JP2012059933A - Die bonder and die-bonding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die bonder that improves the pickup accuracy and productivity.SOLUTION: A die bonder and a die-bonding method include an image processing apparatus in which a transfer tool 403 is rotated by a rotation mechanism 408 by a predetermined rotation angle, the bottom surface of the transfer tool 403 is photographed by a camera 405 per rotation angle, the rotation center of the transfer tool 403 is calculated from the photographed image and the deviation amount θ per rotation angle is registered in a database, the position correction for the transfer tool 403 is performed based on the database each time a semiconductor chip 402 is mounted on a work 404.

Description

  The present invention relates to a die bonder and a die bonding method, and more particularly, to misalignment correction when exchanging a die pickup tool.

  Conventionally, a positional deviation that occurs when a transfer tool (a die pick-up tool such as a collet) picks up a die (semiconductor chip) from a wafer is imaged with a camera (hereinafter referred to as an undervision camera) from the back of the die after pick-up. By detecting the center position of the back surface of the die by image recognition from the captured image, the amount of deviation is calculated and corrected, and the die bonding accuracy to a workpiece such as a substrate (substrate) or a frame is improved (patent) Reference 1).

JP 2003-77942 A

In the above-described prior art, before picking up a die from a wafer, the surface of the die in the wafer is imaged with a camera (referred to as a wafer camera), and the center position of the die is detected by image recognition from the captured image. Calculate and correct the amount to pick up. That is, the die position is recognized, and the center position (Xd, Yd, θd) of the die and the center position (Xt, Yt, θt) of the transfer tool are matched and picked up. At this time, it is necessary to slightly rotate the transfer tool in order to match θd and θt. However, the rotation center of the transfer tool is not always at the center of the bottom surface of the transfer tool. Accordingly, the X position and the Y position after the rotation (θ) correction are shifted (θ deviation). For this reason, there has been a problem that the transfer tool cannot accurately pick up the die.
In addition, if the rotation mechanism that rotates the transfer tool has poor linearity with respect to the command value due to mechanical resistance such as sliding resistance, there is a problem that θ shift occurs depending on the rotation angle, and the transfer tool cannot pick up the die accurately. there were.
Therefore, the image is picked up by the undervision camera from the back surface of the die after picking up, and the deviation is corrected by recognizing the position of the die. However, since imaging with an undervision camera is required for each pickup, the tact time (the time from picking up to mounting on a work (substrate or frame)) becomes longer, and productivity is lowered.
In view of the above problems, an object of the present invention is to provide a die bonder and a die bonding method in which the accuracy of pickup is increased and the productivity is improved.

In order to achieve the above object, the die bonder of the present invention creates correction data for θ rotation of the transfer tool in advance using a camera and corrects it at the time of mounting.
That is, the die bonder of the present invention includes a transfer tool that takes out a semiconductor chip and mounts it on a workpiece, a rotation mechanism that rotates the transfer tool, a camera that images the bottom surface of the transfer tool, and the transfer tool. The image is rotated at a predetermined rotation angle, the bottom surface of the transfer tool is imaged by the camera at each rotation angle, the rotation center of the transfer tool is calculated from the captured image, and the θ deviation amount at each rotation angle And a position control device that corrects the position of the transfer tool based on the database each time the semiconductor chip is mounted on the workpiece.
In the die bonder of the present invention described above, the θ shift amount registered in the database is a shift amount in the X direction, Y direction, and θ direction for each rotation angle.
Furthermore, in the die bonder according to the present invention, the image processing device is configured such that the rotation center of the transfer tool is determined from a rotation trajectory about an arbitrary point of the bottom image of the transfer tool imaged by the camera at each rotation angle. Is calculated.

In the die bonding method of the present invention, the transfer tool is rotated at a predetermined rotation angle, the bottom surface of the transfer tool is imaged by the camera at each rotation angle, and the rotation center of the transfer tool is determined from the captured image. The calculated and registered θ shift amount for each rotation angle is registered in a database, and the position of the transfer tool is corrected based on the database each time a semiconductor chip is mounted on a workpiece.
Furthermore, the die bonding method of the present invention calculates the rotation center of the transfer tool from a rotation locus for an arbitrary point of the image of the bottom surface of the transfer tool imaged by the camera for each rotation angle. It is.

