Server PCB back drilling reliability real-time monitoring method and system

Abstract

The invention belongs to the technical field of PCB back drill monitoring, and discloses a server PCB back drill reliability real-time monitoring method and system.The method comprises the steps that a set of back drill Coupon is designed at the edge of a PCB, and back drill holes comprise open circuit design and short circuit design; the open circuit design indicates back drilling of a layer needing to be drilled and broken, and the short circuit design indicates back drilling of a stub layer circuit which cannot be drilled and broken; and after etching, a universal meter is used for measuring the Coupon, and the back drilling depth is detected. The reliability of the depth of the back drilling hole is verified through the back drilling detection device, the back drilling defects can be positioned in real time in the back drilling production process, monitoring of the back drilling quality of all production boards is facilitated, the detection time is shortened, and the production efficiency is improved. According to the real-time monitoring method suitable for the server PCB back drilling process, the quality problem caused by drilling missing or non-in-place drilling in the back drilling process can be prevented, the yield and reliability of a high-density PCB are improved, and the efficiency is improved by 90% compared with a traditional monitoring mode.

Description

Technical Field

[0001] The present invention belongs to the technical field of PCB backdrill monitoring, and in particular relates to a method and system for real-time monitoring of server PCB backdrill reliability. Background Art

[0002] Backdrilling, a recently emerging process in printed circuit board (PCB) manufacturing, removes copper from through-hole sections that don't serve any connection or transmission function. This prevents residual metal from causing reflections, scattering, and signal delays. However, during backdrilling, backdrill misalignment is a common occurrence. During backdrilling of a PCB, the back-drilled hole may deviate from the corresponding drilled hole on the PCB, resulting in backdrill misalignment, which can affect the final quality of the PCB.

[0003] Traditional methods rely on manual sectioning visual inspection or offline electrical testing, which are inefficient, have poor real-time performance, and are unable to locate backdrilling defects in real time during the process. Therefore, a real-time monitoring solution integrated into the manufacturing process is urgently needed. Summary of the Invention

[0004] To overcome the problems existing in the related art, the present invention discloses a method and system for real-time monitoring of server PCB backdrill reliability. The technical solution is as follows:

[0005] The present invention is implemented as follows: a method for real-time monitoring of server PCB backdrill reliability includes:

[0006] Design a set of backdrill coupons at the edge of the PCB board. The backdrill holes include open circuit design and short circuit design. The open circuit design indicates the layer that needs to be drilled through by the backdrill, and the short circuit design indicates the stub layer circuit that cannot be drilled through by the backdrill.

[0007] After etching, use a multimeter to measure the coupon and check the backdrill depth.

[0008] In the outer layer graphic design of the Top / bot surface, the VIA hole represents the hole D that needs to be back-drilled, and the etched characters G, O, and S represent ground, open circuit, and short circuit, respectively. The hole size is 1.1 mm.

[0009] In the inner layer graphic design that needs to be drilled through by back drilling, the back drill hole position and the outer layer etched character O are connected by a line; on the layer where the back drill hole is located, a 5-mil line width wire is designed to connect the back drill hole pad and the copper foil of the outer layer etched character O; the copper foil of the outer layer etched character O meets the minimum rectangular area of ​​20 mil × 20 mil.

[0010] In the inner layer graphics that do not need to be drilled through during back drilling, the back drill hole position is connected to the outer layer etched character S using a line; on the layer where the back drill hole is located, a 5 mil line width wire is designed to connect the back drill hole pad and the copper foil of the outer layer etched character S; the copper foil of the outer layer etched character S is on the same network as the layer where the back drill hole is located.

[0011] In the graphic design of other inner layers, the back drill and the outer layer etched character O / S do not need to be connected by lines, and are electrically isolated from the character O / S, with an insulation spacing of ≥10mil.

[0012] The coupon measurement process includes:

[0013] Use a multimeter to measure the outer layer etched character O hole. If the buzzer sounds, it is normal. If the buzzer is silent, it is abnormal, indicating that the backdrill has drilled through the required layer.

[0014] Use a multimeter to measure the outer layer etched character S hole. If the buzzer is silent, it is normal. If the buzzer sounds, it is abnormal, indicating that the back drilling has caused residual copper on the hole wall or the required layer has not been drilled.

[0015] Furthermore, the backdrill deviation detection process when measuring the S-hole etching character using a multimeter includes:

[0016] A backdrill detection device is arranged on the edge of the front side of the PCB. The backdrill detection device includes a backdrill detection hole and a circular deviation indicator module surrounding the backdrill detection hole for detecting the alignment of the backdrill.

