PCB back drilling depth determination method and electronic device

Abstract

The application discloses a PCB back-drilling depth determination method and electronic equipment, comprising: obtaining a plurality of drilling depths from a back-drilling surface to a target layer and a drill tip size parameter; when a drilling process is performed on a PCB, based on each drilling depth, a drill bit drills a target position in different PCBs of the same model to obtain a processed hole, and an optical device collects an image of each processed hole; images including a first color and a second color are screened out, and the center area of the image is a circular area; for each image, the working depth of the drill tip after reaching the target layer is determined according to the color, area parameter and drill tip size parameter of the circular area in the image; the difference between the drilling depth and the working depth is calculated to obtain the actual thickness of the back-drilling surface to the target layer corresponding to the current image; the average thickness is calculated according to the actual thickness corresponding to all images, and the back-drilling depth is calculated according to the average thickness and a preset residual stub length, thereby improving the accuracy and controllability of the residual stub length.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, and in particular to a method for determining the back-drilling depth of a PCB and an electronic device. Background Technology

[0002] Back-drilling is a key technology in the manufacturing of printed circuit boards (PCBs). It is mainly used to remove excess parts (i.e., stubs, also known as residuals) of vias (PTHs) in high-speed signal transmission to improve signal integrity.

[0003] In traditional technology, the control of residual piles in back drilling is related to the drilling accuracy, XY accuracy, the overall PCB thickness, and dielectric thickness. Among these, dielectric thickness has a significant impact on drilling accuracy and cannot be directly measured, making it difficult to improve the control accuracy of residual piles in back drilling.

[0004] In existing technologies, the depth between the back-drilled surface and the target layer is typically obtained by drilling test holes or slicing the edge area of ​​the circuit board, and this depth is used as the basis for subsequent back-drilling. However, during the PCB manufacturing process, the thickness of the dielectric layer in the edge area and the middle area of ​​the circuit board may vary due to factors such as lamination and adhesive flow. To ensure that the target layer is not drilled through, a large safety distance must be reserved. This safety distance usually needs to cover the range of board thickness fluctuations, which may result in excessively long residual studs after back-drilling, affecting signal transmission or causing open circuits due to drill breakage, thus posing a high reliability risk. Summary of the Invention

[0005] This invention provides a method for determining the back-drilling depth of a PCB, which solves the problems of difficulty in improving the control accuracy of back-drilling residue and high reliability risk in existing PCB back-drilling depth determination methods.

[0006] In a first aspect, the present invention provides a method for determining the back-drilling depth of a PCB, wherein the PCB includes a target layer and other layers, and the target layer is a circuit layer to which the signal needs to be connected;

[0007] The method includes:

[0008] Obtain multiple borehole depths and drill tip size parameters from the back drill face to the target layer;

[0009] When drilling a PCB, the drill bit is controlled to drill holes at target positions in multiple PCBs of the same model based on each drilling depth to obtain the processed holes. An image of each processed hole is acquired by an optical device. The image includes at least one of a first color and a second color. The first color corresponds to the target layer, and the second color corresponds to other layers adjacent to the target layer. The processed hole is a blind hole.

[0010] The images that include the first color and the second color are selected, and the central region of the images is a circular region;

[0011] For each image, the working depth of the drill tip after reaching the target layer is determined based on the color of the circular region in the image, the region parameters, and the drill tip size parameters.

[0012] Calculate the difference between the drilling depth and the working depth to obtain the actual thickness from the back drill surface to the target layer corresponding to the current image;

[0013] Calculate the average thickness from the back drill surface to the target layer based on the actual thickness corresponding to all the images;

[0014] The back-drilling depth is calculated based on the average thickness and the preset residual pile length when back-drilling the PCB at the target location.

[0015] Optionally, the drilling depth can be set as follows:

[0016] Obtain the theoretical thickness from the back drill face to the target layer;

[0017] Based on the theoretical thickness and the preset plate thickness error range, multiple drilling depths from the back drilling surface to the target layer are set.

[0018] Optionally, determining the working depth of the drill tip after reaching the target layer for each image, based on the color of the circular region in the image, region parameters, and the drill tip size parameters, includes:

[0019] For each image, the relative position of the current drill tip to the target layer is determined based on the color of the circular region in the image;

[0020] The working depth of the drill tip after reaching the target layer is determined based on the relative position, the region parameters of the circular area in the image, and the drill tip size parameters.

[0021] Optionally, determining the relative position of the current drill tip to the target layer based on the color of the circular region in the image includes:

[0022] If the color of the circular region in the image is the first color, then the relative position of the current drill tip and the target layer is determined to be that part of the drill tip has reached the target layer;

[0023] If the color of the circular region in the image is the second color, then the relative position of the current drill tip and the target layer is determined to be that the drill tip has partially passed through the target layer.

[0024] Optionally, determining the working depth of the drill tip after reaching the target layer based on the relative position, the region parameters of the circular area in the image, and the drill tip size parameters includes:

[0025] Based on the region parameters of the circular region in the image and the drill tip size parameters, calculate the drill tip length corresponding to the circular region;

[0026] If the relative position is such that part of the drill tip reaches the target layer, then the drill tip length is taken as the working depth of the drill tip after reaching the target layer;

[0027] If the relative position is such that part of the drill tip passes through the target layer, then the sum of the drill tip length and the known thickness of the target layer is calculated to obtain the working depth of the drill tip after reaching the target layer.

[0028] Optionally, the drill tip size parameters include the drill tip length, the region parameters of the circular region include the area ratio of the circular region, and the drill tip length corresponding to the circular region is calculated as follows:

[0029] h1 = h × (S1 / S) 1 / 2 ;

[0030] Where h1 is the drill tip length corresponding to the circular region, h is the drill tip length, S1 / S is the area ratio; S1 is the area of ​​the circular region in the image, and S is the area of ​​the image.

