresponding to each back-drilling hole based on the aforementioned processing basic information to obtain depth data; Based on the machining basic information and depth data, the spindle speed, feed rate, single pecking depth, retraction height and dressing parameters are set to obtain the back drilling machining parameters; The back-drilling machining parameters are matched with the corresponding back-drilling holes to generate the segmented machining data.

[0030] In this embodiment, the layer structure information includes the overall thickness of the circuit board, the thickness of each layer, material properties (such as the type and thickness of the copper layer and substrate layer), and the electrical connections between layers. This information can be obtained through X-ray CT scanning or optical 3D scanning technology to ensure the accuracy of the thickness and materials of each layer of the circuit board. Back-drilled hole information includes data such as hole coordinates, hole diameter, and hole number, which can be obtained directly from CAD design files or confirmed through an automated measurement system. Target machining depth information is set according to the electrical performance requirements of the circuit board, determining the final back-drilling depth of each back-drilled hole. The target depth can be set according to the functional requirements and signal transmission requirements of the circuit board. For example, the back-drilling depth of ultra-thin copper segments needs to match signal integrity requirements; therefore, the target depth is usually set according to electrical design specifications. Residual hole segment control information refers to the control of the maximum allowable residual copper segment length for each back-drilled hole in the circuit board design. To avoid the generation of tiny copper wires or other electrical performance problems, residual hole segment control information ensures that the copper segment inside the hole is not too long. Based on this basic information, the target back-drilling depth for each back-drilled hole is calculated. The calculation of the target back-drilling depth needs to consider the layer structure of the circuit board and the specific requirements of the back-drilled holes. For example, when calculating the corresponding back-drilling depth for each layer of the circuit board, the material thickness of each layer and the specific location of the holes need to be considered. The calculated depth ensures that the back-drilling of each hole can reach the predetermined depth, removing excess copper segments. A series of processing parameters are set based on the calculated depth data, such as spindle speed, feed rate, single-pass depth, retraction height, and dressing parameters. These parameters are determined through experimental data and actual processing experience. For example, the spindle speed and feed rate need to be set according to the hardness of the circuit board material, the hole diameter, and the processing depth. For harder materials and deeper holes, the spindle speed may need to be set lower, while the feed rate needs to be moderate to ensure processing stability and avoid excessive heat buildup. The single-pass depth can be set between 0.05mm and 0.15mm. This range is suitable for most standard circuit boards, ensuring cutting efficiency while avoiding excessive heat and guaranteeing the quality of the drill bit and hole wall. The retraction height and dressing parameters are used to ensure smooth withdrawal from the hole after each drilling operation and to allow for necessary hole wall trimming. These back-drilling parameters are matched with the corresponding back-drilled holes to generate segmented machining data for the circuit board to be processed. This data includes the machining depth for each back-drilled hole, the drill bit selection, the machining sequence, and all relevant parameters.

