JP2016171107A - Bonding device and bonding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die bonder and a bonding method of high positioning accuracy at a mounting position, by correcting the posture deviation between a pickup imaging camera and a mounting imaging camera.SOLUTION: A die is suction held by a bonding head, having a reference mark at a position offset from the center position of a collet for suction holding the die, and bonded to a mounting position. The reference mark is images by the imaging means at the suction holding position and the mounting position, respectively. Based on the respective imaging results, positional deviation and rotation angle deviation of each imaging means from the bonding head are detected. Based on the respective detection results, at least the third rotation angle deviation, out of the third positional deviation and third rotation angle deviation of the bonding head from the mounting position, is corrected.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a bonding apparatus and a bonding method, and more particularly to a bonding apparatus and a bonding method capable of improving positioning accuracy at a mounting position where a die is bonded.

The die is adsorbed from the wafer as part of the process of mounting the die (semiconductor chip) on a substrate such as a wiring board or lead frame to assemble the package. There is a bonding process in which the substrate is mounted directly on a substrate or once on an intermediate stage and mounted by a bonding head.
There is cited document 1 as such a bonding apparatus. In Cited Document 1, in order to prevent a decrease in positioning accuracy due to the weight of the bonding head, the rotation axis of the bonding head that brings about weight is not provided in the bonding head, and the position (angle) deviation in the rotation direction of the substrate on the bonding stage is shifted. Discloses a technique for correcting by rotating a pellet (die) on a precise stage (intermediate stage).

JP 2000-252303 A

  On the other hand, due to the recent development of chip-on-chip stacking technology due to smaller and thinner packages and thinner die, die bonding has become more demanding for single-digit order μm positioning.

  Therefore, sufficient positioning accuracy cannot be obtained simply by correcting the rotational deviation of the substrate on the bonding stage as in the cited document 1, and when the die is picked up, the die posture defined by the position and the rotation angle is imaged. When bonding the die to the pickup imaging camera and the die, it has become a problem that the positional deviation with respect to the bonding head between the mounting imaging camera for imaging the mounting position affects the positioning accuracy of the die at the mounting position.

  The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide a bonding apparatus and a bonding method with high positioning accuracy at a mounting position by correcting a positional deviation between a pickup imaging camera and a mounting imaging camera.

In order to achieve the above object, the present invention provides a pickup imaging means having a first imaging field of view,
A mounting position imaging means having a second imaging visual field capable of imaging the mounting position of the die;
A die transfer tool capable of picking up a die in a first imaging field of view and placing the die at a placement position in a second imaging field of view, and picking up the die within the first imaging field of view. A die transfer tool having a reference mark at a position that can be imaged within the second imaging field when the die is placed at the placement position;
A first detection unit capable of detecting a reference mark within the first imaging field; a second detection unit capable of detecting the reference mark within the second imaging field; a first detection unit; and a second detection unit. It is a bonding apparatus having a correcting means capable of correcting the mounting position of the die held by the die transfer tool based on the result.

  Here, the die transfer tool includes, in addition to a bonding head for bonding the die, a pickup head for picking up from the wafer, a head that moves between the intermediate stage and some other place.

Further, the pickup imaging means includes an imaging means for picking up a die from a wafer, an imaging means for picking up a die placed on an intermediate stage, and an imaging means for picking up a die from a holding tool for another die. In short, it includes an image pickup means that can pick up an image when picking up a die. In addition, the mounting position imaging unit is an imaging unit that takes an image when the die is placed on a target portion to be transferred, such as an imaging unit when the die is placed on an intermediate stage, an imaging unit when the die is placed on a substrate, Including means.
In addition to placing the die at the target location, placing the die includes any bonding action such as provisional pressure bonding or main pressure bonding.

  Further, the correction means is not limited to correction using only the die transfer tool, and any correction means capable of correcting the mounting position of the die held by the die transfer tool may be used. The die placement location may be corrected by correcting the position / angle of the die transfer tool, or the die placement location may be corrected by correcting the position / angle of the intermediate stage. In addition, any correction means that can correct the mounting position of the die can be used.

