JPH10221271A - Photographing system for specular object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To photograph a distorted specular object in good performance. SOLUTION: Light emitted from a halogen lamp is cast from the tips of light guides 2a and 2b onto a diffusive surface of a hemisphere 4, whose inner wall constitutes a hemispherical diffusive surface of reflex type. Thus a diffused indirect light is produced by the hemisphere 4, and with it a work 5 is irradiated. The reflected light by the work is passed through an observation window 14 furnished in the hemisphere 4 and incident on a camera 1. Because the diffused indirect light by the hemisphere 4 are incident on the work 5 from various sides, the manifoldly distorted surface of the work 5 can be irradiated uniformly, and it is possible to photograph the work 5 properly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection apparatus for inspecting a specular object such as a back surface of a TCP, and more particularly, to an imaging system for imaging a specular object.

[0002]

2. Description of the Related Art Conventionally, TCP (Tape Carrier Packa) has been used as a mounting technique suitable for a demand for increasing the number of pins of an IC or LSI.
ge) is known. TCP is TAB (Tape Automat
This is a film carrier type package that uses the technology of ed bonding). A copper foil pattern formed by etching on a polyimide film carrier (TAB tape) is bonded to the electrodes of the IC chip to form external leads. . FIG. 12 is a sectional view of the TCP. TCP is
Film carrier 21, copper foil pattern 22 formed on film carrier 21, IC chip 23, chip 23
Bumps 24 made of Au or the like formed on the pads of FIG.
2 to protect the unit from external forces, moisture, contaminants, etc.
5 is comprised.

In TCP, defects such as short-circuit or chipping of the copper foil pattern 22 may occur during manufacturing. Conventionally, the presence or absence of these defects has been visually inspected manually. However, due to the increase in production volume and fine patterning due to high density, visual inspection has required a lot of human labor, and in recent years the demand for automation has been rapidly increasing, and the copper foil pattern of a film carrier has been imaged with a TV camera. Inspection technology has been proposed (see, for example,
341960).

[0004] Apart from the inspection relating to the front surface of the TCP, as an inspection relating to the back surface of the TCP (the lower surface in FIG.
Alternatively, it is necessary to inspect adhesion of the resin 25 to the IC chip 23 (in FIG. 12, adhesion to the film carrier 21 or the lower surface of the IC chip 23), unmounting of the IC chip 23, and the like. Therefore, it is desired to automate the inspection of the TCP back surface as well as the front surface, but this has the following problems.

FIG. 13 shows the back surface of the TCP. The white part at the center of the TCP is the IC chip 23, the black part around it is the resin 25, and the other gray parts are the film carrier 21. The back surface of the film carrier 21 has a smooth texture and very strong gloss. Furthermore, the film carrier 21 has distortion and undulation due to the effects of mounting the IC chip 23, applying the resin 25, and curing the resin 25. On the other hand, the resin 25 is semi-glossy when dried through a baking furnace. The back surface of the IC chip 23 is not coated with a resin, and has a metallic luster.

As described above, the back surface of TCP must be considered as a kind of mirror surface due to its high gloss. Since mirror-like objects reflect the emitted visible light with high efficiency,
The observer is observing an image (visible light specularly reflected from the object) reflected on a mirror-like object. Therefore, the observation of a mirror-like object is based on the premise that an object that satisfies the observation conditions is projected on the object surface. When direct light is used for illumination in observing the TCP back surface, the specularly reflected direct light itself is observed depending on the observation position. When observation is performed while avoiding direct reflection of direct light, the amount of light applied to the TCP surface is extremely small, and satisfactory observation results cannot be obtained. For these reasons, an illumination method of directly irradiating light to the TCP back surface that causes specular reflection is not advisable.

As an effective illumination method for the TCP back side,
A method using diffuse indirect light is conceivable. FIG. 14 shows a block diagram of an imaging system of a conventional TCP visual inspection device using a half mirror and a diffusion plate. In this inspection device, the light source 31
Is diffused by the diffusion plate 32 and the TCP 34 is irradiated with the diffused light by the half mirror 33. Then, the reflected light from the TCP 34 passes through the half mirror 33 and enters the camera 31. According to the illumination method as shown in FIG. 14, it is possible to create a pseudo uniform surface light source and irradiate it as complete epi-illumination. Further, since diffused light is generated by the diffuser plate 32, the mirror-like object T
This is very effective as illumination for the back surface of the CP.
This is because the diffused light obtained by the half mirror 33 is light having a single directivity, so that a flat mirror surface can be evenly irradiated with a light beam.

