JP2004151010A - Soldering inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve precision of quality determination of soldering. <P>SOLUTION: This device is equipped with a ring-shaped light 1 for irradiating a soldered spot 10 with light, a CCD camera 2 for imaging a region including the soldered spot where a bright part is formed by irradiation light, and a control device 4 for determining the quality of soldering from the imaged image. The CCD camera 2 is arranged with a position relation for imaging the region including the soldered spot 10 from the direction tilted at a prescribed angle from the vertical direction on the substrate surface. The control device 4 can discriminate highly accurately the solder wetting state to a lead by performing combined determination of each determination of the position and the area of the bright parts on the lands on the lead tip side and on the lead side face side, to thereby perform quality determination of soldering highly accurately. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a soldering point inspection device.
[0002]
2. Description of the Related Art Conventionally, solder is printed on predetermined lands (electrode portions) of a printed circuit board, electronic components and the like are temporarily fixed thereon, and the printed circuit board is passed through a reflow furnace to solder the electronic components and the like. A reflow soldering method is used.
[0003]
As a method for inspecting a soldered product as described above, for example, a method described in Patent Document 1 is known. In this inspection method, light is sequentially radiated at different angles to a soldering location using multi-stage illumination, and the soldering location is imaged from a vertical direction on the substrate surface. Based on the image data, a reflected light distribution corresponding to each irradiation step of the solder fillet formed by soldering is obtained. Then, a ridge line corresponding to the appearance shape of the solder fillet is estimated based on the reflected light distribution, and the quality of the soldering is determined from the ridge line data.
[0004]
An inspection method described in Patent Document 2 is also known. In this inspection method, all the solder fillets on the substrate are irradiated with a beam, and reflected light from all the solder fillets is received. Then, based on the total received light amount of the reflected light, the scum of the solder is detected.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 10-26084
[Patent Document 2]
JP-A-63-177042
[Problems to be solved by the invention]
However, in each of the inspection methods of Patent Literature 1 and Patent Literature 2, the imaging direction or the irradiation direction is set in a direction perpendicular to the substrate surface. For this reason, in particular, the irradiation light or the reflected light may be blocked by the leads of the electronic component, and the shape of the solder fillet in the vicinity of the leads may not be accurately detected.
[0008]
The present invention has been made in view of the above points. In other words, by imaging the soldering position from a viewpoint obliquely inclined at a predetermined angle from the vertical direction of the substrate surface, it is possible to accurately grasp the state of solder wetting to the lead, and determine whether soldering is good or bad. An object of the present invention is to provide an inspection device with improved accuracy.
[0009]
[Means for Solving the Problems]
The soldering inspection device according to claim 1, wherein when soldering a lead of the electronic component to a land of the substrate, the soldering inspection device inspects whether the soldering is good or not. Irradiating light irradiating means, and light irradiating from the light irradiating means, in a state where a bright portion is formed on a solder surface at the soldering location, imaging means for imaging an area including the soldering location, A determination unit that determines whether soldering is good or not from an image captured by the imaging unit, wherein the light irradiation unit and the imaging unit are configured such that an angle formed between the solder surface and the substrate surface is smaller than a predetermined angle. The solder surface is a bright portion, and the imaging means is arranged in a positional relationship for imaging an area including a soldering point from a direction inclined at a predetermined angle from the vertical direction of the substrate surface. The determining means determines the quality of the soldering based on a combination of the position of the bright portion on the land on the lead tip side and the position of the bright portion on the land on the lead side surface. And
[0010]
In this manner, the image pickup means and the light irradiation means are arranged so that the image pickup means can pick up an image of the soldered portion from a direction inclined by a predetermined angle from the vertical direction. For this reason, it is possible to obtain image data that captures the state of solder wetting on the leads by the imaging means. Whether the wet state is good or bad based on the image data is determined based on the position of the bright portion appearing on the solder surface when the angle formed with the substrate surface is smaller than a predetermined angle. That is, when the solder wets the lead and is normally soldered, the solder has an inclined angle toward the upper surface of the lead. On the other hand, when the solder is funnel with respect to the lead, a substantially flat portion characteristically appears around the lead. Therefore, by combining the positions of the bright portions on the side surface and the tip side of the lead, it is possible to determine the state of solder wetting on the lead with high accuracy, and thus to judge the quality of soldering with high accuracy.
