A ball grid array package chip automatic laser solder ball welding method and related equipment

Abstract

The present application relates to the field of welding technology, and in particular to a method for automatic laser solder ball welding of a ball grid array package chip and related equipment, the method comprising: obtaining the target coordinates of the nozzle corresponding to the nozzle welding position; judging whether the target coordinates meet the preset coordinate requirements; if the target coordinates meet the preset coordinate requirements, judging whether it is necessary to calculate the nozzle welding height; if it is necessary to calculate the nozzle welding height, obtaining the nozzle welding height and lowering the nozzle to the nozzle welding height; based on the target coordinates, controlling the solder ball to fall into the nozzle, and controlling the laser to emit light for welding; judging whether the welding result meets the preset welding requirements; if the welding result meets the preset welding requirements, ending the current welding process. The present application helps to improve the welding effect.

Description

Technical Field

[0001] The present application relates to the field of welding technology, and in particular to an automatic laser solder ball welding method for ball grid array packaged chips and related equipment. Background Art

[0002] At present, in the packaging and assembly process of electronic products, solder is needed to connect different electronic components. For example, in the flip chip process of connecting the chip to the printed circuit board, the surface mounting (SMT) process of connecting the BGA packaged product to the circuit board, etc., solder balls are needed to connect the chip and the printed circuit board or to connect the BGA (ball grid array) package and the circuit board.

[0003] Ball Grid Array (BGA) packaging is a packaging body substrate on the back of the ball contacts as pins in an array, so the array of solder balls as the I / O end of the circuit and the printed circuit board (PCB) interconnect. Because of its smaller footprint, smaller profile, more pins and better assembly yield, it is widely used in network equipment, electronic communications and automobiles and other fields.

[0004] In the related technology, reflow soldering technology is mainly used for soldering. However, reflow soldering requires printing flux. The flux may generate gas during the subsequent reflow soldering heating process, and the gas will escape from the solder ball. If the gas does not escape or escapes insufficiently, pores and voids will be generated in the solder ball. In addition, when the flux is heated in the reflow soldering equipment, splashing may occur, which may cause adverse conditions such as burns to the soldered products. Summary of the invention

[0005] In order to help improve the welding effect, the present application provides a ball grid array package chip automatic laser solder ball welding method and related equipment.

[0006] In the first aspect, the present application provides an automatic laser solder ball welding method for ball grid array package chips, which adopts the following technical solution:

[0007] An automatic laser solder ball welding method for a ball grid array package chip, comprising:

[0008] Obtain the target coordinates of the nozzle corresponding to the nozzle welding position;

[0009] Determine whether the target coordinates meet preset coordinate requirements;

[0010] If the target coordinates meet the preset coordinate requirements, determining whether it is necessary to calculate the nozzle welding height;

[0011] If the nozzle welding height needs to be calculated, the nozzle welding height is obtained, and the nozzle is lowered to the nozzle welding height;

[0012] Based on the target coordinates, the solder ball is controlled to fall into the nozzle, and the laser is controlled to emit light for welding;

[0013] Determine whether the welding results meet the preset welding requirements;

[0014] If the welding result meets the preset welding requirement, the current welding process is terminated.

[0015] By adopting the above technical solution, the target coordinates of the nozzle at the welding position are first obtained, and it is determined whether the target coordinates meet the preset coordinate requirements; if they do, it indicates that the obtained target coordinates are correct coordinates that meet the requirements, and it is further determined whether the nozzle welding height needs to be calculated; if it does, it indicates that the nozzle welding height corresponding to this welding operation is different from that of the previous welding operation, and it is necessary to re-acquire the nozzle welding height, so the nozzle welding height is recalculated, and the nozzle is lowered to the nozzle welding height, the tin ball is controlled to fall into the nozzle, and the laser is controlled to emit light, so that the tin ball in the nozzle is melted and ejected by heat, thereby completing the welding; after the welding is completed, it is further determined whether the welding result meets the preset welding requirements. If it does, it indicates that the welding effect is good and there is no defect in the welded product, so the current welding process is terminated;

[0016] After adjusting the nozzle welding height, heating the solder ball with laser helps to accurately control the heat transfer to the product being welded. On the one hand, it has high energy utilization rate and is environmentally friendly and energy-saving. On the other hand, it avoids scalding and burns to the product being welded due to excessive heat and insufficient tin fluidity and insufficient tin pads due to insufficient heat. In addition, using laser to directly heat the solder ball does not require the use of flux, which helps to reduce the occurrence of pores, voids and burns, thereby improving the welding effect.

