JPH03218406A - Picture processing method for soldering surface - Google Patents

Abstract

PURPOSE:To exactly decide the quality of a soldering joint surface by changing the luminance distribution of picture data and recognizing the presence/absence of eccentricity in the direction of the change. CONSTITUTION:A printed circuit board 2 is loaded on an X-Y table 1 and the circuit board 2 is lighted up by a ring-shaped light source 6. Then, the image of the circuit board is picked up by a TV camera 9 and the picture element signals of the camera 9 are A/D converted 11 and temporarily stored in a picture memory 12 as the picture data. A computer 10 binarizes the picture data and decides the quality of a soldering joint part 4 and when it is decided the part 4 is defective, an actuator 5 is operated so as to exclude the circuit board 2 in the side direction of the table 1. The computer 10 operates the table 1 through an X-Y table control part 3 so that the joint part 4 can be positioned just under the camera 9, changes the vertical position of the light source 6 through a light source position control part 7 as needed and changes the luminous intensity of the light source 6 through a light source luminous intensity control part 8. Thus, the luminance distribution of the picture data is changed, the eccentricity in the direction of the change is recognized and the quality of the joint part can be decided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image processing method of a solder surface for determining the quality of solder joints formed on a substrate.

[Prior Art] Traditionally, the surface of a solder joint on a printed circuit board is illuminated, the reflected image is captured as image data by a TV camera, and binarized image processing is performed based on the image data. An image processing method for determining the quality of solder joints has been proposed.

However, in this image processing method, low brightness areas may occur on the solder surface image due to the hemispherical shape of the solder surface and the metallic luster of the solder surface. For this reason, the low brightness area is a blowhole,
There is a risk that a soldering defect such as a hole may be mistakenly recognized, and a good soldered joint may be determined to be defective.

Therefore, the current countermeasure is to provide an extremely large number of light sources for illumination to uniformly brighten the solder surface (Japanese Patent Application Laid-Open No. 6-0-2
5 4 0 5), etc.

[Problems to be Solved by the Invention] However, with the above-mentioned conventional measures, when another component 23 is mounted near the solder joint 22, as in a double-sided mounting board 2l as shown in FIG. In this case, even if multiple light sources were used to illuminate the solder surface, it was not effective because the solder surface did not have high brightness due to the shadow of the component 23. Furthermore, when there are a large number of light sources, as shown in FIG. 9, a shallow defect recess 24 formed on the solder joint 22 becomes highly bright, making it impossible to detect the defect.

This invention has been made in view of the above-mentioned circumstances, and its purpose is to appropriately determine the quality of solder joints.

[Means for Solving the Problems] In order to achieve the above object, the present invention illuminates the surface of a solder joint formed on a substrate, captures the reflected image as image data with an image pickup device, and captures the reflected image as image data. In a solder surface image processing method that determines the quality of a solder joint by processing image data, the brightness distribution of the image data captured by an imaging device is changed and the direction of change in the brightness distribution is recognized. Then, the quality of the solder joint is determined based on the presence or absence of deviation in the direction of change.

[Operation] According to the above configuration, the brightness distribution of the image data captured by the imaging device is changed, the direction of change in the brightness distribution is recognized and processed, and the solder joint is determined based on the presence or absence of bias in the direction of change. Since the quality of the solder joint is judged as good or bad, a proper judgment can be made while preventing misidentification of the low brightness area of the solder joint.

[Example] Hereinafter, an example embodying the present invention will be described in detail based on the drawings.

FIG. 1 is a schematic diagram of an image processing apparatus to which the solder surface image processing method of this embodiment is applied.

The X-Y table l is a well-known workpiece position changing device that places a printed circuit board 2 as a workpiece and moves the board 2 in the X-Y direction. It is controlled by the control section 3. or,
In the vicinity of the X-Y table 1, if the solder joint 4 made on the printed circuit board 2 is defective, there is a
An actuator 5 is provided which is actuated to expel the object to the side of the X-Y table l.

