Processing system, method of determining back drill depth, back drill method and circuit board

Abstract

This application provides a processing system, a method for determining back-drilling depth, a back-drilling method, and a circuit board. It adopts a dual-loop separate detection design, with the first detection loop dedicated to detecting surface layer signals and the second detection loop dedicated to detecting inner reference layer signals. This breaks the traditional single-loop shared triggering mode, completely avoiding false signal abrupt changes caused by drill debris and drill bit side impacts. It eliminates the problem of mis-detection of inner reference layers from the root, ensures the authenticity of layer detection, and thus provides a reliable benchmark for back-drilling depth measurement, reduces stub value control errors, and improves the quality of the circuit board.

Description

Technical Field

[0001] This application belongs to the field of circuit board processing technology, and particularly relates to a processing system, a method for determining back drilling depth, a back drilling method, and a circuit board. Background Technology

[0002] In the field of printed circuit board (PCB) manufacturing, to reduce interlayer signal interference and ensure high-speed signal transmission, the industry uses back-drilling (controlled depth drilling) to remove excess copper walls. The length of the remaining copper wall is called the stub value. With the upgrading of high-end PCB processes, stub value control has become increasingly stringent. Traditional back-drilling is insufficient in precision. To improve back-drilling accuracy, related technologies calculate the interlayer thickness by measuring signal abrupt changes when the drill bit contacts the surface layer and the inner reference layer, thus calculating the back-drilling depth. However, copper wires, board debris, and drill bit side contact with the hole wall generated during drilling can easily trigger false signals, causing false triggering of the inner reference layer and resulting in distorted layer thickness calculations. This leads to deviations in the back-drilling depth compensation benchmark, failure of stub value control, and problems such as excessive residue or damage to the target layer, making it difficult to meet the requirements of high-precision back-drilling production. Summary of the Invention

[0003] In view of this, embodiments of this application provide a processing system, a method for determining back-drilling depth, a back-drilling method, and a circuit board, which can avoid false triggering signals caused by wire chips or drill bit side impacts when probing the reference layer, and realize the separation of the surface layer and the reference layer for detection, thereby improving the calculated back-drilling depth.

[0004] In a first aspect, embodiments of this application provide a processing system, including: spindle; A switching device, one end of which is electrically connected to the main spindle; The other end of the switching device is connected to the first detection circuit and the second detection circuit respectively. The switching device is used to electrically connect the spindle to the first detection circuit or the second detection circuit. During the process of the spindle driving the drill bit to drill a hole in the circuit board, the first detection circuit is used to detect the first electrical signal generated when the drill bit contacts the surface layer of the circuit board, and the second detection circuit is used to detect the second electrical signal generated when the drill bit contacts the reference layer of the circuit board. The machining system can be used to determine the back-drilling depth based on the first electrical signal and the second electrical signal.

[0005] In some embodiments, the processing system further includes: A power supply device for applying voltage to the reference layer; A controller, connected to the first detection circuit and the second detection circuit, is used to determine the back-drilling depth based on the first electrical signal and the second electrical signal.

[0006] In some embodiments, the power supply device includes a contact device and a power source, the contact device being used to maintain electrical contact with the reference layer, and the power source being used to provide a preset voltage to the contact device to apply the preset voltage to the reference layer.

[0007] In some embodiments, the contact device includes a resilient contact device.

[0008] In some embodiments, the circuit board includes at least one surface layer and at least one reference layer. A window is provided in a predetermined area on the surface layer, and an electrical contact hole is provided at a predetermined position on the circuit board. The electrical contact hole communicates with the window on the surface layer, and an electrical contact point of the reference layer is disposed on the electrical contact hole. The contact device forms an electrical connection with the reference layer through the electrical contact hole.

[0009] In some embodiments, the distance between the preset position and the edge of the circuit board is less than a preset distance.

[0010] In some embodiments, the first detection circuit includes a capacitor and a first detection module. One end of the capacitor is connected to the switching device, and the other end of the capacitor is connected to the first detection module. When the drill bit contacts the surface layer of the circuit board, the capacitance value of the capacitor changes more than a change threshold. The first detection module detects a first electrical signal generated when the drill bit contacts the surface layer of the circuit board. The second detection circuit includes a current detection module for detecting current information when the drill bit contacts the reference layer. When the spindle is connected to the second detection circuit, the spindle is grounded.

[0011] In a second aspect, embodiments of this application provide a method for determining back-drilling depth, applied to the machining system described in any one of the first aspects, comprising: The first electrical signal generated when the drill bit contacts the surface layer of the circuit board is obtained based on the first detection circuit, and the position of the surface layer is determined based on the first electrical signal. The switching device is controlled to switch so that the main shaft is connected to the second detection circuit; The second electrical signal generated when the drill bit contacts the reference layer is obtained based on the second detection circuit, and the position of the reference layer is determined based on the second electrical signal, wherein a voltage is applied to the reference layer; The back-drilling depth is determined based on the position of the surface layer and the position of the reference layer.

