A method for inspecting the welding quality of LED chips in an LED display screen

Abstract

A method for detecting the welding quality of LED chips of an LED display screen comprises a camera, a moving mechanism, and a control module. The control module forms a plurality of offset graphs by performing multiple offsets on the image, and then adds the sharpness obtained by subtracting the fourth offset graph from the remaining seven offset graphs and the entire image, and performs an absolute value operation to obtain the clarity of the image at the height. Then the moving mechanism moves the camera to find the clearest part of the image according to the change rule, and the control module obtains the final image at the clearest part and determines whether the quality of the solder joint is qualified. Compared with locking a single point and subtracting it from the surrounding points, the whole image is subtracted, and the calculation efficiency is faster, thereby improving the focusing speed, so as to speed up the detection speed of the quality of the LED chip solder joint. In addition, each point in the image is calculated, which not only ensures the high calculation efficiency, but also ensures the accuracy of the data.

Description

Technical Field

[0001] The invention relates to the technical field of LED display screen manufacturing, and in particular to a method for detecting the welding quality of LED chips of an LED display screen. Background Art

[0002] LED display is a flat panel display composed of multiple LED dot matrix. By controlling the brightness and color of LED, the screen display content such as text, pictures, and videos can be changed. Each LED has an LED chip, one end of the LED chip is set on a bracket, and the other end is connected to the power supply. When current flows into the LED chip, it converts electrical energy into light energy to achieve light emission. Therefore, the LED chip is the core component of the LED.

[0003] Before using the LED chip, it is necessary to inspect the solder joints inside the LED chip to detect the quality of the solder joints and avoid the occurrence of poor solder joints, leaking solder joints and other undesirable phenomena. The solutions in the prior art are mainly slow in focusing speed, which leads to too slow detection speed. For some small-sized LED chips, the solder joints are at the micron level. The detection of such micron-level solder joints is generally done manually due to the slow detection speed, that is, the position of the solder joints is manually magnified by a magnifying device to identify the quality of the solder joints, such as a solder joint detection device disclosed in patent number CN201420652724.X. The solder joint detection device detects the quality of the solder joints through a magnifying glass, but the detection speed and accuracy of the naked eye are low, the labor cost is high, and because the detection speed is much lower than the production speed, it is generally a sampling test, and it is impossible to detect all the solder joints of the LED chips. Summary of the invention

[0004] In view of this, the present invention provides a method for detecting the welding quality of LED chips of an LED display screen to solve the above technical problems.

[0005] A method for detecting the welding quality of LED chips of an LED display screen, the LED display screen comprising a frame, a plurality of LED modules arranged in the frame, and a power supply assembly, wherein a plurality of LED lamps are arranged in an array in the LED module, each of the LED lamps is provided with an LED chip and connected to the power supply assembly via a wire, and one end of the wire is welded to the LED chip to form a welding point. The method for detecting the welding quality of LED chips of the LED display screen comprises a camera, a moving mechanism for controlling the camera to move along a height, and a control module. The method for detecting the welding quality of LED chips of the LED display screen comprises the following steps:

[0006] Step S1: Initializing setting parameters in the control module, the parameters including the initial height of the camera and the height value of the camera rising or falling;

[0007] Step S2: The moving mechanism drives the camera to move to the top of the LED lamp, and obtains an image of the welding point at the initial height, and then the control module extracts the gray value of each pixel in the image, the width and height of the image are W-2 pixels × H-2 pixels, and the coordinates of the four corners of the image in the rectangular coordinate system are (0, 0), (0, H-2), (W-2, H-2), and (W-2, 0);

[0008] Step S3: the control module performs multiple shifts on the image, including shifting the image along the X-axis by 1 pixel to obtain a first shift map, shifting the image along the X-axis by 2 pixels to obtain a second shift map, shifting the image along the Y-axis by 1 pixel to obtain a third shift map, shifting the image along the X-axis by 1 pixel and then along the Y-axis by 1 pixel to obtain a fourth shift map, shifting the image along the X-axis by 2 pixels and then along the Y-axis by 1 pixel to obtain a fifth shift map, shifting the image along the Y-axis by 2 pixels to obtain a sixth shift map, shifting the image along the X-axis by 1 pixel and then along the Y-axis by 2 pixels to obtain a seventh shift map, shifting the image along the X-axis by 2 pixels and then along the Y-axis by 2 pixels to obtain an eighth shift map, and the fourth shift map is located at the center of all images;

