JP2013221861A - Inspection method of wetted state of solder, automatic appearance inspection device and substrate inspection system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate a wetted state of solder at a soldered part including a part whose appearance is hard to be measured.SOLUTION: After a solder printing step, after amounts of cream solder applied to the respective lands are measured, an inspection by an inspection device 30 after reflow is executed to a substrate to which a component mounting step and a reflow step are executed. In the inspection device 30, imaging with a camera 302 at a state of performing front view of a substrate surface of an inspection object is performed under illumination by an illumination device 305, and for a soldered part which has features which do not appear in a generated image, and where the cream solder measured for the corresponding land satisfies predetermined successful conditions, features which appear in the image, and relevant to the shape of a part which does not appear in the image of the soldered part are measured, and quality of wetting of the solder at the soldered part is determined based on a result of this measurement.

Description

  The present invention relates to a method for inspecting the wet-up state of a solder fillet formed at a component mounting position on a component mounting substrate, and an automatic visual inspection apparatus and a substrate inspection system to which this method is applied.

  Many of inspections for component mounting boards are performed as appearance inspections accompanied by photographing by a camera. A conventional general automatic visual inspection apparatus includes a camera set in a state in which the optical axis is aligned with the vertical direction and the substrate surface is viewed in front, above the stage portion that supports the substrate, and each camera has a field of view in each direction. And an illuminating device for irradiating light, and an image is generated by specularly reflected light from a soldered portion with respect to the illumination light.

  As this type of automatic appearance inspection device, multiple types of color light are irradiated from different directions of elevation with respect to the substrate, respectively, and the suitability of the solder fillet tilt state is determined based on the color distribution pattern that appears at the soldering site in the image There is an inspection device of a type that performs (see, for example, Patent Document 1).

  In addition, an inspection apparatus configured to image a solder fillet from an oblique direction has been proposed. For example, in Patent Document 2, as the soldering part is imaged from obliquely upward while illuminating the soldering part of the lead component, one inspection target part is imaged from a plurality of directions, and is generated by each imaging. It is described that the quality of soldering is determined by a method of comparing the pattern of the bright area in the image with the corresponding threshold value.

  Also, in recent years, an inspection device has been provided for each of the series of processes performed for the production of substrates, and the results of measurements performed during the inspection in the previous process have been used in the subsequent process inspection. Inspection systems have been developed. As an example of such a system, Patent Document 3 has a configuration in which an inspection apparatus having a three-dimensional measurement function is provided in each of the solder printing process, the component mounting process, and the reflow process, and communication between the inspection apparatuses is possible. An improved system is disclosed. Further, Patent Document 3 captures measurement data derived at the time of the inspection of the immediately preceding process in each inspection apparatus, and uses this measurement data to indicate the parts and changes added in the process of the own apparatus. It is described that the amount of change in height at a generated site is obtained and an inspection is performed by a method of comparing this amount of change with a reference value.

  Specifically, in the inspection after component mounting described in Patent Document 3, the height of the cream solder is measured, and the height data of the cream solder measured by the inspection device of the solder printing process is acquired. By determining the amount of change in the cream solder height from the measured data, it is determined whether or not the amount of push-in during component mounting is appropriate. In addition, in the inspection device after solder printing, the height of the component is measured, the height data of the component measured by the inspection device in the component mounting process is acquired, and the amount of change in the height of the component from both measurement data Is determined to determine whether or not a floating defect has occurred in the part.

Japanese Patent No. 3599023 JP 2004-151010 A JP 2007-78533 A

  In an inspection apparatus that takes an image of the substrate surface when viewed from the front, if the inclination angle of the solder fillet becomes steep, it becomes difficult to form regular reflection light from the fillet on the imaging surface of the camera. The corresponding part becomes a dark area. In particular, since the fillet becomes very steep at the soldered portion with respect to the extremely small land, most of the fillet in the image becomes a dark region, and it is difficult to determine the wet-up state.

  On the other hand, according to the method of imaging the fillet from the oblique direction as described in Patent Document 2, it seems that the vicinity of the end point of wetting up can be imaged regardless of the state of inclination. However, in the actual image, it is difficult to distinguish the boundary between the side surface of the component and the fillet, and the solder wet-up position cannot be easily identified in many cases. In addition, since recent PCBs have a high mounting density, there are some parts that are difficult to capture due to the shadows of other parts, such as being hidden by the shadows of other parts, and all parts are imaged from a direction suitable for fillet measurement. It is impossible to do.

  In addition, in lead parts, the back fillet being sufficiently wet is an important point for determining the quality of soldering, but the back fillet is hidden by the part electrode and front fillet, so imaging is difficult. The characteristics cannot be measured directly.

  This invention pays attention to said problem, and makes it a subject to enable it to discriminate | determine the wet-up state of the solder in the soldering site | part containing the location where it is difficult to measure an external appearance.

  An inspection method according to the present invention includes an automatic appearance inspection apparatus having an imaging unit disposed above a board in a state in which the board surface of the component mounting board is viewed in front, and an illumination unit that illuminates an imaging target area of the imaging unit. It is used to inspect the solder wetting state on the substrate. In this method, the amount of cream solder applied to the land on the board in the solder printing process in a series of processes performed for the production of the component mounting board in advance is set before the parts are mounted. Measure for each land. Then, in the automatic appearance inspection device, the soldering part has a feature that does not appear in the image generated by the imaging unit, and the amount of cream solder measured for the corresponding land satisfies a predetermined favorable condition. On the other hand, the following measurement step and determination step are executed.