[0012] In some embodiments, determining the back-drilling depth based on the position of the surface layer and the position of the reference layer includes: Based on the position of the surface layer and the position of the reference layer, determine the actual distance between the surface layer and the reference layer; The positional deviation is determined based on the actual distance and the theoretical distance between the surface layer and the reference layer; The back-drilling depth is obtained based on the positional deviation and the theoretical depth value.

[0013] In some embodiments, the method further includes: Control the power supply device to apply voltage to the reference layer.

[0014] Thirdly, embodiments of this application provide a back-drilling method, including: The back-drilling depth obtained by the method for determining back-drilling depth as described in any of the second aspects; The circuit board is back-drilled based on the stated back-drilling depth.

[0015] Fourthly, embodiments of this application provide a circuit board manufactured using the back-drilling method described in the third aspect. The circuit board includes at least one surface layer and at least one reference layer. A window is provided in a predetermined area on the surface layer, and an electrical contact hole is provided at a predetermined position on the circuit board. The electrical contact hole communicates with the window on the surface layer, and the electrical contact point of the reference layer is disposed on the electrical contact hole.

[0016] The beneficial effects of the embodiments in this application compared with the prior art are: The processing system, method for determining back-drilling depth, back-drilling method, and circuit board provided in this application adopt a dual-detection loop separate detection design. The first detection loop is dedicated to detecting the surface layer signal, and the second detection loop is dedicated to detecting the inner reference layer signal. This breaks the traditional single-loop shared triggering mode, completely avoids false signal abrupt changes caused by drill debris and drill bit side impact, eliminates the problem of mis-detection of the inner reference layer from the root, ensures the authenticity of layer detection, thereby providing a reliable benchmark for back-drilling depth measurement, reducing stub value control error, and thus improving the quality of the circuit board. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a processing system provided in an embodiment of this application; Figure 2 A schematic diagram of a circuit board structure provided in an embodiment of this application; Figure 3 A schematic diagram of an electrical contact point provided in an embodiment of this application; Figure 4 This is a schematic diagram illustrating the arrangement of a contact device according to an embodiment of this application; Figure 5 A schematic diagram illustrating the implementation process of a method for determining back-drilling depth provided for the purposes of this application; Figure 6 A schematic flowchart illustrating a detection loop triggering timing provided in an embodiment of this application; Figure 7 This is a schematic diagram of a signal switching process provided in an embodiment of this application; Figure 8 This is a schematic diagram illustrating the implementation process of a back-drilling method provided in an embodiment of this application. Detailed Implementation

[0019] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0020] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0021] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0022] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrases "if determined" or "if detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once detected," or "in response to detection."

[0023] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0024] References to "one embodiment" or "some embodiments" in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized.

[0025] Based on the problems in related technologies, embodiments of this application provide a processing system. Figure 1 This is a schematic diagram of the structure of a processing system provided in an embodiment of this application, such as... Figure 1 The device includes: a spindle for mounting a drill bit; a switching device, one end of which is electrically connected to the spindle; a first detection circuit and a second detection circuit, the other end of which is connected to the first detection circuit and the second detection circuit respectively. The switching device is used to electrically connect the spindle to the first detection circuit or the second detection circuit. The first detection circuit is used to detect a first electrical signal generated when the drill bit contacts the surface layer of the circuit board, and the second detection circuit is used to detect a second electrical signal generated when the drill bit contacts the reference layer of the circuit board.

[0026] In this embodiment, the spindle is the core rotating component of the processing equipment, used to clamp and fix the drill bit, driving the drill bit to rotate at high speed to complete PCB drilling and back drilling operations. The spindle body is made of conductive metal material, serving the dual function of drill bit driving and electrical signal transmission. It can be used in conjunction with the detection circuit to realize electrical signal transmission, providing a hardware carrier for layer detection.

[0027] In this embodiment, the switching device is an electrically controlled signal switching switch, responsible for switching the electrical connection between the spindle and the two detection circuits. It is the core control component for the independent operation of the dual circuits. One end is stably electrically connected to the spindle, and the other end is synchronously connected to the first and second detection circuits. The switching device receives instructions and executes actions, connecting only one circuit at a time. When switching to the second detection circuit, the spindle grounding action is triggered simultaneously.

[0028] In this embodiment, the first detection circuit is an independent detection circuit based on the principle of capacitance detection, dedicated to the layer positioning of the copper foil on the PCB surface, and belongs to the non-contact signal detection circuit. The first detection circuit forms a variable capacitor with the drill bit as the positive plate and the PCB surface copper foil as the negative plate. When the drill bit approaches the surface, the capacitance value changes abruptly, the circuit captures this electrical signal and transmits it to the controller to lock the Z-axis coordinate of the surface. The first detection circuit completes the surface positioning, does not participate in the inner layer detection, and is not affected by drill debris or side impacts from the hole wall, ensuring the uniqueness and accuracy of the surface positioning signal.

[0029] In this embodiment, the second detection circuit is an independent current detection circuit based on the voltage conduction principle, dedicated to layer positioning of the reference layer within the PCB, and belongs to the contact-type conduction detection circuit. When the spindle switches to this circuit, it is automatically grounded. Combined with the stable voltage applied to the reference layer, a closed current loop is formed the moment the drill bit contacts the reference layer. After detecting the current signal, the circuit transmits it to the processing system to lock the Z-axis coordinate of the reference layer. The second detection circuit uses conduction-type detection logic, triggering a signal only when the drill bit actually contacts the reference layer, completely avoiding false signals caused by debris and side impacts, and eliminating false triggering of inner layers.

