Machining method for solving problem that plated-through holes exist in steps of step printed circuit board

Abstract

The invention discloses a processing method for solving the problem that plated-through holes exist in steps of a step printed circuit board, and relates to the field of printed board manufacturing. The processing method for solving the problem that the plated-through hole exists in the step of the step printed circuit board comprises the steps of selecting a depth-controlled milling cutter, designing the depth-controlled depth, performing pretreatment before drilling, performing depth-controlled drilling, performing quality inspection after drilling, completing depth-controlled step milling and performing final quality inspection. According to the processing method for solving the problem that the plated-through hole is formed in the step of the step printed circuit board, the hole wall copper can be prevented from being directly cut by a milling cutter in the subsequent processing process through depth-controlled drilling, so that the hole wall copper is effectively prevented from being cracked and burrs are effectively prevented. And after the depth-controlled drilling is completed, depth-controlled step milling is completed according to a conventional mode. The step ensures accurate machining of the step, and meanwhile damage to hole wall copper is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit board manufacturing, in particular to a processing method for solving the problem of metallized holes in steps of a stepped printed circuit board. Background Art

[0002] In the field of printed circuit board (PCB) manufacturing, stepped PCBs often face numerous challenges due to their unique structural characteristics. The processing of plated holes within the stepped surfaces is particularly problematic. When a plated through hole is designed within a stepped PCB layer and controlled-depth milling is required, the milling cutter's lateral cuts can cause the hole walls to crack and burr. These issues not only impact PCB processing quality but can also adversely affect subsequent device assembly.

[0003] In the prior art, the problem of processing plated holes within steps is typically solved by manually repairing each hole one by one. However, this method is not only inefficient, but the repair results are often unsatisfactory, making it difficult to meet the requirements of high-quality PCB manufacturing. Therefore, this application proposes a method for processing plated holes within steps of stepped printed circuit boards. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention provides a method for processing plated holes within steps of stepped printed circuit boards. This method addresses the conventional problem of manually repairing plated holes one by one in the existing technology. However, this method is not only inefficient, but the repair results are often unsatisfactory, making it difficult to meet the requirements of high-quality PCB manufacturing.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: A processing method for solving the problem of metallized holes in the steps of a stepped printed circuit board, comprising the following steps:

[0006] Step 1: Select a depth-controlled milling cutter. According to the drilling diameter of the metalized hole in the step, select a depth-controlled milling cutter that is at least 0.2mm larger than the diameter.

[0007] Step 2: Design the controlled depth. Based on the actual depth of the step and the factory's processing capacity, the designed controlled depth is the step depth plus 0.1mm. Use vibration suppression technology and conduct dynamic monitoring of the drilling process.

[0008] Step 3: Pre-treat before drilling: clean the step area, remove oil and oxide impurities, and preheat the PCB board;

[0009] Step 4: depth-controlled drilling: Use the selected depth-controlled milling cutter to perform depth-controlled drilling on the metallized hole in the step to form an interlaced area between the milled step and the metallized hole;

[0010] Step 5: Check the quality of the hole after drilling. After drilling is completed, use a microscope or magnifying glass to check the quality of the hole.

[0011] Step 6: Complete the depth-controlled milling step in a conventional manner, and perform stress relief and flattening.

[0012] Step 7: Final quality inspection: After processing is completed, use a microscope, magnifying glass or X-ray detection equipment to conduct a comprehensive inspection of the processing quality.

[0013] Preferably, the preheating temperature in the pretreatment step before drilling is controlled between 50°C and 80°C.

[0014] Preferably, in the depth-controlled drilling step, coolant is used for cooling and lubrication during the drilling process, and the coolant is an environmentally friendly water-soluble cutting fluid.

[0015] Preferably, the post-drilling quality inspection and the final quality inspection include inspection contents of hole wall smoothness, hole diameter consistency, and the presence or absence of burrs or cracks, and the inspection results are recorded.

[0016] Preferably, after completing the step of controlling the depth of the step milling, the edge of the step is chamfered, and the chamfer radius is controlled between 0.1 mm and 0.3 mm.

[0017] Preferably, in the step of selecting a depth-controlled milling cutter, the material of the depth-controlled milling cutter is cemented carbide or diamond, and the cutting edge of the milling cutter is precision-ground.

[0018] Preferably, the dynamic monitoring of the drilling process is specifically as follows:

[0019] S1. Torque and vibration sensor data acquisition: A high-precision torque sensor and vibration sensor are installed simultaneously on the spindle of the CNC drilling machine. The torque sensor monitors the torque changes during the drilling process in real time, while the vibration sensor monitors the vibration conditions during the processing, including vibration acceleration and vibration displacement parameters.

[0020] The sensor transmits the collected analog signal to the A / D conversion module through the data transmission line.

[0021] S2, A / D conversion and signal processing: The A / D conversion module receives the analog signals transmitted by the torque and vibration sensors and converts them into digital signals;

[0022] The converted digital signal undergoes preliminary signal processing, such as filtering and amplification, to improve the signal-to-noise ratio and accuracy.