[0031] Optionally, the step of calculating the back-drilling depth of the PCB at the target location based on the average thickness and the preset residual pile length includes:

[0032] The total drilling depth is obtained by summing the average thickness with the preset compensated drilling depth.

[0033] The difference between the total drilling depth and the preset residual pile length is calculated to obtain the back drilling depth when back drilling is performed on the PCB at the target location.

[0034] Optionally, after acquiring an image of each of the machined holes using an optical device, the method further includes:

[0035] A second drilling is performed at the target location to obtain a through hole, thus completing one drilling operation.

[0036] Optionally, the diameter of the drill bit used during the secondary drilling is the target diameter of the drilling process, and the diameter of the drill bit used during the first drilling at the target position is smaller than the target diameter.

[0037] Secondly, the present invention provides a PCB back-drilling depth determination device, wherein the PCB includes a target layer and other layers, and the target layer is the circuit layer to which the signal needs to be connected;

[0038] The device includes:

[0039] The basic data acquisition module is used to acquire multiple borehole depths and drill tip size parameters from the back drill face to the target layer;

[0040] The drilling image acquisition module is used to control the drill bit to drill holes at target positions in multiple PCBs of the same model based on each drilling depth when drilling a PCB. The module also acquires an image of each hole through an optical device. The image includes at least one of a first color and a second color. The first color corresponds to the target layer and the second color corresponds to other layers adjacent to the target layer. The hole is a blind hole.

[0041] An image filtering module is used to filter out images that include the first color and the second color, wherein the central region of the image is a circular region;

[0042] The working depth determination module is used to determine the working depth of the drill tip after reaching the target layer for each image, based on the color of the circular region in the image, the region parameters, and the drill tip size parameters.

[0043] The actual thickness determination module is used to calculate the difference between the drilling depth and the working depth to obtain the actual thickness from the back drill surface to the target layer corresponding to the current image;

[0044] The average thickness calculation module is used to calculate the average thickness from the back drill surface to the target layer based on the actual thickness corresponding to all the images.

[0045] The back-drilling depth determination module is used to calculate the back-drilling depth of the PCB at the target location based on the average thickness and the preset residual pile length.

[0046] Thirdly, the present invention provides an electronic device, the electronic device comprising:

[0047] At least one processor; and

[0048] A memory communicatively connected to the at least one processor; wherein,

[0049] The memory stores a computer program that can be executed by the at least one processor, the computer program being executed by the at least one processor to enable the at least one processor to perform the PCB back-drilling depth determination method according to the first aspect of the present invention.

[0050] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions that, when executed by a processor, implement the PCB back-drilling depth determination method described in the first aspect of the present invention.

[0051] The PCB back-drilling depth determination method provided in this embodiment of the invention has the following beneficial effects:

[0052] By utilizing the correlation between drill tip size parameters and circular areas in the image, the actual thickness from the PCB back-drilled surface to the target layer can be accurately calculated, achieving non-destructive board thickness detection and improving the accuracy of back-drilling depth settings and the controllability of residual pile length.

[0053] By calculating the average thickness from the back-drilled surface to the target layer, standardized and reliable back-drilling depth reference parameters are provided for mass production, ensuring that the same back-drilling position on the same model of PCB board achieves a uniform back-drilling effect, thereby significantly improving product yield, performance consistency and production efficiency.

[0054] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 This is a schematic diagram of a residual pile provided in an embodiment of the present invention;

[0057] Figure 2 This is a flowchart of a method for determining the back-drilling depth of a PCB provided in an embodiment of the present invention;

[0058] Figure 3 This is a schematic diagram of a PCB structure provided in an embodiment of the present invention;

[0059] Figure 4 This is a schematic diagram illustrating the correspondence between an image of a first color and a second color and the working position of a drill tip, provided by an embodiment of the present invention.

[0060] Figure 5 This is a schematic diagram of a PCB back-drilling depth determination device provided in an embodiment of the present invention;

[0061] Figure 6 This is a schematic diagram of the structure of the electronic device provided in an embodiment of the present invention. Detailed Implementation

[0062] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0063] To aid in a clear understanding of the technical solution of this application, the terms used in this application are explained below:

[0064] Back drilling is a technique in printed circuit board (PCB) manufacturing that involves drilling additional holes from the back of a completed multilayer PCB to remove a portion of the material from certain placed-through holes (PTHs). This process is typically used to improve signal integrity and reduce interference in high-speed signal transmission. Below are some basic concepts of back drilling:

[0065] Through-hole (PTH): In multilayer PCBs, through-holes are structures used to connect conductive tracks between different layers. They penetrate from one side of the board to the other to achieve electrical connections between layers.

[0066] Drill Tape: A procedural document used to control CNC drilling machines to perform drilling operations. Designed for back drilling processes, it precisely removes excess copper stubs from through holes through dynamic depth control (such as laser thickness measurement or real-time feedback).

[0067] Figure 1 This is a schematic diagram of a type of residual pile, such as... Figure 1 As shown, in the traditional hole metallization process, a metal layer 1 is first formed in the through hole ( Figure 1 (Figure a) Then, the excess copper layer is removed by back drilling. Figure 1 (Figure b), but due to factors such as drilling accuracy and laminate thickness uniformity, it is impossible to completely remove excess residual copper 2 ( Figure 1 (See Figure C). This residual copper is called a residual stud. Different manufacturing standards correspond to different residual stud lengths. However, the presence of residual studs in through holes will cause problems such as PCB impedance discontinuity, signal reflection, and delay mismatch. Therefore, it is necessary to ensure the control accuracy of residual studs in the back drilling process.