[0009] Step S4: the control module obtains a plurality of difference values ​​by subtracting the grayscale value of each pixel point in the fourth offset map from the grayscale values ​​of each pixel point in the remaining seven offset maps and the image, and performs the subtraction for the entire image, then adds up all the difference values, and performs an absolute value operation to obtain sum1;

[0010] Step S5: the moving mechanism moves the camera in the height direction by a distance of the height value and re-performs steps S2 to S4 to calculate sum2 of the image at the second height;

[0011] Step S6: the control module compares the sizes of sum1 and sum2 of the images at two heights. When sum becomes larger, the camera moves in the same direction and calculates the sizes of sum at different heights. When sum becomes smaller, the camera moves in the opposite direction and calculates the sizes of sum at different heights. The control module finds the maximum value of sum according to the change rule of sum, which is the clearest part of the image, and then the control module obtains the final image.

[0012] Step S7: the control module performs comprehensive calculation and comparison on the shapes and sizes of the solder joints in the final image, and determines whether the quality of the solder joints is qualified based on the results. If the judgment results are all qualified, the quality of the solder joints is qualified.

[0013] Furthermore, the camera is a thousand-fold large depth-of-field camera, and the depth of field of the camera is between 0.05 mm and 0.1 mm.

[0014] Furthermore, in the above step S1, the parameters also include a maximum threshold and a minimum threshold for allowing the size deviation of the solder joint, and a maximum threshold and a minimum threshold for allowing the shape of the solder joint to deviate from.

[0015] Further, in the above step S7, the judgment basis is that if the size of the weld is between the maximum threshold and the minimum threshold of the allowable deviation of the weld size, the weld size is judged to be qualified; if the shape of the weld is between the maximum threshold and the minimum threshold of the allowable deviation of the weld shape, the weld shape is judged to be qualified.

[0016] Compared with the prior art, the LED chip welding quality detection method of the LED display screen provided by the present invention forms multiple offset graphs by performing multiple offsets on the image, and the offset image has the same grayscale value as each pixel point in the image, but the position is different, and then the grayscale value of each pixel point in the fourth offset graph is subtracted from the grayscale value of each pixel point in the remaining seven offset graphs and the image to obtain multiple differences, and the differences are added, and finally an absolute value operation is performed. The position of the image is pre-set by offsetting, and then the image at the center position is subtracted from the eight surrounding images. Compared with locking a single point in the image and subtracting the point position from the surrounding points, the program logic operation of subtracting the whole image in the algorithm program is faster than the program logic operation of subtracting a single point position, and the operation efficiency is faster, the process of locking each point is omitted, and the calculation can be performed at the same time, thereby improving the operation efficiency, accelerating the focusing speed, and then improving the detection speed of the quality of the LED chip solder joints. In addition, each point in the image is calculated, which not only ensures the high operation efficiency, but also ensures the accuracy of the data. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention provides a flow chart of a method for detecting the welding quality of LED chips of an LED display screen.

[0018] Figure 2 for Figure 1 A rectangular coordinate diagram of an image of a method for detecting the welding quality of LED chips of an LED display screen.

[0019] Figure 3 for Figure 1 A rectangular coordinate diagram of a first offset diagram of a method for detecting the welding quality of LED chips of an LED display screen.

[0020] Figure 4 for Figure 1 A rectangular coordinate diagram of a second offset diagram of a method for detecting the welding quality of LED chips of an LED display screen.

[0021] Figure 5 for Figure 1 A rectangular coordinate diagram of a third offset diagram of the LED chip welding quality detection method of an LED display screen.

[0022] Figure 6 for Figure 1 A rectangular coordinate diagram of a fourth offset diagram of a method for detecting the welding quality of LED chips of an LED display screen.

[0023] Figure 7 for Figure 1 A rectangular coordinate diagram of a fifth offset diagram of the LED chip welding quality detection method of the LED display screen.

[0024] Figure 8 for Figure 1 A rectangular coordinate diagram of a sixth offset diagram of the LED chip welding quality detection method of an LED display screen.

[0025] Fig. 9 for Figure 1 A rectangular coordinate diagram of the seventh offset diagram of the LED chip welding quality detection method of the LED display screen.

[0026] Fig.10 for Figure 1 A rectangular coordinate diagram of the eighth offset diagram of the LED chip welding quality detection method of the LED display screen. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention are further described in detail below. It should be understood that the description of the embodiments of the present invention herein is not intended to limit the protection scope of the present invention.

