Multilayer circuit board and back drilling hole processing method and back drilling hole drilling equipment thereof

Abstract

The invention discloses a multi-layer circuit board and a back drilling processing method and back drilling equipment thereof. The processing method comprises the following steps: providing a multi-layer substrate, forming a through hole in the multi-layer substrate, and electroplating the through hole to obtain a metal through hole; performing graphic processing on the surface of a top substrate on the multilayer substrate with the metal through holes to obtain a multilayer substrate with a surface circuit layer; and performing CT scanning on the multi-layer substrate to determine the back drilling depth of the metal through holes, and performing drilling treatment along the depth direction from the metal through holes in the top-layer substrate according to the back drilling depth to obtain the multi-layer circuit board. Therefore, the length of the processed stub meets the requirement and is not too large or too small, and the purposes of ensuring that the multi-layer circuit board achieves relatively high signal integrity, improving the processing quality and reducing the rejection rate are achieved.

Description

Technical Field

[0001] This invention relates to the field of circuit board processing, and more particularly to a multilayer circuit board and a back-drilling method and equipment for back-drilling holes therein. Background Technology

[0002] With the application and rapid development of electronic products, high-frequency and high-speed PCBs (printed circuit boards) are gradually evolving towards higher layering, higher density, and higher signal integrity requirements. The complexity of PCB circuitry has increased significantly, making wiring more difficult, and electromagnetic interference exists between circuits. Single-sided or double-sided boards can no longer meet production demands; therefore, high-frequency and high-speed PCBs are generally multi-layered circuit boards. To achieve high signal integrity in high-frequency and high-speed PCBs, it is essential to minimize sources of interference signals.

[0003] In the PCB industry, back-drilling is a common process. This involves using a mechanical drilling machine with controlled depth drilling to remove chemical copper from layers that don't require interconnection, ensuring signal transmission integrity. However, due to the taper of the drill bit and the inability of the equipment to precisely control the depth, unusable metal sections inevitably remain, known as studs. The longer the stud, the greater the impedance of the signal hole, and the greater the impact on signal transmission integrity. If the stud is too short or even drills through the target layer, the back-drilled hole will pass through a section of usable metal, causing the circuit board to malfunction and become unusable. Furthermore, current back-drilling inspection methods cannot guarantee the detection of this defect, resulting in stud lengths that are too large or too small, affecting the performance of the final product and causing significant losses. Therefore, controlling stud length is crucial in PCB manufacturing. Summary of the Invention

[0004] This invention provides a multilayer circuit board and a back-drilling method and equipment for back-drilling, in order to solve the problem in the prior art where the length of the residual pile in the back-drilling process is too large or too small, or even drills through the target layer, due to changes in board thickness.

[0005] To achieve the above objectives, in one embodiment, a method for back-drilling holes in a multilayer circuit board is provided, the method comprising the following steps: A multilayer substrate is provided, through holes are formed on the multilayer substrate, and the through holes are electroplated to obtain a multilayer substrate with metal through holes. The multilayer substrate is subjected to CT scanning to determine the back-drilling depth of the metal through-holes. The metal through-holes are then back-drilled to a preset depth according to the back-drilling depth to obtain a multilayer circuit board.

[0006] In one embodiment, performing a CT scan on the multilayer substrate includes: The area to be back-drilled on the multilayer substrate is determined, and a CT scan is performed on the multilayer substrate at the corresponding position according to the area to be back-drilled.

[0007] In one embodiment, performing a CT scan on the multilayer substrate to determine the back-drilling depth of the metal via, and then back-drilling the metal via to a preset depth according to the back-drilling depth, includes: Patterning is performed on the surface of the top substrate of the multilayer substrate with the metal through-hole to obtain a multilayer substrate with a surface circuit layer. A CT scan is performed on the multilayer substrate to determine the back-drilling depth at which the metal vias are to be back-drilled. Based on the back-drilling depth, back-drilling is performed at a preset depth from the corresponding metal via on the top substrate along the depth direction.

