JP4434417B2 - Inspection equipment for printed wiring boards - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to an inspection apparatus for inspecting through holes, wiring patterns and the like in a printed wiring board.
[0002]
[Prior art]
Conventionally, two types of inspections such as a wiring pattern inspection and a through-hole inspection are performed for inspection of a printed wiring board or the like. The wiring pattern inspection is generally performed by acquiring and inspecting acceptable data from an acceptable substrate or CAD data by a design rule method, a pattern matching method, or the like. In this case, in order to inspect the surface wiring pattern of the substrate to be inspected (hereinafter also simply referred to as a substrate), line / ring / spot illumination or the like is installed on the same side as the camera to project the wiring pattern. On the other hand, in the case of through-hole inspection, it is possible to confirm the presence or absence of foreign matter present in the through-hole by irradiating transmitted light from the opposite side of the camera and capturing an image of the transmitted light. By combining these two types, the wiring pattern inspection and the through hole inspection can be performed simultaneously. However, if the through-hole inspection is performed from only one direction, it may be difficult to determine the presence or absence of foreign matter existing deep in the through-hole from the relationship between the depth of focus of the camera and the size of the printed wiring board. For this reason, if both the front and back sides are performed simultaneously to improve the inspection speed, the transmitted light illumination interferes with the extension line of the camera installed on the back side (if a camera is installed on the back side, The camera could only be installed on one side. Therefore, only one side was inspected, and the back side surface was not inspected or turned over and the back side had to be inspected again. In the former case, the inspection accuracy is lowered, and in the latter case, the inspection time is increased.
[0003]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to provide an inspection apparatus that improves the accuracy of inspection of through-holes and shortens the inspection time in the inspection of substrate wiring patterns and through-holes.
[0004]
[Means for solving the problems and actions / effects]
  In order to solve the above problems, the printed wiring board inspection apparatus of the present invention is
  An imaging device provided coaxially in the vertical direction on both sides of the substrate to be inspected;
  A first light source that is provided on both sides of the substrate to be inspected and has corresponding half mirrors, and is incident on the opposite side of the substrate to be inspected and is incident on the imaging device;
  With
  The imaging apparatus has a mechanism for simultaneously receiving light transmitted through the through-holes from the opposite side on the opposite sides and performing inspection of the same through-holes from both sides.PremiseAnd
[0005]
As described above, the image pickup devices are installed on both sides of the substrate to be inspected, and the first light source corresponding to each image pickup device is illuminated obliquely through the half mirror, and the through-hole state is made clear by the transmitted light to receive light. It is possible to reduce the error from the accompanying real image. In addition, since the image information provided on both sides of the substrate to be inspected simultaneously captures the optical information of the same through hole on both sides, both front and back sides can be inspected at the same time, which is an inspection method with high inspection accuracy. Moreover, the inspection time is shortened compared with the inspection for each side, and a quick inspection can be performed. In this inspection apparatus, when the depth of focus of the camera is greater than the depth of the through hole, the through hole may be inspected from only one side and the wiring pattern may be inspected simultaneously on both sides. In any case, it suffices to have a mechanism capable of carrying out through-hole inspection and wiring pattern inspection simultaneously on both sides.
[0006]
  And the inspection apparatus of the printed wiring board of the present invention,
  An imaging device provided coaxially in the vertical direction on both sides of the substrate to be inspected;
  A first light source that is provided on both sides of the substrate to be inspected and has corresponding half-mirrors, and illuminates incidently toward the imaging device located on the opposite side of the substrate to be inspected;
  A second light source that is provided on the same side as the imaging device on both sides of the substrate to be inspected, and irradiates the imaging position of the imaging device from an oblique direction;
  With
  The imaging apparatus transmits through light from the through-hole by the slant illumination from the opposite side and from the surface of the substrate to be inspected on the same side.By the second light sourceReflected light is received simultaneously on both sides, and each imaging position has a mechanism that is the same position on the inspected substrate opposite to the front and back.It is characterized by.