[0031] In another embodiment, the calculation of the target machining depth assumes that the circuit board has a 4-layer structure with a thickness of 5mm, each copper layer being 0.2mm thick and each non-conductive material layer being 1mm thick. The goal is to remove excess copper segments between the 2nd and 3rd layers on the circuit board, but the residual hole segment control information needs to be considered during the removal process, i.e., controlling the maximum residual copper segment length of each back-drilled hole. For example, the layer structure information is: total circuit board thickness 5mm, copper layer thickness 0.2mm per layer (1st and 2nd layers), non-conductive layer thickness 1mm per layer (between the 2nd and 3rd layers); the board layer configuration is: 1st copper layer (0.2mm), 2nd non-conductive layer (1mm), 3rd copper layer (0.2mm), 4th non-conductive layer (1mm). The target back-drilling depth is determined according to the circuit board design requirements, removing excess copper segments between the 2nd and 3rd copper layers. Assuming a target depth of 3mm, it means that the copper segment length to be removed from the area starting from the bottom of the 2nd layer is 3mm. Maintain a minimum residual copper segment in each back-drilled hole. This length is determined by residual segment control information, which is given by the circuit board design requirements. For example, the maximum allowable length of the residual copper segment is 0.2mm. During back-drilling, the target depth should be adjusted based on this residual segment length to avoid completely removing all copper layers from the circuit board. When calculating the target depth, subtract the residual copper segment length (e.g., 0.2mm) from the target depth of 3mm. That is: Target machining depth = Target back-drilling depth - Residual segment control information. According to the above formula, the target machining depth is: Target machining depth = 3mm - 0.2mm = 2.8mm. The target back-drilling depth is adjusted to 2.8mm, and during processing, ensure that the residual copper segment in each back-drilled hole does not exceed 0.2mm. Set the spindle speed, feed rate, single-pass depth, retraction height, and dressing parameters based on the target depth data. These parameters are optimized according to the circuit board material characteristics, target depth, and hole diameter. For a hole with a target depth of 3mm, the spindle speed is generally set to 6000rpm and the feed rate is set to 0.1mm / s. These parameters can be adjusted using experimental data or previous machining experience to ensure stable cutting and reduce heat buildup.

[0032] In one embodiment, the step of obtaining the layer structure information, back drill hole information, target machining depth information, and residual hole segment control information of the circuit board to be processed includes: Obtain the board thickness information, lamination structure information, and conductive layer distribution information of the circuit board to be processed to obtain the layer structure data; Obtain the hole position coordinates, hole diameter and corresponding hole number of each back drill hole to obtain back drill hole data; Based on the conductive layer distribution information and the back drill hole data, the target machining endpoint of each back drill hole is obtained, and the target machining depth information is obtained. Based on the preset residual hole segment range, residual hole segment control information corresponding to each back drill hole is generated.

[0033] In this embodiment, the layer structure information of the circuit board, including the thickness and material properties of each layer, is obtained by scanning or by reading design documents. For example, assuming the circuit board has four layers, where layers 1 and 3 are copper layers, each with a thickness of 0.2 mm, and layers 2 and 4 are non-conductive layers, each with a thickness of 1 mm, for a total thickness of 5 mm. This layer structure information allows understanding of the internal composition of the circuit board and its impact on the back-drilling depth. Back-drilling hole information is then obtained, including the location, diameter, and hole number of each hole. For example, assuming the circuit board has multiple back-drilling holes, the location and dimensions of each hole are clearly marked in the CAD file. The diameter, coordinates, and number of each hole are obtained using an automated measurement system. This data forms the basis for subsequent processing, ensuring precise positioning of each hole. After obtaining the back-drilling hole information, the target processing depth information for each hole is determined. The target depth is determined during circuit board design and is typically set based on electrical or signal integrity requirements. For example, for a circuit board used in an AI server, the target back-drilling depth might be set to 3 mm to remove excess copper stubs. To ensure accurate back-drilling depth, calculations are needed based on the structure and electrical performance requirements of each layer of the circuit board. Residual hole length control information is set according to electrical requirements; each back-drilled hole on the circuit board must retain a certain amount of copper to ensure signal transmission integrity. Therefore, the design typically sets the maximum allowable residual copper length for each back-drilled hole. Assuming the design requires that the residual hole length for each back-drilled hole not exceed 0.2mm, this requirement will be taken into account in the target depth calculation to avoid removing excessive copper. By obtaining the above information, a machining base dataset is generated, and this dataset is used to set the corresponding target depth and machining parameters for each back-drilled hole. The generated segmented machining data includes the target depth of each hole, hole location information, drill parameters, etc.

