JP4660998B2 - Bonding inspection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bonding inspection apparatus, and more specifically, bonding for inspecting an internal defect of a bonded portion of a bonded product in which components are bonded on a substrate, using a transmission image obtained by irradiating the bonded portion with X-rays. It relates to an inspection device.
[0002]
[Prior art]
Conventionally, as this type of bonding inspection apparatus, for example, the presence or absence of bonding defects such as air bubbles (voids) using a transmission image obtained by irradiating X-rays to a bonded product in which an electronic component is soldered on a substrate Have been proposed (for example, Japanese Patent Application Laid-Open Nos. Hei 5-172727 and Hei 6-117828). In this apparatus, the transmission image obtained by irradiating the bonded product with X-rays is binarized to calculate the area of the dark part (defective part) from the count of dark pixels (defective pixels) and the area of the dark part. The presence or absence of a bonding defect is determined by comparing the size with a reference area serving as a determination criterion.
[0003]
[Problems to be solved by the invention]
However, in such an apparatus, the intensity distribution of X-ray irradiation is not considered.
That is, when the intensity distribution of X-ray irradiation occurs, it is recognized as a dark part (defective pixel) by the binarization process even though it is not originally a defective part, and an erroneous determination may be made.
[0004]
In addition, when such a device is used to inspect the presence or absence of a bonding defect of a bonded product having a bonding layer in which a plurality of components are bonded as a laminated structure on a substrate and two or more layers overlap, As a result, overlapping transmission images are obtained, and it becomes impossible to determine the defect of the joint portion.
[0005]
One object of the bonding inspection apparatus of the present invention is to more accurately inspect a bonding defect. Another object of the bonding inspection apparatus of the present invention is to more accurately inspect bonding defects by removing the influence of the intensity distribution of X-ray irradiation. Another object of the bonding inspection apparatus of the present invention is to more accurately inspect a bonding defect by removing the influence of overlapping of two or more bonding layers in an X-ray transmission image of a bonded product having a laminated structure. To do.
[0006]
[Means for solving the problems and their functions and effects]
In order to achieve at least a part of the above object, the bonding inspection apparatus and method of the present invention employ the following means.
[0009]
The first bonding inspection apparatus of the present invention irradiates an X-ray on an internal defect of a bonded portion of a bonded product in which a plurality of components are bonded on a substrate to form two or more bonding layers. A joint inspection apparatus for inspecting using a transmission image obtained by detecting brightness of two predetermined points separated by a determination range in the transmission image, and detecting the brightness between the detected brightness and the two predetermined points Intensity distribution calculating means for calculating the X-ray irradiation intensity distribution in the direction of the line connecting the two predetermined points based on the distance, and correcting the brightness of each unit pixel within the determination range based on the calculation result The lightness correction means calculates the lightness difference between adjacent pixels in the contour region of the overlapping region where the two or more layers of the joint layers previously set in each unit pixel within the corrected determination range overlap. Each unit pixel in the multi-layer area in the direction to cancel the brightness difference Overlapping region correction means for correcting, defective pixel setting means for setting a unit pixel exceeding the threshold value as a defective pixel when the brightness of each unit pixel within the corrected determination range exceeds a predetermined threshold value, and the setting And a defect determination means for determining the presence or absence of a defect in the bonded portion based on the area of the defective pixel.