  According to the present invention, it is possible to provide a die bonder and a die bonding method with improved productivity and mounting accuracy.

It is the conceptual diagram which looked at the die bonder of one Example of this invention from the top. It is typical sectional drawing for demonstrating the function of the camera in one Example of the die bonder and die-bonding method of this invention. It is a figure for demonstrating one Example of the control system of the position alignment mechanism of this invention. It is a schematic diagram for demonstrating operation | movement of one Example of the die bonder and die-bonding method of this invention. It is a figure which shows one Example of the data table produced in the die bonder and die bonding method of this invention. It is a figure for demonstrating (theta) shift | offset | difference of the bottom face (back surface) of the transfer tool 403 in the die bonder and die bonding method of this invention. It is a flowchart for demonstrating one Example of the database creation process of the rotation center of the transfer tool of the die bonder and die bonding method of this invention. It is a figure for demonstrating one Example of the transfer tool used for the die bonder and die-bonding method of this invention.

The present invention creates correction data for θ rotation of the transfer tool by using a camera such as an under vision camera each time the transfer tool is replaced. This automatically corrects the deviation of the θ rotation during mounting. As a result, the mounting accuracy is improved without reducing productivity.
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of each drawing, components having common functions are denoted by the same reference numerals, and the description thereof is omitted to avoid duplication as much as possible.

First, a basic configuration of a die bonder will be described with reference to FIG. FIG. 1 is a conceptual view of a die bonder according to an embodiment of the present invention as viewed from above. Reference numeral 100 denotes a die bonder, 11 denotes a wafer supply unit, 12 denotes a workpiece supply / conveyance unit, and 13 denotes a die bonding unit. As described above, the die bonder 100 includes the wafer supply unit 11, the workpiece supply / conveyance unit 12, and the die bonding unit 13.
In the wafer supply unit 11, 111 is a wafer cassette lifter, and 112 is a pickup device. In the workpiece supply / conveyance unit 12, 121 is a stack loader, 122 is a frame feeder, and 123 is an unloader. In the die bonding part 13, 131 is a preform part, and 132 is a bonding head part.

In FIG. 1, a wafer cassette lifter 111 has a wafer cassette (not shown) filled with wafer rings, and sequentially supplies the wafer rings to the pickup device 112. The pickup device 112 moves the wafer ring so that the die to be picked up can be picked up from the wafer ring by the transfer tool.
The stack loader 121 supplies a work (substrate or substrate) to which the die is bonded to the frame feeder 122. The frame feeder 122 conveys the workpiece to the unloader 123 via two processing positions on the frame feeder 122 (processing positions of the preform part and the die bonding part). The unloader 123 stores the conveyed work.
The preform part (die adhesive application device) 131 applies the die adhesive to the work conveyed by the frame feeder 122. The bonding head unit 132 picks up and picks up a die to be picked up from the pickup device 112 and moves the die to a bonding point on the frame feeder 122. Then, the bonding head unit 132 lowers the die at the moved bonding point, and mounts the die on the bonding point on the workpiece coated with the die adhesive. A film-like adhesive is attached in advance to the back surface (adhesion surface) of the die.

The basic functions of the camera used for the die bonder will be further described with reference to FIG. FIG. 2 is a schematic cross-sectional view for explaining the function of the camera in one embodiment of the die bonder of the present invention. 2A is a diagram viewed from the lateral direction (Y direction), and FIG. 2B is a diagram viewed from the upper direction (Z direction). Note that FIG. 2 illustrates a camera in a die bonder and a captured image thereof. For this reason, illustration and description are omitted for functional parts (other components, connection) not related to the description. 232 is a processing position of the preform portion, 233 is a processing position of the die bonding portion, 211 is a wafer of a wafer ring mounted on the pickup device 112, 201 is a wafer camera that images the die of the wafer 211 from above the pickup device 112, 212 Is a workpiece carried into the preform portion 232, 202 is a camera for imaging the die bonding position (bonding point) of the preform portion 131, 213 is a workpiece carried into the processing position 233 of the bonding head portion, and 203 is a bonding head portion. 251 is a pitch between the processing position 232 of the preform part and the die bonding part 233. The workpieces 212 and 213 are loaded from the loader while keeping the interval of the pitch 251 and transferred to the unloader.
The camera is, for example, a camera using a CCD image sensor or a CMOS image sensor.

