JP3272640B2 - Bonding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding apparatus, and more particularly to a bonding apparatus for connecting a pad as an electrode thin film of a semiconductor chip as an object to be processed and a lead provided on a lead frame by bonding. The present invention relates to a bonding apparatus that performs relative positioning between an object and a bonding tool by using an image captured from a bird's-eye view by a camera.

[0002]

2. Description of the Related Art A bonding apparatus for connecting a pad on a semiconductor chip and a lead by bonding is well known in the field of semiconductor processing. The bonding apparatus includes a wire bonding apparatus that connects an object to be bonded by a thin metal wire such as Au (gold) or Al (aluminum), and a tape bonding apparatus that uses a tape.

[0003] As the former wire bonding apparatus,
Nail head bonding is a common method, including thermocompression bonding using pressure bonding with heat applied, thermosonic bonding using ultrasonic vibration energy with heat applied, and room temperature bonding. Ultrasonic wedge bonding using ultrasonic processing.

In the latter tape bonding apparatus, a tape to be used is usually provided with windows at regular intervals by bonding a copper foil to a polyimide tape, and the windows correspond to pads as electrodes of a semiconductor chip such as an IC. Bumps (buds) as gold bumps are formed on the pads.
mp, bumps) are applied, and pressure is applied by a bonding tool as a processing tool at a position where the lead and each bump overlap, and at the same time, electric current is heated to perform bonding.

In both the wire bonding apparatus and the tape bonding apparatus described above, the position of the semiconductor chip and the lead (wire bonding) or the position of the semiconductor chip (tape bonding) as the workpiece at the time of the bonding processing is at the correct processing position. It is necessary to perform positioning with a processing tool after confirming whether or not there is an object. Usually, for this positioning, an image obtained by optically imaging the work from above with a camera such as an ITV A displacement of the workpiece is detected by a method such as collating an image generated by a signal with a standard position pattern, and bonding processing is performed after the displacement is correctly aligned.

FIG. 4 is a block diagram showing a configuration of a positioning unit in a conventional bonding apparatus. FIG. 4 shows a case of a wire bonding apparatus as an example. As shown in FIG. 4A, a lens 101b constituting an optical system having a preset focal length, and a camera 101a are a workpiece as a subject. From above, and sends the acquired image signal S to the image processing unit 103.

[0007] The camera 101a and the lens 101b are usually integrated, and an imaging position of a subject is set by a suspension mechanism 105 driven by a camera driving unit 102. The camera drive unit 102 includes an actuator, a motor, and the like driven by a drive control signal D output from the drive control unit 104. The image processing unit 103 generates a bird's-eye view image of the subject based on the input image signal S, compares the image with a standard pattern indicating the correct position of the subject, and uses the difference as displacement data E representing the displacement of the subject. Is sent to a position matching unit (not shown), whereby the mounting structure and the like of the subject are driven to perform position matching for processing.

FIG. 4B also shows a focus range a for the subject (workpiece) imaged in this manner.
That is, an image is captured so as to include the workpiece in the focal range a shown in FIG.

FIG. 5 is a side view showing an example of a workpiece. FIG. 5 is a side view of a workpiece to be processed by the wire bonding apparatus, and shows a semiconductor chip 1001 such as an IC.
And a lead 1002 to be wire-bonded to the semiconductor chip 1001.
The lead 2 and the lead 2 are separated from each other, and a gap therebetween is formed by bonding using a thin metal wire such as Au, Al or the like, and is bridged.

The upper surface of the semiconductor chip 1001 and the lead 1
A precondition for good imaging is to set the focal range in accordance with the variation of the chip step 1003 of the difference from the upper surface of 002.

[0011]

In the above-mentioned conventional bonding apparatus, positioning with respect to a workpiece is performed using an image signal captured by a camera using a lens as an optical system having a single focus. The focus cannot be changed corresponding to the height of the workpiece, that is, the variation of the chip step. Therefore, when the chip step is large, the work is performed based on one of the following and Was taken in the focal range to perform imaging.

