Non-destructive quality inspection method and defect determination method for back-drilled hole of printed circuit board

Abstract

A non-destructive quality inspection method and a defect determination method for a back-drilled hole of a printed circuit board (PCB). The non-destructive quality inspection method comprises: using X-rays to obtain a cross-sectional image of a back-drilled hole under inspection (S110); on the cross-sectional image, using a surface layer where a drilling entry surface of the back-drilled hole is located as a reference layer, and on the basis of the layer level of a target layer and theoretical thicknesses of multiple layers between the target layer and the reference layer, calculating a theoretical depth of the target layer, so as to initially locate the target layer (S120); using the theoretical depth of the target layer as a reference, searching within an actual deviation range of the target layer for a layer level where abrupt changes in grayscale values occur, and determining the layer level where abrupt changes in grayscale values occur as an actual target layer (S130); and identifying a tip Ltip of a stub tip portion on the cross-sectional image, and measuring a distance between the tip Ltip of the stub tip portion and the target layer, so as to obtain a stub length Lstub (S140).

Description

Nondestructive testing and defect determination method for back drilling quality of printed circuit boards

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on November 21, 2023, with application number 202311549514.8, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of printed circuit boards (PCBs), and for example, to a method for non-destructive testing and defect determination of back-drilled holes in PCBs. Background Art

[0003] On multilayer printed circuit boards, signal transmission between layers is achieved through metallized through-holes. For signal conduction between designated layers, the through-hole wall metal is removed through a back-drilling process to specifically cut off the layers that do not need to be connected or transmitted. This process uses a drill bit larger than the through-hole diameter to perform controlled-depth drilling at the original through-hole position, removing the hole wall metal (hole wall copper) connecting non-designated layers, so that the remaining hole wall metal can achieve circuit conduction between local layers, thereby avoiding reflection, scattering and delay of high-speed signal transmission, which causes signal "distortion".

[0004] Back-drilled hole quality is inspected by creating a back-drilled hole slice to obtain a half-hole cross-section. The target layer is first determined, the tip of the stump is located, and the actual stump length is measured and compared with the target stump length. If the error is within a reasonable range, the stump is considered qualified. This grinding and measuring method requires manual grinding and measurement. When working with multi-layer printed circuit boards with many layers, manual layer counting can lead to errors in target layer positioning, affecting the stump length measurement results.

[0005] Summary of the Invention

[0006] The present application provides a method for nondestructive testing and defect determination of back-drilled holes in a PCB. The method can calculate the drilling depth D 孔深 , residual pile length L 残桩 and the distance H from the actual target layer to the reference layer 目标层 (Distance from target layer to surface copper layer), and thus determine the defect of back drilling hole according to the above value.

[0007] This application provides a nondestructive testing method for back-drilling quality of a PCB, comprising:

[0008] Use X-ray to obtain a cross-sectional image of the back-drilled hole to be tested;

[0009] On the cross-sectional image, the surface layer where the back-drilled hole is drilled is used as the reference layer. The theoretical depth of the target layer is calculated according to the layer of the target layer and the theoretical thickness of the multiple layers between the target layer and the reference layer, thereby preliminarily locating the target layer.

[0010] Based on the theoretical depth of the target layer, the layer with grayscale value mutation is searched according to the actual deviation range of the target layer, and the layer with grayscale value mutation is determined as the actual target layer;

[0011] Identify the tip L of the stump tip on the cross-sectional image 尖端 , and measure the tip L of the stump tip 尖端 The distance from the target layer to obtain the residual pile length L 残桩 .

[0012] In some embodiments, the measurement reference point of the actual target layer is the middle position L of the actual target layer. m_ct , the actual target layer copper thickness Cu is measured Lm , length of residual pile L 残桩 =|L 尖端 -L m_ct |-0.5Cu Lm .

[0013] In some embodiments, the middle position L of the actual target layer m_ct It is calculated by the theoretical depth of the target layer*(1±0.08).

