Die placement head with turret

Abstract

Herein described is a system for the placement of dies on a substrate that uses a rotating turret carried with the die placement system to supply die placement heads necessary for the placement of various dies on a substrate, where multiple dies are to be placed, to a force application rod, thereby allowing for the rapid and efficient placement of a variety of dies on a single substrate.

Claims

1. A system for the placement of dies on a substrate comprising: a frame; a housing fixed to said frame, said housing comprising a guide channel encompassing a force application rod, which extends from a distal end of said housing, said force application rod configured for linear motion relative to said housing and the application of linear force, a measurement device configured to measure the linear motion of said force application rod, said force application rod further comprising a die placement head holding aperture at a distal end thereof; a turret rotatably fixed to said frame comprising a rotation measuring device and a plurality of die placement head holding portions positioned substantially adjacent a periphery of the turret, wherein each die placement head holding portion comprises two concentric apertures, a first aperture and a second aperture, said first aperture positioned adjacent the distal end of said housing and extending fully through said turret, said second aperture positioned on the side of the turret opposite said first aperture and concentric therewith, wherein said first aperture is of a size only slightly larger than that of said force application rod and said second aperture extends only partially into said turret and wherein, upon rotation, each of said plurality of die placement head holding apertures can be brought into alignment with said force application rod; and a motor fixed to said frame and configured to rotate said turret upon activation.

2. The system of claim 1 further comprising at least one die placement head having a proximal end configured to be held in said die placement head holding aperture of said force application rod during use in a die placement operation, a central region configured to be removably retained in said second aperture of said turret upon retraction of said force application rod above said turret and a distal end including a die holding and retaining portion.

3. The system of claim 1 wherein said plurality of die placement head holding portions of said turret are configured in multiple concentric rows.

4. The system of claim 1 wherein said die placement head holding aperture of said force application rod further comprises magnets configured to retain a die placement head inserted therein.

5. The system of claim 1 wherein said turret further comprises magnets configured to retain a die placement head in at least one of the plurality of die placement head holding portions thereof.

6. The system of claim 1 wherein said die placement head holding aperture of said force application rod is in operative communication with a controllable vacuum source.

7. The system of claim 6 further comprising a die placement head configured to allow vacuum to be drawn therethrough.

8. The system of claim 1 wherein a portion of said force application rod external to said housing further comprises a projection, wherein said projection is restricted from rotation but substantially unrestricted during normal usage against linear motion.

9. The system of claim 8 wherein said projection is hollow, thereby allowing vacuum to be pulled therethrough or pressure forced therein.

10. The system of claim 1 wherein said force application rod is an air piston, said guide channel is an air cylinder, and said guide channel is in communication with a vacuum or pressure source, wherein the introduction of vacuum or pressure into said guide channel results in a linear movement of or application of force to the force application rod.

11. The system of claim 10 wherein said guide channel further comprises a spring configured to bias linear movement of said force application rod.

12. The system of claim 10 wherein said force application rod is of a polygonal shape and said guide channel is a corresponding polygonal shape, whereby said polygonal shape provides resistance to rotation of said force application rod.

13. The system of claim 1 further comprising at least one voice coil which at least partially surrounds said force application rod, wherein said at least one voice coil is configured to induce linear movement of or the application of linear force into said force application rod.

14. The system of claim 1 wherein said motor produces rotational movement of said turret via a belt and pulley drive system, the pulley drive system comprising at least two pulleys and at least one belt.

15. The system of claim 14 wherein said belt is a timing belt and said pulleys are timing pulleys.

16. The system of claim 1 further comprising a hall-effect sensor, wherein said hall-effect sensor is configured to measure a location of said force application rod.

17. The system of claim 1 wherein said die placement head holding aperture is tapered, having a larger opening adjacent the distal end of the force application rod and becoming relatively narrower further from said distal end of said force application rod.

18. The system of claim 17 wherein said tapered die placement head holding aperture is conical in shape.

19. The system of claim 17 further comprising at least one die placement head having a proximal end configured to be held in said tapered die placement head holding aperture of said force application rod during use in a die placement operation, a central region configured to be removably retained in said second aperture of said turret upon retraction of said force application rod above said turret and a distal end including a die holding and retaining portion.