[0030] The working principle of the machining system provided in this application embodiment is as follows: The switching device connects the spindle to the first detection circuit, and the spindle is in a non-grounded state; the drill bit moves down, the first detection circuit captures the capacitance change signal, and the controller records the surface coordinates; the switching device is controlled to operate, the spindle disconnects the first detection circuit and connects the second detection circuit, and the spindle is grounded at this time; pressure is applied to the reference layer, and the second detection circuit is turned on when the drill bit contacts the reference layer, and the machining system records the reference layer coordinates; the machining system combines the dual coordinate data to complete the deviation compensation and determine the final back drilling depth.

[0031] The processing system provided in this application adopts a dual-loop separate detection design. The first detection loop is dedicated to detecting the first electrical signal of the surface layer, and the second detection loop is dedicated to detecting the second electrical signal of the inner reference layer. This breaks the traditional single-loop shared triggering mode, completely avoids false signal abrupt changes caused by drilling debris and drill bit side impacts, eliminates the problem of false detection of the inner reference layer from the root, ensures the authenticity of layer detection, thereby providing a reliable benchmark for back-drilling depth measurement, reducing the error of stub value control, and thus improving the quality of the circuit board.

[0032] In some embodiments, see continue to see Figure 1 The processing system also includes: A power supply device is used to apply voltage to the reference layer; a controller is connected to the first detection circuit and the second detection circuit and is used to determine the back-drilling depth based on the first electrical signal and the second electrical signal.

[0033] In this embodiment, the power supply device, which provides a stable voltage to the inner reference layer, is a prerequisite component for the second detection circuit to achieve continuity detection. The power supply device can be paired with a flexible contact head (such as a mushroom-shaped probe) to reliably make electrical contact with the window of the reference layer lead on the PCB edge, outputting a constant preset voltage to ensure signal stability when the circuit is conducting. The power supply device provides a stable voltage reference for inner layer detection, ensuring accurate current signal triggering and eliminating detection errors caused by voltage fluctuations.

[0034] The controller is the core computing and control unit of the system, responsible for receiving detection signals, controlling switching actions, and calculating back-drilling depth. The controller can acquire electrical signals from the first and second detection loops in real time, locking the coordinates of the surface layer and reference layer respectively. Combined with the theoretical thickness, it calculates the deviation compensation value and ultimately outputs accurate back-drilling depth parameters. The controller integrates and processes the dual-loop detection data, relying on precise coordinates to complete depth compensation, strictly controlling stub value errors, and improving the yield rate of finished back-drilled products.

[0035] In some embodiments, the power supply device includes a contact device and a power source, the contact device being used to maintain electrical contact with the reference layer, and the power source being used to provide a preset voltage to the contact device to apply the preset voltage to the reference layer.

[0036] In this embodiment, the contact device is an electrical contact actuator of the power supply device, responsible for establishing a stable conductive path between the power supply and the PCB inner reference layer, and is a key intermediate component for voltage transmission. The power supply is a voltage supply component of the power supply device, used to output a constant and controllable preset voltage to provide a stable voltage reference for the second detection circuit. The preset voltage is a pre-set constant voltage value, adapted to the conduction detection requirements of the second detection circuit, ensuring accurate signal triggering and no misjudgments.

[0037] In this embodiment, the contact device employs an elastic conductive structure (such as a mushroom-shaped probe or an elastic pin), which can closely fit the lead window position of the reference layer on the PCB board edge, eliminating contact gaps and ensuring conductive reliability. The power supply is a DC regulated power supply, outputting a preset voltage adapted to the detection requirements. The voltage is continuously delivered to the inner reference layer through the contact device, keeping the reference layer energized. Combined with the spindle grounding logic, this forms a second detection circuit to be conducted. The circuit only generates a current signal when the drill bit actually contacts the reference layer. The preset voltage can be configured; for example, it can be configured to 24V.

[0038] The processing system provided in this application embodiment achieves a stable electrical connection between the power supply and the reference layer through an elastic contact device, avoiding voltage loss or signal abnormality caused by poor contact, and ensuring the continuity of inner layer detection; it adopts a regulated power supply to output a preset voltage, eliminating signal false triggering caused by voltage fluctuations, further avoiding interference caused by drill debris and drill bit side impacts, and consolidating the foundation for accurate detection of the inner reference layer.

[0039] In some embodiments, the circuit board includes at least one surface layer and at least one reference layer. A window is provided in a predetermined area on the surface layer, and an electrical contact hole is provided at a predetermined position on the circuit board. The electrical contact hole communicates with the window on the surface layer, and an electrical contact point of the reference layer is disposed on the electrical contact hole. The contact device forms an electrical connection with the reference layer through the electrical contact hole.

