TWI900040B - Mounting device and method for detecting displacement of bonding head included in the mounting device - Google Patents

Abstract

A mounting device capable of accurately detecting displacement of a bonding head in both the forward and backward directions and the rotational direction. The mounting device includes: a bonding head having a cylindrical side surface; a support member supporting the bonding head; a first actuator for advancing and retracting the bonding head in its axial direction; a second actuator for rotating the bonding head about its axis; a first scale for detecting axial displacement of the bonding head, disposed on the cylindrical side surface; a second scale for detecting axial displacement of the bonding head, disposed on the cylindrical side surface; a first sensor head for reading the first scale and outputting a first detection signal corresponding to the axial displacement of the bonding head; and a second sensor head for reading the second scale and outputting a second detection signal corresponding to the axial displacement of the bonding head, supported by the support member.

Description

Mounting device and method for detecting displacement of bonding head included in the mounting device

The present invention relates to a mounting device and a method for detecting the displacement of a bonding head included in the mounting device.

For example, in mounting devices used in semiconductor chip manufacturing, such as die bonders, it is necessary to control the position of a bonding head, which holds a semiconductor chip at its tip, so that it can be accurately placed on the die pads of a lead frame mounted on a stage. Therefore, technologies have been proposed for accurately measuring the position of the bonding head or the semiconductor chip after it has been held relative to the die pads (e.g., see Patent Document 1).

[Prior Art Literature] [Patent Literature] [Patent Literature 1] Japanese Patent Publication No. 2014-036068

[Problem to be Solved by the Invention] Even if the relative position of a semiconductor chip before placement on a lead frame can be accurately measured, the chip cannot be accurately placed at the target position on the lead frame unless the bonding head that holds the semiconductor chip can be accurately displaced. This is particularly true when the bonding head is directly driven to displace the chip before placement on the lead frame. This requirement also applies to flip-chip bonders that attach a semiconductor chip to a substrate at the target position.

In typical mounting systems, the bond head rotates via a linkage or gear system, resulting in misalignment between the actuator's output shaft and the bond head's rotational axis. Furthermore, the drive mechanism that linearly moves the bond head and the drive mechanism that rotates the bond head are sometimes stacked in layers relative to the bond head. Consequently, when attempting to calculate the bond head's rotational displacement by measuring the actuator's output shaft rotation, accurate values may not be obtained due to accumulated errors caused by play in the power transmission mechanism or the layered structure.

The present invention is made to solve this problem and provides a mounting device that can accurately detect the displacement of the bonding head in the forward and backward directions and the displacement in the rotational direction.

[Means for Solving the Problem] A first embodiment of the present invention comprises a mounting device comprising: a bonding head having a cylindrical side surface; a support member supporting the bonding head so that the bonding head can advance and retract in an axial direction along a central axis of the cylindrical side surface and can rotate about the central axis; a first actuator for advancing and retracting the bonding head in the axial direction; a second actuator having an output shaft that is not aligned with the central axis and for rotating the bonding head about the axis; and a first scale for detecting whether the bonding head is in a position to move. The axial displacement is provided on the side of the cylinder; a second scale is provided on the side of the cylinder for detecting the displacement of the bonding head about the axis; a first sensor head reads the first scale and outputs a first detection signal corresponding to the displacement of the bonding head about the axis; and a second sensor head reads the second scale and outputs a second detection signal corresponding to the displacement of the bonding head about the axis, and is supported by the support member.

In addition, the second aspect of the present invention is a displacement detection method for a bonding head included in a mounting device, which includes: a second output step, using a second actuator having an output shaft that is inconsistent with the center axis, so that the bonding head having a cylindrical side surface is displaced relative to a supporting member supporting the bonding head around the axis of the center axis of the cylindrical side surface, and the second sensor head supported by the supporting member reads A second scale provided on the side of the cylinder outputs a second detection signal corresponding to the displacement of the bonding head about the axis; and a first output step comprises: when the bonding head is displaced axially along the central axis relative to the support member using a first actuator, a first sensor head reads the first scale provided on the side of the cylinder and outputs a first detection signal corresponding to the displacement of the bonding head in the axial direction. [Effects of the Invention]

The present invention can provide a mounting device that can accurately detect the displacement of a bonding head in the forward and backward directions and the displacement in the rotational direction.