[0007]
As described above, the through-hole state is clarified by the first light source corresponding to each imaging device provided on both sides of the substrate to be inspected, and the substrate to be inspected is irradiated by the second light source. The surface state (wiring pattern, resin surface, etc.) can also be made clear, and errors from the real image accompanying light reception can be reduced. In addition, by capturing the optical information at the same position on the opposite side of the substrate to be inspected at the same time on both sides by the imaging device, for example, the same through hole can be inspected simultaneously from the both sides, such as the pattern and resin surface, so the inspection accuracy High inspection method. Moreover, the inspection time is shortened compared with the inspection for each side, and a quick inspection can be performed. In this inspection apparatus, when the depth of focus of the camera is greater than the depth of the through hole, the through hole may be inspected from only one side and the wiring pattern may be inspected simultaneously on both sides. In any case, it suffices to have a mechanism capable of carrying out through-hole inspection and wiring pattern inspection simultaneously on both sides.
[0008]
The first light source is
The first line illumination that irradiates light in a one-dimensional manner, and the falling illumination by the first line illumination irradiates the substrate to be inspected in a substantially line shape, and in the through hole on the irradiation position, Emit the transmitted light to the opposite side,
Furthermore, the imaging apparatus has a line sensor that receives light information in a one-dimensional manner, and the line direction is the same as the line direction of the first light source, and the transmitted light from the opposite side by the line sensor. Can also be received.
[0009]
In this way, by using the first line illumination that emits one-dimensional irradiation light to the first light source, the slanted illumination by the first line illumination becomes the transmitted light of the through hole. The transmitted light can have a high degree of condensing, and sufficient illuminance can be given to the imaging device. In addition, by using a line sensor that receives light information one-dimensionally in the imaging device, the collected light information is received one-dimensionally, and the light energy emitted by the line illumination is sensed. The ratio (the ratio detected by the line sensor) increases and becomes efficient.
[0010]
Furthermore, the first light source is
The first line illumination that irradiates light in a one-dimensional manner, and the falling illumination by the first line illumination irradiates the substrate to be inspected in a substantially line shape, and in the through hole on the irradiation position, Emit the transmitted light to the opposite side,
The second light source is
Irradiate light in a one-dimensional manner, the line direction is second line illumination that is the same direction as the first line illumination, and the imaging position by the imaging device provided on the same side is irradiated in a substantially line shape. ,
Furthermore, the imaging device has a line sensor that receives light information in a one-dimensional manner, and the line direction is the same as the line direction of the first light source and the second light source. The transmitted light from the opposite side and the reflected light on the same side can be received.
[0011]
Thus, by using the second line illumination that irradiates light one-dimensionally also in the second light source, it is possible to irradiate the substrate to be inspected with light having a high concentration degree, and the reflected light has high illuminance. Become. Furthermore, the light receiving efficiency can be increased by receiving the reflected light by the line sensor.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to examples shown in the drawings.
As shown in FIG. 1, a 5000-pixel one-dimensional CCD camera 10 (hereinafter, also simply referred to as a CCD camera 10) having a line sensor is used as an imaging device, and an upper CCD camera 10a on the upper side across a substrate to be inspected. The lower CCD camera 10b is coaxially located at the lower part. The upper CCD camera 10a and the lower CCD camera 10b are opposed to each other in the sensing direction, and the imaging positions thereof are the same positions on the inspected substrate 11 (see FIG. 3) provided on the installation table 32. . The one-dimensional image captured by the one-dimensional CCD camera 10 is stored as two-dimensional data in a storage device such as a RAM inside an image processing device such as a computer, and image processing is performed. By using the one-dimensional CCD camera 10, it is possible to take a large inspection field of view, and furthermore, it is possible to efficiently enter the transmitted light that passes through the through hole in the through hole inspection. Further, by using the one-dimensional CCD camera 10, the diameter of the detected through hole does not vary due to the difference in the incident angle of light and the detection error is reduced.
[0013]
By using a telecentric lens for the one-dimensional CCD camera 10, the focal point can be deepened and the measurement accuracy can be increased. Further, the resolution of the one-dimensional CCD camera 10 is preferably set optimally depending on the size of the printed wiring board serving as the substrate to be inspected, and is set to about 5 μm to 20 μm. If the thickness exceeds 20 μm, the measurement accuracy may not be sufficiently secured. On the other hand, if the thickness is less than 5 μm, the field of view becomes too narrow. For example, the unit substrate does not fit in the field of view. The one-dimensional CCD camera 10 captures line data having a predetermined width in the X direction and has a resolution of 8.5 μm. In the CCD camera 10 of this embodiment, the line data inspection width is 34 mm. Further, the imaging apparatus is a one-dimensional CCD camera 10 having a line sensor, but is not limited thereto, and may be a two-dimensional sensor (for example, one having a two-dimensional CCD sensor).