[0068] The purpose of this invention is to provide the following embodiments to solve the problems of difficulty in improving the control accuracy of back drill residue and high reliability risk in the existing PCB back drill depth determination method.

[0069] This invention provides a method for determining the back drilling depth of a PCB. This embodiment is applicable to situations where the back drilling depth of a PCB needs to be controlled to ensure the accuracy of the residual pile. This method can be executed by a PCB back drilling depth determining device, which can be implemented in hardware and / or software and can be configured in an electronic device.

[0070] A PCB consists of a target layer and other layers. The target layer is the circuit layer to which the signal needs to be connected. The target layer is usually a copper layer, and the other layers adjacent to the target layer are usually dielectric layers.

[0071] Figure 2 A flowchart of a method for determining the back-drilling depth of a PCB provided in an embodiment of the present invention is shown below. Figure 2 As shown, the method for determining the PCB back-drilling depth includes:

[0072] S201. Obtain multiple borehole depths and drill tip size parameters from the back drill face to the target layer.

[0073] Figure 3 This is a schematic diagram of a PCB structure, such as... Figure 3 As shown, the PCB board includes a target layer 32, a first other layer 31 located above the target layer 32, and a third other layer 33 located below the target layer 32.

[0074] Assuming the back drill surface is the side of the first other layer 31 that is far from the target layer 32, the drilling depth from the back drill surface to the target layer is the drilling depth when drilling starts from the back drill surface and reaches the vicinity of or within the target layer 32.

[0075] The drilling depth is set as follows:

[0076] Obtain the theoretical thickness from the back drill surface to the target layer, and set multiple drilling depths from the back drill surface to the target layer based on the theoretical thickness and the preset plate thickness error range.

[0077] The theoretical thickness from the back-drilled surface to the target layer can be obtained through PCB stack-up design parameters and process parameters, such as PCB design drawings or lamination process specifications. Board thickness error refers to the PCB board thickness tolerance value. For example, if the preset board thickness error range is ±k%, and the theoretical thickness is L, then the theoretical thickness range for the drill depth corresponding to the theoretical thickness L can be obtained as L±L×k%, and multiple drill depths can be set within the theoretical thickness range.

[0078] For example, the operator can preset a set of drilling depths, which fluctuate slightly above and below the theoretical thickness. For instance, if the theoretical thickness is 1.0 mm, several depths such as 0.95 mm, 0.98 mm, 1.0 mm, 1.02 mm, and 1.05 mm might be set. By setting multiple drilling depths within the theoretical thickness of the target layer from the back drill surface and the board thickness tolerance, it is possible to ensure that the cutting tool tip detects the target layer without wasting production capacity.

[0079] Furthermore, determining the drilling depth from the back drill surface to the target layer surface based on the theoretical thickness and a preset plate thickness error range includes:

[0080] The theoretical thickness range is determined based on the theoretical thickness and the preset plate thickness error range; multiple thickness values ​​are obtained by taking values ​​at intervals within the theoretical thickness range; each thickness value is used as the drilling depth from the back drill surface to the target layer.

[0081] In one example, a unit depth can be set, and values ​​can be taken within the theoretical thickness range at intervals of this unit depth. In Example B, the theoretical thickness range is L±L×k%, and the drill tip length h can be increased progressively with the drill tip length h within the theoretical thickness range L±L×k% from the back-drilled surface to the target layer to obtain multiple drilling depths: LL×K%, LL×K%+h, LL×K%+2h…LL×K%+nh, L…L+L×K%. Multiple drill strips with different drilling depths are generated, and the same back-drilled position (i.e., the target position) of multiple circuit boards in the same batch is processed according to the different drill strips.

[0082] S202. When drilling a PCB, the drill bit is controlled to drill holes at the target positions in multiple PCBs of the same model based on each drilling depth, and the image of each hole is acquired by optical equipment.

[0083] The image includes at least one of a first color and a second color, the first color corresponds to the target layer, the second color corresponds to other layers adjacent to the target layer, and the processed holes are blind holes.

[0084] The front-end processes of back drilling mainly include drilling and hole metallization. Specifically, during drilling, a series of holes are drilled on multiple PCBs in the same batch using the same drill bit at different depths preset in the first step. After drilling, the bottom image of each hole is captured by optical equipment. Specifically, the image of the hole is obtained by scanning the hole with a high-precision optical microscope or an automated optical inspection (AOI) device.

[0085] The image includes at least one of a first color and a second color. The first color corresponds to the target layer, and the second color corresponds to other layers adjacent to the target layer. It should be noted that the first color and the second color are the colors of different PCB layers presented during AOI scanning, but not necessarily the actual colors of the PCB layers. A PCB includes a target layer and other layers adjacent to the target layer. The target layer is typically a copper layer, and the other layers adjacent to the target layer are typically dielectric layers. Due to the different materials and body colors of different PCB layers, the first color can be clearly distinguished from the second color. For example, the first color can be copper or gold, and the second color can be gray and / or black. It should also be noted that the first color is a specific color, while the second color can be one or more colors (possibly two). The above description of the specific color systems of the first and second colors is merely illustrative and not intended to limit the invention.

[0086] S203. Filter out images that include the first color and the second color, with the central area of ​​the image being a circular area.

