Method for measuring board thickness through back drilling in PCB processing

Abstract

The invention relates to the technical field of PCB (printed circuit board) back drilling processing, and discloses a method for measuring board thickness by back drilling in PCB processing, which comprises the following operation steps of: manufacturing an inner-layer circuit and laminating a multilayer board, manufacturing the inner-layer circuit on a PCB, and combining the inner-layer circuit board with materials such as a copper foil and a prepreg into the multilayer board through a laminating process; drilling and thickness measurement preparation: drilling required through holes and back drilling hole positions on the multilayer board, preparing a thickness measurement drawing and a thickness measurement program, dividing square grids on the drawing according to a certain density, marking the positions and diameters of all back drilling holes, through holes and identification holes, and preparing the thickness measurement program corresponding to the drawing. The program contains alignment hole coordinates and grid coordinates and is used for guiding the operation of the automatic thickness measuring equipment. The method for measuring the board thickness through the back drill in the PCB processing aims at achieving program automation, the number of measuring point positions can be flexibly selected according to actual requirements, and the processing efficiency and accuracy are remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of PCB back drilling processing, and in particular to a method for measuring board thickness by back drilling during PCB processing. Background Art

[0002] PCB back drilling is a high-precision circuit board processing technology, which is mainly used to create tiny channels running through different layers in multi-layer circuit boards. This technology makes the connection inside the circuit board more flexible and efficient by precisely controlling the drilling depth and position. PCB back drilling technology is widely used in electronic products that require high-density interconnection and complex circuit structures, such as smart phones, tablets, servers, etc. It can not only improve the connection performance and signal transmission speed of the circuit board, but also effectively reduce the volume and weight of the circuit board to meet the needs of modern electronic products for miniaturization and lightweight. In the existing PCB back drilling process, accurate measurement of board thickness is a key link to ensure processing accuracy and finished product quality.

[0003] However, the traditional board thickness measurement method relies too much on manual operation and has many defects. Specifically, technicians usually need to judge the distance between the marks based on the distribution of the back drill and their personal experience, and manually mark the marks on the PCB board one by one. This process is not only time-consuming and laborious, but also easily affected by human factors, such as visual fatigue, operational errors, etc., which leads to increased measurement errors. In addition, the manual marking method cannot achieve automated operation, which greatly limits the improvement of processing efficiency. What is more serious is that due to the uncontrollability of manual operation, the traditional method often cannot maintain consistent measurement force and accuracy during the measurement process, making it impossible to guarantee the reliability and stability of the measurement results. This will not only affect the accuracy of the back drilling process and the quality of the finished product, but also increase the difficulty and cost of subsequent processing and testing. Summary of the invention

[0004] The purpose of the present invention is to realize program automation, flexibly select the number of measuring points according to actual needs, significantly improve processing efficiency and accuracy, and propose a method for back drilling to measure board thickness in PCB processing.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] A method for measuring the thickness of a PCB by back drilling during PCB processing, comprising the following steps:

[0007] S10, inner layer circuit production and multilayer board lamination, the inner layer circuit of the PCB is produced, and the inner layer circuit board is combined with copper foil, prepreg and other materials into a multilayer board through a lamination process;

[0008] S20, preparation for drilling and thickness measurement, drilling the required through holes and back-drilled holes on the multilayer board, preparing thickness measurement drawings and thickness measurement programs, dividing the drawings into square grids at a certain density, and marking the positions and diameters of all back-drilled holes, through holes and identification holes. At the same time, preparing thickness measurement programs corresponding to the drawings, which contain alignment hole coordinates and grid coordinates, to guide the operation of the automatic thickness measurement equipment;

[0009] S30, automatic measurement of plate thickness. Place the multilayer plate on the automatic thickness measuring device. According to the coordinate position in the thickness measuring program, use the automatic thickness measuring device with alignment function to measure the plate thickness of each grid. The automatic thickness measuring device collects plate thickness data in real time and transmits the data to the data processing system for analysis. The data processing system processes the measured data according to the preset algorithm and threshold value to obtain accurate plate thickness distribution and deviation.

[0010] S40, electroplating and back drilling processing, according to the measured board thickness data, accurate back drilling processing is carried out, and the PCB after drilling is electroplated;

[0011] S50, subsequent processing and finished product inspection, electroplating treatment is performed again, the required circuit pattern is made on the outer layer, followed by solder mask treatment, and finally, the finished circuit board is inspected and tested.

[0012] Based on the above technical solution, the present invention can also be improved as follows.

[0013] Furthermore, the circuit production in step S10 includes the steps of designing an inner layer circuit pattern, producing an inner layer copper foil, and etching, wherein when designing the inner layer circuit pattern, the pattern of the inner layer circuit is drawn using one of the circuit design software such as Altium Designer, Eagle, KiCad, OrCAD, and Mentor Graphics PADS; when producing the inner layer copper foil, the designed inner layer circuit pattern is transferred to the copper foil through photoengraving technology to form a copper foil board with a desired circuit structure; when etching, the copper foil board is etched using an etching solution to etch away the unprotected copper foil portion, thereby forming the desired circuit structure.