[0014] The present application also provides a method for determining PCB back-drilling defects, which, combined with the above-mentioned non-destructive testing method for PCB back-drilling quality, includes:

[0015] According to the processing requirements of the multilayer printed circuit board, the maximum threshold value A and the minimum threshold value B of the stump length are set;

[0016] Determine the length of the residual pile L 残桩 Is it within (B, A)?

[0017] The distance between the tip of the residual pile and the reference layer is measured as the drilling depth D 孔深 , the distance H from the actual target layer to the reference layer is measured 目标层 , calculate the drilling depth threshold D 阈值 (H 目标层 -A,H 目标层 -B), then determine the drilling depth D 孔深 Is it in (H 目标层 -A,H 目标层 -B) inside;

[0018] If L 残桩 Within (B, A) and drill depth D 孔深 Also in (H 目标层-A,H 目标层 -B) is considered qualified;

[0019] If L 残桩 Not within (B, A), and the drilling depth is D 孔深 Nor in (H 目标层 -A,H 目标层 -B), it is judged as unqualified and according to L 残桩 Greater than A or less than B and D 孔深 Greater than H 目标层 -B or less than H 目 标层 -A: The defect type is determined to be too deep or too shallow;

[0020] If L 残桩 Within (B, A) and drill depth D 孔深 Not in (H 目标层 -A,H 目标层 -B), it is judged as unqualified, and the cause of the defect is the wrong positioning of the target layer or the wrong drilling surface;

[0021] If L 残桩 Not within (B, A), and the drilling depth is D 孔深 In (H 目标层 -A,H 目标层 -B), it is judged as unqualified and the cause of the defect is drilling deviation.

[0022] In some embodiments, the thickness of the reference layer Cu is measured top The measurement reference point of the obtained reference layer is the middle position L of the reference layer top_ct ; Drilling depth D 孔深 =|L top_ct -L 尖端 |+Cu top *0.5.

[0023] In some embodiments, the measurement reference point of the actual target layer is measured to be the middle position L of the actual target layer. m_ct , the distance H from the actual target layer to the reference layer 目标层 =|L top_ct -L m_ct |+Cu top *0.5-Cu Lm *0.5, Cu Lm The copper thickness of the copper layer of the actual target layer.

[0024] In some embodiments, when the upper surface and the lower surface of the PCB are back-drilled respectively, the back-drilled holes of the upper and lower surfaces of the PCB are inspected simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a diagram of the theoretical thickness of multiple plies;

[0026] FIG2 is a diagram illustrating multiple position identifications of a method for nondestructive testing and defect determination of back-drilled holes in a PCB according to an embodiment of the present application;

[0027] FIG3 is a schematic structural diagram of a PCB double-sided backdrill according to an embodiment of the present application;

[0028] FIG4 is a schematic structural diagram of a PCB before backdrilling according to an embodiment of the present application;

[0029] FIG5 is a schematic structural diagram of a qualified backdrill for a single-sided backdrill of a PCB according to an embodiment of the present application;

[0030] FIG6 is a schematic structural diagram of a single-sided backdrilling of a PCB according to an embodiment of the present application;

[0031] FIG7 is a schematic structural diagram of a PCB single-sided backdrilling with excessive backdrilling depth according to an embodiment of the present application;

[0032] FIG8 is a schematic structural diagram of a PCB single-sided backdrilling case where the backdrilling depth is too small according to an embodiment of the present application;

[0033] FIG9 is a flow chart of a nondestructive testing method for back-drilling quality of a PCB provided by the present application;

[0034] FIG10 is a flow chart of a method for determining a back-drilling defect of a PCB provided by the present application;

[0035] FIG11 is a schematic structural diagram of a PCB back-drilling quality non-destructive testing device provided by the present application;

[0036] FIG12 is a schematic structural diagram of a PCB back-drilling defect determination device provided by the present application;

[0037] FIG13 is a schematic structural diagram of an electronic device provided in this application. DETAILED DESCRIPTION

[0038] The embodiments of the present application will be described below with reference to the accompanying drawings. Although the drawings show optional embodiments of the present application, the present application can be implemented in many forms and should not be limited to the embodiments described herein.