[0040] In this embodiment, the surface layer is the outermost conductive copper foil layer of the PCB, which is the detection object of the first detection loop, the initial contact layer for drilling, and also the outer surface protection and conductive layer of the circuit board. The reference layer is a designated conductive copper layer of the inner layer of the PCB, serving as the detection reference layer for the second detection loop. It is used to calculate the actual thickness between layers and to achieve back-drilling depth compensation, and is the core reference for inner layer positioning. The window is a copper surface opening in a preset area of ​​the PCB surface layer, used to expose the inner layer traces / contact points, break through the surface layer solder mask and copper foil obstruction, and construct an electrical contact channel. The electrical contact hole is a conductive through-hole (metallized hole) that penetrates part of the PCB board layer, connecting the surface layer window and the electrical contact point of the inner layer reference layer, realizing stable transmission of voltage signals to the inner layer. The electrical contact point is a conductive point reserved on the inner layer reference layer, set on the inner wall / bottom of the electrical contact hole, used to conduct with the electrical contact hole and receive the voltage transmitted by the contact device. Figure 2 This application provides a schematic diagram of the structure of a circuit board, as shown in the embodiment of the present application. Figure 2 As shown, the circuit board includes: a top layer 1, a reference layer 2, a target layer (not shown) and a bottom layer 3 located below the reference layer. A window 11 is provided on the top layer 1, and a window 12 is provided on the bottom layer 3. The purpose of the window 11 and the window 12 is to remove the copper layer of the top layer 1 and the bottom layer 3. An electrical contact hole 4 is provided on the circuit board, and the electrical contact hole 4 connects the window 11 and the window 12.

[0041] In this embodiment, a window can be opened in a non-functional area on the surface of the PCB to clean the solder mask and copper foil in that area, forming an exposed contact channel; an electrical contact hole is provided at the corresponding window position to ensure stable electrical contact between the conductive layer on the hole wall and the inner reference layer; a contact device (elastic probe) is inserted into the surface window and abuts against the electrical contact hole, and the preset voltage of the power supply is stably delivered to the inner reference layer through the conductive path of the electrical contact hole, thereby achieving unobstructed electrical connection between the power supply device and the reference layer.

[0042] Figure 3 This is a schematic diagram of an electrical contact point provided in an embodiment of this application, such as... Figure 3 As shown, taking two reference layers as an example, they are connected to electrical contact points via leads, and the electrical contact points are set on electrical contact holes.

[0043] Figure 4 This is a schematic diagram of the arrangement of a contact device provided in an embodiment of this application, such as... Figure 4 As shown, the contact device is connected to the reference layer 2 through an electrical contact hole.

[0044] The processing system provided in this application, through its surface window + electrical contact hole structure design, avoids interference between the PCB surface circuitry and the solder mask layer, enabling direct non-surface power transmission to the inner reference layer, ensuring stable and lossless voltage transmission. The reference layer electrical contact points are integrated on the electrical contact holes, adapting to the high-density wiring requirements of the PCB. The flexible contact device connects to the electrical contact holes through the window, making installation convenient and contact reliable, preventing contact detachment during drilling, and further eliminating detection failure caused by voltage transmission interruption, thereby ensuring the accuracy of inner layer positioning.

[0045] In some embodiments, the distance between the preset position and the edge of the circuit board is less than a preset distance.

[0046] In this embodiment, the preset position refers to the location of the electrical contact holes on the PCB, that is, the overall layout point of the surface opening and the electrical contact holes, which is the designated area where the contact device connects to the inner reference layer. The edge of the circuit board refers to the outer peripheral boundary of the PCB board, which belongs to the non-functional processing area of ​​the PCB and avoids core wiring and functional holes. The preset distance is a pre-set safety distance threshold, determined by the PCB processing technology and equipment assembly accuracy, and is used to limit the layout range of the electrical contact holes.

[0047] In this embodiment, during the PCB design phase, the placement of electrical contact holes and surface openings is defined in the area near the board edge, and the distance between this point and the PCB edge is strictly controlled to be less than the preset distance. During processing, the openings and electrical contact holes are made directly in the non-functional area of ​​the board edge, and the contact device is aligned with the contact hole in the board edge area to complete the docking, thereby realizing the electrical connection between the power supply device and the inner reference layer.

[0048] The processing system provided in this application places the electrical contact holes in the area near the board edge. This not only avoids occupying the core wiring space of the PCB and does not affect the circuit function of the circuit board, but also facilitates the quick alignment, assembly, and debugging of the machine tool contact device, adapting to automated processing flow. The layout near the board edge can shorten the length of the reference layer lead, reduce voltage signal transmission loss, and at the same time avoid the drill bit accidentally damaging the contact point during drilling, preventing damage to the contact path. The layout near the board edge can also adapt to various PCB specifications, improve the versatility of the processing system, and simplify equipment debugging and mass production operations.

[0049] In some embodiments, see continue to see Figure 1The first detection circuit includes a capacitor C and a first detection module. One end of the capacitor C is connected to the switching device, and the other end of the capacitor C is connected to the first detection module. When the drill bit contacts the surface layer of the circuit board, the capacitance value of the capacitor changes more than a change threshold. The first detection module detects a first electrical signal generated when the drill bit contacts the surface layer of the circuit board. The second detection circuit includes a current detection module, which is used to detect the current information when the drill bit contacts the reference layer. When the spindle is connected to the second detection circuit, the spindle is grounded.