However, the rear surface of the TCP 34 is far from a flat mirror surface due to distortion and undulation, and has tilt components in various directions. Since the camera 35 has no direct relationship with the reflection component of the irradiation light on the inclined surface of the TCP 34, it is impossible to obtain a uniform illumination effect on the inclined portion by the half mirror 33. In this case, the camera 35 observes an object other than the illumination reflected on the inclined surface of the TCP 34. If the reflected object is black, the captured image also has a low luminance level in the reflected portion, which may cause erroneous detection. In order to avoid such a state, the light source for the TCP must be able to irradiate the inclined surface of the TCP evenly,
The conventional imaging method using a half mirror has no ability to respond to the inclination of TCP.

[0009]

As described above, the imaging method of the conventional inspection apparatus has a problem that a distorted mirror-like object such as TCP cannot be appropriately imaged and inspected. SUMMARY An advantage of some aspects of the invention is to provide an imaging method capable of correctly imaging a distorted mirror-like object.

[0010]

According to the present invention, there is provided a hemispherical diffuser arranged at a position facing a mirror-like object so that reflected light is incident on the mirror-like object. A diffusing hemisphere having a surface, illumination means for illuminating the diffusing surface of the diffusing hemisphere, and a mirror surface arranged such that reflected light from the specular object enters through a window provided in the diffusing hemisphere. And a camera for imaging the object. As described above, when the diffuse indirect light is generated using the diffuse hemisphere, and the specular object is illuminated with the diffuse indirect light, the diffuse indirect light obtained by the diffuse hemisphere enters the specular object from various directions. Even if there is distortion in the specular object, variously distorted surfaces of the specular object can be evenly illuminated.

Further, as described in claim 2, the camera is disposed at a predetermined angle with respect to the mirror target, and the window of the diffusion hemisphere is diffused according to the inclination of the camera. It is provided at a position off the vertex of the hemisphere. As described above, the camera is disposed at a predetermined angle with respect to the specular object, and the window of the diffusion hemisphere is provided at a position deviated from the vertex of the diffusion hemisphere in accordance with the inclination of the camera. Can be prevented from being reflected on a specular object.

[0012]

FIG. 1 is a block diagram of an image pickup system of a TCP visual inspection apparatus showing a first embodiment of the present invention, wherein 1 is a camera, 2a and 2b are each composed of a plurality of optical fibers. Light guides 3a and 3b for transmitting light emitted from a halogen lamp (not shown)
Attachments for fixing the tips of a and 2b, 4 is a diffusion hemisphere whose inner wall is a hemispherical diffusion surface, and 5 is a work whose observation surface is a mirror surface (in the present embodiment, the back surface is a mirror surface). TCP).

Next, the operation of the imaging system of such a TCP visual inspection device will be described. Light emitted from a halogen lamp (not shown) is applied to the diffusion surface of the diffusion hemisphere 4 from the tips of the light guides 2a and 2b. The light guides 2a, 2b
The reason for oblique irradiation from two directions is to prevent the diffusion surface of the diffusion hemisphere 4 from being shaded. Diffuse hemisphere 4
Has a hemispherical reflective diffuser surface on the inner wall, and the diffuser surface is subjected to a white non-glare (matte) treatment to prevent generation of a regular reflection component of illumination.

Thus, the diffusion hemisphere 4 is illuminated from at least two directions, and the spread angle of the light beam radiated from the light guides 2a and 2b is large, so that the diffusion surface of the diffusion hemisphere 4 is uniformly illuminated. By uniformly irradiating the light on the diffusion surface of the diffusion hemisphere 4, the light reflected from the diffusion surface becomes diffuse indirect light.

The indirect light generated by the diffusing hemisphere 4 is
In principle, from a plane parallel to the diffusion hemisphere 4 (parallel here means perpendicular to the center axis of the hemisphere 4 passing through the vertex and center of the diffusion hemisphere 4), It is possible to uniformly irradiate light on all surfaces inclined immediately before (parallel to the central axis). Therefore, it is possible to effectively irradiate light even to a distorted portion that cannot be illuminated by illumination using a conventional half mirror.

On the other hand, in order to image the work 5 with the camera 1, it is necessary to obtain reflected light from the work 5, but since the diffuse hemisphere 4 itself is colored and opaque, the work 5 is observed at the vertex thereof. It is indispensable to provide a window 14 (hereinafter referred to as an observation window). Thereby, the reflected light from the work 5 enters the camera 1 through the observation window 14.