[0023] S3, PLC control system processing and vibration suppression

[0024] The digital signal is transmitted to the PLC control system, which processes and analyzes the signal. The PLC system has preset reference torque values, threshold values, and vibration limits. By comparing these with the real-time collected torque and vibration data, it determines whether the drilling process is normal. If the vibration exceeds the set limit, the PLC system activates the vibration suppression strategy.

[0025] S4, Edge Computing Module Analysis

[0026] The PLC system transmits the processed data to the edge computing module, which performs more in-depth analysis of the data, such as spectrum analysis, tool life prediction, and vibration source identification.

[0027] Spectral analysis can identify vibration frequency components during the drilling process, helping to determine tool wear, process stability, and vibration sources. Tool life prediction uses an algorithmic model to predict the remaining tool life based on historical and real-time monitoring data. Vibration source identification can help optimize machining parameters or adjust equipment configuration to further reduce vibration.

[0028] S5. Human-machine interface display and operation feedback

[0029] The edge computing module transmits the analysis results to the human-machine interface, which displays torque data, vibration data, machining status, and warning information in real time in the form of graphs and curves. The operator can monitor the machining process through the interface, promptly understand machining status and abnormal conditions, and make operational adjustments or interventions as needed.

[0030] The HMI also provides operational feedback functions, such as confirming warning information, recording processing logs, adjusting processing parameters, and activating or adjusting vibration suppression devices.

[0031] Preferably, the vibration suppression strategy includes the following steps:

[0032] Step 1: Initial Adjustment

[0033] The PLC system first attempts to reduce vibration by adjusting the feed rate. By reducing the feed rate, the cutting force is reduced, thereby reducing the vibration amplitude.

[0034] Step 2: Activate active vibration suppression

[0035] If reducing the feed rate fails to reduce the vibration amplitude, the PLC system will activate an active vibration suppression device, such as an electromagnetic damper or piezoelectric ceramic actuator. The electromagnetic damper or piezoelectric ceramic actuator can dynamically adjust the suppression force based on the real-time monitored vibration signal to offset the processing vibration.

[0036] Preferably, the stress relief and flattening include:

[0037] S1. Workpiece placement: Carefully place the processed workpiece into the working area of ​​the vacuum furnace, ensuring that the workpiece is placed stably and does not touch the furnace wall.

[0038] S2. Parameter setting: According to the process requirements, set the vacuum furnace's heating rate, holding temperature, holding time and vacuum parameters.

[0039] S3. Start heat treatment cycle: After confirming that all parameter settings are correct, start the heat treatment cycle of the vacuum furnace.

[0040] S4. Monitoring process: During the heat treatment process, regularly check the operating status of the vacuum furnace to ensure that parameters such as temperature and vacuum degree remain within the set range.

[0041] S5. Completion inspection: After the heat treatment cycle is completed, wait for the workpiece to cool down to ≤40℃ and then take it out of the furnace. Perform an appearance inspection on the workpiece to confirm that there are no oxidation or deformation defects.

[0042] Preferably, the parameter settings are specifically as follows:

[0043] Warming up stage:

[0044] From room temperature to 80℃, the heating rate is controlled at 3℃ / min to avoid thermal stress in the workpiece due to excessive temperature difference;

[0045] Insulation stage:

[0046] Maintain at 80°C for 30 minutes to make the internal temperature of the workpiece uniform and start initial stress relief;

[0047] The vacuum degree was maintained at 5×10 -3 Pa, ensures that the workpiece is heat treated in a non-oxidizing environment;

[0048] Secondary heating:

[0049] The temperature was raised from 80°C to 120°C at a rate of 2°C / min to further promote stress release;

[0050] Final insulation:

[0051] Keep at 120℃ for 15 minutes to fully eliminate the internal stress of the workpiece;

[0052] The vacuum degree is increased to ≤1×10-2Pa to ensure the heat treatment effect.

[0053] The present invention discloses a processing method for solving the problem of metallized holes in the steps of a stepped printed circuit board, which has the following beneficial effects:

[0054] This method for processing metallized holes within stepped PCBs uses controlled-depth drilling to prevent the milling cutter from directly cutting the copper in the hole wall during subsequent processing, effectively preventing cracking and burrs in the copper wall. After completing controlled-depth drilling, controlled-depth milling of the step is performed conventionally. This step ensures precise machining of the step while avoiding damage to the copper in the hole wall.

[0055] 2. This method solves the problem of metallized holes in the steps of the printed circuit board. It is to select a depth-controlled milling cutter that is at least 0.2mm larger than the overall diameter of the metallized hole drilling tool in the step. This choice ensures that the milling cutter has sufficient margin during the processing and avoids direct cutting of the copper in the hole wall. The controlled depth is at least 0.1mm deeper than the step depth, and the specific depth can be determined according to the actual factory capacity. This design ensures that the milling cutter can completely penetrate the useless material during the processing process to form a stable staggered area. First, perform controlled depth drilling on the metallized hole in the step before the depth-controlled milling step. The purpose of this step is to first remove the useless material above the metallized hole in the step to form an staggered area between the milling step and the metallized hole.