[0008] In one embodiment, performing a CT scan on the multilayer substrate to determine the back-drilling depth of the metal via includes: The multilayer substrate is subjected to CT scanning to determine the reference layer position and target layer position of the multilayer substrate. The reference layer position is the depth information of the top substrate, and the target layer position is the depth information of the target layer substrate in the multilayer substrate that does not require circuit connection. Calculate the vertical distance between the reference layer position and the target layer position to obtain the back-drilling depth in the metal via from the top substrate to the target substrate.

[0009] In one embodiment, performing a CT scan on the multilayer substrate to determine the location of the reference layer and the target layer of the multilayer substrate specifically includes: At least three reference points are taken on the upper surface of the top substrate of the multilayer substrate, a reference surface is determined based on the reference points, the depth of the reference surface is calculated, and the position of the reference layer is obtained. The multilayer substrate is subjected to CT scanning to generate three-dimensional position information of the target layer substrate of the multilayer substrate. The depth information of N metal holes on the target layer substrate is extracted from the three-dimensional position information and used as N target layer positions, where N≥1. Calculate the vertical distance between the reference layer position and the target layer position to obtain the back-drilling depth of the metal via from the top substrate to the target substrate, specifically including: Calculate the vertical distance between the reference layer position and each of the target layer positions, and the N back-drilling depths from the top substrate to the target layer substrate in the metal via.

[0010] In one embodiment, after performing a CT scan on the multilayer substrate to determine the back-drilling depth of the metal via, the back-drilling method further includes: The QR code containing the back-drilling depth is marked at the corner of the multilayer substrate. The drilling machine scans a QR code located at the corner of the multilayer substrate to obtain the back drilling depth, so that the drilling machine can perform the drilling process according to the back drilling depth.

[0011] In one embodiment, marking a QR code containing the back-drilling depth at a corner position of the multilayer substrate includes: The QR code is formed by marking the corner of the multilayer substrate using a laser marking device; or by performing graphic exposure processing on the corner of the multilayer substrate; or by spraying the QR code on the corner of the multilayer substrate using a CT scanner.

[0012] In one embodiment, after drilling from the metal via on the top substrate along the depth direction according to the back-drilling depth to obtain a multilayer circuit board, the method further includes: Obtain reference drilling data for the drilling process, compare the reference drilling data with the detected actual drilling data, obtain the deviation value between the reference drilling data and the actual drilling data, and use a drilling machine to perform drilling compensation processing on the metal through hole that generates the deviation value based on the deviation value. Alternatively, obtain reference drilling data for the drilling process of N multilayer substrates in the current batch, where N≥1, compare the N sets of reference drilling data with the detected actual drilling data, obtain the deviation values ​​between the N sets of reference drilling data and the detected actual drilling data, determine the comprehensive deviation value based on the N deviation values, and perform drilling compensation processing using the metal through-holes of the multilayer substrates in the current batch of the drilling machine based on the comprehensive deviation value.

[0013] In one embodiment, the back-drilling depth is obtained using a network communication method with a drilling rig, and drilling is performed along the depth direction from the metal through-hole on the top substrate according to the back-drilling depth.

[0014] In one embodiment, the step of patterning the surface of the top substrate on a multilayer substrate having the metal vias to obtain a multilayer substrate with a surface circuit layer includes: Clean the surface of the top substrate on the multilayer substrate, attach a dry film to the surface of the top substrate, and expose the top substrate with ultraviolet light using an exposure device; then develop the top substrate to obtain a patterned top substrate. The top substrate is subjected to pattern electroplating to remove the dry film, resulting in a multilayer substrate with a surface circuit layer.

[0015] In one embodiment, a multilayer circuit board is provided, which is prepared by the back-drilling process described in any of the preceding embodiments.

[0016] In one embodiment, a back-drilling device is provided, which integrates an X-ray inspection device. The back-drilling device is used to drill holes in a multilayer circuit board according to the back-drilling processing method described in any of the preceding embodiments.

[0017] In one embodiment, the back drilling equipment further includes a controller, the data input terminal of which is connected to the data output terminal of the X-ray inspection device for acquiring CT scan data; the data output terminal of the controller is connected to the data input terminal of the drilling rig for outputting the back drilling depth.

