PCB defect correction method and circuit board manufacturing method

Abstract

The application discloses a PCB defect correction method and a circuit board manufacturing method. The correction method comprises the following steps: inputting the design document of the circuit board to be detected into an AOI device, wherein the design document comprises the size design information of each object on the circuit board; scanning the circuit board by using the AOI device to obtain a scanning image, and acquiring the pixel unit size currently set by the AOI device; in response to a detection request for a target object on the circuit board, determining the number of pixels occupied by the target object in the scanning image in a requested measurement direction; calculating the size of the target object in the requested measurement direction according to the current pixel unit size of the AOI device and the number of pixels occupied by the target object; comparing the size of the target object in the requested measurement direction with the size of the target object in the design document; if the size difference exceeds a preset difference threshold, it is determined that the target object has a defect, and the process type of the target object is determined and the process parameter of the target object is corrected according to the design document.

Description

[0001] This application is a divisional application of the invention application filed on June 20, 2022, with application number 2022106966763 and titled "PCB Defect Detection Method, Circuit Board Measurement Method and Manufacturing Method". Technical Field

[0002] This invention relates to the field of PCB inspection, and more particularly to a method for PCB defect correction and a method for circuit board manufacturing. Background Technology

[0003] Automated Optical Inspection (AOI) equipment has become an important inspection tool and process quality control tool for ensuring product quality in the electronics manufacturing industry. It is equipped with a line scan camera to scan the circuit board and then stitch the sub-images of the line scan to obtain a complete PCB scan image.

[0004] The conventional method for PCB defect detection is to use AOI equipment to compare the detection points with qualified parameters in a database, and then process the images to detect defects on the product being tested.

[0005] However, the accuracy of current AI detection models is insufficient, leading to frequent detection errors and affecting the accuracy of defect identification.

[0006] The above background information is provided only to assist in understanding the inventive concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application, nor does it necessarily provide technical teaching. In the absence of clear evidence that the above information was disclosed before the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0007] The purpose of this invention is to provide a method for first detecting defects in a PCB and then correcting the process parameters of the defective object. This method utilizes the scanning images from an AOI device to quickly perform two-dimensional measurement on the object on the PCB, and uses the PCB measurement data as the basis for detecting PCB defects, thereby improving the accuracy of defect detection and identification.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A PCB defect correction method includes:

[0010] Input the PCB design document of the circuit board to be inspected into the AOI device. The PCB design document includes the dimensional design information of each object on the circuit board.

[0011] The AOI device is used to scan the circuit board to be inspected to obtain a PCB scan image, and the pixel unit size currently set by the AOI device is obtained.

[0012] In response to a trigger signal requesting the detection of at least one target object, the number of pixels occupied by the target object in the PCB scan image in the requested measurement direction is determined;

[0013] Based on the pixel unit size currently set by the AOI device and the number of pixels occupied by the target object in the requested measurement direction, the size of the target object in the requested measurement direction is calculated by multiplying the two.

[0014] The calculated dimensions of the target object in the requested measurement direction are compared with the dimension design information of the target object in the PCB design document. If the dimension difference exceeds a preset difference threshold, it is determined that the target object of the circuit board has a defect. Based on the PCB design document, the process type of the target object is determined, and the process parameters are corrected for the determined process type so that the dimension difference between the measurement dimension of the target object of the circuit board manufactured by the corrected process and its dimension design information in the PCB design document is reduced.

[0015] Furthermore, if the measured line width of the solder wire on the circuit board to be inspected is smaller than the corresponding size design information, the etching time process parameters are reduced.

[0016] If the measured line width of the solder wires on the circuit board to be inspected is larger than the corresponding size design information, then increase the etching time process parameters.

[0017] Furthermore, the trigger signal for a detection request of a target object includes:

[0018] The PCB scan image and the corresponding PCB design image from the PCB design document are pre-entered into the two-dimensional measurement software for display.

[0019] Map and associate the PCB scan image with the PCB design image;

[0020] On the display interface of the PCB scan image, select the target object and determine the measurement direction; and determine the mapping object associated with the selected target object in the PCB design image.

[0021] Furthermore, the trigger signal for a detection request of a target object includes:

[0022] The PCB scan image and the corresponding PCB design image from the PCB design document are pre-entered into the two-dimensional measurement software for display.

[0023] Map and associate the PCB scan image with the PCB design image;

[0024] On the display interface of the PCB design image, select the mapping object associated with the target object mapping; determine the target object associated with the selected mapping object in the PCB scan image, and determine the measurement direction.