[0010]
In the first joining inspection apparatus of the present invention, the intensity distribution calculating means detects the brightness of two predetermined points separated by the determination range in the transmission image, and the detected brightness and the distance between the two predetermined points Based on the above, the X-ray irradiation intensity distribution in the direction of the line connecting the two predetermined points is calculated, and the brightness correction means corrects the brightness of each unit pixel within the determination range based on the calculation result. Then, the multi-layer region correction means calculates the brightness difference between adjacent pixels at the contour portion of the multi-layer region where two or more preset joining layers in each unit pixel within the corrected determination range overlap. The brightness of each unit pixel in the multi-layer area is corrected in a direction to cancel the calculated brightness difference. Thereafter, when the brightness of each unit pixel within the corrected determination range exceeds a predetermined threshold, the defective pixel setting unit sets a unit pixel that exceeds this threshold as a defective pixel, and the defect determination unit sets the set defect. Based on the area of the pixel, the presence / absence of a defect in the joint portion is determined. As a result, even when a plurality of components are bonded and have a region where two or more bonding layers overlap, erroneous determination due to the intensity distribution of X-ray irradiation and erroneous determination due to having a region where bonding layers overlap. It is possible to suppress the defect of the joint portion more accurately. Here, the “unit pixel” may be one pixel, or may be a pixel in which a plurality of adjacent pixels such as two pixels or four pixels are combined.
[0011]
The second bonding inspection apparatus of the present invention is a bonding inspection for inspecting an internal defect in a bonded portion of a bonded product in which components are bonded on a substrate, using a transmission image obtained by irradiating the bonded product with X-rays. A line that detects brightness at two predetermined points separated by a determination range in the transmission image and connects the two predetermined points based on the detected brightness and a distance between the two predetermined points. Intensity distribution calculating means for calculating the X-ray irradiation intensity distribution in the direction, brightness correction means for correcting the brightness of each unit pixel in the determination range based on the result of the calculation, and within the determination range after the correction When the brightness of each unit pixel exceeds a predetermined threshold value, defective pixel setting means for setting a unit pixel exceeding the threshold value as a defective pixel, and the defect of the joint portion based on the set area of the defective pixel Defect determination means for determining presence or absence The the gist.
[0012]
In the second joining inspection apparatus of the present invention, the intensity distribution calculation means detects the brightness of two predetermined points separated by the determination range in the transmission image, and uses the detected brightness and the distance between the two predetermined points. Based on this, the X-ray irradiation intensity distribution in the direction of the line connecting the two predetermined points is calculated, and the brightness correction means corrects the brightness of each unit pixel within the determination range based on the calculation result. Then, the defective pixel setting means sets the unit pixel exceeding this threshold as a defective pixel when the brightness of each unit pixel within the corrected determination range exceeds a predetermined threshold, and the defect determination means is set to this The presence / absence of a defect in the joint portion is determined based on the area of the defective pixel. Thereby, the erroneous determination resulting from the intensity distribution of X-ray irradiation can be suppressed, and the defect in the joint portion can be inspected more accurately.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described using examples. FIG. 1 is a configuration diagram showing an outline of the configuration of a bonding inspection apparatus 20 according to an embodiment of the present invention. The joint inspection apparatus 20 according to the embodiment inspects internal defects in a joint portion of a joint product 10 in which components are joined on a substrate (for example, a joint product in which electronic components such as transistors and diodes are soldered on the substrate). It is a device for performing. As shown in FIG. 1, the bonding inspection apparatus 20 of the embodiment irradiates an X-ray transmission image by irradiating a bonded product 10 as a work conveyed by a work conveying machine 22 with X-rays. 30 and analyzing the X-ray transmission image captured by the X-ray inspection apparatus 30 to determine the presence / absence of a defect in the joint portion and to display the X-ray transmission image and the determination result, etc. And a display device 42.
[0014]
The X-ray inspection apparatus 30 is configured as, for example, a microfocus X-ray inspection apparatus, and an X-ray generator 34 that irradiates the bonded product 10 with X-rays and an X-ray generation in the housing 32 thereof. A CCD camera 36 is provided that detects X-rays irradiated by the instrument 34 and transmitted through the bonded article 10 as an X-ray transmission image through a phosphor (not shown) such as a scintillator. The housing 32 is provided with a shutter 38 for carrying the work (joined product 10) conveyed by the work conveyance machine 22 into the inside. In the embodiment, the X-ray inspection apparatus 30 irradiates with X-rays having at least two types of wavelength distributions to obtain a transmission image in order to obtain a transmission image of the solder. Components other than solder were removed, and a transmission image using only solder was extracted.