Further, according to the present invention, when the first detection means or the second detection means is moved in a plane in a moving direction in which the transfer tool moves from the pick-up position of the die to the mounting position of the die or in a direction perpendicular to the moving direction. It may be possible to detect the trajectory of the reference mark obtained.
Further, in the present invention, the reference mark may be a reference mark that can be imaged by the pickup imaging means or the mounting position imaging means via an optical system having two prisms provided on the transfer tool.

In the present invention, the correcting means may be able to correct by rotating an intermediate stage that is rotatable in a plane parallel to the mounting surface related to the mounting position.
Furthermore, the present invention may include pickup means that can invert the die and can rotate in a plane parallel to the placement surface having the placement position, and the correction means may rotate the pickup means.

The present invention also includes a first detection step of detecting a reference mark provided on the die transfer tool imaged by the pickup imaging means;
A second detection step of detecting a reference mark imaged by the mounting position imaging means;
A bonding method including a step of correcting a placement position of a die held by a die transfer tool based on detection results of a first detection step and a second detection step.

Further, according to the present invention, in the first detection step or the second detection step, the plane is moved in the moving direction in which the die transfer tool moves from the pick-up position of the die to the mounting position of the die or in a direction perpendicular to the moving direction. It may be a step of detecting based on the trajectory of the reference mark obtained at that time.
In the present invention, the first or second detection step may be a step in which the reference mark is imaged through an optical system having two prisms provided in the transfer tool.

Further, according to the present invention, the correction step is a step of correcting by rotating an intermediate stage that is rotatable in a plane parallel to the placement surface based on the results obtained in the first detection step and the first detection step. There may be.
In the present invention, the correction step may be a step of correcting by rotating the pick-up means that can be rotated in a plane parallel to the mounting surface having the mounting position by inverting the die.

  According to the present invention, it is possible to provide a bonding apparatus and a bonding method with high positioning accuracy at a mounting position by correcting a positional deviation between the pickup imaging camera and the mounting imaging camera.

It is a schematic side view of the principal part of the 1st Example of the die bonder suitable for this invention. It is the schematic which shows one Example of the pick-up head which picks up die | dye from a wafer. It is a figure which shows typically the structure of the bonding head in a 1st Example. Fig. 3 shows a detection processing flow of an imaging camera posture shift. (a) is a figure which shows the detection result of the attitude | position deviation of a mounted imaging camera, (b) is a figure which shows the detection result of the bonding head attitude | position deviation of an intermediate | middle stage imaging camera. (a) shows the figure when the mounting position of the new die D is imaged by the mounting imaging camera on the substrate P or the already mounted die by the broken line conveyed to the attach stage, and (b) is placed on the intermediate stage. It is a figure when the image | photographed die D is imaged with the intermediate stage imaging camera. It is a schematic side view of the principal part of the 2nd Example of the die bonder suitable for this invention. It is a figure explaining the difference between this invention and a prior art.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, the following description is for describing one embodiment of the present invention, and does not limit the scope of the present invention. Accordingly, those skilled in the art can employ embodiments in which these elements or all of the elements are replaced with equivalent ones, and these embodiments are also included in the scope of the present invention.
In this description, components having common functions are denoted by the same reference numerals in the description of each drawing, and overlapping description is avoided as much as possible.

  FIG. 1 is a schematic side view of a main part of a first embodiment of a die bonder which is a bonding apparatus suitable for the present invention. The die bonder 100 once places the die D picked up by the pickup head 13 on the intermediate stage (holding position) 22, picks up the placed die D again with the bonding head 23, bonds it to the mounting position, and attaches it to the substrate P. It is a device to be mounted.

  The die bonder 100 includes a supply stage imaging camera 11 that recognizes the attitude of the die D on the wafer, an intermediate stage imaging camera 21 that recognizes the attitude of the die D placed on the intermediate stage 22, and a mounting position on the attachment stage 32. And a mounted imaging camera 31 that recognizes.

  In the present invention, it is the intermediate stage imaging camera 21 involved in the pickup by the bonding head 23 and the mounting imaging camera involved in the bonding to the mounting position by the bonding head 23 that needs to correct the posture deviation between the imaging cameras. In this embodiment, the intermediate stage imaging camera 21 is a pickup imaging camera in the present invention.

  The die bonder 100 includes a turning drive device 25 provided on the intermediate stage 22, an undervision camera 41 provided between the intermediate stage 22 and the attach stage 32, a heating device 34 provided on the attach stage 32, And a control device 50.

