JPH05232041A - External appearance inspecting device and external appearance inspecting method for solder - Google Patents

Abstract

PURPOSE:To provide a means capable of judging accurately the quality of solder to adhere an electrode of a micro electronic part, such as, particularly, a microscopic capacitor chip onto a substrate. CONSTITUTION:An external appearance inspecting device is composed of the first light source 6 to radiate light from above toward an electronic part 5 soldered onto a substrate 1, the second light source 6 to radiate light from the oblique upper direction toward the length direction N of this electronic part 5 and a camera 8 arranged in the oblique upper direction on the opposite side of this second light source 7 so as to observe this electronic part 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder visual inspection apparatus and a visual inspection method, and irradiates an electronic component whose electrodes on both sides are soldered to a substrate with light from above and obliquely above.
This is observed by a camera obliquely above and the quality of the soldering state is determined.

[0002]

2. Description of the Related Art Electrodes for electronic components mounted on a board are generally soldered, but these include those with a poor soldering state such as no solder or non-wetting, and therefore After mounting on the board, a visual inspection of the solder is performed. Therefore, the present applicant has previously proposed a visual inspection method in a soldering state using a camera (Japanese Patent Laid-Open No. 21248/1990).
Publication).

In this method, as shown in FIG. 5, the optical scanning start line m1n1 is located inward of the position where the electrode Q of the electronic component is expected to exist, and the goal line m2n2 is located outward. Set the start line m1
Optical scanning from n1 toward goal line m2n2,
The end surface Qb of the electrode Q is detected by detecting the position where the brightness switches from bright to dark. Then, a check area A shown in FIG. 2 is set outside the detected end surface Qb, light is emitted from an upper light source 7, and the image is captured by an upper camera 6 to check the check area A. The quality of the soldering state has been determined from the image data.

[0004]

By the way, in recent years, substrates are becoming more and more dense, and along with this, electronic parts such as capacitor chips are becoming smaller and smaller, and one side is 0.5 mm or smaller. Ultra-small electronic components have also been mounted on boards. In such a microelectronic component, the electrodes on both sides are also extremely small. Therefore, when the image of this electrode is captured by the camera as in the conventional means, the brightness of this electrode is extremely unstable. As a result, it is difficult to accurately detect the end surface Qb, and the set position of the check area A is likely to be misaligned. As a result, there is a problem that the quality of the soldering state may be erroneously determined.
Also, since the amount of solder that adheres the electrodes to the substrate is extremely small, the check area A must be set to be extremely small. There was a problem that it was difficult to judge.

Therefore, it is an object of the present invention to provide means for sufficiently capturing image data of an electronic component, particularly a microminiature electronic component, and accurately determining the quality of the soldered state.

[0006]

To this end, the present invention provides a first light source which emits light from above toward an electronic component whose electrodes on both sides are soldered to a substrate, and the length of the electronic component. A second light source that emits light obliquely from above, and a camera that is provided obliquely above and opposite to the second light source and that observes the electronic component from above obliquely.

[0007]

According to the above structure, light is emitted from above and obliquely in the lengthwise direction of the electronic component, the image of the check area including the solder and the electrode is captured by the camera on the opposite obliquely upper side, and the image data is obtained. The quality of the appearance of the solder is judged from.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of an appearance inspection apparatus for electronic components, in which 1 is a substrate positioned on a positioning unit 4 composed of an X table 2 and a Y table 3, and an electronic component 5 is mounted on the upper surface thereof. .. The electronic component 5 is a capacitor chip having electrodes P and Q on both sides. Board 1
A ring-shaped first light source 6 is provided above the
A second light source 7 such as a halogen lamp is provided obliquely above the electronic component 5 in the length direction N. A camera 8 is provided obliquely above the second light source 7. In FIG. 2, the electrodes P and Q on both sides of the electronic component 5 are bonded to the electrodes 11 of the substrate 1 with solder 13. Next, a method for inspecting the appearance of solder by the above device will be described.