[0039] The terms used in this application are for the purpose of describing particular embodiments only and are not intended to limit this application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term "and / or" refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0040] Although the terms "first", "second", "third", etc. may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise specified.

[0041] Example 1

[0042] This embodiment provides a nondestructive testing method for back-drilling quality of a PCB, as shown in FIG9 , including the following steps. This method can be applied to an automatic X-ray inspection machine.

[0043] S110: Acquire a cross-sectional image of the back-drilled hole to be tested using X-rays.

[0044] Detect the back-drilled hole to be detected using X-ray technology, reconstruct the grayscale value mutation position of the section of the back-drilled hole image to be detected, determine the residual pile tip of the residual pile copper column on the inner wall of the back-drilled hole, and record the tip L of the residual pile tip 尖端 location.

[0045] S120: On the cross-sectional image, the surface layer where the back-drilled hole is drilled is used as the reference layer. The theoretical depth of the target layer is calculated based on the layer of the target layer and the theoretical thickness of multiple layers between the target layer and the reference layer, thereby preliminarily locating the target layer. The target layer is the layer that cannot be drilled through.

[0046] S130: Based on the theoretical depth of the target layer, searching for a layer with a sudden grayscale value mutation according to the actual deviation range of the target layer, and determining the layer with a sudden grayscale value mutation as the actual target layer.

[0047] That is, determine the target layer and record the layer number where the target layer is located, determine the number of board layers between the target layer and the surface copper layer (i.e., the reference layer) and record the theoretical thickness of multiple board layers. The target layer and the reference layer may contain one or more board layers. Calculate the sum of the theoretical thicknesses of multiple board layers to obtain the theoretical distance between the target layer and the surface copper layer. For example, in order to more accurately determine the thickness of the target layer, the theoretical distance of the target layer * (1±0.08) is the middle position L of the actual target layer. m_ct .

[0048] For example, in conjunction with the table in FIG1 below, if the target layer is the 5th layer, the 1st to 4th layer and the corresponding thickness are 0.6, 2.86, 1.2, and 4 respectively, so the total thickness from the target layer of the 5th layer to the surface copper layer is calculated to be: 0.6+2.86+1.2+4=8.66, therefore, the theoretical distance between the target layer and the surface copper layer is 8.66, and the middle position L of the actual target layer is 0.6+2.86+1.2+4=8.66. m_ct Should be in the range of 8.66*(1±0.08).

[0049] S140: Identify the tip L of the stump tip on the cross-sectional image 尖端 , and measure the tip L of the stump tip 尖 端 The distance from the target layer to obtain the residual pile length L 残桩 .

[0050] In this embodiment, the measurement reference point of the actual target layer obtained in S130 is the middle position L of the actual target layer. m_ct , the actual target layer copper thickness Cu is measured Lm , length of residual pile L 残桩 =|L 尖端 -L m_ct |-0.5Cu Lm .

[0051] Formula L 残桩 =|L 尖端 -L m_ct |-0.5Cu Lm The working principle is: L 尖端 With L m_ct The difference is the stump length between the target layer and the stump tip, and the corresponding stump length is obtained by subtracting half the copper layer thickness.

[0052] In this embodiment, the middle position L of the actual target layer m_ct It is calculated by the theoretical depth of the target layer*(1±0.08), which can more accurately determine the thickness of the target layer.

[0053] In Figure 2, Cu Ln is the copper thickness of the drilled layer; Ln_ct is the middle position of the drilled layer; Cu bottom is the thickness of the bottom copper foil of the PCB; L bottom_ct This is the middle position of the actual bottom copper foil of the PCB detected by X-ray.