  The turning drive device 25 turns the intermediate stage 22 in a plane parallel to the mounting surface having the mounting position, and corrects a rotational angle shift or the like between the intermediate stage imaging camera 21 and the mounting imaging camera.

  The under vision camera 41 observes the state of the die D adsorbed while the bonding head 23 is moving from directly below, and the heating device 34 heats the stage 32 in order to mount the die D.

  A control device 50, a CPU (Central processor unit) (not shown), a ROM (Read only memory) for storing a control program, a RAM (Random access memory) for storing data, a control bus, etc., control each element constituting the die bonder 100. Then, implementation control described below is performed.

  In the present invention, a reference mark is provided on the bonding head 23 to correct a positional deviation between the pickup imaging camera 21 and the mounting imaging camera 31.

  Further, in this embodiment, the intermediate stage 22 is turned to correct the rotational angle deviation between the two imaging cameras. Hereinafter, in this embodiment, the two imaging cameras refer to the intermediate stage imaging camera 21 and the mounting imaging camera 31 that are pickup imaging cameras.

  FIG. 2A is a diagram schematically showing the structure of the bonding head 23 in this embodiment. The bonding head 23 includes a collet 23C that sucks and holds the die D, a main body 23H that moves the collet 23C up and down and moves it on a two-dimensional plane parallel to the mounting surface, and an imaging camera posture deviation detection unit 23K having a reference mark M. Have The bonding head 23 does not have a turning axis for turning the collet in a plane parallel to the mounting surface.

  The imaging camera attitude deviation detection unit 23K extends from the main body 23H, and passes through the mark portion 23m provided with the reference mark M and the image of the reference mark M through the center position 23cp of the collet 23C and perpendicular to the mounting surface It has an optical system 23o leading onto 23j. The center position 23cp shown in FIG. 2A is shown for convenience on the side parallel to the paper surface.

  In this embodiment, the optical system 23o has two prisms 23p1 and 23p2 provided on the upper portion of the main body 23H, and an optical system support 23s that supports them on the main body 23H. The prism 23p2 has an optical axis. It is provided so as to coincide with the central axis 23j. As another example of the optical system, a fiberscope provided so that one end faces the reference mark M and the other end faces the imaging surface of the imaging camera at the position of the prism 23p2.

  The reference mark M is provided at a position offset from the center position 23cp of the collet 23C in the imaging field of view of both imaging cameras. Further, the distance L from the imaging surface of both imaging cameras to the reference mark M is a distance that becomes a position corresponding to the focal length WD of the imaging camera shown in FIG. 2B, that is, L1 + L2 + L3.

  FIG. 3A shows a view of the reference mark M shown in FIG. Other reference mark M shapes may be triangular notches as shown in FIG. 3B, and the mark 23m may be rod-shaped. In short, the reference mark M only needs to have a shape that can be contrasted with the mark portion 23m and can be discriminated by the resolution of the imaging camera in order to increase the positioning accuracy at the mounting position.

  Further, the reference mark may have a linear shape as shown in FIG. If it is linear, there is an advantage that it is not necessary to move the mark reference M in order to detect a deviation in posture. When the size of the die D is small, the field of view of the imaging camera is reduced to further increase the resolution, and the linear length may not be increased.

  Prior to describing a method of detecting the attitude deviation of both imaging cameras, the prior art described in the present invention and Patent Document 1 will be described with reference to FIG. FIG. 8 (a) is a diagram schematically showing the processing flow of the present invention, and FIG. 8 (b) is a diagram schematically showing the processing flow of the prior art.

In the prior art, the postures of the substrate and the die are simply imaged by the respective imaging cameras, and the posture deviation defined by the position (X, Y) of the substrate and the die and the rotation angle θ is corrected. On the other hand, in addition to correcting the posture deviation between the substrate and the die, the present invention further includes a pickup imaging camera that images the posture of the die as described in the problem and a mounting imaging camera that images the mounting position (substrate or the like). Next, an example of the mounting imaging camera 31 will be described with reference to a method for detecting the attitude deviation of the imaging camera using the reference mark M with reference to FIG. 2, FIG. This will be described with reference to FIG. FIG. 4 is a diagram illustrating a detection processing flow of the posture deviation of the imaging camera. FIG. 5A is a diagram illustrating a detection result of the attitude shift of the mounted imaging camera 31 obtained by the processing. In the description, as shown in FIG. 1, the direction in which the bonding head 23 moves between the intermediate stage 22 and the attach stage 32 is defined as the Y direction, and the direction orthogonal to the Y direction is parallel to the mounting surface 32m. X direction.