[0014] Furthermore, during the lamination process in step S10, the prepared inner layer circuit board, copper foil, prepreg and other materials are arranged in a predetermined stacking order, wherein the size and thickness of each layer of material must be ensured to meet the requirements. During the lamination process, the temperature, pressure and time parameters must be controlled to ensure that the layers are tightly combined to form a complete multi-layer circuit board. After the lamination is completed, the multi-layer board is deburred, cleaned, etc. to remove impurities and residues generated during the lamination process.

[0015] Furthermore, in step S20, a laser drilling machine is used for drilling. The thickness measurement program also includes a data processing algorithm, which can automatically calculate and output the overall thickness of the multilayer board, the thickness between each layer, and the local thickness information of each hole position. When preparing the thickness measurement drawing in step S20, the grid is defined with a specific side length, and the software is used to draw a grid outward on the PCB with the center of the board as the origin. The grid with deep drilled holes is marked as a thickness measurement grid. The thickness measurement grid is named with numbers from left to right and from top to bottom, and the numbers are displayed in the grid. The drawing must also show the back drill holes and through holes at the current time, as well as the identification holes outside the board. Finally, the thickness measurement drawing is output to the specified path.

[0016] Furthermore, the thickness measurement program includes alignment holes, the number of alignment holes is at least 3, the thickness measurement coordinates are the coordinates of the exact center of the grid, and the coordinates are output in numerical order of the grid; the automatic thickness measurement equipment is also provided with a data analysis module and a data processing module, which automatically calculates and outputs the overall thickness of the multilayer board, the thickness between each layer and the local thickness information of each hole position according to the measurement data.

[0017] Furthermore, in step S40, before electroplating, the drilled PCB needs to be pretreated, including cleaning, degreasing, and removing the oxide layer, etc., to ensure that the plating solution can be evenly and tightly attached to the hole wall and the copper foil surface. According to the required electroplating layer material, a suitable plating solution is selected and prepared. The concentration, temperature, and pH value of the plating solution must be controlled within a preset range to ensure the uniformity and quality of the electroplating layer. The pretreated PCB is placed in an electroplating tank, and the thickness and uniformity of the electroplating layer are controlled by adjusting parameters such as current density and electroplating time. After electroplating, the PCB is cleaned and dried to remove residual plating solution and impurities. After the back drilling process is completed, the processing results are quality checked, including checking the hole diameter, hole depth, position accuracy of the back-drilled hole, and the integrity of the circuit board surface. For processing results that do not meet the requirements, they are repaired or reprocessed.

[0018] Furthermore, in step S50, small apertures or deep holes on the PCB can be filled with resin. According to the size, depth, and required strength of the hole, a suitable resin material is selected and mixed in a certain proportion. The mixed resin is filled into the hole by injection or dipping to ensure that the resin can evenly and tightly fill the entire hole wall, and excess resin is removed to maintain the flatness of the circuit board surface. The filled circuit board is placed in a curing device, and the resin is cured by heating, pressurizing, etc.

[0019] Furthermore, after the resin plugging process is completed, normal electroplating treatment is carried out. During the electroplating process, the concentration, temperature, current density and other parameters of the electroplating solution are controlled to ensure that the electroplating layer can be evenly and tightly attached to the copper foil and the hole wall.

[0020] Furthermore, during the inspection and testing, the finished circuit boards can be visually inspected, including checking the flatness, color uniformity, damage and stains on the surface of the circuit boards, and using specific testing equipment to check the circuit connectivity of the circuit boards to ensure that the connections between the circuits are correct, without open circuits or short circuits. At the same time, the circuit boards are also required to be tested for electrical performance, including insulation resistance, dielectric constant and withstand voltage tests, to ensure that the electrical performance of the circuit boards meets the design requirements. Finally, according to the use environment and requirements of the circuit boards, functional tests and reliability tests are performed, tests simulating actual working environments, long-term working stability tests, etc., to ensure that the quality and performance of the circuit boards are stable and reliable.

[0021] Compared with the prior art, the technical solution of this application has the following beneficial technical effects:

[0022] The present invention completely abandons the traditional manual marking and measurement methods by introducing an automated thickness measurement process, thereby greatly improving the measurement efficiency and effectively reducing the influence of human factors on the measurement results. With the assistance of the automatic thickness measurement equipment, the measurement accuracy has been significantly improved, so that the distribution and deviation of the plate thickness can be presented more accurately. Secondly, the method carefully prepares the thickness measurement drawings and thickness measurement programs in the drilling and thickness measurement preparation stages. These tools not only provide clear operating instructions for the automatic thickness measurement equipment, but also ensure the normalization and standardization of the measurement process. The square grids divided by a certain density on the drawings and the marked hole positions Information has laid a solid foundation for subsequent precise measurement. Furthermore, this method ensures the high-quality combination of multilayer boards during the inner-layer circuit production and multilayer board lamination stages, providing a stable substrate for subsequent back drilling and board thickness measurement. At the same time, in the electroplating and back drilling stages, as well as the subsequent processing and finished product inspection stages, this method also strictly follows the established process flow and quality standards, thereby ensuring the high quality and reliability of the finished circuit boards. In summary, this method not only greatly improves the efficiency and accuracy of board thickness measurement in PCB back drilling, but also ensures the high-quality completion of the entire processing process by introducing automated processes and standardized operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A method flow chart of a method for measuring board thickness by back drilling in PCB processing according to the present invention;