[0018] The aforementioned multilayer circuit board and its back-drilling processing method and equipment incorporate a CT scanning step of the multilayer substrate into the original back-drilling processing technology. This allows the back-drilling depth of the metal through-hole to be determined based on the CT scan results. Based on the back-drilling depth, a secondary drilling process is performed from the metal through-hole on the top substrate along the depth direction. This ensures that the length of the residual stake after the secondary drilling process according to the back-drilling depth meets the requirements and is neither too large nor too small. This guarantees that the multilayer circuit board achieves high signal integrity, improves processing quality, and reduces the scrap rate. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the 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.

[0020] Figure 1 This is a flowchart of a back-drilling method for a multilayer circuit board according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a multilayer substrate formed by lamination in one embodiment of the present invention; Figure 3 This is a schematic diagram of a multilayer substrate with through holes in one embodiment of the present invention; Figure 4 This is a schematic diagram of a multilayer substrate with metal through holes obtained by electroplating in one embodiment of the present invention; Figure 5 This is a schematic diagram of locating the scan pattern of a multilayer substrate to the target layer of a secondary drilling in one embodiment of the present invention; Figure 6 This is a schematic diagram of the vertical distance between the reference layer position and the target layer position of a multilayer substrate in one embodiment of the present invention; Figure 7 This is a schematic diagram of a multilayer substrate in which the thickness of each substrate layer is deformed in one embodiment of the present invention. Figure 8 This is a schematic diagram of a back drilling device according to an embodiment of the present invention; Figure 9 This is a schematic diagram of another back-drilling device according to one embodiment of the present invention; The labeling is explained as follows: 1. Copper foil; 2. Resin fiberglass; 3. Through hole; 4. Metal through hole; 5. Base layer; 6. Target layer; 7. Residual pile. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals denote the same elements throughout.

[0023] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this invention, the first element, component, area, layer, or portion discussed below may be referred to as the second element, component, area, layer, or portion.

[0024] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein for convenience of description to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, then the element or feature described as “below,” “under,” or “below” other elements or features will be oriented “above” other elements or features. Therefore, the exemplary terms “below” and “under” can include both above and below orientations. The device may be otherwise oriented (rotated 90 degrees or otherwise) and the spatial descriptive terms used herein will be interpreted accordingly.

[0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising” and / or “including,” when used in this specification, identify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0026] To fully understand this invention, detailed structures and steps will be presented in the following description to illustrate the technical solution proposed by this invention. Preferred embodiments of the invention are described in detail below; however, in addition to these detailed descriptions, the invention may have other embodiments.

[0027] In one embodiment, a method for back-drilling holes in a multilayer circuit board is provided, the process of which is as follows: Figure 1 As shown, the back drilling method includes the following steps: S101, a multilayer substrate is provided, through holes are formed on the multilayer substrate, and the through holes are electroplated to obtain metal through holes; Among them, the provided multilayer substrates are such as Figure 2 As shown, the multilayer substrate is formed by lamination, and each substrate layer consists of copper foil 1 and resin glass fiber 2. Furthermore, before laminating multiple substrates, the circuit patterns of all substrates except the top substrate have already been prepared.

[0028] After lamination to form a multilayer substrate, a PCB drilling machine is used... Figure 2 Machining is performed on the sheet metal, and through holes 3 are drilled to obtain the following result: Figure 3 The plate shown is electroplated with chemical copper in through hole 3 to obtain metal through hole 4, as shown. Figure 4 As shown.

[0029] S102, perform CT scanning on the multilayer substrate to determine the back-drilling depth of the metal through-hole to be back-drilled, and back-drill the metal through-hole to a preset depth according to the back-drilling depth to obtain the multilayer circuit board.

[0030] Among these methods, CT scanning can detect the various metal layers of a multilayer substrate, thereby enabling the location of the target layer 6 for secondary drilling based on the scan pattern. Figure 5 As shown, a secondary drilling process is performed from the metal via on the top substrate downwards according to the back-drilling depth H of the target layer 6. In this step, to ensure the integrity of signal transmission, chemical copper between layers that do not require circuit connection is removed by controlled-depth drilling based on the first through-hole drilling.