  In the measurement step, a feature that appears in the image generated by the imaging unit and that is related to the shape of a portion that does not appear in the image in the soldered region to be inspected is measured. In the determination step, the quality of the solder wet-up at a soldering site having a feature that does not appear in the image is determined based on the measurement result obtained in the measurement step.

  According to the above method, the amount of cream solder before the solder fillet is formed is good, but even if some reason causes solder wetting failure, and the defect cannot be confirmed directly from the image, It becomes possible to detect a defect using features of other parts appearing in the image.

  Specifically, when the above method is applied to a soldering part for a part having an electrode on a side surface, such as a chip part, a measured value of the amount of cream solder in a corresponding land is predetermined. The above steps are executed for the soldered portion exceeding the reference value. In the measurement step in this case, the height of the target component is measured. In the determination step, if the difference between the measured height of the part obtained in the measurement step and the reference height registered for the part does not exceed a predetermined allowable value, the soldering site to be inspected is checked. When it is determined that the solder wetting is good and the difference in height exceeds the allowable value, it is determined that the solder wetting at the soldering site to be inspected is defective.

  In the above description, the difference between the measured value of the height of the component and the reference height is a parameter representing the floating of the component. When the cream solder is melted in the reflow process, the component floats when the melted solder flows into the lower part of the component. However, when the amount of inflow increases, the amount of solder connecting the component electrode and the land decreases. As a result, the solder wet-up state also deteriorates.

  In the present invention, according to this phenomenon, when the amount of cream solder exceeds the reference value and the amount of float of the component does not exceed the allowable value, it is determined that the solder wet-up is good, and the amount of cream solder is If it exceeds the reference value, but the amount of float of the component exceeds the allowable value, it is determined that the solder wetting is defective.

  According to this method, even if the soldering site to be inspected is a dark region, the darkness is caused by the steep slope of the fillet or the fillet shape is defective. Can be correctly identified.

  In the automatic appearance inspection apparatus, an input step of inputting a measured value of the amount of cream solder in the land corresponding to the soldering site to be inspected may be executed prior to the determination step. In this case, in the determination step, the accuracy of the determination can be increased by changing the value of the allowable value according to the measurement value input in the input step.

  Next, when the above method is applied to the soldering part for each electrode of the lead component mounted on the board, the soldering with the measured value of the amount of cream solder exceeding the predetermined reference value The above steps are executed for the part. In this measurement step, the image of the front fillet at the soldering site to be inspected is processed to measure the amount of solder forming the front fret. Further, in the determination step, when the measurement value obtained in the measurement step is included in a predetermined standard range, it is determined that the solder wet-up at the soldering portion to be inspected is good, and the measurement value is the reference value. If it is not included in the range, it is determined that the solder wetting at the soldering site to be inspected is defective.

  In the conventional appearance inspection for lead parts, only the front fillet is the object of measurement, but even if the front fillet is well formed and the amount of cream solder applied to the land is appropriate, most of it is on the front side of the electrode If it is biased and hardened, the back fillet becomes defective. On the other hand, when the majority of the cream solder is biased toward the back side of the electrode and hardens, the front fillet becomes defective.

  In the present invention, according to these phenomena, the amount of cream solder exceeds the reference value, but if the amount of solder forming the front fillet exceeds or falls below the reference range, solder wetting is poor. It is determined that In this way, it is possible to make a determination taking into account the state of the back fillet that is difficult to confirm from the image, and the accuracy of the inspection can be increased.

  Even in the inspection for lead parts, an input step for inputting the measured value of the amount of cream solder in the land corresponding to the soldering part to be inspected from the outside is executed prior to the determination step. The reference range can be changed according to the input measurement value. In this way, it is possible to improve the accuracy of the determination by changing the determination criterion for acceptability according to the amount of solder applied to the land.

The amount of cream solder can be measured, for example, in an inspection apparatus that inspects the printed state of solder. However, the present invention is not limited to this, and in the component mounting process, before the component is mounted on the substrate introduced into the process. In addition, cream solder may be measured.
In addition, as a method of measuring the amount of cream solder, for example, the height of cream solder applied to the land using a light cutting method or phase shift method is obtained, and the volume of the cream solder is obtained by a method of accumulating the height. be able to. However, the present invention is not limited to this, cream cream solder is detected by a method of detecting a cream solder application area by binarizing an image and multiplying the area (number of pixels) of the detected area by the thickness of the mask used for solder printing. You may obtain | require the numerical value showing the volume of. Further, the area of the solder application region may be used as a parameter indicating the amount of solder.
Even in the measurement step in the automatic visual inspection apparatus, the three-dimensional data of the measurement target part can be obtained by the phase difference shift method or the stereo measurement, but the measurement method is not limited to the three-dimensional measurement.

An automatic visual inspection apparatus according to the present invention is generated by an imaging unit disposed above a substrate surface of the component mounting board in a front view, an illumination unit that illuminates an imaging region by the imaging unit, and an imaging unit. And a processing unit for inspecting the wet-up state of the solder on the board using the obtained image.
In the processing unit, for a soldering part having a feature that does not appear in the image generated by the imaging unit, a feature that appears in the image and that does not appear in the image in the soldering part Measurement means for measuring features related to the shape, and determination means for determining whether solder wetting is good or bad at a soldering portion having a characteristic that does not appear in the image, using measurement data obtained by processing of the measurement means; Output means for outputting inspection result information based on the result of the determination.

  With the above configuration, it is possible to provide an automatic visual inspection apparatus that satisfies the requirements for executing the above-described inspection method. According to this apparatus, it is possible to determine the quality of the solder wetting state, including the determination of a location where no feature appears in the image, and the accuracy of the inspection is greatly improved.