[0025] Furthermore, in response to a trigger signal for a detection request for a defined area, all target objects within the defined area are located and their respective measurement directions are determined, and the number of pixels occupied by each target object in the PCB scan image in its respective measurement direction is determined.

[0026] Based on the currently set pixel unit size and the number of pixels occupied by each target object within the defined area, calculate the size of each target object in the requested measurement direction.

[0027] Furthermore, the target object is a straight line segment or a curved line segment, and the corresponding requested measurement direction is the direction of line segment length extension or line width direction; or,

[0028] The target object is a polygon, and the corresponding requested measurement direction is the edge length direction.

[0029] Alternatively, the target object is circular, and its corresponding requested measurement direction is radial.

[0030] Furthermore, the PCB scan image is a grayscale image or a color image.

[0031] Furthermore, during the AOI equipment scanning process, the number of pixels occupied by each scanned object on the circuit board in the PCB scan image in the requested measurement direction is counted until the scanning is completed. At this point, the number of pixels occupied by all objects on the circuit board in the PCB scan image in the requested measurement direction and / or the size of all objects in the requested measurement direction are obtained.

[0032] Furthermore, the number of pixels occupied by each scanned object on the circuit board in the PCB scan image in the requested measurement direction is counted in the following manner:

[0033] Locate the starting endpoint of the target object in its measurement direction and count it as 1;

[0034] If the grayscale value difference between the current pixel block and the pixel block in the previous step exceeds a preset grayscale threshold, the counting and stepping will stop; otherwise, the count will increment by 1.

[0035] Repeat the step to the next pixel block in the measurement direction until the difference in grayscale value between the current pixel block and the pixel block in the previous step exceeds a preset grayscale threshold. Then, use the current counting result as the number of pixels occupied by the target object in the PCB scan image in its measurement direction.

[0036] According to another aspect of the present invention, a 2D measurement method for printed circuit boards is provided, comprising:

[0037] Acquire a PCB scan image obtained by an AOI device scanning a target circuit board, and acquire the currently set pixel unit size of the AOI device;

[0038] Select one or more target objects in the PCB scan image and determine their measurement direction;

[0039] Determine the number of pixels occupied by the target object in its respective measurement direction in the PCB scan image; calculate the size of the target object in its measurement direction based on the pixel unit size currently set by the AOI device and the number of pixels occupied by the target object.

[0040] Furthermore, the number of pixels occupied by a target object in its measurement direction in the PCB scan image is determined by the following method:

[0041] Locate the starting endpoint of the target object in its measurement direction and count it as 1;

[0042] If the grayscale value difference between the current pixel block and the pixel block in the previous step exceeds a preset grayscale threshold, the counting and stepping will stop; otherwise, the count will increment by 1.

[0043] Repeat the step to the next pixel block in the measurement direction until the difference in grayscale value between the current pixel block and the pixel block in the previous step exceeds a preset grayscale threshold. Then, use the current counting result as the number of pixels occupied by the target object in the PCB scan image in its measurement direction.

[0044] Furthermore, the printed circuit board 2D measurement method also includes:

[0045] The PCB scan image is mapped and associated with the PCB design image in the design document of the target circuit board;

[0046] Determine the mapping object associated with the selected target object in the PCB design image;

[0047] Determine the dimensional design information of the mapped object in the design document;

[0048] The difference between the calculated dimension of the target object in its measurement direction and the dimension design information of the mapped object in the design document is used as the measurement result of the target object.

[0049] According to another aspect of the present invention, a method for manufacturing a printed circuit board is provided, comprising:

[0050] Set various initial process parameters according to the circuit board design document;

[0051] The circuit board to be verified was fabricated according to the initial process parameters.

[0052] The PCB defect correction method described above is used to correct the defects in the circuit board.

[0053] If it is determined that the circuit board is free of defects, then mass production shall be carried out according to the current process parameters.

[0054] The beneficial effects of the technical solution provided by this invention are as follows:

[0055] a. Two-dimensional metrological measurements of circuit boards can be performed on the scanned images of circuit boards by AOI equipment without the need for additional tools such as cameras;

[0056] b. During the AOI equipment scanning process, the number of pixels occupied by the target object in the PCB scan image in the requested measurement direction can be counted. After the AOI equipment scan is completed, the two-dimensional measurement result data of the circuit board can be obtained quickly without affecting the AOI detection process itself, which greatly improves the efficiency of the AOI cycle.