[0056] 3. This method for processing plated holes within stepped PCBs involves removing oil and oxides during pre-drilling to prevent debris and contamination of the hole walls and poor conductivity. This reduces heat conduction barriers and improves process consistency. Preheating to 50-80°C also reduces internal stress in the board, minimizing deformation or cracking caused by temperature differences during drilling. This softens the board surface, improving cutter penetration and reducing the risk of tool breakage.

[0057] 4. This method for processing metallized holes within stepped PCBs utilizes chamfering to eliminate stress concentration at the step edges, reducing the risk of microcracks. This improves PCB fatigue resistance and extends service life. The milling cutter, made of carbide / diamond, is heat-resistant and wear-resistant, making it suitable for high-speed machining. Precision-ground cutting edges reduce cutting resistance and improve hole wall verticality.

[0058] 5. This method for processing metallized holes within stepped PCBs utilizes torque and vibration sensors to collect real-time torque and vibration data during the drilling process, ensuring that feed rate and cutting depth remain within safe ranges. Vibration frequency and amplitude are monitored to identify potential issues such as tool wear, spindle imbalance, or machine tool resonance. Dynamic adjustments are made to reduce feed rate and optimize cutting parameters to avoid hole tearing, tool breakage, or workpiece deformation caused by torque overload or excessive vibration. Electromagnetic dampers or piezoelectric ceramic actuators are used to actively offset machining vibrations, improving surface quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0060] Figure 1 It is a schematic diagram of the process of the present invention;

[0061] Figure 2 Schematic diagram of using a CNC milling cutter to complete PCB steps in the prior art of the present invention;

[0062] Figure 3 This is a schematic diagram of the dynamic monitoring process of the drilling process of the present invention;

[0063] Figure 4 This is a flow chart of the vibration suppression strategy of the present invention;

[0064] Figure 5 Schematic diagram of the stress relief and flattening process of the present invention;

[0065] Figure 6 Schematic diagram of the parameter setting process of the present invention. DETAILED DESCRIPTION

[0066] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0067] The present invention provides a method for processing plated holes within steps of a stepped printed circuit board. This method addresses the conventional problem of manually repairing plated holes within steps, typically using a method that repairs each hole individually. However, this method is not only inefficient, but also often produces unsatisfactory repair results, making it difficult to meet the requirements of high-quality PCB manufacturing.

[0068] Select a depth-controlled milling cutter that is at least 0.2mm larger than the overall diameter of the metallized hole drilled in the step. This choice ensures that the milling cutter has sufficient margin during the processing process and avoids direct cutting of the copper in the hole wall. The controlled depth is at least 0.1mm deeper than the step depth, and the specific depth can be determined according to the actual factory capacity. This design ensures that the milling cutter can completely penetrate the useless material during the processing process to form a stable staggered area. First, perform controlled depth drilling on the metallized hole in the step before depth-controlled milling. The purpose of this step is to first remove the useless material above the metallized hole in the step to form an staggered area between the milling step and the metallized hole. Through depth-controlled drilling, the milling cutter can be prevented from directly cutting the copper in the hole wall during subsequent processing, thereby effectively preventing the copper in the hole wall from cracking and burrs. After completing the controlled depth drilling, the controlled depth milling step is completed in the conventional manner. This step ensures the precise processing of the step while avoiding damage to the copper in the hole wall.

[0069] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0070] The embodiment of the present invention discloses a processing method for solving the problem of metallized holes in steps of a stepped printed circuit board.

[0071] According to the attached Figure 1 As shown in FIG. 6 , a processing method for solving the problem of metallized holes in the steps of a stepped printed circuit board includes the following steps:

[0072] Step 1: Select a depth-controlled milling cutter. According to the drilling diameter of the metalized hole in the step, select a depth-controlled milling cutter that is at least 0.2mm larger than the diameter.

[0073] Step 2: Design the controlled depth. Based on the actual depth of the step and the factory's processing capacity, the designed controlled depth is the step depth plus 0.1mm. Use vibration suppression technology and conduct dynamic monitoring of the drilling process.

[0074] Step 3: Pre-treat before drilling: clean the step area, remove oil and oxide impurities, and preheat the PCB board;

[0075] Step 4: depth-controlled drilling: Use the selected depth-controlled milling cutter to perform depth-controlled drilling on the metallized hole in the step to form an interlaced area between the milled step and the metallized hole;

[0076] Step 5: Check the quality of the hole after drilling. After drilling is completed, use a microscope or magnifying glass to check the quality of the hole.

[0077] Step 6: Complete the depth-controlled milling step in a conventional manner, and perform stress relief and flattening.

[0078] Step 7: Final quality inspection: After processing is completed, use a microscope, magnifying glass or X-ray detection equipment to conduct a comprehensive inspection of the processing quality.

[0079] Furthermore, the preheating temperature in the pretreatment step before drilling is controlled between 50°C and 80°C.