In FIG. 2, the camera 201 captures an image of the pattern surface (front surface) of the wafer 211 of the pickup device 112, and the center position of one die and the center of the transfer tool of the pickup device 112 by known image processing such as pattern recognition. The position is corrected so as to eliminate the deviation from the center position of the push-up block.
Similarly, the camera 202 captures an image of a predetermined die bonding position (bonding point) of the preform portion 232, and the position shifts so that the preform resin is applied to the die bonding position by a known image processing such as pattern recognition. Make corrections and apply preform resin.
Similarly, the camera 203 captures an image of a predetermined die bonding position of the die bonding unit 233, and a well-known image processing such as pattern recognition enables the die to be mounted at the center position of the die bonding position. Correct the misalignment and mount the die.

  Next, the positional deviation correction will be further described with reference to the alignment mechanism shown in FIG. FIG. 3 is a diagram for explaining an embodiment of the control system of the alignment mechanism of the present invention. Reference numeral 301 denotes an image processing device, 302 denotes a position control device, 303 denotes an X-axis drive unit, 304 denotes a Y-axis drive unit, 305 denotes a θ-axis drive unit, 306 denotes an X-axis motor, 307 denotes a Y-axis motor, and 308 denotes a θ-axis motor. It is.

In FIG. 3, the camera 201 captures an image of the pattern surface (front surface) of the wafer 211 and outputs the captured image data to the image processing device 301.
The image processing apparatus 301 analyzes the input image data by well-known image processing such as pattern recognition, and extracts deviations in the X, Y, and θ coordinates using alignment marks at predetermined locations on the wafer and die. The position correction amount is calculated so that the center of the die to be picked up is at the center position of the pickup, and the calculated position correction amount is output to the position control device 302.
The position control device 302 outputs a control signal to the drive units 303 to 305 based on the input position correction amount. The drive units 303 to 305 control the respective motors (X-axis motor 306, Y-axis motor 307, and θ-axis motor 308) based on the input control signal, and the X coordinate, Y coordinate, and θ (rotation) coordinate. Correct.
In the above-described embodiment, the position correction for the pickup device 112 has been described. Hereinafter, the same applies to the preform portion 131 and the bonding head portion 132. The image processing device 301 and the position control device 302 are a set, and control all of the pickup device 112, the preform unit 131, and the bonding head unit 132.

One embodiment of the present invention will be described with reference to FIG. FIG. 4 is a schematic diagram for explaining the operation of the embodiment of the die bonder of the present invention. FIG. 4A is a schematic diagram for explaining the bonding operation of an embodiment of the die bonder of the present invention. FIG.4 (b) is a side view for demonstrating the rotation mechanism of the transfer tool of the die bonder of this invention. FIG. 4C is a view for explaining the rotation trajectory of the transfer tool of one embodiment of the die bonder of the present invention. 401 is a wafer, 402 is a die, 403 is a transfer tool, 404 is a work (substrate or frame), 405 is a camera that images the die 402, 406 is a camera that images the work 404, 407 is picking up the transfer tool 403 A camera for imaging the back surface of the die, 408 is a rotation mechanism, 409 is a rotation center, 410 is the center of the transfer tool (point P ₁ ), 411 is a pulley / belt portion, and 412 is a rotation locus. The rotation mechanism 408 includes, for example, a motor and a pulley / belt portion for transmitting the rotational driving force of the motor to the transfer tool.

