JP2002071578A - Visual inspection apparatus and method of visually inspecting printed wiring board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a visual inspection apparatus high in general-purpose property and superior in detection accuracy. SOLUTION: The visual inspection apparatus 1 is provided with an image pickup means 5 to pick up the images of sections to be inspected 3 and 4 in the surface of a body to be inspected 2, and first and second luminaires 6 and 7 to irradiate the sections to be inspected 3 and 4 with light. The irradiation angle of the second luminaire 7 is higher than that of the first luminaire 6. Switching means 8a, 11, and 15 selectively switch between the luminaries 6 and 7 according to the shape properties of the sections to be inspected 3 and 4. The defectiveness/non-defectiveness of the sections to be inspected 3 and 4 is inspected by processing the images obtained by the image pickup means 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an appearance inspection apparatus for inspecting the quality of a part to be inspected by processing an image of the object to be inspected obtained by an imaging means, and a method for inspecting the appearance of a printed wiring board using the same. It is about.

[0002]

2. Description of the Related Art Conventionally, a package formed by bonding a large number of conductive balls to pads formed on the surface of a printed wiring board for mounting a semiconductor, a so-called BGA (Ball Grid Arra)
A package called y) is well known. This type of package is required to have higher density, higher function, finer and more terminals, and accordingly the number of conductive balls as external connection terminals tends to increase year by year. Therefore, it can be said that efficiently inspecting the quality of the conductive balls at the time of manufacturing the package is an extremely important task in improving productivity. In recent years, visual inspection using image processing technology has been performed instead of the conventional visual inspection.

An appearance inspection apparatus for performing such an appearance inspection is provided with a CCD camera for imaging a solder ball as a part to be inspected, and a low-angle ring illumination for irradiating light to a printed wiring board. In such an apparatus, an image obtained by the CCD camera is processed to inspect the quality of the shape of the solder ball and the like. More specifically, for example, the presence or absence of displacement, the presence or absence of scratches and dents,
The presence or absence of size variation is inspected.

[0004]

However, while the conventional visual inspection apparatus is effective for inspecting a conductive ball having a three-dimensional shape, it is not suitable for inspecting a part to be inspected having a different shape. Was unsuitable. For example, when the above-described apparatus is directly used for inspecting a ball pad having a planar shape, there is a disadvantage that the inspection accuracy is low, and the apparatus has been poor in versatility. Therefore, there is a problem that a visual inspection device dedicated to ball pad inspection must be purchased separately.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a visual inspection apparatus having high versatility and excellent inspection accuracy.

[0006]

Means for Solving the Problems In order to solve the above problems, the inventors of the present invention have conducted intensive research. First, while paying attention to the form of illumination used in the apparatus, the shape characteristics of the inspected portion are not changed. We have gained new knowledge that when it changes, the lighting suitable for it also changes. Also, with only one type of lighting,
It was also found that it was not possible to sufficiently cope with the case where the shape of the inspected part was significantly different. Then, the inventor of the present application has further developed this based on the above findings, and has finally arrived at the following invention.

That is, in order to solve the above-mentioned problems, according to the first aspect of the present invention, there is provided an image pickup means for picking up an image of a portion to be inspected on a surface of an object to be inspected; A visual inspection apparatus that processes an image obtained by the imaging unit and inspects the quality of the inspected portion, wherein the first illumination, a second illumination having an irradiation angle higher than the first illumination, A gist of the invention is an appearance inspection apparatus characterized by comprising switching means for selectively switching between the two illuminations according to the shape properties of the inspected part.

According to a second aspect of the present invention, in the first aspect, the first illumination is a low-angle ring illumination and the second illumination is a low-angle ring illumination.
The illumination is a high-angle coaxial illumination located at a position farther from the object to be inspected than the first illumination.

According to a third aspect of the present invention, in the second aspect, the second illumination reflects incident light from a light source in the direction of the inspection object and reflects reflected light from the inspection object to the inspection object. A half mirror for transmitting light is provided on the imaging means side, and the half mirror is provided so as to be retractable from the path of the reflected light.

According to a fourth aspect of the present invention, there is provided the visual inspection apparatus according to any one of the first to third aspects, wherein the second illumination is operated only to activate the second illumination on the printed wiring board. Inspecting the inspected portion, operating only the first illumination, and inspecting the first inspected portion on the printed wiring board, the shape being more three-dimensional than the first inspected portion. The gist is a method for inspecting the appearance of printed wiring boards to be performed.

According to a fifth aspect of the present invention, in the fourth aspect, the first inspected portion is a ball for external connection, and the second inspected portion is a ball pad to which the ball is bonded. There was.

