Multiple actuator wire bonding apparatus

Abstract

According to a first aspect of the present invention, there is provided a bond apparatus for bonding a wire to a bonding surface, comprising: a bond head body movably retained by a mounting portion; a first actuator; and a second actuator, wherein the bond head body has a tool portion configured to receive a bonding tool for receiving and bonding the wire and an actuator portion coupled with the first actuator and the second actuator, the first actuator and the second actuator being operative to act on the actuator portion for moving the bond head body with respect to the mounting portion to move the bonding tool with respect to the bonding surface.

Claims

1. A bond head for bonding a wire to a bonding surface, comprising: a bond head body movably retained by a mounting portion about a pivot having a pivot axis; a first actuator comprising a first coil positioned between first and second magnet stacks, wherein at least one of the first and second magnet stacks comprises a plurality of magnets; and a second actuator comprising a second coil positioned between the second magnet stack and a third magnet stack; wherein said bond head body has a tool portion configured to receive a bonding tool for receiving and bonding said wire and an actuator portion coupled with said first actuator and said second actuator, said first actuator and said second actuator being operative to act on said actuator portion for driving said bond head body to rotate about the pivot axis with respect to said mounting portion to move said bonding tool in reciprocating directions toward and away from said bonding surface, the first and second coils being spaced from each other in a direction that is parallel to an axial direction of the pivot axis.

2. The bond head of claim 1, wherein said first actuator is operative to generate a first force on said actuator portion and said second actuator is operative to generate a second force on said actuator portion.

3. The bond head of claim 2, wherein said actuator portion is configured to receive said first force and said second force and be urged in a direction due to a resultant force comprising a combination of said first force and said second force.

4. The bond head of claim 2, wherein said first actuator and said second actuator are operative to generate said first force and said second force with one of equal and unequal magnitudes.

5. The bond head of claim 2, wherein said first actuator and said second actuator are operative to generate said first force and said second force to act in one of a common and differing directions.

6. The bond head of claim 2, wherein at least one of said first actuator and said second actuator are operative to generate at least one of said first force and said second force with at least one of a time-varying magnitude and direction.

7. The bond head of claim 3, wherein said actuation portion is configured to combine said first force and said second force to generate said resultant force having at least one of a time-varying magnitude and direction.

8. The bond head of claim 2, wherein said first actuator and said second actuator are operative to generate said first force and said second force having equal magnitudes and acting in opposing directions to combine to produce a null resultant force.

9. The bond head of claim 1, wherein said first actuator and said second actuator each comprises a motor.

10. The bond head of claim 1, wherein said first actuator and said second actuator are collocated by said actuator portion.

11. The bond head of claim 1, wherein said first actuator is spaced apart from but connected to said second actuator by said actuator portion.

12. The bond head of claim 1, wherein said first actuator and said second actuator are both located for concurrent movement with said actuator portion.

13. The bond head of claim 1, wherein said actuator portion has a first housing portion which receives said first coil of said first actuator and a second housing portion which receives said second coil of said second actuator.

14. The bond head of claim 13, wherein said first coil of said first actuator is located in a fixed relationship with respect to said second coil of said second actuator by said actuator portion.

15. The bond head of claim 13, wherein said actuator portion comprises at least one brace extended between said first housing portion and said second housing portion.

16. The bond head of claim 1, wherein said first magnet stack of said first actuator is located in a fixed relationship with respect to said second magnet stack of said second actuator.

17. The bond head of claim 16, wherein said first magnet stack and said second magnet stack are located in a fixed relationship with respect to said mounting portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIGS. 1A to 1C illustrate an example of a prior art bond head;

(3) FIGS. 2A and 2B illustrate a bond head of one embodiment;

(4) FIG. 3 illustrates relative sizes and centres of gravity of actuator coils;

(5) FIG. 4 illustrates the arrangement of the bond head body with a magnet array of one embodiment;

(6) FIG. 5 illustrates a magnet array of another embodiment;

(7) FIG. 6 shows the bond head with its magnet array together with housings of one embodiment; and

(8) FIGS. 7A and 7B illustrate exemplary forces generated during operation of the bond head of one embodiment.

(9) In the drawings, like parts are denoted by like reference numerals.

DETAILED DESCRIPTION

(10) Before discussing embodiments of the invention in any more detail, an overview will first be provided. Embodiments provide an actuation mechanism which may be used by, for example, a bond head or other apparatus which requires improved actuation control. The actuator mechanism has more than one actuator, which are coupled to act together on the bond head. Having more than one actuator provides for increased control over the forces generated to move the bond head. Also, having more than one actuator provides structural advantages since each actuator can be smaller than an equivalent single actuator and the actuators couple with the bond head at different locations to improve structural rigidity. Furthermore, the actuators can be operated to generate cancelling forces to avoid changes in the operating of the bond head when transitioning to a stationary or inactive state.

(11) Bond Head

(12) FIGS. 2A and 2B illustrate a bond head 200 of a bonding apparatus according to one embodiment. FIG. 2A shows a perspective view and FIG. 2B shows a top view (omitting a wire clamp and a transducer to improve clarity). The arrangement and configuration of the bond head body 202 is identical to the arrangement mentioned above, with the exception of the provision of dual coils 214A; 214B and a dual actuator housing structure 204.

(13) The dual actuator housing structure 204 comprises a lateral component 205 which extends in an axial direction of the pivot 112 and has two flange structures 206A, 206B which extend transversely to the lateral component 205, away from the pivot 112 in a radial direction. The two flange structures 206A, 206B have recesses shaped to receive a corresponding coil 214A, 214B. The extended connection of the dual actuator housing structure 204 to the rest of the bond head body 202 along the axial direction of the pivot 112 helps to improve the stiffness of the bonding head which helps to improve its performance in operation.