In FIG. 1, the hemisphere 4 is arranged so that the center axis of the diffusion hemisphere 4 is perpendicular to the work 5, and the take-up axis of the camera 1 is perpendicular to the work 5. The camera 1 is arranged, and the observation window 14 is provided at the vertex of the hemisphere 4. However, in the actual inspection, the observation window 14 is reflected on the work 5 because the observation surface of the work 5 is mirror-like. An obstacle to doing so.

Therefore, in order to exclude the observation window 14 from the observation field of view, the window 14 is shifted from the vertex of the diffusion hemisphere 4 to a position where it is not reflected, and the taking axis of the camera 1 is positioned with respect to the workpiece 5. The image of the work 5 is captured by inclining at an appropriate angle from the vertical position. With this method, the phenomenon that the observation window 14 is reflected on the work 5 can be prevented.

Next, a detailed calculation of the above-described imaging system will be described. First, the work 5 and the camera 1 shown in FIG.
A distance d (to be precise, an image pickup element of the camera 1) (hereinafter, referred to as a work distance) is determined by a focal length and a resolution of a lens of the camera 1. Further, the distance Wd between the edge of the diffusion hemisphere 4 and the work 5 and the radius r of the diffusion hemisphere 4
Is determined by factors such as the resolution, the size of the observation area (inspection range) on the work 5, the distortion of the work 5, and the like.

Although the resolution and the observation area size are determined according to the specifications, the distortion of the work 5 is an uncertain factor.
Therefore, the distance Wd and the radius r are determined by limiting the distortion or the like of the work 5 to a realistic range and conducting an experiment to determine conditions for realizing an ideal illumination state as experimental values.

Subsequently, as shown in FIG. 2, the length of the imaging device 11 (for example, a CCD device) of the camera 1 in the x direction is represented by Wx
The length of the observation window 14 in the x direction is Wx, the length of the observation window 14 in the y direction is Wy, and the length of the observation area 15 on the workpiece 5 in the x direction is Wx.
Assuming that the length in the work and y directions is Wywork, the positional relationship among the image sensor 11, the observation window 14, and the observation area 15 is set as shown in FIG.

The x-direction and z-direction are as shown in FIG. 1, but the y-direction means a direction perpendicular to the plane of FIG. 1 and is a transport direction in TCP.
Then, from the positional relationship in FIG. 3, the sizes Wx and Wy of the observation window 14 provided in the diffusion hemisphere 4 can be obtained by the following equations.

Wx = Wxwork − {(Wxwork−Wxccd) × (Wd + r) / d} (1) Wy = Wywork − {(Wywork−Wyccd) × (Wd + r) / d} (2)

If the camera 1 is tilted as described above, a slight distortion of the captured image cannot be avoided.
It is necessary to minimize the tilt of the camera 1. In addition, the direction in which the camera 1 is tilted is set to the short y direction in order to minimize distortion. Next, the calculation of the position of the observation window 14 and the tilt angle θ3 of the camera 1 will be described.
FIG. 4 is a diagram for explaining this calculation method.

In FIG. 4, the angle θ1 between a straight line connecting the edge E of the observation area 15 projected onto the diffusion hemisphere 4 and the center O of the diffusion hemisphere 4 and the perpendicular of the work 5 can be obtained by the following equation. . θ1 = arcsin {Wywork / (2 × r)} (3) When an observation window 14 is provided at the vertex P of the diffusion hemisphere 4 and an image is taken in from a position perpendicular to the work 5, The observation window 14 is reflected at the position of K1.

On the other hand, the observation area 1 on the work 5
In the case where the observation window 14 is set at a position not reflected in 5, the circumferential distance ds1 from the vertex P of the diffusion hemisphere 4 to the center Q of the observation window 14 can be obtained by the following equation. ds1 = (θ1 / 180) × π × r + (1/2) × Wy (4)

Therefore, the observation window 14 has a size of Wx in the x direction and Wy in the y direction, centered on the position Q shifted from the vertex P of the diffusion hemisphere 4 by the circumferential distance ds1. Further, an angle θ2 between a straight line connecting the center O of the diffusion hemisphere 4 and the center Q of the observation window 14 and the perpendicular line of the workpiece 5 is obtained by the following equation using the distance ds1. θ2 = {180 / (π × r)} × ds1 (5)

Therefore, the angle formed by the straight line connecting the center of the observation area 15 and the center Q of the observation window 14 and the perpendicular of the work 5, that is, the inclination angle θ3 of the camera 1 can be calculated by the following equation. θ3 = arctan {r × sin θ2 / (r × cos θ2 + Wd)} (6)

By the above calculation, the position on the work 5 where the observation window 14 is reflected can be moved to K2.
The image of the observation area 15 in which the observation window 14 is not reflected can be captured by the camera 1. Next, when the camera 1 is simply tilted by only the angle θ3 and moved to a position where the observation area 15 is taken in, the distance between the work 5 and the image sensor 11 becomes longer than the work distance d. Since the work distance d is a value determined by the resolution, it must be constant regardless of the tilt of the camera 1.