[0034] In one embodiment, the step of segmenting the target back-drilling depth according to the segmented machining data, selecting the corresponding drill bit according to the segmentation results, and obtaining the back-drilling tool set corresponding to each segment includes: Read the target back drill depth and single pecking amount from the segmented processing data, and divide the target back drill depth into at least two processing segments according to the preset segmentation rules; Based on the depth data of each machining segment, obtain the corresponding tool cutting length range, select multiple drill bits with different cutting lengths from drill bits with the same hole diameter, and match the multiple drill bits with each machining segment. The corresponding drill bits are sorted according to the processing segment sequence to obtain the back drill tool set; The preset segmentation rule is to segment the target back drilling depth according to the target back drilling depth, the single pecking amount, and the cutting edge length of the corresponding machining segment.

[0035] In this embodiment, the target back-drilling depth and single-peck depth are read from the segmented machining data, and the target depth is divided into multiple machining segments according to preset segmentation rules. The division of the target depth is based on factors such as the thickness of the circuit board, the hole diameter, chip removal requirements, and the drill bit length. For example, when the target back-drilling depth is 3mm, it may be divided into 3 depth segments, each approximately 1mm deep, to avoid instability caused by drilling too deep each time. The preset segmentation rules divide the target back-drilling depth according to the depth of each segment, the single-peck depth, and the tool length. For shallower machining segments, a drill bit with a shorter cutting edge is selected to improve the rigidity and drilling accuracy of the drill bit; for deeper machining segments, a drill bit with a longer cutting edge is selected to ensure smooth drilling of deeper holes. The selection of each drill bit considers not only the depth but also the consistency of the hole diameter to ensure that the hole diameter of each segment remains consistent and to avoid uneven hole walls. Once the depth and cutting edge length of each segment are determined, the drill bits are sorted according to the machining sequence to obtain the back drill tool set. The sorting order is determined based on the depth requirements of each segment, with shorter cutting edge bits used for the earlier segments and longer cutting edge bits used for the later segments. This ensures that each segment is completed under optimal conditions, avoiding overheating or excessive wear during the cutting process.

[0036] In one embodiment, the step of obtaining the corresponding tool cutting length range based on the segment depth data of each machining segment, and selecting multiple drill bits with different cutting lengths from drill bits with the same hole diameter, includes: Obtain the segment depth and cumulative depth corresponding to each processing segment to obtain the segment depth sequence; Based on the segmented depth sequence, at least two types of drill bits are determined from the first segment drill bit, the middle segment drill bit, and the last segment drill bit. The drill bit with a shorter cutting edge is set as the preceding machining segment, and the drill bit with a longer cutting edge is set as the following machining segment.

[0037] In this embodiment, the segment depth and cumulative depth of each segment are obtained. The segment depth is set according to the thickness of the circuit board, the hole positions, and electrical design requirements. Each segment depth is typically shallow to better control cutting force and heat accumulation. For example, when the target back-drilling depth is 3mm, it may be divided into 3 segments, each with a depth of 1mm. After completing the first segment, the cumulative depth is 1mm; when entering the second segment, the cumulative depth is 2mm, until the target depth is reached. The drill bit cutting length range corresponding to each segment is determined based on the segment depth sequence. For example, if the initial segment depth is shallow, a drill bit with a shorter cutting length is selected, while if the subsequent segment depth is deeper, a drill bit with a longer cutting length is selected. In this way, the drill bit can better adapt to the cutting requirements of different depths, avoiding wobbling and heat accumulation during the cutting process. The system selects drill bits based on the segmented depth sequence. For example, shorter cutting edges are chosen for the initial machining stage to improve rigidity and drilling accuracy, while longer cutting edges are selected for later stages to ensure smooth drilling of deep holes and reduce drilling resistance. The system can also automatically adjust the selection and sequencing of drill bits based on their cutting edge length range, ensuring that each segment is drilled under optimal conditions. This selection and matching of drill bits with various cutting edge lengths improves drilling efficiency, ensures accurate depth control for each segment, reduces the risk of hole wall damage and drill bit wear, and thus enhances the stability and accuracy of the entire back-drilling process.