The "action" of the present invention will be described below. According to the first to fifth aspects of the present invention, the inspection can be performed by selectively switching the two types of illumination by the switching unit. In the case of an inspected part having a planar shape, the amount of light reflected on the imaging means side increases when light is irradiated from illumination having a high illumination angle. Therefore, by operating only the first illumination, it is possible to accurately inspect the quality of a part to be inspected having a three-dimensional shape (for example, a ball for external connection). Further, by operating only the second illumination, it is possible to accurately inspect the quality of another inspected portion (for example, a ball pad or the like) having a planar shape.
Further, according to the present invention, it is possible to inspect two types of inspected parts having different shapes and properties with one apparatus, so that a highly versatile appearance inspection apparatus can be obtained.

According to the third aspect of the present invention, since the half mirror can be retracted from the path of the reflected light, the loss of the reflected light due to the interposition of the half mirror is eliminated, and the light is bright and excellent in resolution. A clear image can be obtained. Therefore, even if the number of inspected parts is large and minute, it can be inspected easily and with extremely high accuracy.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An appearance inspection apparatus 1 embodying the present invention and an appearance inspection method of a printed wiring board 2 using the same will be described in detail with reference to FIGS.

As shown in FIG. 1, an appearance inspection apparatus 1 according to the present embodiment includes two types of inspected portions (a solder ball 3 and a solder ball joined to each other) on the surface of a printed wiring board 2 which is an object to be inspected. This is for automatically inspecting the quality of the ball pad 4). That is, the printed wiring board 2 forms an E-BGA type package. This visual inspection device 1 is provided with a CC
D camera 5, low-angle ring illumination 6 as first illumination,
A high-angle coaxial illumination 7 as a second illumination, a control computer 8, an XYZ table 9, a supporting frame (not shown), and the like are provided.

The CCD camera 5 is supported by a frame with the lens 5a facing downward. The optical axis of the CCD camera 5 is parallel to the vertical direction of the printed wiring board 2. The CCD camera 5 is electrically connected to the control computer 8. Therefore, the image data signal obtained by the CCD camera 5 is taken into the CPU 8a in the control computer 8, where it is processed based on a predetermined program.

The XYZ table 9 is provided below the CCD camera 5. On this table 9, the printed wiring board 2 which is an object to be inspected is placed. Then, by appropriately moving the table 9 in a predetermined direction, adjustment of the imaging position, adjustment of the focus, and the like are performed. The printed wiring board 2 may be fixed to the table 9 by, for example, vacuuming at this time. Of course, the CCD camera 5 side may be appropriately moved to adjust the imaging position and the like.

The low-angle ring illumination 6 is an illumination having a ring-shaped light-emitting body therein, and is supported by a frame at a position above the printed wiring board 2 and at a position close to the printed wiring board 2. . Further, light can pass through the center of the low-angle ring illumination 6. The low-angle ring light 6 is electrically connected to a control computer 8 via a driving means 10 for the low-angle ring light 6. The control computer 8 has a built-in first switch 11 which constitutes a part of the switching means. Specifically, the drive means 10 and the CPU 8a are connected via the first switch 11. Then, the first switch 11
Is turned on / off by a signal from the CPU 8a which is also a part of the switching means. As a result, the low-angle ring illumination 6 is turned on or off.

The high-angle coaxial illumination 7 comprises a low-angle ring illumination 6
Illumination with a higher irradiation angle. The lamp 12 as a light source constituting the high-angle coaxial illumination 7 is disposed at a position apart from the side of the light reflection unit 13 also constituting the high-angle coaxial illumination 7. This lamp 12
Is electrically connected to the control computer 8 via the driving means 14 for the high-angle coaxial illumination 7. The control computer 8 has a built-in second switch 15 which constitutes a part of the switching means. Specifically, the drive unit 14 and the CPU 8a are connected via the second switch 15. The second switch 15 is connected to the CPU 8
It is turned on / off by a signal from a. As a result, lamp 1
2 is turned on or off, and the high-angle coaxial illumination 7 is substantially switched to an activated state or an activated state.

The light reflecting unit 13 constituting the high-angle coaxial lighting 7 is more printed circuit board 2 than the low-angle ring lighting 6.
It is supported by the frame at a position (high position) far from the camera. The light reflecting unit 13 is arranged on the optical axis of the CCD camera 5.