[0054] The present application provides a non-destructive testing method for PCB back-drilling quality, which uses X-rays to obtain a cross-sectional image of the back-drilled hole to be tested. Based on the cross-sectional image, the surface layer where the back-drilled hole is drilled is used as the reference layer. The theoretical depth of the target layer is calculated according to the layer of the target layer and the theoretical thickness of the multiple layers between the target layer and the reference layer, thereby preliminarily locating the target layer and identifying the tip L of the residual stump tip on the cross-sectional image. 尖端 , and measure the tip L of the stump tip 尖端 The distance from the target layer to obtain the residual pile length L 残桩 , where the multi-layer theoretical thickness is the theoretical thickness of the plate layer between the target layer and the reference layer. This non-destructive testing method can accurately detect and identify the target layer in combination with the laminated structure, and has the advantages of fast and convenient detection.

[0055] Example 2

[0056] Based on Example 1, this embodiment provides a method for determining back drilling defects in PCB. 孔深 (Back drilling depth) 、 Residual pile length L 残桩 (length of residual copper column) and the distance H from the actual target layer to the reference layer (surface copper layer) 目标层 ,Determining the defect of the back-drilled hole includes the following steps.

[0057] S210: Set the length of the residual pile L according to the processing requirements of the multi-layer printed circuit board 残桩 The maximum threshold A and the minimum threshold B.

[0058] S220: Determine the length of the residual pile L 残桩 Is it within (B, A).

[0059] Please refer to Figures 5 to 8. In order to determine whether the stump length (the length of the stump copper column) is qualified, this embodiment discloses setting the maximum threshold value of the stump length to A and the minimum threshold value to B. When B≤L 残桩 ≤A, the length of the residual pile is qualified; otherwise, the length of the residual pile is unqualified.

[0060] In one or more embodiments, when the stump length L 残桩 When the residual pile length L is greater than or equal to the minimum threshold B and less than or equal to the maximum threshold A, the residual pile length L 残桩 Within the appropriate range, the length of the residual pile can be determined to be qualified.

[0061] In one or more embodiments, if all L 残桩 <B, then the back drilling depth is too large. If all L 残桩 >A, it is determined that the back drilling depth is insufficient.

[0062] If the L on one side 残桩 >A, L on the other side残桩 <B, it is determined that there is a problem of drilling deviation in the back drilling.

[0063] S230: The distance between the tip of the residual pile and the reference layer is measured as the drilling depth D 孔深 , the distance H from the actual target layer to the reference layer is measured 目标层 , calculate the drilling depth threshold D 阈值 (H 目标层 -A,H 目标层 -B), then determine the drilling depth D 孔深 Is it in (H 目标层 -A,H 目标层 -B) inside.

[0064] Since the longer the residual copper column is, the smaller the back-drilling depth is, the drilling depth D is determined based on the set residual copper column length threshold. 孔深 Whether qualified.

[0065] If L 残桩 <B and D 孔深 >HA, the back drilling depth is too large. If L 残桩 >A and D 孔深 <HB, the back-drilling depth is too small. The back-drilling depth is determined by the two parameters of the residual copper column length and the back-drilling depth, avoiding the problem of inaccurate determination of whether the back-drilling is qualified by only one parameter.

[0066] S240:

[0067] If S220 L 残桩 Within (B, A), and the drilling depth in S230 is D 孔深 Also in (H 目标层 -A,H 目 标层 -B) is judged as qualified;

[0068] If S220 L 残桩 Not within (B, A), and the drilling depth in S230 is D 孔深 Nor in (H 目标层 -A,H 目标层 -B), it is judged as unqualified and according to L 残桩 Greater than A or less than B and D 孔深 Greater than H 目标层 -B or less than H 目标层 -A: The defect type is determined to be too deep or too shallow;

[0069] If S220 L 残桩 Within (B, A), and the drilling depth in S230 is D 孔深 Not in (H 目标层 -A,H 目标层-B), it is judged as unqualified, and the cause of the defect is the wrong positioning of the target layer or the wrong drilling surface;

[0070] If S220 L 残桩 Not within (B, A), and the drilling depth in S230 is D 孔深 In (H 目标层 -A,H 目标层 -B), it is judged as unqualified and the cause of the defect is drilling deviation.

[0071] Since the drilling depth D 孔深 , residual pile length L 残桩 And the distance H from the target layer to the reference layer (surface copper layer) 目标层 , so it is possible to judge whether the back drilling depth is too large or too small based on these values.