A ring-shaped light source 6 for illuminating the printed circuit board 2 is provided above the X-Y table l. The position of this tip source 6 can be controlled in the vertical direction by a light source position control section 7 including a step mode and the like. Further, the luminous intensity of the tip source 6 can be controlled by a light source luminous intensity control section 8.

A TV camera 9 is provided above the light source 6 as an imaging device for taking an image of the solder joint 4 on the printed circuit board 2 through the ring-shaped space of the light source 6. That is, the surface of the solder joint 4 is illuminated by a light source 6, and a reflected image thereof is taken by a TV camera 9. At this time, the level of the signal (pixel signal) from the TV camera 9 that photographed the high brightness part of the solder joint 4 is high, and on the contrary, the level of the pixel signal from the TV camera 9 that photographed the low brightness part is low. Become.

The computer 10 is composed of a central processing unit, a read-only program memory in which a control program is stored in advance, a readable and rewritable working memory that temporarily stores arithmetic processing results of the central processing unit, and the like. and,
Pixel signals taken by the TV camera 9 are converted from analog values to digital values by the A/D converter 11, and then temporarily stored in the image memory 12 as image data.

The image data stored in the image memory 12 is output and displayed on the monitor 13, and is also taken into the computer 10 and subjected to binarized image processing to determine the quality of the solder joints 4 on the printed circuit board 2.

When the computer 10 determines that the solder joint 4 is defective, it outputs a control signal for operating the actuator 5.

The computer 10 also outputs a control signal to the X-Y table controller 3 to position the solder joint 4 on the printed circuit board 2 directly below the TV camera 9, and controls the X-Y table l.
Activate. Further, the computer 10 controls a light source position control unit 7 to change the vertical position of the light source 6 as necessary.
At the same time, it outputs a control signal to the light source luminous intensity control unit 8 in order to change the luminous intensity of the light source 6 as necessary.

Next, an image processing method performed using the image processing apparatus configured as described above will be described according to the flowchart shown in FIG. Note that this flowchart shows the control processing performed by the computer 10.

First, in step 101, image data is captured. That is, image data taken by the TV camera 9, converted by the A/D converter l1, and temporarily stored in the image memory 12 is taken in. Here, since the shape of the solder joint 4 is hemispherical, when the ring-shaped light source 6 illuminates the solder joint 4 from above, the solder surface image captured as shown in FIG. (2) The luminance distribution in 4 is contour-shaped.

Next, in step 102, the captured image data is binarized. That is, as shown in FIG. 3, the image data of the captured solder surface image l4 is binarized at a predetermined level, and a substantially circular low brightness area 15A is extracted.

Subsequently, in step 103, as shown in FIG. 3, the horizontal (x)
The horizontal length 1xl, which is the length in the direction, and the vertical length lyl, which is the length in the vertical (y) direction, are calculated. This is calculated from the number of pixels in the low-luminance area 15A among all pixels of the image data.

Next, in step 104, the binarization level of the captured image data is changed.

That is, as shown in FIGS. 4 and 5, the previously captured image data is binarized again at a higher level than the previous binarization level, and the low luminance area 15B is extracted anew from the solder surface image l4. Here, the solder surface image l4 in FIG.
The solder surface image l4 in FIG. 5 shows an image when the solder joint 4 is defective.

Subsequently, in step 105, as shown in FIGS. 4 and 5, the horizontal length lX2 and vertical length ly2 of the low luminance area 15B extracted again by binarization are calculated, respectively. and,
In step 106, a change in horizontal length ΔlX and a change in vertical length Δ1y are calculated. That is, Δ(! x=I2 x2 −1 xi Δβy=py2−17y1 are calculated respectively.

Thereafter, in step 107, a ratio K between the previously calculated vertical change ΔIll and the horizontal change Δlx is calculated, and in step 108, the horizontal change Δl
The sum L of x and the vertical change Δ1y is calculated. here,
The ratio K and the sum are as described above, for the low luminance areas 15A and 15B that change depending on the change of the binarization level.
This value is used in steps 109 to 111 below to determine whether there is a bias in the direction of change.