FIG. 3A is an overall image of the electronic component 5 observed obliquely from above by the camera 8, and FIG. 3B is a side view of the observation state. In FIG. 3A, A is a check area, which is set large so as to include the electrodes Q and the solder 13. By setting the check area A large in this way, a sufficient image for the quality judgment can be obtained. Data is available. The size and position of the check area A are set based on known electronic component coordinate data and dimension data. The electrodes P, Q and the solder 13 are metal and their surfaces are mirror surfaces, and strongly reflect light.

In FIG. 3B, L1 to L4 are lights emitted from the upper light source 6, and L1 'and L2' are lights emitted from the obliquely upper light source 7. The solder 13 is a good product because the electrode Q is firmly adhered to the electrode 11 of the substrate 1. The light L1 emitted perpendicularly to the electrode Q is reflected right above and does not enter the camera 8, so that it is observed dark. Similarly, the light L2 that has entered the top of the solder 13 is also reflected directly above and does not enter the camera 8, so it is observed dark. The light L3 incident on the inclined surface near the top of the solder 13 is reflected obliquely upward and enters the camera 8, so that it is observed brightly, and the light L4 incident on the lower portion of the solder 13 is reflected obliquely downward and reflected by the camera 8. It is not incident on and is observed dark. Further, the light L1 ′ irradiated on the electrode Q from obliquely upward is reflected obliquely upward and is incident on the camera 8 and is observed brightly, but the light L2 ′ incident on the solder 13 is reflected upward and is reflected on the camera 8. Does not enter. The upper surface 5a of the electronic component 5 has a dark color, and therefore the light incident on this upper surface is absorbed, so that it is observed as dark by the camera 8. Similarly, since the substrate 1 has a dark color and absorbs light, and the electrode 11 is a shadow of the electronic component 5 and the solder 13, it is observed dark by the camera 8.

FIG. 3C shows the camera 8 as described above.
The image of the check area A taken in is shown.
As described above, since the light L1 ′ is incident on the camera 8, the electrode Q is brightly observed, and since the light L3 is also incident on the camera 8, the upper portion of the solder 13 is brightly observed in a half-moon shape. On the other hand, since the light L4 does not enter the camera 8, the solder 13
The lower part of is observed dark.

FIG. 3D shows a luminance cumulative curve a on the vertical axis YL of FIG. 3C, and a differential curve b of a falling portion a'of the cumulative curve a. Falling part a '
The gradient is a little gentle and therefore the differential curve b has a mountain shape. The differential curve b has the positive and negative sides reversed.

FIGS. 4A and 4B show defective products without the solder 13. In this case, as shown in FIG. 4B, the light L1 ′ radiated on the electrode Q from obliquely above is reflected by the camera 8
However, the light L1 emitted from directly above is reflected directly above and does not enter the camera 8. Therefore, the image is as shown in FIG. 4C, and only the electrode Q is bright. The luminance characteristic is as shown in FIG. 4 (d), and the falling portion a'of the cumulative curve a of luminance is almost vertical, and therefore the differential curve b stands upright at an acute angle.

5A and 5B show solder non-wetting (defective product). In this case, only the light L1 ′ emitted obliquely from above the electrode Q and the light L1 emitted from the above to the inclined portion on the right side of the solder 13 are incident on the camera 8, and the other light is reflected right above or sideways. Does not enter the camera 8. Therefore, the image is as shown in FIG. 5 (c), and the luminance characteristic is as shown in FIG. 5 (d). in this case,
As shown in the figure, the cumulative curve a has two peaks, and two differential curves b1 and b2 are obtained. This one is also shown in Figure 3.
Similar to that shown in (d), the falling portion a ′ is almost vertical, and therefore the differential curve b1 is upright at an acute angle.