[0087] Multiple drilling depths are set to drill holes at target locations on the same type of PCB to obtain machined holes, which are blind vias. The machined holes are then scanned using AOI to obtain machined images. If the machined image only includes the first color, it indicates that the entire drill tip is within the target layer. Since parameters (area ratio) cannot be obtained from the machined image to calculate the working depth of the drill tip, this type of image is discarded. If the image only includes the second color, it indicates that the drill bit (drill tip) has not reached the target layer or has completely drilled through the target layer. In this case, parameters (area ratio) cannot be obtained from the machined image to calculate the working depth of the drill tip, and this type of image is also discarded and not used as the basis for calculating the back-drilling depth.

[0088] The first color is the color corresponding to the target layer (signal layer), and the second color is the color corresponding to the other layers above and below the target layer. When the image includes both the first and second colors, it indicates that part of the drill tip is located in the target layer, and part of the drill tip is located in an adjacent layer of the target layer. For details, please refer to [reference needed]. Figure 4 , Figure 4 This is a schematic diagram showing the correspondence between the image (including the first and second colors) and the working position of the drill tip. Figure 4 PCB structure and Figure 3 Similarly, the PCB board includes a target layer 32, a first additional layer 31 above the target layer 32, and a third additional layer 33 below the target layer 32. Figure 4 As shown in Figures a and b, when only part of the drill tip 34 is located in the target layer 32 or only part of the drill tip 34 drills out of the target layer 32, the image 35 includes a first color and a second color. Figure 4Image 35 in Figure b includes one circle and two annexes. The central circle and the outer annexes are the same color. In this case, the drill tip 34 is divided into three parts according to its location. Each part is located in the first other layer 31, the target layer 32, and the second other layer 33, respectively. Of course, it is also possible that the drill tip 34 is divided into two parts, one part is located in the target layer 32, and the other part is located in the second other layer 33 below the target layer 32. In this case, the image will only include one circle and one annexes. The circle is the second color, and the annexes are the first color. However, this solution focuses on the depth to which the drill tip 34 penetrates the target layer 32 or exceeds the top of the target layer 32. This top corresponds only to the circular area in image 35. Therefore, the number of annexes in image 35 does not affect the calculation of the depth of the top of the drill tip 34.

[0089] It should be noted that the drill bit is inserted vertically into the PCB, therefore, as Figure 4 As shown, the central region of image 35 is a circular region, and the outer layer of the circular region is a ring.

[0090] S204. For each image, determine the working depth of the drill tip after reaching the target layer based on the color of the circular area in the image, the area parameters, and the drill tip size parameters.

[0091] The geometry of the drill tip is crucial. Since the maximum cross-section of the drill tip is triangular, the working range during one rotation is a cone. In one scenario, when the drill tip just touches the target layer (copper plating), a copper-colored circular area will appear at the center of the image.

[0092] The region parameters (region size, etc.) of this copper-colored circular area have a mathematical relationship with the geometry of the drill tip penetrating the target layer. Therefore, the working depth of the drill tip after reaching the target layer can be determined based on the region parameters of the circular area and the drill tip size parameters. For example, the drill tip size parameters include the drill tip angle, and the diameter of the circular area is the maximum diameter of the drill tip penetrating the target layer at this point. Knowing the maximum diameter and the drill tip angle, it is possible to deduce the length of the drill tip (i.e., the working depth) that has penetrated into the target layer.

[0093] In another scenario, when the drill tip just breaks through the target layer, a gray (or other color) circular area will appear at the center of the image. The area parameters of this gray circular area are also mathematically related to the geometry of the drill tip. Similarly, we can deduce how much length of the drill tip has broken through the copper layer. Adding this to the thickness of the target layer, we can obtain the working depth.

[0094] S205. Calculate the difference between the drilling depth and the working depth to obtain the actual thickness from the back drill surface to the target layer corresponding to the current image.

[0095] The actual thickness from the back face to the target layer is the difference between the borehole depth and the working depth. An actual thickness can be calculated for each image.

[0096] S206. Calculate the average thickness from the back drill surface to the target layer based on the actual thickness corresponding to all images.

[0097] The average thickness from the back-drilled surface to the target layer is crucial for setting the back-drilling depth during mass production. Uneven adhesive flow in PCB lamination leads to dielectric layer thickness deviations, affecting board thickness uniformity. Knowing the actual thickness from the back-drilled surface to the target layer is essential for accurate drilling, preventing insufficient drilling depth (excessively long residual holes) or excessive drilling depth (damage to the target signal layer). In this step, the average actual thickness corresponding to all images is calculated to obtain the average thickness from the back-drilled surface to the target layer. This average thickness is representative and can represent the thickness from the back-drilled surface to the target layer in most PCBs of the same model, improving drilling accuracy and reducing the defect rate.

[0098] S207. Calculate the back-drilling depth when back-drilling the PCB at the target location based on the average thickness and the preset residual pile length.

[0099] The preset residual pile length is a small residual pile section that the process engineer (or customer) proactively designs and allows to be retained based on signal integrity requirements. The back-drilling depth is the final depth value input into the machining program of the back-drilling machine. It indicates the final position the drill bit reaches from the back-drilling face, a position slightly shallower than the point where it just touches the target layer. That is, back-drilling depth = average thickness - preset residual pile length. For example, if the measured average thickness is 1.00 mm and the preset residual pile length is 0.05 mm according to signal requirements, then the back-drilling depth = 1.00 mm - 0.05 mm = 0.05 mm.

[0100] Since the average thickness is obtained based on the drilling results of multiple PCBs, it can represent the thickness from the back drill surface to the target layer of the target back drill position on most PCBs. Therefore, when calculating the back drill depth and performing back drills based on this, the length of the residual pile can be precisely controlled, avoiding the residual pile being too long or too short, thus improving the product yield.

