JPH07159338A - Inspection method for soldering - Google Patents

Abstract

PURPOSE:To judge the quality of a soldering with high accuracy by a method wherein a judgment region is divided into a plurality of regions according to the shape of a soldered part and the area ratio of the bright part to the dark part of reflected light in the individual regions is found. CONSTITUTION:A CCD camera 3 fetches the color image of a conveyed board in every section whenever the board is conveyed, and a read-out signal is output to a controller 4. The controller 4 is composed of a binarized circuit 41, an area extraction circuit 42 and a judgment control circuit 43. The circuit 41 binarizes the read-out signal, it outputs the binarized read-out signal to a monitor 5, and an image is displayed. The circuit 42 finds the area ratio of an area expressed by the number of pixels inside one detection region to an area occupied by a bright part regarding detection regions 14 to 16 which have been divided in, e.g. three. The circuit 43 takes into the area ratio, it compares the area ratio with a criterion range which has been preset regarding the regions 14 to 16, and it judges that solder is not wetted, imperfectly soldered or the like when the area ratio is the criterion range or higher. In addition, when the area ratio is the criterion range or lower, a soldered state is judged to be normal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering inspection method for determining the quality of soldering on a board.

[0002]

2. Description of the Related Art Conventionally, in order to judge the quality of soldering,
For example, as shown in Japanese Patent Laid-Open No. 2-212747, light is applied to the periphery of a soldered electronic component,
It was mainly performed based on the area ratio of light and dark of the light reflected from the soldered portion.

FIG. 5 is an explanatory view showing a conventional inspection apparatus. Reference numeral 203 denotes irradiation light from a light source (not shown), and this irradiation light 203 is adapted to be applied to an electronic component or a soldered portion to be inspected. 201 is a printed circuit board, and lands 207 are printed on the upper surface thereof.
Further, there is a chip 202 having an electrode 206 on the land 207, and the electrode 206 and the land 207 are connected by a solder 205.

As shown in the figure, the irradiation light 203 hits the electrodes 206, the solder 205, etc., respectively, and the reflected light 20
It becomes 4. Reflected light 204b, 204c from a flat surface such as the surface of the electrode 206 or the surface of the land 207 is input to the camera 200 provided above, but the reflected light 204a from the inclined solder 205 portion is reflected by the camera 200. Not entered in. Then, when the reflected light is viewed with the camera 200, as shown in the lower part of FIG.
8 and the dark portion 209 which is not input are distinguished. Therefore, the area ratio of the bright part and the dark part is calculated within the range of the detection regions 210 and 211, and the quality of the solder is judged from this area ratio. That is, if a certain reference value is set and the area of the bright portion is larger than this reference value, the amount of solder 205 is small and it can be determined that the soldering is defective. On the other hand, if the area of the bright portion is small, the amount of solder 205 is large, and it can be determined that the soldering is good.

[0005]

However, such a quality judgment causes the following problems. That is,
Since the shape of the solder varies, as shown in FIG. 6, the solder 205 may not be attached to a part of the electrode 206, while the solder may be attached to the other part of the electrode 206. Although this is a state where soldering connection strength is weak and soldering is defective, the area of the bright portion as a whole is sometimes smaller than the reference value, and this is erroneously determined as a good product.

In order to avoid such an erroneous detection, it is possible to increase the reference value so that it is not judged as a good product unless the area of the bright portion is too small. However, in this case, it is a good product. There is a possibility that it will be determined to be defective, and the quality cannot be determined accurately only by changing the setting of the reference level. Therefore, it is an object of the present invention to be able to accurately determine the quality of soldering without being affected by variations in the shape of solder.

[0007]

In order to achieve the above object, the present invention provides a soldering inspection method for determining whether a soldering of an electronic component on a board is good or bad in a predetermined area, depending on the shape of the solder. The predetermined area is divided into a plurality of areas and arranged, and the quality of soldering is determined based on the area ratio of the brightness of the reflected light in each of the divided areas.