First, referring to FIG. 4A, a method for creating a correction table when the center position of the transfer tool 403 varies depending on the rotation angle thereof will be described.
In FIG. 4A, the camera 407 previously images the bottom surface of the transfer tool 403 from the lower side (back side: Z direction) of the transfer tool 403. At this time, imaging is performed while the transfer tool 403 is rotated by the rotation mechanism 408. At this time, the transfer tool 403 does not pick up the die 402.
Then, the rotation center Ot is calculated from the coordinate locus of an arbitrary point on the bottom surface of the transfer tool 403 (see FIG. 4C). At this time, the image processing apparatus 301 outputs a rotation amount command value to the rotation mechanism 408 via the position control device, and the rotation mechanism 408 rotates the transfer tool 403 according to the rotation amount command value (FIGS. 3 and 3). 4 (b).) The rotation mechanism 408 rotates the transfer tool 403 by the minimum resolution unit of the rotation mechanism, or rotates 360 degrees for each predetermined angle. From the rotation amount command value and the position after rotation recognized by the undervision camera 407, a data table for correcting the error of the actual rotation amount (actual rotation amount) at each angle is created. The created data table is stored in the image processing apparatus 301 or the position control apparatus 302.

  FIG. 5 is a diagram showing an example of a data table created in the die bonder and the die bonding method of the present invention. The rotation amount command value is rotated from 0 degree to 359 degrees, and the image picked up by the undervision camera 407 after each rotation operation is subjected to image processing, and the actual rotation amount (Δθ) and X coordinate error (ΔX) And the error (ΔY) of the Y coordinate.

  FIG. 6 is a view for explaining the θ shift of the bottom surface (back surface) of the transfer tool 403 in the die bonder of the present invention. Reference numeral 600 denotes the bottom surface of the transfer tool 403, 601 denotes an ideal bottom image when the rotation amount command value captured by the undervision camera 407 is 0 degrees, and 602 denotes an example of the bottom surface image shifted in the θ direction. Reference numeral 603 denotes an example of an image of the bottom surface shifted in the X direction. Since the transfer tool 403 is a tool that is exchanged depending on the size of the die, every time it is exchanged, deviation occurs in the θ direction, the X direction, and the Y direction.

FIG. 7 is a flowchart for explaining an embodiment of the database creation process of the rotation center of the transfer tool of the die bonder and die bonding method of the present invention.
This processing operation is controlled by the image processing apparatus (see FIG. 3).
In FIG. 7, in step S701, the rotation center Ot (Xt, Yt) of the transfer tool is calculated (see FIGS. 4 to 6).
In step S702, the actual rotation amount when the rotation amount command value is 0 degree is calculated from the image of the bottom surface of the transfer tool acquired from the camera and registered in the data table.
In step S703, the transfer tool is rotated by k degrees (k degrees is the minimum resolution of the rotation mechanism, for example).
In step S704, the actual rotation amount at the rotation amount command value k degrees is calculated from the image of the bottom surface of the transfer tool acquired from the camera and registered in the data table.
In step S705, it is determined whether all rotation amount data for 360 degrees have been registered in the database. If all the rotation amount data has been registered, this process ends. If not, the process returns to step S703.

Next, a procedure in which the transfer tool 403 picks up the die 402 from the wafer 401 and mounts it on the workpiece 404 will be briefly described with reference to FIG.
The camera 405 images the surface of the die 402 to be picked up on the wafer 401 and outputs the captured image to the image processing apparatus 301. The image processing apparatus 301 calculates the center position (Xd, Yd, θd) of the die 402 by performing image processing on the captured image of the die 402.
Further, the image processing apparatus 301 aligns the rotation center (Xp, Yp, θp) of the transfer tool 403 calculated in advance with the calculated center position of the die 402. At this time, θ correction is performed based on a previously calculated θ rotation data table, and the die 402 to be picked up is picked up from the wafer 401.
As described above, the transfer tool 403 moves onto the wafer 401 (point P ₀ ) and picks up the die 402 based on the image captured by the camera 405. After the pickup, transfer tool 403 is moved to the point _{P 2.}