[0080] Furthermore, in the depth-controlled drilling step, coolant is used for cooling and lubrication during the drilling process, and the coolant is an environmentally friendly water-soluble cutting fluid.

[0081] Furthermore, the post-drilling quality inspection and final quality inspection include inspection contents such as hole wall smoothness, hole diameter consistency, and the presence or absence of burrs or cracks, and the inspection results are recorded.

[0082] Furthermore, after the step of controlling the depth of the step is completed, the edge of the step is chamfered, and the chamfer radius is controlled between 0.1 mm and 0.3 mm.

[0083] Furthermore, in the step of selecting the depth-controlled milling cutter, the material of the depth-controlled milling cutter is cemented carbide or diamond, and the cutting edge of the milling cutter is precision-ground.

[0084] Select a depth-controlled milling cutter that is at least 0.2mm larger than the overall diameter of the metallized hole drilled in the step. This choice ensures that the milling cutter has sufficient margin during the processing process and avoids direct cutting of the copper in the hole wall. The controlled depth is at least 0.1mm deeper than the step depth, and the specific depth can be determined according to the actual factory capacity. This design ensures that the milling cutter can completely penetrate the useless material during the processing process to form a stable staggered area. First, perform controlled depth drilling on the metallized hole in the step before depth-controlled milling. The purpose of this step is to first remove the useless material above the metallized hole in the step to form an staggered area between the milling step and the metallized hole. Through depth-controlled drilling, the milling cutter can be prevented from directly cutting the copper in the hole wall during subsequent processing, thereby effectively preventing the copper in the hole wall from cracking and burrs. After completing the controlled depth drilling, the controlled depth milling step is completed in the conventional manner. This step ensures the precise processing of the step while avoiding damage to the copper in the hole wall.

[0085] Specifically disclosed, the dynamic monitoring of the drilling process is specifically as follows:

[0086] S1. Torque and vibration sensor data acquisition: A high-precision torque sensor and vibration sensor are installed simultaneously on the spindle of the CNC drilling machine. The torque sensor monitors the torque changes during the drilling process in real time, while the vibration sensor monitors the vibration conditions during the processing, including vibration acceleration and vibration displacement parameters.

[0087] The sensor transmits the collected analog signal to the A / D conversion module through the data transmission line.

[0088] The torque sensor utilizes a non-contact type, offering high precision, high sensitivity, and long life. Full-scale accuracy is ±0.5% FS, ensuring accurate torque data. Mounted on the CNC drilling machine spindle, it connects directly to the tool, providing real-time feedback on tool force. The analog signal is transmitted to the A / D converter module via wired or wireless communication.

[0089] Vibration sensors utilize accelerometers or displacement sensors, offering high precision, high sensitivity, and wideband response. They are installed on the spindle or tool of a CNC drilling machine to accurately monitor vibration during machining. The analog signal is transmitted to an A / D converter module via wired or wireless communication.

[0090] S2, A / D conversion and signal processing: The A / D conversion module receives the analog signals transmitted by the torque and vibration sensors and converts them into digital signals;

[0091] The converted digital signal undergoes preliminary signal processing, such as filtering and amplification, to improve the signal-to-noise ratio and accuracy.

[0092] The A / D converter module features a 24-bit Σ-Δ converter, ensuring high-precision conversion from analog to digital signals. Its sampling frequency is 10kHz, meeting the requirements for high-speed, high-precision data acquisition. A built-in anti-aliasing filter effectively filters out high-frequency noise, improving signal quality.

[0093] S3, PLC control system processing and vibration suppression

[0094] The digital signal is transmitted to the PLC control system, which processes and analyzes the signal. The PLC system has preset reference torque values, threshold values, and vibration limits. By comparing these with the real-time collected torque and vibration data, it determines whether the drilling process is normal. If the vibration exceeds the set limit, the PLC system activates the vibration suppression strategy.

[0095] PLC control system:

[0096] The processing logic utilizes a dual-threshold comparison algorithm, with warning and emergency thresholds defined to achieve graded early warning and control. Thresholds are set based on the material and process requirements, with baseline torque values ​​and thresholds determined through experimentation or experience. Based on the comparison results, the control system generates corresponding control instructions, such as adjusting feed rate, pausing drilling, and retracting the tool, ensuring process stability and reliability.

[0097] S4, Edge Computing Module Analysis

[0098] The PLC system transmits the processed data to the edge computing module, which performs more in-depth analysis of the data, such as spectrum analysis, tool life prediction, and vibration source identification.

[0099] Spectral analysis can identify vibration frequency components during the drilling process, helping to determine tool wear, process stability, and vibration sources. Tool life prediction uses an algorithmic model to predict the remaining tool life based on historical and real-time monitoring data. Vibration source identification can help optimize machining parameters or adjust equipment configuration to further reduce vibration.

[0100] The data analysis algorithm uses a fast Fourier transform spectrum analysis algorithm to identify vibration frequency components during the drilling process. Tool life prediction is based on historical data and real-time monitoring data, using a machine learning algorithm to build a tool life prediction model. Data interaction is carried out via industrial Ethernet or fieldbus with the PLC control system and human-machine interface.