[0024] Figure 2 The present invention is a schematic diagram of a thickness measurement drawing of a method for measuring board thickness by back drilling in PCB processing. DETAILED DESCRIPTION

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

[0026] Combination Figure 1-Figure 2 As shown, a method for measuring the thickness of a PCB by back drilling during PCB processing of the present invention comprises the following steps:

[0027] S10, inner layer circuit production and multilayer board lamination, the inner layer circuit of the PCB is produced, and the inner layer circuit board is combined with copper foil, prepreg and other materials into a multilayer board through a lamination process;

[0028] S20, preparation for drilling and thickness measurement, drilling the required through holes and back-drilled holes on the multilayer board, preparing thickness measurement drawings and thickness measurement programs, dividing the drawings into square grids at a certain density, and marking the positions and diameters of all back-drilled holes, through holes and identification holes. At the same time, preparing thickness measurement programs corresponding to the drawings, which contain alignment hole coordinates and grid coordinates, to guide the operation of the automatic thickness measurement equipment;

[0029] S30, automatic measurement of plate thickness. Place the multilayer plate on the automatic thickness measuring device. According to the coordinate position in the thickness measuring program, use the automatic thickness measuring device with alignment function to measure the plate thickness of each grid. The automatic thickness measuring device collects plate thickness data in real time and transmits the data to the data processing system for analysis. The data processing system processes the measured data according to the preset algorithm and threshold value to obtain accurate plate thickness distribution and deviation.

[0030] S40, electroplating and back drilling processing, according to the measured board thickness data, accurate back drilling processing is carried out, and the PCB after drilling is electroplated;

[0031] S50, subsequent processing and finished product inspection, electroplating treatment is performed again, the required circuit pattern is made on the outer layer, followed by solder mask treatment, and finally, the finished circuit board is inspected and tested.

[0032] In a preferred embodiment, the present invention can be further configured as follows: in step S10, the circuit production includes the steps of designing the inner layer circuit pattern, making the inner layer copper foil, and etching, wherein when designing the inner layer circuit pattern, the inner layer circuit pattern is drawn using one of the circuit design softwares such as AltiumDesigner, Eagle, KiCad, OrCAD, and Mentor Graphics PADS; when making the inner layer copper foil, the designed inner layer circuit pattern is transferred to the copper foil by photolithography technology to form a copper foil board with a desired circuit structure; when etching, the copper foil board is etched using an etching liquid to etch away the unprotected copper foil portion, thereby forming the desired circuit structure; Altium Designer, Eagle, KiCad, OrCAD, or Mentor Graphics PADS is used to print the inner layer circuit pattern; and when etching, the inner layer copper foil is printed using a printing plate. PADS and other professional circuit design software are used to design the inner layer circuit pattern, which greatly improves the accuracy and flexibility of the design. These software not only provide a rich component library and powerful layout and routing functions, but also support automated design verification and simulation, so as to effectively reduce errors and improve design efficiency in the design stage. Secondly, when making the inner copper foil, the designed inner layer circuit pattern is transferred to the copper foil through photolithography technology. This step not only ensures the accurate replication of the pattern, but also greatly improves the production efficiency. With its high precision and high resolution, the photolithography technology makes the circuit structure on the copper foil board highly consistent with the design pattern, laying a solid foundation for the subsequent etching process. Finally, in the etching stage, the copper foil board is etched with etching liquid to etch away the copper foil part that is not covered by protective layers such as photoresist to form the required circuit structure. This step not only realizes the fine processing of the circuit, but also ensures the stability and reliability of the circuit structure. By accurately controlling the concentration, temperature and etching time of the etching liquid and other parameters, the etching effect can be further optimized to improve the quality and performance of the circuit.

[0033] In a preferred embodiment, the present invention can be further configured as follows: in the process of lamination in step S10, the prepared inner layer circuit board, copper foil, prepreg and other materials are arranged in a predetermined stacking order, wherein the size and thickness of each layer of material must be ensured to meet the requirements. During the lamination process, the temperature, pressure and time parameters must be controlled to ensure that each layer is tightly combined to form a complete multi-layer circuit board. After the lamination is completed, the multi-layer board is deburred, cleaned, etc. to remove impurities and residues generated during the lamination process. During the lamination process, strict control of the size and thickness of each layer of material is the key to ensuring the quality of the circuit board. This step not only requires precise matching of material sizes, but also requires consideration of physical properties such as thermal expansion and contraction of the material to ensure that circuit errors due to size mismatch do not occur during the lamination process. At the same time, precise control of temperature, pressure and time parameters can ensure that each layer of material is tightly bonded to form a complete and strong multi-layer circuit board. This tight bonding not only improves the mechanical strength of the circuit board, but also helps to improve the electrical connection performance between circuits. After the lamination is completed, deburring and cleaning the multi-layer board are important measures to further ensure the quality of the circuit board. Deburring can remove the tiny protrusions or depressions produced during the lamination process to ensure the flatness of the circuit board surface; cleaning can remove impurities and residues produced during the lamination process, such as glue stains, oil stains, etc., to avoid these pollutants from adversely affecting the performance of the circuit board. These subsequent processing steps not only improve the appearance quality of the circuit board, but also ensure the stability and reliability of the circuit board during long-term use.