[0017] Optionally, obtaining the target coordinates of the nozzle corresponding to the nozzle welding position includes:

[0018] Move the visual positioning camera to the visual photo taking position;

[0019] Control the visual positioning camera to take pictures and calculate the target coordinates of the nozzle corresponding to the nozzle welding position.

[0020] Optionally, controlling the visual positioning camera to take pictures and calculating the target coordinates of the nozzle corresponding to the nozzle welding position includes:

[0021] Setting positioning parameters, and controlling the visual positioning camera to capture a standard image based on the positioning parameters;

[0022] Optimizing the standard image, and creating an image template based on the standard image and a normalized cross-correlation algorithm;

[0023] Controlling the visual positioning camera to capture a target image;

[0024] Optimizing the target image, and searching for pad pixel coordinates based on the image template and the target image;

[0025] Based on the pad pixel coordinates and a preset calibration conversion relationship, the target coordinates of the nozzle corresponding to the nozzle welding position are calculated.

[0026] Optionally, the controlling the solder ball to fall into the nozzle based on the target coordinates and controlling the laser to emit light for welding includes:

[0027] Control the turntable to rotate and make the solder ball fall into the nozzle;

[0028] Control the laser to emit light, and make the solder ball in the nozzle melt and eject;

[0029] Raise the nozzle to a safe height.

[0030] Optionally, controlling the laser to emit light and causing the solder ball in the nozzle to melt and spray out by heating includes:

[0031] Get the melting point temperature of solder ball and the real-time temperature of welding area;

[0032] Obtaining a temperature difference between the melting point temperature and the real-time temperature;

[0033] Based on the temperature difference and the preset control rules, the light emitting power of the laser is adjusted, and the solder ball in the nozzle is heated, melted and ejected.

[0034] Optionally, the determining whether the welding result meets the preset welding requirements includes:

[0035] Acquire detection images;

[0036] Input the detection image into a preset neural network model and output solder joint data, wherein the solder joint data includes solder leak status, tin coverage rate, solder ball offset degree, tin connection status and overall solder joint morphology characteristics;

[0037] Determining whether the solder joint data meets corresponding data requirements;

[0038] If the welding point data meets the corresponding data requirements, it is determined that the welding result meets the preset welding requirements;

[0039] If the welding point data does not meet the corresponding data requirement, it is determined that the welding result does not meet the preset welding requirement.

[0040] Optionally, before inputting the detection image into a preset neural network model and outputting the welding point data, the method further includes:

[0041] Extracting geometric information of the edge contour of the chip reference point in the detection image based on a sub-pixel edge extraction algorithm;

[0042] Based on the geometric information, positionally matching the reference point contour with the standard reference point contour and generating a matching result;

[0043] Based on the matching result, calculating the position offset;

[0044] Based on the position offset, the image pixel position of the pad is obtained.

[0045] In the second aspect, the present application also discloses an automatic laser solder ball welding system for ball grid array package chips, which adopts the following technical solution:

[0046] An automatic laser solder ball welding system for ball grid array package chips, comprising:

[0047] A first acquisition module is used to acquire the target coordinates of the nozzle corresponding to the nozzle welding position;

[0048] A first judging module, used to judge whether the target coordinates meet the preset coordinate requirements;

[0049] A second judgment module, if the target coordinates meet the preset coordinate requirements, the second judgment module is used to judge whether it is necessary to calculate the nozzle welding height;

[0050] A second acquisition module, if it is necessary to calculate the nozzle welding height, the second acquisition module is used to acquire the nozzle welding height based on the target coordinates, and lower the nozzle to the nozzle welding height;

[0051] A first execution module is used to control the solder ball to fall into the nozzle based on the target coordinates, and control the laser to emit light for welding;

[0052] The third judgment module is used to judge whether the welding result meets the preset welding requirements;

[0053] The second execution module is used to end the current welding process if the welding result meets the preset welding requirement.