[0014]
Hereinafter, a photographing unit that performs image photographing and the like will be described. First, the outline will be described with reference to FIGS. 3 and 4. As a second light source, halogen light pattern detection line illuminations 9a and 9b (hereinafter also simply referred to as line illuminations 9a and 9b) are used obliquely. Irradiating. The line illuminations 9a and 9b irradiate the vicinity of the image capturing position by the CCD camera 10 on the surface of the inspected substrate 11 (printed wiring board or the like) from both sides. Further, through-hole detection line illuminations 17a and 17b (hereinafter, also simply referred to as line illuminations 17a and 17b) serving as the first light source are respectively obliquely illuminated through half mirrors and transmitted to the opposite CCD cameras. Irradiating light. In this way, the second light source gives stable illuminance to the substrate portion and the wiring pattern of the inspected substrate 11 and to the through hole by the first light source.
[0015]
Next, capturing of an image on the front side of the substrate to be inspected by the upper CCD camera 10a provided at the upper portion and a light source corresponding thereto will be described. As shown in the explanatory diagram of FIG. 4, the pattern detection line illumination 9a as the light source for wiring pattern inspection causes the vicinity of the image capturing position by the upper CCD camera 10a on the surface portion of the substrate 11 (printed wiring board) to be inspected. Irradiating from both sides in a line extending in the direction, a stable illuminance is given to the substrate portion 36, the wiring pattern 37, etc. of the substrate 11 to be inspected, and a sufficient illuminance is secured in the reflected light from these elements. In addition, the condensing lens 26a is provided in the front-end | tip part of the line illumination 9a for pattern detection, and it can irradiate with high illumination intensity. Further, as a first light source, a through-hole detection line illumination 17b by halogen light or the like is installed on the back side of the board to be inspected 11 (below the board to be inspected), and the irradiation light is also installed on the back side. The half mirror 12 is irradiated. In addition, as shown in FIG. 3, it is possible to obtain high illuminance by attaching a condensing lens 26b and condensing the tip of the through-hole detection line illumination 17b. Further, a cover 27 made of glass or the like having high light transmittance is provided above and below the upper half mirror 12a to protect the half mirror and allow the optical axis to pass. The through-hole detection line illumination 17b can be moved by an adjustment screw 24b serving as a focus adjusting means, and the focal position is adjusted by moving the through-hole detection line illumination 17b closer to or away from the half mirror 12b.
[0016]
Thus, by using line illumination in various places, the illuminance can be increased and errors in the detected image can be reduced. In this embodiment, line illumination is used for the second light source for pattern detection and the first light source for through-hole detection. However, the present invention is not limited to this. For example, a two-dimensional light source may be used instead of a one-dimensional light source (line illumination, etc.), and the type and number of illuminations are various according to the substrate to be inspected. be able to. For example, since LED illumination is effective for a mirror-like shape such as solder, it can be used, or ring illumination can be used as a light source from the upper surface. As described above, it is desirable to use a light source selected according to the material, surface state, usage environment, etc. of the substrate to be inspected.
[0017]
As shown in the explanatory diagram of FIG. 4, the lower half mirror 12b is installed in a state inclined at a predetermined angle with respect to the irradiation direction of the through-hole detection line illumination 17b serving as the first light source, and the reflected light is reflected. The incident light is vertically illuminated on the inspection substrate 11. In the present embodiment, the through-hole detection line illumination 17b irradiates in the horizontal direction, and the lower half mirror 12b irradiates the reflected light vertically onto the substrate 11 to be inspected that moves horizontally by tilting 45 degrees with respect to the irradiation direction. is doing. Further, the incident illumination is transmitted through the through-hole 35 formed in the substrate 11 to be inspected, and the transmitted light is transmitted through the upper half mirror 12a provided on the opposite side. Then, the optical information by the transmitted light is received as optical information indicating the shape of the through hole 35 by the upper CCD camera 10a located on the extension line. In this way, the through-hole 35 is given sufficient illuminance by the transmitted light due to the epi-illumination, and the shape of the through-hole 35 becomes clear on the substrate, and the error in acquiring optical information is reduced. Further, the upper CCD camera 10a receives reflected light from the surface of the substrate to be inspected in addition to the light transmitted through the through hole 35, and the reflected light is recognized as an image indicating the surface state of the device to be inspected. The reflected light includes color information unique to each element such as a substrate portion 36 having a resin surface, a wiring pattern 37 plated, etc. (for example, grayscale information having a density value range unique to each element). Furthermore, since the transmitted light indicating the through-hole 35 described above also has unique color information, the shape of each element is clarified by the unique color information in the developed two-dimensional image, and the element shape, etc. Whether or not is normal is determined.