[0017] The backdrill detection device further includes an identification module, wherein the identification module is used to identify a preset backdrill offset corresponding to each backdrill detection hole;

[0018] The backdrill detection holes are sequentially passed through in ascending order of the preset backdrill offsets. When the substrate around the backdrill detection holes is observed through the backdrill holes, the backdrill offset is the preset backdrill offset.

[0019] The circular deviation indicator module consists of multiple sets of concentric rings, with the ring spacing equal to the preset deviation increment. The actual deviation of the backdrill is determined by observing the damage of the rings after drilling.

[0020] Mark the module adjacent to the back-drilled detection hole, use laser engraving text, and arrow to mark the offset direction;

[0021] The backdrill deviation detection process specifically includes:

[0022] (1) Visual pre-alignment:

[0023] Use an optical positioning system to identify the identification module and determine the direction and size of the preset offset;

[0024] The spacing between embedded feature markers on each layer = 2 × maximum backdrill offset

[0025] (2) Back drilling:

[0026] Drill holes in order from small to large according to the preset offset;

[0027] (3) Offset determination:

[0028] When substrate exposure is first observed, the current preset offset is recorded as the actual offset;

[0029] (4) Data Recording:

[0030] Record the offset and direction and generate process compensation parameters.

[0031] After measuring the coupon with a multimeter, the backdrill depth detection process includes:

[0032] Obtain the through-hole distribution of the PCB board to be tested after backdrilling, as well as the position and direction of the backdrilled holes;

[0033] Based on the through-hole distribution and the position and direction of the back-drilled holes, the optimal scanning angle of the laser scanner is calculated, the scanning direction and scanning base point are determined, and a multi-angle scanning plan is generated to achieve scanning path optimization;

[0034] According to the optimized path of the laser scanner, the point cloud data of the through-hole surface and the back-drilled surface of the PCB board to be inspected are collected, and the point cloud data are converted into a depth map;

[0035] Determine the depth data of the back-drilled holes of the PCB board to be inspected based on the back-drilled hole direction of the PCB board to be inspected, the back-drilled depth image of the back-drilled surface, and the through-hole depth image of the through-hole surface.

[0036] Furthermore, collecting the point cloud data of the PCB board to be inspected and converting the point cloud data into a depth map includes:

[0037] The multi-view point clouds are registered to the same coordinate system using the ICP algorithm, and point cloud clusters with too low density are deleted using radius filtering. Poisson reconstruction is performed on the point clouds to generate a continuous surface model.

[0038] The 3D point cloud is projected onto a 2D grid, and grid cells with missing data are filled using neighboring interpolation or curvature-based prediction; depth maps from different perspectives are weightedly fused to output a depth map.

[0039] Another object of the present invention is to provide a server PCB backdrill reliability real-time monitoring system, which is used to control the server PCB backdrill reliability real-time monitoring method, and the system includes:

[0040] The backdrill design module is used to design a set of backdrill coupons at the edge of the PCB board. The backdrill holes include open circuit design and short circuit design. The open circuit design indicates the layer that needs to be drilled through by the backdrill, and the short circuit design indicates the stub layer circuit that cannot be drilled through by the backdrill.

[0041] The backdrill depth detection module is used to measure the coupon with a multimeter after etching and detect the backdrill depth.

[0042] In combination with all the above technical solutions, the beneficial effects of the present invention are as follows:

[0043] First, the present invention designs a set of back-drilled coupons at the edge of the PCB board. The back-drilled holes are divided into two designs: an open circuit design, indicating the layer that needs to be drilled through by the back drill; and a short circuit design, indicating the stub layer circuit that cannot be drilled through by the back drill. After etching, the coupon is measured using a multimeter.

[0044] The present invention utilizes a backdrilling detection device to verify the reliability of backdrilled hole depth, enabling effective alignment and detection, facilitating operational workflows and facilitating monitoring of backdrilled quality across all produced boards. The detection method of the present invention significantly reduces inspection time and accuracy, improves production efficiency, and facilitates quality monitoring.

[0045] Second, the backdrilling detection device of the present invention realizes rapid visual detection of backdrilling offset through the collaborative design of the deviation indicator ring and the identification module. Its advantages include:

[0046] 1. No need to destroy the PCB: the process status is evaluated only by the board edge inspection device.

[0047] 2. Real-time feedback: Drilling parameter compensation values ​​are generated immediately.

[0048] 3. High compatibility: suitable for various PCB types such as HDI and high-frequency materials.

