EP2322021A1

EP2322021A1 - Pick-and-place machine

Info

Publication number: EP2322021A1
Application number: EP09788291A
Authority: EP
Inventors: Raymond Jacobus Wilhelmus Knaapen; Erwin John Van Zwet; Adrianus Johannes Petrus Maria Vermeer; Sander Christiaan Broers; Clemens Maria Bernardus Van Der Zon; Pieter Willem Herman De Jager
Original assignee: Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
Current assignee: Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
Priority date: 2008-09-01
Filing date: 2009-08-27
Publication date: 2011-05-18
Also published as: WO2010024675A1; JP2012501538A

Abstract

A pick-and-place machine, comprising a frame including a shaft; a turret comprising a plurality of pick/place heads, and an inertial balance wheel, both being mounted for rotation about the axis of the shaft; a first electromechanical device for rotating the turret during pick-and-place operation and comprising a magnetic field-generating part and an electrical current-carrying, one part being on the turret and one part being on the inertial balance wheel, wherein the machine is constructed such that torque developed by the first electromechanical device causes angular acceleration of the turret in one direction and angular acceleration of the inertial balance wheel in the opposite direction.

Description

Pick-And-Place Machine

The present invention relates to a pick-and-place machine having particular, but not exclusive, application to three dimensional integrated circuits (3D ICs).

It is well known that pick-and-place machines are used to place a broad range of electronic components onto substrates, such as printed circuit boards or lead frames. Existing technologies provide either a fast, or alternatively, an accurate, pick-and-place performance but not both. One type of pick-and- place machine includes a rotatable turret having a plurality of pick/place heads, an example of which is disclosed in DE10230901.

With the advent of 3D ICs, it has become necessary to place dies in a 3D stack which requires very high accuracy, for example, to within a placement tolerance of less than one micrometer in some applications.

It is an object of the present invention to provide a pick-and-place machine which is able to place components to a high degree of accuracy, for example, to meet the needs of 3D IC manufacture, while doing so at a commercially viable rate.

With this in mind, according to a first aspect, the present invention may provide a pick-and-place machine, comprising:

a frame including a shaft; a turret comprising a plurality of pick/place heads, and an inertial balance wheel, both being mounted for rotation about the axis of the shaft;

a first electromechanical device for rotating the turret during pick-and-place operation and comprising a magnetic field- generating part and an electrical current- carrying part, one part being on the turret and one part being on the inertial balance wheel,

wherein the machine is constructed such that torque developed by the first electromechanical device causes angular acceleration of the turret in one direction and angular acceleration of the inertial balance wheel in the opposite direction.

During pick-and-place operation, the turret angularly accelerates first positively and then negatively between each pick/place operation. The first aspect of the present invention prevents, or at least substantially reduces, the transmission of reaction forces caused to the frame by the angular acceleration of the turret through the provision of the inertial balance wheel which is caused by the reaction forces to angularly accelerate in a direction opposite to the turret. In this way, even when the machine is operating at high speeds, that is high positive and negative angular accelerations are required, vibration of the frame is eliminated, or at least kept low, whereby high placement accuracy can be achieved.

Preferably, the turret is rotatable such that each pick/place head can be moved to a pick position and to a place position, each pick/place head comprising a translator part of an actuator, wherein the machine further comprises a stator part of an actuator fixed to the frame and located at the pick position, and a stator part of an actuator fixed to the frame and located at the place position, the machine being arranged such that when a said pick/place head is located at a said pick or place position an operative actuator is formed, said operative actuator being operable to perform a pick or place movement.

By fixing the stator part of the actuator to the frame, the reaction forces produced when performing a pick or place movement are transmitted to the frame, thereby avoiding vibration at the turret.

Preferably, the drive shaft is horizontal, and the machine further comprises a pick stage located to one side of the turret and a place stage located to the other opposite of the turret, wherein both stages are arranged to hold a substrate in a vertical plane.

Such an orientation is beneficial in minimizing the tendency of contaminants from clinging to the substrate, or to the surface of a die.

Advantageously, the machine further comprises blower means for sending a clean air flow down over the surfaces of the pick stage and the place stage to further assist with the elimination of contaminants.

According to a second aspect, the present invention may provide a pick-and- place machine, comprising:

a frame including a shaft;

a turret comprising a plurality of pick/place heads, each pick/place head comprising a translator part of an actuator, the turret being mounted for rotation about the axis of the shaft such that each pick/place head can be moved by turret rotation to a pick position and to a place position,

the machine further comprising a stator part of an actuator fixed to the frame and located at the pick position and a stator part of an actuator fixed to the frame and located at the place position, the machine being arranged such that when a said pick/place head is located at a said pick or place position an operative actuator is formed, said operative actuator being operable to perform a pick or place movement.