Therefore, in order to maintain the work distance d, the shift amount dy in the y direction of the camera 1 and the shift amount dz in the z direction are calculated by the following equations. dy = d × sin θ3 (7) dz = d × (1-cos θ3) (8)

Thus, as shown in FIG.
1 (camera 1) is tilted by θ3, and dy and z are
By shifting by dz in the direction, it is possible to capture an image without reflection of the observation window 14 without changing the resolution.

When the camera 1 is tilted to capture an image, the captured image is distorted as described above. FIG. 5 is a diagram for explaining a method of correcting the distortion of the captured image. FIG.
As shown in the figure, when the camera 1 is tilted by θ3 with the work distance d unchanged, the observation area 1 on the work 5
Resolution PIXP of one pixel at edges P1 and P2 of 5
1, PIXP2 is calculated as follows.

PIXP1 = PIXorg × (d−δd) / d (9) PIXP2 = PIXorg × (d + δd) / d (10) In equations (9) and (10), PIXorg is a standard resolution. , Δd = (Wy × sin θ3) / 2. In this way, based on the equations (9) and (10), the resolution of the captured image is corrected and the actual inspection is performed.

In an actual inspection, a grayscale image of the work 5 picked up by the camera 1 is digitized by an A / D conversion circuit (not shown), and the digital image data is binarized by a binarization circuit (not shown). By comparing the structured pattern with a reference master pattern, for example,
The work 5 can be inspected.

For example, on the rear surface of the TCP, there are a portion where strong reflection such as an IC chip and a film carrier occurs and a portion where weak reflection such as a resin occurs. As will be described later, according to the imaging method of the present invention, such shading can be appropriately captured, so that the value between the density of the IC chip or film carrier and the density of the resin is binarized. By setting the threshold value and binarizing the captured image data, IC
For example, a binary pattern in which the chip or the film carrier becomes “1” and the resin becomes “0” is obtained.

At this time, if the resin adheres to the IC chip or the film carrier, the portion of the chip or the film carrier which should be "1" becomes "0". Therefore, if the binarized pattern is compared with the master pattern, the adhesion of the resin can be easily detected. vice versa,
If the resin is insufficient, the portion that should originally be “0” becomes “1”. Thereby, shortage of resin can be easily detected.

Similarly, when the IC chip is not mounted, the portion of the chip which should be "1" is "0". This makes it possible to easily detect that the IC chip is not mounted.

As described above, whether or not the work 5 is normal can be inspected. In the TCP, a hole is formed in the film carrier, and only the reflection illumination (illumination illuminated from the observation side) by the diffusion hemisphere 4 is taken in a state where the hole portion is blackened out. As a result, the brightness level becomes the same as that of the resin, which is a cause of erroneous detection. Such a problem can be prevented beforehand by setting the hole portion to the brightness level of the film.

Therefore, for the work 5 having a hole such as the back surface of the TCP, the observation surface is opposite (that is, FIG.
Illuminate the surface light source from below) and set the brightness level at the hole to the level of the film. By configuring such illumination, it is possible to obtain a stable image for performing an inspection.

FIGS. 6 and 7 show photographs of the back of the TCP captured by the conventional imaging system of FIG. 14, and FIGS. 8 to 10 show photographs of the back of the TCP captured by the imaging system of the present embodiment.
6 to 10 show images obtained by imaging the rear surface of the TCP as a photograph (output by a video printer).

FIG. 11 is a diagram for explaining FIGS. 6 to 10. As shown in FIG. 11, a box-shaped white portion crossing the gray film carrier 21 in FIGS. 6 to 10 is an IC chip 23, a black portion around the IC chip 23 is a resin 25, and the film carrier 21 is vertically extended. The box-shaped white portion that crosses is the metal reflection surface G of the tape guide.

The black portion at the right end is a menu display section M of the video printer, a crossing point between the x-axis line Lx and the y-axis line Ly indicates a position where the luminance distribution is measured, and a curve Rx near the crossing liner. , Ry respectively represent the luminance of the X coordinate and the y coordinate indicated by the cross cursor C.
Note that the luminance indicated by the curve Rx is higher toward the upper side, and the luminance indicated by the curve Ry is higher toward the right side.