[0057] c. The scanned image of the AOI device is stitched together from the images captured by the line scan camera, so that compared with the limited pixels of the camera, the scanned image theoretically has an unlimited number of measurement points. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0059] Figure 1 A schematic flowchart of a PCB defect detection and correction method based on 2D metrology provided as an exemplary embodiment of the present invention;

[0060] Figure 2 A schematic diagram of a 2D metrology measurement method for printed circuit boards provided as an exemplary embodiment of the present invention;

[0061] Figure 3 A schematic diagram of the measurement interface of a two-dimensional measurement software provided as an exemplary embodiment of the present invention;

[0062] Figure 4 A schematic diagram of a printed circuit board manufacturing method based on 2D measurement, provided as an exemplary embodiment of the present invention. Detailed Implementation

[0063] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0064] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, apparatus, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0065] In one embodiment of the present invention, a PCB defect detection method is provided, see [link to relevant documentation]. Figure 1 The defect detection method includes:

[0066] Input the PCB design document of the circuit board to be inspected into the AOI device. The PCB design document includes the dimensional design information of each object on the circuit board.

[0067] The AOI device is used to scan the circuit board to be inspected to obtain a PCB scan image (which can be a grayscale image or a color image), and the pixel unit size currently set by the AOI device is obtained.

[0068] In response to a trigger signal requesting the detection of at least one target object, the number of pixels occupied by the target object in the PCB scan image in the requested measurement direction is determined;

[0069] Based on the currently set pixel unit size of the AOI device and the number of pixels occupied by the target object, calculate the size of the target object in the requested measurement direction;

[0070] If the calculated dimensions of the target object in the requested measurement direction are compared with the dimension design information of the target object in the PCB design document, and the dimension difference exceeds a preset difference threshold, then it is determined that the target object of the circuit board has a defect.

[0071] In this embodiment, the PCB scan image and the corresponding PCB design image from the PCB design document are pre-entered into two-dimensional metrology software for display, such as... Figure 3 As shown, Figure 3 The top center shows the PCB design image, and the bottom center shows the PCB scan image.

[0072] In the two-dimensional measurement software, the PCB scan image is mapped and associated with the PCB design image. That is, if an object is selected in the PCB scan image, it can be mapped to the corresponding object in the PCB design image, and vice versa.

[0073] In one embodiment of the present invention, the trigger signal for a detection request of a target object is: selecting the target object on the display interface of the PCB scan image and determining the measurement direction; and determining the mapping object associated with the selected target object in the PCB design image.

[0074] In another embodiment of the present invention, the trigger signal for the detection request of a target object is: selecting a mapping object associated with the target object mapping on the display interface of the PCB design image; determining the target object associated with the selected mapping object in the PCB scan image; and determining the measurement direction.

[0075] In summary, the target object can be a line segment, a circular area, or a polygonal area in the PCB scan image. For example, a target object can be selected by clicking, clicking multiple times, or right-clicking, or the target object in the PCB scan image can be selected indirectly by selecting the mapped object in the PCB design image.

[0076] Different target objects can have different measurement directions. For example, if the target object is a straight line segment or a curved line segment, the corresponding requested measurement direction is the direction of line segment length extension or line width; if the target object is a polygon, the corresponding requested measurement direction is the direction of edge length; if the target object is a circle, the corresponding requested measurement direction is the radial direction.

[0077] like Figure 3As shown, the selected target object is a straight line segment, and the requested measurement direction is the line width direction. Figure 3 The Measurement pop-up window shows that the 2D measurement linewidth in the PCB scan image is 3.59µm, corresponding to a 4.6µm dimension design information (Reference) of the associated mapped object in the PCB design image, resulting in a dimension difference of -1.01µm. For example, a preset difference threshold of 0.5µm indicates that a range of ±0.5µm from the Reference dimension is within the tolerance range. If the difference exceeds this range, the process parameters of the target object need to be corrected to reduce the dimension difference between the measured dimension of the target object on the PCB manufactured using the corrected process and its dimension design information in the PCB design document. Figure 3 In this process, the line segment is etched. If the 2D measured line width is smaller than the Reference size, it indicates that the etching is over-etched and the etching time process parameter should be reduced. Conversely, if the 2D measured line width is larger than the Reference size, it indicates that the etching is incomplete and the etching time process parameter should be increased.

[0078] In one embodiment of the present invention, multiple target objects can also be measured in batches in two dimensions. The specific steps are as follows: using an input device such as a mouse to delineate an area in a PCB scan image, and similarly associating it with a mapped area in a PCB design image to locate all target objects within the delineated area and determine their respective measurement directions; determining the number of pixels occupied by each target object in its respective measurement direction in the PCB scan image; and calculating the size of each target object in the requested measurement direction based on the currently set pixel unit size and the number of pixels occupied by each target object within the delineated area.