[0101] S5. Human-machine interface display and operation feedback

[0102] The edge computing module transmits the analysis results to the human-machine interface, which displays torque data, vibration data, machining status, and warning information in real time in the form of graphs and curves. The operator can monitor the machining process through the interface, promptly understand machining status and abnormal conditions, and make operational adjustments or interventions as needed.

[0103] The HMI also provides operational feedback functions, such as confirming warning information, recording processing logs, adjusting processing parameters, and activating or adjusting vibration suppression devices.

[0104] The human-machine interface displays torque data, machining status, and warning information in real time, using intuitive graphics and curves. Touchscreen or keypad operation facilitates operator monitoring, adjustment, and intervention. A machining log, including machining time, parameters, and warning information, is recorded to support quality traceability and process optimization.

[0105] Specifically disclosed, the vibration suppression strategy includes the following steps:

[0106] Step 1: Initial Adjustment

[0107] The PLC system first attempts to reduce vibration by adjusting the feed rate. By reducing the feed rate, the cutting force is reduced, thereby reducing the vibration amplitude.

[0108] Step 2: Activate active vibration suppression

[0109] If reducing the feed rate fails to reduce the vibration amplitude, the PLC system will activate an active vibration suppression device, such as an electromagnetic damper or piezoelectric ceramic actuator. The electromagnetic damper or piezoelectric ceramic actuator can dynamically adjust the suppression force based on the real-time monitored vibration signal to offset the processing vibration.

[0110] Torque and vibration sensors collect real-time torque and vibration data during the drilling process, ensuring feed rates and cutting depths remain within safe ranges. Vibration frequency and amplitude are monitored to identify potential issues such as tool wear, spindle imbalance, or machine resonance. Feed rates are dynamically adjusted to reduce feed rates and optimize cutting parameters to avoid hole tearing, tool breakage, or workpiece deformation caused by torque overload or excessive vibration. Electromagnetic dampers or piezoelectric ceramic actuators are used to actively offset machining vibrations, improving surface quality.

[0111] Real-time monitoring of torque changes can predict tool wear trends and avoid unplanned downtime caused by excessive tool wear. Optimizing cutting parameters and vibration suppression reduces dynamic loads on the tool, extending tool life. A closed-loop control system automatically adjusts machining parameters, reducing manual intervention, shortening machining cycles, and lowering scrap rates due to machining defects, thereby improving production yields.

[0112] Specifically disclosed, the stress relief and flattening include:

[0113] S1. Workpiece placement: Carefully place the processed workpiece into the working area of ​​the vacuum furnace, ensuring that the workpiece is placed stably and does not touch the furnace wall.

[0114] S2. Parameter setting: According to the process requirements, set the vacuum furnace's heating rate, holding temperature, holding time and vacuum parameters.

[0115] S3. Start heat treatment cycle: After confirming that all parameter settings are correct, start the heat treatment cycle of the vacuum furnace.

[0116] S4. Monitoring process: During the heat treatment process, regularly check the operating status of the vacuum furnace to ensure that parameters such as temperature and vacuum degree remain within the set range.

[0117] S5. Completion inspection: After the heat treatment cycle is completed, wait for the workpiece to cool down to ≤40℃ and then take it out of the furnace. Perform an appearance inspection on the workpiece to confirm that there are no oxidation or deformation defects.

[0118] Specifically disclosed, the parameter settings are:

[0119] Warming up stage:

[0120] From room temperature to 80℃, the heating rate is controlled at 3℃ / min to avoid thermal stress in the workpiece due to excessive temperature difference;

[0121] Insulation stage:

[0122] Maintain at 80°C for 30 minutes to make the internal temperature of the workpiece uniform and start initial stress relief;

[0123] The vacuum degree is maintained at 5×10-3Pa, ensuring that the workpiece is heat treated in a non-oxidizing environment;

[0124] Secondary heating:

[0125] The temperature was raised from 80°C to 120°C at a rate of 2°C / min to further promote stress release;

[0126] Final insulation:

[0127] Keep at 120℃ for 15 minutes to fully eliminate the internal stress of the workpiece;

[0128] The vacuum degree is increased to ≤1×10-2Pa to ensure the heat treatment effect.

[0129] The vacuum heat treatment equipment uses a vertical vacuum furnace, which must have the following key features:

[0130] Working area size: Φ300mm×400mm, to ensure that it can accommodate the processed workpiece.

[0131] Temperature uniformity: ±3°C, ensuring that the workpiece is heated evenly during the heat treatment process.

[0132] Vacuum degree: A vacuum environment of 5×10-3Pa to 1×10-2Pa can be maintained to prevent the workpiece from oxidation.

[0133] Vacuum heat treatment evenly releases internal stress in the workpiece, preventing deformation or cracking caused by stress concentration. The vacuum environment prevents oxidation and ensures surface quality. After heat treatment, the workpiece is cooled in the furnace to ≤40°C to minimize the impact of thermal stress on flatness. Flatness testing ensures that the workpiece meets high-precision assembly requirements. After stress relief, workpiece deformation during subsequent processing or use is reduced by over 50%, improving product consistency.