[0018]
In addition, the same configuration is used to capture an image on the back side of the substrate to be inspected by the lower CCD camera 10b provided under the substrate 11 to be inspected. At that time, the pattern detection line illumination 9b is used as the second light source that irradiates the back side surface of the substrate to be inspected, and the through hole detection line illumination 17a is used as the first light source. And incident light is vertically illuminated on the substrate 11 to be inspected. Then, the transmitted light below the substrate to be inspected due to the epi-illumination passes through the lower half mirror 12b and reaches the lower CCD camera 10b, and the lower CCD camera 10b captures the light information as image information. The light source for pattern detection uses not only the pattern detection line illumination 9b but also the epi-illumination by the lower half mirror 12b as auxiliary light. Similarly, the epi-illumination by the upper half mirror 12a is used for pattern detection on the surface side of the substrate to be inspected. It is used as an auxiliary light source. In this way, epi-illumination by a half mirror is used not only as illumination for through-hole detection but also as illumination for pattern detection, so that the use of illumination becomes efficient and sufficient illuminance for image extraction Can be secured.
[0019]
As described above, the first light source and the second light source corresponding to the CCD cameras 10 provided above and below are provided symmetrically with respect to the substrate to be inspected, and image information on the front and back sides can be taken in simultaneously. Become. Further, the CCD camera 10 is provided on the same axis, and its image acquisition position is the same position on the substrate to be inspected upside down. Therefore, since the same through-hole state can be captured simultaneously, the through-hole inspection can be performed precisely, and the inspection time can be shortened to more than half compared with the single-side inspection. Here, the reason why it is more than half here is that not only the inspection time for one side can be shortened, but also the trouble of setting the substrate to be inverted can be saved.
[0020]
In order to further shorten the inspection time, a plurality of such illumination / camera systems can be arranged. When a plurality of sets of illumination / camera systems are provided, the amount of video data that can be acquired by one sensing operation increases, and a wide range of images can be captured at one time, so the inspection time can be further shortened. In this embodiment, two sets are used as shown in FIG. 1, and the inspection range is widened and the speed can be increased. Moreover, in order to perform high-speed processing, inspection image capture and image processing / measurement are processed in parallel.
[0021]
Hereinafter, the configuration and operation of the actuator and the like in the inspection apparatus will be described. As shown in FIG. 1, the inspection apparatus has a plurality of position adjusting means for adjusting the relative positions of the substrate 11 to be inspected (see FIG. 3) and the imaging apparatus (one-dimensional CCD camera 10). The one-dimensional CCD camera 10 is fixed to a Z table 20 attached to a Z-direction stepping motor 15 (position adjusting means) so as to be movable in the Z-direction. Further, the Z-direction stepping motor 15 is moved to an X-direction stepping motor 13 ( It is fixed to the X table 16 attached to the position adjusting means) and is movable in the X direction. That is, the CCD camera 10 is moved in both XZ positive and negative directions by an XZ both stepping motor serving as a position adjusting means, and the relative position with respect to the substrate to be inspected can be adjusted. Accordingly, the focus adjustment can be performed by moving the CCD camera 10 in the Z positive / negative direction, and the inspection position in the X direction can be sequentially changed by moving in the X positive / negative direction.
[0022]
Further, as shown in FIG. 2, a pedestal 34 that is movable in the Y positive and negative directions by the Y direction stepping motor 14 (position adjusting means) is provided on the main body frame. On the pedestal 34, there is provided an installation base 32 on which the board 11 to be inspected (see FIG. 3) can be installed. The installation base 32 on which the board 11 to be inspected is installed by a driving means such as an air cylinder. After being moved in the Y direction on 34, it is pressed by a cover 30 that can be moved in the Z direction by driving means such as an air cylinder. Accordingly, the installation base 32 is fixed on the base 34 below the cover 30 and is moved integrally with the base 34 by driving by the Y-direction stepping motor 14 to move in the Y positive and negative directions. The relative positional relationship in the Y direction of the CCD camera 10) is adjusted. The cover 30, the installation base 32, and the pedestal 34 are formed by opening the installation portion of the board to be inspected 11, and the board 11 to be inspected is fixed in the vicinity of the outer edge with the surface exposed.