[0072] Please refer to FIG3 . In actual production, when the upper and lower surfaces of the PCB are back-drilled respectively, the back-drilled holes on the upper and lower surfaces of the PCB are inspected simultaneously, that is, the back-drilled holes on the upper and lower surfaces are inspected respectively.

[0073] The above method is based on three-dimensional X-ray non-destructive testing technology. By identifying and calculating different key data of back drilling holes, it automatically outputs different back drilling processing quality and defect results, solving the problem that non-destructive testing methods cannot detect and determine defects such as position drilling deviation, excessive back drilling depth, and insufficient back drilling depth, and outputs determination results for different defect determination methods.

[0074] The above detection method can achieve non-destructive testing accuracy within ±15μm.

[0075] In this embodiment, the thickness of the reference layer Cu is measured. top The measurement reference point of the obtained reference layer is the middle position L of the reference layer top_ct ; Drilling depth D 孔深 =|L top_ct -L 尖端 |+Cu top *0.5.

[0076] Point out the direction along the tip of the stump to identify the position with the maximum gray value of the whole layer and record the position, which is the middle position L of the reference layer in the direction of the back drilling surface of the circuit board. top_ct (Middle position of the top surface copper layer).

[0077] That is, the tip of the stump is pointing to the middle position of the top surface copper layer of the board layer, and the top position is the middle position L of the reference layer. top_ct .

[0078] In this embodiment, the measurement reference point of the actual target layer is the middle position L of the actual target layer.m_ct , the middle position of the reference layer L op_ct The middle position L of the actual target layer m_ct The actual distance from the target layer to the reference layer is obtained by adding half the thickness of the top surface copper layer and subtracting half the thickness of the target layer copper layer.

[0079] The measurement reference point of the actual target layer is measured to be the middle position L of the actual target layer. m_ct , the distance H from the actual target layer to the reference layer 目标层 =|L top_ct -L m_ct |+Cu top *0.5-Cu Lm *0.5, Cu Lm The copper thickness of the copper layer of the actual target layer.

[0080] Formula H 目标层 =|L top_ct -L m_ct |+Cu top *0.5-Cu Lm *0.5 principle: the middle position L of the reference layer top_ct (top position) and the middle position L of the actual target layer m_ct The distance between the target layer and the copper layer, plus the thickness of the top surface copper layer, minus the thickness of the copper layer of the target layer.

[0081] The PCB back drilling defect determination method of the present application is based on the obtained stump length L 残桩、 The distance between the tip of the residual pile and the reference layer is the drilling depth D 孔深 , D 孔深 By comparing the thresholds, it is possible to determine whether there are defects in the PCB back-drilled holes, and accurately determine the defect type and the defect type of the back-drilled holes.

[0082] FIG11 is a schematic structural diagram of a PCB back-drilling quality non-destructive testing device provided in an embodiment of the present application. As shown in FIG11 , the PCB back-drilling quality non-destructive testing device of this embodiment includes the following modules.

[0083] A cross-sectional image acquisition module 310 is configured to acquire a cross-sectional image of the back-drilled hole to be tested using X-rays;

[0084] The target layer positioning module 320 is configured to use the surface layer where the drilling surface of the back-drilled hole to be measured is located as a reference layer on the cross-sectional image, and calculate the theoretical depth of the target layer according to the layer of the target layer and the theoretical thickness of multiple layers between the target layer and the reference layer, thereby preliminarily locating the target layer;

[0085] The target layer determination module 330 is configured to use the theoretical depth of the target layer as a reference, search for a layer with a sudden grayscale value change according to the actual deviation range of the target layer, and determine the layer with a sudden grayscale value change as the actual target layer;

[0086] The stump length determination module 340 is configured to identify the tip L of the stump tip on the section image. 尖 端 , and measure the tip L of the stump tip 尖端 The distance between the target layer and the target layer is used to obtain the stump length Lstump.

