JPH06300538A - Contour recognition technique and shape inspection method using the technique - Google Patents

Abstract

PURPOSE:To detect the contour of a body, and inspect the shape thereof. CONSTITUTION:A slit beam is cast on a recognition object from the predetermined direction, and a slit beam image reflected from the object is photographed from the predetermined direction. The slit beam reflection image 33 so obtained is divided into elements for the breadth of one picture element, along the length of the slit beam, and the position (p) of the center of gravity of the image 33 is obtained for every divided picture element breadth. Then, the outline position of the cross section of the object along a slit beam irradiation direction is calculated for every picture element on the basis of the data of each position of the center of gravity. Then, a comparison is made between the preliminarily established cross section data of the recognition object and the calculated outline data, and the acceptance or non-acceptance of the object is judged, based upon whether a difference is within an allowance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recognizing a contour of an object to be recognized and discriminating the shape of the object, such as when inspecting a soldering state of an electronic component mounted on the surface of a printed circuit board. It is applied.

[0002]

2. Description of the Related Art Various methods for inspecting the state of an object by optical means have been proposed. In JP-A-4-15506, which is given as an example, in order to inspect the soldering state of the components of the printed circuit board, a laser irradiation means for sweeping and irradiating a laser spot light toward the solder, and a sweep irradiation in the transverse direction of the solder A light receiving means for receiving the reflected light of the laser spot light thus generated is provided, and the peak position in the transverse direction of the solder is detected. Then, a light receiving means for receiving the reflected light of the laser spot light swept and irradiated in the vertical direction passing through the peak position is provided, the height position of the solder along the vertical direction is detected, and the quality of the solder shape is judged. There is.

[0003]

In such a method for inspecting an object shape, in order to detect the shape with high accuracy, it is necessary to irradiate the laser spot light with a large number of sweeps, so that the inspection time tends to be long. Absent. In the present invention, the slit light is radiated toward the recognition object only once, the reflected light is taken in, the shape of the recognition object is detected with high accuracy or according to the required accuracy, and the shape is detected in a relatively short time. It is intended to provide a method for determining the quality of.

[0004]

In the present invention, slit light is emitted from a predetermined direction toward an object to be recognized, and a slit light image reflected from the slit light is imaged from the predetermined direction. This slit light reflection image is divided into 1-pixel widths in the length direction of the slit light, and each barycentric position of the slit light reflection image is obtained for each divided 1-pixel width. , The outer shape position of the cross section of the recognition object in the slit light irradiation direction is calculated. Then, the preset cross-sectional shape data of the recognition target object is compared with the calculated outer shape data, and whether the shape of the recognition target object is good or bad is determined depending on whether or not it is within the allowable value.

Further, according to the present invention, the above-mentioned slit light reflection image that is picked up is divided in the lengthwise direction of the slit light into widths that are integer multiples of one pixel depending on the shape state of the recognition object and the recognition accuracy. Then, each barycentric position of the slit light reflection image is obtained for each division width, and the outer shape position of the cross section of the recognition object in the slit light irradiation direction is calculated from each barycentric position data for each division width. Then, the preset cross-sectional shape data of the recognition target object is compared with the calculated outer shape data, and whether the shape of the recognition target object is good or bad is determined depending on whether or not it is within the allowable value.

[0006]

According to the required accuracy, the slit light reflection image from the object to be recognized has one pixel or one pixel in the length direction of the slit light.
It is divided into widths that are an integral multiple of the pixel, and the contour position of the cross section in the slit light irradiation direction is calculated for each divided width. Then, only the calculated contour position within the allowable value is determined as a non-defective product in terms of shape.

[0007]

EXAMPLE An example of using the contour recognition method of the present invention and the shape inspection method using the same for soldering inspection will be described. FIG. 1 is a perspective view showing a main configuration of a soldering inspection apparatus according to this embodiment, in which leads 21 of an electronic component 2 surface-mounted on a printed circuit board 1 are successfully soldered onto a copper foil pattern 11 of the printed circuit board. It is to inspect whether it is attached.