[0015]
Although not shown, the controller 40 is configured as a microprocessor centered on a CPU, and includes a ROM that stores a processing program, a RAM that temporarily stores data, and an input / output port. A command signal from an operation panel 44 that commands the operation of each device, an image signal detected by the CCD camera 36, and the like are input to the controller 40 via an input port. Further, the controller 40 outputs a control signal for controlling the operation of the X-ray generator 34 and the workpiece transfer machine 22 and a display signal to the display device 42 via an output port.
[0016]
The operation of the bonding inspection apparatus 20 of the embodiment thus configured, particularly the operation when inspecting the bonded product 10 for the presence or absence of defects using a transmission image obtained by irradiating the bonded product 10 with X-rays. explain. FIG. 2 is a flowchart illustrating an example of a bonding inspection processing routine executed by the CPU of the controller 40.
[0017]
When this bonding inspection processing routine is executed, the CPU of the controller 40 first irradiates the bonded product 10 with X-rays (step S100), and the bonded product 10 is based on the image signal detected from the CCD camera 36. Is acquired (step S102). Next, the determination range of the bonding defect in the acquired transmission image is read (step S104). The determination range is read by, for example, reading the determination range of the joint defect set by surrounding the solder portion by operating the operation panel 44 while viewing the transmission image displayed on the display device 42. It is done by. Then, noise included in the set determination range image is removed using a filter such as a median filter (step S106), and the outline of a defect (void) existing in the determination range of the transmission image from which noise is removed is extracted. The contour extraction process is performed (step S108).
[0018]
In this contour extraction process, a brightness difference with an adjacent pixel is calculated for each unit pixel (a pixel group in which one pixel or two adjacent pixels or four pixels are grouped together is set as a unit pixel) within the determination range of the transparent image. When the calculated brightness difference is equal to or greater than a predetermined threshold, the unit pixel is extracted as a contour pixel. Here, the predetermined threshold value is a threshold value for discriminating a brightness difference between adjacent pixels in a contour portion of a defect (void) and a brightness difference between adjacent pixels based on the intensity distribution of X-ray irradiation. In general, the brightness difference between adjacent pixels in the outline of a defect (void) is large, but the intensity distribution of X-ray irradiation is relatively gentle, and the brightness difference between adjacent pixels is small over the entire transmission image. Is based on becoming. A unit pixel exceeding this threshold is set to, for example, the maximum brightness as a contour pixel, and the other unit pixels are set to, for example, a value of 0, thereby setting two brightnesses. As a result, the determination range of the transmission image is a binarized image including a bright part indicating the outline and a dark part other than the bright part. Such contour extraction processing is specifically shown. For example, if the brightness of a unit pixel is f (x, y) ((x, y) represents a position coordinate in the determination range) and the brightness difference between the unit pixel and an adjacent pixel is g (x, y), The brightness difference g (x, y) can be expressed by the following equation.
[0019]
g (x, y) = | f (x, y) −f (x + 1, y) | (1)
[0020]
At this time, when the threshold value is Aref, when the brightness difference g (x, y) exceeds the threshold value Aref, the maximum value is set as the brightness f (x, y), and the brightness difference g (x, y) is set to the threshold value Aref. In the following cases, the value 0 is set as the brightness f (x, y), so that the outline of the defective portion is extracted while removing the influence of the intensity distribution of the X-ray irradiation.
[0021]
When contour extraction is performed in this way, by tracing each contour pixel by contour tracking, the region surrounded by the contour pixel is specified, and all unit pixels in this region have the same brightness (in the embodiment, By setting the maximum brightness, the area surrounded by the contour pixels is filled (step S110). By this filling, all the unit pixels in the area surrounded by the contour pixels are set as defective pixels. Then, the area of the filled region, that is, the number of unit pixels set to the maximum brightness is measured, and the ratio (void ratio) of the number of defective pixels to the total number of unit pixels in the determination range read in step S104 is calculated. Then (step S112), defect determination processing is performed (step S114). This process is a process for determining the presence or absence of a bonding defect by determining whether or not the void ratio exceeds a predetermined threshold, and this threshold is set to an appropriate value based on the required bonding accuracy. Is done. In this defect determination, a method of determining a bonding defect when the number of defective pixels exceeds a preset reference number of defective pixels can be adopted without calculating the void ratio.