  In one embodiment of the automatic appearance inspection apparatus, information indicating the measurement value of cream solder applied to the land corresponding to the soldering site to be inspected or the result of determining the suitability of the measurement value is input from the outside. Input means are provided. Further, the determination means determines whether or not the amount of cream solder measured for the land corresponding to the soldering site to be inspected satisfies a predetermined good condition based on the information input from the input means. On the other hand, when it is determined that the condition is satisfied, determination using the measurement data is performed. When it is determined that the condition is not satisfied, it is determined that the solder wet-up at the soldering portion to be inspected is defective.

  According to the above embodiment, even if the production line is moved without removing the substrate having lands with an unfavorable amount of cream solder applied in the previous step, the soldering site for the land with an unfavorable amount of application is regarded as defective. It becomes possible to judge.

  The board inspection system according to the present invention is provided in a solder printing process in a series of processes carried out for the production of a component mounting board, and inspects the application state of cream solder on each land of the board after solder printing. And a second automatic visual inspection device that is provided in a reflow step in a series of steps and inspects the solder wet state of the component mounting board that has undergone the reflow step. . Each automatic appearance inspection apparatus is generated by an imaging unit disposed above the substrate in a state where the substrate surface of the substrate to be inspected is viewed in front, an illumination unit that illuminates an imaging target region of the imaging unit, and an imaging unit. And a processing unit that executes an inspection using the obtained image.

  The processing unit of the first automatic visual inspection apparatus compares the measured amount of cream solder with a reference value registered in advance by measuring means for measuring the amount of cream solder applied to the land to be inspected. A determination unit that determines whether the amount is appropriate; and an output unit that outputs inspection result information based on a result of the determination.

  The processing unit of the second automatic visual inspection apparatus uses the first automatic visual inspection apparatus or the first automatic visual inspection apparatus as a result of the inspection result information for the land corresponding to the soldering part having the feature that does not appear in the image generated by the imaging unit. An input unit that is input by communication with an apparatus that has received an output from the output unit of the automatic visual inspection apparatus, and a feature that appears in the image with respect to a soldered part that has a feature that does not appear in the image, A measuring means for measuring a feature related to the shape of a part not appearing in the image in the soldering part, and a land corresponding to the soldering part having a characteristic not appearing in the image based on the information input by the input means. It is determined whether or not the amount of cream solder measured satisfies a predetermined good condition, and the determination result and measurement data obtained by measurement by the measuring means are There comprising determination means for determining acceptability of wetting of the solder in the soldering portion having a characteristic that does not appear in the image, and output means for outputting the inspection result information based on the result of the determination.

  In the above system, the second automatic visual inspection apparatus receives the result of the inspection performed by the first automatic visual inspection apparatus or the measurement data on the land corresponding to the soldering part having the feature that does not appear in the image. Based on the input information, it is possible to determine whether or not the amount of cream solder in the land satisfies a favorable condition. Here, when it is determined that the amount of cream solder satisfies a favorable condition, it is possible to determine whether the solder wet-up is good or not based on measurement data obtained by measurement by the measurement unit. On the other hand, when it is determined that the amount of cream solder is not good by measurement by the measuring means, it may be determined that the solder wet-up state is defective based on the determination.

  According to the present invention, the solder wetting state is accurately detected even for a soldered part including a part that cannot be directly measured because it appears as a dark region in an image or imaging is difficult. The accuracy of inspection to improve can be improved.

It is explanatory drawing which shows the structure of a board | substrate inspection system corresponding to the whole structure of the production line of a component mounting board | substrate. It is a block diagram which shows the structure of a solder printing inspection apparatus. It is a block diagram which shows the structure of the inspection apparatus after reflow. It is a figure which shows the influence which the difference in the width of a land has on the shape of a fillet and the reflection direction of illumination light. It is a flowchart which shows the procedure of the quality determination of a fillet. It is a figure which shows typically the case classified by the determination process of FIG. FIG. 6 is a diagram illustrating a case where the determination criterion of FIG. 5 is not applied. It is a flowchart which shows the whole procedure of the inspection after reflow. It is a figure which shows typically the relationship between the quantity of cream solder, and the allowable value of the floating amount of components. It is a graph which shows the relationship between the quantity of cream solder, and the allowable value of the floating amount of components. It is a figure which shows typically the example of the quality of a fillet in a lead component, and a defect. It is a flowchart which shows the procedure which determines the quality of the fillet in a lead component.

FIG. 1 shows the configuration of an embodiment of a board inspection system in association with the overall configuration of a production line for component-mounted boards.
The production line of this embodiment includes a solder printing process, a component mounting process, and a reflow process. The solder printing process includes a solder printing apparatus 11 that applies cream solder to each land on the substrate and a solder printing inspection apparatus 10 that inspects the application state of the cream solder. In the component mounting process, a mounter 21 that mounts components on a board after solder printing and a mounting inspection device 20 that inspects the mounting state of the components are provided. In the reflow process, there are provided a reflow furnace 31 for melting the cream solder on the substrate after mounting the components, and a post-reflow inspection device 30 for inspecting the solder fillet and components on the substrate after the reflow.

The inspection apparatuses 10, 20, and 30 are all automatic appearance inspection apparatuses and are connected to each other via the LAN line 100.
Further, a server 40 for data management is connected to the LAN line 100. The server 40 stores inspection reference data and inspection result information used for inspections by the inspection apparatuses 10, 20, and 30. The inspection reference data includes a program necessary for the inspection, a reference value for determination, and the like, and the inspection result information includes measurement data obtained by the measurement processing for the inspection target portion and a determination result of pass / fail.