An image is taken using a lens having a large depth of focus. An image is taken using a mechanism for raising and lowering the lens. An image is taken using a mechanism for moving the workpiece up and down. However, in the case of, the focal range is enlarged, the resolution is reduced, and the positioning accuracy is deteriorated.
In other cases, it is necessary to add a mechanism for moving the lens up and down, and time for moving the lens up and down is required. In each case, a mechanism for moving the workpiece up and down is required every time an image is taken. There is a problem in that the weight of the mechanism itself is large, and time is required for the vertical movement.

An object of the present invention is to solve the above-mentioned problems and to provide a bonding apparatus having a simple configuration capable of accurately capturing an image of a workpiece having a variation in chip steps.

[0014]

The present invention has the following means in order to achieve the above object. That is, in the first configuration of the present invention, when a pad serving as an electrode of a semiconductor chip and a lead of a lead frame are connected by bonding, the semiconductor chip and the lead of a workpiece to be processed are viewed from above with a camera. In a bonding apparatus for performing alignment of a relative position between a bonding tool and the workpiece, the imaging of the object is performed in accordance with a variation in a step between a top surface of a semiconductor chip and a top surface of a lead. The focal range, which is an area, corresponds to each of two focal ranges: a near-focus range close to the imaging surface and a far-focus range set farther than the near-focus range .
Has two independent optical paths with different imaging planes
An optical system, and the subject is positioned at the near position through the optical system.
In one of the focus range and the far position focus range
An imaging unit that includes two cameras for imaging and acquires an image signal of the subject; and an image signal of the subject acquired by the imaging unit is compared with a standard pattern indicating a normal position of the subject during bonding processing. Relative position difference detection means for detecting a relative position difference between a processing tool and the subject from an expected state; and the processing tool and the subject during bonding processing based on the relative position difference detected by the relative position difference detection means Bonding position aligning means for ensuring position alignment with the bonding position.

[0015]

Further, a second configuration of the present invention is the first configuration ,
Instead of the imaging means of the configuration, the optical system having two systems optical path of mutually independent for a common imaging surface corresponding to each of said distal position focus range and the near position focus range, 2 lines with of this optical system A shutter section that can switch the optical path of the shutter, and any one of the near-position focal range and the far-position focal range corresponding to the two optical paths switched by the shutter section, or the shutter section is opened. the front and a single camera for imaging the focus range of both the far position focus range and the near position focus range as
It is provided with an imaging means for acquiring an image signal of the subject.
is there.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a bonding apparatus for connecting a pad as an electrode structure of a semiconductor chip to a lead of a lead frame, an image generated by using an image signal obtained by a bird's-eye image of a workpiece is usually used. Is used to position the workpiece.

In imaging an object to be processed by a conventional bonding apparatus, a lens (optical system) having a single focal point, that is, a single focal range formed at a certain distance from the object. , The position of the focus range cannot be changed in accordance with the increase in the height of the workpiece (subject). Therefore, when the step between the pad to be bonded and the lead varies, Has used a lens with a so-called deep depth of focus, that is, using a lens with a long focal range, or equipped with a mechanism to move the lens or the workpiece up and down. The point is as described above.

In the present invention, for example, as shown in FIG. 1, the optical system 1c having two optical paths formed optically and the camera (1) 1a and the camera (2) 1b are combined to process. When the chip step of the object is normal, a near-position focus range is formed in a distance range that allows the object to be included in the predetermined fixed position with respect to the workpiece, and when the chip step is large, A far-point focal range is formed at a position closer to the workpiece, and in any case, the workpiece can be accurately imaged in a state where the workpiece can be present in the focal range. It is possible.

In FIG. 1, the above-mentioned near focus range is set by the camera (1) 1a and the optical system 1c, and the far focus is set closer to the workpiece by the camera (2) 1b and the optical system 1c. An image is formed by forming a range. Which of the two different focus ranges is selected is manually set in advance based on the workpiece.