  First, the bonding head 23 is moved in the Y direction and moved to the vicinity of the center position of the imaging field of the mounting imaging camera 31 to obtain the imaging M1 of the reference mark M (S1). Thereafter, the bonding head 23 is moved by a predetermined distance parallel to the X direction, and an image M2 of the reference mark M at that time is obtained (S2). As shown in FIG. 5A, although the reference mark M is moved in parallel to the X direction, the mounting imaging camera 31 is connected to the bonding head 23 by connecting M1 and M2 and inclining the straight line. In other words, a rotation angle deviation Δθba is obtained (S3). Since M1 is on the center position 23cp of the collet 23C, the deviation between M1 and the center position 31c of the imaging field of the mounting imaging camera 31 becomes the positional deviation with respect to the bonding head 31 of the mounting imaging camera 31, and the positional deviation (ΔXba, ΔYba) is obtained (S4).

  Steps S1 to S4 shown in FIG. 4 are also performed on the intermediate stage imaging camera 21 to obtain a rotational angle deviation Δθbc and positional deviation (ΔXbc, ΔYbc) of the intermediate stage imaging camera 21 shown in FIG. . For example, Δθba and Δθba are positive in the clockwise direction, and other rotational angle deviations are the same. Note that 21 c is the center position of the imaging field of view of the intermediate stage imaging camera 21.

As a result, the attitude deviation with respect to the bonding head 23 with respect to the mounting position on the attachment stage 32 due to the attitude deviation between the two imaging cameras 21 and 31 (the both imaging camera attitude deviations) is expressed by equations (1) and (2).
Rotational angle deviation Δθb: Δθba−Δθbc (1)
Position deviation (ΔXb, ΔYb): (ΔXba−ΔXbc, ΔYba−ΔYbc) (2)
When the posture deviations of both imaging cameras change every moment, they are detected each time. When the posture deviations can be maintained for a certain time, they are detected every certain time. In either case, the rotation angle deviation correction is performed by rotating the intermediate stage 22. As a result of the rotation, the die D is recognized again, and after having entered a certain range, is picked up and picked up by the collet 23C, then moved to the mounting position and bonded.

  On the other hand, the positional deviation correction is performed by moving the bonding head in the X and Y directions. The position to be corrected is a position shift by the intermediate stage imaging camera 21 before and after the pickup from the intermediate stage, and a shift correction by the mounting imaging camera 31 may be performed at the time of mounting or by both imaging cameras described later. The total displacement may be performed at the mounting position.

In the embodiment described above, the bonding head 23 is moved to the vicinity of the center position of the imaging field of view of the mounting imaging camera 31 and the intermediate stage camera. By translating from the mounting position to the Y position, which is the center position of the imaging camera 21, the positional deviation in the Y direction is eliminated, and the positional deviation ΔXb in the X direction is also ΔXbc. That is, equation (2 ′) is obtained.
Misalignment (ΔXb, ΔYb): (−ΔXbc, 0) (2 ′)
As a result, the positional deviation correction including the following positional deviation correction becomes easy.

  In the embodiment described above, the rotational angle deviation between the pickup (intermediate stage) imaging camera and the mounting imaging camera that images the mounting position of the die is corrected by the rotation of the intermediate stage. May be.

  According to the present embodiment described above, the bonding head having the reference mark is used to detect and correct the positional deviation with respect to the bonding head between the pickup (intermediate stage) imaging camera and the mounting imaging camera that images the mounting position of the die. Thus, the mounting position can be accurately determined.

  Further, according to the present embodiment described above, by rotating the intermediate stage, it is possible to correct the rotational angle deviation of the two imaging camera attitude deviations without providing a rotation axis in the bonding head.