[0038] In one embodiment, the step of controlling the back drill bit assembly to sequentially perform segmented drilling on the circuit board to be processed, and controlling the current drill bit to withdraw from the hole to a preset height after each segment is processed, and calling the drill bit corresponding to the next segment to continue processing, includes: The drill bit corresponding to the first processing segment is lowered to the starting position, and the first processing segment is drilled according to the corresponding processing parameters to form the first segment hole; After the first segmented hole is formed, the current drill bit is controlled to retract along the original path to the preset height to obtain the first continuous drilling channel; Call the drill bit corresponding to the next processing segment to enter the first continuous drilling channel, and execute the next segment pecking drill according to the processing parameters corresponding to the next processing segment to form the updated segmented hole; Repeat the retraction and drilling steps until a back drill plate is formed that reaches the target back drill depth.

[0039] In this embodiment, the drill bits corresponding to each segment are selected based on the machining data and installed sequentially into the tool set. Based on the target depth and corresponding machining parameters for each segment, the appropriate drill bit is called for machining. In actual operation, each drill bit needs to descend to the starting position of the target depth and perform the first peck drill. Specifically, the drill bit drills into the circuit board at a set feed rate and spindle speed, completing a portion of the target depth. During this process, the feed rate can be set to approximately 0.1 mm / s, and the spindle speed can be set to 6000 rpm to maintain appropriate cutting force and temperature control. After each peck drill, the drill bit will completely withdraw from the hole along a predetermined path, and the withdrawal height is set to 1.5 times the thickness of the circuit board, for example, 7.5 mm, to ensure that the chips after each drilling can be smoothly discharged, avoiding chip accumulation in the hole. After complete withdrawal, the system will call the drill bit for the next segment and repeat this process until the final target back-drilling depth is achieved. To improve machining efficiency and reduce drill bit wear, the selection of drill bits can be adjusted in a timely manner according to the segment depth. For example, a shorter cutting edge is selected for shallower sections to increase drill bit rigidity and positioning accuracy; a longer cutting edge is selected for deeper sections to ensure stability in deep hole drilling. After each drilling operation, the drill bit retraction ensures sufficient chip removal space, preventing hole clogging. This segmented pecking drilling method allows each section to be drilled under conditions of low cutting heat and low cutting resistance, ensuring improved hole wall quality and avoiding the problems of hole clogging and temperature buildup that may occur in conventional drilling.

[0040] In one embodiment, after the step of lowering the drill bit corresponding to the first machining segment to the starting position, the method further includes: Before the current machining segment begins, the spindle speed and feed rate parameters corresponding to that segment are called, and the current drill bit is controlled to cut downwards to the set segment depth according to the spindle speed and feed rate. After reaching the set segment depth, record the current hole depth data and update the hole depth data to the processing record of the corresponding hole position; The spindle speed, feed rate, and depth parameters for the next machining segment are retrieved based on the machining record to form the drilling command for the next machining segment.

[0041] In this embodiment, after invoking the step of lowering the drill bit to the starting position corresponding to the first machining segment, detailed parameter control is performed according to the machining requirements of each segment. The spindle speed and feed rate of each segment are set according to the specific machining requirements. For example, before the start of each segment, the spindle speed and feed rate parameters for the corresponding segment are invoked to ensure that the drill bit drills under optimal machining conditions. For shallower segments, the spindle speed can be set higher (e.g., 8000 rpm) to improve drilling efficiency; the feed rate is set lower (e.g., 0.1 mm / s) to ensure drilling accuracy and hole wall quality. For deeper segments, the spindle speed can be set lower to reduce the accumulation of cutting heat, while the feed rate is relatively higher to maintain cutting stability and efficiency. During drilling, when the drill bit reaches the preset depth, the current hole depth data is recorded and updated in the machining record. In this way, the drilling progress of each segment can be accurately tracked, ensuring that the depth of each hole can be precisely controlled. Based on these records, after reaching the set depth, the spindle speed, feed rate, and depth parameters of subsequent segments are automatically adjusted to optimize the efficiency and accuracy of subsequent drilling, ensuring stability during back drilling and avoiding situations where the drill bit wears out too quickly or drills too deeply.

