A method for detecting variable solder joints and gold wires in chip detection, computer readable medium

Abstract

The application discloses a detection method and computer readable medium for variable solder joints and gold wires in chip detection, which utilizes image threshold segmentation to obtain a possible solder joint area, and then utilizes an opening operation to remove noise interference, extracts a solder joint contour for first solder joint positioning, according to the result of the first solder joint positioning, expands the detection area, and utilizes a caliper method to extract an accurate position of the solder joint, which utilizes contour extraction for coarse positioning to obtain the position of the solder joint, avoiding the problem that the traditional method directly uses the caliper to extract the variable solder joint and fails; a template matching method is utilized to position a second solder joint, and the second solder joint is segmented according to the size of the drawn template; the positions of the first solder joint and the second solder joint are sorted, and the sorting result is matched according to rows or columns, the first solder joint and the second solder joint are connected to obtain a gold wire, a detection area of the gold wire is calculated according to a set expansion range, and gold wire detection is performed through threshold segmentation.

Description

Technical Field

[0001] This invention relates to the field of variable solder joint product testing technology, and in particular to a method for detecting variable solder joints and gold wires in chip testing. Background Technology

[0002] As the integrated circuit industry continues to advance towards advanced processes, chip integration density is constantly increasing, and packaging technology is also continuously improving. In the semiconductor packaging process, the chip, as a core electronic component, directly affects the reliability of electronic devices. Wire bonding (WB) is a key process in chip packaging, connecting the chip's electrodes to the packaging substrate or lead frame via metal wires to ensure stable transmission of electrical signals. The quality of WB products directly affects the reliability of the chip's electrical connections. Defects such as poor bonding, broken wires, short circuits, and misalignment can lead to chip malfunction and even affect the stability of the entire device.

[0003] Currently, quality inspection of traditional WB products mainly relies on manual visual inspection and electrical performance testing. Manual visual inspection is inefficient and depends on operator experience, and is easily affected by subjective factors, making it difficult to meet the needs of high-precision, high-volume production. Electrical performance testing can only test electrical continuity and cannot detect problems such as solder joint misalignment and gold wire abnormalities in advance, resulting in high rework and maintenance costs later.

[0004] Currently, many WB products have inconsistent solder joint positions. Due to these differences, the gold wire positions may shift. Furthermore, these products typically have a large number of solder joints and gold wires, which are densely arranged, making it easier to miss or misdetect them when relying on traditional manual inspection methods. Summary of the Invention

[0005] According to a first aspect of the present invention, a method for detecting variable solder joints and gold wires in chip inspection is provided, comprising the following steps:

[0006] Solder joint inspection:

[0007] Thresholding is performed on the acquired chip image to extract candidate solder joint regions that meet the grayscale range, resulting in a solder joint threshold image.

[0008] Morphological opening operations are used to remove noise from a threshold image of a solder joint. After noise removal, the boundary contour point set of the solder joint region is obtained. ;

[0009] Calculate the shortest distance from each point inside the boundary profile of each weld point to the boundary profile of the weld point. Obtain the distance image and find the point with the maximum value in the distance image. ,but The distance from the center of the inscribed circle of this weld joint to the point of maximum value. The radius of the inscribed circle of the weld joint;

[0010] Using the center of the inscribed circle as the center and a preset multiple of the radius of the inscribed circle as the search area, a solder joint is extracted using the caliper method to obtain the precise center position and radius of the solder joint;

[0011] Determine whether there are missing solder joints, poor solder ball quality, or residual solder ball defects based on the number and area of ​​a solder joint and the area of ​​defects in the outer expansion region.

[0012] Two-weld joint inspection:

[0013] Multiple two-solder-point templates are drawn, and the positions of all two-solder-points are located in the chip image by normalized cross-correlation matching;

[0014] Calculate the minimum bounding rectangle of each template's two weld points to obtain the standard width and height. Based on the positions of all the located two weld points and their standard width and height, crop each two weld point individually to obtain an independent image of the two weld points.

[0015] Determine whether there are missing, poor, or redundant solder joints based on the number and area of ​​the two solder joints.

[0016] Gold thread testing:

[0017] Based on the data of the first and second solder joints obtained from the detection of the first and second solder joints, the first and second solder joints are sorted. Then, according to the sorting results, they are paired by row or column to match the first and second solder joints one by one. The paired first and second solder joints are connected to calculate the theoretical angle, midpoint and length of the gold wire.