The quality of the soldered state can be determined by the image data of the luminance distribution shown in FIGS. 3 (c) to 5 (c) or FIG. 3 (d).
~ This is performed based on the cumulative curve a or the differential curve b shown in Fig. 5 (d). The quality determination based on the brightness distribution is performed as follows, for example. That is, the brightness distribution of the check area A shown in FIG. 3C is registered in the computer as a master pattern, and the image of the check area obtained by observing the electronic component 5 to be inspected is matched with this master pattern. If the matching is high, it is determined as a good product, and if the matching rate is low, it is determined as a defective product. Of course, a method similar to the method disclosed in JP-A-2-21248, that is, the quality may be determined from the ratio of the bright portion and the dark portion, and various determination methods can be considered.

The quality judgment based on the cumulative curve a is performed by the magnitude of the slope of the falling portion a '. Of course, FIG.
The cumulative curve a in (d) may be registered in the computer as a master curve, and the quality curve may be determined by comparing the cumulative curve obtained by observing the electronic component 5 to be inspected with this master curve. .. The quality determination based on the differential curve b is performed based on the sharpness. Of course, this one also
The differential curve b in FIG. 3D may be registered in a computer as a master curve, and the differential curve obtained by observing the electronic component 5 to be inspected may be compared with this master curve. Of course, in the case of the solder 13 shown in FIG.
Since the cumulative curve a has two peaks and two differential curves b1 and b2 exist, it may be determined as a defective product based on this feature.

As described above, there are several pass / fail judgment methods.
The quality may be determined by any one method, and the quality may be comprehensively determined by a plurality of methods.
According to the results of experiments conducted by the present inventor, the differential curve b is the easiest to distinguish between good solder and bad solder, and the quality determination can be performed most accurately. Of course, the method of processing the image data shown in FIGS. 3 (c) to 5 (c) is not limited to the method shown in FIGS. 3 (d) to 5 (d). It is possible to further consider whether or not to use it as the pass / fail judgment data.

[0018]

As described above, according to the present invention, the check area can be set large, sufficient image data can be obtained, and the quality of the soldering state can be accurately determined. Even in the case of a small amount of solder that adheres the electronic component to the substrate, it is possible to obtain sufficient image data and make a pass / fail judgment.

[Brief description of drawings]

FIG. 1 is a perspective view of an appearance inspection apparatus according to the present invention.

FIG. 2 is a side view of the appearance inspection apparatus according to the present invention.

3A is a plan view of an inspection state according to the present invention, FIG. 3B is a sectional view of the inspection state according to the present invention, FIG. 3C is an image diagram according to the present invention, and FIG. 3B is a luminance characteristic diagram according to the present invention.

4A is a plan view of an inspection state according to the present invention, FIG. 4B is a sectional view of the inspection state according to the present invention, FIG. 4C is an image diagram according to the present invention, and FIG. 4B is a luminance characteristic diagram according to the present invention.

5A is a plan view of an inspection state according to the present invention, FIG. 5B is a sectional view of the inspection state according to the present invention, FIG. 5C is an image diagram according to the present invention, and FIG. 5B is a luminance characteristic diagram according to the present invention.

[Explanation of symbols]

 1 substrate 5 electronic component 6 first light source 7 second light source 8 camera 13 solder Q electrode

Claims (2)

[Claims] 1. A first light source that emits light from above toward an electronic component whose electrodes on both sides are soldered to a substrate, and a light source that emits light obliquely in the longitudinal direction of the electronic component. 2. A solder visual inspection apparatus comprising: a second light source; and a camera provided obliquely above the second light source, the camera observing the electronic component obliquely above. 2. Light is emitted from above and obliquely upward in the lengthwise direction of the electronic component toward the electronic component soldered on the substrate, and solder is applied by the camera on the opposite diagonal side. And a method for inspecting the appearance of solder, wherein an image of a check area including electrodes on the side of an electronic component is captured and the quality of the appearance of the solder is determined from the image data.