[0022]
When the defect determination process is thus performed, the determination result is output to the display device 42 (step S116), and this routine is terminated. Thereby, the operator can know whether or not there is a defect in the joint portion of the joint article 10.
[0023]
According to the bonding inspection apparatus 20 of the embodiment described above, the influence of the intensity distribution of the X-ray irradiation is removed by using a threshold value that distinguishes the outline of the bonding defect portion and the X-ray intensity distribution. Defects can be inspected more accurately.
[0024]
Next, a bonding inspection apparatus 120 that is a second embodiment of the present invention will be described. The bonding inspection apparatus 120 of the second embodiment has the same configuration as the bonding inspection apparatus 20 of the embodiment except that the object (bonded product) to be inspected for defects is different and the processing in the controller 140 is different. . Accordingly, the same parts as those of the bonding inspection apparatus 20 of the embodiment are denoted by the same reference numerals and the description thereof is omitted. In the bonding inspection apparatus 120 according to the second embodiment, an internal defect of a bonded portion of a bonded product in which a plurality of components are bonded and two or more overlapping bonding layers are formed, for example, a side view of the bonded product 110 in FIG. 3A) and a front view (FIG. 3B), an element 112 such as a transistor or a diode, and a conductive heat radiating plate 114 for releasing heat generated based on the operation of the element 112. And the presence or absence of a bonding defect between the first bonding layer 118 and the second bonding layer 119 of the bonded product 110 in which the insulating substrate 116 that secures insulation between the element 112 and the heat sink 14 is bonded by solder. Consider the case. FIG. 4 is a flowchart showing an example of a bonding inspection processing routine executed by the CPU of the controller 140. The processing contents in this routine will be described below with reference to the transparent image processing process of FIG.
[0025]
First, the CPU of the controller 140 performs the same processing as steps S100 to S104 of the routine of FIG. 2, that is, the X-ray is irradiated to the bonded product 110 to acquire a transmission image, and a transmission image determination range (FIG. 5A). (The range of the second solder layer 119) is set (steps S200 to S204, FIG. 5A). Next, processing for correcting the intensity distribution of X-ray irradiation is performed (step S206, FIG. 5B). The processing for correcting the intensity distribution assumes that the X-ray irradiation intensity distribution can be regarded as a linear distribution (it can be assumed that the X-ray irradiation intensity changes linearly in a certain direction). Is a process for removing the influence of the unit image on the brightness of the transmission image. Specifically, first, two points A and B separated by the determination range are set, and the brightness of each of the points A and B is detected. Then, the brightness difference between the points A and B is calculated, and the slope of the X-ray intensity distribution is obtained based on the ratio between the distance between the points A and B (number of unit pixels) and the brightness difference between the points A and B. The X-ray irradiation intensity is obtained by subtracting the X-ray intensity distribution in the line direction of points A and B calculated on the basis of the brightness of the unit pixel column in the line direction of points A and B in the actually acquired transmission image. The influence based on distribution can be removed. Here, the positions of the points A and B are based on predictions or experiments based on the X-ray irradiation direction and the position of the joint 110 so that the X-ray intensity distribution is generated in the direction of the line connecting the points A and B. Set in advance. Further, the points A and B are set so as to be outside the region of the joining portion in the transmission image (in the embodiment, outside the region of the second solder layer 119 in FIG. 5A in the transmission image). This is because in the transmission image in which only the joint portion (solder layer) is extracted, the brightness of the pixels outside the joint portion region should all be the same value, so only the influence of the X-ray intensity distribution is taken into account. It is because it is good.