[0049] The present invention is applicable to a real-time monitoring method for a server PCB backdrilling process, which can prevent quality problems caused by drilling omissions or incomplete drilling during the backdrilling process, and improve the yield and reliability of high-density PCBs.

[0050] Third, considering the technical solution as a whole or from the perspective of the product, the technical effects and advantages of the technical solution to be protected by the present invention are described in detail as follows:

[0051] 1. The present invention can locate backdrilling defects in real time during the backdrilling process;

[0052] 2. The present invention is 90% more efficient than traditional monitoring methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure;

[0054] Figure 1 This is a flow chart of a method for real-time monitoring of server PCB backdrill reliability provided by an embodiment of the present invention;

[0055] Figure 2 This is a schematic diagram of the outer layer graphic design of the Top / bot surface provided by an embodiment of the present invention;

[0056] Figure 3 This is a schematic diagram of a graphic design after back drilling of the top / bot surface provided by an embodiment of the present invention;

[0057] Figure 4 This is a schematic diagram of the inner layer graphic design of the layer to be drilled through by back drilling provided by an embodiment of the present invention;

[0058] Figure 5 This is a schematic diagram of a layer-by-layer graphic design for back drilling without drilling through provided by an embodiment of the present invention;

[0059] Figure 6 It is a schematic diagram of the graphic design of other layers provided by an embodiment of the present invention;

[0060] Figure 7 1 is a schematic diagram of Coupon measurement results provided by an embodiment of the present invention; wherein, FIG (a) is a schematic diagram of etching character O, and FIG (b) is a schematic diagram of etching character S. DETAILED DESCRIPTION

[0061] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0062] Example 1, as Figure 1 As shown, the server PCB backdrilling reliability real-time monitoring method provided by the embodiment of the present invention specifically includes the following steps:

[0063] S1, design a set of backdrill coupons at the edge of the PCB board. The backdrill holes include open circuit design and short circuit design. The open circuit design indicates the layer that needs to be drilled through by the backdrill, and the short circuit design indicates the stub layer circuit that cannot be drilled through by the backdrill.

[0064] S2, after etching, use a multimeter to measure the coupon and check the backdrill depth.

[0065] The oupon design requirements provided by the embodiment of the present invention are as follows:

[0066] Figure 2 Design of the outer layer graphics of the Top / bot surface: VIA holes represent holes D that need to be back-drilled, and the etched characters G, O, and S represent ground, open, and short circuit respectively. The hole diameter is 1.1mm.

[0067] Figure 3 Graphic design for the top / bot surface after back drilling.

[0068] Figure 4 Design the inner layer pattern for the layer through which backdrilling will penetrate, and use a trace to connect the backdrill hole location to the outer layer etched O. On the layer where the backdrill hole is located, design a 5-mil-wide wire to connect the backdrill hole pad to the outer layer etched O's copper. The outer layer etched O's copper should fit within a minimum 20-mil x 20-mil rectangular area.

[0069] Figure 5 Design inner layer graphics for layers that don't need to be drilled through for backdrilling. Use a trace to connect the backdrill hole location to the outer layer etched character S. On the layer where the backdrill hole is located, design a 5-mil-wide trace to connect the backdrill hole pad to the outer layer copper etched with the character S. The outer layer copper etched with the character S is on the same network as the backdrill hole layer.

[0070] Figure 6 For the inner layer graphic design of other layers: back drilling and outer layer etching character O / S do not need to use line connection, and maintain electrical isolation from the character O / S, with an insulation spacing of ≥10mil.

[0071] The coupon measurement method provided by the embodiment of the present invention is as follows:

[0072] Etched character O: Use a multimeter to measure this hole. If the buzzer sounds, it is normal. If there is no sound, it is abnormal, indicating that the back drill has drilled through the required layer. Figure 7 (a)

[0073] Etched character S: Use a multimeter to measure this hole. If the buzzer does not sound, it is normal. If it sounds, it is abnormal, indicating that the back drilling has caused residual copper on the hole wall or the required layer has not been drilled. Figure 7 (b) shown.

[0074] The present invention uses a multimeter to measure the backdrill deviation detection process when etching the character S hole, which includes:

[0075] A backdrill detection device is arranged on the edge of the front side of the PCB. The backdrill detection device includes a backdrill detection hole and a circular deviation indicator module surrounding the backdrill detection hole for detecting the alignment of the backdrill.

[0076] The backdrill detection device further includes an identification module, wherein the identification module is used to identify a preset backdrill offset corresponding to each backdrill detection hole;

[0077] The backdrill detection holes are sequentially passed through in ascending order of the preset backdrill offsets. When the substrate around the backdrill detection holes is observed through the backdrill holes, the backdrill offset is the preset backdrill offset.