[0054] By adopting the above technical solution, the target coordinates of the nozzle at the welding position are first obtained, and it is determined whether the target coordinates meet the preset coordinate requirements; if they do, it indicates that the obtained target coordinates are correct coordinates that meet the requirements, and it is further determined whether the nozzle welding height needs to be calculated; if it does, it indicates that the nozzle welding height corresponding to this welding operation is different from that of the previous welding operation, and it is necessary to re-acquire the nozzle welding height, so the nozzle welding height is recalculated, and the nozzle is lowered to the nozzle welding height, the tin ball is controlled to fall into the nozzle, and the laser is controlled to emit light, so that the tin ball in the nozzle is melted and ejected by heat, thereby completing the welding; after the welding is completed, it is further determined whether the welding result meets the preset welding requirements. If it does, it indicates that the welding effect is good and there is no defect in the welded product, so the current welding process is terminated;

[0055] After adjusting the nozzle welding height, heating the solder ball with laser helps to accurately control the heat transfer to the product being welded. On the one hand, it has high energy utilization rate and is environmentally friendly and energy-saving. On the other hand, it avoids scalding and burns to the product being welded due to excessive heat and insufficient tin fluidity and insufficient tin pads due to insufficient heat. In addition, using laser to directly heat the solder ball does not require the use of flux, which helps to reduce the occurrence of pores, voids and burns, thereby improving the welding effect.

[0056] In a third aspect, the present application provides a computer device, which adopts the following technical solution:

[0057] An intelligent terminal comprises a memory and a processor, wherein the memory is used to store a computer program that can be run on the processor, and when the processor loads the computer program, the method of the first aspect is executed.

[0058] By adopting the above technical solution, a computer program is generated based on the method of the first aspect and stored in a memory to be loaded and executed by a processor, thereby manufacturing an intelligent terminal based on the memory and the processor for user convenience.

[0059] In a fourth aspect, the present application provides a computer-readable storage medium, which adopts the following technical solution:

[0060] A computer-readable storage medium stores a computer program, and when the computer program is loaded by a processor, the method of the first aspect is executed.

[0061] By adopting the above technical solution, a computer program is generated based on the method of the first aspect and stored in a computer-readable storage medium so as to be loaded and executed by a processor. The computer-readable storage medium facilitates the readability and storage of the computer program.

[0062] In summary, this application includes the following beneficial technical effects:

[0063] After adjusting the nozzle welding height, heating the solder ball with laser helps to accurately control the heat transfer to the product being welded. On the one hand, it has high energy utilization rate and is environmentally friendly and energy-saving. On the other hand, it avoids scalding and burns to the product being welded due to excessive heat and insufficient tin fluidity and insufficient tin pads due to insufficient heat. In addition, using laser to directly heat the solder ball does not require the use of flux, which helps to reduce the occurrence of pores, voids and burns, thereby improving the welding effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is a main flow chart of an automatic laser solder ball welding method for a ball grid array package chip according to an embodiment of the present application;

[0065] Figure 2 is a step flow chart from step S201 to step S202;

[0066] Figure 3 is a flowchart of steps S301 to S305;

[0067] Figure 4 is a flowchart of steps S401 to S403;

[0068] Figure 5 is a flowchart of steps S501 to S503;

[0069] Figure 6 is a flowchart of steps S601 to S605;

[0070] Figure 7 is a flowchart of steps S701 to S704;

[0071] Figure 8 This is a module diagram of an automatic laser solder ball welding system for a ball grid array packaged chip according to an embodiment of the present application.

[0072] Description of reference numerals:

[0073] 1. First acquisition module; 2. First judgment module; 3. Second judgment module; 4. Second acquisition module; 5. First execution module; 6. Third judgment module; 7. Second execution module. DETAILED DESCRIPTION

[0074] In a first aspect, the present application discloses an automatic laser solder ball welding method for ball grid array packaged chips.

[0075] Reference Figure 1, a method for automatic laser solder ball welding of ball grid array package chips, comprising steps S101 to S107:

[0076] Step S101: obtaining the target coordinates of the nozzle corresponding to the nozzle welding position.

[0077] Specifically, in this embodiment, the target position is the position of the nozzle corresponding to the nozzle welding position.

[0078] Step S102: Determine whether the target coordinates meet preset coordinate requirements.

[0079] Specifically, in this embodiment, the preset coordinate requirement is a pre-set criterion for determining whether the target coordinates are correct coordinates. By using the preset coordinate requirement, it can be determined whether the acquired target coordinates are valid coordinates.

[0080] Step S103: If the target coordinates meet the preset coordinate requirements, determine whether it is necessary to calculate the nozzle welding height.

[0081] Specifically, the nozzle welding height refers to the height of the nozzle during welding. In this embodiment, the nozzle welding height can be calculated by controlling the movement of the mobile motor, moving the laser displacement sensor to the height measuring position, and obtaining the measurement value of the laser displacement sensor. It is worth noting that if the same type of welding operation is performed and the nozzle welding height does not need to be adjusted, there is no need to repeatedly calculate the nozzle welding height.

[0082] Step S104: if the nozzle welding height needs to be calculated, the nozzle welding height is obtained, and the nozzle is lowered to the nozzle welding height.

