JPH0617776B2 - Bonding wire inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a bonding wire inspection method.

(Prior Art) FIG. 5 is a configuration diagram of a bonding wire inspection apparatus. In the figure, reference numeral 1 is an XY table.
The IC chip 2 that has been bonded on the table 1
And the frame 3 is mounted. That is, the IC chip 2 and the frame 3 are electrically connected by the plurality of bonding wires 4. The XY table 1 is composed of an X table 1a and a Y table 1b, and is driven by an X direction motor 5 and a Y direction motor 6, respectively. On the other hand, a microscope 7 is arranged above the XY table 1, and a CCD is attached to the eyepiece of the microscope 7.
(Solid-state image sensor) A camera 8 is attached. Then, the image signal output from the CCD camera 8 is sent to the image processing unit 9 for image processing. An illumination device 10 is attached to the microscope 7 to irradiate the bonding wire 4 with light. Further, the image processing unit 9 performs an image processing operation in response to a command from the host computer 11, and the motors 5 and 6 are driven through the control unit 12 and the driving unit 13 by a command issued from the host computer 11. ing.

However, the image processing unit 9 receives the image signal from the CCD camera 8 to obtain image data, and extracts only the bonding wire 4 from this image data. Then, it is detected whether or not the bonding wire 4 is in contact with an adjacent bonding wire, the bending state of the bonding wire 4, the contact state of the bonding wire 4 with the pad of the IC chip 2 and the lead of the frame 3, and the like. It

(Problems to be Solved by the Invention) However, in the above device, the image data obtained because the CCD camera 8 is arranged above the bonding wire 4 is a planar image of the bonding wire 4 seen from above. Has become. For this reason, it is impossible to inspect the data in the height direction of the bonding wire 4, that is, the height, the sagging, etc. of the bonding wire 4.
Therefore, the inspection of the bonding wire 4 is insufficient.

Therefore, an object of the present invention is to provide a bonding wire inspection method capable of obtaining a three-dimensional shape of a bonding wire and also inspecting in the height direction.

[Configuration of Invention] (Means and Actions for Solving the Problem) The present invention provides a bonding wire inspection method for inspecting a three-dimensional shape of a bonding wire in which terminals are electrically connected to each other. A second image obtained by the second imaging device capturing a line of sight when the first and second imaging devices capture images from different directions and then the first imaging device captures a predetermined bonding wire. A line-of-sight image projected on the data is drawn, and then a line passing between the line-of-sight image and each terminal connected by a bonding wire is obtained. Next, from the intersection of this line and the line-of-sight image, a predetermined line on the second image data is obtained. Of the bonding wire image of each of the first and second image data. This is a bonding wire inspection method for achieving the above object by recognizing the three-dimensional shape of the bonding wire.

(Example) Hereinafter, one example of the present invention will be described with reference to the drawings. The same parts as those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a configuration diagram of a bonding wire inspection apparatus to which the bonding wire inspection method is applied. Two microscopes 20 and 21 are arranged above the XY table 1 so that the imaging directions of the bonding wires 4 are different from each other, and further, the first CCD camera 22 and the first CCD camera 22 are attached to the eyepieces of these microscopes 20 and 21, respectively. Two CCD cameras 23 are attached. And these CCD cameras 22, 23
Each image signal output from the image processing unit 25 is sent to the image processing unit 25 through the camera switch 24. In addition, each microscope 20,
Illumination devices 26 and 27 are attached to 21 to irradiate the bonding wire 4 with light.

The image processing unit 25 has a function of receiving a command from the host computer 28 and obtaining the three-dimensional shape of the bonding wire 4 from the image data obtained by the CCDs 22 and 23. The second CCD camera 23 obtains a line-of-sight image (hereinafter referred to as an epipolar line) when a predetermined one of the bonding wires 4 is captured by the second CCD camera 23. The line-of-sight image projected on the image data is drawn, and then a line passing between the lead 3a and the pad 2a connected to this epipolar line by a predetermined one bonding wire 4 is obtained. An image of one predetermined bonding wire 4 on the second image data is extracted from the intersection, and then the first and second bonding wires 4 are extracted. It has become one that recognizes the three-dimensional shape of the predetermined bonding wires 4 from the image of a predetermined bonding wires 4 in the second image data.