Each inspection apparatus 10, 20 and 30 reads necessary inspection reference data from the server 40, generates an inspection program for the board to be inspected, images the board based on this program, and handles each part Measurement and determination are performed for each range to be performed. The inspection result information obtained by these processes is associated with the board and component identification information, collected, transmitted to the server 40, and stored in the memory.
Moreover, the inspection result information in the solder printing inspection apparatus 10 can be read for each land. The result of the fillet inspection and the measurement data in the post-reflow inspection apparatus 30 are also set to be readable for each individual electrode.

In this embodiment, using the inspection result information of the above configuration, in the fillet inspection in the post-reflow inspection apparatus 30, the inspection by the inspection performed by the solder printing inspection apparatus 10 on the land corresponding to the soldered portion to be inspected is performed. Result information is acquired, and this inspection result information is used as one of the determination targets. In this embodiment, the post-reflow inspection device 30 accesses the data management server 40 to acquire the inspection result information of the land to be processed. However, the present invention is not limited to this, and communication with the solder print inspection device 10 is performed. Thus, necessary test result information may be acquired.
Hereinafter, the configuration of the apparatus and the contents of the processing relating to this inspection will be described in order.

FIG. 2 shows the configuration of the solder print inspection apparatus 10.
A solder print inspection apparatus 10 of this embodiment includes a stage unit 101 that supports a substrate to be inspected, a camera 102 and a projector 103, an inspection head 104 that supports these above the stage unit 101, and a processing unit 100. . The stage unit 101 is provided with a moving mechanism (not shown) that moves the stage main body along one axis (for example, an axis along the horizontal direction in FIG. 2). The inspection head 104 is provided with a moving mechanism (not shown) that moves the head main body along the axis orthogonal to the moving axis of the stage unit 101 together with the camera 102 and the projector 103. Although not shown in FIG. 2, an illumination unit that illuminates the imaging target area of the camera 102 is also attached to the inspection head 104.

  The processing unit 100 performs processing such as measurement, determination, and output of results in addition to the control of the movement mechanism and the optical system, and includes a CPU 110, a memory 111, an inspection head control unit 112, and an imaging processing unit 113. , Projector control unit 114, stage control unit 115, measurement processing unit 116, inspection execution unit 117, inspection data storage unit 118, communication interface 119, operation unit 120, display unit 121, and the like.

  The CPU 110 controls the movement of the inspection head 104 and the stage unit 101 via the inspection head control unit 112 and the stage control unit 115, and causes the camera 102 to capture an image via the imaging processing unit 113, and causes the projector control unit 114 to operate. Via the projector 103. The imaging processing unit 113 is also provided with a function of taking an image generated by the camera 102 and digitally converting it.

The memory 111 stores a program related to the above control, and also stores image data generated by digital conversion of the imaging processing unit 113, a projection image to be projected by the projector 103, and the like.
The measurement processing unit 116 and the inspection execution unit 117 are programmable logic devices, and execute measurement and determination processing in cooperation with the CPU 110.

  In the solder printing inspection apparatus 10 having the above-described configuration, a striped pattern image that periodically varies from the projector 103 is projected onto the land on the substrate based on the principle of the phase shift method, and every time the pattern image changes. Take an image. The measurement processing unit 116 detects, for each pixel, a change in luminance that has occurred in the image during one cycle of projection processing, and calculates the height of a point indicated by the pixel based on the phase of the change.

  Furthermore, the measurement processing unit 116 regards pixels whose calculated height exceeds a predetermined value as indicating cream solder, and accumulates the heights of these pixels to thereby calculate the cream solder on the land. Determine the volume. The inspection execution unit 117 compares the above volume with a reference value registered in advance, and determines that the amount of cream solder applied is good if the volume is equal to or greater than the reference value, and the volume does not satisfy the reference value. In this case, it is determined that the amount of cream solder applied is poor.

  The CPU 110 collects the determination result and the measured value of the solder volume used for the determination into inspection result information according to the above-described data configuration, and stores it in the inspection data storage unit 118. Further, every time the inspection for one board is completed, information stored for the board is collected and transmitted to the server 40 via the communication interface 119.

FIG. 3 shows the configuration of the post-reflow inspection apparatus 30.
The post-reflow inspection apparatus 30 also includes a substrate stage 301, a camera 302, a projector 303, an inspection head 304, and a processing unit 300. Since the processing unit 300 has the same configuration as that of the processing unit 100 of the solder print inspection apparatus 10 in FIG. 2, each component is denoted by a symbol that matches the corresponding two digits of the solder print inspection apparatus 10. (For example, CPU 310 with respect to CPU 110), and the description thereof is omitted.

The post-reflow inspection device 30 is provided with a dome-shaped illumination device 305 as an illumination unit as a configuration that the solder print inspection device 10 does not have. An illumination control unit 322 for controlling the light emission operation of the illumination device 305 is also provided in the processing unit 300.
The illumination device 305 is also attached to the inspection head 304 but is supported at a position lower than the camera 302 and the projector 303. Window portions 305a and 305b for imaging and projection are provided at positions corresponding to the camera 302 and the projector 303 of the dome of the lighting device 305, respectively, and the LED is disposed on almost the entire inner surface of the dome excluding the window portions 305a and 305b. (Not shown) are arranged in an annular shape. The light emission colors of these LEDs are gradually changed according to changes in the azimuth angle and the incident angle, and are adjusted so as to become white light when the light of each color is diffused.

  In the post-reflow inspection apparatus 30 configured as described above, similarly to the solder printing inspection apparatus 10, imaging is performed a plurality of times in accordance with the projection of the striped pattern image from the projector 303, and images generated by the respective imaging are used. Measure height. This height measurement is performed on a range corresponding to the part, thereby restoring the three-dimensional shape of the part.