[0026]
FIG. 6 is a diagram showing the relationship between the brightness of the unit pixel column in the determination range from point A to point B and the influence of the X-ray intensity distribution. As shown in FIG. 6, the lightness c of each unit pixel column of the transmission image actually captured by the X-ray inspection apparatus 30 is mainly the lightness a of the original unit pixel column that is not affected by the X-ray irradiation intensity distribution. And X-ray irradiation intensity distribution (brightness) b can be expressed as (a + b). Since the brightness of the points A and B is also detected at this time, considering the case where the brightness changes linearly as the X-ray intensity distribution, the unit pixel existing between the points A and B indicates the slope of the X-ray intensity distribution b. It can be expressed as the ratio of the brightness difference between points A and B to the number of. Therefore, by subtracting (c−b) the X-ray intensity distribution b calculated based on the inclination from the lightness c of the actually captured unit pixel column, the influence of the X-ray intensity distribution is removed. The brightness a can be obtained. In this way, by performing the above processing for each unit pixel column in the transmission image determination range, it is possible to obtain an image in which the influence of the X-ray intensity distribution is removed in the entire transmission image determination range. . Note that the X-ray intensity distribution may be calculated for each unit pixel column in the determination range, or the X-ray intensity distribution calculated in a certain unit pixel column may be applied to another unit pixel column. .
[0027]
When the influence of the X-ray intensity distribution is removed in this way, the correction of the element shadow portion, that is, the overlapping region where the plurality of bonding layers overlap (in the embodiment, the first solder layer 118 positioned on the second solder layer 119) is performed. Is corrected (step S208, FIG. 5C). This process is a process of removing the brightness of each unit pixel in the overlapping area where a plurality of bonding layers overlap as a value indicating a dark pixel. Specifically, this correction processing is performed by pattern matching processing. FIG. 7 is a diagram illustrating the relationship between the brightness of the unit pixel column within the determination range of the transparent image and the influence of the multi-layer area. As shown in FIG. 7, a multi-layer region is set in advance at the brightness a of the unit pixel column from which the X-ray intensity distribution has been removed, and adjacent pixels in the contour part (points C and D in FIG. 7) of this region. Is calculated, and a correction coefficient for canceling the brightness difference is calculated. Then, by adding a correction coefficient to the brightness of all unit pixels in the multi-layer area (the broken line portion in FIG. 7), the brightness of each unit pixel in the multi-layer area can be matched with the brightness of surrounding pixels. Can be removed.
[0028]
Thereafter, noise included in the transmission image determination range is removed using a filter such as a median filter (step S210), and the bright pixel and the dark pixel are divided for each unit pixel in the transmission image determination range. A value process is performed (step S212). This process is a process of setting, for example, the maximum brightness as a defective pixel when the brightness of the unit pixel exceeds a predetermined threshold, and setting the other unit pixels as, for example, a value 0, for example, as normal pixels. Thereby, the binarized image which distinguished the defective pixel and the normal pixel can be obtained. When the binarization process is performed, the number of defective pixels (the number of pixels having the maximum brightness) is measured, and the ratio (void ratio) of the number of defective pixels to the total number of unit pixels in the determination range is calculated (step S214). A determination process is performed (step S216). This process is a process for determining the presence or absence of a bonding defect by determining whether or not the void ratio exceeds a predetermined threshold, and the specific value of this threshold is based on the required bonding accuracy and the like. An appropriate value is set. In this defect determination, a method of determining a bonding defect when the number of defective pixels exceeds a preset reference number of defective pixels can be adopted without calculating the void ratio.
[0029]
When the defect determination process is thus performed, the determination result is output to the display device 42 (step S218), and this routine is terminated. Thereby, the operator can know whether or not there is a defect in the bonded portion of the bonded product 110.
[0030]
According to the bonding inspection apparatus 20 of the second embodiment described above, X-ray irradiation is performed even when a multi-layered region where two or more bonding layers in which a plurality of components are bonded is formed as the bonded product 110. Since the influence of the strength distribution and the weight region is removed, the defect inspection of the joint portion can be performed more accurately.