[0083] Specifically, in this embodiment, after the nozzle welding height is obtained, the nozzle is lowered to the nozzle welding height to prepare for welding.

[0084] Step S105: Based on the target coordinates, control the solder ball to fall into the nozzle, and control the laser to emit light for welding.

[0085] Specifically, before welding, the PCB and the pin parts are assembled together, that is, the pins of the pin parts are inserted into the through holes of the PCB. In this embodiment, the pins can be inserted manually or automatically, and then the assembled parts are placed as a whole in a preset profiling jig. The profiling jig is specially designed according to the processed PCB and the pin parts, and can make the upper surface of the PCB flat and stable. At this time, the pins protrude from the upper surface of the PCB, and the semiconductor devices are located on the lower surface of the PCB; the jig enters the equipment through the double-track belt assembly line; when the jig arrives at the first workstation, the double-track belt assembly line stops automatically, and the jig is blocked by the cylinder and stops at a fixed position.

[0086] The first workstation has a tin ring box. Different tin ring boxes contain tin rings of different specifications (tin ring thickness, tin ring inner diameter, and tin ring outer diameter). Tin rings of different specifications correspond to different PCB through-holes and pins of different diameters. The volume of the tin ring is slightly larger than the volume of the PCB through-hole minus the volume of the pin in the through-hole, so that the melted tin alloy fills the gap of the PCB through-hole and tries to achieve a tin penetration rate of 100%. The inner diameter of the tin ring is as close as possible to the diameter of the pin, so that the tin ring can absorb more laser light and prevent the laser from entering the through-hole. Tin rings of different specifications have corresponding nozzles for suction. Before sucking the tin ring, take a photo of the position of the tin ring, and then take a photo of the position of the inner hole of the tin ring from below after sucking it. Then the robot grabs the tin ring to the top of the pin, takes a photo of the position of the pin, and then puts the tin ring on the pin.

[0087] The second station is mainly for dispensing solder paste, the principle is similar to dispensing glue with a dispensing machine; the tin alloy used in this station is in paste form, the solder paste is placed in a syringe, and squeezed out of the syringe. Before dispensing solder paste, the pin is positioned so that the solder paste can be accurately squeezed to the top of the pin; dispensing solder paste on the top of the pin makes the gap between the tin ring and the pin further blocked by the solder paste when viewed from above, thereby further reducing the laser from penetrating the gap between the tin ring and the pin into the PCB through-hole.

[0088] The third workstation is mainly for laser welding. First, find the periphery of the tin ring to determine the center point of the pin; then emit laser to heat the solder paste and tin ring, melt the solder paste and tin ring into liquid, and flow into the PCB through-hole along the pin; the laser welding head part has a monitoring camera, which is connected to the monitoring screen, so that personnel can observe the welding process conveniently.

[0089] Step S106: Determine whether the welding result meets the preset welding requirements.

[0090] Specifically, in this embodiment, the preset welding requirement is a pre-set criterion for judging whether the welding result is qualified. The criterion can be set according to relevant regulations or according to user needs.

[0091] Step S107: Determine whether the welding result meets the preset welding requirements.

[0092] The automatic laser solder ball welding method for ball grid array packaged chips provided in the present embodiment first obtains the target coordinates of the nozzle at the welding position, and determines whether the target coordinates meet the preset coordinate requirements; if so, it indicates that the obtained target coordinates are correct coordinates that meet the requirements, and further determines whether it is necessary to calculate the nozzle welding height; if so, it indicates that the nozzle welding height corresponding to this welding operation is different from that of the previous welding operation, and it is necessary to re-acquire the nozzle welding height, so the nozzle welding height is recalculated, and the nozzle is lowered to the nozzle welding height, the solder ball is controlled to fall into the nozzle, and the laser is controlled to emit light, so that the solder ball in the nozzle is melted and ejected by heat, thereby completing the welding; after the welding is completed, it is further determined whether the welding result meets the preset welding requirements. If so, it indicates that the welding effect is good and there is no defect in the welded product, so the current welding process is terminated.

[0093] After adjusting the nozzle welding height, heating the solder ball with laser helps to accurately control the heat transfer to the product being welded. On the one hand, it has high energy utilization rate and is environmentally friendly and energy-saving. On the other hand, it avoids scalding and burns to the product being welded due to excessive heat and insufficient tin fluidity and insufficient tin pads due to insufficient heat. In addition, using laser to directly heat the solder ball does not require the use of flux, which helps to reduce the occurrence of pores, voids and burns, thereby improving the welding effect.