According to a third aspect of the present invention, the present invention may provide a pick-and-place machine, comprising:

a frame including a horizontally-oriented shaft;

a turret, comprising a plurality of pick/place heads, mounted for rotation about the axis of the shaft;

a pick stage located to one side of the turret and a place stage located to the other opposite side of the turret,

wherein both stages are arranged to hold a substrate in a vertical plane.

According to a fourth aspect, the present invention may provide a turret assembly for a pick-and-place machine, comprising:

a turret comprising a plurality of pick/place heads; and an inertial balance wheel, both being mountable for rotation about the axis of a shaft of a support frame;

a first electromechanical device for rotating the turret during pick-and-place operation and comprising a magnetic field- generating part and an electrical current- carrying part, one part being on the turret and one part being on the inertial balance wheel, wherein the turret assembly is constructed such that torque developed by the first electromechanical device causes angular acceleration of the turret in one direction and angular acceleration of the inertial balance wheel in the opposite direction.

As used herein, the term "angular acceleration" is used broadly to encompass both angular acceleration and angular deceleration. Angular acceleration is referred to as positive angular acceleration, and angular deceleration is referred to as negative angular acceleration.

Other aspects of the present invention and further preferred features are described in the following description and defined in the appended claims.

Exemplary embodiments of the invention are hereinafter described with reference to the accompanying drawings, in which:

Figure 1 shows a schematic front view of a first pick-and-place machine;

Figures 2(a) and 2(b) show a cross-sectional view and an axial- sectional view of the turret assembly shown in Figure 1;

Figure 3 shows a schematic block diagram of a second pick-and-place machine; and

Figures 4(a) and 4(b) show schematic views of parts of an individual pick/place head as it reaches a pick or place position, and at a pick or place position, respectively.

A first pick-and-place machine generally designated 10 is shown in Figure 1. The machine 10 comprises a support frame 12 to which a turret assembly 14 is mounted for rotation about a shaft 15 (visible in Figures 2(a), (b)) having an axis labeled X. The machine 10 further comprises a pick stage 16 fixed to the frame 12 to the right hand side of the turret assembly 14 and a place stage 18 fixed to the frame 12 on the left hand side of the turret assembly 14. The pick stage 16 comprises a substrate in the form of a pick wafer 16a containing an array of dies ready for placement. The pick stage 16 can adjust the position of the pick wafer 16a in two dimensions within the plane of the wafer. The place stage 18 comprises a substrate 18a for holding the dies during stacking. The place stage 18 can adjust the position of the substrate 18a in two dimensions within the plane of the substrate 18a. The pick-and-place machine 10 further comprises a down flow unit 26 for sending a clean air flow over the surfaces of the pick stage 16 and the place stage 18. The air flow is filtered and has a very low ISO cleanliness class. The turret assembly 14 comprises a turret 20 having a turret body 22 in the form of a thick annular ring having 8 pick/place heads 24a — h disposed at equal angular intervals around the circumference of the turret body 22. Each pick/place head 24 comprises a vacuum nozzle which can be moved radially between an extended position and a retracted position in order to perform a pick or place movement.

Referring to Figure 2(b), the turret assembly 14 further comprises an inertial balance wheel 30 also mounted about the shaft 15. The inertial balance wheel 30 also takes the form of a thick annular ring having approximately the same dimensions and mass as the turret body 22. The turret 20 and the inertial balance wheel 30 are both mounted for free rotation about the shaft 15 by air bearings 25.

In other embodiments, rolling element bearings can be used instead.

The turret assembly 14 further comprises a first electromechanical device 40 comprising a magnetic field- generating part 42 secured to the turret body 22 and an electrical current- carrying part 44 secured to the inertial wheel balance. The magnetic field- generating part 42 comprises 12 permanent magnets 42 a — 1, each located at equal angular intervals around the circumference of the turret body 22 as best visible in Figure 2(a).

The electrical current- carrying part 44 comprises 12 coils 44 a - 1, each located at equal angular intervals around the circumference of the inertial balance wheel 30 and corresponding with a permanent magnet 42 a - 1. The electromechanical device 40 may be thought of as a linear motor with its constituent elements folded into circles centered on the axis X. The electromechanical device 40 serves to rotate the turret 20 during pick-and- place operation.

In other embodiments, the electrical current- carrying part 44 is secured to the turret body 22 and the magnetic field- generating part 42 is secured to the inertial balance wheel 30. In other embodiments, the first electromechanical device 40 may comprise an induction or asynchronous motor in which the magnetic field- generating part 42 comprises coils which generate a magnetic field and the electrical current- carrying part 44 comprises a conductor within which eddy currents are generated. The conductor may comprise a cylinder or be in a cage configuration.

