Printed circuit board back drilling hole depth detection device and operation method thereof

Abstract

The invention relates to a printed circuit board back drilling hole depth detection device and an operation method thereof, and relates to the technical field of depth detection. The device comprises a detection module and a positioning and pressing module. The detection module is provided with a measuring probe, and the positioning hold-down module is provided with a hold-down base. When the pressing base and the measuring probe press the horizontal plane at the same time, the tail end of the probe and the tail end of the base are aligned in the horizontal direction, and the detection module records a first numerical value as a reference position. And then, the detection module and the positioning and pressing module move to the position above the back drilling hole and move downwards, and when the detection module and the positioning and pressing module reach the reference position, the detection module further moves into the back drilling hole in the vertical direction. And when the electric measurement signal of the measurement probe changes, the detection module records a second numerical value and calculates the drilling depth according to the difference between the two numerical values. The method is easy, convenient and rapid to operate, non-destructive and suitable for quality inspection of the depth of the back drilling hole.

Description

Technical Field

[0001] This invention relates to the field of depth detection technology, and in particular to a device for detecting the depth of back-drilled holes in printed circuit boards and its operating method. Background Technology

[0002] In the manufacturing process of printed circuit boards (PCBs), especially those used for high-speed, high-frequency signals, back drilling is often employed to remove non-electrically connected conductive stubs from vias (vias) to suppress signal reflections and improve signal integrity. Precise control of the back drilling depth is crucial to this process. Insufficient drilling depth results in excessively long residual stubs, failing to effectively improve signal quality; excessive drilling may damage inner conductive layers or via walls that need to be preserved, leading to open circuits or decreased reliability. Therefore, accurate measurement of the back drilling depth is a vital step in ensuring product quality.

[0003] Currently, the industry mainly relies on destructive slicing analysis or optical methods with limited precision for depth inspection. The former is costly, inefficient, and cannot inspect all samples, while the latter is susceptible to interference and lacks reliability. Therefore, existing technologies lack a non-destructive, high-precision, and high-efficiency depth inspection method that can meet the needs of online quality inspection. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention is proposed.

[0005] Therefore, the present invention aims to provide a non-destructive, high-precision back-drilling depth detection solution.

[0006] To solve the above technical problems, the present invention provides the following technical solution: a printed circuit board back-drilling hole depth detection device, comprising: a detection module having a probe spindle and a measuring probe connected to the front end of the probe spindle, the detection module being movable in a vertical direction; a positioning and holding module connected to the probe spindle of the detection module and having a holding base, the holding base having a central hole through which the measuring probe passes; when the detection module and the positioning and holding module move synchronously downward in the vertical direction so that the holding base and the measuring probe simultaneously press against a horizontal surface, the probe tip of the measuring probe and the... The base end of the pressure-holding base is aligned in a horizontal direction perpendicular to the vertical direction. The detection module is used to record a first value as a reference position. The detection module and the positioning pressure-holding module are also used to move above the back drill hole and move downward along the vertical direction. When the detection module reaches the reference position of the first value, the detection module further moves into the back drill hole along the vertical direction. When the measurement electrical signal of the measuring probe changes, the detection module is used to record a second value and calculate the drilling depth of the back drill hole based on the difference between the first value and the second value.

[0007] As a preferred embodiment of the printed circuit board back-drilling depth detection device of the present invention, the detection module further includes a displacement recording unit, which is disposed on one side of the probe spindle, and the holding base is provided with a reference mark, which is disposed adjacent to the displacement recording unit.

[0008] In a preferred embodiment of the printed circuit board back-drilling hole depth detection device of the present invention, when the displacement recording unit detects that the reference mark is aligned, the displacement recording unit is used to determine that the detection module has reached the reference position and record the corresponding starting value.

[0009] In a preferred embodiment of the printed circuit board back-drilling depth detection device of the present invention, when the base end of the pressing base and the probe end of the measuring probe are not pressed on the horizontal surface, the base end and the probe end are spaced apart by a protective distance in the vertical direction.

[0010] As a preferred embodiment of the printed circuit board back-drilling hole depth detection device of the present invention, the positioning and holding module further includes a telescopic cylinder, which is disposed between the detection module and the holding base.