[0034] In a preferred embodiment, the present invention can be further configured as follows: in step S20, a laser drilling machine is used to perform drilling processing when drilling holes. The thickness measurement program also includes a data processing algorithm, which can automatically calculate and output the overall thickness of the multilayer board, the thickness between each layer, and the local thickness information of each hole position. When preparing the thickness measurement drawing in step S20, the grid is defined with a specific side length, and the software is used to draw a grid outward from the center of the board surface as the origin on the PCB. The grid with deep drill holes is marked as a thickness measurement grid. The thickness measurement grid is named with numbers from left to right and from top to bottom, and the numbers are displayed in the grid. The back drilling holes and through holes at the current time must also be displayed on the drawing, and The holes are marked outside the board. Finally, the thickness measurement drawing is output to the specified path. The laser drilling machine is used for drilling. Compared with the traditional mechanical drilling method, it has higher accuracy and efficiency, and can significantly reduce the error and damage in the drilling process, thereby improving the reliability and service life of the circuit board. At the same time, the data processing algorithm contained in the thickness measurement program provides unprecedented convenience and accuracy for the thickness measurement of multilayer boards. The algorithm can automatically calculate and output the overall thickness of the multilayer board, the thickness between each layer, and the local thickness of each hole position. This information is crucial for evaluating the structural stability and electrical performance of the circuit board. By accurately measuring and recording these data According to the data, manufacturers can promptly detect and solve potential uneven thickness or thickness deviation problems, thereby ensuring that each circuit board meets the design requirements and quality standards. When preparing thickness measurement drawings, an efficient and intuitive method is also adopted. By defining the grid with a specific side length and using the software to draw the grid outward from the center of the board surface on the PCB, manufacturers can easily mark the hole positions that need to be measured, especially for those grids with deep drill holes, which are specially marked as thickness measurement grids and named with numbers from left to right and from top to bottom. These numbers are directly displayed in the grid, allowing measurement personnel to identify the positions that need to be measured at a glance. In addition, the thickness measurement drawing also shows in detail the back-drilled holes and through-holes at the current time, as well as the off-board identification holes. This information is of great guiding significance for the subsequent processing and assembly process. By integrating these key information into one drawing, manufacturers can greatly improve production efficiency and accuracy, and reduce errors and delays caused by missing or misunderstanding information. Finally, outputting the thickness measurement drawing to the specified path not only facilitates the manufacturer's storage and management, but also provides an important basis for subsequent quality traceability and problem analysis. The addition of this step makes the entire multi-layer circuit board manufacturing process more standardized and systematic, which helps to improve the overall production quality and efficiency.

[0035] In a preferred embodiment, the present invention can be further configured as follows: the thickness measurement program includes alignment holes, the number of alignment holes is at least 3, the thickness measurement coordinates are the coordinates of the exact center of the grid, and the coordinates are output in the numerical order of the grid; the automatic thickness measurement equipment is also provided with a data analysis module and a data processing module, which automatically calculate and output the overall thickness of the multilayer board, the thickness between each layer and the local thickness information of each hole position according to the measurement data. By introducing at least 3 alignment holes in the thickness measurement program, this design greatly enhances the accuracy and stability of the measurement. The alignment holes serve as the reference points for the measurement, and the number of the alignment holes is sufficient to ensure that during the measurement process, no matter how the circuit board is placed or moved, the position of the circuit board can be accurately determined through these three or more alignment holes, thereby avoiding the measurement error caused by position deviation. Secondly, The thickness measurement coordinates are taken from the exact center of the grid and the coordinates are output in numerical order. This approach not only simplifies the measurement process, but also improves the readability and traceability of the measurement data. By taking the exact center of the grid as the coordinate origin and outputting the coordinates in numerical order, manufacturers can easily identify the position of each measurement point, which is crucial for subsequent data analysis and processing. More importantly, the automatic thickness measurement equipment is also equipped with a data analysis module and a data processing module. The addition of these two modules makes the processing and analysis of measurement data more efficient and accurate. The data analysis module can automatically receive and process the raw data from the measuring equipment, while the data processing module automatically calculates and outputs the overall thickness of the multilayer board, the thickness between each layer, and the local thickness information of each hole position according to the preset algorithms and formulas.