At point P ₂ , the camera 406 captures a predetermined die bonding position of the workpiece 404 and outputs the captured image to the image processing apparatus 301. The image processing apparatus 301 calculates the center position of the workpiece 404 by performing image processing on the captured image of the workpiece 404.
Furthermore, the image processing apparatus 301 aligns the rotation center (Xp, Yp, θp) of the transfer tool 403 calculated in advance with the calculated center position of the workpiece 404. At this time, θ correction is performed based on a previously calculated θ rotation data table, and the die 402 to be picked up is picked up from the wafer 401.

As described above, die bonding is performed in advance so as to correct the displacement of the center position of the transfer tool 403 in the rotational direction. That is, the surface of the die 402 of the wafer 401 is imaged by the camera 405, and the center position Od (Xd, Yd, Zd) of the die 402 is calculated from the image recognition process on the surface of the die 402. Then, the rotation center Ot (Xp, Yp, Zp) calculated in advance is matched with the center position Od of the die. At that time, θ correction is performed based on a previously calculated θ rotation command-actual rotation correction data table, and a die is picked up from the wafer.
Thereafter, the substrate 406 is recognized by the camera 406 and the center of the mounting position is calculated, and the rotation center (Xp, Yp, θp) of the transfer tool 403 and the center of the mounting position (Xm, Ym, θm) are calculated. In addition, the die picked up from the wafer is mounted on the workpiece 404.

FIG. 4B is a view for explaining the rotation mechanism of the transfer tool 403. FIG. 4C is a diagram illustrating an example of the rotation locus of the transfer tool 403 captured by the camera 407.
Incidentally, FIG. 4 (b) is a diagram rotational center axis 409 of FIG. 4 transported to the position of the point _{P 1} of (a) tool 403 and transport tools 403 is stopped moving. At this time, the camera 407 is provided at a position where the transfer tool 403 can be imaged from below.
As described above, first, the rotation center Ot of the transfer tool 403 is calculated from the rotation trajectory of the transfer tool 403, and is rotated around the calculated rotation center Ot in the minimum resolution unit or at a predetermined angle. It is possible to create a data table for correcting the error of the actual rotation amount at each angle from the rotation amount command value and the position after rotation recognized by the camera 407 by rotating 360 degrees each time.

FIG. 8 is a cross-sectional view showing a part of a transfer tool used in the die bonder and the die bonding method of the present invention. Reference numeral 800 denotes a transfer tool, reference numeral 801 denotes a fixing part of the transfer tool 800, reference numeral 802 denotes an exchange part of the transfer tool 800 that is exchanged according to the size of the die, reference numeral 803 denotes a bottom part of the transfer tool, and reference numeral 804 denotes a fixing part 801 and an exchange part 802. It is a fixing tool.
As shown in an example in FIG. 8, since there is always a mechanical gap between the fixing portion 801 and the replacement portion 802, when fixed with the fixture 804, the centers of the replacement portion 802 and the bottom surface portion 803 are Does not match the center of rotation.
In the above embodiment of the present invention, the suction mechanism for sucking the die is complicated, and is not shown in the transfer tool.

In FIG. 4A, the transfer tool 403 and the rotation center axis 409 of the transfer tool 403 are moved to the position of the point P ₁ , and the image is picked up by the camera 405 from the upper side of the transfer tool 403 and transferred by the rotation mechanism 408. The tool 403 is rotated, and the center of rotation is calculated from the locus of the coordinates of an arbitrary point on the transfer tool 403. Further, the transfer tool 403 is rotated 360 degrees in the minimum resolution unit of the rotation mechanism 408, and a data table for correcting the error of the actual rotation amount calculated from the rotation amount command value and the position after rotation viewed with the camera 407 is created. To do. The difference from the first embodiment is that the camera 407 is provided so as to image the transfer tool 403 from the upper side, and the rotation center of the transfer tool is calculated from the locus of an arbitrary point on the outer shape of the bottom surface of the transfer tool 403. is there. Hereinafter, it is the same as that of Example 1.