Further, the post-reflow inspection device 30 performs imaging under illumination by the illumination device 305 (hereinafter referred to as “dome illumination”), and the color of the specularly reflected light image that appears at the soldering site in the image and its color. The direction of the normal line of the surface indicated by the pixel in which the color is generated is specified based on the light irradiation direction corresponding to. Furthermore, by using the combination of the pixel coordinates and the normal vector that have been identified, the solder three-dimensional shape is restored, and the relationship between the three-dimensional shape and the three-dimensional shape of the component is analyzed. It is determined whether or not the electrode of the part is well wetted.
The measurement processing unit 316 includes a table in which the correspondence relationship between the feature data representing the color and the direction of the normal line calculated from the light based on the color is registered, and this table is obtained based on the feature data detected from the image. By referring to, it is possible to quickly specify the direction of the normal.

  However, since the camera 302 of the post-reflow inspection apparatus 30 is arranged so as to image the board from almost directly above, when the solder fillet has a steep inclination, the specularly reflected light from the fillet enters the camera. It becomes difficult.

FIG. 4 shows an example in which the tilt angle of the fillet and the reflection direction of the illumination light vary depending on the size of the land to be soldered, taking a chip component as an example. In FIG. 4 and FIGS. 6, 7, and 9 to be described later, only the soldered state with respect to the electrode on one side of the chip component is shown for simplification.
When soldered to a standard size land, as shown in FIG. 4 (1), the fillet becomes relatively gentle, and the illumination light from the oblique direction is reflected in the direction toward the camera 302. Can do. However, if the land to be soldered becomes narrower, the slope of the fillet becomes steep, and it becomes impossible to reflect the illumination light in the direction toward the camera 302 as shown in FIG. As a result, the portion corresponding to the fillet in the image becomes a dark region, the three-dimensional shape of the solder cannot be restored, and the accurate inspection cannot be performed.

  In view of the above problems, in the post-reflow inspection of this embodiment, for a soldering portion where the color distribution is unclear, the result of the solder printing inspection for the land corresponding to that portion is input and the device itself The amount of float of the component is calculated from the height of the component measured in step (1), and the quality of the fillet is determined by a process as shown in FIG.

  In this determination process, it is checked whether the result of the solder printing inspection is “good” or “bad” (step A). If the result is “good”, it is checked whether or not the floating amount of the component is within an allowable value (step B).

FIG. 6 shows three cases divided by the above steps A and B, taking a chip part as an example.
In each example, the state of cream solder applied to the substrate before component mounting and the state of the fillet formed by melting and solidifying the cream solder are shown side by side. Moreover, in the figure on the right hand, the range of solder wetting with respect to the component electrodes is indicated by a line with an arrow.

  In the example of FIG. 6A, an appropriate amount of cream solder is mounted on the land, and the component is also correctly mounted on the land, so that the solder is wetted up to the top of the electrode. In this case, the result of the solder printing inspection is “good”, and the amount of floating of the component is within the allowable value. Therefore, both steps A and B in FIG. 4 are “YES”, and the fillet is determined to be good. (Step C).

In the example of FIG. 6 (2), the amount of cream solder is appropriate. However, when the cream solder is melted, the part floats, and a part of the solder flows into the lower part of the part. The amount of has decreased significantly. Although the solder wets up to some extent, the upper end position of the wet-up stays up to the lower end of the component electrode because the component moves upward.
In such a case, the result of the solder print inspection is “good”, but the floating amount of the component exceeds the allowable value, so step A becomes “YES”, step B becomes “NO”, and the fillet failure is It is determined that it has occurred (step D).

  In the example of FIG. 6 (3), since the amount of cream solder applied to the land is less than the reference, a solder wet-up failure occurs. In this case, since the result of the solder printing inspection is “defective”, the step A becomes “NO”, and the process proceeds straight to the step D without checking the floating amount of the component, and the fillet defect is generated. It is determined that

  As shown in FIGS. 6 (2) and 6 (3), when the amount of cream solder is small or when the components are lifted, the solder wet-up state becomes insufficient and the fillet becomes short. However, when the land becomes narrower, the inclination of the fillet becomes steep even if the length of the fillet becomes shorter. Therefore, in the cases of FIGS. 6 (2) and (3), as in the case of FIG. 6 (1), There may be no color distribution in the fillet. Then, it is difficult to distinguish each case in FIGS. 6 (1), (2), and (3) from the image.

  On the other hand, according to the determination algorithm shown in FIG. 5, each case is distinguished by two types of parameters: the amount of cream solder applied to the land before component mounting and the amount of component floating on the substrate after reflow. Can be judged correctly.

  However, the determination processing of FIG. 5 is applied because the regular reflection light with respect to the light from the dome-shaped illumination device 305 cannot be guided to the camera 302, and thus the corresponding portion in the image is a dark region. Limited to site. The determination algorithm based on the relationship between the three-dimensional shape of the solder and the three-dimensional shape of the component described above is applied to the soldered portion where no dark region is generated. By separating the determination processing algorithm in this manner, it is possible to prevent the solder having the shape shown in FIG. 7 from being determined to be good.

In the case of FIG. 7, the solder amount of cream solder is an appropriate amount, and the parts are not lifted. However, for some reason (for example, the temperature of the reflow furnace is low), the solder does not get wet and becomes a ball. ing. When the determination process of FIG. 5 is applied to the solder having such a shape, it is determined that the fillet is good. However, the solder in the example of FIG. 7 has a gentle slope, and specularly reflected light with respect to the illumination light is guided to the camera 302, and color distribution due to the illumination light occurs at corresponding locations in the image under dome illumination. The determination process can be excluded.
Therefore, it is possible to correctly determine that the shape of the fillet is defective based on the three-dimensional shape restored from the color distribution.