[0008]

In the present invention, when determining the quality of soldering in a predetermined area, this area is divided into areas corresponding to the shape of the solder and arranged. Then, in each of the divided regions, the light-dark area ratio of the reflected light is detected. For example, if the bright area is large in a certain area, it is determined that the solder is not attached to a part of the area even if the bright area in the other area is small, and it is determined to be defective. On the contrary, if the bright area is small in all regions, it is determined to be good.

[0009]

1 is a schematic view of a soldering inspection apparatus showing a first embodiment of the present invention. On the substrate 1, electrodes of electronic components such as melf resistors mounted on lands are soldered. The transport rail 2 transports the substrate 1 after the soldering process to the inspection area.

Reference numeral 3 is a CCD camera for taking in a color image on the substrate 1 which has been conveyed by the conveying rail 2.
Although not shown, the light source is provided separately from the camera 3. The CCD camera 3 is a fixed type, but the substrate 1 (transport rail 2) in the transport area is divided into sections (for example, about 50 pieces per section) of the substrate 1 which are preliminarily divided by an XY robot or the like (not shown). Since each of the sections is moved so that the electronic component) and the camera 3 face each other, the CCD camera 3 can capture the image of each section of the substrate 1 divided in advance (that is, the camera 3). Is relatively moving each section to capture each image). Then, the CCD camera 3 sends a signal indicating the image of the substrate 1,
It outputs to the controller 4 mentioned later via a communication line. The camera 3 may be moved with the substrate 1 left as it is.

The controller 4 takes in the signal showing the above-mentioned image, recognizes the brightness state of the reflected light from the substrate 1, and judges the quality of the solder based on this state. In addition, the signal of this image is binarized and output to the monitor 5, which will be described later. Further, the controller 4 controls the blinking of the warning lamp 6, the display of the defective section (the section number is displayed on the display 61 shown in the figure) according to the quality of the solder, and the drive of the XY robot described above. .

The monitor 5 displays a binarized image (white, black) of the substrate 1. The warning lamp 6 blinks to inform the operator of a defective solder. In this example, a black and white image is used.
Not limited to this, the raw image of the substrate 1 may be displayed as it is. Further, it will be described in detail with reference to FIG. Figure 2
(A) is a block diagram of the above-mentioned inspection device. As shown in the figure, the solder 13 is attached to both electrodes of the melf resistor 12 mounted on the substrate 1 by a dipping process or the like.
The CCD camera 3 outputs an image of such a state of the solder 13 to the controller 4.

On the other hand, the controller 4 includes a binarization circuit 4
1, an area extraction circuit 42, and a determination control circuit 43. The binarization circuit 41 takes in the image, and based on the binarization threshold value stored in the memory of the circuit 41, it is bright (white) if the brightness of the reflected light in the image is larger than the binarization threshold value. If it is smaller than the threshold, it is judged as dark (black),
The original image is divided into two values, white and black. This 2
The digitized signal is also output to the monitor 5.

The bright area extraction circuit 42 finds the area occupied by this white. That is, in this example, as shown in the figure, the area occupied by the bright portion in one detection region is extracted as the number of pixels for each of the three detection regions 14, 15, and 16. Then, the area ratio between the area (the number of pixels) of one detection area and the area (the number of pixels) occupied by this bright portion is calculated for each of the detection areas 14, 15, and 16.

Next, the detection areas 14, 15 and 16 will be described in detail. As shown in FIG. 2B, the detection regions 14, 15, 16 in this example are arranged in three rows in the vertical direction (A) of the melf resistor 12. The areas of these regions are all the same, and the region 15 is provided along the vertical center of the resistor 12. On the other hand, the detection areas 14 and 16
Are provided near the upper and lower ends in the vertical direction of the 12 electrodes of the melf resistor. These three detection areas are based on past solder shape data, and the shape of the solder becomes remarkable when a solder defect occurs. It is provided so as to cover the changing portion.

A shaded area 17 in the drawing indicates that the reflected light is not input to the camera 3 and is a dark area due to the oblique shape of the solder 13, and 18 indicates that the reflected light has a planar shape and the reflected light is This indicates that it is the bright part input to the camera 3. As described above, the bright area extraction circuit 42 in the present example.
Calculates the area and the area ratio of the bright part in each detection region for both electrodes of the melf resistor 12, and outputs this area ratio to the determination control circuit 43 described later.