[0094] Reference Figure 2 In one implementation of this embodiment, step S101 of obtaining the target coordinates of the nozzle corresponding to the nozzle welding position includes steps S201 to S202:

[0095] Step S201: Move the visual positioning camera to the visual photographing position.

[0096] Specifically, the visual positioning camera is moved to the visual photographing position by controlling the moving axis of the mobile motor. In this embodiment, the visual photographing position is above the reference point of the chip.

[0097] Step S202: Control the visual positioning camera to take pictures and calculate the target coordinates of the nozzle corresponding to the nozzle welding position.

[0098] Specifically, in this embodiment, according to the characteristics of different chips, a dedicated positioning reference point can be selected or the chip pad can be used as a reference point, and the target coordinates can be calculated through the position of the reference point.

[0099] The automatic laser solder ball welding method for ball grid array packaged chips provided in this embodiment uses a visual positioning camera to take a picture of the chip at a visual photographing position, and calculates the target coordinates based on the basic point position. By calculating the target coordinates, it helps to weld the object to be welded more accurately.

[0100] Reference Figure 3 In one implementation of this embodiment, step S202 controls the visual positioning camera to take pictures and calculates the target coordinates of the nozzle corresponding to the nozzle welding position, including steps S301 to S305:

[0101] Step S301: setting positioning parameters, and controlling the visual positioning camera to capture a standard image based on the positioning parameters.

[0102] Specifically, in this embodiment, after the positioning parameters are set, a standard image is first captured by a visual positioning camera, and the standard image is used for image positioning and creating an image template.

[0103] Step S302: Optimizing the standard image, and creating an image template based on the standard image and a normalized cross-correlation algorithm.

[0104] Specifically, the optimization process includes filtering and denoising the standard image; an image template is created by performing a normalization correlation algorithm on the standard image, and the image template records the pixel features of the standard image.

[0105] Step S303: controlling the visual positioning camera to capture a target image.

[0106] Step S304: Optimize the target image and search for pad pixel coordinates based on the image template and the target image.

[0107] Specifically, in this embodiment, during the image positioning process, the camera is controlled to take a target photo, and the target image is preprocessed by filtering and denoising. Next, the pad pixel coordinates in the target image are searched using an image template created according to the standard image. The pad pixel coordinates are the pixel coordinates of the pad position in the target image according to the coordinate rule set by the image template, wherein the coordinate rule includes the setting of the coordinate origin position, etc.

[0108] Step S305: Calculating the target coordinates of the nozzle corresponding to the nozzle welding position based on the pad pixel coordinates and a preset calibration conversion relationship.

[0109] Specifically, in this embodiment, the target coordinates corresponding to the nozzle welding position are calculated using the calibration conversion relationship between the pixel coordinates and the motor coordinates, wherein the calibration conversion relationship between the pixel coordinates and the motor coordinates is a preset setting, and the target coordinates include the motor motion axis coordinates.

[0110] The automatic laser solder ball welding method for ball grid array packaged chips provided in this embodiment creates an image template based on a standard image and a normalized cross-correlation algorithm, then uses the image template to search for the pixel coordinates of the pad in the target image, and finally calculates the target coordinates corresponding to the nozzle welding position based on the calibration conversion relationship between the pixel coordinates and the motor coordinates, thereby completing visual positioning.

[0111] Reference Figure 4 In one implementation of this embodiment, step S105 controls the solder ball to fall into the nozzle based on the target coordinates, and controls the laser to emit light for welding, including steps S401 to S403:

[0112] Step S401: Control the turntable to rotate and make the solder ball fall into the nozzle.

[0113] Specifically, in this embodiment, the rotating motor is controlled to drive the turntable to rotate and make the solder ball fall into the nozzle.

[0114] Step S402: Control the laser to emit light, so that the solder ball in the nozzle is heated, melted and ejected.

[0115] Specifically, in this embodiment, after the solder ball falls into the nozzle, the laser is controlled to emit light, the laser contacts the surface of the solder ball, and the solder ball is heated and melted and then ejected.

[0116] Step S403: Raise the nozzle to a safe height.

[0117] Specifically, after welding is completed, the nozzle is adjusted up to a safe height. In this embodiment, the safe height can be set according to the melting point temperature of the solder ball or related standards, or can be set according to user needs.