[0031] The back-drilling method in this embodiment adds a CT scanning step to the original back-drilling process for multilayer substrates. This allows the back-drilling depth of the metal vias to be determined based on the CT scan results. Based on the back-drilling depth, a secondary drilling process is performed from the metal vias on the top substrate along the depth direction. This ensures that the length of the residual pile after the secondary drilling process according to the back-drilling depth meets the requirements and is neither too large nor too small. This guarantees that the multilayer circuit board achieves high signal integrity, improves processing quality, and reduces the scrap rate.

[0032] In one embodiment, step S102 above, performing a CT scan on the multilayer substrate, includes: The area to be back-drilled on the multilayer substrate is determined, and a CT scan is performed on the multilayer substrate at the corresponding position according to the area to be back-drilled.

[0033] In this embodiment, CT scanning is performed on a specific area of ​​the multilayer substrate to be back-drilled, rather than a global scan. A rapid scan is performed on the area to be processed, which improves scanning efficiency and thus improves the overall back-drilling processing efficiency.

[0034] In one embodiment, step S102 above, which involves performing a CT scan on the multilayer substrate to determine the back-drilling depth of the metal via, and then back-drilling the metal via to a preset depth according to the back-drilling depth, includes: S11, pattern processing is performed on the surface of the top substrate on the multilayer substrate having the metal through-hole to obtain a multilayer substrate with a surface circuit layer. Among them, in obtaining Figure 4 After multiple metal vias 4 are formed, a circuit pattern is fabricated on the top substrate of the multilayer substrate to obtain the surface circuit layer.

[0035] S12, perform CT scanning on the multilayer substrate to determine the back-drilling depth of the metal through-hole to be back-drilled at the corresponding position, and perform back-drilling processing at a preset depth from the corresponding metal through-hole on the top substrate along the depth direction according to the back-drilling depth.

[0036] Since multiple metal vias are provided at different locations on the multilayer substrate, each metal via can be back-drilled according to the calculated back-drilling depth.

[0037] In this embodiment, CT scanning is performed on the entire area of ​​the multilayer substrate to be back-drilled, which enables back-drilling of multiple metal vias on the top substrate, thus ensuring higher signal integrity, improving processing quality, and reducing scrap rate of the multilayer circuit board.

[0038] In one embodiment, step S102 above, namely performing a CT scan on the multilayer substrate to determine the back-drilling depth of the metal via, includes: S201, Perform a CT scan on the multilayer substrate to determine the reference layer position and target layer position of the multilayer substrate. The reference layer position is the depth information of the top substrate, and the target layer position is the depth information of the target layer substrate in the multilayer substrate that does not require circuit connection. S202, calculate the vertical distance between the reference layer position and the target layer position to obtain the back-drilling depth in the metal through hole from the top substrate to the target substrate.

[0039] This can be achieved using a PCB-specific CT scanning device. The copper foil of the topmost substrate is used as the reference layer 5. Before back-drilling, the board is CT-scanned to obtain the actual depth H (back-drilling depth) of the target layer at the location requiring back-drilling, which is the vertical distance between the target layer 6 and the reference layer 5. Figure 6 As shown.

[0040] The back-drilling method in this embodiment accurately locates the back-drilling depth between the reference layer and the target layer of the multilayer substrate using CT scanning. The back-drilling depth can be used for back-drilling, which can not only meet the processing requirements and ensure that the length of the residual pile 7 meets the requirements, but also improve the processing quality and reduce the scrap rate of the board.

[0041] In one embodiment, considering that during the back-drilling process, in addition to the equipment accuracy causing the residual pile length to be too large or too small, the thickness variation of the processed board itself also plays a crucial role. Because the resin of the substrate has fluidity, as the number of laminated layers of the multilayer substrate increases, the thickness of the board at different locations within the same board changes. If the same back-drilling depth is used for controlled back-drilling, it is relatively easy to result in a residual pile length that is too large or too small, or even drill through the entire board.

[0042] Therefore, step S201 above, which involves performing a CT scan on the multilayer substrate to determine the location of the reference layer and the target layer of the multilayer substrate, specifically includes: S301, at least three reference points are taken on the upper surface of the top substrate of the multilayer substrate, a reference surface is determined based on the reference points, the depth of the reference surface is calculated, and the position of the reference layer is obtained. Among them, such as Figure 7 For the multilayer substrates with varying thicknesses shown, three highest points on the surface copper foil of the top substrate can be taken as reference points. Then, a reference surface can be calculated based on the coordinates of the three reference points, and the depth of the reference surface can be used as the position of the reference layer.