[0101] In an optional embodiment, the step of calculating the back-drilling depth of the PCB at the target location based on the average thickness and the preset residual pile length includes: calculating the sum of the average thickness and the preset compensation drilling depth to obtain the total drilling depth; and calculating the difference between the total drilling depth and the preset residual pile length to obtain the back-drilling depth of the PCB at the target location.

[0102] The preset compensation drilling depth includes compensation for electroplated copper thickness, compensation depth for back drill bit tip angle, and aluminum sheet thickness.

[0103] The PCB back-drilling depth determination method provided in this embodiment of the invention has the following beneficial effects:

[0104] By leveraging the correlation between drill tip size parameters and circular regions in the image, the actual thickness from the PCB back-drilled surface to the target layer can be accurately calculated, enabling non-destructive board thickness detection. This improves the accuracy of back-drilling depth settings and the controllability of residual pile length.

[0105] By calculating the average thickness from the back-drilled surface to the target layer, standardized and reliable back-drilling depth benchmark parameters are provided for mass production, ensuring that the same back-drilling position on the same model of PCB board achieves a uniform back-drilling effect, thereby significantly improving product yield, performance consistency and production efficiency.

[0106] In an optional embodiment, for each image, the working depth of the drill tip after reaching the target layer is determined based on the color, area ratio, and drill tip size parameters of the circular region in the image, including: for each image, determining the relative position of the current drill tip to the target layer based on the color of the circular region in the image; and determining the working depth of the drill tip after reaching the target layer based on the relative position, the area parameters of the circular region in the image, and the drill tip size parameters.

[0107] Specifically, the relative position of the current drill tip to the target layer is determined based on the color of the circular region in the image, including:

[0108] If the circular region in the image is the first color, then the relative position of the current drill tip to the target layer is determined to be that part of the drill tip has reached the target layer; for details, please refer to... Figure 4 In Figure a, if the circular region 351 in image 35 is colored with the first color (copper), then the relative position of the current drill tip and the target layer 32 can be determined to be that part of the drill tip has reached the target layer 32.

[0109] If the circular area in the image is the second color, then the relative position of the current drill tip to the target layer is determined to be that the drill tip has partially penetrated the target layer. For details, please refer to... Figure 4 In Figure b, if the circular region 351 in image 35 is colored with the second color (gray), then the relative position of the current drill tip and the target layer 32 is determined to be that part of the drill tip passes through the target layer 32.

[0110] Based on the relative position, the regional parameters of the circular area in the image, and the drill tip size parameters, the working depth of the drill tip after reaching the target layer is determined, specifically including:

[0111] Based on the region parameters of the circular region in the image and the drill tip size parameters, calculate the drill tip length corresponding to the circular region;

[0112] If the relative position indicates that part of the drill tip has reached the target layer, then the drill tip length is taken as the working depth of the drill tip after reaching the target layer; for example... Figure 4 As shown in Figure a, at this time, part of the drill tip reaches the target layer 32, and the working depth of the drill tip after reaching the target layer 32 is h1.

[0113] If the relative position represents a portion of the drill tip passing through the target layer, then the sum of the drill tip length and the known thickness of the target layer is calculated to obtain the working depth of the drill tip after reaching the target layer. For example... Figure 4 As shown in Figure b, at this point, part of the drill tip reaches the target layer 32. The working depth of the tip after reaching the target layer 32 is the sum of h1 and the thickness of the target layer.

[0114] In an optional embodiment, the drill tip size parameter includes the drill tip length, the region parameter of the circular region includes the area percentage of the circular region, and the drill tip length corresponding to the circular region is calculated as follows:

[0115] h1 = h × (S1 / S) 1 / 2 ;

[0116] Where h1 is the drill tip length corresponding to the circular region, h is the drill tip length, S1 / S is the area ratio; S1 is the area of ​​the circular region in the image, and S is the area of ​​the image.

[0117] AOI equipment can perform image analysis to obtain the area ratio of circular regions in the image, that is, the area ratio of circular regions in the entire image. The drill tip length h is an inherent parameter of the drill bit and can be obtained in advance. Therefore, the drill tip length corresponding to the circular region can be calculated according to the above calculation method.

[0118] The derivation of this formula is as follows:

[0119] Please refer to Figure 4 Figure a in the middle,

[0120] The area of ​​the circular region 351 is: S1 = π (h1 / tan((180°-β) / 2)) 2 β is the drill bit tip angle;

[0121] The area of ​​image 35 is: S = π (h / tan((180°-β) / 2)) 2 ;

[0122] AOI has a function to detect area percentage, which is a percentage area, denoted as A%, then:

[0123] A% = S1 / S;

[0124] A%=(π (h1 / tan((180°-β) / 2)) 2 ) / (π (h / tan((180°-β) / 2)) 2 ;

[0125] A%=h1 2 / h 2 ;

[0126] h1=h (A%) 1 / 2 ;

[0127] The working depth h1 is linearly proportional to the drill tip length h and the square root of the area ratio A%. h is fixed, and A% is detected, so the value of h1 can be calculated.

[0128] This method allows for the rapid calculation of the drill tip length corresponding to a circular region.

[0129] In an optional embodiment, after acquiring an image of each machined hole using an optical device, the method further includes:

[0130] A second drilling is performed at the target location to obtain a through hole, thus completing the first drilling process.

[0131] Since the first drilling at the target location produces a blind hole, and the first drilling operation aims to create a through hole at the target location, after acquiring an image of the hole to measure the actual thickness from the back drill surface to the target layer, a second drilling operation is required at the target location to obtain a through hole in order to complete the first drilling operation.

[0132] In an optional embodiment, the diameter of the drill bit used during the secondary drilling is the target diameter of the first drilling operation, while the diameter of the drill bit used during the initial drilling at the target location is smaller than the target diameter.