[0050] In this embodiment, the capacitor is a variable capacitor connected in series with the drill bit and the copper foil on the PCB surface. It is the core sensing component of the first detection circuit. The capacitance value changes with the distance between the drill bit and the surface layer, and is crucial for triggering the surface layer positioning signal. The first detection module is a dedicated processing module adapted to the CBD capacitance detection principle. It is used to monitor capacitance value fluctuations, determine signal validity, and output accurate surface layer contact electrical signals. The change threshold is a pre-calibrated critical value for capacitance value fluctuations, used to distinguish normal interference from genuine surface layer contact signals and filter out misjudgments caused by minor fluctuations. The first electrical signal is a level transition signal sent by the first detection module to the controller after the capacitance value exceeds the limit. It is used to mark the precise Z-axis coordinate of the drill bit contacting the surface layer. The current detection module is the core processing component of the second detection circuit. It is used to monitor the current changes generated by the circuit's on / off state and identify the actual contact action between the drill bit and the inner reference layer. The current information is the current value / on / off state generated when the drill bit contacts the charged reference layer and the circuit is conducting. It is the core basis for determining the position of the inner reference layer.

[0051] In this embodiment, one end of the capacitor is connected to the conductive spindle and drill bit through a switching device, and the other end is connected to the first detection module to form a closed-loop capacitance detection path. In the initial stage of drilling, the distance between the drill bit and the surface copper foil gradually decreases during the downward movement of the drill bit, and the capacitance value continues to increase. When the change in capacitance value exceeds the preset change threshold, the first detection module determines that the drill bit is in contact with the surface, and then generates and transmits the first electrical signal to the controller.

[0052] In this embodiment, the current detection module is connected in series between the spindle grounding path and the reference layer power supply path. When the drill bit contacts the charged reference layer, the circuit is instantly turned on and a current is generated. The current detection module captures the current information and transmits the corresponding trigger signal to the controller to complete the positioning of the inner reference layer.

[0053] The processing system provided in this application improves the accuracy of surface positioning by setting a capacitance change threshold to accurately filter out drilling debris and false capacitance fluctuations caused by minor vibrations. It also employs a dedicated current detection module that responds only to the actual conduction current, completely avoiding non-contact interference signals and ensuring zero false triggering of the inner reference layer detection.

[0054] Based on the machining system provided in the foregoing embodiments, this application provides a method for determining back-drilling depth that can be applied to electronic devices. These electronic devices may include: mobile phones, tablets, wearable devices, augmented reality (AR) / virtual reality (VR) devices, laptops, ultra-mobile personal computers (UMPCs), netbooks, personal digital assistants (PDAs), etc. The electronic device can serve as the controller of the machining system. This method for determining back-drilling depth can be compiled into a computer program, which can be installed on the electronic device. The following description uses the example of an electronic device as the controller of the machining system. Figure 5 A schematic diagram illustrating the implementation process of a method for determining back-drilling depth provided for the purposes of this application is shown below. Figure 5 As shown, the methods for determining the back-drilling depth include: Step S101: Obtain the first electrical signal generated when the drill bit contacts the surface layer of the circuit board based on the first detection circuit, and determine the position of the surface layer based on the first electrical signal.

[0055] In this embodiment, the position of the surface layer refers to the Z-axis coordinate latched by the controller when the drill bit contacts the copper foil on the surface of the PCB. The position of the surface layer serves as the starting reference point for back-drilling depth measurement.

[0056] In this embodiment, in the initial state of the processing system, the switching device connects the spindle to the first detection circuit, and the spindle is not grounded. The drill bit rotates down at high speed. When it approaches the PCB surface, the variable capacitance value formed by the drill bit and the surface copper foil changes abruptly. Since the capacitance of the first detection circuit is connected in series with the capacitance formed by the drill bit and the surface copper foil, the capacitance detected by the first detection circuit will also change. The first detection module captures the capacitance change that exceeds the threshold, generates a first electrical signal, and transmits it to the controller. The controller receives the signal in real time and immediately latches the current Z-axis coordinate, which is the position of the surface.

[0057] Step S102: Control the switching device to switch so that the spindle is connected to the second detection circuit.

[0058] In this embodiment, after the controller obtains the surface position, it automatically sends a switching command to the switching device; the switching device performs a disconnection action, cuts off the electrical connection between the spindle and the first detection circuit, and then connects the spindle and the second detection circuit, while triggering the spindle to ground, thus completing the seamless switching of the dual circuits, with no signal crosstalk during the switching process.

[0059] Step S103: Obtain the second electrical signal generated when the drill bit contacts the reference layer based on the second detection circuit, and determine the position of the reference layer based on the second electrical signal, wherein the reference layer is subjected to a voltage.

[0060] In this embodiment, the position of the reference layer refers to the Z-axis coordinate latched by the controller when the drill bit contacts the inner reference layer of the PCB, which serves as the intermediate reference point for back-drilling depth measurement. The second electrical signal is a current trigger signal generated by the current detection module after the second detection circuit is turned on, used to mark the precise position of the inner reference layer.