[0087] In one or more embodiments, the measurement reference point of the actual target layer is the middle position L of the actual target layer. m_ct , the copper thickness of the actual target layer is measured Cu Lm , length of residual pile L 残桩 =|L 尖 端 -L m_ct |-0.5Cu Lm .

[0088] The above-mentioned PCB back-drilling quality non-destructive testing device can execute the PCB back-drilling quality non-destructive testing method provided in any embodiment of the present application, and has the corresponding functional modules and effects of the execution method.

[0089] FIG12 is a schematic structural diagram of a PCB back-drilling defect determination device provided in an embodiment of the present application. As shown in FIG12 , the PCB back-drilling defect determination device of this embodiment includes the following modules.

[0090] The threshold determination module 410 is configured to set the residual length L according to the processing requirements of the multi-layer printed circuit board. 残 桩 The maximum threshold A and the minimum threshold B;

[0091] The first judgment module 420 is configured to determine the length L of the residual pile 残桩 Is it within (B, A)?

[0092] The second judgment module 430 is configured to measure the distance between the tip of the residual pile tip and the reference layer as the drilling depth D 孔深 , the distance H from the actual target layer to the reference layer is measured 目标层 , calculate the drilling depth threshold D 阈值 (H 目标层 -A,H 目标层 -B), and determine the drilling depth D 孔深 Is it in (H 目标层 -A,H 目标层 -B) inside;

[0093] The determination module 440 is set to 残桩 Within (B, A) and drill depth D 孔深 Also in (H 目标层 -A,H 目标层 -B) In the case of the back drilling, it is determined to be qualified;

[0094] In L 残桩 Not within (B, A), and the drilling depth is D 孔深 Nor in (H 目标层 -A,H 目标层 -B) If the back drilling is not qualified, the back drilling is judged to be unqualified and the L 残桩 Greater than A or less than B and D 孔深 Greater than H 目标层 -B or less than H 目标层 -A: The defect type is determined to be too deep or too shallow;

[0095] In L 残桩 Within (B, A) and drill depth D 孔深 Not in (H 目标层 -A,H 目标层 -B) In the case of the back drilling, it is determined that the back drilling is unqualified and the cause of the defect is determined to be the wrong positioning of the target layer or the wrong drilling surface;

[0096] In L 残桩 Not within (B, A), and the drilling depth is D 孔深 In (H 目标层 -A,H 目标层 -B), the back drilling is judged to be unqualified and the cause of the defect is determined to be drilling deviation.

[0097] In one or more embodiments, the thickness of the reference layer Cu is measured. top The measurement reference point of the obtained reference layer is the middle position L of the reference layer. top_ct ; Drilling depth D 孔深 =|L top_ct -L 尖端 |+Cu top *0.5.

[0098] In one or more embodiments, the measurement reference point of the actual target layer is measured to be the middle position L of the actual target layer. m_ct , the distance H from the actual target layer to the reference layer 目标层 =|L top_ct -L m_ct |+Cu top *0.5-Cu Lm *0.5, Cu Lm The copper thickness of the copper layer of the actual target layer.

[0099] In one or more embodiments, when the upper surface and the lower surface of the PCB are back-drilled separately, the back-drilled holes of the upper surface and the lower surface of the PCB are inspected simultaneously.

[0100] The above-mentioned PCB back-drilling defect determination device can execute the PCB back-drilling defect determination method provided in any embodiment of the present application, and has functional modules and effects corresponding to the execution method.

[0101] Figure 13 is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. Referring to Figure 13 below, it shows a schematic diagram of the structure of an electronic device 500 suitable for implementing an embodiment of the present application. The electronic device in the embodiment of the present application may include mobile electronic devices such as mobile phones, laptops, digital broadcast receivers, personal digital assistants (PDAs), tablet computers (Portable Android Devices, PADs), portable multimedia players (PMPs), vehicle-mounted electronic devices (such as vehicle-mounted navigation electronic devices), etc., as well as fixed electronic devices such as digital televisions (TVs), desktop computers, etc. The electronic device shown in Figure 13 is only an example and should not bring any limitations to the functions and scope of use of the embodiments of the present application.