As can be seen from FIGS. 6 and 7, when the back surface of the TCP is taken in by the conventional imaging system, the film carrier 21
The difference in brightness (contrast) between the resin and the resin 25 is not sufficiently obtained. Further, shading (shade) occurs near the edge of the film carrier 21. The reason why contrast cannot be obtained is that, due to the structure of the half mirror, the color of the indirect light diffused by the milky white acrylic plate slightly changes from white, so that when reflected on the TCP, the luminance level of the film carrier 21 is sufficiently reduced. Is not improved.

Further, the TCP is distorted by the influence of the heat received in the baking furnace, and the film surface has various angles. Therefore, the unidirectional light beam emitted from the half mirror cannot correspond to the angle of the film surface. as a result,
It is concluded that shading has occurred at the edge of the film carrier 21. Therefore, resin 2
It is very difficult to detect the shortage or protrusion of 5 and the adhesion of the resin on the film carrier 21.

On the other hand, as can be seen from FIGS.
When the back surface of P is captured by the imaging system of the present embodiment, it can be seen that a sufficient difference in luminance between the film carrier 21 and the resin 25 is obtained. Shading due to distortion near both edges of the film carrier 21 does not occur. This is because by using the diffusion hemisphere 4, TCP
This is because it has become possible to irradiate diffused light to the film surface tilted due to the distortion.

Therefore, as shown in FIG. 10, the resin 25 adheres to the film carrier 21 (in FIG. 10,
The elliptical black point on the lower side of the IC chip 23) When the TCP is captured by the imaging system of the present embodiment, since there is a contrast between the attached resin and the film carrier,
This defect can be easily detected. In the present embodiment, the back surface of the TCP is imaged, but it goes without saying that the present invention may be applied to other objects.

[0047]

According to the present invention, as described in claim 1, diffuse indirect light is generated by using a diffuse hemisphere, and the mirror indirect light is illuminated with the diffuse indirect light, thereby distorting the specular object. Is present, the variously distorted surfaces of the mirror-like object can be uniformly illuminated, and the distorted mirror-like object can be correctly imaged. As a result, if the captured image is used in an inspection apparatus that inspects a mirror-finished object, the mirror-finished object can be correctly inspected.

Further, as described in claim 2, the camera is disposed at a predetermined angle with respect to the mirrored object, and the window of the diffusion hemisphere deviates from the vertex of the diffusion hemisphere according to the inclination of the camera. By providing it at the position, it is possible to prevent the window of the diffuse hemisphere from being reflected on a mirror target in the observation area of the camera.

[Brief description of the drawings]

FIG. 1 is a block diagram of an imaging system of a TCP visual inspection device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the size of an image sensor, an observation window, and an observation area of a camera.

FIG. 3 is a diagram illustrating a positional relationship among an image sensor, an observation window, and an observation area.

FIG. 4 is a diagram for explaining a method of calculating a position of an observation window and a tilt angle of a camera.

FIG. 5 is a diagram for explaining a method of correcting distortion of a captured image.

FIG. 6 is a photograph of a TCP back surface captured by a conventional imaging system.

FIG. 7 is a photograph of a TCP back surface captured by a conventional imaging system.

FIG. 8 is a photograph of a TCP back surface captured by the imaging system of FIG. 1;

FIG. 9 is a photograph of a TCP back surface captured by the imaging system of FIG. 1;

FIG. 10 is a photograph of a TCP back surface captured by the imaging system of FIG. 1;

FIG. 11 is a diagram for explaining FIGS. 6 to 10;

FIG. 12 is a sectional view of a TCP.

FIG. 13 is a bottom view of the TCP.

FIG. 14 is a block diagram of an imaging system of a conventional TCP visual inspection device.

[Explanation of symbols]

1 ... camera, 2a, 2b ... light guide, 4 ... diffusion hemisphere, 5
... workpiece, 11 ... image sensor, 14 ... observation window, 1
5 ... Observation area.

Claims (2)

[Claims] 1. A diffusing hemisphere having a hemispherical diffusing surface, which is disposed at a position facing the specular object so that reflected light is incident on the specular object, and for illuminating the diffusing surface of the diffusing hemisphere. And a camera arranged to cause reflected light from the specular object to enter through a window provided in the diffuse hemisphere, and a camera for imaging the specular object. The imaging method of the object. 2. The method according to claim 1, wherein the camera is disposed at a predetermined angle with respect to the mirror object, and the window of the diffusion hemisphere is a camera. An imaging method for a specular object, which is provided at a position deviated from the vertex of the diffusion hemisphere in accordance with the inclination of the object.