[0018] Based on theoretical angles, lengths, and user-defined expansion parameters, a rectangular detection area for the gold wire is adaptively generated. Threshold segmentation is performed within the rectangular detection area, and the gold wire is judged to have broken or bent defects based on its connectivity and whether it exceeds the detection area.

[0019] Furthermore, in the detection of a single solder joint, the formula for threshold processing is:

[0020] ;

[0021] in, This represents the grayscale value of the chip image at coordinates (x, y); It is the lower limit of the grayscale value of the solder joint; It is the upper limit of the grayscale value of the solder joint.

[0022] Furthermore, the operational formula for morphological opening is:

[0023] ;

[0024] in, The image to be processed; This is a structure element for opening operations.

[0025] Furthermore, calculate the shortest distance from each point inside the boundary profile of each weld point to the boundary profile of the weld point. The formula is:

[0026] .

[0027] Furthermore, the formula for locating all two-solder joint positions in the chip image using normalized cross-correlation matching is as follows:

[0028] ;

[0029] in, Template image; The mean of the template image; Image of the chip to be inspected; The average value of the image in the chip image; It is the pixel coordinate position; It is a template image in a chip image. The sliding position.

[0030] Furthermore, the formula for calculating the minimum bounding rectangle of each template's two weld points to obtain the standard width and height is as follows:

[0031] ;

[0032] in, It is the average width; It is the average height; The number of template images, .

[0033] Furthermore, from the theoretical perspective of gold lines Calculated using the following formula:

[0034] ;

[0035] in, These are the coordinates of a solder joint on the gold wire. These are the coordinates of the two solder points of the gold wire.

[0036] Furthermore, the midpoint of the gold line The length d is calculated using the following formula:

[0037] .

[0038] Furthermore, the rectangular detection area for generating the gold line is specifically as follows:

[0039] The formula for calculating the coordinates of the top right corner vertex of the rectangular detection area for the gold line is as follows:

[0040] ;

[0041] The formula for calculating the coordinates of the top-left vertex of the rectangular detection area for the gold line is as follows:

[0042] ;

[0043] The formula for calculating the coordinates of the lower left corner vertex of the rectangular detection area for the gold line is as follows:

[0044] ;

[0045] The formula for calculating the coordinates of the lower right corner vertex of the rectangular detection area for the gold line is as follows:

[0046] ;

[0047] in, The parameters for expanding the gold line area are set in a custom way;

[0048] A rectangular detection area for the gold line is generated based on the calculated coordinates of the four vertices.

[0049] According to a second aspect of the present invention, a computer-readable medium having processor-executable non-volatile program code is provided, the program code causing the processor to perform a method for detecting variable solder joints and gold wires in chip inspection according to a first aspect.

[0050] A method for detecting variations in solder joints and gold wires in chip testing according to an embodiment of the present invention has the following beneficial effects:

[0051] 1. A detection method is proposed for chips with solder joint changes, which detects the first and second solder joints that have changed, and detects the corresponding gold wires based on the changed solder joints;

[0052] 2. For the inspection of a single solder joint, the position of the solder joint is obtained by two positioning operations, which avoids the problem of solder joint positioning failure caused by the change of the solder joint position when the inspection is performed directly at a fixed position.

[0053] 3. Based on the drawn two-weld-point template, the two-weld-point region is obtained by threshold segmentation. The standard width and height of the two-weld-point region are obtained by finding the minimum bounding rectangle of the two-weld-point region. The two-weld-point is then separated using the standard width and height.

[0054] 4. Pair the first and second solder joints, and adaptively generate the detection area based on the pairing results and the gold wire expansion parameters set by the user. Obtain the gold wire area through threshold segmentation, and determine the gold wire defect type based on the obtained gold wire area and the detection area.

[0055] It should be understood that both the foregoing general description and the following detailed description are exemplary and intended to provide further illustration of the claimed technology. Attached Figure Description

[0056] Figure 1 This is a flowchart of a chip testing method for detecting variable solder joints and gold wires according to an embodiment of the present invention.

[0057] Figure 2 This is a schematic diagram showing the adhesion of two weld points.