[0023]
FIG. 5 shows an electrical configuration of the main control unit in the inspection apparatus. The main control unit 100 includes a microprocessor including an I / O port 101 and a CPU 102, a ROM 103, and a RAM 104 connected to the I / O port 101. The ROM 103 stores a main control program 103a. In the microprocessor configured as described above, the CPU 102 calls the main control program 103a after the workpiece is mounted by the workpiece mounting mechanism 41 (the mechanism such as the movement of the installation base 32 by the driving means such as the cylinder and the fixing by the cover 30). Start control. The CPU 102 receives the program and drives the X direction stepping motor 13 and the Y direction stepping motor 14 connected to the I / O port 101 to move the CCD camera 10 relatively to the inspection start position. Then, in a state where the X position is stopped, the inspected substrate 11 is moved by the Y direction stepping motor 14, and the relative position in the Y direction is sequentially changed. Then, the CCD camera 10 sequentially captures the image at the changed position and generates two-dimensional image data including position information in both XY directions. In this inspection apparatus, the width of the line data (X direction width) captured by the CCD camera 10 is 34 mm. In general, the substrate 11 to be inspected is composed of a plurality of unit substrates, and if one side of the unit substrate is within 34 mm, the entire unit substrate can be covered by a single sensing in the Y direction. If one side exceeds 34 mm, a CCD camera with a wide inspection width is used, or sensing is performed twice by shifting the position in the X direction, and the image is synthesized later. Good. In the inspection apparatus, drive processing of the actuator and the like, image capture by the imaging / analysis unit 40, or analysis thereof can be performed in parallel processing.
[0024]
Next, a method for processing an image captured by a one-dimensional CCD camera will be described. The outline is that line data in the X direction captured at a predetermined timing by the one-dimensional CCD camera is captured as information corresponding to the Y position at the time of capture because the substrate to be inspected moves at a predetermined speed in the Y direction. The image information indicating the surface state of the substrate 11 to be inspected is converted from the one-dimensional line data to the two-dimensional data. The two-dimensional data includes pixel data having position information, color information, and the like for each of through holes, wiring patterns, substrate portions, foreign matters, and the like. I do.
[0025]
A photographing / analyzing unit 40 that performs image photographing and analysis will be described with reference to a block diagram showing an electrical configuration shown in FIG. The control unit (hereinafter also referred to as an image analysis unit) 110 includes a microprocessor having an I / O port 111 and a CPU 112, a ROM 113, and a RAM 114 connected to the I / O port 111. The ROM 113 stores an image analysis program 113a. The I / O port 111 is connected to the above-described CCD camera 10 (including a one-dimensional CCD sensor 115 and a sensor controller 116 for converting the sensor output into a one-dimensional digital image input signal) as an imaging device. ing. Further, the RAM 114 is formed with a work area 114a of the CPU 112 and a memory 114b for storing captured image data of the substrate 11 to be inspected by the CCD camera 10 (see FIG. 4 and the like). The CPU 112 receives the image analysis program 113a, performs analysis processing, and can determine whether or not the inspected substrate 11 is normal.
[0026]
In addition, as the color information for each pixel constituting the line data, for example, density information corresponding to the inspection target substrate 11 at the pixel detection position is given, and the density information for each pixel is obtained by quantizing the density information. it can. For example, if the density value is 256 gradation levels, 0 as the minimum value is dark and 255 as the maximum value is light, the hole portion has a density value of 250 or more, and the wiring pattern portion has a density value of 120. Since the density value indicated by each element is different between the front and rear and the resin part, such as a density value of 40 or less, it can be clearly distinguished by the density value. In the present embodiment, the threshold value serving as the boundary of the through hole 35 is set to the density value 200, the pixel exceeding the density value 200 is set to the through hole pixel, and the position where the through hole 35 exists in the two-dimensional image information is recognized. Clarify the shape.
