JPH1183456A - Bonding wire inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speed up the detection of a bounding wire height to reduce the inspection time by introducing wire pictures on multiple focal planes into a picture processing device successively. SOLUTION: By using light from a lighting system 4 incident on a bonding wire 1 vertically, that is, a falling illumination, of which light energy is controlled by an illumination control device 8, the light is regularly reflected by the top part of the wire and thereby, an image pickup device 3 picks up an image of luminescent spots of which luminance is higher than that of the periphery on the wire. The image pickup device 3 is attached to a Z stage 5, and a Z control device 7 drives the Z stage 5 and can read the height of the image pickup device 3, that is, the height position of the Z stage 5. When pictures are introduced sequentially while the height of the Z stage 5 is being changed in the optical axis direction, the image pickup device 3 picks up wire pictures on different local planes and hence, a picture processing device 6 introduces the pictures successively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for inspecting the shape and height of a bonding wire on a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, as an apparatus for inspecting the height of a bonding wire, as described in Japanese Patent Application Laid-Open No. 1-244305, a wire in a space illuminated by an illuminating means is used to detect the height of an imaging device. A method for recognizing the wire shape is to take an image at a plurality of different focal planes with different heights and obtain the wire height at each focal plane from the contrast of the wire image at each focal plane and the thickness of the wire image. Proposed.

In Japanese Patent Application Laid-Open No. 6-174439, an image of a wire at a plurality of focal planes, for example, an image at five focal planes, is successively taken into an image processing apparatus, and a change in luminance of the wire is applied to each focal plane. A method of calculating the height of a wire with an accuracy equal to or less than the interval between the wires is shown.

[0004]

However, according to the method described in Japanese Patent Application Laid-Open No. 1-244305, as shown in FIG.
Since a plurality of image sensors 31, 32, and 33 are used to capture the image of the wire in 2 and 103, there is a problem that the cost of the apparatus increases. In addition, the adjustment of the optical axis of each image sensor and the position adjustment of the imaging plane become complicated, and further, since each focal plane is optically fixed, an image of an arbitrary focal plane cannot be captured. There is also a problem.

In the case where images of a plurality of focal planes are captured by changing the height of one imaging device, it takes time to capture all the images if the imaging device is stopped at each focal plane and captured. However, the measurement time of the height of the wire becomes longer, which causes a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to continuously capture images of bonding wires at a plurality of different focal planes by using a single imaging device without stopping the imaging device or using a plurality of imaging elements, so that the inspection time can be reduced. An object of the present invention is to provide a bonding wire inspection apparatus that can be shortened. Another object of the present invention is to provide a bonding wire inspection apparatus capable of capturing an image of a focal plane having an arbitrary height.

[0007]

In order to achieve the above object, a bonding wire inspection apparatus of the present invention illuminates a bonding wire on a semiconductor chip, and picks up an image of the wire illuminated by the illuminating means. Imaging means for obtaining an image signal; height control means for controlling the focal plane of the imaging means by controlling the height of the imaging means; illumination control means for controlling the light emission timing of the illumination means; Image processing means for processing the image signal obtained by the means and inspecting the wire, wherein the height control means controls the driving speed of the imaging means, and the illumination control means adjusts the time of capturing the image signal. The height control means reads the position of the imaging means at the time of capturing the image signal, and controls the light emission timing of the illumination means. By incorporating No. to the image processing unit, characterized in that incorporated into the image processing apparatus sequentially wire images at multiple focal planes.

According to the present invention, in the inspection of the height of a bonding wire, a plurality of images in which the focal plane is changed with respect to the wire height can be continuously produced in the shortest time without stopping the driving of the imaging means. And the inspection time can be shortened.

[0009]

In a preferred embodiment of the present invention, the focal plane of the imaging means can be controlled at an arbitrary position on a bonding wire. Thereby, an image of the focal plane at an arbitrary height can be captured.

Preferably, the imaging means has an imaging optical system having a depth of focus that does not cause blurring of a captured image due to movement of a focal plane during the imaging. Further, the imaging unit may include a shutter mechanism, the illumination unit may be constantly turned on by the illumination control unit, and the shutter mechanism may have a shutter opening / closing timing controlled in accordance with image signal capture of the imaging unit. .