Subsequently, in step 109, the step 107
It is determined whether the ratio K calculated in is a value included in the value taking into account the error ±α. That is, it is determined whether the value is larger than the value of (1)-α and less than or equal to the value of l+α.

If the ratio K is included in the value considering the error ±α, that is, the low luminance area 15B obtained the second time by changing the binarization level has an approximately circular shape as shown in FIG. If the difference in horizontal and vertical changes Δlx and Δly becomes small, it is determined that the solder joint 4 is defective and the process moves to step 110. In the same step 110, a board removal command signal is sent to the actuator 5. output to the faulty printed circuit board 2 and activates the actuator 5.
is removed and the subsequent processing is temporarily terminated.

On the other hand, if the ratio K is not included in the value considering the error ±α, the process moves to step 111, and in the same step 111, the sum L calculated in the step 108 is larger than the predetermined judgment value β. Determine whether it is small or not.

If the sum L is smaller than the predetermined judgment value β, that is, the low luminance area 15B obtained for the second time by changing the binarization level has a substantially circular shape and is horizontally long and horizontally long, as shown in FIG. If the vertical changes Δlx, Δ1y become small, the solder joint 4 is considered defective and step 1 is performed.
10, and in the same step 110, a signal of a board removal command is output to the actuator 5, the actuator 5 is operated to remove the defective printed circuit board 2, and the subsequent processing is temporarily terminated.

On the other hand, if the sum L is not smaller than the predetermined judgment value β, that is, the low luminance area 15B obtained for the second time by changing the binarization level forms a curved ellipse as shown in FIG. If one of the horizontal and vertical changes Δlx and ΔIll becomes larger, it is assumed that the solder joint 4 is good, and the process moves to step 112. In the same step 112, the solder joint 4 is judged to be To do this, a board position change command signal is output to the XY table control section 3 to change the position of the printed circuit board 2, and the subsequent processing is temporarily terminated.

In other words, in the processing of this embodiment, the binarization level is changed back and forth for the captured image data, and the solder surface image l4 is
By changing the brightness distribution of
, .DELTA.1y are summed together with their ratio K to determine the quality of the solder joint 4.

Therefore, if the solder surface image l4 is obtained by setting the second binarization level of the image data slightly higher than the first binarization level, if the solder joint 4 is good, the low luminance area 1
5B grows along the contour lines as shown in FIG.

In other words, the low luminance area 15A during the first binarization grows more vertically than horizontally.

On the other hand, if the solder joint 4 is defective, the low brightness area 15B has an almost circular shape, similar to the low brightness area 15A during the first binarization, as shown in FIG. You will grow without it.

In other words, the low brightness area 15A during the first binarization grows almost equally in all directions, and the amount of growth is much greater than the low brightness area 15B in FIG. 4, which is caused by light reflection. It becomes something small.

If we look at the change in brightness level with respect to the coordinate position centered on the solder joint, we get a graph as shown in FIG. 7, for example. As can be seen from this graph, the change in the brightness level near the solder joint is clearly different between cases where the solder joint has a defect and cases where there is no defect.

That is, when there is a defect, there is almost no change in the brightness level around the solder joint, and when there is no defect, there is a change in the brightness level.

As described above, in the solder surface image processing method in this embodiment, the brightness distribution of the image data captured by the TV camera 9 is changed and the direction of change in the brightness distribution is recognized and processed, that is, the low brightness area 15A is The vertical and horizontal directions are recognized by changing the brightness area 15B, and if there is a bias in the amount of change in the vertical and horizontal directions, the solder joint 4
It is determined that the solder joint 4 is good, and if there is little deviation in the amount of change, it is determined that the solder joint 4 is defective.