[0078] The circular deviation indicator module consists of multiple sets of concentric rings, with the ring spacing equal to the preset deviation increment. The actual deviation of the backdrill is determined by observing the damage of the rings after drilling.

[0079] The identification module is adjacent to the back-drilled detection hole, and the text is engraved by laser, and the arrow marks the offset direction.

[0080] The backdrilling deviation detection process of the present invention specifically includes:

[0081] (1) Visual pre-alignment:

[0082] Use an optical positioning system to identify the identification module and determine the direction and size of the preset offset;

[0083] The spacing between embedded feature markers on each layer = 2 × maximum backdrill offset

[0084] (2) Back drilling:

[0085] Drill holes in order from small to large according to the preset offset;

[0086] (3) Offset determination:

[0087] When substrate exposure is first observed, the current preset offset is recorded as the actual offset;

[0088] (4) Data Recording:

[0089] Record the offset and direction and generate process compensation parameters.

[0090] After measuring the coupon using a multimeter, the backdrilling depth detection process of the present invention includes:

[0091] Obtain the through-hole distribution of the PCB board to be tested after backdrilling, as well as the position and direction of the backdrilled holes;

[0092] Based on the through-hole distribution and the position and direction of the back-drilled holes, the optimal scanning angle of the laser scanner is calculated, the scanning direction and scanning base point are determined, and a multi-angle scanning plan is generated to achieve scanning path optimization;

[0093] According to the optimized path of the laser scanner, the point cloud data of the through-hole surface and the back-drilled surface of the PCB board to be inspected are collected, and the point cloud data are converted into a depth map;

[0094] Determine the depth data of the back-drilled holes of the PCB board to be inspected based on the back-drilled hole direction of the PCB board to be inspected, the back-drilled depth image of the back-drilled surface, and the through-hole depth image of the through-hole surface.

[0095] The present invention collects point cloud data of the PCB board to be inspected and converts the point cloud data into a depth map, including:

[0096] The multi-view point clouds are registered to the same coordinate system using the ICP algorithm, and point cloud clusters with too low density are deleted using radius filtering. Poisson reconstruction is performed on the point clouds to generate a continuous surface model.

[0097] The 3D point cloud is projected onto a 2D grid, and grid cells with missing data are filled using neighboring interpolation or curvature-based prediction; depth maps from different perspectives are weightedly fused to output a depth map.

[0098] In embodiment 2, a server PCB backdrilling reliability real-time monitoring system provided by an embodiment of the present invention includes:

[0099] The backdrill design module is used to design a set of backdrill coupons at the edge of the PCB board. The backdrill holes include open circuit design and short circuit design. The open circuit design indicates the layer that needs to be drilled through by the backdrill, and the short circuit design indicates the stub layer circuit that cannot be drilled through by the backdrill.

[0100] The backdrill depth detection module is used to measure the coupon with a multimeter after etching and detect the backdrill depth.

[0101] The above description is only a preferred specific implementation method of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A real-time monitoring method for server PCB backdrill reliability, characterized in that: The method includes: Design a set of backdrill coupons at the edge of the PCB board. The backdrill holes include open circuit design and short circuit design. The open circuit design indicates the layer that needs to be drilled through by the backdrill, and the short circuit design indicates the stub layer circuit that cannot be drilled through by the backdrill. After etching, use a multimeter to measure the coupon and check the backdrill depth.

2. The method for real-time monitoring of server PCB backdrill reliability according to claim 1, characterized in that: In the outer layer graphic design of the Top / bot surface, the VIA hole represents the hole D that needs to be back-drilled, and the etched characters G, O, and S represent ground, open circuit, and short circuit, respectively. The hole size is 1.1 mm.

3. The method for real-time monitoring of server PCB backdrill reliability according to claim 1, characterized in that: In the inner layer graphic design that needs to be drilled through by back drilling, the back drilling hole position is connected to the outer layer etched character O using a line; On the layer where the back-drilled hole is located, a 5-mil-wide wire is designed to connect the back-drilled hole pad and the outer copper sheet with the etched character O. The outer copper sheet with the etched character O meets the minimum rectangular area of ​​20 mil × 20 mil.

4. The method for real-time monitoring of server PCB backdrill reliability according to claim 1, characterized in that: In the inner layer graphics that do not need to be drilled through during back drilling, the back drilling hole position is connected to the outer layer etched character S using a line; On the layer where the back drill hole is located, a 5 mil line width wire is designed to connect the back drill hole pad and the outer layer copper sheet with the etched character S; the outer layer copper sheet with the etched character S is on the same network as the layer where the back drill hole is located.