[0058] Figure 3 This is a schematic diagram of the rectangular detection area of ​​gold wire generated by a chip inspection method for detecting variable solder joints and gold wires according to an embodiment of the present invention. Detailed Implementation

[0059] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, further illustrating the present invention.

[0060] First, combine Figure 1 , 3 This invention describes a method for detecting variable solder joints and gold wires in chip testing, which is widely used for detecting solder joints and gold wires.

[0061] like Figure 1 , 3 As shown, an embodiment of the present invention provides a method for detecting variable solder joints and gold wires in chip testing, comprising the following steps:

[0062] In S1, a solder joint inspection includes the following sub-steps:

[0063] S101: Perform thresholding on the acquired chip image to extract candidate solder joint regions that meet the grayscale range, resulting in a solder joint threshold image. The thresholding formula is:

[0064] (1);

[0065] in, This represents the grayscale value of the chip image at coordinates (x, y); It is the lower limit of the grayscale value of the solder joint; It is the upper limit of the grayscale value of the solder joint.

[0066] S102: Use morphological opening operations to remove noise interference from a weld joint threshold image. After noise removal, obtain the boundary contour point set of the weld joint region. The operational formula for the morphological opening operation is as follows:

[0067] (2);

[0068] in, The image to be processed; This is a structure element for opening operations.

[0069] S103: Calculate the shortest distance from each point inside the boundary profile of each weld point to the boundary profile of the weld point. Obtain a distance image and find the point with the maximum value in the distance image. ,but The distance from the center of the inscribed circle of this weld joint to the point of maximum value. The radius of the inscribed circle of a given weld joint is used as the coarse positioning result for the weld joint. The shortest distance from each point inside the boundary profile of each weld joint to the weld joint boundary profile is calculated. The formula is:

[0070] (3).

[0071] S104: Using the center of the inscribed circle as the center, and a preset multiple of the radius of the inscribed circle (in this embodiment, the multiple is 2 times) as the search area, a solder joint is extracted using the caliper method to obtain the precise center position and radius of the solder joint.

[0072] S105: Determine whether a solder joint is missing, a solder ball defect is poor, or a solder ball residue defect is based on the number of solder joints, their area, and the defect area of ​​the extended area. It should be noted that: if the number of solder joints located is different from the required number, it is determined to be a missing solder joint; if the number of solder joints is correct, each solder joint is divided into thresholds according to formula (1), and the area after division is calculated. If the area is not within the set threshold range, it is determined to be a solder ball defect; for each solder joint area, the area is extended outward. If the defect area within the extended area is greater than the set threshold, it is determined to be a solder ball residue.

[0073] In S2, the two-solder joint detection includes the following sub-steps:

[0074] S201: Draw multiple two-solder-point templates and locate all two-solder-point positions in the chip image using normalized cross-correlation matching. The formula for locating all two-solder-point positions in the chip image using normalized cross-correlation matching is:

[0075] (4);

[0076] in, Template image; The mean of the template image; Image of the chip to be inspected; The average value of the image in the chip image; It is the pixel coordinate position; It is a template image in a chip image. The sliding position.

[0077] S202: Calculate the minimum bounding rectangle of each template's two weld points to obtain the standard width and height. Based on the positions of all located two weld points and their standard width and height, crop each two weld point individually to obtain an independent image of the two weld points. The formula for calculating the minimum bounding rectangle of each template's two weld points to obtain the standard width and height is:

[0078] (5);

[0079] in, It is the average width; It is the average height; The number of template images, .

[0080] It should be noted that during the testing process, situations may arise where two solder joints are stuck together (e.g., Figure 2 As shown in the figure, it is required to inspect each weld point individually. Therefore, it is necessary to obtain the width and height of the two weld points based on the positioning.

[0081] S203: Determine whether a solder joint is missing, defective, or redundant based on the number and area of ​​the two solder joints. It should be noted that: the defect determination is based on the calculated data. If the number of solder joints located is different from the required number, it is determined to be a missing solder joint. If the number of solder joints is correct, the two solder joints are trimmed based on the located position and the adaptively calculated width and height of the two solder joints. The area of ​​the two solder joints is extracted according to formula (1) and the set upper and lower thresholds to determine the defective solder joint. If the area of ​​the two solder joints is greater than the total area of ​​the solder joints within the drawn detection area, it is determined to be a redundant solder joint.