[0011]

【Example】

(First Embodiment) FIG. 1 is a block diagram of a bonding wire inspection apparatus according to this embodiment. In the figure,
1 is a bonding wire on a semiconductor chip which is an inspection object, 2 is an optical device having an imaging system such as an optical microscope, 3 is an imaging device such as a CCD camera, and 4 is an illumination provided with a light source for illuminating the inspection object 1 The device 5 is a Z stage that drives the imaging device 3 and the illumination device 4 in the optical axis direction of the imaging system, 6 is an image processing device that takes in and processes an image signal from the imaging device 3, and 7 controls driving of the Z stage 5. Control device, 8
Is a lighting control device for controlling the lighting and brightness of the lighting device 4, and 9 is a central control device for controlling the operation of the image processing device 6, the Z control device 7 and the lighting control device 8.

In the bonding wire inspection apparatus having the above-described configuration, when the light amount is controlled by the illumination control device 8 and the light vertically incident on the bonding wire 1 from the illumination device 4, that is, so-called epi-illumination, the top portion of the wire is used. , And the image pickup device 3 picks up a bright spot image having a higher luminance than the periphery of the wire as shown in FIG.

The imaging device 3 is mounted on the Z stage 5. The control device 7 drives the Z stage 5, and can read the height of the imaging device 3, that is, the height position of the Z stage 5. When images are sequentially captured while changing the height of the Z stage 5 in the optical axis direction, the imaging device 3 captures wire images at different focal planes, and the image processing device 6 continuously captures the images.

FIG. 3 is a diagram showing a positional relationship between the bonding wire 1 and the image pickup device 3, wherein F1 to F1 in FIG.
F5 indicates the focal plane of the imaging device 3. When the images at the focal planes F1 to F5 are captured while moving the imaging device 3 in the vertical direction, the brightness of the bright spot image on the wire shown in FIG. Changes occur. After successively capturing five images obtained on the focal planes F1 to F5, the image processing device 6 calculates the in-focus position of the wire top from the luminance change of the bright spot image on the wire.

Next, a method of continuously capturing images of the focal planes F1 to F5 without stopping the driving of the Z stage will be described. Here, FIG. 4 is a timing chart showing the relationship among Z stage drive, illumination control, and Z stage position reading.

(1) The central controller 9 sends an image capture start command to the image processor 6, the Z controller 7, and the illumination controller 8. (2) The Z stage 5 starts constant-speed driving with a preset driving amount by the Z control device 7. (3) At time tl when the Z stage 5 reaches the constant speed v,
The image processing device 6 controls the illumination control device 8 to turn on the illumination device 4 with the strobe light for, for example, T1 = 500 μsec, and instructs the Z control device 7 to read the position of the Ζ stage 5. The Z control device 7 stores the position zl of the Z stage 5 read here. At this time, the image of the bonding wire 1 illuminated by the strobe lighting is output from the imaging device 3 as an image of the focal plane F1 and taken into the image processing device 6.

(4) T2 = 1 / 60s from time tl
At time t2 after ec, the image processing device 6 controls the illumination control device 8 again to set the illumination device 4 to, for example, T1 = 500 μsec.
c and the Z control device 7
A command to read the position of the stage 5 is issued. Z control device 7
Stores the position z2 of the Z stage 5 read out here. At this time, the image of the bonding wire 1 illuminated by the strobe lighting is output from the imaging device 3 as an image of the focal plane F2, and is taken into the image processing device 6.

(5) By repeating the above operations, the images of the focal planes F3, F4, and F5 at the times t3, t4, and t5 are output from the image pickup device 3 and taken into the image processing device 6, and Z The constant speed drive of the stage 5 is stopped. If the illumination lighting and the reading of the Z stage position (z5) at the time t5 at which the last image F5 is captured are completed, the Z stage 5 can be stopped before the output of the image of F5 is completed.

In the case where the field storage of the NTSC CCD camera is used as the imaging device, 1/60 sec.
Since one-field image output is performed at c, T2 = 1
Images can be continuously captured at the shortest interval of / 60 sec. The flash lighting time of the T1 is
Needless to say, it is set optimally according to the light amount of the illumination device 4 and the sensitivity of the imaging device 3.

Here, the images at the focal planes F1 to F5 captured by the image processing device 6 are images captured at intervals of a distance of v / 60.
As described in Japanese Patent No. 437, the image processing apparatus 6 calculates the grayscale value of each image to obtain the wire-top in-focus plane as the in-focus plane within the interval between the captured images. From the values of z1 to z5 stored in the device 7, the central control device 9 calculates the position of the Z stage on the wire-top focal plane.