The judgment control circuit 43 takes in the area ratio, compares it with each of the detection regions 14, 15, 16 with a predetermined reference range (for example, a fixed value of the area ratio 0% to 40%) and takes it in. When the area ratio is above the reference range, the amount of solder 13 in that area is small,
It is judged that there is solder non-wetting or tempura. on the other hand,
If the area ratio is within the reference range, it is determined that the solder state in this area is normal.

It should be noted that this reference range is set based on the area ratio when the solder is normal and when it is defective based on experiments and past data, and is the same in each of the detection regions 14, 15 and 16. Then, which one of the judgment control circuits 43 is used?
If the area ratio here is outside the reference range even in one detection area,
It outputs a blinking signal for causing the warning lamp 6 to blink and a signal for displaying a defective section on the display 61, and a stop signal for stopping the driving of the XY robot.

The binarization circuit 41, the area extraction circuit 42, and the judgment control circuit 43 of this embodiment are collectively constituted by a CPU (central processing unit), a ROM (read only memory), and a RAM (random access memory). However, it may be processed by software. Instead of extracting the area ratio of the dark portion, the area ratio of the bright portion may be obtained and whether normal or defective may be determined.

Next, the operation of this example will be described. Figure 1
In, when the board 1 after the soldering process is carried to the carrying area of the inspection device, the CCD camera 3 captures each section of the board 1 as an image. This image is binarized and displayed on the monitor 5, and the operator visually extracts the area occupied by the bright portion and checks the solder defect by the size of this area. Meanwhile, the controller 4 automatically checks.

That is, the binarization circuit 41 binarizes the original image and distributes it to white and black, the area extraction circuit 42 calculates the area occupied by the pixels which are white (bright portion), and the above area ratio is calculated. Ask. Further, the judgment control circuit 43 compares this area ratio with the above-mentioned reference range. For example, FIG. 3 shows a normal state (a) and a defective state (b) to (d) of soldering. In the case of FIG. 3 (a), the solder 13 is attached over these regions, and The area occupied by the dark portion 17 in the regions 14 to 16 is relatively large, and the dark portion 1
The area occupied by 8 is smaller. Therefore, in the case of this example, in the determination control circuit 43, the area ratio of the bright portion is included in the above-mentioned reference range, and the soldering state of this figure (a) is determined to be normal. As a result, the blinking of the warning lamp 6 and the defective section display are not performed.

Next, in FIG. 3B, the tempura (the state where the electrode and the land are not connected via the solder), that is, the solder 13 does not adhere to the electrode and is solidified into a substantially hemispherical shape on the land 11. However, since the vicinity of such a solder apex is a flat surface, the reflected reflection is 180 ° and the reflected light is input to the camera 3. Therefore, this portion is the bright portion 18b.
Becomes

Therefore, in this case, in this example, the detection area 14,
16, the area occupied by the bright portion is small, and the judgment control circuit 43
In, the area ratio of the bright portion is included in the above-mentioned reference range, but since the position of the detection region 15 includes the apex portion of the solder, the area occupied by the bright portion 18b in this region is large, Since the ratio exceeds the reference range, the determination control circuit 43 blinks the warning lamp 6 and displays the defective section.

As described above, the total area occupied by the dark portion 17b is almost the same as the area of the dark portion shown in FIG. 3A,
Since the bright area in the tempura state is captured in the detection area 15, the solder defect can be reliably detected here. Further, FIG. 3C shows that there is a non-bonding of the solder in a part of the connecting portion between the electrode and the land 11, but such a non-bonding portion (the portion where the land 11 is exposed as it is).
Is a plane and is reflected by 180 ° in this case, and is input to the camera 3, so that the portion here is the bright portion 18c.

Therefore, in this case, in the detection areas 14 and 15, the area occupied by the bright portion is small, and in the determination control circuit 43, the area ratio of the bright portion 18c is included in the above-mentioned reference range. Since the position includes the solder non-adhesion portion, the bright portion 18c occupies a large area in this region, and the area ratio exceeds the reference range. Therefore, the determination control circuit 43 causes the warning lamp 6 to blink and the defective section to be defective. Display.