[0118] It is worth noting that in the present embodiment, laser is used to directly heat the solder ball, and the solder ball directly completes the heating-melting-resolidification process on the surface of the pad, and there is no need to pre-place brazing flux on the surface of the pad, thereby reducing the equipment and process for applying the flux; in addition, the conventional method requires the use of flux, and the flux is prone to form gas when heated. If the gas cannot completely escape from the tin alloy, or partially remains in the tin alloy, then after cooling, bubbles or voids will exist in the solder joint (the re-cooled tin alloy), causing defects; and if the flux escapes quickly in the form of airflow, it is easy to cause splashing. If it splashes onto the surrounding pads, it is easy to cause contamination or even a short circuit. In the present embodiment, there is no need to use flux, so there is no need to clean the residual and splashed flux after welding, thereby reducing the equipment and process for cleaning the flux.

[0119] The automatic laser solder ball welding method for ball grid array packaged chips provided in this embodiment heats the solder ball through laser after the solder ball falls into the nozzle, and the solder ball is melted by the heat and then ejected, thereby completing the welding.

[0120] Reference Figure 5 In one implementation of this embodiment, step S402 controls the laser to emit light, and causes the solder ball in the nozzle to melt and spray out by heating, including steps S501 to S503:

[0121] Step S501: Obtain the melting point temperature of the solder ball and the real-time temperature of the soldering area.

[0122] Specifically, in this embodiment, the melting point temperature of the tin ball varies according to the proportion of the tin content in the tin ball. For example, the melting point of lead solder (tin content 63%, lead content 37%) is about 183°C, while the melting point of lead-free solder (tin 99.3%, copper 0.7%) is about 220°C; the real-time temperature of the welding area refers to the real-time temperature of the laser focus position. In this embodiment, the real-time temperature of the welding area also refers to the center position of the tin ball. In this embodiment, a temperature monitor is provided on the laser welding head part for monitoring the real-time temperature of the welding area.

[0123] Step S502: Obtain the temperature difference between the melting point temperature and the real-time temperature.

[0124] Specifically, in this embodiment, the temperature difference is the difference obtained by subtracting the melting point temperature from the real-time temperature. For example, if the real-time temperature is 221° C. and the melting point temperature is 220° C., the temperature difference is 221-220=1° C.

[0125] Step S503: Based on the temperature difference and the preset control rule, the laser light power is adjusted to melt the solder ball in the nozzle and eject it.

[0126] Specifically, the preset control rule is a pre-set rule for adjusting the light emitting power of the laser emitter according to the temperature difference. In this embodiment, when the temperature difference is less than 0, the light emitting power of the laser emitter is increased, and when the temperature difference is greater than 0, the light emitting power of the laser emitter is reduced, so that the real-time temperature of the welding area is always maintained at the set temperature, wherein the set temperature is the melting point temperature of the solder ball; therefore, during the welding process, the real-time temperature of the welding area will not exceed the melting point temperature of the tin alloy, and maintain the laser energy (i.e., heat) input that can melt the solder ball but is not too high, thereby better protecting the PCB and semiconductor devices from damage during laser welding and heating.

[0127] In addition, in this embodiment, in order to improve the tin penetration rate, a heating platform can be set under the PCB. The heating platform emits infrared rays to heat the PCB. Especially for the case where the PCB is thicker, the heating platform can keep the tin alloy in the PCB through-hole liquid and fluid, so that it gradually penetrates to the lower surface of the PCB.

[0128] The automatic laser solder ball welding method for ball grid array packaged chips provided in this embodiment obtains the temperature difference between the melting point temperature of the solder ball and the real-time temperature of the welding area, and adjusts the laser light power according to the preset control rules and the temperature difference, so that the solder ball can be melted smoothly and the PCB and semiconductor devices can be better protected from damage during laser welding and heating.

[0129] Reference Figure 6 In one implementation of this embodiment, step S106 determines whether the welding result meets the preset welding requirements, including steps S601 to S605:

[0130] Step S601: Acquire a detection image.

[0131] Specifically, four images at different angles are taken by the camera as the detection images. In this embodiment, the annular light source in the computer vision module is turned on in the order of front, back, left and right angles, and the camera shoots the solder joints from a vertical direction. Under the illumination of light sources at different angles, the solder will have different pixel grayscale value distributions on the pad, showing different image features; through contrast enhancement, histogram equalization and filtering algorithms, the contrast of the pad is improved, the noise is reduced, and it is easier to distinguish.

[0132] Step S602: input the detection image into a preset neural network model and output welding point data.

[0133] Specifically, in this embodiment, the preset neural network model is a pre-trained neural network model. By inputting the detection image into the preset neural network model, the preset neural network model will output corresponding solder joint data according to the detection image. The solder joint data includes the solder leak condition, tin coverage, solder ball offset degree, tin connection condition and the overall solder joint morphology characteristics.