(14) The coils 214A, 214B are held by the two flange structures 206A, 206B so that they extend away from the pivot 112 radially, with their major faces orientated to be generally parallel. The coils 214A, 214B are spaced apart by the two flange structures 206A, 206B to provide a void to receive a magnet array (not shown), as will be explained in more detail below.

(15) The dual actuator housing structure 204 has a bracing strut 208 extending between the flange structures 206A and 206B in order to further improve its rigidity which helps to improve its performance in operation.

(16) The bond head body 202 may be formed of component parts connected together or may be formed from a unitary component where the parts move together or in tandem. In either case, forces generated by either coil 214A, 214B are conveyed to its flange structure 206A, 206B and are received by the dual actuator housing structure 204 with the resultant force acting to move the bond head body 202 about the pivot 112.

(17) As illustrated in FIG. 3, in order to generate a predetermined amount of force, the size of a single coil 114 required to generate that amount of force is larger than the size of a pair of coils 214A, 214B operating together to generate the same amount of force. The smaller size of the coils 214A, 214B locates the centre of gravity 220 of the pair of coils 214A, 214B closer to the pivot 112, compared to the centre of gravity 120 of the single coil 114. Placing the centre of gravity 220 closer to the pivot 112 reduces motor inertia. In one exemplary arrangement, the inertia of the equivalent single coil is 47% higher than that of a dual coil and the natural frequency of the equivalent single coil is 550 Hz lower than that of a dual coil.

(18) FIG. 4 illustrates the arrangement of the bond head body 202 with a magnet array. The magnet array remains in a fixed position during operation of the bond head 200 when the bond head body 202 rotates about the pivot 112. The magnet array comprises a first magnet stack 300A adjacent one major face of the coil 214A and a second magnet stack 310A provided adjacent another major face of the coil 214A. This generates a magnetic field extending generally in the direction B, which is generally parallel to the axis of the pivot 112, with magnetic flux flowing perpendicularly through to major faces of the coil 214A. As current flows through the coil 214A in the direction I, a force is generated, generally in the direction F, which causes the bond head body 202 to pivot about the pivot 112, following the turning arc 215.

(19) The second magnet stack 310A is located adjacent one major face of the coil 214B and a third magnet stack 320A is provided adjacent another major face of the coil 214B. This generates a magnetic field extending generally in the direction B, which is generally parallel to the axis of the pivot 112, with magnetic flux flowing perpendicularly through to major faces of the coil 214B. As current flows through the coil 214B in the direction I, a force is generated, generally in the direction F, which causes the bond head body 202 to pivot about the pivot 112, following the turning arc 215.

(20) The arrangement of the dual coils 214A, 214B is more efficient due to its double layer magnet array design which provides for larger magnetic density, and so the coils themselves can be smaller. Also, the cooling efficiency of the dual coil arrangement is higher due to a larger heat-dissipating area.

(21) FIG. 5 illustrates an alternative magnet array where each magnetic stack 300B, 310B, 320B is formed from three magnets whose polarities are arranged as indicated. In particular, the outer magnets in each of the magnet stacks 300B, 310B, 320B have their polarities orientated to be generally parallel to the axis of the pivot 112 while the inner magnet in each stack 300B, 310B, 320B has its polarity orientated perpendicularly in the direction of the magnet stack. This provides for magnetic flux lines formed into a more rectangular shape to pass transversely through the major lengths of the coils 214A, 214B.

(22) FIG. 6 shows the bond head 200 with its magnet array 300A, 310A, 320A retained by its housing 330 and an upper housing 340 which houses optics and other control circuitry which provide driving currents and feedback during operation of the bond head 200.

(23) Bond Head Operation

(24) FIGS. 7A and 7B illustrate exemplary forces generated during operation of the bond head 200. As can be seen in FIG. 7A, assuming that when the coils 214A, 214B are energized with identical currents flowing in a specified direction, the coils 214A, 214B generate identical forces F.sub.A, F.sub.B operating in identical directions. The magnitude of the forces F.sub.A, F.sub.B can be varied by varying the magnitude of the current. The direction of the forces F.sub.A, F.sub.B can be varied by varying the direction of the current. This differential force generation provides for improved control of the bond head body 202. The forces F.sub.A, F.sub.B generated by the coils 214A, 214B act together on the dual actuator housing structure 204 with the combined, resultant force F.sub.R acting on the bond head body 202. Hence, it will be appreciated that the coils 214A, 214B may be driven with non-identical currents and/or with currents operating in opposing directions in order to vary the amount of resultant force F.sub.R experienced by the bond head 200 to provide flexible force configurations such as, for example high accelerating or decelerating forces, fine bonding force, or the like.

(25) As illustrated in FIG. 7B, in one mode of operation, the coils 214A, 214B are driven with currents of equal and opposite magnitudes in order to generate equal and opposite forces F.sub.A, F.sub.B so that current flowing through the coils may maintain thermal stability of the bond head 200. In other words, currents with opposite phases can be provided to the two coils 214A, 214B respectively to generate heat while the bond head 200 is in an idle state. As the forces F.sub.A, F.sub.B generated by each coil counter-balance each other, the resultant force F.sub.R has a zero value and the bond head 200 would stay still. This helps the bond head 200 to maintain thermal stability during idle periods.

(26) Although the present invention has been described in considerable detail with reference to certain embodiments, other embodiments are possible.

(27) Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.