[0028] like Figures 1 to 10 As shown, it is a flow chart of the LED chip welding quality detection method of the LED display screen provided by the present invention.

[0029] The LED display screen mainly includes a frame, a plurality of LED modules arranged in the frame, and a power supply component that provides energy for the LED modules. It is conceivable that the LED display screen also includes some other functional modules, such as assembly components, and a control system that controls the brightness and color of the LED modules, etc., which are technologies known to those skilled in the art and will not be repeated here. A plurality of LED lamps are arranged in an array in the LED module. Each of the LED lamps is provided with an LED chip and connected to the power supply component through a wire. One end of the wire is welded to the LED chip to form a solder joint, and the surrounding is sealed with epoxy resin. After the current is passed from the power supply component to the LED chip through the wire, the LED chip converts the electrical energy into light to realize the light emission of the LED lamp. The quality of the solder joint formed by the welding of the wire and the LED chip directly affects the current transmission efficiency, so the quality of the solder joint needs to be tested before use.

[0030] The LED chip welding quality detection method of the LED display screen includes a camera, a moving mechanism for controlling the movement of the camera in the height direction, and a control module electrically connected to the camera. The camera is a thousand-fold large depth of field camera, and the depth of field of the camera is between 0.05mm and 0.1mm. The depth of field is a clear range between the object being photographed and the objects in front and behind it, and this range is called the depth of field. A large depth of field can allow the object to have a large range of relatively clear space in front and behind, and a large depth of field camera is more stable, and a slight shake will not cause blurring of the image, which is more conducive to the stability of the detection device. The control module can issue a command to control the movement of the moving mechanism, thereby driving the movement of the camera. When the camera moves to the top of the LED lamp, the camera takes an image of the solder joint of the LED chip. The control module will collect the image data output by the camera and record the position of the image.

[0031] The present invention provides a method for detecting the welding quality of LED chips of an LED display screen, comprising the following steps:

[0032] Step S1: Initializing setting parameters in the control module, the parameters include the initial height of the camera, the height value of the camera rising or falling, the maximum threshold and minimum threshold of the allowable solder joint size deviation, and the maximum threshold and minimum threshold of the allowable solder joint shape deviation.

[0033] Step S2: The moving mechanism drives the camera to move to the top of the LED light, and obtains an image 1 of the solder joint at the initial height, and then the control module extracts the grayscale value of each pixel in the image 1. The width and height of the image 1 are W-2 pixels × H-2 pixels. Figure 2As shown, the coordinates of the four corners of the image 1 in the rectangular coordinate system are (0, 0), (0, H-2), (W-2, H-2), and (W-2, 0). Since the maximum width and height of the image is W×H and the subsequent steps need to be offset, subtracting 2 pixels is to prevent the subsequent offset of the image 100 from exceeding the maximum width and height, which is more in line with the calculation of the actual program.

[0034] Among them, the gray value refers to the color depth of the pixel in the image, and the gray value generally ranges from 0 to 255, with white being 255 and black being 0. The greater the difference in gray value between a single pixel in an image and its surrounding pixels, the greater the difference in color depth between the pixel and its surrounding pixels, and the clearer the image. There are many algorithms for extracting the gray value of an image, such as floating point algorithms, integer algorithms, etc. The algorithm for extracting the gray value of an image should be a prior art and will not be repeated here.

[0035] Step S3: The control module performs multiple shifts on the image 1, including shifting the image 1 by 1 pixel along the X axis to obtain a first shift Figure 2 , the image 1 is shifted by 2 pixels along the X axis to obtain a second shift Figure 3 , the image 1 is shifted by 1 pixel along the Y axis to obtain a third shift Figure 4 The image 1 is shifted by 1 pixel along the X axis and then by 1 pixel along the Y axis to obtain a fourth shift Figure 5 The image 1 is shifted by 2 pixels along the X axis and then by 1 pixel along the Y axis to obtain a fifth shift Figure 6 , the image 1 is shifted by 2 pixels along the Y axis to obtain the sixth shift Figure 7 The image 1 is shifted by 1 pixel along the X axis and then by 2 pixels along the Y axis to obtain the seventh shift Figure 8 The image 1 is shifted by 2 pixels along the X axis and then by 2 pixels along the Y axis to obtain an eighth shift Fig. 9 The grayscale value of each pixel in the offset image is the same as the grayscale value of each pixel in the image 1, but the position is different, and the fourth offset Figure 5 Located at the center of all images to facilitate subsequent image subtraction.