[0043] In this step, the reference surface is determined by selecting the three highest points as reference points. This is because in the actual processing of multilayer circuit boards, a metal aluminum sheet with high flatness will be added to the surface of the top substrate. The reference surface is used to simulate the plane where the metal aluminum sheet is located, and serves as the reference surface for secondary drilling.

[0044] S302, Perform CT scanning on the multilayer substrate to generate three-dimensional position information of the target layer substrate of the multilayer substrate, and extract the depth information of N metal holes on the target layer substrate from the three-dimensional position information as N target layer positions, where N≥1; Among them, after performing CT scanning on a multilayer substrate, three-dimensional position information of each layer of the substrate can be generated. The three-dimensional position information of each point on the surface of each layer includes horizontal, vertical, and triangular coordinates. The vertical coordinates of N metal holes on the surface of the target layer substrate can be extracted to obtain the depth information of the metal holes, i.e., the positions of the N target layers. That is, as shown... Figure 7 As shown, since the thickness of the target layer substrate also changes, the depth information at the N metal holes obtained is different, that is, different target layer positions.

[0045] In step S202 above, that is, calculating the vertical distance between the reference layer position and the target layer position to obtain the back-drilling depth of the metal via from the top substrate to the target substrate, specifically includes: S303, calculate the vertical distance between the reference layer position and each of the target layer positions, and the N back-drilling depths from the top substrate to the target layer substrate in the metal via.

[0046] For example, such as Figure 7As shown, the depth information at the two metal holes is determined, namely the first target layer position OP1 and the second target layer position OP2. The difference between the first target layer position OP1 and the reference layer position is used to obtain the first back-drilling depth H1 in the first metal via from the top substrate to the target layer substrate; the difference between the second target layer position OP2 and the reference layer position is used to obtain the second back-drilling depth H2 in the second metal via from the top substrate to the target layer substrate. According to Figure 7 As shown, the first back-drilling depth H1 is greater than the second back-drilling depth H2. Then, drilling is performed in the first metal through hole according to the first back-drilling depth H1, and drilling is performed in the second metal through hole according to the second back-drilling depth H2.

[0047] The back-drilling method in this embodiment uses a CT scanning device to scan the board (i.e., multilayer substrate) before back-drilling to obtain the actual depth of the target layer from the reference layer (i.e., back-drilling depth). Then, a mechanical drilling machine is used to compensate for the back-drilling. This method solves the problem that the residual length of the back-drilled hole is too long, too short, or even drilled through due to the influence of changes in the thickness of the board. It achieves precise processing of the back-drilled hole, thereby reducing the probability of scrap due to defective back-drilled holes and ensuring the quality of the product.

[0048] In one embodiment, after performing a CT scan on the multilayer substrate to determine the back-drilling depth of the metal via, the back-drilling method further includes: S401, mark the QR code containing the back drilling depth at the corner of the multilayer substrate; S402, the drilling machine scans the QR code located at the corner of the multilayer substrate to obtain the back drilling depth, so that the drilling machine performs the drilling process according to the back drilling depth.

[0049] The obtained back-drilling depth information can be transmitted to the drilling machine in a certain way, such as by setting a QR code containing the back-drilling depth and placing the QR code at the corner of the multilayer substrate in a position that is easy for the drilling machine to scan.

[0050] In this embodiment, the back-drilling method uses CT scanning technology to detect the multilayer substrate before back-drilling to generate back-drilling depth data containing metal through holes. Then, a mechanical drill reads the back-drilling depth data in the QR code by scanning and performs back-drilling according to the back-drilling depth to obtain high-quality back-drilled holes.

[0051] In one embodiment, step S401 above, which involves marking the QR code containing the back-drilling depth at the corner of the multilayer substrate, includes: A pattern exposure process is performed at the corner of the multilayer substrate to form a QR code at the corner of the multilayer substrate.