[0102] As shown in FIG13 , the electronic device 500 may include a processing device (e.g., a central processing unit, a graphics processing unit, etc.) 501. The processing device 501 may perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 502 or a program loaded from a storage device 508 into a random access memory (RAM) 503. Various programs and data required for the operation of the electronic device 500 are also stored in the RAM 503. The processing device 501, the ROM 502, and the RAM 503 are connected to each other via a bus 504. An input / output (I / O) interface 505 is also connected to the bus 504.

[0103] The following devices may be connected to the I / O interface 505: an input device 506 including, for example, a touch screen, a touchpad, a keyboard, a mouse, a camera, a microphone, an accelerometer, a gyroscope, etc.; an output device 507 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; a storage device 508 including, for example, a magnetic tape, a hard disk, etc.; and a communication device 509. The communication device 509 may allow the electronic device 500 to communicate with other devices wirelessly or by wire to exchange data. Although FIG13 shows an electronic device 500 having multiple devices, it is not required to implement or have all of the devices shown. More or fewer devices may be implemented or have alternatively.

[0104] According to an embodiment of the present application, the process described above with reference to the flowchart can be implemented as a computer software program. For example, an embodiment of the present application includes a computer program product, which includes a computer program carried on a non-transitory computer-readable medium, and the computer program includes a program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from the network through the communication device 509, or installed from the storage device 508, or installed from the ROM 502. When the computer program is executed by the processing device 501, the above-mentioned functions defined in the method of the embodiment of the present application are performed.

[0105] The electronic device provided in the embodiment of the present application and the non-destructive testing method for the back-drilling quality of a PCB or the method for determining the back-drilling defects of a PCB provided in the above-mentioned embodiment belong to the same application concept. For technical details not described in this embodiment, please refer to the above-mentioned embodiment, and this embodiment has the same effect as the above-mentioned embodiment.

[0106] An embodiment of the present application provides a computer storage medium having a computer program stored thereon. When the computer program is executed by a processor, the method for nondestructive detection of PCB back-drilling quality or the method for determining PCB back-drilling defects provided in the above-mentioned embodiment is implemented.

[0107] The computer-readable medium mentioned above in this application can be a computer-readable signal medium or a computer-readable storage medium, or any combination of the two. The computer-readable storage medium can be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or device, or any combination of the above. The computer-readable storage medium can include: an electrical connection with one or more wires, a portable computer disk, a hard disk, RAM, ROM, Erasable Programmable Read-Only Memory (EPROM), flash memory, optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In this application, a computer-readable storage medium can be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, device, or device. In this application, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, which carries computer-readable program code. This propagated data signal can take a variety of forms, including electromagnetic signals, optical signals, or any suitable combination of the above. A computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium that can send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium may be transmitted using any suitable medium, including: wires, optical cables, radio frequency (RF), etc., or any suitable combination thereof. The storage medium may be a non-transitory storage medium.

[0108] In some embodiments, the client and server can communicate using any currently known or future developed network protocol, such as the HyperText Transfer Protocol (HTTP), and can be interconnected with any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include local area networks (LANs), wide area networks (WANs), internets (e.g., the Internet), and peer-to-peer networks (e.g., ad hoc peer-to-peer networks), as well as any currently known or future developed networks.

[0109] The computer-readable medium may be included in the electronic device, or may exist independently without being incorporated into the electronic device.

[0110] The computer-readable medium carries one or more programs. When executed by the electronic device, the electronic device performs the nondestructive testing method for PCB back-drilled hole quality or the method for determining PCB back-drilled hole defects provided in any embodiment of the present application. Unless otherwise specified, the relative arrangement of components and steps, numerical expressions, and numerical values ​​described in these embodiments do not limit the scope of this application. Furthermore, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to scale. Techniques, methods, and devices known to persons of ordinary skill in the relevant art may not be discussed, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values. Similar reference numerals and letters represent similar items in the following figures; therefore, once an item is defined in one figure, it need not be discussed in subsequent figures.