The present invention is described below by way of its embodiments, but the invention to which the patent application relates is not limited to the following embodiments. In addition, not all structures described in the embodiments are essential as means for solving the problem.

FIG1 is a perspective view schematically showing the main components of a flip-chip bonder 100 according to the present embodiment. The flip-chip bonder 100 is an example of a mounting device incorporating a position control device, and is a bonding device that mounts a semiconductor chip 310 having electrodes formed on one surface onto electrodes on a substrate 330. The perspective view of the flip-chip bonder 100 shown in FIG1 is a diagram that limits and schematically shows the components associated with position control when directly displacing the bonding head 110, and does not represent all the structures necessary for the flip-chip bonder 100 to function. Furthermore, the mounting device is not limited to a flip-chip bonder, and may also be a die bonder that places and bonds a semiconductor chip to a die pad on a lead frame.

The flip-chip bonder 100 primarily comprises a bonding head 110, a support base 120, a linear motion mechanism 130, a rotation mechanism 140, a support block 150, and a sensor plate 160. The bonding head 110 suctions a semiconductor chip 310 at its tip, places it on a mounting area 320 of a substrate 330 placed on a stage 220, and then bonds the chip 310 after applying pressure and heat. In this embodiment, the bonding head 110 is generally cylindrical, with the central axis _Ac of the cylindrical side surface parallel to the Z axis as shown. Furthermore, in this embodiment, as shown, the Z axis is the vertical direction (height direction), while the X and Y axes are planar directions, defined as mutually orthogonal.

The support base 120 is a supporting member that supports the bonding head 110 via the support block 150. The support base 120 also directly or indirectly supports the linear motion mechanism 130 and the rotation mechanism 140. Furthermore, the support base 120 can be moved as a whole in the upper space above the carrier 220 in the vertical and planar directions, as indicated by the hollow arrows in the figure, by being driven by a support actuator (not shown in FIG. 1 ). By controlling this overall movement, the support base 120 can, for example, move the bonding head 110, which has adsorbed the semiconductor wafer 310 in the wafer supply device, to the upper portion of the mounting area 320, which serves as the loading target. Furthermore, during the overall movement of the support base 120, the bonding head 110 ideally remains stationary relative to the support base 120.

The linear motion mechanism 130 is a fine-motion mechanism for advancing and retracting the bonding head 110 along the axis of the central axis _Ac (the z-direction indicated by the arrow in the figure) within a predetermined micro-distance range (e.g., ±0.5 mm relative to a reference position). The linear motion mechanism 130 includes, for example, a first actuator 131, which is a motor, and a transmission mechanism for transmitting the output of the first actuator 131. The transmission mechanism includes, for example, a gear train including a gear and a pinion.

The rotating mechanism 140 is a micro-rotation mechanism used to rotate the bonding head 110 around the central axis _Ac (in the θ direction indicated by the arrow in the figure) within a predetermined micro-angle range (e.g., ±5 degrees relative to a reference angle). The rotating mechanism 140 includes, for example, a second actuator 141, which is a motor, and a transmission mechanism that transmits the output of the second actuator 141. The transmission mechanism includes, for example, a crank mechanism and a gear train. Furthermore, the first and second actuators 131, 141 can also drive the bonding head 110 axially or axially using a voice coil motor, pneumatic cylinder, hydraulic cylinder, linear motor, or the like, without the transmission mechanism.

The support block 150 is mounted on the support base 120 and serves as a guide member that supports and guides the bonding head 110 so that it can move forward and backward in the axial direction along the central axis _Ac and rotate about the central axis _Ac . The support block 150 may also be formed integrally with the support base 120. The support block 150 has an opening window 151 for exposing a portion of the cylindrical side surface of the bonding head 110 to the outside. The opening window 151 is formed in a shape surrounded by a rectangular frame in FIG. 1 , but it may have any shape as long as the support block 150 maintains its function of supporting and guiding the bonding head 110.