FIG. 8 shows a specific procedure of the inspection executed in the post-reflow inspection device 30.
This process is started in response to the completion of the alignment with the inspection head 304 after the substrate to be inspected is carried into the stage unit 301. First, in step S1, in order to obtain an image for measuring the height of a component, imaging under the projection of a pattern image by the projector 303 is executed a predetermined number of times. In step S2, imaging under dome illumination is executed to obtain a measurement image for solder.

  A plurality of images obtained by the imaging in steps S <b> 1 and S <b> 2 are stored in the memory 311. Since each imaging is performed in a state where the camera 302 is positioned at a specific place, all the positions and arrangement relationships of the parts included in these images are matched.

Hereinafter, the following processing is executed for each component, paying attention to the components included in the image in order.
First, an inspection window is set for the focused component (step S3). Although the window to be set differs depending on the type of the part, generally, a part window including a part main body and a land window for each soldering part are set. These windows are also set in common for the plurality of images described above.

  In step S4, height measurement using image data generated under the projection of a striped pattern image is performed for each pixel in the component window. Further, the three-dimensional shape of the part is restored by combining the coordinates of the pixel whose height is equal to or greater than a predetermined value and the calculated height.

  In step S5, a dark region in the land window set for the component under attention is detected for an image under dome illumination. In step S6, the ratio of the dark area in each land window is obtained and compared with a predetermined threshold value. Here, if there is even one land window whose dark area ratio exceeds the threshold value, steps S7, S8, and S9 are executed.

  In step S7, the inspection result of the solder print inspection for the component under attention is input from the data management server 40 or the solder print inspection apparatus 10. In step S8, the floating amount of the part is calculated based on the height data measured in step S4. Specifically, taking the average or maximum height calculated for a part as the part height, the difference between this height and the reference height registered for the part under consideration is obtained, and the difference is calculated. Is the floating amount.

  In step S9, by using the solder amount input in step S7 and the component floating amount calculated in step S8, the determination process by the method shown in FIG. 5 is executed for each land window. The quality of the fillet in each land window is determined.

  If it is determined in step S6 that the ratio of the dark area in each land window is smaller than the threshold value, steps S10 and S11 are executed for each land window.

In step S10, the three-dimensional shape of the solder is restored by referring to the table described above and replacing the color distribution in the land window with the normal distribution.
In step S11, the quality of the solder fillet is determined by analysis using the three-dimensional shape of the solder restored in step S10 and the three-dimensional shape of the part restored in step S4. For example, from the relationship between the coordinates representing the part and the coordinates representing the solder, it is determined whether or not the solder is in contact with the side of the part. Compare. If the height difference between the two is within a predetermined threshold value, the fillet is determined to be good, and if the difference is greater than the threshold value, the fillet is determined to be defective.

  As a result of repeatedly executing the above processing for each component, when the processing for all components is completed (“YES” in step S12), the determination results for each component are integrated to determine whether the board as a whole is good or bad (step S13). ). Further, in step S14, inspection result information including the result of each determination and measurement value is created, stored in the inspection data storage unit 318, and output to the data management server 40.

  According to the flowchart of FIG. 8, the process of combining the stage unit 301 and the inspection head 304 for imaging is performed once. However, if the substrate is larger than the field of view of the camera 302, steps S1 and S2 are performed. The steps S3 to S12 are repeated in accordance with the imaging cycle.

  Further, the allowable value to be compared with the floating amount of the component in step S9 (step B in FIG. 5) needs to be set in advance as a value considering the variation in the height of the component. For example, for each component type, the degree of variation in height of that type of component is obtained, and an allowable value derived from the variation may be registered as inspection reference data.

If the allowable value of the float of the component is not a constant value but is changed according to the amount (volume) of the cream solder, the determination accuracy can be further improved.
FIG. 9 schematically shows the relationship between the amount of cream solder applied and the allowable value for determining the amount of float that causes a fillet failure. As shown in this figure, when the amount of cream solder is large, the allowable value of floating can be increased to some extent. However, as the amount of cream solder decreases, the allowable value of floating needs to be decreased.

  In order to change the allowable value of floating according to the amount of cream solder, for example, a relationship between both may be specified using a plurality of samples, and a table indicating the relationship may be registered in the inspection apparatus 30 after reflow. Further, instead of inputting the result of the solder printing inspection, the volume of the cream solder measured in this inspection is input to the inspection apparatus 30 after reflow, and the allowable value is referred to the above table by the input numerical value. Find it.

  FIG. 10 is a graph in which the relationship table between the cream solder volume and the allowable value of the float of the component is replaced with a graph. P in the figure is a limit point where an allowable value can be set. When the amount of the cream solder is equal to or less than the amount indicated by this point P, a fillet defect always occurs regardless of whether or not the component is lifted.

  In FIG. 10, the allowable values derived from the samples and registered in the table are indicated by dots. If the measured value of the cream solder volume is larger than the value indicated by the point P, select the allowable value indicated by the dot at the highest position in the range smaller than the point corresponding to the measured value in the graph. What is necessary is just to compare the selected tolerance with the deviation | shift amount of components. When the amount of solder is less than or equal to P, it may be determined unconditionally that the fillet is defective without measuring the amount of component displacement.

  As described above, in this embodiment, in contrast to the soldering portion where the feature representing solder does not appear in the image under the dome illumination, the shape of the soldering portion is another feature appearing in the image. It is possible to accurately determine the solder wet-up state based on the feature (part height) related to 1 and the amount of cream solder applied to the land corresponding to the soldering site.