[0111] In the description of this application, the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of this application; the directional words "inside and outside" refer to the inside and outside relative to the outlines of the multiple components themselves.

[0112] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be subsequently positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" may include both "above" and "below". The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used herein are interpreted accordingly.

[0113] In addition, the use of words such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above words have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

Claims

1. A non-destructive testing method for back drilling quality of a printed circuit board (PCB), comprising: Using X-rays to obtain a cross-sectional image of the back-drilled hole to be tested; On the cross-sectional image, the surface layer where the drilling surface of the back-drilled hole to be measured is located is used as the reference layer, and the theoretical depth of the target layer is calculated according to the layer type of the target layer and the theoretical thickness of multiple layers between the target layer and the reference layer, so as to preliminarily locate the target layer; Taking the theoretical depth of the target layer as a reference, searching for a layer with a sudden grayscale value change according to the actual deviation range of the target layer, and determining the layer with a sudden grayscale value change as the actual target layer; Identify the tip L of the stump tip on the slice image 尖端 , and measure the tip L of the stump tip 尖端 The distance between the actual target layer and the residual pile length L is obtained 残桩 .

2. The method according to claim 1, wherein: The measurement reference point of the actual target layer obtained is the middle position L of the actual target layer. m_ct , the copper thickness Cu of the actual target layer is measured Lm , the length of the residual pile is L 残桩 =|L 尖端 -L m_ct |-0.5Cu Lm .

3. The method according to claim 2, wherein: The middle position L of the actual target layer m_ct It is calculated by the theoretical depth*(1±0.08) of the target layer.

4. A method for determining back-drilling defects of a printed circuit board (PCB), in combination with the non-destructive testing method for back-drilling quality of a PCB according to any one of claims 1 to 3, comprising: According to the processing requirements of multi-layer printed circuit boards, set the length of the residual pile L 残桩 The maximum threshold A and the minimum threshold B; Determine the length L of the residual pile 残桩 Is it within (B, A)? Measure the tip L of the residual pile tip 尖端 The distance from the reference layer is the drilling depth D 孔深 , the distance H from the actual target layer to the reference layer is measured 目标层 , calculate the drilling depth threshold D 阈值 is (H 目标层 -A,H 目标层 -B), and determine the drilling depth D 孔深 Is it in (H 目标层 -A,H 目标层 -B) inside; In L 残桩 Within (B, A) and drilled to depth D 孔深 Also in (H 目标层 -A,H 目标层 -B) is within the range, the back drilling is judged to be qualified; In L 残桩 Not within (B, A), and the drilling depth is D 孔深 Nor in (H 目标层 -A,H 目标层 -B), the back drilling is judged as unqualified, and the L 残桩 Greater than A or less than B and D 孔深 Greater than H 目标层 -B or less than H 目标层 -A: The defect type is determined to be too deep or too shallow for back drilling; In L 残桩 Within (B, A) and drilled to depth D 孔深 Not in (H 目标层 -A,H 目标层 -B), the back drilling is judged to be unqualified, and the defect is caused by the wrong positioning of the target layer or the wrong drilling surface; In L 残桩 Not within (B, A), and the drilling depth is D 孔深 In (H 目标层 -A,H 目标层 -B), the back drilling is judged to be unqualified and the defect is caused by drilling deviation.

5. The method according to claim 4, wherein: The thickness of the reference layer Cu is measured top The measurement reference point of the obtained reference layer is the middle position L of the reference layer. top_ct ; Drilling depth D 孔深 =|L top_ct -L 尖端 |+Cu top *0.

5.

6. The method according to claim 5, wherein: The measurement reference point of the actual target layer is measured to be the middle position L of the actual target layer. m_ct , the distance H from the actual target layer to the reference layer 目标 层 =|L top_ct -L m_ct |+Cu top *0.5-Cu Lm *0.5,Cu Lm The copper thickness of the copper layer of the actual target layer.

7. The method according to claim 4, wherein: In the case where the upper surface and the lower surface of the PCB are back-drilled respectively, the back-drilled holes of the PCB on the upper surface and the lower surface are detected at the same time.

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