[0082] In S3, gold thread detection includes the following sub-steps:

[0083] S301: Based on the data of the first and second solder joints obtained from the detection of the first and second solder joints, sort the first and second solder joints, and then pair them according to the sorting results by row or column to match the first and second solder joints one by one. Connect the paired first and second solder joints to calculate the theoretical angle, midpoint and length of the gold wire.

[0084] S302: Generate a rectangular detection area for the gold wire adaptively based on the theoretical angle, length, and user-defined expansion parameters. Perform threshold segmentation within the rectangular detection area (threshold segmentation can be completed using formula (1)). Determine whether the gold wire is broken or bent based on its connectivity and whether it exceeds the detection area. Specifically, determining whether the gold wire is broken or bent based on its connectivity and whether it exceeds the detection area is as follows: if the segmented gold wire within the rectangular area is connected and contains one or two solder joints, the gold wire is normal; otherwise, the gold wire is broken. If the gold wire exceeds the rectangular area, it is determined to be bent.

[0085] The theoretical perspective of gold thread Calculated using the following formula:

[0086] (6);

[0087] in, These are the coordinates of a solder joint on the gold wire. These are the coordinates of the two solder points of the gold wire.

[0088] Furthermore, the midpoint of the gold wire The length d is calculated using the following formula:

[0089] (7).

[0090] Furthermore, the rectangular detection area for generating the gold line is specifically as follows:

[0091] The formula for calculating the coordinates of the top right corner vertex of the rectangular detection area for the gold line is as follows:

[0092] (8);

[0093] The formula for calculating the coordinates of the top-left vertex of the rectangular detection area for the gold line is as follows:

[0094] (9);

[0095] The formula for calculating the coordinates of the lower left corner vertex of the rectangular detection area for the gold line is as follows:

[0096] (10);

[0097] The formula for calculating the coordinates of the lower right corner vertex of the rectangular detection area for the gold line is as follows:

[0098] (11);

[0099] in, The parameters for expanding the gold line area are set in a custom way;

[0100] A rectangular detection area for the gold line is generated based on the calculated coordinates of the four vertices.

[0101] The above combined with the appendix Figure 1 , 3 A method for detecting variable solder joints and gold wires in chip inspection according to an embodiment of the present invention is described. Furthermore, the present invention can also be applied to a computer-readable medium having processor-executable non-volatile program code.

[0102] According to a second aspect of the present invention, a computer-readable medium having processor-executable non-volatile program code is provided, the program code causing the processor to perform a method for detecting variable solder joints and gold wires in chip inspection according to a first aspect.

[0103] The readable storage medium can be a computer storage medium or a communication medium. A communication medium includes any medium that facilitates the transfer of a computer program from one location to another. A computer storage medium can be any available medium accessible to a general-purpose or special-purpose computer. For example, a readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an application-specific integrated circuit (ASIC). Alternatively, the ASIC can reside within a device. Of course, the processor and the readable storage medium can also exist as discrete components in a communication device. The readable storage medium can be a read-only memory (ROM), random access memory (RAM), CD-ROM, magnetic tape, floppy disk, and optical data storage device, etc. The present invention also provides a program product including executable instructions stored in the readable storage medium. At least one processor of the device can read the executable instructions from the readable storage medium, and the at least one processor executes the executable instructions to cause the device to implement the method for detecting variable solder joints and gold wires in chip inspection provided by the various embodiments described above. In the embodiments of the above-described device, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly manifested as being executed by a hardware processor, or executed by a combination of hardware and software modules within the processor.