The sensor plate 160 is a plate-shaped component mounted on the support block 150, facing the cylindrical side surface of the bonding head 110 and covering at least a portion of the opening window 151. The sensor plate 160 supports the first sensor head 161 and the second sensor head 162, so that their respective sensing portions face the cylindrical side surface of the bonding head 110. The first sensor head 161 outputs a first detection signal corresponding to the axial displacement (advance/retract) of the bonding head 110. The second sensor head 162 outputs a second detection signal corresponding to the axial displacement (rotational displacement) of the bonding head 110. In Figure 1, the first and second sensor heads 161, 162 are supported by the sensor plate 160 so as to protrude toward the interior of the opening window 151.

By placing the first and second sensor heads 161, 162 on the sensor plate 160 in this manner, the displacement calculation unit (described later) can calculate the axial and circumferential displacements of the bonding head 110 relative to the support base 120. In other words, the first and second sensor heads 161, 162 are essentially supported by the support base 120.

Figure 2 is a system diagram of the flip-chip bonder 100. The control system of the flip-chip bonder 100 primarily includes an arithmetic processing unit 170, a support actuator 121, a first actuator 131, a second actuator 141, a first sensor head 161, and a second sensor head 162. The arithmetic processing unit 170 is a processor (central processing unit (CPU)) that controls the flip-chip bonder 100 and executes programs. The processor can also collaborate with an arithmetic processing chip, such as an application-specific integrated circuit (ASIC) or a graphics processing unit (GPU).

The computational processing unit 170 also serves as a functional computational unit, performing various computations according to the instructions of the position control program. Specifically, the computational processing unit 170 also functions as a displacement calculation unit 171 and a drive control unit 172. The displacement calculation unit 171 receives the first detection signal output by the first sensor head 161 and processes it to calculate the axial displacement (advance/retract) of the bond head 110 relative to the support base 120. Furthermore, the displacement calculation unit 171 receives the second detection signal output by the second sensor head 162 and processes it to calculate the axial displacement (rotational displacement) of the bond head 110 relative to the support base 120. In addition, a position detection signal is received from a position sensor (not shown), and the position detection signal is processed to calculate the three-dimensional coordinates of the reference position of the support base 120.

During fine motion control, the drive control unit 172 determines the target amount of forward or backward movement required for the semiconductor chip 310 to reach the mounting area 320, where the semiconductor chip 310 is to be placed. Furthermore, the drive control unit 172 determines the target amount of rotation required for the semiconductor chip 310 to be placed in the correct position on the mounting area 320. The drive control unit 172 then sequentially compares the target amount of rotation with the amount of displacement around the axis calculated by the displacement calculation unit 171, and sends a drive signal to the second actuator 141, thereby adjusting the semiconductor chip 310 to the target position. Furthermore, the drive control unit 172 sequentially compares the target advance/retract movement amount with the axial displacement amount calculated by the displacement calculation unit 171, and sends a drive signal to the first actuator 131, thereby placing the semiconductor chip 310 at the target position in the mounting area 320. Furthermore, the drive control unit 172 determines the target movement position of the holder base 120 during overall movement control. Then, the drive control unit 172 sequentially compares the target movement position with the three-dimensional coordinates of the holder base 120 calculated by the displacement calculation unit 171, and sends a drive signal to the holder actuator 121, thereby causing the holder base 120 to reach the target movement position.

Next, the displacement detection sensors used in this embodiment and their configuration are described. Figure 3 is a schematic perspective view of the bond head 110 and two sensor heads (first sensor head 161 and second sensor head 162). Furthermore, Figure 3 depicts the two sensor heads as more separated than is practical, and omits the supporting sensor plate 160 to facilitate understanding of their relationship to the scale membrane 113 they face.