[0042] In one embodiment, the step of setting the spindle speed, feed rate, single peck depth, retraction height, and dressing parameters based on the machining foundation information and depth data includes: The range of single-pecking depth is determined based on the plate thickness and lamination structure information in the layer structure data, and the hole diameter information in the back-drilled hole data; wherein, the single-pecking depth is 0.05mm to 0.15mm. Based on the cumulative hole depth change corresponding to the target back drilling depth, the spindle speed and feed rate are set for different machining segments respectively; The reciprocating stroke, number of repairs, and rotation parameters in the final hole finishing are set according to the segment depth corresponding to the final processing segment.

[0043] In this embodiment, the single-peg depth for each drill stroke can be set based on the board thickness and laminated structure information in the layer structure data, and the hole diameter information in the back-drilling data. Assuming a target back-drilling depth of 3mm, the system will set the single-peg depth to 0.1mm. This is because a smaller peck depth reduces the cutting force during each feed and avoids excessive heat buildup, while ensuring that the drill bit and the circuit board surface are not damaged. The spindle speed and feed rate are set based on the material properties of the circuit board and the hole depth. In shallower segments (e.g., 1mm), the feed rate can be set to a higher 0.1mm / s, while the spindle speed can be increased to 6000rpm to increase drilling efficiency. For deeper segments (e.g., 2mm), the feed rate needs to be reduced to 0.05mm / s, and the spindle speed reduced to 4000rpm to ensure stable deep drilling and reduce heat buildup. The retraction height can be set to 1.5 times the circuit board thickness. Assuming a circuit board thickness of 5mm, the retraction height will be set to 7.5mm to ensure the drill bit completely withdraws from the hole after each segment is machined, while providing sufficient space to remove debris and prevent blockage. For finishing, appropriate finishing parameters are set according to the hole wall quality requirements, such as a reciprocating stroke of 0.5mm and a rotational speed of 4000rpm. This helps to smooth the hole wall, ensuring no damage and improving hole wall quality, especially for PCBs requiring high-precision signal transmission. These precise machining parameter settings ensure that each drilling segment is performed under optimal conditions, thereby improving machining efficiency, reducing tool wear, and guaranteeing hole wall smoothness and electrical performance.

[0044] In one embodiment, the step of performing final hole finishing on the back drill plate to obtain the processed printed circuit board includes: The last section of the drill bit is called into the already formed back drill hole, and the last section of the drill bit is controlled to perform short-stroke reciprocating repair to obtain the initial repair hole. After the initial finishing hole is formed, the final drill bit is controlled to rotate and finish to form the final finishing hole, resulting in the processed printed circuit board.

[0045] In this embodiment, the terminal drill bit is controlled to enter the pre-drilled hole and perform short-stroke reciprocating finishing to remove minute burrs from the hole wall and bottom. During this process, the drill bit moves up and down slightly along the hole wall to remove residual impurities and ensure a smoother hole wall. The rotary finishing stage uses a higher-speed drill bit to rotate rapidly within the hole, further removing minute debris and copper wire residue. The purpose of rotary finishing is to ensure a completely smooth hole wall, avoiding any minor defects that could affect electrical performance. After finishing, the hole walls of the processed printed circuit board will meet the electrical and mechanical performance requirements, ensuring the absence of impurities or burrs.

[0046] In one embodiment, the step of obtaining a back drill plate that reaches the target back drill depth includes: After each processing segment is completed, obtain the actual hole depth data for the corresponding processing segment; The actual hole depth data is compared with the set segment depth corresponding to the processing segment to obtain the segment verification result; Based on the segmented verification results, the corresponding drill bits and processing parameters for the subsequent processing segments are called, and the subsequent segmented processing continues; When the actual hole depth reaches the target back drill depth, the back drill plate that has reached the target back drill depth is obtained.