[0052] Among them, a QR code pattern can be generated at the corner of a multilayer substrate through exposure and development processes, which makes it convenient for drilling rigs to scan the QR code to obtain depth information.

[0053] In one embodiment, step S401 above, which involves marking the QR code containing the back-drilling depth at the corner of the multilayer substrate, includes: A CT scanner is used to spray a coating onto the corners of the multilayer substrate to form QR codes at the corners of the multilayer substrate.

[0054] Among them, the QR code spraying function built into the CT scanner can be used to process the corner positions of the multilayer substrate and generate QR code pattern markings on the corner positions, so that the drilling rig can scan the QR code to obtain depth information.

[0055] In one embodiment, step S401 above, which involves marking the QR code containing the back-drilling depth at the corner of the multilayer substrate, includes: The multilayer substrate is marked with a laser marking device to form a QR code at the corner of the multilayer substrate.

[0056] In this process, a multilayer substrate can be placed on the operating table of a laser marking machine and fixed, and then the laser marking machine can be operated to mark the corners of the multilayer substrate to form a QR code.

[0057] In one embodiment, after drilling from the metal via on the top substrate along the depth direction according to the back-drilling depth to obtain a multilayer circuit board, the method further includes: Obtain reference drilling data for the drilling process, compare the reference drilling data with the actual drilling data obtained by detection, obtain the deviation value between the reference drilling data and the actual drilling data, and use a drilling machine to perform drilling compensation processing on the metal through hole that generates the deviation value based on the deviation value.

[0058] In this embodiment, the secondary drilling is based on the accurately detected back depth. However, accurate detection does not necessarily mean accurate processing. To ensure accurate processing, after the secondary drilling is completed, the data of the processed back drilling is further compared with the data of the actual drilling control. If there is a deviation in the comparison result, the deviation value is compensated to the drilling machine to achieve continuous feedback and improvement of drilling measurement, thereby improving the processing accuracy.

[0059] In one embodiment, after drilling from the metal via on the top substrate along the depth direction according to the back-drilling depth to obtain a multilayer circuit board, the method further includes: Obtain reference drilling data for the drilling process of N multilayer substrates in the current batch, where N≥1. Compare the N sets of reference drilling data with the actual drilling data obtained by detection to obtain the deviation values ​​between the N sets of reference drilling data and the actual drilling data obtained by detection. Determine the comprehensive deviation value based on the N deviation values. Based on the comprehensive deviation value, perform drilling compensation processing using the metal through-holes of the multilayer substrates in the current batch of drilling machines.

[0060] For the back drilling process of each batch of circuit boards, reference drilling data can be used for drilling on one multilayer substrate or multiple multilayer substrates. When multiple reference drilling data are obtained, multiple actual drilling data can be detected. The deviation between the reference drilling data and the actual drilling data can be obtained by calculating the difference. The average of the multiple deviation values ​​can be used to obtain the comprehensive deviation value. According to the comprehensive deviation value, drilling compensation processing is performed on the metal through holes of each circuit board in the current batch. This can improve the processing accuracy while taking into account the drilling efficiency.

[0061] In practical applications, due to certain uncontrollable factors in the lamination and other processes of multilayer circuit boards from different production batches or with different specifications, the internal layer conditions of multilayer circuit boards vary from batch to batch. To further improve the back-drilling accuracy of multilayer circuit boards in each batch, it is possible to obtain initial processing data for multiple quantities of multilayer circuit boards in each batch in advance. By pre-drilling back holes and CT scanning the back-drilling quality, data on the corresponding circuit boards and processing quality can be obtained in advance. When processing different batches of circuit boards, the corresponding batch of circuit boards can be compensated for, and the drilling machine can be compensated accordingly. This improves the flexibility and applicability of actual processing scenarios by supplementing the data for different circuit boards.

[0062] In one embodiment, in step S103 above, the back drilling depth can also be obtained by using a drilling rig to conduct network communication, and drilling can be performed along the depth direction from the metal through hole on the top substrate according to the back drilling depth.

[0063] Among them, the drilling rig can obtain depth information through wireless or wired network communication, without the need to set QR codes at the corners of the multilayer substrate, which can quickly obtain depth information and speed up the drilling process of the circuit board.