[0133] If the drill bit used in both the first and second drilling operations is the target diameter for the first drilling operation, the inherent precision errors in the drilling process will lead to a cumulative error effect when drilling twice at the same target location. This increases the total error of the through hole, resulting in a decrease in the final accuracy of the machined through hole. For example, it may cause the hole diameter to exceed tolerances or the hole's roundness to fail to meet standards. Therefore, this embodiment uses a drill bit smaller than the target diameter for the first drilling operation, and only uses the target diameter drill bit for the second drilling operation. This allows for obtaining the actual thickness from the back drill surface to the target layer without affecting the drilling accuracy of the through hole during the first drilling operation.

[0134] To clearly illustrate the PCB back-drilling depth determination method of this solution, we will now explain its application in the actual back-drilling process using an example. The PCB back-drilling depth determination method mainly includes the following steps:

[0135] 1. Obtain the laminated circuit board;

[0136] 2. Drilling Process: Obtaining the back-drilling depth (the actual depth from the target layer to the back-drilling surface) during the drilling process, the specific process is as follows;

[0137] ① Obtain the theoretical thickness L from the back drill surface to the target layer surface and the thickness tolerance value ±k% of the lamination plate. Then, the theoretical thickness range from the back drill surface to the target layer is L ± L × k%.

[0138] ② Obtain information about a drilling tool used for drilling, including tool diameter d, tool tip angle β, and drill tip length h;

[0139] ③ Within the theoretical thickness range from the back-drilled surface to the target layer, the drilling depth is progressively determined by the drill tip length h, i.e., drilling depth: LL×K%, LL×K%+h, LL×K%+2h…LL×K%+nh…L+L×K%, generating multiple drill strips with different drilling depths. Based on the different drill strips, the same back-drilled positions on multiple circuit boards in the same batch are processed.

[0140] ④ After processing, the machined hole position is scanned using an automated optical instrument (AOI) to obtain the scanned image of the machined hole position. The image is judged to calculate the actual thickness from the back drill surface to the target layer. When the circular hole position image is completely gray-black (i.e., the second color), it is judged that the target layer has not been drilled or the target layer has been completely drilled through, and the image is removed. When the AOI scan shows copper color (i.e., the first color) and gray-black, if the copper color appears in the center, it is judged that the target layer has been drilled through. If the gray-black appears in the center, it is judged that the target layer has been drilled through, but not completely.

[0141] ⑤ If copper color appears in the scanned image, obtain the area ratio A% of the two concentric circles in the AOI scanned image. A% = S1 / S = (π(h1 / / tan((180°-β) / 2)) 2 ) / (π(h / tan((180°-β) / 2)) 2 That is, A%=h1 2 / h 2 That is, h1 = h × (A%) 1 / 2 ;

[0142] When copper appears in the center of the scanned image, it is determined that the target layer has been reached. The drilling depth H1 (drilling depth) of the corresponding drill strip in this image is then obtained. At this point, the actual depth from the back drill face to the target layer (surface) is L1 = H1 - h × (A1%). 1 / 2 ;

[0143] When a grayish-black color appears in the center of the scanned image, it is determined that the target layer has been penetrated, but not completely. The drilling depth H2 corresponding to this image is then obtained. The depth from the back drill face to the target layer (surface) is then calculated as L2 = H2 - h × (A2%). 1 / 2 -Mt, where Mt is the thickness of the target layer.

[0144] Calculate the average thickness from the back drill face to the target layer for all images, and obtain the depth from the back drill face to the target layer LA = (L1+L2+……+Ln) / n.

[0145] 3. Complete one drilling process: drill through, deburr, and plasma degumming (remove drilling adhesive residue);

[0146] 4. Hole metallization: copper plating, electroplating;

[0147] 5. Back Drilling: Based on the depth from the back drill surface to the target layer and the actual drilling depth compensation value obtained above, determine the back drill depth and complete the back drill processing. The electroplated copper thickness (K1), back drill bit tip angle compensation (K2), and aluminum sheet thickness (K3) are set. The corrected back drill depth P = L + K1 + K2 + K3 - STUB is then set to obtain a relatively high-precision back drill STUB (residual pile).

[0148] The PCB back-drilling depth determination method of this application sets a progressive drilling depth during drilling, allowing the drill bit to reach the target layer. It then uses an automated optical inspection (AOI) device to scan and acquire an image of the drill hole location, determines the state of the drill bit reaching the target layer, and quickly calculates the back-drilling depth of the target drill hole location using the area ratio of concentric circles in the drill hole location image, the drill bit tip angle, and the drill bit diameter. This improves back-drilling accuracy, reduces the length of residual piles in the back-drilling process, and enhances the quality of back-drilling.

[0149] Corresponding to the above-described method for determining the PCB back-drilling depth, this embodiment of the invention also provides a device for determining the PCB back-drilling depth. Figure 5 This is a schematic diagram of a PCB back-drilling depth determination device provided in an embodiment of the present invention. Figure 5 As shown, the PCB back-drilling depth determination device includes:

[0150] A PCB includes a target layer and other layers. The target layer is the circuit layer to which signals need to be connected.

[0151] The device includes:

[0152] The basic data acquisition module 501 is used to acquire multiple borehole depths and drill tip size parameters from the back drill face to the target layer;

[0153] The drilling image acquisition module 502 is used to control the drill bit to drill holes at target positions in multiple PCBs of the same model based on each drilling depth when drilling a PCB, and to acquire an image of each of the processed holes through an optical device. The image includes at least one of a first color and a second color, the first color corresponds to the target layer, the second color corresponds to other layers adjacent to the target layer, and the processed hole is a blind hole.