[0011]
The inspection device according to claim 2 is characterized in that the determining means determines that the soldering is defective when a bright portion exists on the land on the side surface of the lead.
[0012]
When the lead hits the solder, such as when the lead is lifted off the land, the surface of the solder becomes flat on the land on the side surface of the lead. Therefore, the quality of the soldering can be determined based on whether there is a bright portion on the land on the side surface of the lead.
[0013]
4. The soldering inspection device according to claim 3, wherein the determination unit is configured such that a distance from a top end of the lead to a bright portion position on the land is equal to or greater than the lead thickness, and a tip side of the lead and a side surface of the lead. 5. When there is no bright portion in the nearby land portion, the soldered portion is determined to be defective.
[0014]
According to the inspection device of the third aspect, it is possible to determine the wetting state of the solder on the tip side of the lead. In other words, if the distance from the top end of the lead to the bright solder part is greater than the lead thickness, the solder will not wet the tip end of the lead and form a flat surface on the land, or the amount of solder itself will be extremely small. May be slight. Therefore, in such a case, it is determined whether there is a bright portion near the lead tip side and near the lead side surface, in other words, the inclination angle of the solder fillet at that portion. This makes it possible to determine with high accuracy whether a solder fillet is formed on the lead.
[0015]
5. The soldering point inspection apparatus according to claim 4, wherein the imaging unit captures an image of the region including the soldering point from a plurality of angular positions including at least an angular position facing the tip of the lead. .
[0016]
On the leading end side of the lead, the distance from the leading end of the lead upper surface to the bright portion is compared with the lead thickness, so that it is necessary to accurately draw these from image data. For this reason, it is preferable that the imaging means captures an image of the soldering location from a position facing the tip of the lead. Furthermore, as described above, in the present invention, the quality of soldering is determined based on the position of the light portion of the land on the side surface of the lead, so that even at an angular position different from the angular position facing the tip of the lead, the soldering position is determined. It is preferable to take an image.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the configuration of the soldering inspection apparatus 100 according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram showing a configuration of a soldering inspection apparatus 100 according to the present invention.
[0018]
The soldering inspection device 100 of the present invention shown in FIG. 1 includes a ring-shaped light 1, a CCD camera 2, an imaging angle setting device 3, and a control device 4. Reference numeral 10 denotes a soldering location 10, which is an inspection object.
[0019]
The ring-shaped light 1 corresponds to a light irradiation unit described in the claims. The light 1 is a lighting device for irradiating light to a soldering location 10 to be inspected. The ring-shaped light 1 has a circular shape as shown in FIG. 1, and a soldering location 10 to be inspected is installed substantially vertically below a center point of the circle, and an inspection area of the soldering location 10 is set. Light is emitted from all around the ring-shaped light 1.
[0020]
FIG. 2 is an explanatory view showing a state of light irradiation of the ring-shaped light 1. In FIG. 2, the irradiation outside angle a is set to, for example, 84 °, and the irradiation inside angle b is set to 45 °. Then, the ring-shaped light 1 irradiates a range excluding the range of the cone formed by the irradiation inner angle b from the cone formed by the irradiation outer angle a.
[0021]
As described above, in the present embodiment, the light irradiating means is shown as a ring-shaped lighting device, but the present invention is not limited to this. If there is, its shape does not matter.
[0022]
The CCD camera 2 is a photographing machine for photographing the soldering location 10 illuminated by the ring-shaped light 1, and is an imaging means described in the claims. The CCD camera 2 is a digital still camera, and a captured image is transmitted as digital data to a control device 4 described later.
[0023]
The imaging angle setting unit 3 is a setting unit that determines an imaging angle of the CCD camera 2. The imaging angle set by the imaging angle setting unit 3 is a tilt angle that takes an angle of α with respect to a vertical line (Z axis in FIG. 1) from the center of the ring-shaped light 1 to the soldering point 10 as the test object. And a rotation angle that takes an angle of γ with respect to an extension line (X axis in FIG. 1) of the lead of the soldering portion 10 in the longitudinal direction. Both can be set to any angle. However, when capturing a plurality of images of the common soldering location 10, the inclination angle α is the same, and only the rotation angle (γ) is changed.