[0047] In this embodiment, after each processing segment is completed, the actual hole depth data of the corresponding processing segment is automatically read and compared with the set segment depth. The comparison process determines whether the processing of each segment has reached the expected target depth. If the error between the actual hole depth and the set segment depth exceeds the allowable range, the system will adjust the processing parameters of subsequent segments to ensure the drilling accuracy of each segment. When the verification is completed and the hole depth is confirmed to have reached the target depth, the system will record the segment verification result and call the drill bit and processing parameters of the subsequent processing segment based on the result. The subsequent segment processing continues until the predetermined back drilling depth is reached, ensuring that the depth of each back drilling hole can be precisely controlled, avoiding over-drilling or insufficient hole depth, thereby improving the stability and accuracy of back drilling processing. When all segments are processed, a back drilling board that has reached the target back drilling depth is output and quality inspection is performed to ensure that the accuracy of each hole position, hole wall quality, and copper wire residue meet the design requirements. Through segment verification and precise control, the entire back drilling processing process can achieve high precision and high quality requirements, ensuring the electrical performance and mechanical stability of the final circuit board.

[0048] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for back-drilling a printed circuit board, characterized in that, include: Obtain the basic processing information of the circuit board to be processed, construct back drilling processing parameters based on the basic processing information, and obtain segmented processing data corresponding to the circuit board to be processed; Based on the segmented processing data, the target back drilling depth is segmented and set. The corresponding drill bit is selected according to the segmentation results to obtain the back drilling tool set corresponding to each segment. The back drill bit assembly is controlled to sequentially drill the circuit board to be processed in segments. After each segment is processed, the current drill bit is controlled to exit the hole to a preset height, and the drill bit corresponding to the next segment is called to continue processing, so as to obtain a back drill board that reaches the target back drill depth. The back drill plate is then finished with final holes to obtain the processed printed circuit board.

2. The back-drilling method for printed circuit boards according to claim 1, characterized in that, The steps of obtaining the basic processing information of the circuit board to be processed, constructing back-drilling processing parameters based on the basic processing information, and obtaining segmented processing data corresponding to the circuit board to be processed include: The layer structure information, back drill hole information, target machining depth information, and residual hole segment control information of the circuit board to be processed are obtained to obtain the basic machining information; Calculate the target back-drilling depth corresponding to each back-drilling hole based on the aforementioned processing basic information to obtain depth data; Based on the machining basic information and depth data, the spindle speed, feed rate, single pecking depth, retraction height and dressing parameters are set to obtain the back drilling machining parameters; The back-drilling machining parameters are matched with the corresponding back-drilling holes to generate the segmented machining data.

3. The back-drilling method for printed circuit boards according to claim 2, characterized in that, The steps of obtaining the layer structure information, back drill hole information, target machining depth information, and residual hole segment control information of the circuit board to be processed include: Obtain the board thickness information, lamination structure information, and conductive layer distribution information of the circuit board to be processed to obtain the layer structure data; Obtain the hole position coordinates, hole diameter and corresponding hole number of each back drill hole to obtain back drill hole data; Based on the conductive layer distribution information and the back drill hole data, the target machining endpoint of each back drill hole is obtained, and the target machining depth information is obtained. Based on the preset residual hole segment range, residual hole segment control information corresponding to each back drill hole is generated.

4. The back-drilling method for printed circuit boards according to claim 1, characterized in that, The steps of segmenting the target back drilling depth according to the segmented machining data, selecting the corresponding drill bit according to the segmentation results, and obtaining the back drilling tool set corresponding to each segment include: Read the target back drill depth and single pecking amount from the segmented processing data, and divide the target back drill depth into at least two processing segments according to the preset segmentation rules; Based on the depth data of each machining segment, obtain the corresponding tool cutting length range, select multiple drill bits with different cutting lengths from drill bits with the same hole diameter, and match the multiple drill bits with each machining segment. The corresponding drill bits are sorted according to the processing segment sequence to obtain the back drill tool set; The preset segmentation rule is to segment the target back drilling depth according to the target back drilling depth, the single pecking amount, and the cutting edge length of the corresponding machining segment.