[0036] In a preferred embodiment of the present invention, the following configuration can be further performed: in step S40, before electroplating, the drilled PCB needs to be pre-treated, including cleaning, degreasing, and removing the oxide layer, so as to ensure that the electroplating solution can be evenly and tightly attached to the hole wall and the copper foil surface; according to the required electroplating layer material, a suitable electroplating solution is selected and prepared; the concentration, temperature, and pH value of the electroplating solution need to be controlled within a preset range to ensure the uniformity and quality of the electroplating layer; the pre-treated PCB is placed in an electroplating tank; by adjusting parameters such as current density and electroplating time, the thickness and uniformity of the electroplating layer are controlled; after electroplating, the PCB is cleaned and dried to remove residual electroplating solution and impurities; and the back drilling process is completed. After completion, the processing results are checked for quality, including the back-drilled hole diameter, hole depth, position accuracy and integrity of the circuit board surface. For processing results that do not meet the requirements, they are repaired or reprocessed. The PCB after drilling is pretreated before electroplating, including cleaning, degreasing, and removing the oxide layer. This measure is crucial. It ensures that the plating solution can adhere evenly and tightly to the hole wall and copper foil surface, laying a solid foundation for the subsequent electroplating process. The pretreatment not only removes surface pollutants and oxide layers, but also improves the wettability of the plating solution and the PCB surface, thereby ensuring the adhesion and uniformity of the electroplating layer. Secondly, according to the required electroplating layer material, select and prepare the appropriate The electroplating solution is used, and the concentration, temperature, pH value and other parameters of the electroplating solution are strictly controlled. This practice ensures the quality and uniformity of the electroplating layer. The formula and parameters of the electroplating solution have a direct impact on the performance of the electroplating layer. By accurately controlling these factors, an electroplating layer with excellent conductivity, corrosion resistance and mechanical strength can be obtained, thereby meeting the high quality requirements of the electroplating layer for multi-layer circuit boards. During the electroplating process, the pre-treated PCB is placed in the electroplating tank, and the thickness and uniformity of the electroplating layer are accurately controlled by adjusting parameters such as current density and electroplating time. The precise control of this step enables the electroplating layer to not only meet the design requirements, but also maintain a high degree of stability and consistency, which is very important for multi-layer circuit boards. The electrical performance and reliability of the back-drilling circuit board are crucial. After the electroplating is completed, the PCB is cleaned and dried to remove the residual plating solution and impurities. This step is also indispensable. Cleaning and drying can ensure the surface cleanliness and dryness of the electroplating layer, avoiding the degradation of electrical performance or reliability problems caused by residues. Finally, after the back drilling process is completed, the processing results are quality checked, including checking the aperture, hole depth, position accuracy of the back-drilled holes and the integrity of the circuit board surface. This step ensures that the quality of the back drilling process meets the design requirements. For processing results that do not meet the requirements, they are repaired or reprocessed in time to avoid the scrapping of circuit boards or performance degradation due to quality problems.

[0037] In a preferred embodiment, the present invention can be further configured as follows: in step S50, resin filling can be performed for small apertures or deep holes on the PCB. According to the size, depth, and required strength of the hole, a suitable resin material is selected and mixed in a certain proportion. The prepared resin is filled into the hole by injection or dipping to ensure that the resin can evenly and tightly fill the entire hole wall, and excess resin is removed to maintain the flatness of the circuit board surface. The filled circuit board is placed in a curing device, and the resin is cured by heating, pressurizing, etc. The resin filling of small apertures or deep holes on the PCB can effectively improve the mechanical strength and electrical performance of the circuit board. Small apertures or deep holes often constitute electrical connection channels in the circuit board, but they may also become weak links in the circuit board structure. By selecting a suitable resin material for filling, the strength of these areas can be significantly improved to prevent problems such as breakage or deformation during subsequent processing or use. At the same time, resin filling can also improve the electrical insulation performance of the hole wall and improve the overall electrical performance of the circuit board. Secondly, it is emphasized that according to the size, depth, and required strength of the hole, a suitable resin material is selected and mixed in a certain proportion. This is done The method ensures the pertinence and effectiveness of resin filling. Different hole sizes and depths have different requirements for resin materials. By accurately matching the types and ratios of resin materials, it can be ensured that the circuit board after resin filling has the best mechanical and electrical properties. In the resin filling process, it is also stipulated that the prepared resin is filled into the hole by injection or dipping, and it is ensured that the resin can evenly and tightly fill the entire hole wall. The precise control of this step is crucial to the effect of resin filling. By ensuring that the resin evenly and tightly fills the hole wall, the strength and electrical properties of the circuit board can be further improved, while avoiding defects such as bubbles or gaps during the resin filling process. In addition, removing excess resin to maintain the flatness of the circuit board surface is also an important link. Excess resin will not only affect the aesthetics of the circuit board, but may also cause inconvenience to subsequent processing and use. By removing excess resin, the flatness of the circuit board surface can be ensured, which provides convenience for subsequent processing and use. Finally, the filled circuit board is placed in a curing device, and the resin is cured by heating, pressurizing, etc. This is the last step of the resin filling process. The curing process ensures the stability and reliability of the resin filling layer, giving the circuit board higher strength and longer service life.

[0038] In a preferred embodiment, the present invention can be further configured as follows: after the resin plugging process is completed, a normal electroplating treatment is performed. During the electroplating process, by controlling the concentration, temperature, current density and other parameters of the electroplating solution, it is ensured that the electroplating layer can be evenly and tightly attached to the copper foil and the hole wall. In the manufacturing process of multi-layer circuit boards, the resin plugging process is a key step to ensure that small apertures or deep holes are effectively filled, thereby improving the mechanical strength and electrical properties of the circuit board. However, resin filling alone is not sufficient to meet the circuit board's requirements for electrical connection and surface protection. Therefore, after the resin plugging process is completed, it becomes particularly important to perform a normal electroplating treatment. The electroplating treatment can form a uniform and tight electroplating layer on the copper foil and the hole wall. This electroplating layer not only has good conductive properties, but also can provide additional protection to prevent the copper foil and the hole wall from being damaged in subsequent additions. At the same time, the electroplating layer can also enhance the overall aesthetics of the circuit board and improve the market competitiveness of the product. In the electroplating process, it is very important to control the concentration, temperature, current density and other parameters of the plating solution. The concentration and temperature of the plating solution directly affect the deposition rate and quality of the electroplating layer, while the current density determines the thickness and uniformity of the electroplating layer. By precisely controlling these parameters, it can be ensured that the electroplating layer can be evenly and tightly attached to the copper foil and the hole wall to avoid problems such as uneven thickness and poor adhesion of the electroplating layer. In addition, the normal progress of the electroplating treatment is also emphasized, which means that certain process flows and operating specifications need to be followed during the electroplating process to ensure the quality and stability of the electroplating layer. Normal electroplating treatment can not only meet the needs of the circuit board for electrical connection and surface protection, but also provide reliable guarantees for subsequent processing and use.