[0064] In one embodiment, the step of patterning the surface of the top substrate on a multilayer substrate having the metal vias to obtain a multilayer substrate with a surface circuit layer includes: Clean the surface of the top substrate on the multilayer substrate, attach a dry film to the surface of the top substrate, and expose the top substrate with ultraviolet light using an exposure device; then develop the top substrate to obtain a patterned top substrate. The top substrate is subjected to pattern electroplating to remove the dry film, resulting in a multilayer substrate with a surface circuit layer.

[0065] The pattern electroplating process involves electroplating a copper layer of the required thickness and a gold-nickel or tin layer of the required thickness onto the exposed copper foil or hole walls of the circuit pattern. After the process, the dry film is removed using a NaOH solution to expose the non-circuit copper layer, thereby obtaining a multilayer substrate with a surface circuit layer.

[0066] In one embodiment, a multilayer circuit board is provided, which is prepared by the back-drilling process described in any of the preceding embodiments.

[0067] The multilayer circuit board in this embodiment, after being processed by a special back-drilling method, ensures that the length of the residual posts on the circuit board meets the requirements, thereby improving the product yield and resulting in higher product quality.

[0068] In one embodiment, a back-drilling device is provided, such as... Figure 8 As shown, the back drilling equipment is equipped with an X-ray inspection device. The back drilling equipment is used to drill holes in multilayer circuit boards according to the back drilling processing method described in any of the preceding embodiments.

[0069] The process involves using X-ray inspection equipment to perform CT scanning on the multilayer substrate to determine the back-drilling depth of the metal vias, and then using a drilling machine to perform primary and secondary drilling on the multilayer substrate. Primary drilling refers to creating multiple metal vias on the multilayer substrate, while secondary drilling refers to drilling along the depth direction at some of the metal vias on the top layer substrate according to the obtained back-drilling depth.

[0070] In one embodiment, such as Figure 9 As shown, the back drilling equipment also includes a controller. The data input terminal of the controller is connected to the data output terminal of the X-RAY inspection device to acquire CT scan data. The data output terminal of the controller is connected to the data input terminal of the drilling rig to output the back drilling depth.

[0071] The controller is used to acquire CT scan data transmitted by the X-RAY inspection device and execute the processes in steps S201 to S202 or steps S301 to S303 above. It calculates N back-drilling depths from the top substrate to the target substrate in some metal through holes and sends the back-drilling depth data to the drilling machine so that the drilling machine can perform secondary drilling on each metal through hole according to the N back-drilling depths.

[0072] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention 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 the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for back-drilling holes in a multilayer circuit board, characterized in that, The back drilling method includes the following steps: A multilayer substrate is provided, through holes are formed on the multilayer substrate, and the through holes are electroplated to obtain a multilayer substrate with metal through holes. The multilayer substrate is subjected to CT scanning to determine the back-drilling depth of the metal through-holes. The metal through-holes are then back-drilled to a preset depth according to the back-drilling depth to obtain a multilayer circuit board.

2. The back-drilling method according to claim 1, characterized in that, The CT scan of the multilayer substrate includes: The area to be back-drilled on the multilayer substrate is determined, and a CT scan is performed on the multilayer substrate at the corresponding position according to the area to be back-drilled.

3. The back-drilling method according to claim 1, characterized in that, The step of performing a CT scan on the multilayer substrate to determine the back-drilling depth of the metal via, and then performing back-drilling on the metal via to a preset depth according to the back-drilling depth, includes: Patterning is performed on the surface of the top substrate of the multilayer substrate with the metal through-hole to obtain a multilayer substrate with a surface circuit layer. A CT scan is performed on the multilayer substrate to determine the back-drilling depth at which the metal vias are to be back-drilled. Based on the back-drilling depth, back-drilling is performed at a preset depth from the corresponding metal via on the top substrate along the depth direction.

4. The back-drilling method according to any one of claims 1 to 3, characterized in that, The step of performing a CT scan on the multilayer substrate to determine the back-drilling depth of the metal via includes: The multilayer substrate is subjected to CT scanning to determine the reference layer position and target layer position of the multilayer substrate. The reference layer position is the depth information of the top substrate, and the target layer position is the depth information of the target layer substrate in the multilayer substrate that does not require circuit connection. Calculate the vertical distance between the reference layer position and the target layer position to obtain the back-drilling depth in the metal via from the top substrate to the target substrate.