20. The system of claim 1 wherein vacuum or pressure held between said force application rod and an end of said housing guide channel is used as an air spring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of a die placement system wherein the die placement head of the force application rod is in an unloaded state, configured in accordance with one embodiment of the present disclosure;

(2) FIG. 2 is a cross-sectional perspective view of a die placement system wherein the die placement head of the force application rod is in an unloaded state, configured in accordance with one embodiment of the present disclosure;

(3) FIG. 3 is a front elevation sectional view of a die placement system wherein the die placement head of the force application rod is in an unloaded state, configured in accordance with one embodiment of the present disclosure;

(4) FIG. 4 is a perspective view of a die placement system wherein the die placement head of the force application rod is in a loaded state, configured in accordance with one embodiment of the present disclosure;

(5) FIG. 5 is a perspective view of a die placement system wherein the die placement head of the force application rod is in a loaded state configured in accordance with one embodiment of the present disclosure; and

(6) FIG. 6 is a bottom elevation view of a die placement system configured in accordance with one embodiment of the present disclosure.

DETAILED DESCRIPTION

(7) In general terms, a die placement cycle comprises the following steps: 1. Determining the position of the die in 3D space using markers on the die and substrate themselves, which are generally referred to as fiducials; 2. Pickup of the die by the die placement head 118; 3. Imaging and angular or theta correction; and 4. Placement of the die onto the substrate. For the placement of multiple dies on a single substrate, steps 1-4 are repeated as necessary.

(8) Dies may be presented for placement in various ways, such as in wafers, waffle packs, and tape & reel. Using the common case of wafer processing for an example, wafers are received, after dicing into individual dies, on a film frame. Cassettes of wafers are then fed to the machine, and one wafer is indexed into the machine for placement. In order to pick a device from the frame, an ejector pin is typically used to push the die off of the frame while the die placement head 118 lifts the die, often through the use of a vacuum. The most common approach used for component assembly is to perform the dispensing and placement operations on one machine that is commonly referred to as a die bonder.

(9) Dies are extremely small in size, typically on the order of 10 to 15 mils in any given direction. Because of their tiny size, the mechanism for moving and controlling a tool for picking up and transferring such a die must be constructed to minimize tolerances as much as possible while maintaining high throughput to be commercially viable. The situation becomes even more challenging when multiple die types are to be placed on a single substrate. Because of the small size and non-standardized nature of dies, different tool heads, referred to as die placement heads 118, must be used for each die type.

(10) Reduction of the cycle time for such operations while maintaining precision and accuracy is crucial to the cost-effective production of die/substrate packages. An increase in the speed at which a die placement head 118 can be changed results in an immediate improvement to the total cycle time required to perform the die placement operation. Movement of the die placement head 118 also takes time and results in a longer cycle time than if such movement could be eliminated. Also, since excessive movement of the die placement head 118 can be detrimental to accuracy, keeping such movement to a minimum can help to enhance the precision and accuracy of the die placement system 100.

(11) The present disclosure describes an improved die placement system 100 that allows for the efficient placement of multiple die types by a single die placement system 100 during a die placement cycle, yielding improvements in cycle times and accuracy. This is accomplished through minimization of the movement of the die placement system 100 in operations involving the placement of multiple dies on a single substrate where die placement heads 118 must be swapped to accommodate differently sized dies by incorporating a die placement head 118 holding turret 112, a rotating holder for tools, into the die placement system 100. The turret 112 of such a system carries all die placement heads 118 necessary for use in a particular application, negating the need for the die placement system 100 to return to a traditional tool holder between die placement operations involving differently sized dies. In embodiments, the turret 112 may incorporate permanent magnets, electro-magnets, vacuum passages or combinations thereof to retain the die placement heads 118 when not in use. Other suitable means of retaining the die placement heads 118 within the turret 112 would be apparent to one of ordinary skill in the art.

(12) The die placement system 100 of the present disclosure, in one embodiment, comprises a housing 102, frame, motor 104, transmission 106/108, force application rod 110, and linear measurement device. The housing 102 encompasses the force application rod 110 and linear measurement device. In embodiments, an encoder, hall-effect sensor, or other measuring device, as would be known to one of ordinary skill in the art, may be used to measure the linear travel of the force application rod 110. The frame connects the housing 102, turret 112 and motor 104, with the motor 104 operatively connected to the turret 112 by a force transmission means 106/108, to the remainder of the die bonding system, which is not shown.