[0154] Image filtering module 503 is used to filter out images that include the first color and the second color, wherein the central area of ​​the image is a circular area;

[0155] The working depth determination module 504 is used to determine the working depth of the drill tip after reaching the target layer for each image, based on the color of the circular region in the image, the region parameters, and the drill tip size parameters.

[0156] The actual thickness determination module 505 is used to calculate the difference between the drilling depth and the working depth to obtain the actual thickness from the back drilling surface to the target layer corresponding to the current image.

[0157] The average thickness calculation module 506 is used to calculate the average thickness from the back drill surface to the target layer based on the actual thickness corresponding to all the images.

[0158] The back-drilling depth determination module 507 is used to calculate the back-drilling depth of the PCB at the target location based on the average thickness and the preset residual pile length.

[0159] Optionally, the drilling depth can be set as follows:

[0160] Obtain the theoretical thickness from the back drill face to the target layer;

[0161] Based on the theoretical thickness and the preset plate thickness error range, multiple drilling depths from the back drilling surface to the target layer are set.

[0162] Optionally, the operation depth determination module 504 includes:

[0163] The relative position determination submodule is used to determine the relative position of the current drill tip and the target layer for each image based on the color of the circular region in the image.

[0164] The working depth determination submodule is used to determine the working depth of the drill tip after reaching the target layer based on the relative position, the region parameters of the circular area in the image, and the drill tip size parameters.

[0165] Optionally, the relative position determination submodule is used for:

[0166] If the color of the circular region in the image is the first color, then the relative position of the current drill tip and the target layer is determined to be that part of the drill tip has reached the target layer;

[0167] If the color of the circular region in the image is the second color, then the relative position of the current drill tip and the target layer is determined to be that the drill tip has partially passed through the target layer.

[0168] Optionally, the operation depth determination submodule is used for:

[0169] Based on the region parameters of the circular region in the image and the drill tip size parameters, calculate the drill tip length corresponding to the circular region;

[0170] If the relative position is such that part of the drill tip reaches the target layer, then the drill tip length is taken as the working depth of the drill tip after reaching the target layer;

[0171] If the relative position is such that part of the drill tip passes through the target layer, then the sum of the drill tip length and the known thickness of the target layer is calculated to obtain the working depth of the drill tip after reaching the target layer.

[0172] Optionally, the drill tip size parameters include the drill tip length, the region parameters of the circular region include the area ratio of the circular region, and the drill tip length corresponding to the circular region is calculated as follows:

[0173] h1 = h × (S1 / S) 1 / 2 ;

[0174] Where h1 is the drill tip length corresponding to the circular region, h is the drill tip length, S1 / S is the area ratio; S1 is the area of ​​the circular region in the image, and S is the area of ​​the image.

[0175] Optionally, the back-drilling depth determination module 507 is used for:

[0176] The total drilling depth is obtained by summing the average thickness with the preset compensated drilling depth.

[0177] The difference between the total drilling depth and the preset residual pile length is calculated to obtain the back drilling depth when back drilling is performed on the PCB at the target location.

[0178] Optionally, the PCB back-drilling depth determination device also includes:

[0179] The secondary processing module is used to perform secondary drilling on each of the processing holes to obtain through holes, thereby completing one drilling process.

[0180] Optionally, the diameter of the drill bit used in the secondary drilling is the target diameter of the drilling process, and the diameter of the drill bit used in the first drilling of the hole is smaller than the target diameter.

[0181] The PCB back-drilling depth determination device provided in the embodiments of the present invention can execute the PCB back-drilling depth determination method provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the method.

[0182] Figure 6 A schematic diagram of an electronic device 40 that can be used to implement embodiments of the present invention is shown. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processors and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the invention described and / or claimed herein.

[0183] like Figure 6 As shown, the electronic device 40 includes at least one processor 41 and a memory, such as a read-only memory (ROM) 42 or a random access memory (RAM) 43, communicatively connected to the at least one processor 41. The memory stores computer programs executable by the at least one processor. The processor 41 can perform various appropriate actions and processes based on the computer program stored in the ROM 42 or loaded from storage unit 48 into the RAM 43. The RAM 43 may also store various programs and data required for the operation of the electronic device 40. The processor 41, ROM 42, and RAM 43 are interconnected via a bus 44. An input / output (I / O) interface 45 is also connected to the bus 44.

[0184] Multiple components in electronic device 40 are connected to I / O interface 45, including: input unit 46, such as keyboard, mouse, etc.; output unit 47; storage unit 48, such as disk, optical disk, etc.; and communication unit 49. Communication unit 49 allows electronic device 40 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0185] Processor 41 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of processor 41 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, a digital signal processor (DSP), and any suitable processor, controller, microcontroller, etc. Processor 41 performs the various methods and processes described above, such as the PCB back-drilling depth determination method.

[0186] In some embodiments, the PCB back-drilling depth determination method may be implemented as a computer program tangibly contained in a computer-readable storage medium, such as storage unit 48. In some embodiments, part or all of the computer program may be loaded and / or mounted on electronic device 40 via ROM 42 and / or communication unit 49. When the computer program is loaded into RAM 43 and executed by processor 41, one or more steps of the PCB back-drilling depth determination method described above may be performed. Alternatively, in other embodiments, processor 41 may be configured to perform the PCB back-drilling depth determination method by any other suitable means (e.g., by means of firmware).

[0187] Various embodiments of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), systems-on-a-chip (SoCs), complex programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include implementations in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which may be a dedicated or general-purpose programmable processor, capable of receiving data and instructions from a storage system, at least one input device, and at least one output device, and transferring data and instructions to the storage system, the at least one input device, and the at least one output device.