[0134] Select a depth-controlled milling cutter that is at least 0.2mm larger than the overall diameter of the metallized hole drilled in the step. This choice ensures that the milling cutter has sufficient margin during the processing process and avoids direct cutting of the copper in the hole wall. The controlled depth is at least 0.1mm deeper than the step depth, and the specific depth can be determined according to the actual factory capacity. This design ensures that the milling cutter can completely penetrate the useless material during the processing process to form a stable staggered area. First, perform controlled depth drilling on the metallized hole in the step before depth-controlled milling. The purpose of this step is to first remove the useless material above the metallized hole in the step to form an staggered area between the milling step and the metallized hole. Through depth-controlled drilling, the milling cutter can be prevented from directly cutting the copper in the hole wall during subsequent processing, thereby effectively preventing the copper in the hole wall from cracking and burrs. After completing the controlled depth drilling, the controlled depth milling step is completed in the conventional manner. This step ensures the precise processing of the step while avoiding damage to the copper in the hole wall.

[0135] Torque and vibration sensors collect real-time torque and vibration data during the drilling process, ensuring feed rates and cutting depths remain within safe ranges. Vibration frequency and amplitude are monitored to identify potential issues such as tool wear, spindle imbalance, or machine resonance. Feed rates are dynamically adjusted to reduce feed rates and optimize cutting parameters to avoid hole tearing, tool breakage, or workpiece deformation caused by torque overload or excessive vibration. Electromagnetic dampers or piezoelectric ceramic actuators are used to actively offset machining vibrations, improving surface quality.

[0136] Real-time monitoring of torque changes can predict tool wear trends and avoid unplanned downtime caused by excessive tool wear. Optimizing cutting parameters and vibration suppression reduces dynamic loads on the tool, extending tool life. A closed-loop control system automatically adjusts machining parameters, reducing manual intervention, shortening machining cycles, and lowering scrap rates due to machining defects, thereby improving production yields.

[0137] Vacuum heat treatment evenly releases internal stress in the workpiece, preventing deformation or cracking caused by stress concentration. The vacuum environment prevents oxidation and ensures surface quality. After heat treatment, the workpiece is cooled in the furnace to ≤40°C to minimize the impact of thermal stress on flatness. Flatness testing ensures that the workpiece meets high-precision assembly requirements. After stress relief, workpiece deformation during subsequent processing or use is reduced by over 50%, improving product consistency.

[0138] Example 1: specifically comprising the following steps:

[0139] S1. Select the depth-controlled milling cutter:

[0140] According to the 0.3mm drilling tool diameter of the metalized hole in the step, a depth-controlled milling cutter that is 0.25mm larger than it is selected, that is, the milling cutter diameter is 0.55mm.

[0141] S2. Design control depth:

[0142] The actual depth of the step is 1.0mm, and the designed controlled depth is the step depth plus 0.15mm, that is, the controlled depth is 1.15mm.

[0143] S3. Pre-treatment before drilling:

[0144] Clean the step area to remove oil, oxide and other impurities. Preheat the PCB board to 60°C.

[0145] S4, depth-controlled drilling:

[0146] Using the selected depth-controlled milling cutter, the plated-on hole within the step is depth-controlled drilled at 5,000 rpm. Environmentally friendly, water-soluble cutting fluid is used for cooling and lubrication during the drilling process. The drilling depth is strictly controlled to 1.15 mm.

[0147] S5. Quality inspection after drilling:

[0148] After drilling is completed, use a microscope to check the drilling quality to confirm that the hole wall is smooth and undamaged.

[0149] S6. Complete the depth-controlled milling step:

[0150] The controlled depth milling step was completed in the conventional manner, with a milling speed of 1000 mm per minute and a feed rate of 0.05 mm / tooth.

[0151] S7, Final Quality Inspection:

[0152] After processing is completed, X-ray inspection equipment is used to conduct a final quality inspection of the steps and metallized holes to confirm that they meet the design requirements. The edges of the steps are chamfered with a chamfer radius of 0.2mm.

[0153] Example 2: specifically comprising the following steps:

[0154] S1. Select the depth-controlled milling cutter:

[0155] According to the 0.4mm drilling tool diameter of the metalized hole in the step, a depth-controlled milling cutter that is 0.3mm larger than it is selected, that is, the milling cutter diameter is 0.7mm.

[0156] S2. Design control depth:

[0157] The actual depth of the step is 1.2mm, and the designed controlled depth is the step depth plus 0.2mm, that is, the controlled depth is 1.4mm.

[0158] S3. Pre-treatment before drilling:

[0159] Clean the step area to remove oil, oxide and other impurities. Preheat the PCB board to 70°C.