[0134] It is worth noting that the training process of the preset neural network model includes: first, using the convolutional neural network layer to extract features from the manually pre-labeled pad image data; second, classifying and learning these feature vectors through the fully connected neural network layer; in the classification learning process, the back propagation algorithm is used to update the node weights of the neural network; once the model completes automatic learning, it will be verified on the image test set; the tested model will be applied to the post-soldering inspection of chip pads.

[0135] Step S603: Determine whether the solder joint data meets the corresponding data requirements.

[0136] Specifically, in this embodiment, the data requirement is a criterion for judging whether the solder joint data is qualified, and different types of solder joint data have corresponding data requirements.

[0137] Step S604: If the welding point data meets the corresponding data requirements, it is determined that the welding result meets the preset welding requirements.

[0138] Step S605: If the welding point data does not meet the corresponding data requirements, it is determined that the welding result does not meet the preset welding requirements.

[0139] The automatic laser solder ball welding method for ball grid array packaged chips provided in this embodiment inputs the detection image into a preset neural network model, outputs the corresponding solder joint data, and determines whether the solder joint data meets the corresponding data requirements, and finally determines whether the welding result meets the preset welding requirements based on the judgment result.

[0140] Reference Figure 7 In one implementation of this embodiment, before inputting the detection image into a preset neural network model in step S602 and outputting the welding point data, the method further includes steps S701 to S704:

[0141] Step S701: extracting geometric information of the edge contour of the chip reference point in the detection image based on a sub-pixel edge extraction algorithm.

[0142] Specifically, in this embodiment, the geometric information includes information such as shape, position, and size.

[0143] Step S702: Based on the geometric information, positionally match the reference point contour with the standard reference point contour, and generate a matching result.

[0144] Specifically, the precise placement of each chip to be inspected has a certain degree of randomness. Before inspecting the pad, the pad needs to be accurately positioned. Therefore, it is necessary to first take an image with a post-weld inspection camera as a positioning image. The standard reference point contour is the contour of the reference point in the positioning image. In this embodiment, when taking the positioning image, it is necessary to control the annular light source to be adjusted to uniform illumination and appropriate brightness; the matching result is the result generated by comparing the reference point contour with the standard reference point contour, and the matching result includes the geometric information of the reference point contour and the standard reference point contour.

[0145] Step S703: Calculate the position offset based on the matching result.

[0146] Specifically, in this embodiment, the position offset is the offset between the reference point and the standard reference point.

[0147] Step S704: based on the position offset, obtaining the image pixel position of the pad.

[0148] The automatic laser solder ball welding method for ball grid array packaged chips provided in this embodiment extracts the geometric information of the edge contour of the chip reference point in the detection image, and then matches the reference point contour with the standard reference point contour based on the geometric information, and then calculates the position offset based on the matching result, and finally calculates the image pixel position of the pad based on the position offset.

[0149] In a second aspect, the present application also discloses an automatic laser solder ball welding system for ball grid array packaged chips.

[0150] Reference Figure 8 , an automatic laser solder ball welding system for ball grid array package chips, comprising:

[0151] A first acquisition module is used to acquire the target coordinates of the nozzle corresponding to the nozzle welding position;

[0152] A first judging module, used to judge whether the target coordinates meet the preset coordinate requirements;

[0153] A second judgment module, if the target coordinates meet the preset coordinate requirements, the second judgment module is used to judge whether it is necessary to calculate the nozzle welding height;

[0154] A second acquisition module, if it is necessary to calculate the nozzle welding height, the second acquisition module is used to acquire the nozzle welding height based on the target coordinates, and lower the nozzle to the nozzle welding height;

[0155] A first execution module is used to control the solder ball to fall into the nozzle based on the target coordinates, and control the laser to emit light for welding;

[0156] The third judgment module is used to judge whether the welding result meets the preset welding requirements;

[0157] The second execution module is used to end the current welding process if the welding result meets the preset welding requirement.

[0158] In a third aspect, an embodiment of the present application discloses an intelligent terminal, including a memory and a processor. The memory is used to store a computer program that can be run on the processor. When the processor loads the computer program, it executes an automatic laser solder ball welding method for a ball grid array packaged chip of the above embodiment.

[0159] In a fourth aspect, an embodiment of the present application discloses a computer-readable storage medium, and a computer program is stored in the computer-readable storage medium, wherein when the computer program is loaded by a processor, an automatic laser solder ball welding method for a ball grid array packaged chip of the above embodiment is executed.