In the case of positioning with higher accuracy, correction is performed by taking into account the processing attitude deviation described below.
The processing posture deviation is a posture deviation of the substrate P transported to the attach stage 32 or the already mounted die D with respect to the mounting imaging camera 31, and an intermediate stage imaging camera of the die D placed on the intermediate stage 21. The posture deviation with respect to 21 is collectively referred to. Hereinafter, the processing posture deviation will be described with reference to FIG.

  FIG. 6A shows a diagram when the mounting imaging camera 31 images the mounting position of a new die D on the substrate P or the already mounted die D indicated by the broken line that has been transported to the attach stage 32. As shown in FIG. 6A, the positional deviation of the mounting position with respect to the mounting imaging camera 31 is Δθad as the rotation angle deviation and (ΔXad, ΔYad) as the positional deviation. Similarly, FIG. 6B is a diagram showing the posture deviation with respect to the intermediate stage imaging camera 21 by imaging the die D placed on the intermediate stage 21, and the rotation angle deviation is Δθcd and the positional deviation is (ΔXcd, ΔYcd).

From FIG. 6, the processing attitude deviation with respect to the mounting position due to the attitude deviation between the mounting position on the attach stage 32 and the die D on the intermediate stage 21 is expressed by Equations (3) and (4).
Rotational angle deviation Δθd: Δθad−Δθcd (3)
Misalignment (ΔXd, ΔYd): (ΔXad−ΔXcd, ΔYad−ΔYcd) (4)
The total orientation deviation with respect to the mounting position of the bonding head 23 when both the imaging camera orientation deviation and the processing orientation deviation are performed at the same time are the both imaging camera orientation deviations shown in Equations (1) and (2), and (3) and Equations (4). (5) and (6) are obtained by combining the processing posture deviations shown in FIG.
Total rotation angle deviation Δθ: Δθb + Δθd (5)
Total displacement (ΔX, ΔY): (ΔXb + ΔXd, ΔYa + ΔYd) (6)
Accordingly, when only one die D is bonded to the substrate P in FIG. 1, the intermediate stage 22 is turned based on the formula (3) or the formula (5) to correct the rotational angle deviation, and the formula (6) Based on the above, the positional deviation is corrected by the bonding head, and then the die D is picked up from the intermediate stage 22 and bonded to the mounting position. The correction of the positional deviation based on Expression (6) may be performed at the mounting position without being performed at the intermediate stage 22.

  Further, when a plurality of dies D are stacked on the substrate P in FIG. 1, the posture deviation of the stacked dies D can be obtained as a posture deviation obtained by shifting the posture deviation of the substrate P obtained first.

  Further, according to the present embodiment described above, by detecting the attitude deviation of the die placed on the intermediate stage with respect to the intermediate stage imaging camera and the attitude deviation of the attachment stage mounting position with respect to the mounting imaging camera, Since the attitude deviation with respect to the mounting position can be corrected in association with the attitude deviations of both imaging cameras, the die can be positioned more accurately at the mounting position.

  Next, a second embodiment of a die bonder suitable for the present invention will be described with reference to FIG. Unlike the first embodiment, the die bonder 200 of the second embodiment has no intermediate stage 22, and the bonding head 23 picks up the die D directly from the wafer (holding position) W, and the mounting position of the attach table 32 is obtained. This is a device for bonding directly to the mounting position.

  In the second embodiment, the supply stage imaging camera 11 that confirms the posture of the die D on the wafer W on the supply stage 12 is a pickup imaging camera. For example, the posture deviation between the supply stage imaging camera 11 and the mounting imaging camera 31 is detected by the method shown in the first embodiment by the bonding head 23 having the reference mark M shown in FIG. By correcting the posture deviation, the positioning accuracy at the mounting position can be improved. In the present embodiment, a rotation axis of the bonding head 23 is provided, and correction of the rotation angle deviation is performed by the rotation axis together with the position deviation correction.