The light reflecting unit 13 of this embodiment includes a prism 16, a half mirror 17, a reflecting mirror 18, an actuator 19 for retracting the half mirror, and an actuator driving means 20. The prism 16 is made of a light-transmitting material such as glass, and a reflecting mirror 18 is provided on a vertical surface thereof. The reflecting mirror 18 plays a role of reflecting the light of the lamp 12 that is transmitted through the half mirror 17 and enters from the horizontal direction and returns the light to the half mirror 17 side again. The half mirror 17 is a plate-like member made of a light-transmitting material having a transmittance of about 50%, and is disposed on the upper slope of the prism 16. Therefore, the half mirror 17 forms an angle of 45 ° with the horizontal direction. The half mirror 17 reflects the reflected light from the reflecting mirror 18 at 90 ° to the printed wiring board 2 side, and transmits the reflected light from the printed wiring board 2 upward to reach the CCD camera 5 side. Playing a role.

An actuator 19 for retracting the half mirror 17 supporting the half mirror 17 is electrically connected to the control computer 8 via an actuator driving means 20. Therefore, when a control signal is output from the CPU 8a, the actuator 19 operates via the actuator driving means 20. As a result, the half mirror 17 is driven from the use position (ie, the upper slope position of the prism 16) to the retracted position (ie, a position obliquely above the prism 16, a position deviating from the path of the reflected light). I have. As the actuator 19, for example, a fluid pressure cylinder or the like can be used. In this case, as the actuator driving means 20, for example, an electromagnetic valve for supplying / discharging a driving fluid to / from a hydraulic cylinder is used. Of course, instead of a device using fluid pressure, a device using electricity such as a motor may be used as the actuator 19.

Now, a method of inspecting the printed wiring board 2 using the appearance inspection apparatus 1 configured as described above will be described. First, a case where it is desired to inspect the quality of the solder ball 3 will be described. As shown in FIG. 1B, in this case, the first switch 11 is turned on,
The second switch 15 is turned off. Therefore, only the low-angle ring illumination 6 is activated and the high-angle coaxial illumination 7 is deactivated. The driving of the actuator 19 moves the half mirror 17 to the retracted position.

The light emitted from the low-angle ring illumination 6 is reflected by the surface of the printed wiring board 2 and then passes through the prism 16 to reach the lens 5a of the CCD camera 5. as a result,
An image as shown in FIG. 2A is taken.

Here, the solder balls 3 are made of a glossy metal material (ie, solder), while the surrounding base material is made of a non-gloss resin material. As described above, the reflectance differs between a place where the metal material is present and a place where the metallic material is not present. Therefore, in the image of the CCD camera 5, the outline of the solder ball 3 on the printed wiring board 2 appears as an annular bright pattern, and the other portions appear as dark patterns. Therefore, by performing predetermined image processing based on the shape of the light and dark image, the quality of the solder ball 3 is inspected. The graph of FIG. 2B is a chart of the reflection intensity on the A line. According to the chart, it can be seen that the reflection intensity is particularly high in a portion having the contour of the solder ball 3.

Next, a case where it is desired to inspect the quality of the ball pad 4 will be described. As shown in FIG. 1A, in this case, the first switch 11 is turned off and the second switch 15 is turned on. Therefore, only the high-angle coaxial illumination 7 is activated and the low-angle ring illumination 6 is deactivated. The half mirror 17 is returned to the use position.

The light emitted from the lamp 12 once passes through the half mirror 17 and is reflected by the reflecting mirror 18. Light from the reflecting mirror 18 is reflected by the half mirror 17 and reaches the printed wiring board 2 side. Then, this light is reflected by the surface of the printed wiring board 2, then passes through the prism 16 and the half mirror 17 and reaches the lens 5 a of the CCD camera 5. As a result, an image as shown in FIG.

The ball pad 4 is made of a glossy metal material (eg, copper, aluminum, gold, etc.).
The portion of the base material surrounding the base material is made of a dull resin material. As described above, the reflectance differs between a place where the metal material is present and a place where the metallic material is not present. Therefore, the image of the CCD camera 5 includes
The ball pad 4 on the printed wiring board 2 appears as a circular bright pattern, and other portions appear as dark patterns. Accordingly, the quality of the ball pad 4 is inspected by performing predetermined image processing based on the shape of the light and dark image. The graph of FIG. 3B is a chart of the reflection intensity on the B line. According to the chart, it can be seen that the reflection intensity is particularly strong at a certain portion of the ball pad 4.

Here, as a comparative example with respect to the present embodiment,
As shown in FIG. 4, three types of appearance inspection devices having different illumination modes were prepared. The visual inspection device of Comparative Example 1
Only the low-angle ring illumination 6 is provided (see FIG. 4A). The visual inspection device of Comparative Example 2 has a low-angle ring illumination 6
And high-angle coaxial illumination 7,
4 is not provided with a switching means for selectively switching the number 7 (see FIG. 4).
(B)). Therefore, in Comparative Example 2, light obtained by blending the two illuminations 6 and 7 is applied. Comparative Example 2 does not include the half mirror retracting actuator 19 and the actuator driving unit 20. The visual inspection device of Comparative Example 3 includes a high-angle ring illumination 21 and a light diffusion plate 22 in addition to the low-angle ring illumination 6 (FIG. 4).
(C)).