[0160] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for automatic laser solder ball welding of ball grid array package chips, characterized in that: include: Obtain the target coordinates of the nozzle corresponding to the nozzle welding position; Determine whether the target coordinates meet preset coordinate requirements; If the target coordinates meet the preset coordinate requirements, determining whether the nozzle welding height needs to be calculated; If the nozzle welding height needs to be calculated, the nozzle welding height is obtained, and the nozzle is lowered to the nozzle welding height; Based on the target coordinates, the solder ball is controlled to fall into the nozzle, and the laser is controlled to emit light for welding; Determine whether the welding results meet the preset welding requirements; If the welding result meets the preset welding requirement, the current welding process is terminated; Wherein, the step of obtaining the target coordinates of the nozzle corresponding to the nozzle welding position includes: Move the visual positioning camera to the visual photo taking position; Control the visual positioning camera to take pictures and calculate the target coordinates of the nozzle corresponding to the nozzle welding position; Controlling the visual positioning camera to take pictures and calculate the target coordinates of the nozzle corresponding to the nozzle welding position includes: Setting positioning parameters, and controlling the visual positioning camera to capture a standard image based on the positioning parameters; Optimizing the standard image, and creating an image template based on the standard image and a normalized cross-correlation algorithm; Controlling the visual positioning camera to capture a target image; Optimizing the target image, and searching for pad pixel coordinates based on the image template and the target image; Based on the pad pixel coordinates and a preset calibration conversion relationship, the target coordinates of the nozzle corresponding to the nozzle welding position are calculated; The determining whether the welding result meets the preset welding requirements includes: Acquire detection images; Input the detection image into a preset neural network model and output solder joint data, wherein the solder joint data includes solder leak status, tin coverage, solder ball offset degree, tin connection status and overall solder joint morphology characteristics; Determining whether the solder joint data meets corresponding data requirements; If the welding point data meets the corresponding data requirements, it is determined that the welding result meets the preset welding requirements; If the welding point data does not meet the corresponding data requirements, it is determined that the welding result does not meet the preset welding requirements; Before inputting the detection image into a preset neural network model and outputting the welding point data, the method further includes: Extracting geometric information of the edge contour of the chip reference point in the detection image based on a sub-pixel edge extraction algorithm; Based on the geometric information, positionally matching the reference point contour with the standard reference point contour and generating a matching result; Based on the matching result, calculating the position offset; Based on the position offset, the image pixel position of the pad is obtained.

2. The automatic laser solder ball welding method for ball grid array package chips according to claim 1, characterized in that: The step of controlling the solder ball to fall into the nozzle based on the target coordinates and controlling the laser to emit light for welding includes: Control the turntable to rotate and make the solder ball fall into the nozzle; Control the laser to emit light, and make the solder ball in the nozzle melt and eject; Raise the nozzle to a safe height.

3. The automatic laser solder ball welding method for ball grid array package chips according to claim 2, characterized in that: The controlling of the laser to emit light and causing the solder ball in the nozzle to melt and eject when heated comprises: Get the melting point temperature of solder ball and the real-time temperature of welding area; Obtaining a temperature difference between the melting point temperature and the real-time temperature; Based on the temperature difference and the preset control rules, the light emitting power of the laser is adjusted, and the solder ball in the nozzle is heated, melted and ejected.

4. A ball grid array package chip automatic laser solder ball welding system, used to perform any one of the methods of claims 1 to 3, characterized in that: include: A first acquisition module is used to acquire the target coordinates of the nozzle corresponding to the nozzle welding position; A first judging module, used to judge whether the target coordinates meet the preset coordinate requirements; A second judgment module, if the target coordinates meet the preset coordinate requirements, the second judgment module is used to judge whether it is necessary to calculate the nozzle welding height; A second acquisition module, if it is necessary to calculate the nozzle welding height, the second acquisition module is used to acquire the nozzle welding height based on the target coordinates, and lower the nozzle to the nozzle welding height; A first execution module is used to control the solder ball to fall into the nozzle based on the target coordinates, and control the laser to emit light for welding; The third judgment module is used to judge whether the welding result meets the preset welding requirements; The second execution module is used to end the current welding process if the welding result meets the preset welding requirement.

5. An intelligent terminal, comprising a memory and a processor, characterized in that: The memory is used to store a computer program that can be run on the processor, and when the processor loads the computer program, it executes the method according to any one of claims 1 to 3.

6. A computer-readable storage medium, wherein a computer program is stored in the computer-readable storage medium, characterized in that: When the computer program is loaded by a processor, the method according to any one of claims 1 to 3 is executed.

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