In order to achieve the above object, the die bonder and the die bonding method of the present invention can accurately determine the rotation center of the rotation mechanism of the transfer tool with a camera and accurately determine the trajectory of any point during rotation. It is equipped with a function that can accurately correct the rotation of the workpiece by accurately aligning the rotation center of the transfer tool and the center of the workpiece.
Also, by measuring the trajectory during rotation of the transfer tool with a camera, a position correction data table for rotation for correcting the linearity of the rotation mechanism of the transfer tool is created, and the function for accurately correcting the rotation of the workpiece is provided. Prepared.
Furthermore, the camera has a function of inspecting the back surface of the die picked up from the wafer and the state of the transfer tool with a camera.

In the future semiconductors, especially memories, package shrinkage has progressed from two dimensions to three dimensions (height and thickness direction), and the process of stacking dies while reducing the thickness of the dies has become the mainstream. Yes. In order to perform such lamination, a highly accurate mounting technique is required. In particular, a technique for increasing the correction accuracy of the θ component in the positioning accuracy is indispensable. According to the above embodiment, it is possible to increase the correction accuracy of the θ component in the positioning accuracy.
Furthermore, according to the above embodiment, the work of picking up the die from the wafer, imaging the back surface of the die with the undervision camera, and correcting the rotational position by image processing can be omitted, and the die can be mounted on the workpiece. A die bonder and a die bonding method with high productivity and high reliability can be provided.

  11: Wafer supply unit, 12: Workpiece supply / conveyance unit, 13: Die bonding unit, 100: Die bonder, 111: Wafer cassette lifter, 112: Pickup device, 121: Stack loader, 122: Frame feeder, 123: Unloader, 131 : Preform part, 132: Bonding head part, 201-203: Camera, 211 :: Wafer, 212, 213: Workpiece, 232: Processing position of preform part, 233: Processing position of die bonding part, 251: Pitch, 301: Image processing device 302: Position control device 303: X-axis drive unit 304: Y-axis drive unit 305: θ-axis drive unit 306: X-axis motor 307: Y-axis motor 308: θ-axis motor 401: Wafer 402: Die 403: Transfer Lumpur, 404: workpiece 405 to 407: Camera 408: rotating mechanism 409: the rotational center axis, 410: center of the transfer tool, 411: pulley belt unit, 412: rotation locus.

Claims (5)

A transfer tool for taking a semiconductor chip and mounting it on a workpiece;
A rotating mechanism for rotating the transfer tool;
A camera for imaging the bottom surface of the transfer tool;
Rotating the transfer tool to a predetermined rotation angle by the rotation mechanism, imaging the bottom surface of the transfer tool by the camera at each rotation angle, calculating the rotation center of the transfer tool from the captured image; and An image processing apparatus for registering a θ shift amount for each rotation angle in a database;
A position control device that corrects the position of the transfer tool based on the database each time the semiconductor chip is mounted on the workpiece;
A die bonder characterized by comprising:   The die bonder according to claim 1, wherein the θ shift amount registered in the database is a shift amount in the X direction, the Y direction, and the θ direction for each rotation angle.   3. The die bonder according to claim 1, wherein the image processing device is configured to transfer the transfer from a rotation trajectory about an arbitrary point of the bottom image of the transfer tool captured by the camera at each rotation angle. A die bonder characterized by calculating the center of rotation of the tool.   The transfer tool is rotated at a predetermined rotation angle, the bottom surface of the transfer tool is imaged by the camera at each rotation angle, the rotation center of the transfer tool is calculated from the captured image, and θ for each rotation angle A die bonding method comprising: registering a deviation amount in a database and correcting the position of the transfer tool based on the database each time a semiconductor chip is mounted on a workpiece.   5. The die bonding method according to claim 4, wherein a rotation center of the transfer tool is calculated from a rotation locus of an arbitrary point of the image of the bottom surface of the transfer tool imaged by the camera for each rotation angle. A die bonding method characterized by the above.

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