5. The method for real-time monitoring of server PCB backdrill reliability according to claim 1, characterized in that: In the graphic design of other inner layers, the back drill and the outer layer etched character O / S do not need to be connected by lines, and are electrically isolated from the character O / S, with an insulation spacing of ≥10mil.

6. The method for real-time monitoring of server PCB backdrill reliability according to claim 1, characterized in that: The coupon measurement process includes: Use a multimeter to measure the outer layer etched character O hole. If the buzzer sounds, it is normal. If the buzzer is silent, it is abnormal, indicating that the backdrill has drilled through the required layer. Use a multimeter to measure the outer layer etched character S hole. If the buzzer is silent, it is normal. If the buzzer sounds, it is abnormal, indicating that the back drilling has caused residual copper on the hole wall or the required layer has not been drilled.

7. The method for real-time monitoring of server PCB backdrill reliability according to claim 6, characterized in that: The backdrill offset detection process for etching character S holes using a multimeter includes: A backdrill detection device is arranged on the edge of the front side of the PCB. The backdrill detection device includes a backdrill detection hole and a circular deviation indicator module surrounding the backdrill detection hole for detecting the alignment of the backdrill. The backdrill detection device further includes an identification module, wherein the identification module is used to identify a preset backdrill offset corresponding to each backdrill detection hole; The backdrill detection holes are sequentially passed through in ascending order of the preset backdrill offsets. When the substrate around the backdrill detection holes is observed through the backdrill holes, the backdrill offset is the preset backdrill offset. The circular deviation indicator module consists of multiple sets of concentric rings, with the ring spacing equal to the preset deviation increment. The actual deviation of the backdrill is determined by observing the damage of the rings after drilling. Mark the module adjacent to the back-drilled detection hole, use laser engraving text, and arrow to mark the offset direction; The backdrill deviation detection process specifically includes: (1) Visual pre-alignment: Use an optical positioning system to identify the identification module and determine the direction and size of the preset offset; The spacing between embedded feature markers on each layer = 2 × maximum backdrill offset (2) Back drilling: Drill holes in order from small to large according to the preset offset; (3) Offset determination: When substrate exposure is first observed, the current preset offset is recorded as the actual offset; (4) Data Recording: Record the offset and direction and generate process compensation parameters.

8. The method for real-time monitoring of server PCB backdrill reliability according to claim 1, characterized in that: After measuring the coupon with a multimeter, the backdrill depth detection process includes: Obtain the through-hole distribution of the PCB board to be tested after backdrilling, as well as the position and direction of the backdrilled holes; Based on the through-hole distribution and the position and direction of the back-drilled holes, the optimal scanning angle of the laser scanner is calculated, the scanning direction and scanning base point are determined, and a multi-angle scanning plan is generated to achieve scanning path optimization; According to the optimized path of the laser scanner, the point cloud data of the through-hole surface and the back-drilled surface of the PCB board to be inspected are collected, and the point cloud data are converted into a depth map; Determine the depth data of the back-drilled holes of the PCB board to be inspected based on the back-drilled hole direction of the PCB board to be inspected, the back-drilled depth image of the back-drilled surface, and the through-hole depth image of the through-hole surface.

9. The method for real-time monitoring of server PCB backdrill reliability according to claim 8, characterized in that: Collecting point cloud data of the PCB to be inspected and converting the point cloud data into a depth map includes: The multi-view point clouds are registered to the same coordinate system using the ICP algorithm, and point cloud clusters with too low density are deleted using radius filtering. Poisson reconstruction is performed on the point clouds to generate a continuous surface model. The 3D point cloud is projected onto a 2D grid, and grid cells with missing data are filled using neighboring interpolation or curvature-based prediction; depth maps from different perspectives are weightedly fused to output a depth map.

10. A server PCB backdrill reliability real-time monitoring system, characterized in that: The system is used to control the real-time monitoring method for server PCB backdrill reliability according to any one of claims 1 to 9, and the system includes: The backdrill design module is used to design a set of backdrill coupons at the edge of the PCB board. The backdrill holes include open circuit design and short circuit design. The open circuit design indicates the layer that needs to be drilled through by the backdrill, and the short circuit design indicates the stub layer circuit that cannot be drilled through by the backdrill. The backdrill depth detection module is used to measure the coupon with a multimeter after etching and detect the backdrill depth.

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