[0188] Computer programs used to implement the methods of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, such that when executed by the processor, the computer programs cause the functions / operations specified in the flowcharts and / or block diagrams to be performed. The computer programs may be executed entirely on a machine, partially on a machine, or as a standalone software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0189] In the context of this invention, a computer-readable storage medium can be a tangible medium that may contain or store a computer program for use by or in conjunction with an instruction execution system, apparatus, or device. A computer-readable storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination thereof. Alternatively, a computer-readable storage medium may be a machine-readable signal medium. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0190] To provide interaction with a user, the systems and techniques described herein can be implemented on an electronic device having: a display device for displaying information to a user (e.g., a monitor with a cathode ray tube or liquid crystal display); and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the electronic device.

[0191] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as data servers), or middleware components (e.g., application servers), or frontend components (e.g., user computers with graphical user interfaces or web browsers through which users can interact with implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., communication networks). Examples of communication networks include local area networks (LANs), wide area networks (WANs), blockchain networks, and the Internet.

[0192] A computing system may include clients and servers. Clients and servers are generally located far apart and typically interact through a communication network. The client-server relationship is created by computer programs running on the respective computers and having a client-server relationship with each other.

[0193] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0194] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for determining the depth of back drilling on a PCB, characterized in that, The PCB includes a target layer and other layers, wherein the target layer is the circuit layer to which the signal needs to be connected; The method includes: Obtain multiple borehole depths and drill tip size parameters from the back drill face to the target layer; When drilling a PCB, the drill bit is controlled to drill holes at target positions in multiple PCBs of the same model based on each drilling depth to obtain the processed holes. An image of each processed hole is acquired by an optical device. The image includes at least one of a first color and a second color. The first color corresponds to the target layer, and the second color corresponds to other layers adjacent to the target layer. The processed hole is a blind hole. The images that include the first color and the second color are selected, and the central region of the images is a circular region; For each image, the working depth of the drill tip after reaching the target layer is determined based on the color of the circular region in the image, the region parameters, and the drill tip size parameters. Calculate the difference between the drilling depth and the working depth to obtain the actual thickness from the back drill surface to the target layer corresponding to the current image; Calculate the average thickness from the back drill surface to the target layer based on the actual thickness corresponding to all the images; The back-drilling depth is calculated based on the average thickness and the preset residual pile length when back-drilling the PCB at the target location.

2. The method as described in claim 1, characterized in that, The drilling depth is set as follows: Obtain the theoretical thickness from the back drill face to the target layer; Based on the theoretical thickness and the preset plate thickness error range, multiple drilling depths from the back drilling surface to the target layer are set.

3. The method as described in claim 1, characterized in that, For each image, determining the working depth of the drill tip after reaching the target layer based on the color, region parameters, and drill tip size parameters of the circular region in the image includes: For each image, the relative position of the current drill tip to the target layer is determined based on the color of the circular region in the image; The working depth of the drill tip after reaching the target layer is determined based on the relative position, the region parameters of the circular area in the image, and the drill tip size parameters.

4. The method as described in claim 3, characterized in that, Determining the relative position of the current drill tip to the target layer based on the color of the circular region in the image includes: If the color of the circular region in the image is the first color, then the relative position of the current drill tip and the target layer is determined to be that part of the drill tip has reached the target layer; If the color of the circular region in the image is the second color, then the relative position of the current drill tip and the target layer is determined to be that the drill tip has partially passed through the target layer.

5. The method as described in claim 4, characterized in that, Determining the working depth of the drill tip after reaching the target layer based on the relative position, the region parameters of the circular area in the image, and the drill tip size parameters includes: Based on the region parameters of the circular region in the image and the drill tip size parameters, calculate the drill tip length corresponding to the circular region; If the relative position is such that part of the drill tip reaches the target layer, then the drill tip length is taken as the working depth of the drill tip after reaching the target layer; If the relative position is such that part of the drill tip passes through the target layer, then the sum of the drill tip length and the known thickness of the target layer is calculated to obtain the working depth of the drill tip after reaching the target layer.

6. The method as described in claim 4, characterized in that, The drill tip size parameters include the drill tip length, and the region parameters of the circular region include the area percentage of the circular region. The drill tip length corresponding to the circular region is calculated as follows: h1= h×(S1 / S) 1 / 2 ; Where h1 is the drill tip length corresponding to the circular region, h is the drill tip length, S1 / S is the area ratio; S1 is the area of ​​the circular region in the image, and S is the area of ​​the image.

7. The method according to any one of claims 1-6, characterized in that, The calculation of the back-drilling depth at the target location for back-drilling based on the average thickness and the preset residual pile length includes: The total drilling depth is obtained by summing the average thickness with the preset compensated drilling depth. The difference between the total drilling depth and the preset residual pile length is calculated to obtain the back drilling depth when back drilling is performed on the PCB at the target location.

8. The method according to any one of claims 1-6, characterized in that, After acquiring an image of each of the processed holes using an optical device, the process further includes: A second drilling is performed at the target location to obtain a through hole, thus completing one drilling operation.

9. The method as described in claim 8, characterized in that, The diameter of the drill bit used in the secondary drilling is the target diameter of the first drilling operation, while the diameter of the drill bit used in the first drilling at the target position is smaller than the target diameter.

10. An electronic device, characterized in that, The electronic device includes: At least one processor; and A memory communicatively connected to the at least one processor; wherein, The memory stores a computer program that can be executed by the at least one processor, the computer program being executed by the at least one processor to enable the at least one processor to perform the PCB back-drilling depth determination method according to any one of claims 1-9.

Images