5. The back-drilling method for printed circuit boards according to claim 4, characterized in that, The step of obtaining the corresponding tool cutting length range based on the segment depth data of each machining segment, and selecting multiple drill bits with different cutting lengths from drill bits with the same hole diameter, includes: Obtain the segment depth and cumulative depth corresponding to each processing segment to obtain the segment depth sequence; Based on the segmented depth sequence, at least two types of drill bits are determined from the first segment drill bit, the middle segment drill bit, and the last segment drill bit. The drill bit with a shorter cutting edge is set as the preceding machining segment, and the drill bit with a longer cutting edge is set as the following machining segment.

6. The back-drilling method for printed circuit boards according to claim 1, characterized in that, The steps of controlling the back drill bit assembly to sequentially drill segments of the circuit board to be processed, and controlling the current drill bit to withdraw from the hole to a preset height after each segment is processed, and calling the drill bit corresponding to the next segment to continue processing, include: The drill bit corresponding to the first processing segment is lowered to the starting position, and the first processing segment is drilled according to the corresponding processing parameters to form the first segment hole; After the first segmented hole is formed, the current drill bit is controlled to retract along the original path to the preset height to obtain the first continuous drilling channel; Call the drill bit corresponding to the next processing segment to enter the first continuous drilling channel, and execute the next segment pecking drill according to the processing parameters corresponding to the next processing segment to form the updated segmented hole; Repeat the retraction and drilling steps until a back drill plate is formed that reaches the target back drill depth.

7. The back-drilling method for printed circuit boards according to claim 6, characterized in that, After the step of lowering the drill bit corresponding to the first machining segment to the starting position, the method further includes: Before the current machining segment begins, the spindle speed and feed rate parameters corresponding to that segment are called, and the current drill bit is controlled to cut downwards to the set segment depth according to the spindle speed and feed rate. After reaching the set segment depth, record the current hole depth data and update the hole depth data to the processing record of the corresponding hole position; The spindle speed, feed rate, and depth parameters for the next machining segment are retrieved based on the machining record to form the drilling command for the next machining segment.

8. The back-drilling method for printed circuit boards according to claim 3, characterized in that, The steps of setting the spindle speed, feed rate, single-pass depth, retraction height, and dressing parameters based on the machining foundation information and depth data include: The range of single-pecking depth is determined based on the plate thickness and lamination structure information in the layer structure data, and the hole diameter information in the back-drilled hole data; wherein, the single-pecking depth is 0.05mm to 0.15mm. Based on the cumulative hole depth change corresponding to the target back drilling depth, the spindle speed and feed rate are set for different machining segments respectively; The reciprocating stroke, number of repairs, and rotation parameters in the final hole finishing are set according to the segment depth corresponding to the final processing segment.

9. The back-drilling method for printed circuit boards according to claim 1, characterized in that, The step of performing final hole finishing on the back drill plate to obtain the processed printed circuit board includes: The last section of the drill bit is called into the already formed back drill hole, and the last section of the drill bit is controlled to perform short-stroke reciprocating repair to obtain the initial repair hole. After the initial finishing hole is formed, the final drill bit is controlled to rotate and finish to form the final finishing hole, resulting in the processed printed circuit board.

10. The back-drilling method for printed circuit boards according to claim 1, characterized in that, The step of obtaining a back drill plate that reaches the target back drill depth includes: After each processing segment is completed, obtain the actual hole depth data for the corresponding processing segment; The actual hole depth data is compared with the set segment depth corresponding to the processing segment to obtain the segment verification result; Based on the segmented verification results, the corresponding drill bits and processing parameters for the subsequent processing segments are called, and the subsequent segmented processing continues; When the actual hole depth reaches the target back drill depth, the back drill plate that has reached the target back drill depth is obtained.

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