Thus, the total area occupied by the dark portion 17c is almost the same as the area of the dark portion shown in FIG. 3A,
Since the bright area 18c when the part is not attached is caught in the detection area 16, the solder defect can be reliably detected here. Further, FIG. 3 (d) shows the position shift of the melf resistor 12 (it is easy to roll because of the cylindrical shape), that is, the state where the entire solder moves to the lower side in the figure with the shift of the melf resistor 12, Since the part after the movement (the part where the land 11 is exposed) is a flat surface, it is reflected by 180 ° in this case and is input to the camera 3, so this part becomes the bright part 18d.

Therefore, in this case, the area occupied by the bright portion is small in the detection regions 15 and 16, and in the determination control circuit 43, the area ratio of the bright portion is included in the above-mentioned reference range. Contains the portion after the solder has moved, the area occupied by the bright portion 18d in this area is large, and the area ratio exceeds the reference range.
The judgment control circuit 43 blinks the warning lamp 6 and displays the defective section.

Thus, the total area occupied by the dark portion 17d is almost the same as the area of the dark portion shown in FIG. 3A,
Since the detection area 14 captures the bright portion when there is a positional deviation, a solder defect can be reliably detected here. When a defect occurs, the operator checks the unwetted portion (section) on the monitor 5 while looking at the display on the display 61. Further, since the substrate 1 is not conveyed by the output of the stop signal, it is possible to prevent the defective substrate from flowing in the subsequent process.

Although the detection area is divided into three in this example, the present invention is not limited to this and may be divided into two or four. The point is that the detection area may be divided and arranged in accordance with the shape of the solder, in a portion to which the solder should adhere, and in a portion where the solder shape remarkably changes when defective. Next, a second embodiment of the present invention will be described. FIG. 4 is an explanatory diagram showing the detection area of this example. The same parts as those in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted.

The difference from FIG. 3 is that the detection regions 20, 21, 22 are arranged in the lateral direction (B) of the melf resistor 12. That is, FIG. 4 shows a state in which the melf resistor 12 is moved in the right lateral direction due to vibrations during substrate transfer and is peeled off from the solder 13, but the detection region 22 is the end of the electrode to be soldered. Since they are arranged in the vertical direction (A) of the part, when such a defective state occurs,
The area ratio of the bright portion 24 in the detection region 22 becomes large. Therefore, this area ratio exceeds the reference range, and the judgment control circuit 43 can judge this as a defect.

Although the detection area 20 is arranged over the end portion of the land 11, only in this detection area 20, the reference range is set to, for example, 10% to 30%, and the area ratio is 10.
% (That is, the area of the dark portion 23 is large), the solder defect can be detected with higher accuracy by adding a process of determining that the solder is excessive and flows out of the land 11 to be defective.

Further, for each solder inspection, the quality of soldering is first determined in the inspection range of the first embodiment, and then the quality of soldering is determined in the inspection range of the second embodiment. A double check may be performed. Therefore, the inspection ranges 14, 15, 16 and 20, 21, 22
If any one of the area ratios exceeds the reference range, it is determined to be defective.

By performing the double check in this way,
The quality of soldering can be determined more accurately. still,
Although the electronic component is a melf resistor in the above description, the invention is not limited to this, and other components such as a box-shaped chip component can be applied.

[0034]

As described above, according to the present invention, the quality of soldering can be accurately determined without being affected by the variation in the shape of the solder.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a soldering inspection apparatus showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a soldering inspection apparatus showing an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing various soldering states.

FIG. 4 is a configuration diagram of a soldering inspection apparatus showing a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a conventional inspection device.

FIG. 6 is an explanatory diagram showing a state at the time of defective soldering.

[Explanation of symbols]

 1 ... Substrate 3 ... CCD camera 4 ... Controller 14, 15, 16 ... Detection area

Claims (1)

[Claims] 1. A soldering inspection method for determining the quality of soldering of an electronic component on a substrate in a predetermined area, wherein the predetermined area is divided into a plurality of areas according to the shape of the solder, and the divided areas are divided. A soldering inspection method, characterized in that the quality of soldering is judged based on the area ratio of the brightness of the reflected light in each area.