[0039] In a preferred embodiment, the present invention can be further configured as follows: during inspection and testing, the finished circuit board can be inspected for appearance, including inspection of the flatness, color uniformity, damage and stains on the surface of the circuit board, and specific test equipment is used to inspect the circuit connectivity of the circuit board to ensure that the connections between the circuits are correct, without open circuits or short circuits. At the same time, the circuit board needs to be tested for electrical performance, including insulation resistance, dielectric constant and withstand voltage tests to ensure that the electrical performance of the circuit board meets the design requirements. Finally, according to the use environment and requirements of the circuit board, functional tests and reliability tests are performed, tests simulating the actual working environment, long-term working stability tests, etc. are performed to ensure that the quality and performance of the circuit board are stable and reliable. In the appearance inspection link, by inspecting the flatness, color uniformity, damage and stains on the surface of the circuit board, the basic quality status of the circuit board can be intuitively judged. This step is the basis for subsequent testing and can effectively screen out circuit boards with obvious defects to prevent them from entering the next stage of testing or production processes, thereby reducing cost waste caused by quality problems. Secondly, specific test equipment is used to inspect the circuit connectivity of the circuit board to ensure that the connections between the circuits are correct. The circuit connectivity test can accurately locate and repair potential connection problems, avoid signal transmission failure or functional failure after the circuit board is put into use, and improve the reliability and stability of the circuit board. Furthermore, the electrical performance test of the circuit board, including insulation resistance, dielectric constant and withstand voltage test, is a key step in evaluating whether the electrical performance of the circuit board meets the design requirements. These tests can ensure that the circuit board has good electrical insulation performance and stable working state when it is subjected to normal working voltage and special working environment, thereby ensuring the reliable operation of the circuit board in a complex environment. Finally, according to the use environment and requirements of the circuit board, functional tests and reliability tests are carried out, such as tests simulating the actual working environment and long-term working stability tests, which are important links for comprehensive evaluation of the quality and performance of the circuit board. These tests can simulate various situations of the circuit board in actual use, verify whether it can work stably under various conditions, and whether it has sufficient durability and reliability. Through this step, circuit boards with excellent performance and reliable quality can be further screened out, providing a strong guarantee for the high-quality production of electronic products.

[0040] Example

[0041] Step S10: Inner layer circuit production and multilayer board lamination

[0042] Design the inner layer circuit pattern: Use AltiumDesigner software to draw the inner layer circuit pattern according to the circuit design requirements. After the pattern design is completed, save it as a Gerber file for subsequent production;

[0043] Making inner copper foil: The designed inner circuit pattern is transferred to the copper foil through photolithography technology. The specific steps include: importing the Gerber file into the platemaking machine, using laser to punch holes corresponding to the inner circuit pattern on the platemaking material; then, covering the copper foil on the platemaking material, and removing the part of the copper foil not protected by the platemaking material by chemical etching or electroplating to form a copper foil board with the required circuit structure;

[0044] Etching treatment: put the copper foil board into the etching solution, and use the chemical action of the etching solution to etch away the unprotected copper foil part, so as to obtain a complete inner layer circuit structure. After the etching is completed, the copper foil board is cleaned and dried to remove the residual etching solution and impurities;

[0045] Multilayer board lamination: Arrange the prepared inner layer circuit board, copper foil, prepreg and other materials in a predetermined stacking order to ensure that the size and thickness of each layer of material meet the requirements. Then, put the arranged multilayer materials into the laminating machine and laminarize them under the set temperature, pressure and time parameters to make each layer tightly bonded to form a complete multilayer circuit board. After lamination, the multilayer board is deburred and cleaned to remove impurities and residues generated during the lamination process.

[0046] Step S20: preparation for drilling and thickness measurement;

[0047] Drilling: Use a laser drilling machine to drill holes in the multilayer board to drill the required through holes and back-drilled holes. During the drilling process, ensure that the drilling position is accurate and the hole diameter and hole depth meet the requirements;

[0048] Prepare thickness measurement drawings and thickness measurement programs: According to the size of the multilayer board and the distribution of back-drilled holes, define the grid with a side length of 20mm. Use software to draw a grid on the PCB with the center of the board as the origin. If there are deep drilled holes in the grid, it is marked as a thickness measurement grid. The thickness measurement grid is named from left to right and from top to bottom, and the numbers are displayed in the grid. The current back-drilled holes (diameter 0.5mm), through holes (aperture 0.1mm) and off-board identification holes (aperture 3.1mm) must also be displayed on the drawing. Finally, the thickness measurement drawing is output to the specified path;

[0049] The thickness measurement program includes alignment holes (3.1mm in diameter, 3 in number). The alignment hole coordinates correspond to the grid coordinates on the drawing. The thickness measurement coordinates are the coordinates of the exact center of the grid, and the coordinates are output in numerical order of the grid. The program also includes a data processing algorithm that can automatically calculate and output the overall thickness of the multilayer board, the thickness between each layer, and the local thickness information of each hole position.