[0061] In this embodiment, the power supply device continuously applies a stable preset voltage to the inner reference layer through a contact device and an electrical contact hole; the drill bit continues to drill downwards until the tip contacts the inner reference layer. At this time, the grounded drill bit and the charged reference layer form a closed current loop. The current detection module detects the conducting current, generates a second electrical signal, and uploads it to the controller; the controller latches the Z-axis coordinate at this time, which is the position of the reference layer.

[0062] Step S104: Determine the back-drilling depth based on the position of the surface layer and the position of the reference layer.

[0063] In this embodiment, the controller retrieves the coordinates of the surface layer position and the reference layer position, calculates the difference between the two to obtain the actual layer distance from the surface layer to the reference layer; compares the actual layer distance with the theoretical layer distance to obtain the deviation compensation value, and, combined with the target Stub value requirement, corrects the theoretical back-drilling depth to finally obtain the accurate actual back-drilling depth.

[0064] The method provided in this application relies on a dual-loop independent detection architecture to achieve precise step-by-step positioning of the surface and inner reference layers, eliminating false triggering problems caused by signal confusion and debris interference from a single loop. Automated loop switching ensures a continuous and efficient detection process, adapting to automated mass production. Depth calculation based on measured coordinates and deviation compensation completely eliminates the influence of theoretical layer spacing errors, enabling refined control of the stub value. This avoids damage to the target layer from excessively deep back drilling and excessive residue from excessively shallow drilling, significantly improving the yield rate of PCB back-drilled products and meeting the stringent process requirements of high-end, high-speed PCBs.

[0065] In some embodiments, step S104 can be implemented through the following steps: Step S1041: Determine the actual distance between the surface layer and the reference layer based on the position of the surface layer and the position of the reference layer.

[0066] In this embodiment, the actual distance is the true thickness between the PCB surface copper foil and the inner reference layer, obtained by actual measurement through a dual-loop circuit. It is obtained by directly calculating the coordinate difference by the controller and is the core parameter reflecting the actual processing error of the board.

[0067] In this embodiment, the controller retrieves the locked surface Z-axis coordinates and reference Z-axis coordinates, and directly obtains the actual distance from the surface to the inner reference layer by performing a coordinate difference operation (surface coordinates - reference layer coordinates). This value is the measured absolute value.

[0068] Step S1042: Determine the positional deviation based on the actual distance and the theoretical distance between the surface layer and the reference layer.

[0069] In this embodiment, the theoretical distance is the standard thickness from the surface layer to the reference layer preset during the PCB design stage. It is an ideal value specified in the drawings and does not take into account dimensional deviations caused by board lamination and processing. The positional deviation is the difference between the actual distance and the theoretical distance, representing the error between the actual thickness of the board and the designed thickness, and is the core basis for back-drilling depth compensation.

[0070] In this embodiment, the controller retrieves the preset theoretical distance parameter, calculates the difference between the measured actual distance and the theoretical distance (actual distance - theoretical distance), and obtains the position deviation; a positive deviation indicates that the actual plate thickness is too thick, and a negative deviation indicates that the actual plate thickness is too thin, thus accurately quantifying the plate processing error.

[0071] Step S1043: The back drill depth is obtained based on the position deviation and the theoretical depth value.

[0072] In this embodiment, the theoretical depth value is the ideal back-drilling depth calculated based on the design layer spacing and the target stub value, without considering actual board thickness error correction. The back-drilling depth is the final actual drilling depth after position deviation compensation, which is a precise processing parameter that adapts to the actual board thickness and meets stub value control.

[0073] In this embodiment, the controller adds the position deviation to the theoretical depth value, i.e., back drilling depth = theoretical depth value + position deviation, to complete the depth compensation correction; the compensated depth value matches the actual thickness of the board.

[0074] The method provided in this application, by quantifying positional deviations and dynamically correcting theoretical depths, overcomes the limitations of ideal design values, allowing the back-drilling depth to perfectly match the actual thickness of each board; it eliminates depth measurement distortion at the algorithm level, further strictly controls residual errors in stub values, avoids damage to the target retention layer due to excessive back-drilling, and prevents excessive copper wall residue due to excessively shallow back-drilling, significantly improving the consistency and finished product qualification rate of high-precision back-drilling, and meeting the stability requirements of high-end PCB mass production.

[0075] In some embodiments, while or after step S102 is being performed, the method further includes controlling the power supply device to apply a voltage to the reference layer.

[0076] In this embodiment, after the switching device completes the connection between the spindle and the second detection circuit and the spindle is grounded, the controller immediately issues a power supply command. The power supply device receives the command, starts the DC regulated power supply, and continuously delivers a preset constant voltage to the inner reference layer through the conductive path of the elastic contact device, the PCB surface window and the electrical contact hole, so that the reference layer maintains a stable charged state until the drill bit contacts the reference layer and completes the detection, at which point the power supply can be stopped as needed.