In FIG. 1, an arm 8 and a capillary 9 are bonding tools necessary for bonding, a semiconductor chip 14 and a lead 15 mounted on a carrier section 10 are a workpiece (subject), and position control is performed. Unit 4, drive unit 5, XY stage 6, bonding head 7
Sets the position of the workpiece, the image processing unit 2 generates a captured image, and the CPU 3 controls the overall operation.

In the wire bonding apparatus, heat is applied to the workpiece by several hundred degrees, and a heater block 11 and a temperature controller 12 are provided for this purpose.

[0023]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention. The configuration of the embodiment shown in FIG. 1 is an example of a wire bonding apparatus, and has an optical system 1c that forms the same focal range at two positions, far and near, and two far and near focal points formed by the optical system 1c. Based on two ITV cameras (1) 1a and 1 (b) for capturing two optical images obtained for a workpiece included in the range, and an image signal P acquired by the two cameras. And an image processing unit 2 for generating a bird's-eye view image of the semiconductor chip and the lead and detecting a displacement of a workpiece, and a processing and control program,
A CPU 3 for controlling the overall operation, a position control unit 4 for transmitting a position control signal for controlling the position of the workpiece, and a drive signal for driving the workpiece in response to the position control signal output from the position control unit 4 The driving unit 5 that is generated, the XY stage 6 that is mounted on the base 13 and moves the processing tool in the X and Y directions (horizontal direction), gives the movement of the processing tool in the Z direction (vertical direction), and provides the processing tool and imaging Bonding head 7 for mounting the system and arm 8 as a processing tool
And a capillary 9, a carrier unit 10 on which a workpiece is placed, a heater block 11 for applying heat to the workpiece,
A temperature controller 12 for controlling a heating temperature of the heater block 11, a base 13 on which an imaging system and a processing system are mounted,
FIG. 1 also shows a support arm 20 for fixing the imaging system to the bonding head 7 and data buses 30 and 40 together with a semiconductor chip 14 to be processed and leads 15.

Among these components, the camera (1) 1a, the camera (2) 1b and the optical system 1c form an image pickup means, the image processing section 2 and the CPU 3 form a relative position difference detection means, and the CPU 3 The position control unit 4, the drive unit 5, the XY stage 6, and the bonding head 7 form a bonding position alignment unit.

Next, the operation of this embodiment will be described.
The optical system 1c attached to the bonding head 7 via the support arm 20 and the imaging system of the camera (1) 1a and the camera (2) 1b are used for the semiconductor chip 1 of the workpiece.
According to the size of the step between the lead 4 and the lead 15, a near-focus range is formed at a predetermined fixed position by the camera (1) 1a and the optical system 1c for imaging in the case of a normal chip step. An image is taken with the workpiece included in the near position focus range.

When the chip step is large and the workpiece protrudes from the above-described focal position at the near position, it is manually switched in advance so as to form a focal position at a far position.

As described above, if the near-position and far-position focal ranges can be formed, it is possible to very easily cope with accurate imaging of a difference in chip level difference of a workpiece.

FIG. 2 is a view for explaining imaging of a workpiece in the embodiment of FIG. As shown in FIG.
When two imaging cameras are used, the combination of the camera (1) 1a and the optical path (1) 1005 is used when the imaging condition is to form a far-position focal range, that is, the step between the semiconductor chip surface and the lead surface. Is selected when the workpiece deviates from the normal focus range and the workpiece cannot be properly imaged, and the combination of the camera (2) 1b and the optical path (2) 1006 is used in such a case. It is selected to form the focal range of the position.

The camera (1) 1a and the optical path (1) 10
The combination with 05 is used to form a near focus range for a normal chip step.

FIG. 2B shows an optical path (1) and a near-focus range a of the optical path (1) formed by using the camera (1) 1a, an optical path (2) and the camera (2) 1b. 6 shows a far-field focal range b of an optical path (2) formed by utilizing.

In this embodiment, the near focus range a of the optical path (1) and the far focus range b of the optical path (2) are formed adjacent to each other. A focus range may be set, and these are set to a desired state based on the content of the workpiece, the configuration of the imaging system, and the like.