(13) In embodiments, the force transmission means 106/108 is a belt 106 and pulley 108 system. In other embodiments, the belt 106 is a timing belt 106 and the pulleys 108 are timing pulleys 108, respectively. In this case, timing belt 106 refers to a toothed belt 106 and timing pulley 108 refers to pulleys 108 having teeth that correspond to those of the timing belt 106, to prevent slippage so that the position of the components to each other, once calibrated, will be known during future operations.

(14) The turret 112 portion of the die placement system 100, in embodiments, has the capability to hold between 15-20 separate die placement heads 118, although more or less could be held. Some embodiments utilize a single row of tool-holding apertures 114 while others incorporate multiple rows of tool-holding apertures 114 into a single turret 112. Representative embodiments of the present disclosure show the turret 112 having a circular shape; other shapes, however, could also be used without departing from the scope of the current disclosure.

(15) Each turret 112 tool-holding aperture 114, in embodiments, may also comprise a lip 200 situated adjacent an upper edge thereof, the upper edge being considered the edge closest to the central portion of the die placement system 100. In such embodiments, the lip 200 is designed to prevent a die placement head 118 contained therein from passing through the turret 112 upon retraction of a force-application rod 110 therethrough. To function, the lip 200 must be small enough to allow the force-application rod 110 to penetrate therethrough without impeding its motion, but must also intrude into the tool-holding aperture 114 sufficiently to prevent the die placement head 118 from passing therethrough upon retraction of the force-application rod 110.

(16) The die placement system 100 must also ensure that the die does not rotate during placement, which would prevent proper alignment. One way that this can be accomplished is through the use of an anti-rotation member 116. In one embodiment, the anti-rotation member 116 comprises a substantially perpendicular projection from the force-application rod 110 that is supported by bearings, bushings, or similar mechanical restraints that are fastened to the frame of the die placement system 100.

(17) In embodiments, the above-described substantially perpendicular projection 116 may be hollow. Such a design allows for a vacuum to be drawn or pressure provided to other parts of the die placement system 100, or indeed any other part of the larger system to which the die placement system 100 is connected, therethrough. For example, vacuum may be supplied to the force application rod tip 122 portion of the system for secure die placement head 118 holding. In embodiments, the vacuum provided to the force application rod tip 122 is distinct from vacuum operation of the larger die placement system 100.

(18) In other embodiments, the force application rod 110 may be of a polygonal shape corresponding to a force-application rod 110 guide channel 204 within the die placement system 100, specifically one contained within the housing 102. In still other embodiments, the force application rod 110 may utilize a square air bearing anti-rotate design built into the guide channel 204. The use of an air bearing anti-rotate offers less friction than other embodiments, allowing better repeatability under certain conditions.

(19) In such an embodiment, as well as other embodiments not yet described, the force-application rod 110 may be an air piston and the force-application rod 110 guide channel 204 may be an air cylinder.

(20) In still other embodiments, the position of and force applied by the force application rod 110 may be controlled by electrical means, such as through the use of a voice coil. A spring 206 internal to the housing 102 guide channel 204 may further be inserted or connected between the housing 102 and force application rod 110, residing in the guide channel 204, such that it biases the force application rod 110 to retract or extend in the absence of additional forces.

(21) In embodiments, a back side of the die placement heads 118 may be of a shape that corresponds to a tool-holding aperture 114 of the turret 112 in which they are designed to fit. The tool-holding aperture 114 may beneficially be keyed, i.e. contain a keyway 120, such that the die placement head 118 orientation is accurately known without requiring the use of additional sensors. Similarly, the force application rod tip 122 may beneficially incorporate a keyway 120 for the same reason. In embodiments, the back side of the die placement head 118 is circular with a keyed portion corresponding to the turret 112 keyway 120, although other shapes are also considered within the scope of this disclosure.

(22) In some embodiments, the tip 122, or tool-holding portion, of the force-application rod 110 may incorporate a tapered seat 202, proximal the turret 112 for retention of the die placement heads 118. In such embodiments, the die placement heads 118 would have a corresponding tapered portion on the side proximal the force-application rod 110, allowing for self-alignment of the interconnecting pieces of the die placement system 100. In one embodiment, the tapered seat 202 is a conical seat.

(23) Each and every page of this submission, and all contents thereon, however characterized, identified, or numbered, is considered a substantive part of this application for all purposes, irrespective of form or placement within the application. This specification is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. The particular embodiments disclosed above are illustrative only, as the application may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the application. Accordingly, the protection sought herein is as set forth in the claims below.