Using the four kinds of appearance inspection apparatuses 1, an appearance inspection was performed as follows, and the obtained results were compared (see the table in FIG. 5). here,
In particular, 22 non-defective samples having no defects and 7 samples having misalignment in the solder balls 3
And seven samples having scratches on the solder balls 3 were prepared. Then, the defect detection rate and the over-inspection rate were calculated based on the determination result (“OK” or “NG”) by the image processing.

In the embodiment, the defect detection rate and the over-inspection rate of the non-defective product, the ball displacement and the ball scratch are 0% and 100%, respectively.
% And 100%, indicating that the detection accuracy was extremely excellent. In addition, when the quality inspection for the size and displacement of the ball pad 4 was performed in the same manner, no particular problem was found, and it was found that the detection accuracy was extremely excellent.

Also in Comparative Example 1, the defect detection rate and the over-inspection rate of the non-defective product, the ball displacement and the ball flaw were 0%, respectively.
100% and 100%, indicating that the detection accuracy was extremely excellent. However, when a pass / fail inspection of the size and displacement of the ball pad 4 was performed in the same manner, in this case, the erroneous detection rate was increased, and the detection accuracy tended to decrease. Therefore, it was concluded that the low-angle ring illumination 6 was not suitable for inspecting the ball pad 4 having a flat shape.

In Comparative Example 2, the defect detection rate and the over-inspection rate of the non-defective product, the ball displacement and the ball flaw were 9% and 100%, respectively.
% And 71%, which are clearly inferior in detection accuracy as compared with the embodiment.

In Comparative Example 3, the defect detection rate and the over-inspection rate of the non-defective product, the ball displacement and the ball flaw were 36% and 10%, respectively.
It was 0% and 100%, and the detection accuracy was clearly inferior to the embodiment.

Therefore, according to the present embodiment, the following effects can be obtained. (1) The visual inspection apparatus 1 of the present embodiment uses the low-angle ring illumination 6 as the first illumination, the high-angle coaxial illumination 7 with a higher illumination angle, and the two illuminations 6 and 7 as the shape of the inspected part. Switching means for selectively switching according to the characteristic. Therefore, these two types of illuminations 6 and 7 can be selectively switched appropriately by the switching means to perform an appearance inspection. Further, when inspecting a ball pad 4 having a flat shape, it is better to irradiate light from the high-angle coaxial illumination 7.
The amount of light reflected on the CCD camera 5 side increases. Therefore, by operating only the low angle ring illumination 6,
The quality of the solder ball 3 can be accurately inspected. On the other hand, by operating only the high-angle coaxial illumination 7, the quality of the ball pad 4 can be accurately inspected.

Further, according to the present embodiment, it is possible to inspect two kinds of inspected parts having different geometric properties with one appearance inspection apparatus 1. For this reason, the versatility appearance inspection apparatus 1 can be obtained. That is, the appearance inspection device 1
By making use of the above, investment in package production equipment can be reduced, and as a result, the cost of the package can be reduced.

(2) The high-angle coaxial illumination 7 in the visual inspection apparatus 1 reflects the incident light from the lamp 12 in the direction of the printed wiring board 2 and reflects the reflected light from the printed wiring board 2 to the CCD camera 5 side. A half mirror 17 for transmitting light through the mirror is provided. Further, the half mirror 17 can be moved between two positions by an actuator 19 for retracting the half mirror and an actuator driving means 20. Therefore, the half mirror 17 can be retracted from the path of the reflected light as needed. Therefore, the loss of reflected light due to the interposition of the half mirror 17 is eliminated,
A clear image that is bright and excellent in resolution can be obtained. Therefore, even if the solder balls 3 and the ball pads 4 are many and fine, the quality of the solder balls 3 and the ball pads 4 can be inspected easily and with extremely high accuracy.

(3) The visual inspection apparatus 1 controls the first switch 11 for turning on and off the low-angle ring illumination 6, the second switch 15 for turning on and off the high-angle coaxial illumination 7, and the switches 11, 15. Switching means comprising a CPU 8a is provided. Therefore, it is possible to easily and surely switch between the two illuminations 6 and 7 according to the shape properties of the inspected portion.