The first sensor head 161 pairs with the first scale 113a depicted on the opposing scale film 113, forming a z-axis encoder for detecting the amount of axial displacement (forward and backward) of the center axis _Ac of the bond head 110. The z-axis encoder is a reflective linear encoder that uses a photodiode to receive reflected light from the first sensor head 161 after it is reflected by the first scale 113a. The encoder then outputs a first detection signal corresponding to the axial displacement based on the intensity of the reflected light.

The second sensor head 162 is paired with the second scale 113b depicted on the opposing scale film 113 to form a θ-axis encoder for detecting the amount of displacement around the central axis _Ac of the bond head 110 (in the rotational direction). The θ-axis encoder is a reflective linear encoder that uses a photodiode to receive reflected light from the second sensor head 162 after it is reflected by the second scale 113b. The encoder then outputs a second detection signal corresponding to the axial displacement, based on the intensity of the reflected light. While this reflective linear encoder is used for both the z-axis encoder and the θ-axis encoder in this embodiment, any type of displacement sensor can be used, as long as the scale and sensor head face each other and output a detection signal corresponding to the displacement. For example, a magnetic encoder may be used in which the scale is formed by magnets and the changes in the scale are detected by a magnetic sensor provided in the sensor head.

At least a portion of the side surface of the bonding head 110 is formed by a cylindrical side surface 110a, which is formed by an arc equidistant from the central axis _Ac . The scale film 113 can also be directly attached to the cylindrical side surface 110a, but in this embodiment, it is indirectly attached via the scale block 112 for ease of installation.

The scale block 112 has an outer surface 112a. When mounted on the bond head 110, this outer surface 112a forms an arcuate surface equidistant from the center axis _Ac , effectively forming the cylindrical side surface of the bond head 110. A scale film 113 is attached to this outer surface 112a. Therefore, when the scale block 112 is mounted on the bond head 110, the scale film 113 attached to the outer surface 112a is effectively positioned on the cylindrical side surface of the bond head 110. Specifically, the first sensor head 161 can directly detect the forward and backward displacement of the bond head 110 by reading changes in the first scale 113a, and the second sensor head 162 can directly detect the rotational displacement of the bond head 110 by reading changes in the second scale 113b. Furthermore, even if the bonding head 110 does not have a cylindrical side surface, or even if it has a cylindrical side surface but the scale block 112 is not mounted on the cylindrical side surface, as long as the outer surface 112a of the scale block 112 mounted on the bonding head 110 is an arc surface that is equidistant from the central axis _Ac , which serves as the rotating axis of the bonding head 110, the bonding head 110 actually has a cylindrical side surface, and the scale film 113 can be attached to the outer surface 112a.

In mounting devices, it's difficult to align the output shaft of a rotating actuator (the second actuator 141 in this embodiment) with the center axis of the bonding head to directly rotate the bonding head. In actual designs, as in this embodiment, the bonding head is often rotated by combining an actuator with an output shaft that doesn't align with the bonding head's center axis _Ac and a transmission mechanism that transmits its output. In conventional mounting devices with this configuration, a rotary encoder is used to detect the rotation of the actuator's output shaft, and a conversion formula is used to calculate the bonding head's rotation. However, this method of calculating the bonding head's rotation may not always yield an accurate value due to play in the transmission mechanism or installation errors. Although attempts have been made to fix an actuator to the linear motion mechanism so that its output axis is aligned with the center axis of the bonding head, in such a configuration, the rotational mechanism is stacked on top of the linear motion mechanism, and errors associated with the linear motion mechanism's movements are accumulated, making it impossible to accurately obtain the amount of rotation of the bonding head.

Compared to this prior art, in the flip-chip bonder 100 of this embodiment, the first sensor head 161 and the second sensor head 162 are supported by the support base 120, without a drive mechanism. Furthermore, the first scale 113a and the second scale 113b are actually attached to the cylindrical side surface of the bond head 110. Therefore, both the axial and circumferential displacements of the bond head 110 can be directly detected, and the respective displacements can be obtained with greater accuracy than in prior mounting devices. Furthermore, in this embodiment, the displacement calculation unit 171 calculates the axial displacement and the axial displacement based on the first detection signal and the second detection signal. However, the axial speed and the axial angular velocity of the bonding head 110 can also be calculated by observing the changes in each detection signal in each short period of time.