[0011] To address the aforementioned problems, the present invention also provides an operation method for a printed circuit board back-drilled hole depth detection device, employing the aforementioned printed circuit board back-drilled hole depth detection device and including the following steps: a reference positioning step: when the end of the base of the holding base and the end of the measuring probe are simultaneously in contact with the horizontal plane, a first value is recorded by the detection module as a reference position; a measurement step: the device is moved above the back-drilled hole, and the device is lowered so that the holding base presses against the surface of the printed circuit board; after reaching the reference position, the detection module is controlled to drive the measuring probe to move vertically into the back-drilled hole; when the measuring electrical signal of the measuring probe changes, a second value is recorded; and a calculation step: the drilling depth is calculated based on the difference between the first value and the second value.

[0012] In a preferred embodiment of the operation method of the printed circuit board back-drilled hole depth detection device of the present invention, the change of the measurement electrical signal is generated based on the resistance conduction or capacitance induction between the measurement probe and the residual copper hole wall in the back-drilled hole.

[0013] The beneficial effects of this invention are as follows: By utilizing the change in electrical signal generated when the measuring probe contacts the residual copper layer inside the back-drilled hole, non-destructive and accurate measurement of the back-drilled hole depth is achieved, making full product inspection possible; by first aligning the measuring probe with the end of the holding base on a horizontal plane to calibrate the reference position, the initial errors caused by circuit board warping, uneven thickness, and clamping deviations are effectively eliminated, transforming absolute depth measurement into high-precision relative displacement measurement, significantly improving the accuracy and repeatability of the test results; at the same time, the device has an ingenious structural design, with the holding base first pressing and fixing the circuit board, and then the measuring probe independently probing downwards. The operation process is simple and highly automated, effectively improving the testing efficiency and equipment stability, making it suitable for online applications, thus providing an efficient and reliable solution for quality control of the back-drilling process of printed circuit boards. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0016] Figure 2 This is a schematic diagram of the overall structure of the present invention and the back-drilled holes of the printed circuit board.

[0017] Figure 3 This is a flowchart of the operation method of the present invention.

[0018] Figure 4 This is one of the schematic diagrams illustrating different stages of the operation method of the device of the present invention.

[0019] Figure 5 This is the second schematic diagram showing different stages of the operation method of the device of the present invention.

[0020] Figure 6 This is the third schematic diagram illustrating different stages of the operation method of the device of the present invention.

[0021] Figure 7 This is the fourth schematic diagram illustrating different stages of the operation method of the device of the present invention.

[0022] Figure 8 This is the fifth schematic diagram illustrating different stages of the operation method of the device of the present invention.

[0023] Figure 9 This is the sixth schematic diagram illustrating different stages of the operation method of the device of the present invention. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive, either alone or selectively, with other embodiments.

[0027] Example 1, referring to Figures 1-2 This is the first embodiment of the present invention. The circuit board back drill hole depth detection device 100 provided in this embodiment is used to measure the actual depth of the back drill hole 210 provided on the printed circuit board 200, so as to determine whether the back drill hole 210 has the correct depth, so as to avoid signal integrity problems caused by incomplete removal of the target conductor layer.

[0028] The device mainly includes a detection module 110 and a positioning and holding module 120.

[0029] The detection module 110 has a probe spindle 112 and a measuring probe 114 fixedly connected to the front end of the probe spindle 112. The detection module 110 can be driven by a drive mechanism (not shown in the figure) such as a motor or lead screw, so that it can accurately reciprocate along the vertical direction D1. The positioning and holding module 120 is connected to the probe spindle 112 of the detection module 110 and has a holding base 122. The holding base 122 has a central hole 121, and the measuring probe 114 passes through this central hole 121, so that the measuring probe 114 can move freely forward and backward along the vertical direction D1 during the detection process without interfering with the holding base 122.

[0030] In a preferred embodiment, the detection module 110 further includes a displacement recording unit 116. This displacement recording unit 116 (e.g., a high-precision grating ruler system) is fixedly mounted on one side of the probe spindle 112 and is used to accurately measure and record the displacement of the probe spindle 112 in the vertical direction D1. Correspondingly, a reference mark 124 is provided on the holding base 122 of the positioning and holding module 120. The position of the reference mark 124 corresponds to the reading position of the displacement recording unit 116. When the detection module 110 and the positioning and holding module 120 move downwards synchronously to a preset height, the reference mark 124 will point to a specific scale or value on the displacement recording unit 116. At this time, the displacement recording unit 116 can determine that the detection module 110 has reached the reference position and record this position value as a reference benchmark (i.e., the first value) for subsequent hole depth measurement.