Reference numeral 3 is a light source for irradiating a laser slit light,
It is held downward by a θ rotary head unit (not shown) that is suspended right above the printed circuit board 1. Reference numeral 4 denotes an image pickup means such as a CCD camera, the optical axis of which forms a constant tilt angle with the optical axis of the laser slit light, and the longitudinal direction of the horizontal section of the laser slit light (hereinafter referred to as the length direction of the slit light). It is fixed to the rotary head together with the light source 3 so as to be orthogonal to. In FIG. 1, the printed circuit board 1 is an XY not shown.
It is arranged horizontally on a table, and the electrodes and leads of the electronic component to be inspected are positioned under the laser slit light emitted from the light source 3. Thus, the electronic component 2
The copper slit pattern 11 corresponding to the lead 21 and the solder portion (hereinafter referred to as a solder fillet) 12 for adhering the lead and the copper foil pattern are irradiated with the laser slit light 31 in parallel with the protruding direction of the lead.

At this time, the position of the copper foil pattern on the printed circuit board and the mounting position of the mounted electronic component have already been recognized in a separate process (the detailed description thereof is omitted because it is not the gist of the present invention). Only the printed circuit board whose deviation amount is within the allowable value is subjected to the soldering inspection of this embodiment. And
Based on the position recognition data, the laser slit light 31
The lengthwise center of the lead or the part electrode is aligned with the tip of the electrode, and the horizontal direction of the laser slit light (hereinafter referred to as the width direction of the slit light) is centered in the width direction of the lead or copper foil pattern. The printed board 1 is moved XY so as to coincide with the center of the lead (the direction orthogonal to the protruding direction). If the width direction center position of the lead and the corresponding copper foil pattern is misaligned, align the width direction center of the laser slit light with the midpoint between the two centers, and the laser slit light will reach the apex position of the solder fillet. The position of the printed circuit board 1 may be corrected so that it is irradiated.

The operation of this embodiment will be described with reference to the drawings. FIG. 2 is an enlarged perspective view showing a lead soldering portion of an electronic component, in which laser slit light is radiated from directly above toward the lead 21, the copper foil pattern 11 and the solder fillet 12 for bonding them. There is. (Thus, in this case, the cross section in the slit light irradiation direction is the cross section in the height direction of the solder.) 32 is a strip-shaped reflected light image when the laser slit light illuminates each surface of the lead, the solder fillet, and the copper foil pattern. The center of the longitudinal direction thereof coincides with the tip of the lead 21. When this reflected light image 32 is taken by the CCD camera 4, an image 33 as shown in FIG.
The horizontal center of the reflected light image 32 is located at the center of the horizontal field of view of the D camera 4.

FIG. 4 is an explanatory view showing a method for inspecting a soldering state. As shown on the left side of FIG.
The horizontal direction of the CD camera 4 is divided into 1-pixel widths, and the center of gravity p of the image 33 is obtained for each 1-pixel width. On the right side of FIG. 4, there is shown the state of each barycentric position p, where the horizontal direction of the field of view of the CCD camera is the X (length) coordinate axis and the vertical direction is the H (height) coordinate axis. In the figure on the right side, a straight line L that passes through the position of the center of gravity having the lowest height among the positions of center of gravity p and is parallel to the X coordinate axis is used as a reference line. Then, the average of the H-coordinates of the center of gravity on the left side of the figure from the X-coordinate C of the visual field center is calculated, and the distance t between the average value U and the reference line L falls within the allowable amount compared with the lead thickness. To see if If the allowable amount is exceeded, it is determined that the leads are floating above the copper foil pattern, and the solder fillet is not inspected.

Next, a barycentric point px at a position separated from the X coordinate C of the center of the visual field in the right direction by a predetermined distance x is extracted, and a distance h between the H coordinate value of the barycentric point px and the reference line L is calculated. , As the height of the center of gravity px. (The actual height is calculated by h · cos θ, where θ is the elevation angle of the optical axis of the camera 4 as viewed from the printed circuit board by the triangulation method.) This distance h is evaluated by the height shape of the solder fillet 12. Confirm that the value is a value greater than or equal to a predetermined limit value as an index. If it is equal to or more than the limit value, it is determined that the soldering is good, and if it is less than the limit value, it is determined that the soldering is defective.