Here, a method of obtaining three-dimensional coordinates by a stereo camera using the CCD cameras 22 and 23 will be described with reference to FIG. The method of obtaining the three-dimensional coordinates is described in Author Y.
“A Stereo fo by Yakimovaky
r Extracting Three-Dimensions
Ional Measurements from a
stereo Pair of TV camera
s ”Computer Graphica and I
maga Processing July issue, 195-2
Page 10, 1978.

In Figure 4 Since, Here, the center of the first image plane is (0, 0), I _L : I coordinate of the first image plane I _L : First CCD camera lens focal point H _L ′: First CCD camera lens Horizontal unit vector V _L ′: Vertical unit vector of the first CCD camera lens A _L : Unit vector in the lens optical axis direction, That is, If f _L H _L ′ = H _L Becomes In the same way f _L V _L ′ = V Becomes Therefore, H: horizontal vector, V: vertical vector, A: unit vector in the lens optical axis direction, Set the model to be. Then, when these equations (1) and (2) are modified, (P−C, H−I · A) = 0 (3) (P−C, V−J · A) = 0 (( 4) and from these equations (3) and (4) Is required. Since R is a unit vector, P = C + λR λ> 0 (5) Next, when the formula (3) is expanded, (P, IA)-(C, IA)-(P, H) + (C, H) = 0, and when the suffix for the observation point on the m side is introduced, (P _m , I _m · A) − (C, I _m · A) − (P _m , H) + (C, H) = 0 ... (6) Similarly, when the formula (4) is expanded and the suffix for m observation points is introduced, (P _m , J _m · A) − (C, J _m -A)-( _Pm , V) + (C, V) = 0 (7). Therefore, , And camera parameters (A, H, V, Ch, Ca,
Cv Ch = (C, H), Ca = (C, A), Cv = (C,
V).

By the way, the left and right camera parameters (A, H, V, Ch, Ca, Cv) of the stereo camera and the first and second C
3 from the sample coordinates (I, J) of the CD cameras 22 and 23
When obtaining the dimensional coordinates P (Px, Py, Pz), the first (1)
By modifying the equation and the equation (2), (IA-H, P) = ICa-Ch, similarly, (JA-V, A) = JCa-Cv. Since the first and second CCD cameras 22 and 23 are provided, if suffixes L and R representing left and right parameters are introduced to these cameras 22 and 23, (I _L A _L −H _L , P) = I _L C _{aL -C hL (I R A R} -H R, P) = I R Ca R -Ch R (J L A L -V L, P) = J L Ca L -Cv L (J R A R -V R , P) = J _R Ca _R −Cv _R. Therefore, if this is expressed in a matrix, Therefore, if this equation (8) is solved, the three-dimensional coordinate P (Px, P
y, Pz) can be obtained.

Next, how to obtain the epipolar line will be described.
Here, the first image data obtained by the image pickup of the first CCD camera 22 is set as shown in FIG.
When the second image data obtained by the image pickup by the CD camera 23 is set as shown in FIG. 3, the first CCD camera 2
When 2 takes an image of the bonding wire 4-1, when the line of sight of the first CCD camera 22, that is, the optical axis is drawn on the second image data, this line of sight becomes an epipolar line l.