[0027]
Next, an example of a measurement method in an image analysis program for determining pass / fail of a substrate to be inspected will be described. The hole center data of the through-hole that is acquired and set in advance from CAD data or non-defective product data is two-dimensionally developed using a technique such as pattern matching (a two-dimensional image of line data from the one-dimensional CCD camera 10). The image is superimposed on the developed image. Furthermore, the actual image memory is scanned in the positive and negative directions of XY (total of four directions) from the hole center, and the point of change from the through hole 35 to the inspected substrate 11 or the wiring pattern (that is, the through hole 35 peripheral portion and ). At that time, a change point that changes below the threshold value (density value 200 in this embodiment) at the end of the through hole 35 may be searched, or a pixel or wiring pattern indicating the substrate 11 to be inspected may be indicated. You may make it look for the point where a pixel appears. In any case, the X coordinate of the midpoint of the two points that intersect the through hole 35 circumference in both the positive and negative directions of X, and the Y coordinate of the midpoint of the two points that intersect the through hole 35 circumference in both the positive and negative directions of Y, Becomes the coordinates of the base point of the detected through hole 35. The position based on the hole center data can be used as the coordinates of the base point 50.
[0028]
As for the direction of scanning radially from the base point 50, in FIG. 7, eight directions (directions of arrows A to H) are scanned with respect to the base point 50 every 45 degrees. The number of scanning lines in the inspection direction can be arbitrarily set. However, if the number of scanning lines is set to multiple directions, the inspection can be performed with high accuracy, but the amount of acquired data increases and the inspection time becomes long. Further, if the number of directions is reduced, the inspection time becomes short, but the accuracy decreases. Therefore, the inspection direction is determined in consideration of inspection time, accuracy, and the like. If the number of directions is set to about 8 directions to 16 directions, the inspection time can be shortened while maintaining the inspection accuracy.
[0029]
Then, as shown in FIG. 8, the distance from the base point 50 calculated by the above-described method or the like to the position where the through hole is removed radially toward the outer peripheral portion is measured. In addition, if the center point of the formed through hole coincides with the hole center data acquired and set from CAD data or non-defective product data, and each of the measured through holes is normal without foreign matter in the through hole, each measured All directional distances are equal to the through-hole radius. Therefore, in this inspection method, it is determined whether or not the through-hole radius is within an allowable range for each inspection direction. The inspection can be determined in the same manner by using the diameter of the through hole obtained from two directions in which the inspection direction is symmetric about the center.
[0030]
Next, a method for measuring the distance in the image information will be described. Pixels with density values exceeding 200 from the base point 50 are counted in units of pixels, and the distance corresponding to the size of the substrate to be inspected corresponds to the number of pixels counted until the density value changes to 200 or less, that is, the point outside the through hole. To calculate the through-hole radius. For example, when there is no foreign substance on the scanning line as shown by the arrow C in FIG. 8 and the shape of the peripheral portion of the through hole 35 is normal, the converted distance is the normal radius registered in advance. Since they are equal, it is determined to be normal. However, when the foreign object 51 is present on the scanning line as indicated by the arrow E direction, the measured through hole radius is calculated based on the number of pixels obtained by counting the distance from the base point 50 to the change point 55 at the end of the foreign object 51. Is determined to be within the allowable range. In such a case, since the measured through-hole radius is shorter than the normal radius, the substrate to be inspected is determined to be defective. The application of this inspection method is not limited to a circular through hole as in this embodiment. For example, even for polygons, ellipses, and other shapes, distances may be measured radially from a predetermined position (for example, the center of gravity) to determine whether each is within an allowable distance range. In this case, an allowable range is set in advance for each direction, and it is determined whether or not the standard is satisfied for each direction.
[0031]
Further, the same scanning may be performed after binarization without scanning the gray image as it is. As an example of scanning in a binarized image, a threshold value of density value 200 is divided into data of 1 and 0, and when the data is 1 (white on the image), a through-hole pixel is through. If it is recognized as a hole 35 and the data is 0 (black on the image), it is recognized as a substrate portion or a wiring pattern. Therefore, the portion where the data value changes from 1 to 0 (the portion where 1 and 0 are aligned in the pixel) is a portion that is out of the through hole 35 such as the outer peripheral portion of the through hole and the boundary with the foreign matter. Then, through-hole pixels are counted in each direction from the base point, and the number of pixels is converted into a length corresponding to the surface of the substrate to be inspected. In addition, the count is stopped assuming that the portion where the 0 data appears on the scanning line has reached the portion outside the through hole 35 such as the substrate portion, the wiring pattern or the foreign matter, and the distance from the base point to the point is within the allowable range. It is determined whether or not there is.