[0024]
The control device 4 includes an image processing unit (not shown) that processes an image transmitted from the CCD camera 2, and a determination unit (not shown) that determines whether the soldering state of the soldering location 10 is good based on the processed image. , And a display unit (not shown) for displaying the determination result.
[0025]
The control device 4 is a computer including a well-known CPU, ROM, RAM, a signal input / output unit, and the like, and is connected to the ring light 1, the CCD camera 2, and the imaging angle setting unit 3.
[0026]
The image data transmitted from the CCD camera 2 is temporarily stored in the image processing unit. The image processing unit performs binary processing (black and white processing) on the stored image data and transmits the processed data to the determination unit.
[0027]
The discriminating unit performs a pass / fail determination process based on the binary-processed image data transmitted from the image processing unit using a pass / fail determination program for a soldering location, which will be described later, and determines the acceptability of the soldering location. The determination result information is transmitted to the display unit.
[0028]
The display unit includes a well-known liquid crystal display device, a cathode ray tube (CRT) display device, and the like. By displaying the determination result information transmitted from the determination unit, the quality of the soldered portion 10 to be inspected is notified.
[0029]
The control device 4 not only notifies the soldering portion 10 of the quality of the soldering portion 10 on the display portion, but also automatically removes the electronic component having the soldering portion in the case of failure. (Shown), a signal output unit for notifying the failure may be provided.
[0030]
Next, patterns of non-defective products and defective products at the soldering locations 10 to be inspected will be described with reference to FIGS. FIG. 3 shows a case where the soldering portion is imaged at an inclination angle α = 45 ° with the general solder fillet shape and the rotation angle γ being 0 °, 45 °, and 90 ° when the soldering shape is normal. Are images schematically shown.
[0031]
In each of the schematic views of the soldering location shown in FIG. 3, the area drawn with diagonal lines with a narrow pitch is a bright portion with a large amount of reflected light. In the present embodiment, the illumination angle of the ring-shaped light 1 is set to the external illumination angle a = 84 °, the internal illumination angle b = 45 °, and the inclination angle α of the CCD camera 2 is set to 45 °. The surface portion of the solder fillet at an angle of 1.5 to 11.25 ° or 33.75 to 43.5 ° is the bright region.
[0032]
The normal pattern 1 has a small amount of solder and a small amount of solder wetting. In this type, the solder does not spread to the land end, and an observable land surface exists between the foot of the solder fillet and the land end. As a result, the land becomes an incomplete bright part due to light irradiation. The shape of the bright portion has characteristics similar to the defective pattern 3 described later.
[0033]
The normal pattern 2 is an ideal type in both the solder amount and the solder wetting amount.
[0034]
The normal pattern 3 has a large amount of solder, and the shape of the solder is substantially convex along the longitudinal direction of the lead.
[0035]
The normal patterns 4 and 5 are intermediate types between the normal patterns 2 and 3, and the difference between the normal patterns 4 and 5 depends on the length of the land.
[0036]
Next, the features of the defective patterns 1 to 3 will be described.
[0037]
FIG. 4 shows, in the same manner as FIG. 3, defective patterns in which the soldering shape is abnormal and the soldering is defective.
[0038]
Defective pattern 1 is a type in which the leads are lifted off the lands and the solder forms fillets under the leads. In this type, a fillet including a surface having an angle of 1.5 ° to 11.25 ° and an angle of 33.75 ° to 43.5 is generated on the land on the side surface or the tip side of the lead. That is, this surface is a portion that becomes a bright portion by light irradiation. Also, the fact that the solder is not wetted on the leads allows the end faces of the leads to be observed, which is a difference from the above-described normal patterns.
[0039]
The defective pattern 2 is of a type in which the lead repels the solder and the solder swells on lands around the lead. Therefore, a difference from each normal pattern is that solder fillets having protrusions are formed on the lands on the side surfaces of the leads and on the lands on the leading ends of the leads.
[0040]
The vicinity of the top of the convex portion includes an angle of 1.5 ° to 11.25, and this portion is a portion that becomes a bright portion by light irradiation.