5. The back-drilling method according to claim 4, characterized in that, Performing a CT scan on the multilayer substrate to determine the location of the reference layer and the target layer of the multilayer substrate specifically includes: At least three reference points are taken on the upper surface of the top substrate of the multilayer substrate, a reference surface is determined based on the reference points, the depth of the reference surface is calculated, and the position of the reference layer is obtained. The multilayer substrate is subjected to CT scanning to generate three-dimensional position information of the target layer substrate of the multilayer substrate. The depth information of N metal holes on the target layer substrate is extracted from the three-dimensional position information and used as N target layer positions, where N≥1. Calculate the vertical distance between the reference layer position and the target layer position to obtain the back-drilling depth of the metal via from the top substrate to the target substrate, specifically including: Calculate the vertical distance between the reference layer position and each of the target layer positions, and the N back-drilling depths from the top substrate to the target layer substrate in the metal via.

6. The back-drilling method according to claim 1, characterized in that, After performing a CT scan on the multilayer substrate to determine the back-drilling depth of the metal via, the back-drilling method further includes: The QR code containing the back-drilling depth is marked at the corner of the multilayer substrate. The drilling machine scans a QR code located at the corner of the multilayer substrate to obtain the back drilling depth, so that the drilling machine can perform the drilling process according to the back drilling depth.

7. The back-drilling method according to claim 6, characterized in that, Marking the corner of the multilayer substrate with a QR code containing the back-drilling depth includes: The QR code is formed by marking the corner of the multilayer substrate using a laser marking device; or by performing graphic exposure processing on the corner of the multilayer substrate; or by spraying the QR code on the corner of the multilayer substrate using a CT scanner.

8. The back-drilling method according to claim 1, characterized in that, After drilling through the metal vias on the top substrate along the depth direction according to the back-drilling depth to obtain a multilayer circuit board, the method further includes: Obtain reference drilling data for the drilling process, compare the reference drilling data with the detected actual drilling data, obtain the deviation value between the reference drilling data and the actual drilling data, and use a drilling machine to perform drilling compensation processing on the metal through hole that generates the deviation value based on the deviation value. Alternatively, obtain reference drilling data for the drilling process of N multilayer substrates in the current batch, where N≥1, compare the N sets of reference drilling data with the detected actual drilling data, obtain the deviation values ​​between the N sets of reference drilling data and the detected actual drilling data, determine the comprehensive deviation value based on the N deviation values, and perform drilling compensation processing using the metal through-holes of the multilayer substrates in the current batch of the drilling machine based on the comprehensive deviation value.

9. The back-drilling method according to claim 8, characterized in that, The back-drilling depth is obtained by using a drilling rig for network communication, and drilling is performed along the depth direction from the metal through-hole on the top substrate according to the back-drilling depth.

10. The back-drilling method according to claim 3, characterized in that, The process of patterning the surface of the top substrate on a multilayer substrate having the metal through-holes to obtain a multilayer substrate with a surface circuit layer includes: Clean the surface of the top substrate on the multilayer substrate, attach a dry film to the surface of the top substrate, and expose the top substrate with ultraviolet light using an exposure device; then develop the top substrate to obtain a patterned top substrate. The top substrate is subjected to pattern electroplating to remove the dry film, resulting in a multilayer substrate with a surface circuit layer.

11. A multilayer circuit board, characterized in that, The multilayer circuit board is prepared by the back drilling process as described in any one of claims 1-10.

12. A back-drilling drilling device, characterized in that, The back drilling equipment is equipped with an X-ray inspection device, and the back drilling equipment is used to perform back drilling on multilayer circuit boards according to the back drilling processing method according to any one of claims 1-10.

13. The back drilling equipment according to claim 12, characterized in that, The back drilling equipment also includes a controller, the data input terminal of which is connected to the data output terminal of the X-RAY detection equipment for acquiring CT scan data; the data output terminal of the controller is connected to the data input terminal of the drilling rig for outputting the back drilling depth.

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