[0077] The method provided in this application explicitly defines the reference layer pressurization action as an independent step, realizing the time-sequential and standardized control of the dual-loop detection process, avoiding signal interference caused by premature voltage application or detection delay caused by delayed voltage application; it precisely controls the timing of pressurization, and in conjunction with the spindle grounding logic, quickly constructs the second detection loop to be conducted, ensuring timely inner layer detection response; through controllable pressurization, it avoids energy loss caused by prolonged reference layer charging, and at the same time prevents circuit false triggering caused by abnormal voltage application, further improving the stability and accuracy of inner layer positioning.

[0078] Based on the foregoing embodiments, this application further provides a method for determining back-drilling depth, the method comprising: Step 1: Reference layer lead wire and window design.

[0079] Design leads on the reference layer inside the PCB, converge them to a certain position on the edge of the board, and make a copper window on the surface layer at that position.

[0080] Step 2: Setting up the contact device.

[0081] A device with elastic contact (such as a mushroom-shaped probe) is installed on the machine base to maintain reliable electrical contact with the opening at the edge of the board and to apply a stable voltage signal.

[0082] Step 3: Construction of the dual-loop detection system.

[0083] Includes two independent detection loops: First detection circuit (capacitance detection circuit): Based on the existing CBD principle, the first electrical signal is triggered by the capacitance change formed by the contact between the drill bit and the surface copper to determine the Z position of the surface. The second detection circuit (contact-type electrical detection circuit): the drill bit is grounded, and a preset voltage (such as 24V) is applied to the inner reference layer through the board edge contact device. When the drill bit processes to this layer, a current loop is formed, and the Z position of the reference layer is determined by current detection.

[0084] Step 4: Based on the difference between the theoretical interlayer distance and the measured distance, perform hole-to-hole compensation for the subsequent depth control drilling.

[0085] In this embodiment, after switching the second detection circuit at trigger copper acquisition position 1 via the first detection circuit, reference layer acquisition position 2 is triggered. The actual distance H1 from the copper surface to the reference layer is obtained via (position 1 - position 2). H1 - H (theoretical distance) is the compensation value that needs to be added during subsequent depth control. For example, if the theoretical distance H is 2mm and the theoretical distance H2 is 1mm, then the theoretical distance from the copper surface to the target layer is 3mm. The subsequent depth control requires a residual STUB value of 0-0.025mm on the target layer; therefore, the set theoretical depth control value K = 2.975. If the actual distance H1 is 2.2mm, then the actual distance from the copper surface to the target layer is at least 3.2mm. In this case, the software compensates for the theoretical depth control value, resulting in a back-drilling depth of K + H1 - H = 2.975 + 2.2 - 2.0 = 3.175mm.

[0086] Figure 6 This is a flowchart illustrating a detection loop triggering timing provided in an embodiment of this application, as shown below. Figure 6 As shown, it includes: Step S601: The switching device is connected to the first detection circuit.

[0087] Step S602: Contact the surface layer to acquire the signal and record position 1.

[0088] Step S603: The switching device switches the connection to the second detection circuit.

[0089] In this embodiment, the power supply device supplies power to the reference layer.

[0090] Step S604: The second detection loop contacts the reference layer to acquire a signal and records position 2.

[0091] Step S605: After processing is completed, the switching device switches the connection to the first detection circuit.

[0092] Step S606: Continue with inspection / processing completed.

[0093] Figure 7 This is a schematic diagram of a signal switching process provided in an embodiment of this application, such as... Figure 7 As shown, it includes: In step S701, the first detection module of the first detection circuit detects a high level.

[0094] In step S702, the first detection circuit comes into contact with the surface layer, forming a capacitor circuit. The surface layer voltage increases, and the detection voltage of the first detection module decreases.

[0095] In step S703, the controller detects a voltage drop in the first detection module and records position 1.

[0096] In step S704, the controller provides a switching signal to the switching device to switch to the second detection loop.

[0097] In step S705, the current detection module detects no current.

[0098] Step S706: The conductive device supplies power to the reference layer.

[0099] In step S707, the second detection circuit contacts the reference layer through the drill bit, the circuit is closed, and the current detection module detects the current.

[0100] Step S708: The controller detects an increase in the current value of the current detection module and records it at position 2.

[0101] In step S709, the controller provides a switching signal to the switching device to switch to the first detection loop.

[0102] The method provided in this application embodiment achieves electrical isolation detection between the surface layer and the inner layer, significantly reducing false alarms of the inner layer caused by factors such as lint and side impacts; the dual-circuit signal triggering mechanism is different, improving detection stability and repeatability accuracy; detection and compensation can be automatically completed during processing without manual intervention, adapting to high-mix lines and multi-variety production environments.

[0103] Based on the foregoing embodiments, this application provides a back-drilling method. Figure 8 This is a schematic diagram illustrating the implementation process of a back-drilling method provided in an embodiment of this application, as shown below. Figure 8 As shown, it includes: Step S801: Obtain the back drill depth obtained by any of the methods for determining back drill depths.

[0104] In this embodiment, the controller can call the dual-loop detection and depth compensation calculation results mentioned above, read the final back-drilling depth value after actual layer spacing deviation correction, and synchronously transmit the value to the equipment drive module to lock the depth benchmark of this drilling.

[0105] Step S802: Perform back drilling on the circuit board based on the back drilling depth.