[0031]
In the bonding inspection apparatus 120 according to the second embodiment, a case where a multilayer region where two or more layers in which a plurality of components are bonded is formed as the bonded product 110 is considered, but the multilayer region is not formed 1 The present invention can also be applied to a joined product of a joining layer. At this time, since only the influence of the X-ray irradiation intensity distribution has to be taken into consideration, the correction process for the multi-layer region is unnecessary.
[0032]
In the joint inspection apparatuses 20 and 120 of the first and second embodiments, solder joint defects are inspected, but joint defects of joints joined by joint materials other than solder (for example, conductive paste). It can also be applied to other inspections.
[0033]
The embodiments of the present invention have been described using the embodiments. However, the present invention is not limited to these embodiments and can be implemented in various forms without departing from the gist of the present invention. Of course you get.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an outline of a configuration of a bonding inspection apparatus 20 according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating an example of a bonding inspection processing routine executed by a controller 40 of the bonding inspection apparatus 20 according to the embodiment.
FIG. 3 is a diagram illustrating a bonded product 110;
FIG. 4 is a flowchart illustrating an example of a bonding inspection processing routine executed by a controller 140 of the bonding inspection apparatus 120 according to the embodiment.
FIG. 5 is an explanatory diagram illustrating a process of processing a transmission image of a bonded product.
FIG. 6 is a diagram showing a relationship between brightness of a unit pixel column within a transmission image determination range and an X-ray intensity distribution;
FIG. 7 is a diagram illustrating a relationship between the brightness of a unit pixel row within a transmission image determination range and the influence of a multi-layer region.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Joined goods, 20 Joined inspection apparatus, 22 Work conveyance machine, 30 X-ray inspection apparatus, 32 Case, 34 X-ray generator, 36 CCD camera, 40 Controller, 42 Display apparatus, 44 Operation panel, 110 Joined article, 112 Element, 114 heat sink, 116 insulating substrate, 118 first solder layer, 119 second solder layer.

Claims (2)

Bonding in which a plurality of components are bonded on a substrate to inspect internal defects in a bonded portion of a bonded product formed of two or more layers using a transmission image obtained by irradiating the bonded product with X-rays An inspection device,
X of the direction of the line connecting the two predetermined points is detected based on the detected lightness and the distance between the two predetermined points, by detecting the brightness of the two predetermined points separated by the determination range in the transmission image. Intensity distribution calculating means for calculating the irradiation intensity distribution of the beam,
Brightness correction means for correcting the brightness of each unit pixel within the determination range based on the result of the calculation;
Calculate the brightness difference between adjacent pixels at the contour region of the overlap region where the two or more layers of the joint layers set in advance in each unit pixel within the corrected determination range, and cancel the calculated brightness difference Multi-layer region correction means for correcting each unit pixel in the multi-layer region in the direction;
A defective pixel setting means for setting a unit pixel exceeding the threshold as a defective pixel when the brightness of each unit pixel within the determination range after the correction exceeds a predetermined threshold;
Defect determining means for determining the presence or absence of a defect in the joint portion based on the set area of the defective pixel;
A joining inspection apparatus comprising: A bonding inspection apparatus for inspecting an internal defect of a bonded portion of a bonded product in which components are bonded on a substrate using a transmission image obtained by irradiating the bonded product with X-rays,
X-rays in the direction of a line connecting the two predetermined points based on the detected lightness and the distance between the two predetermined points are detected based on the detected lightness and the distance between the two predetermined points. Intensity distribution calculating means for calculating the irradiation intensity distribution;
Brightness correction means for correcting the brightness of each unit pixel within the determination range based on the result of the calculation;
Defective pixel setting means for setting a unit pixel exceeding the threshold as a defective pixel when the brightness of each unit pixel within the determination range after the correction exceeds a predetermined threshold;
Defect determining means for determining the presence or absence of a defect in the joint portion based on the set area of the defective pixel;
A joining inspection apparatus comprising:

Images