[0050] Step S30: Automatically measure the plate thickness;

[0051] Place the multilayer board on the automatic thickness measuring device, and measure the board thickness of each grid using the automatic thickness measuring device with alignment function according to the coordinate position in the thickness measuring program. The automatic thickness measuring device collects the board thickness data in real time and transmits the data to the data processing system for analysis. The data processing system processes the measured data according to the preset algorithm and threshold value to obtain accurate board thickness distribution and deviation.

[0052] Step S40: electroplating and back drilling;

[0053] Pretreatment before electroplating: Clean, degrease, and remove the oxide layer of the PCB after drilling to ensure that the electroplating solution can adhere evenly and tightly to the hole wall and copper foil surface;

[0054] Electroplating treatment: According to the required electroplating layer material, select and prepare the appropriate electroplating solution. The concentration, temperature and pH value of the electroplating solution must be controlled within the preset range. The pre-treated PCB is placed in the electroplating tank. By adjusting the current density, electroplating time and other parameters, the thickness and uniformity of the electroplating layer are controlled. After the electroplating is completed, the PCB is cleaned and dried to remove the residual electroplating solution and impurities.

[0055] Back drilling: Based on the measured board thickness data, accurate back drilling is performed. During the processing, it is necessary to ensure that the back drilling hole diameter, hole depth, position accuracy and integrity of the circuit board surface meet the requirements. For processing results that do not meet the requirements, repair or reprocess them;

[0056] Step S50: subsequent processing and finished product inspection;

[0057] Resin filling: For small-diameter or deep holes on PCB, select appropriate resin materials and mix them in a certain proportion. Fill the prepared resin into the hole by injection or dipping to ensure that the resin can evenly and tightly fill the entire hole wall. After filling, remove excess resin to maintain the flatness of the circuit board surface. Place the filled circuit board in the curing equipment and cure the resin by heating and pressurizing.

[0058] Secondary electroplating treatment: After the resin plugging process is completed, normal electroplating treatment is carried out to further protect the circuit board surface and hole wall. During the electroplating process, the concentration, temperature, current density and other parameters of the electroplating solution must also be controlled to ensure that the electroplating layer can be evenly and tightly attached to the copper foil and the hole wall;

[0059] Outer layer pattern transfer and solder mask treatment: Make the required circuit pattern on the outer layer and perform solder mask treatment to protect the circuit structure on the circuit board from the influence of the external environment;

[0060] Finished product inspection and testing: Perform an appearance inspection on the finished circuit boards, including checking the flatness, color uniformity, damage, and stains on the surface of the circuit boards. Use specific testing equipment to check the circuit connectivity of the circuit boards to ensure that the connections between the circuits are correct, without open circuits or short circuits. At the same time, the circuit boards are also required to undergo electrical performance tests, including insulation resistance, dielectric constant, and withstand voltage tests, to ensure that the electrical performance of the circuit boards meets the design requirements. Finally, according to the use environment and requirements of the circuit boards, functional tests and reliability tests are performed, tests that simulate actual working environments, and long-term working stability tests, to ensure that the quality and performance of the circuit boards are stable and reliable.

[0061] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0062] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for measuring the thickness of a PCB by back drilling during PCB processing, characterized in that: The steps include: S10, inner layer circuit production and multilayer board lamination, the inner layer circuit of the PCB is produced, and the inner layer circuit board is combined with copper foil, prepreg and other materials into a multilayer board through a lamination process; S20, preparation for drilling and thickness measurement, drilling the required through holes and back-drilled holes on the multilayer board, preparing thickness measurement drawings and thickness measurement programs, dividing the drawings into square grids at a certain density, and marking the positions and diameters of all back-drilled holes, through holes and identification holes. At the same time, preparing thickness measurement programs corresponding to the drawings, which contain alignment hole coordinates and grid coordinates, to guide the operation of the automatic thickness measurement equipment; S30, automatic measurement of plate thickness. Place the multilayer plate on the automatic thickness measuring device. According to the coordinate position in the thickness measuring program, use the automatic thickness measuring device with alignment function to measure the plate thickness of each grid. The automatic thickness measuring device collects plate thickness data in real time and transmits the data to the data processing system for analysis. The data processing system processes the measured data according to the preset algorithm and threshold value to obtain accurate plate thickness distribution and deviation. S40, electroplating and back drilling processing, according to the measured board thickness data, accurate back drilling processing is carried out, and the PCB after drilling is electroplated; S50, subsequent processing and finished product inspection, electroplating treatment is performed again, the required circuit pattern is made on the outer layer, followed by solder mask treatment, and finally, the finished circuit board is inspected and tested.