Here, in the YaKimovsky method, each CCD camera 2
2,23 camera parameters (A, H, V, Ch, C
a, Cv) and the coordinates (I,
It is known from J) that the three-dimensional coordinate value of the point P can be obtained by the equation (8). Therefore, the camera parameters (A, H, V, Ch, Ca, Cv) are known, and each C
The coordinates of the CD cameras 22 and 23 are also known. Therefore, unknown is _{I R, J R, Px,} Py, and Pz. Therefore, Px, Py, and Pz are eliminated from the equation (8), and I _R and J
_When the relationship with _R is calculated, it is the first CCD camera 23.
Will be the epipolar line. That is, in equation (8) And again When deployed _{as, a 11 Px + a 12 Py} + a 13 Pz = b 1 ... (9) (I R A XR) Px + (I R Ay R -Hy R) Py + (I R Az R -Hz R) P
_{z = I R Ca R -Ch R} ... (10) a 31 Px + a 32 Py + a 33 Pz = b 3 (11) (J R Ax R -Vx R) Px + (J R Ay R) Py + (J R Az R - the _{vz R) Pz = J R Ca} R -Cv R ... (12). Then, from the value obtained by multiplying Equation (9) by a ₃₃ ,
Subtracting the value obtained by multiplying (11) by a ₁₃ yields d ₁ Px + d ₂ Py = d ₃ (13). Incidentally, it is _{d 1 = a 11 a 33 -a} 31 a 13 d 2 = a 12 a 33 -a 32 a 13 d 3 = b 1 a 33 -b 3 a 13. therefore, And (-d ₁ / d ₂ ) = C ₁ , d ₃ / d ₂ = C ₂ and Py = C ₁ Px + C ₂ (15). Further, when Pz is obtained from the expressions (15) and (9), Pz = e ₁ Px + e ₂ (16) Note that it is _{e 1 = (d 1 a 12} -d 2 a 11) / d 2 a 13 e 2 = (d 2 d 1 -d 3 a 12) / d 2 a 13. Then, by substituting the expressions (15) and (16) into the expression (10), Px is obtained, Becomes _{Here, f 1 = Ax R + C} 1 Ay R + e 1 Az R f 2 = -Hx R -C 1 Hy R -e 1 Hz R f 3 = Ca R -C 2 Ay R -e 2 Az R f 4 = is _{-Ch R + C 2 Hy R +} e 2 Hz R. Further, by substituting the equations (15) and (16) into the equation (12) to obtain Px, Becomes Here, it is _{g 1 = -Vx R -C 1 Vy} R -e 1 Vz R g 2 = -Cv R + C 2 Vy R + e 2 Vz R. Therefore, from the expressions (17) and (18), the epipolar line J _R = 1 is Becomes

Next, the operation of the apparatus configured as described above will be described. The first and second CCD cameras 22 and 23 respectively image the plurality of bonding wires 4 and output their image signals. These image signals are sent to the camera switch 2 respectively.
The switching operation is performed at 4 and the image data is alternately sent to the image processing unit 25.
The image processing unit 25 receives image signals from the CCD cameras 22 and 23, processes them into first image data and second image data, and stores them in an image memory. As described above, the first image data is as shown in FIG.
It is assumed that the second image data is as shown in FIG. Here, pay attention to the bonding wire image 4-1 in the image data of FIG.
A point corresponding to the point Q of 1 is searched for on the second image data. That is, the image processing unit 25 uses the first C
The epipolar line 1 obtained by projecting the line of sight of the bonding wire 4 taken by the CD camera 22 on the second image data is obtained from the equation (19), and the epipolar line 1 is obtained as shown in FIG. It is drawn as an image on the image data of. Next, the image processing unit 25 uses the second image data to determine the epipolar line 1 and the bonding wire images 4-2 and 4 from the second image data.
Find points k ₁ and k ₂ that intersect with −3. by the way,
If there is one intersecting point between the epipolar line 1 and the bonding wire image, the bonding wire image at this intersecting point becomes an image corresponding to the bonding wire image in the first image data, but a plurality of intersecting points k ₁ , K ₂ appears, IC chip 2
The line m passing through the pad 2a of the above and the lead 3a of the frame 3 is obtained and drawn on the second image data. In this case, the respective coordinates of the pad 2a and the lead 3a are known at the time of wire bonding work. Next, the image processing unit 25
Finds the coordinates of the intersection of epipolar line 1 and line m,
Points k ₁ and k ₂ that are close to the intersection coordinates are determined. However, the image processing unit 25 determines that the point k ₁ is close, and determines that the bonding wire image 4-2 corresponds to the bonding wire image 4-1 on the first image data. Thereafter, the image processing unit 25 causes the bonding wire images 4- in the first and second image data to be obtained.
Using 1 and 4-2, the three-dimensional shape of the bonding wire 4 is obtained by the stereo method. As a result, the height, bending, and sag of the bonding wire 4 are inspected. In addition,
When obtaining the bonding wire image 4-3 corresponding to the bonding wire image 4-4, the epipolar line when the bonding wire image 4-4 is taken by the first CCD camera 22 is drawn on the second image data, and A straight line passing through the pad 2a-1 and the lead 3a-1 of the second image data is obtained, and the bonding wire image 4 is obtained from the point closest to the intersection of this straight line and the epipolar line.
-3 will be searched.