Also in the second embodiment, as in the first embodiment, by providing the reference mark M on the bonding head 23, it is possible to correct the positional deviation between the pickup imaging camera and the mounting imaging camera, and to increase the positioning accuracy at the mounting position. Can
The present invention is applicable if the bonding head shown in the first and second embodiments is a die bonder that picks up a die and bonds it to a mounting position. For example, the present invention can be applied to delivery of a die of a flip chip bonder that is a bonding apparatus. The flip chip bonder has a pickup head 13 that picks up the die D from the wafer W, inverts it for delivery, and can rotate in a plane parallel to the mounting surface having the mounting position. The die D is sucked and held at the position (holding position) where the die D is reversed at 13 and bonded to the mounting position. The reference mark M is imaged at the reversed position and the mounting position, and the positional deviation and the rotational angle deviation with respect to the mounting position of the bonding head 23 are detected from the imaging results. For example, the rotational deviation is detected by the pickup head 13. Correction can be performed by the bonding head 23. In the case of this example, the pickup head that reverses the die D corresponds to the intermediate stage of the first embodiment.

11: Supply stage imaging camera 12: Supply stage 13: Pickup head 21: Intermediate stage imaging camera 21c: Center position of imaging field of intermediate stage imaging camera 22: Intermediate stage 23: Bonding head 23C: Collet 23cp: Collet center position 23j : Collet central axis 23m: Mark part 23o; Optical system 23p1, 23p2: Prism 23s: Optical system support part 23K: Imaging camera attitude deviation detection part 23H: Bonding head body 25: Rotation drive device 31: Mounting imaging camera 31c: Mounting Center position of imaging field of imaging camera 32: Attach stage 34: Heating device 41: Under vision camera 100, 200: Die bonder D: Die (semiconductor chip)
P: Substrate M, M1, M2, Mα, Mβ: Reference mark W: Wafer Δθba: Rotation angle deviation with respect to bonding head of mounting imaging camera Δθbc: Rotation angle deviation with respect to bonding head of intermediate stage imaging camera

Claims (10)

A pickup imaging means having a first imaging field;
A mounting position imaging means having a second imaging visual field capable of imaging the mounting position of the die;
A die transfer tool capable of picking up a die in the first imaging visual field and placing the die at a placement position in the second imaging visual field, wherein the first imaging is performed when the die is picked up. A die transfer tool having a reference mark at a position that can be imaged within the field of view and can be imaged within the second imaging field of view when the die is placed at the placement position;
A first detection unit capable of detecting the reference mark within the first imaging field; a second detection unit capable of detecting the reference mark within the second imaging field; the first detection unit; A bonding apparatus having correction means capable of correcting a placement position of a die held by the die transfer tool based on a result of a second detection means.   The first detecting means or the second detecting means is obtained when the transfer tool is moved in a plane in a moving direction in which the transfer tool moves from a die pickup position to a die mounting position or in a direction perpendicular to the moving direction. The bonding apparatus according to claim 1, wherein a locus of the reference mark to be detected can be detected.   The bonding apparatus according to claim 1 or 2, wherein the reference mark is a reference mark that can be imaged by the pickup imaging means or the mounting position imaging means via an optical system having two prisms provided on the transfer tool.   4. The bonding apparatus according to claim 1, wherein the correction unit can correct the rotation by rotating an intermediate stage that is rotatable in a plane parallel to the mounting surface related to the mounting position. The pick-up means capable of reversing the die and rotatable in a plane parallel to the mounting surface having the mounting position described above,
The bonding apparatus according to claim 1, wherein the correction unit performs correction by rotating the pickup unit. A first detection step of detecting a reference mark provided on the die transfer tool imaged by the pickup imaging means;
A second detection step of detecting the reference mark imaged by the mounting position imaging means;
A bonding method including a step of correcting a placement position of a die held by the die transfer tool based on detection results of the first detection step and the second detection step.   The first detection step or the second detection step is performed when the die transfer tool is moved in a plane in a moving direction in which the die transfer tool moves from a die pickup position to a die mounting position or in a direction perpendicular to the moving direction. The bonding method according to claim 6, wherein the bonding is a step of detecting based on a trajectory of the obtained reference mark.   The bonding method according to claim 6 or 7, wherein the first or second detection step is a step in which the reference mark is imaged through an optical system having two prisms provided on the transfer tool.   The correction step is a step of correcting by rotating an intermediate stage that is rotatable in a plane parallel to the mounting surface based on the results obtained in the first detection step and the first detection step. Item 9. A bonding method according to any one of Items 6 to 8.   9. The correction step according to claim 6, wherein the correcting step is a step of correcting by rotating the pick-up means that can be rotated in a plane parallel to the mounting surface having the mounting position described above by inverting the die. Bonding method.

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