[0031] In another preferred embodiment, the positioning and holding module 120 further includes a telescopic cylinder 126. This telescopic cylinder 126 is positioned between the detection module 110 (specifically, the probe spindle 112) and the holding base 122, allowing the holding base 122 to extend or retract relative to the probe spindle 112. When the detection module 110 and the positioning and holding module 120 move downwards along the vertical direction D1, and the holding base 122 presses against the surface 220 of the printed circuit board, the probe spindle 112 and the measuring probe 114 can overcome the cylinder resistance and continue to move independently downwards under the buffering effect of the telescopic cylinder 126, penetrating the back-drilled hole 210 of the printed circuit board for hole depth measurement. This design ensures that the holding base 122 remains stable after pressing against the circuit board surface, while the measuring probe 114 can move independently, effectively preventing measurement errors caused by circuit board warping or external force interference, and also reducing the risk of damage to the circuit board due to excessive pressure concentration.

[0032] like Figure 4As shown, in the initial state, when the base end 125 of the pressing base 122 and the probe end 115 of the measuring probe 114 are not yet pressed against the horizontal plane H, there is a protective distance A between them in the vertical direction D1. This distance ensures that during the start-up or movement of the device, the sensitive measuring probe 114 will not bend or be damaged due to premature accidental contact with the working surface, thereby ensuring the service life of the probe and the accuracy of the measurement.

[0033] The device operates as follows: First, a reference position is calibrated. The detection module 110 and the positioning and holding module 120 are moved synchronously downwards along the vertical direction D1 until the base end 125 of the holding base 122 and the probe end 115 of the measuring probe 114 simultaneously contact a high-precision horizontal plane H (e.g., a machine tool calibration platform). At this point, the probe end 115 and the base end 125 are aligned in the horizontal direction D2, meaning they are on the same height plane. The detection module 110 (via the displacement recording unit 116) immediately records this position as the first value (i.e., the reference position).

[0034] After calibration, actual measurements are performed. The entire device is moved above the printed circuit board 200 to be measured and precisely aligned with the back drill hole 210. Then, the device is moved downwards again along the vertical direction D1. When the reading of the displacement recording unit 116 shows that the probe module 110 has descended to the previously recorded first value (i.e., the reference position), it means that the holding base 122 is now stably pressed onto the surface 220 of the printed circuit board. This step cleverly eliminates the initial positioning error caused by uneven thickness, warping, or clamping deviation of the circuit board itself.

[0035] Next, with the holding base 122 stationary, the detection module 110 drives the measuring probe 114 to continue moving independently downwards in the vertical direction D1, allowing it to enter the back-drilled hole 210. When the probe tip 115 of the measuring probe 114 contacts the residual copper hole wall 230 at the bottom of the back-drilled hole 210, it triggers a sudden change in the measurement electrical signal. This change can be a sudden decrease in resistance (forming a conductive loop) or a change in coupling capacitance. The detection module 110 detects this change and immediately records the position at that moment as a second value. Finally, the calculation module (which can be integrated into the detection module 110) calculates the difference between the first value and the second value to accurately determine the actual depth of the back-drilled hole 210.

[0036] Example 2, refer to Figures 3-9 This is the second embodiment of the present invention. This embodiment provides an operating method for operating the aforementioned circuit board back-drill hole depth detection device to measure the depth of the back-drill hole 210 on the printed circuit board. The detailed steps of this method are as follows:

[0037] S1: Move the detection module 110 and the positioning and holding module 120 downward synchronously along the vertical direction D1 until the holding base 122 of the positioning and holding module 120 and the measuring probe 114 of the detection module 110 are simultaneously pressed on a high-precision horizontal plane H.

[0038] S2: When the probe end 115 of the measuring probe 114 is aligned with the base end 125 of the pressing base 122 in the horizontal direction D2, the detection module 110 records the first value as the reference position for the entire measurement process.

[0039] S3: Move the detection module 110 and the positioning and holding module 120 to directly above the back drill hole 210 on the printed circuit board 200, and then move them downwards again along the vertical direction D1. When the detection module 110 (determined by the displacement recording unit 116) reaches the reference position corresponding to the first value, control the detection module 110 to move further along the vertical direction D1, so that the measuring probe 114 enters the interior of the back drill hole 210 alone.

[0040] S4: When the measurement electrical signal of the measuring probe 114 changes (for example, due to resistance conduction or capacitance induction caused by the probe tip 115 contacting the residual copper hole wall 230), the detection module 110 immediately records the second value. Subsequently, the drilling depth of the back drill hole 210 of the printed circuit board is calculated based on the difference between the first value and the second value.

[0041] In one specific embodiment of the method, the detection module 110 uses its displacement recording unit 116 to accurately determine the reference position. When the displacement recording unit 116 detects that the reference mark 124 set on the pressure base 122 is aligned, it determines that the detection module 110 has descended to the reference position and records the corresponding initial value (i.e., the first value).