[0160] S4, depth-controlled drilling:

[0161] Using the selected depth-controlled milling cutter, the plated-through hole within the step is depth-controlled drilled at 6,000 rpm. Environmentally friendly, water-soluble cutting fluid is used for cooling and lubrication, and vibration suppression technology is employed to reduce vibration and noise during drilling. The drilling depth is strictly controlled to 1.4 mm.

[0162] S5. Quality inspection after drilling:

[0163] After drilling is completed, use a magnifying glass to check the drilling quality to confirm that the hole wall is smooth and undamaged.

[0164] S6. Complete the depth-controlled milling step:

[0165] The controlled depth milling step was completed in the conventional manner, with a milling speed of 1200 mm per minute and a feed rate of 0.06 mm / tooth.

[0166] S7, Final Quality Inspection:

[0167] After processing is completed, the steps and metallized holes are inspected for final quality using a microscope to confirm that they meet the design requirements. The steps are chamfered with a radius of 0.3mm.

[0168] Example 3: specifically comprising the following steps:

[0169] S1. Select the depth-controlled milling cutter:

[0170] According to the drilling tool diameter of 0.25mm for the metallized hole in the step, a depth-controlled milling cutter 0.2mm larger than it is selected, that is, the milling cutter diameter is 0.45mm.

[0171] S2. Design control depth:

[0172] The actual depth of the step is 0.8mm, and the designed controlled depth is the step depth plus 0.1mm, that is, the controlled depth is 0.9mm.

[0173] S3. Pre-treatment before drilling:

[0174] Clean the step area to remove oil, oxide and other impurities. Preheat the PCB board to 50°C.

[0175] S4, depth-controlled drilling:

[0176] Using the selected depth-controlled milling cutter, the plated-on hole within the step is depth-controlled drilled at 4,000 rpm. Environmentally friendly, water-soluble cutting fluid is used for cooling and lubrication during the drilling process. The drilling depth is strictly controlled to 0.9 mm.

[0177] S5. Quality inspection after drilling:

[0178] After drilling is completed, use a microscope to check the drilling quality to confirm that the hole wall is smooth and undamaged.

[0179] S6. Complete the depth-controlled milling step:

[0180] The controlled depth milling step was completed in the conventional manner, with a milling speed of 800 mm per minute and a feed rate of 0.04 mm / tooth.

[0181] S7, Final Quality Inspection:

[0182] After processing is completed, X-ray inspection equipment is used to conduct a final quality inspection of the steps and metallized holes to confirm that they meet the design requirements. The edges of the steps are chamfered with a chamfer radius of 0.1mm.

[0183] According to the above embodiment, a depth-controlled milling cutter that is more than 0.2 mm larger than the overall diameter of the metallized hole drilled in the step is selected. This choice ensures that the milling cutter has sufficient margin during the processing and avoids direct cutting of the copper in the hole wall. The controlled depth is at least 0.1 mm deeper than the step depth, and the specific depth can be determined according to the actual factory capacity. This design ensures that the milling cutter can completely penetrate the useless material during the processing and form a stable interlaced area. First, the metallized hole in the step before the controlled depth milling step is depth-controlled drilled. The purpose of this step is to first remove the useless material above the metallized hole in the step to form an interlaced area between the milling step and the metallized hole. Through controlled depth drilling, the milling cutter can be prevented from directly cutting the copper in the hole wall during subsequent processing, thereby effectively preventing the copper in the hole wall from cracking and burrs. After completing the controlled depth drilling, the controlled depth milling step is completed in a conventional manner. This step ensures the precise processing of the step while avoiding damage to the copper in the hole wall.

[0184] This effectively solves the problem of machining metallized holes within the steps of stepped printed circuit boards, improving machining quality and efficiency. Furthermore, the introduction of cooling and lubrication measures and vibration suppression technology further enhances the stability and reliability of the machining process.

[0185] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A processing method for solving the problem of metallized holes in the steps of a stepped printed circuit board, characterized in that: The following steps are involved: Step 1: Select a depth-controlled milling cutter. According to the drilling diameter of the metalized hole in the step, select a depth-controlled milling cutter that is at least 0.2mm larger than the diameter. Step 2: Design the controlled depth. Based on the actual depth of the step and the factory's processing capacity, the designed controlled depth is the step depth plus 0.1mm. Use vibration suppression technology and conduct dynamic monitoring of the drilling process. Step 3: Pre-treat before drilling: clean the step area, remove oil and oxide impurities, and preheat the PCB board; Step 4: depth-controlled drilling: Use the selected depth-controlled milling cutter to perform depth-controlled drilling on the metallized hole in the step to form an interlaced area between the milled step and the metallized hole; Step 5: Check the quality of the hole after drilling. After drilling is completed, use a microscope or magnifying glass to check the quality of the hole. Step 6: Complete the depth-controlled milling step in a conventional manner, and perform stress relief and flattening. Step 7: Final quality inspection: After processing is completed, use a microscope, magnifying glass or X-ray detection equipment to conduct a comprehensive inspection of the processing quality.

2. A processing method for solving the problem of metallized holes in the steps of a stepped printed circuit board according to claim 1, characterized in that: The preheating temperature in the pretreatment step before drilling is controlled between 50° C. and 80° C.