[0106] In this embodiment, the device drive module receives a precise back-drilling depth command and controls the spindle to drive the drill bit to rotate at high speed, aligning it with the hole to be processed on the PCB and drilling downwards; the spindle has a built-in displacement sensor to monitor the downward distance in real time, and when the drilling depth reaches the preset compensated depth, the controller immediately issues a stop and tool lifting command to stop the drilling action and complete a single back-drilling operation.

[0107] The method provided in this application embodiment connects depth measurement with actual processing in a closed loop, directly implementing the accurate depth results of dual-loop detection, and realizing integrated control of detection-compensation-processing; relying on the measured and compensated depth drilling, it completely avoids processing deviations caused by plate errors and interference signals.

[0108] Based on the foregoing embodiments, this application provides another circuit board, which is manufactured using the back-drilling method provided in the above embodiments. The circuit board includes at least one surface layer and at least one reference layer. A window is provided in a predetermined area on the surface layer, and an electrical contact hole is provided at a predetermined position on the circuit board. The electrical contact hole communicates with the window on the surface layer, and the electrical contact point of the reference layer is disposed on the electrical contact hole.

[0109] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0110] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A processing system, characterized in that, include: spindle; A switching device, one end of which is electrically connected to the main spindle; The first detection circuit and the second detection circuit, the other end of the switching device are respectively connected to the first detection circuit and the second detection circuit, the switching device is used to electrically connect the spindle to the first detection circuit or the second detection circuit, during the process of the spindle driving the drill bit to drill a hole in the circuit board, the first detection circuit is used to detect the first electrical signal generated when the drill bit contacts the surface layer of the circuit board, and the second detection circuit is used to detect the second electrical signal generated when the drill bit contacts the reference layer of the circuit board. The machining system can be used to determine the back-drilling depth based on the first electrical signal and the second electrical signal.

2. The processing system according to claim 1, characterized in that, The processing system also includes: A power supply device for applying voltage to the reference layer; A controller, connected to the first detection circuit and the second detection circuit, is used to determine the back-drilling depth based on the first electrical signal and the second electrical signal.

3. The processing system according to claim 2, characterized in that, The power supply device includes a contact device and a power source. The contact device is used to maintain electrical contact with the reference layer, and the power source is used to provide a preset voltage to the contact device to apply the preset voltage to the reference layer.

4. The processing system according to claim 3, characterized in that, The contact device includes an elastic contact device.

5. The processing system according to claim 3, characterized in that, The circuit board includes at least one surface layer and at least one reference layer. A window is provided in a predetermined area on the surface layer. An electrical contact hole is provided at a predetermined position on the circuit board. The electrical contact hole communicates with the window on the surface layer. An electrical contact point of the reference layer is disposed on the electrical contact hole. The contact device forms an electrical connection with the reference layer through the electrical contact hole.

6. The processing system according to claim 5, characterized in that, The distance between the preset position and the edge of the circuit board is less than a preset distance.

7. The processing system according to claim 1, characterized in that, The first detection circuit includes a capacitor and a first detection module. One end of the capacitor is connected to the switching device, and the other end of the capacitor is connected to the first detection module. When the drill bit contacts the surface layer of the circuit board, the capacitance value of the capacitor changes more than a change threshold. The first detection module detects a first electrical signal generated when the drill bit contacts the surface layer of the circuit board. The second detection circuit includes a current detection module, which is used to detect the current information when the drill bit contacts the reference layer. When the spindle is connected to the second detection circuit, the spindle is grounded.

8. A method for determining back-drilling depth, characterized in that, Applied to the processing system according to any one of claims 1 to 7, comprising: The first electrical signal generated when the drill bit contacts the surface layer of the circuit board is obtained based on the first detection circuit, and the position of the surface layer is determined based on the first electrical signal. The switching device is controlled to switch so that the main shaft is connected to the second detection circuit; The second electrical signal generated when the drill bit contacts the reference layer is obtained based on the second detection circuit, and the position of the reference layer is determined based on the second electrical signal, wherein a voltage is applied to the reference layer; The back-drilling depth is determined based on the position of the surface layer and the position of the reference layer.

9. The method according to claim 8, characterized in that, Determining the back-drilling depth based on the position of the surface layer and the position of the reference layer includes: Based on the position of the surface layer and the position of the reference layer, determine the actual distance between the surface layer and the reference layer; The positional deviation is determined based on the actual distance and the theoretical distance between the surface layer and the reference layer; The back-drilling depth is obtained based on the positional deviation and the theoretical depth value.

10. The method according to claim 8, characterized in that, The method further includes: The control power supply device applies voltage to the reference layer.

11. A back-drilling method, characterized in that, include: Obtain the back-drilling depth obtained by the method for determining back-drilling depth according to any one of claims 8 to 10; The circuit board is back-drilled based on the stated back-drilling depth.

12. A circuit board, characterized in that, The circuit board is manufactured using the back-drilling method of claim 11. The circuit board includes at least one surface layer and at least one reference layer. A window is provided in a predetermined area on the surface layer. An electrical contact hole is provided at a predetermined position on the circuit board. The electrical contact hole communicates with the window on the surface layer. The electrical contact point of the reference layer is disposed on the electrical contact hole.

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