[0032]
Further, FIG. 9 shows an example in which an elongated foreign matter 51 adheres to the inside of the through hole 35. In the case of such an elongated foreign matter 51, it is difficult to determine a defect by a conventional method. However, when the inspection method as in the present embodiment is used, as shown in FIG. 9, the scanning line intersects the foreign object 51 to detect the change point 55, and the distance from the base point 50 to the change point 55 is allowed. In order to determine that it is out of range, it is determined to be defective.
[0033]
Note that the distance is measured by counting the number of through-hole pixels from the base point 50 to a position off the through-hole 35, but exists within a predetermined distance (within a predetermined number of pixels) from the base point 50 in the inspection direction. It is also possible to determine whether the through hole 35 is good or bad by counting the through hole pixels. In this way, for example, as shown in FIG. 10, when there is a foreign object 51 that does not contact the peripheral portion of the through hole 35, the scanning line detects the foreign object 51 at the change point 55 and then detects the through hole pixel again. become. The length of the foreign matter 51 on the scanning line can be calculated from the total number of through-hole pixels. In this way, for example, a small number of pixels (for example, one pixel out of 100 pixels) in the scanning line are mixed as noise, and even if it is determined that the pixel is not a through-hole pixel, it can be recognized as an error range and is normal. It is possible to prevent an object from being erroneously determined to be defective. In this case, the inspection distance scanned by the scanning line can be arbitrarily set. However, at least the radius of the through hole is necessary, and if it is set longer than necessary, unnecessary data increases and the amount of image data increases. It is necessary to set in consideration of the substrate state, inspection time, and the like.
[0034]
As shown in FIG. 11, even if the through-hole 35 is a perfect hole, if the size and shape of the wiring pattern 17 are not accurate, the information should be detected during scanning to determine abnormality. Therefore, it is most desirable to inspect both the radius and the wiring pattern width. As described above, the radius of the through hole is measured for each scanning line, but the wiring pattern width is similarly measured for each scanning line. As shown in FIG. 11, after the scanning line to be inspected radially from the center reaches the outer periphery of the through hole, the wiring pattern width is also measured. In this image information, a threshold value 1 (density value 200) for distinguishing between a through hole (density value around 250) and a wiring pattern (density value around 120), a resin pattern of the wiring pattern and the substrate portion (density value of 40 or less). ) Have a threshold value 2 (density value 80) and two threshold values. Therefore, pixels corresponding to each element are counted with a pixel having a density value of 200 or more being a through-hole pixel, a pixel having a density value of 80 or more and less than 200 being a wiring pattern pixel, and a pixel having a density value of less than 80 being a substrate portion pixel.
[0035]
Then, the width of the wiring pattern from the inner periphery to the outer periphery of the wiring pattern is measured by counting the number of wiring pattern pixels by using scanning lines extending radially from the base point. In FIG. 11, taking a scanning line scanning in the direction of arrow G as an example, it is determined whether the distance from the base point 50 to the change point 52a satisfies the allowable range as the through-hole radius, and the change point 52a to the change point 52b. It is determined whether or not the allowable range is satisfied with the distance up to the wiring pattern width. The allowable range may be set uniformly in all directions or may be set for each direction. Even when the wiring pattern inspection is performed as described above, the quality may be determined by counting pixels existing within a predetermined distance in each inspection direction. For example, after counting through-hole pixels and wiring pattern pixels existing within a certain distance from the base point 50 and converting the number of each pixel to a distance, it is determined as defective if the distance is outside the allowable range. It becomes. Further, if one of the wiring pattern width and the through hole radius is out of the allowable range even in one direction, the substrate to be inspected is determined to be defective.
[0036]
In the present embodiment, the case where the base point 20 and the center point of the through hole coincide with each other has been described. However, in the case where they do not match, the center point is calculated based on the distance confirmed from the base point 20 in a plurality of directions, and the calculation is performed. The same inspection can be performed by calculating the distance to the position indicating information other than the through hole based on the center point.
[0037]
There are the following two types of processes for forming the through hole and the wiring pattern of the substrate 11 to be inspected. In the first forming step, after a through hole is formed on a resin substrate with copper on both sides by a drill, plating is performed including the inside of the through hole. Then, the through holes and necessary wiring portions are masked, a wiring pattern is formed by etching or the like, and then the masking is removed to fill the through holes.
[0038]
In the second forming step, after a through hole is formed on a resin substrate with copper on both sides by a drill, plating is performed including the inside of the through hole. Then, after filling the through hole, masking is performed on a necessary wiring portion, a wiring pattern is formed by etching or the like, and then the masking is removed.