Returning to FIG. 1, the description of the operation of the embodiment will be continued. Camera (1) 1a or Camera (2) 1b
The image signal P including the semiconductor chip 14 and the lead 15 of the workpiece acquired in the step (1) is sent to the image processing unit 2. The image processing unit 2 includes an image generation unit 21 and a pattern recognition unit 22.

The image generator 21 receives the supplied image signal P
And generates a subject pattern as a still image under the control of a program of the CPU 3 received via the data bus 30 and supplies the pattern to the pattern recognition unit 22.

The pattern recognition unit 22 performs pattern matching between the subject pattern provided from the image generation unit 21 and a standard pattern at a normal position of a built-in workpiece in advance.
The shift of the subject pattern, that is, the shift of the current position of the workpiece from the correct position should be detected, and this shift information is sent to the CPU 3 via the data bus 30.

The CPU 3 calculates position shift correction data for correcting the position shift of the workpiece based on the provided position shift information, and sends the data to the position control unit 4 via the data bus 40. The position control unit 4 receives the provided positional deviation correction signal and sends out a position control signal C for correcting the relative position of the bonding tool with respect to the workpiece to a correct state.

The position control signal C is obtained by moving the XY stage 6 placed on the base 13 on the X and Y axes and the bonding head 7 on which the arm 8 and the capillary 9 as a bonding tool are mounted on the Z axis. Move it up,
The drive unit 5 outputs an X-direction drive signal L, a Y-direction drive signal M, and a Z-direction drive signal N as inputs for matching the relative position of the bonding tool with respect to the workpiece 3
A direction control signal.

In this manner, the capillary 9 provided at the tip of the arm 8 ensuring the relative positional alignment with the workpiece
Is supplied with a fine gold wire from a wire feeding mechanism (not shown).
In the case of bonding by a compression (thermo-compression) method, the heater block 1 having a temperature included in the carrier unit 10 and controlled by the temperature controller 12 is used.
After the first bonding by thermocompression of the workpiece heated (about 300 to 350 ° C.) to the semiconductor chip 14 in step 1 is completed, the wire is transferred to the lead 15 and the second bonding by thermocompression is performed. Thereafter, the wire is cut, and thus the bonding is completed, and the process proceeds to the next bonding step.

FIG. 3 is a block diagram showing a partial configuration of the second embodiment of the present invention. In the second embodiment of the present invention, parts other than the imaging system having the partial configuration shown in FIG.
Since all of the components are the same as those shown in FIG. 1, a detailed description of these same components will be omitted. In the second embodiment, an optical path (3) 1007 and an optical path (4) 1008 are formed as two independent optical paths that form a near-focus range and a far-focus range and have a common imaging surface. The optical path (3) 1007 and the optical path (4) 1008 are each mechanically closed by a shutter 16b, and only one of the optical paths is optically closed. Since imaging using these two optical paths shares the same imaging surface, it is possible to perform imaging with one camera (1) 1a.

A shutter controller 16a indicated by a chain line.
Forms a shutter section 16c with the shutter 16b, and the shutter controller 16a sends a shutter control signal SH for controlling the operation of the shutter 16b. As shown in FIG. 3B, the shutter 16b includes a half mirror H that splits the input light W into two, and shutter elements S1 and S2 as mechanical shutter elements that selectively close an optical path. , S
2 is selectively closed by the shutter control signal SH, or both of the shutter elements S1 and S2 are set to the open state (light traveling state), and the selected one of the near focus range and the far focus range is selected. Alternatively, it is possible to capture a target scene captured by both.

In the second embodiment, a mechanical shutter is used to selectively close two optical paths or to control both of them to be in an open state. other shutter having, for example, by an applied voltage are those which can be implemented easily by L _i N _b O ₃ switching such as switching the optical path of the electro-optical member utilizing crystals that change the refractive index.