In addition, the image processing unit 25 includes the first and second CCD cameras 2
From the image data of any one of the image data obtained by imaging 2, 23, the contact state of the bonding wire 4 with the adjacent bonding wire or the bending state,
Furthermore, the state of contact with the pads and leads is inspected.

As described above, in the above-described embodiment, the epipolar line 1 is drawn to obtain the corresponding bonding wire image in the first and second image data, and the three-dimensional shape of the bonding wire 4 is obtained. Not only planar data but also height and drooping can be inspected. Therefore, the loop shape in the height direction of the bonding wire 4 can be inspected, and it can be inspected with high accuracy whether or not the wire bonding has been reliably performed.

Further, if this method is applied, it is possible to inspect the lead bending of the flat package IC and the lead floating inspection after mounting the flat package IC on the substrate. in this case,
The corresponding point of the target lead can be obtained from the lead of the image data of the other CCD camera and the epipolar line, and the lead can be inspected in a three-dimensional shape.

It should be noted that the present invention is not limited to the above-described embodiment, and may be modified without departing from the spirit of the invention. For example,
The epipolar line of the second CCD camera 23 may be drawn on the first image data to extract the corresponding bonding wire.

[Effects of the Invention] As described in detail above, according to the present invention, even if there are a plurality of bonding wires, not only the planar data of these bonding wires but also a three-dimensional shape can be obtained to inspect for height, droop, etc. It is possible to provide a highly accurate bonding wire inspection method capable of inspecting the loop shape in the height direction of the bonding wire.

[Brief description of drawings]

1 to 4 are views for explaining an embodiment of a bonding wire inspection apparatus to which the present method is applied,
FIG. 1 is a configuration diagram, FIGS. 2 and 3 are schematic diagrams of image data, FIG. 4 is a schematic diagram for explaining a method of obtaining an epipolar line, and FIG. 5 is a diagram for explaining a conventional technique. Is. 1 ... XY table, 2 ... IC chip, 3 ... frame, 4 ... bonding wire, 20,21 ... illumination device, 22 ... first CCD camera, 23 ... second C
CD camera, 24 ... Camera switcher, 25 ... Image processing section.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/60 321 Y 6918-4M 21/66 J 8406-4M

Claims (1)

[Claims] 1. A bonding wire inspecting method for inspecting a three-dimensional shape of a bonding wire electrically connecting terminals to each other, wherein a plurality of the bonding wires are imaged from different directions by a first and a second imaging device, respectively. Then, a line-of-sight image obtained by projecting the line-of-sight when the predetermined bonding wire is captured by the first image-capturing device onto the second image data obtained by the image-capturing of the second image-capturing device, Then, a line passing between each of the terminals connected by the line-of-sight image and the bonding wire is obtained, and then the predetermined bonding wire image on the second image data is extracted from the intersection of the line and the line-of-sight image. Next, from the predetermined bonding wire images in the first and second image data, Bonding wire inspection method and recognizes a three-dimensional shape of the loading wire.