[0039]
When the inspection target shown in the embodiment of the present invention is the substrate 11 to be inspected in the first formation process, the wiring pattern is formed, the masking is removed, and the through hole is filled, that is, the through hole is formed. It is desirable for the substrate to have a plating in the hole and a wiring pattern. In this case, the through hole inspection and the wiring pattern inspection can be performed simultaneously.
[0040]
Further, in the case of the substrate 11 to be inspected by the second formation process, after plating including the through hole and before filling the through hole, that is, the through hole is plated, and the wiring pattern is formed. It is desirable that there is no state. In this case, the through hole inspection and the wiring pattern inspection are performed separately. In any case, it is desirable to carry out in a state where plating is provided in the through hole. The reason for this is that shavings or the like adhering to the wall surface of the through hole drilled on the substrate to be inspected is slightly separated from the wall surface when the plating solution passes through the through hole. This is because the possibility of existing as a foreign object in a crossing shape increases.
[Brief description of the drawings]
FIG. 1 is a front view showing an example of an inspection apparatus according to the present invention.
FIG. 2 is a side view of FIG.
FIG. 3 is an enlarged view showing a main part of FIG. 2;
4 is a perspective view conceptually illustrating FIG. 3. FIG.
FIG. 5 is a block diagram showing an electrical configuration of a main control unit in the inspection apparatus.
FIG. 6 is a block diagram showing an electrical configuration of a photographing / analysis unit.
FIG. 7 is an explanatory diagram showing an example of inspection directions on an image of a through hole.
FIG. 8 is an explanatory diagram of an example of a through-hole state and an example of an analysis method thereof.
FIG. 9 is an explanatory view showing Example 2 of the through-hole state of FIG.
10 is an explanatory view showing Example 3 of the through-hole state of FIG.
11 is an explanatory view showing Example 3 of the through-hole state of FIG. 8;
[Explanation of symbols]
9a, 9b Pattern detection line illumination (second light source)
10 One-dimensional CCD camera (imaging device)
10a Upper CCD camera
10b Lower CCD camera
11 Board to be inspected
12a, 12b half mirror
13 X direction stepping motor
14 Y direction stepping motor
15 Z direction stepping motor
17a, 17b Line illumination for through-hole detection (first light source)
35 through hole
36 Substrate part
37 Wiring pattern

Claims (3)

An imaging device provided coaxially in the vertical direction on both sides of the substrate to be inspected;
A first light source that is provided on both sides of the substrate to be inspected and has corresponding half-mirrors, and illuminates incidently toward the imaging device located on the opposite side of the substrate to be inspected;
A second light source provided on the same side as the imaging device on both sides of the substrate to be inspected, and irradiating the imaging position of the imaging device from an oblique direction;
With
The imaging device simultaneously receives on both sides the transmitted light of the through-hole due to the oblique illumination from the opposite side and the reflected light from the second light source from the surface of the substrate to be inspected on the same side. A printed wiring board inspection apparatus having a mechanism in which the positions are the same positions on the inspected substrate opposite to each other. The first light source is
The first line illumination that irradiates light in a one-dimensional manner, and the falling illumination by the first line illumination irradiates the substrate to be inspected in a substantially line shape, and in the through hole on the irradiation position, Emit the transmitted light to the opposite side,
Furthermore, the imaging apparatus has a line sensor that receives light information in a one-dimensional manner, and the line direction is the same as the line direction of the first light source, and the transmitted light from the opposite side by the line sensor. The printed wiring board inspection apparatus according to claim 1 , wherein the printed circuit board inspection apparatus receives light. The first light source is
The first line illumination that irradiates light in a one-dimensional manner, and the falling illumination by the first line illumination irradiates the substrate to be inspected in a substantially line shape, and in the through hole on the irradiation position, Emit the transmitted light to the opposite side,
The second light source is
Irradiate light in a one-dimensional manner, and the line direction is the same as that of the first line illumination, and the imaging position of the imaging device provided on the same side is irradiated in a substantially line shape. ,
Furthermore, the imaging device has a line sensor that receives light information in a one-dimensional manner, and the line direction is the same as the line direction of the first light source and the second light source. The printed wiring board inspection apparatus according to claim 1 , wherein the transmitted light from the opposite side and the reflected light from the opposite side are received.

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