As a result, in order to judge the quality of the solder joints 4, there is no need for special treatment such as spraying alcohol on the solder surface to suppress metallic luster, as in the past. The steps of installation and solder surface treatment can be omitted, and the cost required for determination can be reduced. Furthermore, it is not necessary to provide a large number of light sources for illumination to make the solder surface uniformly high in brightness as in the past, and the manufacturing cost of the illumination device can be reduced. Furthermore, even if other components are mounted near the solder joints on a double-sided mounting board, the single light source 6 provides illumination to properly judge the quality of the solder joints while avoiding the effects of shadows. be able to. Further, even if a defective concave portion is formed on the solder joint, the defect can be appropriately determined. In other words, it is possible to appropriately and inexpensively determine the quality of solder joints in general.

Note that this invention is not limited to the above embodiments,
The present invention can be implemented as follows by changing a part of the structure as appropriate without departing from the spirit of the invention.

(1) In the above embodiment, the captured image data is binarized twice based on different levels, and the resulting changes in horizontal and vertical lengths Δlx and Δly of the low-luminance areas 15A and 15B are calculated. Although the bias in the direction of change in the low luminance areas 15A and 15B was determined based on the ratio K and the sum L, in order to further improve the detection accuracy, the binarization level of the image data was changed in stages. Calculate the average value of the ratio K and sum L of the changes before and after each stage △lx, Δzy, and calculate the bias in the direction of change in the low luminance area based on the average value. may be determined.

(2) In the above embodiment, the image data that was captured once was binarized twice based on different levels. Binarization may be performed based on the level.

(3) In the above embodiment, in order to change the brightness distribution of image data, the binarization level was changed in the computer IO, but the part where the binarization level is changed is the A/D
It can also be a converter. In other words, there are two A/D converters that binarize pixel signals from the T camera at different levels.
pixel signals from the TV camera are input to each of these two A/D converters to perform binarization, or a binarization level controller is provided for one A/D converter. The image signal from the TV camera may be binarized by the A/D converter while changing the binarization level twice before and after by the binarization level controller.

Further, in order to change the brightness distribution of the image data, the vertical position of the illumination light source 6 may be changed or the luminous intensity of the light source 6 may be changed.

(4) In the above embodiment, the ring-shaped light source 6 was provided, but
The light source is not limited to a ring shape, and various types of light sources may be used.

(5) In the embodiment described above, binarization image processing was employed to recognize the direction of change in the brightness distribution of image data, but grayscale image processing may also be employed.

[Effects of the Invention] As detailed above, according to the present invention, the brightness distribution of image data captured by an image pickup device is changed, the direction of change in the brightness distribution is recognized and processed, and the bias in the direction of the change is corrected. Since the quality of the solder joint is judged based on the presence or absence of the solder joint, it is possible to judge the quality of the solder joint properly and at low cost without applying any special treatment to the solder surface or installing multiple light sources for illumination. It has excellent effects and can be done at low cost.

[Brief explanation of drawings]

1 to 7 are drawings showing embodiments of the present invention, in which FIG. 1 is a schematic configuration diagram of an image processing apparatus to which the solder surface image processing method is applied, and FIG. A flowchart explaining an image processing method performed using an image processing device, FIGS. 3 to 5 are diagrams explaining changes in a low brightness area in a soldering surface image, and FIG. 6 is a diagram explaining the brightness distribution in a soldering surface image. FIG. 7 is a graph illustrating the change in brightness level with respect to the coordinate position centered on the solder joint. FIG. 8 is a side view showing a conventional double-sided mounting board;
FIG. 9 is a side sectional view illustrating a defective concave portion of a solder joint in the conventional example. In the figure, 2 is a printed circuit board, 4 is a solder joint, 6 is a light source,
9 is a TV camera as an imaging device, l4 is a solder surface image, 1
5A and 15B are low brightness areas.

Claims (1)

[Claims] 1. Illuminating the surface of a solder joint formed on a substrate, capturing the reflected image as image data with an imaging device, and determining the quality of the solder joint by processing the image data. In the solder surface image processing method, the brightness distribution of image data captured by the image pickup device is changed, and the direction of change in the brightness distribution is recognized and processed,
A solder surface image processing method, wherein the quality of the solder joint is determined based on the presence or absence of deviation in the direction of change.