[0036] Step S4: The control module sets the fourth offset Figure 5 The grayscale value of each pixel in the image 1 is subtracted from the grayscale value of each pixel in the other seven offset images and the image 1 to obtain multiple differences, and the subtraction is performed for the entire image. All the differences are then added together and the absolute value operation is performed to obtain sum1, thereby calculating the clarity value of the image 1 at the initial height.

[0037] Since the position of the image 1 is changed due to the shift, the fourth shift Figure 5Located at the center of all images and one pixel away, but the grayscale values ​​of all pixels in all images are the same, so the image at the center is subtracted from the eight surrounding images, which is equivalent to subtracting the grayscale values ​​of each pixel in the image 1 from the eight surrounding pixels. The difference between the grayscale value of a single pixel and the grayscale value of the surrounding pixels, and then add all the differences and perform an absolute value operation to obtain the value sum. The larger the value, the clearer the image, and vice versa. Therefore, sum represents the clarity value of the image 1 at this height. The larger the sum, the clearer the image 1 at this height, and vice versa, so sum is used as the basis for judging clarity. Compared with subtracting a single point and locking the surrounding points, the entire image is subtracted, and the operation efficiency will be faster, and each point is calculated, which can ensure the accuracy of the data and improve the detection accuracy.

[0038] Step S5: the moving mechanism moves the camera in the height direction by a distance of the height value and re-performs steps S2 to S4 to calculate sum2 of the image at the second height.

[0039] Step S6: The control module compares the sizes of sum1 and sum2 of the images at two heights. When sum becomes larger, it proves that the image is becoming clearer, indicating that the camera is moving in the correct direction. The camera moves in the same direction and calculates the sizes of sum at different heights. When sum becomes smaller, it proves that the image is becoming blurred, indicating that the moving direction is wrong. The camera moves in the opposite direction and calculates the sizes of sum at different heights. The control module finds the maximum value of sum according to the changing rule of sum, which is the clearest part of the image, and then the control module obtains the final image at the clearest part.

[0040] Step S7: The control module performs comprehensive calculation and comparison on the shape and size of the solder joints in the final image, and judges whether the quality of the solder joints is qualified based on the results. If the judgment results are all qualified, the solder joint quality is qualified. The judgment basis is that if the size of the solder joint is between the maximum threshold and the minimum threshold of the allowable deviation of the solder joint size, the solder joint size is judged to be qualified. If the shape of the solder joint is between the maximum threshold and the minimum threshold of the allowable deviation of the solder joint shape, the solder joint shape is judged to be qualified.

[0041] In the above step S3, if Figures 2 to 10 As shown, in the rectangular coordinate system, the first offset Figure 2 The coordinates of the four corners are (1, 0), (1, H-2), (W-1, H-2), and (W-1, 0). Figure 3 The coordinates of the four corners are (2, 0), (2, H-2), (W, H-2), and (W, 0). Figure 4The coordinate points of the four corners are (0, 1), (0, H-1), (W-2, H-1), and (W-2, 1). Figure 5 The coordinates of the four corners are (1, 1), (1, H-1), (W-1, H-1), and (W-1, 1). Figure 6 The coordinates of the four corners are (2, 1), (2, H-1), (W, H-1), (W, 1), and (W-2, 1). Figure 7 The coordinates of the four corners are (0, 2), (0, H), (W-2, H), and (W-2, 2). Figure 8 The coordinates of the four corners are (1, 2), (1, H), (W-1, H), and (W-1, 2). Fig. 9 The coordinates of the four corners are (2, 2), (2, H), (W, H), and (W, 2).

[0042] Compared with the prior art, the LED chip welding quality detection method of the LED display screen provided by the present invention forms a plurality of offset graphs by performing multiple offsets on the image 1, wherein the offset images have the same grayscale value as each pixel point in the image 1, but the positions are different, and then the fourth offset graph is used to detect the welding quality of the LED chip of the LED display screen provided by the present invention. Figure 5 The grayscale values ​​of each pixel in the image are subtracted from the grayscale values ​​of each pixel in the other seven offset images and the image 1 to obtain multiple differences, and the differences are added, and finally the absolute value operation is performed. The position of the image is pre-set by offset, and then the image at the center position is subtracted from the eight surrounding images. Compared with locking a single point in the image and subtracting it from the surrounding points, the program logic operation of subtracting the entire image in the algorithm program is faster than the program logic operation of subtracting a single point, eliminating the process of locking each point and performing calculations at the same time, thereby improving the calculation efficiency, accelerating the focusing speed, and then improving the detection speed of the quality of the LED chip solder joints. In addition, each point in the image 1 is calculated, which not only ensures the high calculation efficiency, but also ensures the accuracy of the data.