  Furthermore, the inspection after the reflow using the result of the solder printing inspection is not limited to the above, but can be applied to the inspection of the soldered portion of the lead component.

  In the soldering of lead parts, it is desirable to allow a suitable amount of solder to wet on both the front and back sides of the electrode. FIG. 11 (1) is an example of this desirable soldering, and FIGS. 11 (2) and (3) show examples of poor soldering.

  When an appropriate amount of cream solder is applied to the land, and the solder melted by the reflow process is well distributed between the front and back of the electrode, as shown in FIG. 11 (1), the front fillet and the back fillet are Both are well formed.

On the other hand, when the amount of cream solder applied to the lands is small, the melted solder is biased to the front side and gets wet, and the back fillet may not be well formed as shown in FIG. On the other hand, the solder concentrates on the back side of the electrode, and as shown in FIG. 11 (3), the front fillet may not be properly wetted up.
Moreover, even if the amount of cream solder is an appropriate amount, depending on the application state, the same defect as in FIG. 11 (2) or FIG. 11 (3) may occur.

  As described above, in the post-reflow inspection apparatus 30 of this embodiment, the substrate is imaged from almost directly above, so that the front fillet can be measured in the generated image, but the back fillet is almost imaged. Measurement is impossible. Therefore, in the example shown below, the front fillet height can be measured to obtain the volume of the front side solder, and based on the volume and the result of the solder print inspection, the back fillet Conduct inspections including discrimination.

FIG. 12 shows the inspection procedure for one electrode of the lead component. This procedure is also performed as the processing in step S9 in FIG.
Hereinafter, the determination of the solder wet-up state in the lead component will be described with reference to the step symbols in this flowchart.

  First, for the land corresponding to the electrode to be inspected, the inspection result of the solder printing inspection is input, and the content of the result is determined (steps S21 and S22). In this embodiment, a value obtained by adding the minimum required solder volume to the front side and the back side of the electrode of the lead component is used as a reference value for the quality determination of the solder printing inspection. Therefore, when it is determined as “defective” in the solder printing inspection (“NO” in step S22), it is apparent that the solder is insufficient, and therefore the process proceeds to step S27 without performing measurement using an image under dome illumination. Proceed to determine that the fillet is bad.

  If the result of the solder print inspection for the corresponding land is “good” (step S22 is “YES”), the process proceeds to step S23, and the image under the dome illumination is used to correspond to the illumination color in the land window. Measure the height of the location (corresponding to the front fillet) where the color to be distributed is distributed. Further, the volume of the solder forming the front fillet is calculated by calculating the total sum of the measured values at each height (step S24), and the volume is compared with a predetermined reference range (step S25).

  In the solder printing inspection, a good determination is made that the amount of cream solder applied is greater than or equal to the reference value, and the front side solder volume is included in the reference range (both steps S22 and S25 are “YES”), the front Both the fillet and the back fillet are considered to be good and are determined to be “good” (step S26). On the other hand, even if the application amount of the cream solder is equal to or greater than the reference value, if the solder is wetted to the front side, the volume of the solder on the front side increases, so the volume of the solder calculated in step S24 is increased. Beyond the standard range. On the contrary, when the solder is biased to the back side of the electrode and gets wet, the volume of the solder on the front side decreases, so that the volume of the solder falls below the reference range. In these cases, step S25 is “NO”, the process proceeds to step S27, and it is determined that the fillet is defective.

  Even in this embodiment, in step S21, instead of inputting the result of the solder printing inspection, the volume of the cream solder measured by the inspection is input, and the reference range used for the determination in step S25 is set according to the volume. You may make it fluctuate. For example, as the amount of cream solder applied increases, the upper limit value indicating the reference range is increased, and the lower limit value indicating the reference range is decreased, so that the one that does not have to be determined as defective is determined as defective. Can be prevented.

  As described above, only the processing based on the shape of the front fillet can be performed only by processing the image under the dome illumination, whereas the determination processing shown in FIG. 12 includes the determination including the determination of the state of the back fillet. It is possible to correctly determine whether soldering is good or bad.

In the above example, since it is assumed that the post-process will be performed even on a board that has been determined to be defective in the amount of solder applied in the solder printing inspection, the result of the solder printing inspection is input. However, when a board having a defective solder application amount is removed and only a board for which good judgment is made is passed to the subsequent process, it is not always necessary to input the result of the solder printing inspection. For example, in the flowchart of FIG. 8, step S7 is not performed, and the determination based on only the amount of float of the component can be performed in step S9 (that is, the determination process of step A of FIG. 5 is eliminated). Also in the determination process for the lead component shown in FIG. 12, without performing steps S21 and S22, the volume of the front-side solder forming the front fillet is obtained, and the volume of the fillet is determined by checking the volume with the reference range. Pass / fail can be determined.
However, in order to increase the accuracy of the determination, the volume of the cream solder measured by the solder printing inspection is input, and the reference value used for the determination in step S9 or step S25 may be changed according to the volume value. Good.