Further, when inspecting the soldering of components such as chip resistors, which are larger than the minute leads as shown in FIG. 2, division by pixel as shown in FIG.
Often not required for accuracy. In such a case, the division width of the image is set to an arbitrary integral multiple of one pixel according to the size of the solder fillet predicted from the shape of the component electrode, the center of gravity is obtained for each division width, and the same as above. Inspect the soldering condition. FIG. 5 illustrates this using the image 33. On the left side of FIG. 5, the image 33 is the CCD
The camera 4 is divided into two horizontal pixel widths, and the center of gravity p of the image 33 is calculated for each two pixel width. The right side of FIG. 5 shows the state of each barycentric position p on the X-H coordinate axis, similarly to the right side of FIG. Similar to the case of FIG. 4, the reference line L and the average value U are obtained, and the presence or absence of floating of the component electrode or the like is determined by the distance t. Then, the barycentric point px at a position away from the X coordinate C in the right direction in the drawing by a predetermined distance x is extracted, and the height h of the barycentric point px is extracted.
To calculate. If the height h is equal to or more than a predetermined limit value, it is determined that the soldering is good, and if it is less than the limit value, it is determined that the soldering is defective.

In this embodiment, the printed circuit board is held on the XY table, and the light source and the image pickup means are suspended above it so as to be rotatable by θ. However, the printed circuit board is held at a predetermined position and the upper side thereof is covered. The light source and the image pickup means may be suspended on the XY stage so that they can rotate by θ. Further, in the present embodiment, when the height shape of the solder portion is determined, only the height of a predetermined position is used as a determination reference, but all the calculated height positions are determined by comparing with a preset specified value. However, the contour quality data in the height direction may be used as the determination reference. Furthermore, in the present embodiment, an example in which the contour in the height direction of the soldering portion of the electronic component is recognized and applied to the inspection of the soldering shape has been described, but the contour recognition method of the present invention and the shape using the contour recognition method The inspection method is not limited to the above-mentioned embodiment, and the inspection object may be applied to the bonding state between the objects or the object itself, and the height, width, and depth contours thereof are recognized by the irradiation direction of the slit light. However, it is also possible to judge the quality of the shape of the inspection object based on the recognized contour data.

[0015]

The slit light reflection image from the object to be inspected is divided into one pixel in the length direction of the slit light or every width of an integral multiple of one pixel, and the slit light irradiation direction of the object is divided into each divided width. Since the outer shape position of the cross section is calculated, the contour shape of the cross section can be approximated by the polygonal line of the set division width pitch by one image capture. Therefore, by changing the division width according to the inspection object, it is possible to perform approximation with various accuracy and reduce the total inspection time to the necessary minimum.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a soldering inspection method according to an embodiment of the present invention.

FIG. 2 is a perspective view illustrating an irradiation state of slit light.

FIG. 3 is a diagram illustrating a reflected light image of slit light captured by an image capturing unit.

FIG. 4 is an explanatory diagram showing a method for inspecting a soldering state.

FIG. 5 is an explanatory diagram showing another method for inspecting a soldering state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed circuit board 11 Copper foil pattern 12 Solder fillet 2 Electronic component 21 Electronic component lead 3 Light source 4 Imaging means

Claims (4)

[Claims] 1. An object to be recognized is irradiated with slit light,
A method for recognizing a slit light irradiation portion of an object to recognize an outline of the object, irradiating the object with slit light from a predetermined direction, and a slit light image reflected from the object. Is imaged from a predetermined direction, the slit light reflection image is divided into 1-pixel widths in the length direction of the slit light, and each barycentric position of the slit light reflection image is obtained for each divided 1-pixel width, A contour recognition method characterized in that the contour position of a cross section of an object in the slit light irradiation direction is calculated for each pixel from each centroid position data, and the contour of the cross section is recognized. 2. Using the contour recognition method according to claim 1, the preset cross-sectional shape information of the recognition target is compared with the calculated contour data of the cross-section, and it is determined whether or not it is within the allowable tolerance. A shape inspecting method for determining whether the shape of the object is good or bad. 3. An object to be recognized is irradiated with slit light,
A method for recognizing a slit light irradiation portion of an object to recognize an outline of the object, irradiating the object with slit light from a predetermined direction, and a slit light image reflected from the object. Is imaged from a predetermined direction, the slit light reflection image, in the length direction of the slit light,
Divide into widths of integer multiples of 1 pixel according to the shape and recognition accuracy of the object, determine each barycentric position of the slit light reflection image for each of the divided widths, and from each of the barycentric position data, for each divided width A contour recognition method characterized in that the contour position of a cross section of an object in the slit light irradiation direction is calculated and the contour of the cross section is recognized. 4. Using the contour recognition method according to claim 3, the preset cross-sectional shape information of the recognition object is compared with the calculated contour data of the cross-section, and whether or not it is within the allowable tolerance. A shape inspecting method for determining whether the shape of the object is good or bad.