Figure 4 schematically illustrates the scale film 113. In this embodiment, first and second scales 113a, 113b are depicted adjacently on a single film. First scale 113a is used to detect axial displacement of the bond head 110. Therefore, first line segments of length _L1 , perpendicular to the axial direction (advance/retract), are arranged in a number corresponding to the set resolution and displacement width _W1 in the forward/retract direction. As described above, if ±0.5 mm relative to the reference position, the displacement width _W1 is 1.0 mm.

Second scale 113b is used to detect displacement around the axis of bond head 110. Therefore, second line segments of length _L2 , perpendicular to the axis (rotational direction), are arranged in a number corresponding to the set resolution and displacement width _W2 in the rotational direction. If the radius of curvature of outer surface 112a, to which scale film 113 is attached, is, for example, 8 mm, and the rotation angle is, for example, ±5 degrees relative to the reference angle, as described above, then displacement width _W2 is 2π × 8 × 10/360 mm.

Here, when the first scale 113a and the second scale 113b are arranged adjacent to each other, even if the projection light from the first sensor head 161 is projected onto any location within the displacement width _W1 , the second sensor head 162 must detect the displacement amount when the bond head ₁₁₀ rotates. Similarly, even if the projection light from the second sensor head ₁₆₂ is projected onto any location within _the displacement width _W2 , the first sensor head 161 must detect the displacement amount when the bond head ₁₁₀ moves forward or backward. In this embodiment, to minimize the scale film 113, _L1 = _W2 and _L2 = _W1 . That is, the length _L1 of each of the first line segments is equal to the distance W2 between the two end segments of the second line segments, and the length _L2 of each of the second line segments is equal to the distance _W1 between the two end segments of the first line _segments .

Furthermore, in this embodiment, in order to accurately draw the first and second line segments perpendicular to each other, the first scale 113a and the second scale 113b are arranged side by side on a single membrane. However, the arrangement of the first and second scales 113a, 113b is not limited to this example. The first and second scales 113a, 113b may be attached to the outer surface 112a or the cylindrical side surface 110a with their respective scales aligned relative to each other. Furthermore, if the first and second sensor heads 161, 162 are supported by separate support members, the first and second scales 113a, 113b may be positioned so that they face each other.

Next, the processing procedure of the calculation processing unit when directly displacing the bond head 110 will be described. Figure 5 is a flowchart illustrating this processing procedure. The illustrated flow begins when the bond head 110 is moved to the upper portion of the mounting area 320, serving as the placement target, through overall motion control, and the target amount of forward and backward movement and rotation of the bond head 110 are determined.

In step S101, the drive control unit 172 sends a drive signal to the second actuator 141, rotating the bonding head 110. In step S102, the displacement calculation unit 171 receives the second detection signal output by the second sensor head 162 after reading the second scale 113b. In step S103, the displacement around the axis is calculated based on this second detection signal.

In step S104, the displacement calculation unit 171 determines whether the calculated displacement has reached the determined rotation target. If it is not reached, the process returns to step S101. If it is reached, the drive control unit 172 stops sending the drive signal to the second actuator 141 and proceeds to step S105.

In step S105, the drive control unit 172 sends a drive signal to the first actuator 131, causing the bonding head 110 to move forward or backward. In step S106, the displacement calculation unit 171 receives the first detection signal output by the first sensor head 161 after reading the first scale 113a. In step S107, the displacement calculation unit 171 calculates the axial displacement based on this first detection signal.

In step S108, the displacement calculation unit 171 determines whether the calculated displacement has reached the predetermined target amount of advance or retreat. If it is determined that it has not reached the target amount, the process returns to step S105. If it is determined that it has reached the target amount, the drive control unit 172 stops sending the drive signal to the first actuator 131, completing the process of placing the semiconductor chip 310 on the mounting area 320.