[0104] It should be noted that, in this specification, the terms "comprising," "including," or any other variations thereof are intended to cover a 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..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0105] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for detecting a variable solder joint and gold wire in a chip detection, characterized by, The method comprises the following steps: A solder joint detection: Threshold processing is performed on the obtained chip image to extract a candidate solder joint region meeting a gray scale range, thereby obtaining a solder joint threshold image; The morphological opening operation is used to remove noise interference from a solder joint threshold image, and after removing the interference, a boundary contour point set of a solder joint region is obtained ; calculating the shortest distance from each point inside each pad boundary contour to the pad boundary contour obtaining a distance image, finding the point of maximum value in the distance image then is the center of the inscribed circle of the pad, the distance of the point of maximum value is the radius of the inscribed circle of the pad A center of the inscribed circle is taken as a center, a preset multiple of a radius of the inscribed circle is taken as a search area, and a caliper method is used to extract a solder joint, thereby obtaining an accurate solder joint center position and radius; Solder joint loss, solder ball defect and solder ball residue defect are judged according to a number, an area and an expanded area defect area of the solder joint; A second solder joint detection: A plurality of second solder joint templates are drawn, all second solder joint positions in the chip image are located through normalized cross-correlation matching, and a minimum circumscribed rectangle of each template second solder joint is calculated to obtain a standard width and height. Each second solder joint is individually cropped according to the located all second solder joint positions and the standard width and height of the second solder joint, and an independent second solder joint image is obtained. Solder joint loss, solder joint defect and solder joint redundancy defect are judged according to a number and an area of the second solder joint. Gold wire detection: The first solder joint and the second solder joint are sorted according to the first solder joint and the second solder joint data obtained in the first solder joint detection and the second solder joint detection, then the first solder joint and the second solder joint are matched according to a row or a column according to a sorting result, the first solder joint and the second solder joint are one-to-one corresponding, and a theoretical angle, a midpoint and a length of the gold wire are calculated by connecting and matching the first solder joint and the second solder joint. A rectangular detection area of the gold wire is adaptively generated according to the theoretical angle, the length and a user-defined expanded parameter, threshold segmentation is performed in the rectangular detection area, and gold wire breakage or bending defect is judged according to gold wire connectivity and whether the gold wire exceeds the detection area.

2. The method of claim 1, wherein the detecting of the change in the solder joint and the gold wire is performed by a chip detector. In the first solder joint detection, a formula of threshold processing is as follows: ； wherein, is the gray value of the chip image at coordinate (x, y); is the lower limit of the solder joint gray value; is the upper limit of the solder joint gray value.

3. The method of claim 1, wherein the detecting of the change in the solder joint and the gold wire is performed by a chip detector. An operation formula of the morphological opening operation is as follows: ； wherein is the image to be processed; is the structuring element for the opening operation.

4. The method of claim 1, wherein the detecting of the change in the solder joint and the gold wire is performed by a chip detector. calculating a shortest distance from each point inside each pad boundary contour to the pad boundary contour The formula is: 。 5. The method of claim 1, wherein the detecting of the change in the solder joint and the gold wire is performed by a chip detector. A formula of locating all second solder joint positions in the chip image through normalized cross-correlation matching is as follows: ； wherein, is a template image; is a template image mean; is a chip image to be inspected; is an image mean in the chip image; is a pixel coordinate position; is a sliding position of the template image in the chip image .

6. The method of claim 1, wherein the detecting of the change in the solder joint and the gold wire is performed by a chip detector. A formula of calculating a minimum circumscribed rectangle of each template second solder joint to obtain a standard width and height is as follows: ； wherein is the mean value of the width; is the mean value of the height; is the number of template images, .

7. The method for detecting variable solder joints and gold wires in chip testing as described in claim 1, characterized in that, theoretical angle of the gold wire is calculated by the following equation: ； wherein, is a first solder joint coordinate of the gold wire, is a second solder joint coordinate of the gold wire.

8. The method for detecting variable solder joints and gold wires in chip testing as described in claim 7, characterized in that, the midpoint of the gold wire and the length d is calculated by the following equation: 。 9. The method of claim 8, wherein the detecting of the change in the solder joint and the gold wire is performed by a chip detector. The rectangular detection area of the gold wire is generated in detail as follows: A right upper corner vertex coordinate of the rectangular detection area of the gold wire is calculated, and a formula is as follows: ； A left upper corner vertex coordinate of the rectangular detection area of the gold wire is calculated, and a formula is as follows: ； A left lower corner vertex coordinate of the rectangular detection area of the gold wire is calculated, and a formula is as follows: ； A right lower corner vertex coordinate of the rectangular detection area of the gold wire is calculated, and a formula is as follows: ； wherein, is a gold line region outer expansion parameter set by the user; The rectangular detection area of the gold wire is generated according to the calculated four vertex coordinates.

10. A computer readable medium having non-transitory program code executable by a processor, the program code comprising instructions for: The program code enables the processor to run the chip detection method for detecting variable solder joints and gold wires in any one of claims 1-9.

Images