[0041]
The defective pattern 3 is a type in which the solder is not present on the land or is extremely small. In this type, the entire surface of the land can be observed. Since this portion is horizontal to the substrate, that is, 0 °, the lower limit angle to be a bright portion is 1.5 ° or less, but since the angle difference is small, it may be incomplete but a bright portion. The feature of the shape of this incomplete bright part may be similar to the normal pattern 1 described above.
[0042]
As described above, each of the defective patterns 1 to 3 has a surface that is almost flat to almost flat, and the defective patterns 1 to 3 are normally determined depending on the position and the size of the light portion formed on the substantially flat surface. It can be identified from patterns 1 to 5.
[0043]
FIG. 5 is a flowchart showing a process related to the quality judgment of the soldering portion 10 using the optical common feature of each of the defective patterns 1 to 3 in the control device 4 of the soldering inspection device 100 having the above-described configuration.
[0044]
In step S1 of FIG. 5, two binary processed images captured at the left and right side surfaces of the lead of the soldering portion 10 to be inspected, that is, at rotation angles γ = 90 ° and −90 ° are read. In step S2, the image at the tip of the lead, that is, the binary-processed image with the rotation angle γ = 0 ° is read. In step S3, the areas of the bright portions existing on the left and right side portions are measured, and in step S4, the area data of the bright portions on the side faces of the lead for discrimination for the threshold value is read.
[0045]
Then, in step S5, the data of the left and right bright area measured in step S3 is compared with the threshold area data read out in step S4, and one of the measured bright area data of the left and right side portions is measured. However, if the area is larger than the threshold area data, it corresponds to the bright portion feature of the defective patterns 1 and 2, so that the soldered portion 10 to be inspected is determined to be defective. Then, the process proceeds to step S16, and the fact is displayed on the display unit.
[0046]
If both of the bright area data of the left and right side portions are smaller than the threshold area data, that is, if the data is a soldering location having the characteristics of the normal patterns 1 to 4 and the defective pattern 3, the process proceeds to step S6.
[0047]
In the process of step S5, the above-described defective patterns 1 and 2 can be identified. That is, as shown in FIG. 3, in any of the normal patterns 1 to 5, bright portions do not occur on the left and right side surfaces of the lead. Therefore, when a bright portion having a threshold area or more is detected in the left and right side surfaces of the lead, it can be determined that the pattern corresponds to the defective patterns 1 and 2. At this time, whether or not the bright portion area is equal to or larger than the threshold area, rather than the presence or absence of the bright portion itself, is determined by the presence of the solder fillet shape according to each normal pattern. This is because the area is clear but there is a bright part. FIG. 4 shows a target range for determining the bright area of the left and right side surfaces of the lead.
[0048]
In step S6, the distance from the upper end of the lead at the soldering position to the bright portion of the solder fillet is measured. In step S7, the lead thickness data is read. In step S8, the distance measurement value is compared with the lead thickness data. .
[0049]
In this step, if the distance value is equal to or larger than the lead thickness data, the solder may not be wet with respect to the lead end. Such a relationship corresponds to the bright portion characteristics of the normal pattern 1 and the defective patterns 1 to 3. However, the defective patterns 1 and 2 are determined in principle to be soldering defects in step S5, so that the processes in steps S9 to S11 are performed to distinguish the normal pattern 1 from the defective pattern 3. Although the defective pattern 3 does not originally have wet-up solder, the normal pattern 1 is wet-up only with a small wet-up area. However, since the amount of wet solder is small, a land portion can be observed, and the land portion becomes a bright portion, so that it is difficult to distinguish the defective pattern 3 from the defective pattern.
[0050]
Based on the image of the lead tip, the area of the bright part in the land near the lead tip and on the side surface of the lead is measured in step S10. FIGS. 6A and 6B show target ranges for measuring the bright area. In step S11, the measured area data is compared with the read threshold area data. If the measured area data is larger than the threshold area data, it indicates that the land portion, which is a feature of the bright portion of the defective pattern 3, is a bright portion. The attachment location 10 is determined to be defective, and that fact is displayed on the display unit.