100: Flip-chip bonder 110: Bonding head 110a: Cylindrical side 112: Scale block 112a: Outer surface 113: Scale film 113a: First scale 113b: Second scale 120: Support base 121: Support actuator 130: Linear motion mechanism 131: First actuator 140: Rotation mechanism 141: Second actuator 150: Support block 151: Opening window 160: Sensor plate 161: First sensor head 162: Second sensor head 170: Arithmetic processing unit 171: Displacement calculation unit 172: Drive control unit 220: Carrier 310: Semiconductor chip 320: Mounting area 330: Lead frame (substrate) _Ac : Center axis _L1 : Length _L2 : Length S101, S102, S103, S104, S105, S106, S107, S108: Step W ₁ : Displacement width (interval) W ₂ : Displacement width (interval) X, Y, Z: Axis z: Direction θ: Direction

Figure 1 is a perspective view schematically showing the main components of the flip-chip bonder according to this embodiment. Figure 2 is a system diagram of the flip-chip bonder. Figure 3 is a perspective view schematically showing a bonding head and two sensor heads. Figure 4 is a diagram schematically showing a scale film. Figure 5 is a flow chart illustrating the processing procedure of the arithmetic processing unit when the bonding head is directly displaced.

100: Flip Chip Bonder

110: Joint head

120: Bracket base

130: Linear motion mechanism

131: First actuator

140: Rotating mechanism

141: Second actuator

150: Bracket block

151: Opening Window

160: Sensor board

161: First sensor head

162: Second sensor head

220: Carrier

310: Semiconductor chip

320: Installation area

330:Substrate

A _c : Center axis

X, Y, Z: Axes

z: direction

θ: direction

Claims (5)

A mounting device includes: a bonding head having a cylindrical side surface; a supporting member supporting the bonding head so that the bonding head can move forward and backward in an axial direction along a central axis of the cylindrical side surface and can rotate around the axis of the central axis; a first actuator for moving the bonding head forward and backward in the axial direction; a second actuator having an output shaft that is not aligned with the central axis and for rotating the bonding head around the axis; a first scale for detecting displacement of the bonding head in the axial direction, the first scale being provided on the cylindrical side surface and comprising a plurality of axes along a first direction. A first line segment is formed; a second scale is used to detect the displacement of the bonding head around the axis, and is arranged on the side of the cylinder, the second scale is formed by multiple second line segments along a second direction, and the first direction and the second direction are orthogonal to each other; a first sensor head reads the first scale and outputs a first detection signal corresponding to the displacement of the bonding head in the axial direction; and a second sensor head reads the second scale and outputs a second detection signal corresponding to the displacement of the bonding head around the axis, and is supported by the supporting structure. A mounting device as described in claim 1, wherein the first scale and the second scale are arranged adjacent to each other on the side surface of the cylinder. A mounting device as described in claim 2, wherein the respective lengths of the multiple first line segments are equal to the intervals between the line segments at both ends of the multiple second line segments, and the respective lengths of the multiple second line segments are equal to the intervals between the line segments at both ends of the multiple first line segments. A mounting device as described in claim 2 or 3, wherein the first scale and the second scale are integrally formed and mounted on the side surface of the cylinder. A displacement detection method is a displacement detection method for a bonding head included in an installation device, the displacement detection method comprising: a second output step, in which a second actuator is used to cause the bonding head having a cylindrical side surface to be displaced relative to a support member supporting the bonding head around an axis of the central axis of the cylindrical side surface, a second sensor head supported by the support member reads a second scale set on the cylindrical side surface, and outputs a second detection signal corresponding to the displacement of the bonding head around the axis, the second actuator having a second output signal corresponding to the displacement of the bonding head around the axis, An output shaft with an inconsistent center axis; and a first output step, when using a first actuator to cause the bonding head to be displaced axially along the center axis relative to the supporting member, the first sensor head reads a first scale provided on the side surface of the cylinder and outputs a first detection signal corresponding to the displacement of the bonding head in the axial direction, wherein the first scale is formed by a plurality of first line segments along a first direction, and the second scale is formed by a plurality of second line segments along a second direction, and the first direction and the second direction are orthogonal to each other.