[0079] Alternatively, an area can be defined in the PCB design image to locate all design objects within that area. These objects can then be mapped to the PCB scan image to obtain target objects associated with each design object. By using the measurement method for a single target object, multiple target objects can be measured one by one and compared with the design (Reference) dimensions in batches, which can effectively improve defect detection efficiency.

[0080] Even more remarkably, in one particular embodiment, during the AOI scanning process, a step of counting the number of pixels of each object on the PCB in each measurement direction is automatically performed. This allows the two-dimensional measurement result data of all objects on the PCB (in their respective measurement directions) to be obtained immediately after the AOI device completes the scan.

[0081] Specifically, the number of pixels occupied by each scanned object on the circuit board in the PCB scan image along the requested measurement direction is counted using the following method:

[0082] Locate the starting endpoint of the target object in its measurement direction and count it as 1;

[0083] If the grayscale value difference between the current pixel block and the pixel block in the previous step exceeds a preset grayscale threshold, the counting and stepping will stop; otherwise, the count will increment by 1.

[0084] Repeat the step to the next pixel block in the measurement direction until the difference in grayscale value between the current pixel block and the pixel block in the previous step exceeds a preset grayscale threshold. Then, use the current counting result as the number of pixels occupied by the target object in the PCB scan image in its measurement direction.

[0085] In one embodiment of the present invention, a 2D measurement method for printed circuit boards is provided, such as... Figure 2 As shown, the measurement methods include:

[0086] Acquire a PCB scan image obtained by an AOI device scanning a target circuit board, and acquire the currently set pixel unit size of the AOI device;

[0087] Select one or more target objects in the PCB scan image and determine their measurement direction;

[0088] Determine the number of pixels occupied by the target object in its respective measurement direction in the PCB scan image; calculate the size of the target object in its measurement direction based on the pixel unit size currently set by the AOI device and the number of pixels occupied by the target object.

[0089] One aspect of this invention involves using an AOI (Automated Optical Inspection) line scan camera to scan a PCB circuit board, then stitching the scanned images together to obtain a complete PCB scan image. The scan resolution provided by the AOI device can be converted into a single pixel size, or the AOI device can directly provide a single pixel size for direct two-dimensional measurement within the PCB scan image. Specifically, the number of pixels "passed through" by the target object in the measurement direction, multiplied by the side length of a single pixel, gives the length of the target object in the measurement direction. In this embodiment, the number of pixels occupied by a target object in its measurement direction within the PCB scan image is determined using the following method:

[0090] Locate the starting endpoint of the target object in its measurement direction and count it as 1;

[0091] If the grayscale value difference between the current pixel block and the pixel block in the previous step exceeds a preset grayscale threshold, the counting and stepping will stop; otherwise, the count will increment by 1.

[0092] Repeat the step to the next pixel block in the measurement direction until the difference in grayscale value between the current pixel block and the pixel block in the previous step exceeds a preset grayscale threshold. Then, use the current counting result as the number of pixels occupied by the target object in the PCB scan image in its measurement direction.

[0093] The 2D measurement method for printed circuit boards in this embodiment also includes:

[0094] The PCB scan image is mapped and associated with the PCB design image in the design document of the target circuit board;

[0095] Determine the mapping object associated with the selected target object in the PCB design image;

[0096] Determine the dimensional design information of the mapped object in the design document;

[0097] The difference between the calculated dimension of the target object in its measurement direction and the dimension design information of the mapped object in the design document is used as the measurement result of the target object.

[0098] This embodiment of the 2D metrology method for printed circuit boards and the above-mentioned PCB defect detection method embodiment are based on the same inventive concept. Here, the 2D metrology method embodiment for printed circuit boards and the PCB defect detection method embodiment are combined in a combined manner.

[0099] In one embodiment of the present invention, a method for manufacturing a printed circuit board is provided, such as... Figure 4 As shown, the manufacturing method includes:

[0100] Set various initial process parameters according to the circuit board design document;

[0101] The circuit board to be verified was fabricated according to the initial process parameters.

[0102] The circuit board is inspected using the method described in the above PCB defect detection method embodiment;

[0103] If it is determined that the circuit board is free of defects, then mass production shall be carried out according to the current process parameters;

[0104] Otherwise, based on the PCB design document, determine the process type of the defective object; modify the process parameters for the determined process type so that the difference between the measured dimensions of the target object of the circuit board manufactured by the modified process and its dimension design information in the design document is reduced.