In this way, it is possible to perform a bonding process based on high-precision imaging data with a simple configuration and premised on position alignment. Although FIGS. 1, 2 and 3 show the case of a wire bonding apparatus as an example, the overall configuration is also different in the case of tape bonding, but the relative position alignment between the workpiece and the bonding tool based on imaging is not described. Obviously, it can be easily implemented almost as well.

[0042]

As described above, according to the present invention, in a bonding apparatus for connecting a pad serving as an electrode of a semiconductor chip to a lead provided on a lead frame, the relative positions of a bonding tool and a workpiece are matched. In the bird's-eye view imaging of the workpiece to be performed, a focus range as an imaging range having a predetermined distance is set as two imaging ranges of a near position and a far position, corresponding to a step between the pad surface and the lead surface. By doing so, it is possible to obtain an image having a deep depth of focus in a state where the resolution is preserved, eliminating the need for focusing by moving the camera or the subject up and down,
This has the effect that high-speed switching of the focus range and remarkable reduction in size and weight of the apparatus can be ensured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a diagram illustrating imaging of a workpiece in the embodiment of FIG. 1;

FIG. 3 is a block diagram showing a partial configuration of a second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a positioning unit in a conventional bonding apparatus.

FIG. 5 is a side view of a workpiece to be processed by the wire bonding apparatus.

[Explanation of symbols]

 1a Camera (1) 1b Camera (2) 1c Optical System 1d Optical System 2 Image Processing Unit 3 CPU 4 Position Control Unit 5 Drive Unit 6 XY Stage 7 Bonding Head 8 Arm 9 Capillary 10 Carrier Unit 11 Heater Block 12 Temperature Controller 13 Base 14 semiconductor chip 15 lead 16a shutter controller 16b shutter 16c shutter section

Claims (2)

(57) [Claims] A pad as an electrode of a semiconductor chip;
When connecting the lead of the lead frame by bonding, the semiconductor chip and the lead of the workpiece to be processed are imaged from a bird's eye view with a camera, and the relative positions of the bonding tool and the workpiece are aligned. In the bonding apparatus, the focal range, which is the imaging region of the subject, is changed to a near-focus range close to the imaging surface and the near-focus range in response to a step difference as a height difference between the upper surface of the semiconductor chip and the upper surface of the lead. Imaging corresponding to each of the two focal ranges with the far-position focal range set farther than the range
Optics having two independent optical paths with different surfaces
System and the near focus on the subject via the optical system.
Imaging in either one of the focal range
Imaging means for obtaining an image signal of the object, comprising : two cameras for performing bonding processing by comparing the image signal of the object acquired by the imaging means with a standard pattern indicating a normal position of the object; A relative position difference detecting means for detecting a relative position difference between a tool and the subject from an expected state; and the processing tool and the subject during bonding processing based on the relative position difference detected by the relative position difference detecting means. And a bonding position aligning means for ensuring the position alignment. 2. A pad as an electrode of a semiconductor chip,
Connect the lead of the lead frame by bonding
The semiconductor chip of the object to be processed
And a bonding tool
For aligning the relative positions of the workpiece and the workpiece
In the device, the upper surface of the semiconductor chip is
According to the variation of the step as a height difference, the object
The focal range, which is the imaging area of
Range and far position set farther than the near focus range
Imaging corresponding to each of the two focal ranges with the focal range
Light having two independent optical paths with a common surface
Switchable between optical system and optical system of this optical system
Switchable with this shutter section
The near-position focal range corresponding to the two optical paths and
Any one of the focus positions in the telephoto position focus range, or
With the shutter part open, the near focus range and the front
One camera that captures images in both focal ranges
Imaging means for obtaining an image signal of the object and a camera
And the image signal of the subject acquired by the imaging means and
Check the pattern against a standard pattern that indicates the normal position of the subject.
There should be a processing tool and the subject at the time of loading processing
Relative position difference detection means for detecting a relative position difference from the state
And the relative position difference detected by the relative position difference detecting means.
Based on the above processing tool at the time of bonding
Bonding alignment to ensure alignment with the subject
A bonding apparatus comprising: a joining unit.