In operation, as shown in Figure 1, the turret 20 is rotated anticlockwise using an indexing motion. At standstill, a pick/place head at the pick position, corresponding to pick/place head 24c in Figure 1, picks up a die (unlabelled) from the pre-positioned pick wafer 16a. Simultaneously, a pick/place head at the place position, corresponding to pick/place head 24a in Figure 1, places the die onto the pre-positioned substrate 18a. The vertical orientation of the pick wafer 16a and the substrate 18a in conjunction with the clean air flow supplied by the down flow unit 26 serve to prevent the accumulation of contamination on the surfaces of the dies. It will be appreciated that the creation of a clean environment within the machine 10, especially at the pick stage 16 and the place stage 18, enables the machine 10 to be located in an environment with less stringent cleanliness. As the turret 20 is indexed to the next pick/place position, in which the pick/place head 24f is at the pick position and the pick/place head 24b is at the place position, the electromechanical device 40 is driven so as to develop a torque which initially causes the positive angular acceleration of the turret 20 in the anticlockwise direction until it reaches a maximum angular velocity, after which a torque is developed in the opposite direction to cause the negative angular acceleration of the turret 20 in the anticlockwise direction, whereby the turret 20 reaches standstill at the next pick/place position. Since the inertial balance wheel 30 is freely mounted to the shaft 15, reaction forces from the angular accelerations required to rotate the turret 20 in the manner described are not transmitted to the frame 12 but rather to the inertial balance wheel 30 causing it to angularly accelerate in the clockwise direction.

In this way, even when the machine 10 is operating at high speeds, that is high positive and negative accelerations are required, vibration of the frame 12 is eliminated, or at least kept low, whereby high placement accuracy can be achieved.

When subsequently, parts similar to those described in relation to the first pick-and-place machine shown in Figures 1 and Figures 2(a), (b) are referred to, the same reference numeral is used.

Figure 3 shows a second pick-and-place machine 10. For diagrammatic simplicity, most of the frame 12, the pick/place heads 24 and the pick-and-place stages 16, 18 have not been illustrated. The turret assembly 14 shown in Figure 3 differs from that of the first pick-and-place machine in that, the turret 20 is mounted directly to the outer circumference of the inertial balance wheel 30 via an air bearing 25. The machine 10 comprises a control system 50 including a turret position control feedback loop 52. The control loop 52 comprises means 54 for setting the desired turret position, a comparator 56 for comparing the desired turret position with an actual turret position signal supplied by a transducer 60 to produce an error signal. The error signal is fed to a loop controller 62 which supplies a control signal to a driver unit 64 for driving the electromechanical device 40. The transducer 60 optically measures the position of the turret 20 with respect to the fixed world through indices on the shaft 15 which either directly yield an indication of position or are used to estimate angular velocity which is then used to calculate a position.

In operation, the second pick-and-place machine 10 operates like the first pick- and-place machine. A signal is applied by means 54 designating the next pick/place position. Through the operation of the control loop 52, the turret 20 is indexed to that position. Again, as the torque is developed in the electromechanical device 40 to angularly accelerate the turret 20 in a clockwise direction the reaction forces cause the inertial balance wheel 30 to counter rotate. In this way, vibration in the frame 12 is eliminated, or at least kept low, whereby high placement accuracy can be achieved.

The control system 50 may be incorporated into the first pick-and-place machine.

In practice, the inertial balance wheel 30 may not come to a standstill during operation. For this reason, the second pick-and-place machine 10 is preferably provided with means, coupled between the inertial balance wheel 30 and the shaft 15, for reducing the angular velocity of the inertial balance wheel 30. In one embodiment, this is achieved by a passive damping means such as an array of magnets located on the inertial balance wheel 30 and a coating of conducting metal on the turret 20, or vice versa, to induce eddy currents. In another embodiment, a second electromechanical device, similar to the first electromechanical device 40, can be distributed across the inertial balance wheel 30 and the shaft 15, one part being on the inertial balance wheel 30 and one part being on the shaft 15, and used to actively control the angular velocity of the inertial balance wheel 30 by means of a feedback control loop similar to the control loop 52. An active control loop is advantageous in that it allows the damping applied to the inertial balance wheel 30 to be adjusted. When critical processes are carried out, the damping between the inertial balance wheel 30 and the shaft 15 should be as low as possible because, when damping is applied, reaction forces that are partly being transmitted to the shaft cause vibration in the frame.

The various means for reducing the angular velocity of the inertial balance wheel may also be incorporated into the first pick-and-place machine.

The centre of the turret 20 and the shaft 15 are both preferably hollow. This enables moving inertias to be kept low and creates space for other components, for example, cable feedthroughs and sensors.

Figures 4(a), (b) show various parts making up an actuator for radially moving a nozzle of a pick/place head 24 between a retracted position and an extended position. The arrangement shown is suitable for incorporation into either the first or second pick-and-place machines.