[0105] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0106] The above description is only a specific embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for correcting PCB defects, characterized in that, A method for correcting etching process parameters based on the linewidth detection results of solder lines on a circuit board, the correction method comprising: Input the PCB design document of the circuit board to be inspected into the AOI device. The PCB design document includes the PCB design image and the size design information of each object on the circuit board. An AOI device is used to scan the circuit board to be inspected to obtain a PCB scan image, and the pixel unit size currently set by the AOI device is obtained; during the scanning process of the AOI device, the number of pixels occupied by the object on the circuit board in the PCB scan image in the preset requested measurement direction is counted. In response to a trigger signal for a detection request for at least one target object, the number of pixels occupied by the target object in the PCB scan image along the requested measurement direction is determined; wherein the trigger signal for the detection request for at least one target object includes either of the following two methods: inputting the PCB scan image and the corresponding PCB design image from the PCB design document into two-dimensional measurement software for display in advance; mapping and associating the PCB scan image with the PCB design image; selecting the target object on the display interface of the PCB scan image and determining the measurement direction; and determining the mapping object associated with the selected target object in the PCB design image; or, inputting the PCB scan image and the corresponding PCB design image from the PCB design document into two-dimensional measurement software for display in advance; mapping and associating the PCB scan image with the PCB design image; selecting the mapping object associated with the target object on the display interface of the PCB design image; and determining the target object associated with the selected mapping object in the PCB scan image and determining the measurement direction. Based on the pixel unit size currently set by the AOI device and the number of pixels occupied by the target object in the requested measurement direction, the size of the target object in the requested measurement direction is calculated by multiplying the two. The calculated dimensions of the target object in the requested measurement direction are compared with the dimension design information of the target object in the PCB design document. If the dimension difference exceeds a preset difference threshold, it is determined that the target object on the circuit board has a defect. Based on the PCB design document, the process type of the target object is determined, and the process parameters are corrected for the determined process type to reduce the dimension difference between the measured dimensions of the target object on the circuit board manufactured by the corrected process and its dimension design information in the PCB design document. If the measured dimension of the line width of the solder wire on the circuit board to be inspected is smaller than the corresponding dimension design information, the etching time process parameters are reduced; if the measured dimension of the line width of the solder wire on the circuit board to be inspected is larger than the corresponding dimension design information, the etching time process parameters are increased.

2. The PCB defect correction method according to claim 1, characterized in that, In response to a trigger signal requesting the detection of a defined area, all target objects within the defined area are located and their respective measurement directions are determined, and the number of pixels occupied by each target object in the PCB scan image in its respective measurement direction is determined. Based on the currently set pixel unit size and the number of pixels occupied by each target object within the defined area, calculate the size of each target object in the requested measurement direction.

3. The PCB defect correction method according to claim 1, characterized in that, The target object is a straight line segment or a curved line segment, and the corresponding requested measurement direction is the direction of line segment length extension or line width; or... The target object is a polygon, and the corresponding requested measurement direction is the direction of the edge length; or... The target object is circular, and its corresponding measurement direction is radial.

4. The PCB defect correction method according to claim 1, characterized in that, The PCB scan image is either a grayscale image or a color image.

5. The PCB defect correction method according to any one of claims 1 to 4, characterized in that, During the AOI scanning process, the number of pixels occupied by each scanned object on the circuit board in the PCB scan image in the requested measurement direction is counted until the scanning is completed. At this point, the number of pixels occupied by all objects on the circuit board in the PCB scan image in the requested measurement direction and / or the size of all objects in the requested measurement direction are obtained.

6. The PCB defect correction method according to claim 5, characterized in that, The number of pixels occupied by each scanned object on the circuit board in the PCB scan image in the requested measurement direction is counted using the following method: Locate the starting endpoint of the target object in its measurement direction and count it as 1; If the grayscale value difference between the current pixel block and the pixel block in the previous step exceeds a preset grayscale threshold, the counting and stepping will stop; otherwise, the count will increment by 1. Repeat the step to the next pixel block in the measurement direction until the difference in grayscale value between the current pixel block and the pixel block in the previous step exceeds a preset grayscale threshold. Then, use the current counting result as the number of pixels occupied by the target object in the PCB scan image in its measurement direction.

7. A method for manufacturing a printed circuit board, characterized in that, include: Set various initial process parameters according to the circuit board design document; The circuit board to be verified was fabricated according to the initial process parameters. The PCB defect correction method as described in any one of claims 1 to 6 is used to correct the defects in the PCB. If it is determined that the circuit board is free of defects, then mass production shall be carried out according to the current process parameters.

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