Here, supplementary description of image capture on a certain focal plane will be given. For example, an image on the focal plane F3 is obtained at time t
3, the image is captured by the imaging device by the illumination turned on during the time T1, and at this time, the Z stage 5 is moving at a constant speed v. Therefore, an image in which the focal plane has changed by the distance of (v × T1) is captured by the imaging device 3. Therefore, in order to prevent the captured image from being blurred, the optical device 2 may include an aperture (not shown) or a lens (not shown) so as to have an optical characteristic with a focal depth larger than (v × T1).

Further, in the continuous image capturing, the central control unit 9 uses an input device (not shown) from an input device (not shown) as a reference focal plane in advance before starting the image capturing, for example, the height Z of F3 and the distance d between the focal planes. To enter. Thus, it is possible to set a range in which an image is captured on an arbitrary focal plane that is not fixed with respect to the wire to be measured. The central controller 9 can control the Z controller 7 so that the driving speed v of the Z stage 5 is maximized based on the distance d and the depth of focus of the optical device 2 input here.

(Second Embodiment) In the first embodiment, a CCD
Although the description has been given of the image capturing in the field accumulation of the camera, a digital camera or the like is used as the imaging device 3 in this embodiment. These cameras reduce the image output time by 1 /
It can be shorter than 60 seconds, the light amount of the illumination device 4, the depth of focus of the optical device 2, the driving speed v of the Z stage 5,
By appropriately setting, it is possible to further speed up the continuous capture of images.

Further, in the first embodiment, an image projected on the image pickup device 3 is formed only during the time when the lighting device 4 is turned on. In this embodiment, the lighting device 4 is always turned on. A shutter mechanism was provided in the imaging device 3, and the amount of light was controlled by controlling the shutter opening / closing timing to form an image.

[0025]

As described above, according to the present invention, it is possible to perform a continuous capture of bonding wire images on a plurality of focal planes by one imaging device in a short time, thereby detecting the height of the bonding wire. Can be speeded up. Also, since multiple imaging devices are not used,
There is also an effect that the configuration of the optical system is simplified and the adjustment method is simplified. Furthermore, an image can be captured at a focal plane of an arbitrary height.

[Brief description of the drawings]

FIG. 1 is a block diagram of a bonding wire inspection apparatus according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating bright spots on a bonding wire.

FIG. 3 is a diagram showing a positional relationship between a bonding wire and a height of an imaging device.

FIG. 4 is a timing chart showing the relationship between Z-stage driving, illumination control, and Z-stage position reading during image capture.

FIG. 5 is a diagram showing a part of the configuration of a conventional bonding wire inspection device.

[Explanation of symbols]

1: bonding wire on semiconductor chip, 2: optical device, 3: imaging device, 4: illumination device, 5: Z stage,
6: Image processing device, 7: Δ control device, 8: Illumination control device, 9: Central control device, 10: Bright spot on bonding wire, 11: Semiconductor chip, 12: Inner lead, 1
3: focal plane of imaging device, 21 to 23: half mirror, 2
4: Objective lens, 31 to 33: Image sensor, 101 to 10
3: focal plane.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/66 G06F 15/62 405B

Claims (4)

[Claims] An illumination unit for illuminating a bonding wire on a semiconductor chip, an imaging unit for capturing an image of a wire illuminated by the illumination unit to obtain an image signal, and controlling the height of the imaging unit to control the imaging. Height control means for controlling a focal plane of the means, illumination control means for controlling light emission timing of the illumination means, and image processing means for processing an image signal obtained by the imaging means and inspecting a wire. A bonding wire inspection device, wherein the height control unit controls the driving speed of the imaging unit, and the illumination control unit controls the light emission timing of the illumination unit in accordance with the capture of an image signal; The height control means reads out the position of the imaging means at the time of signal capture, and captures the image signal obtained from the image capture means into the image processing means, so that the A bonding wire inspection apparatus wherein wire images at a number of focal planes are continuously taken into the image processing apparatus. 2. The bonding wire inspection apparatus according to claim 1, wherein a focal plane of said imaging means can be controlled at an arbitrary position of the bonding wire. 3. The bonding wire according to claim 1, wherein the imaging unit includes an imaging optical system having a depth of focus that does not cause blurring of a captured image due to movement of a focal plane during the imaging. Inspection equipment. 4. The imaging means includes a shutter mechanism,
The lighting means is always turned on by the lighting control means,
4. The bonding wire inspection apparatus according to claim 1, wherein timing of opening and closing the shutter of the shutter mechanism is controlled in accordance with capturing of an image signal by the imaging unit.