The frame 12 of the machine 10 supports a stator part 72 of an actuator 70 at the pick position and at the place position. Only the place position is shown in Figures 4(a), (b). The stator part 72 comprises a housing portion 74 within which is provided a coil assembly 76. The stator part 72 further comprises a coupling portion 77 rigidly fixing the housing portion 74 to the frame 12. Each pick/place head 24 comprises a translator part 80 comprising a permanent magnet assembly 82 and an actuator member 84 mounted for inward and outward radial motion. The attachment of the outward end of member 84a to the nozzle is omitted for diagrammatic clarity.

In operation, as the pick/place head 24 moves, as illustrated in Figure 4(a) into the place position, the stator part 72 located at the place position and the translator part 80 carried by the pick/place head 24 become aligned to form an operative actuator as the standstill position in Figure 4(b) is reached. In this position, the magnet assembly 82 sits in the functional area of the coil assembly 76, and thus the actuator 70 can be controlled via a current supplied to the coil assembly 76 so as to move the translator part 80 axially between a radially retracted position and a radially extended position to perform a placement motion. As the translator part 80 moves, the reaction force is transmitted via the stator part 72 to the frame/fixed world. Since the reaction force is transmitted to the frame/fixed world, there is no disturbance of the turret 20. Since the turret 20 carries the nozzle, the absence of disturbance/vibration to the turret 20 assists with positioning accuracy.

It is an advantage of this embodiment of the invention that no electrical cables need be attached to the turret 20 for driving the nozzle activators, although some cables may be needed, for example, for measurement purposes.

Furthermore, it will be appreciated that by only carrying a part of the actuator 70 on the turret 20 the overall mass of the turret 20 can be kept low which enables increased speed of throughput or increased placement accuracy (depending on which is required).

Claims

1. A pick-and-place machine, comprising:

a frame including a shaft;

a turret comprising a plurality of pick/place heads, and an inertial balance wheel, both being mounted for rotation about the axis of the shaft;

2. A machine as in claim 1, wherein the turret and inertial balance wheel are directly mounted to the shaft.

3. A machine as in claim 1, wherein the turret is mounted to the outer circumference of inertial balance wheel, and the inertial balance wheel is directly mounted to the shaft.

4. A machine as in any preceding claim, wherein the turret is rotatable such that each pick/place head can be moved to a pick position and to a place position, each pick/place head comprising a translator part of an actuator, wherein the machine further comprises a stator part of an actuator fixed to the frame and located at the pick position, and a stator part of an actuator fixed to the frame and located at the place position, the machine being arranged such that when a said pick/place head is located at a said pick or place position an operative actuator is formed, said operative actuator being operable to perform a pick or place movement.

5. A machine as in any preceding claim, wherein the drive shaft is horizontal, and the machine further comprises a pick stage located to one side of the turret and a place stage located to the other opposite of the turret, wherein both stages are arranged to hold a substrate in a vertical plane.

6. A machine as in any preceding claim, further comprising blower means for sending a clean air flow down over the surfaces of the pick stage and the place stage.

7. A machine as in any preceding claim, further comprising a first feedback control loop for controlling the position of the turret.

8. A machine as in any preceding claim, further comprising means for passively damping the angular velocity of the inertial balance wheel.

9. A machine as in any of claims 1 to 7, further comprising a second electromechanical device comprising a magnetic field- generating part and an electrical current- carrying part, one part being on the inertial balance wheel and one part being on the shaft, and a second feedback control loop for controlling the angular velocity of the inertial balance wheel via the second electromechanical device.

10. A machine as in claim 9, wherein the second feedback control loop may be used to selectively apply damping to the rotation of the inertial balance wheel.

11. A machine as in any preceding claim, wherein the turret is hollow.

12. A machine as in any preceding claim, wherein the shaft is hollow.

13. A turret assembly suitable for use in a pick-and-place machine according to any preceding claim, comprising

a turret comprising a plurality of pick/place heads, an inertial balance wheel, both being mountable for rotation about the axis of a shaft of a support frame;

a first electromechanical device for rotating the turret during pick-and-place operation and comprising a magnetic field- generating part and an electrical current- carrying part, one part being on the turret and one part being on the inertial balance wheel;

wherein the turret assembly is constructed such that torque developed by the first electromechanical device causes angular acceleration of the turret in one direction and angular acceleration of the inertial balance wheel in the opposite direction.

14. A pick-and-place machine, comprising:

a frame including a shaft;

15. A pick-and-place machine, comprising:

a frame including a horizontally-oriented shaft;

a pick stage located to one side of the turret and a place stage located to the other opposite of the turret,

wherein both stages are arranged to hold a substrate in a vertical plane.