3. A processing method for solving the problem of metallized holes in the steps of a stepped printed circuit board according to claim 1, characterized in that: In the depth-controlled drilling step, coolant is used for cooling and lubrication during the drilling process, and the coolant is an environmentally friendly water-soluble cutting fluid.

4. A processing method for solving the problem of metallized holes in the steps of a stepped printed circuit board according to claim 1, characterized in that: The post-drilling quality inspection and final quality inspection shall include the smoothness of the hole wall, the consistency of the hole diameter, and the presence of burrs or cracks, and the inspection results shall be recorded.

5. The method for processing a stepped printed circuit board with metallized holes in the steps according to claim 1, characterized in that: After the step of controlling the depth of the step is completed, the edge of the step is chamfered, and the chamfer radius is controlled between 0.1 mm and 0.3 mm.

6. A processing method for solving the problem of metallized holes in the steps of a stepped printed circuit board according to claim 5, characterized in that: In the step of selecting the depth control milling cutter, the material of the depth control milling cutter is cemented carbide or diamond, and the cutting edge of the milling cutter is processed by precision grinding.

7. A processing method for solving the problem of metallized holes in the steps of a stepped printed circuit board according to claim 1, characterized in that: The dynamic monitoring of the drilling process is specifically as follows: S1. Torque and vibration sensor data acquisition: A high-precision torque sensor and vibration sensor are installed simultaneously on the spindle of the CNC drilling machine. The torque sensor monitors the torque changes during the drilling process in real time, while the vibration sensor monitors the vibration conditions during the processing, including vibration acceleration and vibration displacement parameters. S2, A / D conversion and signal processing: The A / D conversion module receives the analog signals transmitted by the torque and vibration sensors and converts them into digital signals; S3, PLC control system processing and vibration suppression The digital signal is transmitted to the PLC control system, which processes and analyzes the signal. The PLC system has preset reference torque values, threshold values, and vibration limits. By comparing these with the real-time collected torque and vibration data, it determines whether the drilling process is normal. If the vibration exceeds the set limit, the PLC system activates the vibration suppression strategy. S4, Edge Computing Module Analysis The PLC system transmits the processed data to the edge computing module, which performs more in-depth analysis on the data, such as spectrum analysis, tool life prediction, and vibration source identification. S5. Human-machine interface display and operation feedback The edge computing module transmits the analysis results to the human-machine interface, which displays torque data, vibration data, processing status, and early warning information in real time in the form of graphics and curves. Operators can monitor the processing process through the human-machine interface, promptly understand the processing status and abnormal conditions, and make operational adjustments or interventions as needed.

8. The method for processing a stepped printed circuit board with metallized holes in the steps according to claim 1, characterized in that: The vibration suppression strategy includes the following steps: Step 1: Initial Adjustment The PLC system first attempts to reduce vibration by adjusting the feed rate. By reducing the feed rate, the cutting force is reduced, thereby reducing the vibration amplitude. Step 2: Activate active vibration suppression If reducing the feed rate fails to reduce the vibration amplitude, the PLC system will activate an active vibration suppression device, such as an electromagnetic damper or piezoelectric ceramic actuator. The electromagnetic damper or piezoelectric ceramic actuator can dynamically adjust the suppression force based on the real-time monitored vibration signal to offset the processing vibration.

9. A processing method for solving the problem of metallized holes in the steps of a stepped printed circuit board according to claim 1, characterized in that: The stress relief and flattening process specifically includes: S1. Workpiece placement: Carefully place the processed workpiece into the working area of ​​the vacuum furnace, ensuring that the workpiece is placed stably and does not touch the furnace wall; S2. Parameter setting: according to the process requirements, set the vacuum furnace heating rate, holding temperature, holding time and vacuum parameters; S3. Start heat treatment cycle: After confirming that all parameter settings are correct, start the heat treatment cycle of the vacuum furnace; S4. Monitoring process: During the heat treatment process, regularly check the operating status of the vacuum furnace to ensure that parameters such as temperature and vacuum degree remain within the set range; S5. Completion inspection: After the heat treatment cycle is completed, wait for the workpiece to cool down to ≤40℃ and then take it out of the furnace. Perform an appearance inspection on the workpiece to confirm that there are no oxidation or deformation defects.

10. A processing method for solving the problem of metallized holes in the steps of a stepped printed circuit board according to claim 9, characterized in that: The parameter settings are specifically as follows: Warming up stage: From room temperature to 80℃, the heating rate is controlled at 3℃ / min; Insulation stage: Maintain at 80°C for 30 minutes to make the internal temperature of the workpiece uniform and start initial stress relief; The vacuum degree was maintained at 5×10 -3 Pa, so that the workpiece is heat treated in a non-oxidizing environment; Secondary heating: From 80℃ to 120℃, the heating rate is controlled at 2℃ / min; Final insulation: Keep at 120℃ for 15 minutes; The vacuum degree is increased to ≤1×10-2Pa.

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