[0043] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modification, equivalent substitution or improvement within the spirit of the present invention is included in the scope of the claims of the present invention.

Claims

1. A method for detecting the welding quality of LED chips of an LED display screen, wherein the LED display screen comprises a frame, a plurality of LED modules arranged in the frame, and a power supply assembly, wherein a plurality of LED lamps are arranged in an array in the LED module, each of the LED lamps is provided with an LED chip and connected to the power supply assembly through a wire, and one end of the wire is welded to the LED chip to form a welding point, wherein: The LED chip welding quality detection method of the LED display screen includes a camera, a moving mechanism for controlling the camera to move in a height direction, and a control module. The LED chip welding quality detection method of the LED display screen includes the following steps: Step S1: Initializing setting parameters in the control module, the parameters including the initial height of the camera and the height value of the camera rising or falling; Step S2: The moving mechanism drives the camera to move to the top of the LED lamp, and obtains an image of the welding point at the initial height, and then the control module extracts the gray value of each pixel in the image, the width and height of the image are W-2 pixels × H-2 pixels, and the coordinates of the four corners of the image in the rectangular coordinate system are (0, 0), (0, H-2), (W-2, H-2), and (W-2, 0); Step S3: the control module performs multiple shifts on the image, including shifting the image along the X-axis by 1 pixel to obtain a first shift map, shifting the image along the X-axis by 2 pixels to obtain a second shift map, shifting the image along the Y-axis by 1 pixel to obtain a third shift map, shifting the image along the X-axis by 1 pixel and then along the Y-axis by 1 pixel to obtain a fourth shift map, shifting the image along the X-axis by 2 pixels and then along the Y-axis by 1 pixel to obtain a fifth shift map, shifting the image along the Y-axis by 2 pixels to obtain a sixth shift map, shifting the image along the X-axis by 1 pixel and then along the Y-axis by 2 pixels to obtain a seventh shift map, shifting the image along the X-axis by 2 pixels and then along the Y-axis by 2 pixels to obtain an eighth shift map, and the fourth shift map is located at the center of all images; Step S4: the control module obtains a plurality of difference values ​​by subtracting the grayscale value of each pixel point in the fourth offset map from the grayscale values ​​of each pixel point in the remaining seven offset maps and the image, and performs the subtraction for the entire image, then adds up all the difference values, and performs an absolute value operation to obtain sum1; Step S5: the moving mechanism moves the camera in the height direction by a distance of the height value and re-performs steps S2 to S4 to calculate sum2 of the image at the second height; Step S6: the control module compares the sizes of sum1 and sum2 of the images at two heights. When sum becomes larger, the camera moves in the same direction and calculates the sizes of sum at different heights. When sum becomes smaller, the camera moves in the opposite direction and calculates the sizes of sum at different heights. The control module finds the maximum value of sum according to the change rule of sum, which is the clearest part of the image, and then the control module obtains the final image. Step S7: the control module performs comprehensive calculation and comparison on the shapes and sizes of the solder joints in the final image, and determines whether the quality of the solder joints is qualified based on the results. If the judgment results are all qualified, the quality of the solder joints is qualified.

2. The method for detecting the welding quality of LED chips of an LED display screen according to claim 1, characterized in that: The camera is a thousand-fold large depth-of-field camera, and the depth of field of the camera is between 0.05 mm and 0.1 mm.

3. The method for detecting the welding quality of LED chips of an LED display screen according to claim 1, characterized in that: In the above step S1, the parameters also include a maximum threshold and a minimum threshold for the allowable deviation of the size of the solder joint, and a maximum threshold and a minimum threshold for the allowable deviation of the shape of the solder joint.

4. The method for detecting the welding quality of LED chips of an LED display screen as claimed in claim 3, characterized in that: In the above step S7, the judgment basis is that if the size of the solder joint is between the maximum threshold and the minimum threshold of the allowable deviation of the solder joint size, the solder joint size is judged to be qualified; if the shape of the solder joint is between the maximum threshold and the minimum threshold of the allowable deviation of the solder joint shape, the solder joint shape is judged to be qualified.

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