[0051]
If it is determined in step S8 that the measured distance is equal to or less than the lead thickness data, and if it is determined in step S11 that the measured area of the bright part is smaller than the discrimination area data, the process proceeds to step S12. In step S12, a deviation threshold, which is an allowable limit value of deviation between the read and the land, is read. In step S13, the deviation width between the lead and the land is measured. Then, the deviation width measured in step S14 is compared with a threshold value of the deviation width. If the measured deviation width is large, the process proceeds to step S16, and if the measured deviation width is small, the process proceeds to step S15. (See FIG. 7) The threshold value of the deviation width is suitably, for example, about half of the lead width.
[0052]
This further improves the accuracy of the quality determination of the soldering location 10.
[0053]
After the display of the determination of normality or failure in step S15 or step S16, it is determined in step S17 whether or not there is a next soldering location 10 that needs to be determined. If there is, the process returns to step S1. If not, the flow ends.
(Modification)
Next, a modified example of the soldering inspection apparatus 100 according to the above-described embodiment will be described. The soldering inspection device 100 is used for measuring a bright portion of a soldered portion, for example, an image of a lead side surface or a lead end portion, due to bleeding or blurring when an image taken from an opposite direction is subjected to binary processing. It may be difficult to accurately measure the bright area.
[0054]
For this reason, as shown in FIG. 3, one to several images whose imaging angles are changed in the horizontal direction are taken, the areas of bright portions appearing in these images are measured, and the average value is used as the final value. By setting the area of the bright part, it is possible to reduce a measurement error due to measurement using only one facing image.
[0055]
Note that, as described above, the measurement site for reducing the error of the measured value of the bright area using a plurality of images obtained by imaging the same site at different horizontal imaging angles is not limited to the side surface.
[0056]
In this manner, by using a plurality of images, it is possible to obtain the accurate area of the bright portion, and thus it is possible to obtain more accurate bright portion area data. Therefore, it is possible to determine the quality of the soldering portion 10 with high accuracy. become.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a schematic configuration of a soldering inspection apparatus 100 of the present invention.
FIG. 2 is an explanatory diagram for explaining a relationship between an outer angle a and an inner angle b of light emitted by the on-ring light 1. FIG.
FIG. 3 is an explanatory diagram showing a normal pattern of a soldering portion 10 to be inspected.
FIG. 4 is an explanatory diagram showing a defective pattern of a soldering portion 10 to be inspected.
FIG. 5 is a flowchart illustrating a determination process of determining whether the soldering portion 10 is good or bad according to the present invention.
FIG. 6 is an explanatory diagram showing bright portion characteristics of a normal pattern 1 and a defective pattern 3 in an image obtained by imaging a lead end from a side surface.
FIG. 7 is an explanatory diagram showing a state of a lead shift in an image captured with the lead end portions facing each other.
[Explanation of symbols]
1 ring light (light irradiation means)
2 CCD camera (imaging means)
3 imaging angle setting unit (imaging means)
4 Inspection device body (judgment means)
10 soldering location 100 soldering inspection device

Claims (4)

When the lead of the electronic component is soldered to the land of the substrate, an inspection device for inspecting the quality of the soldering,
Light irradiation means for irradiating light to the soldered portion of the lead,
By light emitted from the light irradiating means, in a state where a bright portion is formed on the solder surface at the soldering location, imaging means for imaging an area including the soldering location,
Determining means for determining whether soldering is good or not from the image captured by the image capturing means,
When the angle between the solder surface and the substrate surface is smaller than a predetermined angle, the light irradiating unit and the imaging unit may be configured such that the solder surface is a bright portion, and the imaging unit is in a vertical direction of the substrate surface. It is arranged in a positional relationship of imaging an area including a soldering point from a direction inclined by a predetermined angle from,
The determining means determines the quality of the soldering based on a combination of the position of the bright portion on the land on the lead tip side and the position of the bright portion on the land on the lead side surface. Soldering inspection equipment. 2. The soldering inspection device according to claim 1, wherein the determining unit determines that the soldering is defective when a bright portion exists on the land on the side surface of the lead. 3. The determination means, when the distance from the top end of the lead to the bright portion position on the land is equal to or greater than the lead thickness, and if there is no bright portion in the land near the lead side and the lead side surface, The soldering inspection device according to claim 1, wherein the soldering portion is determined to be defective. The soldering device according to claim 1, wherein the imaging unit captures an image of the area including the soldering location from a plurality of angular positions including at least an angular position facing the tip of the lead. Inspection equipment.

Images