2. The method for measuring the thickness of a PCB by back drilling in PCB processing according to claim 1, characterized in that: The circuit production in step S10 includes the steps of designing an inner layer circuit pattern, producing an inner layer copper foil, and performing etching. When designing the inner layer circuit pattern, the pattern of the inner layer circuit is drawn using one of the circuit design software such as Altium Designer, Eagle, KiCad, OrCAD, and Mentor Graphics PADS. When producing the inner layer copper foil, the designed inner layer circuit pattern is transferred to the copper foil through photoengraving technology to form a copper foil board with a desired circuit structure. When etching, the copper foil board is etched using an etching solution to etch away the unprotected copper foil portion, thereby forming the desired circuit structure.

3. The method for measuring the thickness of a PCB by back drilling in PCB processing according to claim 1, characterized in that: During the lamination process in step S10, the prepared inner layer circuit board, copper foil, prepreg and other materials are arranged in a predetermined stacking order, wherein the size and thickness of each layer of material must be ensured to meet the requirements. During the lamination process, the temperature, pressure and time parameters must be controlled to ensure that the layers are tightly combined to form a complete multi-layer circuit board. After the lamination is completed, the multi-layer board is deburred, cleaned, etc. to remove impurities and residues generated during the lamination process.

4. The method for measuring the thickness of a PCB by back drilling in PCB processing according to claim 1, characterized in that: In step S20, a laser drilling machine is used to perform drilling processing. The thickness measurement program also includes a data processing algorithm, which can automatically calculate and output the overall thickness of the multilayer board, the thickness between each layer, and the local thickness information of each hole position. When preparing the thickness measurement drawing in step S20, the grid is defined with a specific side length, and the software is used to draw a grid outward on the PCB with the center of the board as the origin. The grid with deep drill holes in it is marked as a thickness measurement grid. The thickness measurement grid is named with numbers from left to right and from top to bottom, and the numbers are displayed in the grid. The drawing must also show the back drill holes and through holes at the current time, as well as the identification holes outside the board. Finally, the thickness measurement drawing is output to the specified path.

5. The method for measuring the thickness of a PCB by back drilling in PCB processing according to claim 1, characterized in that: The thickness measurement program includes alignment holes, the number of which is at least 3. The thickness measurement coordinates are the coordinates of the exact center of the grid, and the coordinates are output in numerical order of the grid. The automatic thickness measurement equipment is also provided with a data analysis module and a data processing module, which automatically calculate and output the overall thickness of the multilayer board, the thickness between each layer, and the local thickness information of each hole position according to the measurement data.

6. The method for measuring the thickness of a PCB by back drilling in PCB processing according to claim 1, characterized in that: In step S40, before electroplating, the drilled PCB needs to be pre-treated, including cleaning, degreasing, and removing the oxide layer, so as to ensure that the electroplating solution can be evenly and tightly attached to the hole wall and the copper foil surface. According to the required electroplating layer material, a suitable electroplating solution is selected and prepared. The concentration, temperature, and pH value of the electroplating solution must be controlled within a preset range to ensure the uniformity and quality of the electroplating layer. The pre-treated PCB is placed in an electroplating tank, and the thickness and uniformity of the electroplating layer are controlled by adjusting parameters such as current density and electroplating time. After the electroplating is completed, the PCB is cleaned and dried to remove residual electroplating solution and impurities. After the back drilling process is completed, the processing results are quality checked, including checking the hole diameter, hole depth, position accuracy of the back-drilled hole, and the integrity of the circuit board surface. For processing results that do not meet the requirements, they are repaired or reprocessed.

7. The method for measuring the thickness of a PCB by back drilling in PCB processing according to claim 1, characterized in that: In step S50, resin filling can be performed for small apertures or deep holes on the PCB. According to the size, depth, and required strength of the hole, a suitable resin material is selected and mixed in a certain proportion. The mixed resin is filled into the hole by injection or dipping to ensure that the resin can evenly and tightly fill the entire hole wall. Excess resin is removed to maintain the flatness of the circuit board surface. The filled circuit board is placed in a curing device to cure the resin by heating, pressurizing, and the like.

8. The method for measuring the thickness of a PCB by back drilling in PCB processing according to claim 7, characterized in that: After the resin plugging process is completed, normal electroplating treatment is carried out. During the electroplating process, the concentration, temperature, current density and other parameters of the electroplating solution are controlled to ensure that the electroplating layer can be evenly and tightly attached to the copper foil and the hole wall.

9. The method for measuring the thickness of a PCB by back drilling in PCB processing according to claim 1, characterized in that: During the inspection and testing, the finished circuit board can be inspected for appearance, including checking the flatness, color uniformity, damage and stains on the surface of the circuit board, and using specific testing equipment to check the circuit connectivity of the circuit board to ensure that the connections between the circuits are correct, without open circuits or short circuits. At the same time, the circuit board needs to be tested for electrical performance, including insulation resistance, dielectric constant and withstand voltage tests to ensure that the electrical performance of the circuit board meets the design requirements. Finally, according to the use environment and requirements of the circuit board, functional tests and reliability tests are carried out, tests simulating actual working environments, long-term working stability tests, etc., to ensure that the quality and performance of the circuit board are stable and reliable.

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