[0042] During the measurement process, the electrical signal of the measuring probe 114 changes based on its electrical reaction with the residual copper hole wall 230 in the back drilled hole. When the two come into contact or are very close, a resistive conduction or capacitive induction is triggered. This change is sensitively captured by the detection module 110 as a trigger signal for recording a second value.

[0043] The method also utilizes a retractable cylinder 126 in the positioning and holding module 120. After the device moves down and the holding base 122 presses against the surface 220 of the printed circuit board, the retractable cylinder 126 allows the probe spindle 112 and the measuring probe 114 to continue to descend independently overcoming pneumatic resistance, while the holding base 122 remains pressed, ensuring the stability of the circuit board during the measurement process and thus improving the measurement accuracy.

[0044] In summary, through the synergistic effect of the above-mentioned device and method, the present invention transforms the hole depth, which is difficult to measure directly, into a high-precision relative displacement measurement, effectively corrects various potential errors, and realizes rapid, accurate, and non-destructive detection of back-drilled hole depth.

[0045] It should be noted that the above 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A device for detecting the depth of back-drilled holes in printed circuit boards, characterized in that: include, The detection module (110) has a probe spindle (112) and a measuring probe (114) connected to the front end of the probe spindle (112). The detection module (110) is capable of moving in the vertical direction (D1). The positioning and holding module (120) is connected to the probe spindle (112) of the detection module (110) and has a holding base (122) having a central hole (121) through which the measuring probe (114) passes. When the detection module (110) and the positioning and holding module (120) move synchronously downward along the vertical direction (D1) so that the holding base (122) and the measuring probe (114) simultaneously press against the horizontal surface (H), the probe end (115) of the measuring probe (114) and the base end (125) of the holding base (122) are aligned in the horizontal direction (D2) perpendicular to the vertical direction (D1), and the detection module (110) is used to record the first value as a reference position; The detection module (110) and the positioning and holding module (120) are also used to move above the back drill hole (210) and move downward along the vertical direction (D1). When the detection module (110) reaches the reference position of the first value, the detection module (110) further moves along the vertical direction (D1) into the back drill hole (210). When the measurement electrical signal of the measuring probe (114) changes, the detection module (110) is used to record the second value and calculate the drilling depth of the back drill hole (210) based on the difference between the first value and the second value.

2. The printed circuit board back-drilling hole depth detection device as described in claim 1, characterized in that: The detection module (110) also has a displacement recording unit (116), which is located on one side of the probe spindle (112). The pressure base (122) is provided with a reference mark (124), and the reference mark (124) is located adjacent to the displacement recording unit (116).

3. The printed circuit board back-drilling hole depth detection device as described in claim 2, characterized in that: When the displacement recording unit (116) detects that the reference mark (124) is aligned, the displacement recording unit (116) is used to determine that the detection module (110) has reached the reference position and record the corresponding starting value.

4. The printed circuit board back-drilling hole depth detection device as described in claim 3, characterized in that: When the base end (125) of the pressing base (122) and the probe end (115) of the measuring probe (114) are not pressed against the horizontal plane (H), the base end (125) and the probe end (115) are separated by a protective distance (A) in the vertical direction (D1).

5. The printed circuit board back-drilling hole depth detection device as described in claim 4, characterized in that: The positioning and holding module (120) also includes a telescopic cylinder (126), which is disposed between the detection module (110) and the holding base (122).

6. An operating method for a printed circuit board back-drilling hole depth detection device, characterized in that, The method employs the printed circuit board back-drilling hole depth detection device as described in any one of claims 1 to 5, and includes the following steps: Reference positioning steps: When the base end (125) of the pressure base (122) and the end of the measuring probe (114) simultaneously contact the horizontal plane (H), the first value is recorded by the detection module (110) as the reference position; Measurement steps: Move the back drill hole depth detection device (100) of the printed circuit board above the back drill hole (210), and move the device down so that the pressing base (122) presses against the surface (220) of the printed circuit board. After the detection module (110) reaches the reference position, it drives the measuring probe (114) to move in the vertical direction (D1) into the back drill hole (210); When the measuring electrical signal of the measuring probe (114) changes, a second value is recorded; and, Calculation steps: Calculate the borehole depth based on the difference between the first value and the second value.

7. The operation method of the printed circuit board back-drilling hole depth detection device as described in claim 6, characterized in that: The change in the measured electrical signal is generated based on the resistance conduction or capacitance induction between the measuring probe (114) and the residual copper hole wall (230) in the back drill hole (210).

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