DESCRIPTION OF SYMBOLS 10 Solder printing inspection apparatus 11 Solder printing apparatus 20 Mounting inspection apparatus 21 Mounter 30 Post-reflow inspection apparatus 31 Reflow furnace 40 Data management server 100,300 Processing part 101,301 Stage part 102,302 Camera 103,303 Projector 104,304 Inspection Head 105, 305 Lighting device 110, 310 CPU
116,316 Measurement processing unit 117,317 Inspection execution unit 119,319 Communication interface

Claims (8)

Solder on the board using an automatic visual inspection apparatus having an imaging unit disposed above the board in a state where the board surface of the component mounting board is viewed from the front, and an illumination unit that illuminates an imaging target area of the imaging unit In the method for inspecting the wet state of
The amount of cream solder applied to the lands on the board in the solder printing process of the series of processes carried out for the production of the component mounting board is measured for each land before the parts are mounted. ,
In the automatic visual inspection apparatus,
Generated by the imaging unit for a soldered part having a characteristic that does not appear in the image generated by the imaging unit and the amount of cream solder measured for the corresponding land satisfies a predetermined good condition A measuring step for measuring a feature appearing in the image that is related to a shape of a portion that does not appear in the image in the soldered portion, and the soldering based on the measurement result obtained by the measuring step A determination step for determining whether the solder wetness in the part is good or bad,
A method for inspecting the state of solder wetting. The method of claim 1, comprising:
A soldering part for a part having a shape having an electrode on a side surface, wherein the measured value of the amount of the cream solder exceeds the predetermined reference value, and each step is executed.
In the measuring step, the height of the component is measured,
In the determination step, when the difference between the measurement value of the height of the component obtained in the measurement step and the reference height registered for the component does not exceed a predetermined allowable value, the soldered part to be inspected When the solder wetting is determined to be good and the difference in height exceeds an allowable value, the solder wetting at the soldering site to be inspected is determined to be defective. Inspection method of the rising state. The method of claim 2, wherein
In the automatic appearance inspection apparatus, an input step of inputting the measured value of the amount of cream solder in the land corresponding to the soldering part to be inspected from the outside is executed prior to the determination step,
In the determination step, the solder wet-up state inspection method, wherein the tolerance value is changed in accordance with the measurement value input in the input step. The method of claim 1, comprising:
The soldering part for each electrode of the lead component mounted on the substrate, wherein each step is performed on the soldering part where the measured value of the amount of the cream solder exceeds a predetermined reference value,
In the measurement step, an image of the front fillet at the soldered part to be inspected is processed to measure the amount of solder forming the front fillet,
In the determination step, when the measurement value obtained in the measurement step is included in a predetermined reference range, it is determined that the solder wet-up at the soldering site to be inspected is good, and the measurement value is A method for inspecting a solder wetting state, in which, if not included in a reference range, it is determined that the solder wetting at the soldering site to be inspected is defective. A method as claimed in claim 4, comprising:
In the automatic appearance inspection apparatus, an input step of inputting the measured value of the amount of cream solder in the land corresponding to the soldering part to be inspected from the outside is executed prior to the determination step,
In the determination step, the solder wet-up state inspection method in which the reference range is changed in accordance with the measurement value input in the input step. An imaging unit disposed above the board in a state in which the board surface of the component mounting board is viewed from the front, an illumination unit that illuminates an imaging target area of the imaging unit, and an image generated by the imaging unit. An apparatus including a processing unit for inspecting a solder wet-up state,
The processor is
For a soldering part having a feature that does not appear in the image generated by the imaging unit, it is related to the shape of the part that does not appear in the image in the soldering part that is a feature that appears in the image A measuring means for measuring features;
Using the measurement data obtained by the processing of the measurement means, a determination means for determining the quality of solder wetting at a soldering site having a feature that does not appear in the image generated by the imaging unit;
Output means for outputting inspection result information based on the result of the determination,
Automatic visual inspection device provided. The apparatus according to claim 6, comprising:
It further includes an input means for inputting information indicating the measurement value of the amount of cream solder applied to the land corresponding to the soldering part to be inspected or the result of determining the suitability of the measurement value from the outside,
The determination means is based on information input from the input means, and the amount of cream solder measured per land corresponding to a soldering portion having a feature that does not appear in the image generated by the imaging unit is determined in advance. It is determined whether or not a good condition is satisfied, and when it is determined that the condition is satisfied, the determination using the measurement data is performed. When it is determined that the condition is not satisfied, the solder of the soldering portion is determined. Automatic visual inspection device that determines that wetting is defective. A first automatic visual inspection device that is provided in a solder printing step of a series of steps performed for production of a component mounting board and inspects a cream solder application state on each land of the board after solder printing; A system including a second automatic visual inspection device that is provided in a reflow step in the series of steps and inspects a wet state of solder on the component mounting board that has undergone the reflow step,
Each automatic appearance inspection apparatus is generated by an imaging unit disposed above the substrate in a state where the substrate surface of the substrate to be inspected is viewed in front, an illumination unit that illuminates an imaging target region of the imaging unit, and an imaging unit. A processing unit that performs an inspection using the obtained image,
The processing unit of the first automatic visual inspection apparatus compares the amount of cream solder applied to the land to be inspected with the reference value registered in advance. Determination means for determining the suitability of the amount, and output means for outputting inspection result information based on the result of the determination,
The processing unit of the second automatic visual inspection apparatus is:
The inspection result information for the land corresponding to the soldering part having the feature that does not appear in the image generated by the imaging unit is output from the output unit of the first automatic visual inspection apparatus or the first automatic visual inspection apparatus. Input means for inputting by communication with the received device;
Measuring means for measuring a feature related to the shape of a portion that is a feature that appears in the image and that does not appear in the image, relative to a soldered portion that has a feature that does not appear in the image; ,
Based on the information input by the input means, it is determined whether or not the amount of cream solder measured for a land corresponding to a soldering part having a feature that does not appear in the image satisfies a predetermined good condition. The determination means for determining the quality of the solder wetting in the soldering portion having the characteristic that does not appear in the image using the determination result and the measurement data obtained by the measurement by the measurement means,
Output means for outputting inspection result information based on the result of the determination,
A board inspection system characterized by that.

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