The embodiment of the present invention may be modified as follows. The part to be inspected having a three-dimensional shape is not necessarily limited to the solder ball 3 and may be a ball made of a conductive metal other than solder, for example, a gold ball. In addition, not only a ball-shaped (perfect spherical) terminal portion but also, for example, an imperfect spherical (hemispherical) terminal portion may be used as the inspection target portion. Furthermore, a three-dimensional structure other than the terminal portion, for example, a mushroom-shaped bump or the like, a terminal pin, or the like can be used as the inspection target site.

The switching means includes a first switch 11 and a second switch 11.
The invention is not limited to the one including the switch 15 and the CPU 8a. For example, a single switch integrating the two switches 11 and 15 may be used. A switch 1 electrically switched by a CPU 8a in the control computer 8
1 and 15 using a switch for manual switching
May be configured.

As a part to be inspected having a planar shape,
The wiring pattern is not necessarily limited to the ball pad 4, and may be, for example, a wiring pattern formed on the surface of the printed wiring board 2. The inspected part is not necessarily limited to a glossy part, and may be a part with little or no alternation.

The test object is not limited to the printed wiring board 2 as shown in the embodiment, but may be another electronic component having a terminal portion and the like. Moreover,
Of course, it is also possible to use an object other than the electronic component as the inspection object.

Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-described embodiment will be enumerated below. (1) In any one of claims 1 to 3, both the inspected parts are made of a glossy metal material.

(2) The device according to any one of claims 1 to 3, wherein both of the inspected portions are terminal portions made of a glossy metal material. (3) In any one of claims 1 to 3, the switching means includes a first switch for turning on and off the first lighting, a second switch for turning on and off the second lighting, And control means for controlling the switch.

(4) In Claim 3, an actuator for retracting the half mirror for retracting the half mirror from the path of the reflected light is provided.

[0046]

As described in detail above, according to the first to third aspects of the present invention, it is possible to provide an appearance inspection apparatus which has high versatility and excellent inspection accuracy.

According to the third aspect of the invention, the inspection accuracy can be further improved. Claims 4 and 5
According to the invention described in (1), the appearance inspection of the printed wiring board can be accurately performed.

[Brief description of the drawings]

FIGS. 1A and 1B are schematic perspective views showing a main part of a visual inspection apparatus according to an embodiment of the present invention.

FIG. 2A is a diagram illustrating an example of imaging of a ball by the appearance inspection device of the embodiment, and FIG. 2B is a graph illustrating the reflection intensity at that time.

FIG. 3A is a diagram of an example of imaging of a ball pad by the visual inspection device of the embodiment, and FIG. 3B is a graph showing the reflection intensity at that time.

FIGS. 4A, 4B, and 4C are schematic perspective views showing main parts of a visual inspection device of a comparative example.

FIG. 5 is a graph showing comparison results of the embodiment and each comparative example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Appearance inspection apparatus, 2 ... Printed wiring board as a test object, 3 ... (Solder) ball as a 1st test part,
4 ... Ball pad as a second part to be inspected, 5 ... CCD camera as imaging means, 6 ... Low angle ring illumination as first illumination, 7 ... High angle coaxial illumination as second illumination,
8a CPU constituting the switching means, 11 first switch constituting the switching means, 15 second switch constituting the switching means, 17 half mirror.

Claims (5)

[Claims] An imaging unit configured to image a site to be inspected on a surface of the object to be inspected; and an illumination unit configured to irradiate light to the site to be inspected. In a visual inspection device for inspecting the quality of a part, a first illumination, a second illumination having an irradiation angle higher than the first illumination, and the two illuminations are selectively switched according to a shape property of the inspected part. An appearance inspection apparatus comprising a switching unit. 2. The method according to claim 1, wherein the first illumination is a low-angle ring illumination,
The visual inspection apparatus according to claim 1, wherein the second illumination is a high-angle coaxial illumination located at a position farther from the object to be inspected than the first illumination. 3. The second illumination includes a half mirror that reflects incident light from a light source in the direction of the object to be inspected and transmits reflected light from the object to be inspected toward the imaging unit. The appearance inspection apparatus according to claim 2, wherein the half mirror is provided so as to be able to retreat from a path of the reflected light. 4. A second inspection part on a printed wiring board is inspected by using only the second illumination while using the appearance inspection apparatus according to any one of claims 1 to 3. A visual inspection of a printed wiring board, characterized in that only the first illumination is operated to inspect a first inspected part on the printed wiring board, the first inspected part being three-dimensional in shape than the first inspected part. Method. 5. The device according to claim 4, wherein the first inspected portion is a ball for external connection, and the second inspected portion is a ball pad to which the ball is bonded. Visual inspection method for printed wiring boards.