Assembly and method for IC unit engagement

Abstract

A picker assembly comprising: a plurality of pickers in selective variable spaced relation; a shaft; a plurality of internal positioning plates in sliding engagement with the shaft, each of said internal positioning plates placed intermediate adjacent pickers; a pair of end positioning plates coupled in sliding engagement with the shaft, each of said end positioning plates placed on an outer side of end pickers; said end and internal positioning plates co-axial with said shaft; a pair of cams, each placed in sliding engagement at either end of said shaft, and coupled longitudinally with the end positioning plates; a pair of fixed cam followers each in rolling engagement with a corresponding helical follower surface on each of said cams; wherein on rotation of the shaft, the cam is biased by the pair of cam followers, said rotation of the cams rotating the end and internal positioning plates, such that the selective variability in spacing is provided by rotation of the shaft such that thickness variation of the cam plates move the respective pickers along an axis parallel to the shaft.

Description

[0001] ASSEMBLY AND METHOD FOR IC UNIT ENGAGEMENT

[0002] Field of the Invention

[0003] The invention relates to the singulation of integrated circuit units and in particular to the assemblies used to engage and transport the individual units. In particular, the invention relates to the adaptability of said picker assemblies to adjust the spacing of individual pickers within the assembly.

[0004] Background

[0005] In designing machinery for the processing of substrates and individual IC units, key factors such as minimizing waste, maintaining units per hour (UPH) and limiting downtime for retooling are all key design determinants.

[0006] Considering adaptability of said machines, in order for a machine to be useful for a range of applications, it will be necessary for it to accommodate substrates having different spacing between the IC units. Whilst the machine can be retooled for each application, it would be more efficient if the machine can be adapted relatively simply to accommodate said spacing. In particular the picker assemblies used to transport the singulated IC units between stations are dependent upon the spacing of the units in order to engage the units collectively. It would therefore be useful if the spacing of the pickers within the picker assembly could be adjusted to accommodate substrates having different IC unit spacing. Some systems have been trialled to achieve this function. For instance, one system uses a series of shaped blocks between each picker within the picker array. To ensure the pickers move within the array, a spring system arranged to bias the pickers inwards are placed peripherally to the picker array. If the springs apply a large enough force, rotating the differentially shaped blocks will allow the pickers to vary their pitch. However, for processing batch runs of integrated circuit (IC) substrates, it may be necessary to rapidly vary the pitch of the pickers several times in succession. Given the mass of the picker array and intermediate blocks, there is an upper limit to the speed =by which the springs can react without causing a jittering or vibration. Further, high speed operation in rapid succession may lead to hysteresis effects, and so affecting the accuracy of the pitch positioning.

[0007] With decreasing profit margins for integrated circuits, and in particular, memory, the pressure to reduce processing costs is significant and hence the need to speed production whilst maintaining quality. It follows that the cost of infrastructure to achieve these processes will equally suffer from pressure to reduce cost whilst maintaining speed and quality.

[0008] Summary of Invention

[0009] In a first aspect the invention provides a picker assembly comprising: a plurality of pickers in selective variable spaced relation; a shaft; a plurality of internal positioning plates in sliding engagement with the shaft, each of said internal positioning plates placed intermediate adjacent pickers; a pair of end positioning plates coupled in sliding engagement with the shaft, each of said end positioning plates placed on an outer side of end pickers; said end and internal positioning plates co-axial with said shaft; a pair of cams, each placed in sliding engagement at either end of said shaft, and coupled longitudinally with the end positioning plates; a pair of fixed cam followers each in rolling engagement with a corresponding helical follower surface on each of said cams; wherein on rotation of the shaft, the cam is biased by the pair of cam followers, said rotation of the cams rotating the end and internal positioning plates, such that the selective variability in spacing is provided by rotation of the shaft such that thickness variation of the cam plates move the respective pickers along an axis parallel to the shaft.

[0010] In a second aspect the invention provides A method for picker assembly for selectively varying the spacing of pickers within a picker assembly, the method comprising the steps of: rotating a shaft having a plurality of co-axial end and internal positioning plates, said cam having a variable thickness, said cam plates in engagement with said pickers; biasing said pickers using said end and internal positioning plates, and consequently; wherein the selective variability in spacing is provided by rotation of the shaft moving the respective pickers along an axis parallel to the shaft so as to vary the respective picker spacing.

[0011] Therefore, by providing a cam follower and cam arrangement, a more rigid reaction may be applied to varying the picker pitch, rather than a resilient, or flexible, member such as a spring. Brief Description of Drawings.

[0012] It will be convenient to further describe the present invention with respect to the accompanying drawings that illustrate possible arrangements of the invention. Other arrangements of the invention are possible and consequently, the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention.

[0013] Figure 1 is an isometric view of a picker assembly having a pitch tracker according to one embodiment of the present invention;

[0014] Figure 2 is an isometric view of the a picker assembly of Figure 1;

[0015] Figure 3 is an elevation view of the a picker assembly of Figure 1, and Figure 4 is a detail isometric view of the picker assembly of Figure 1.

[0016] Detailed Description

[0017] Picker assemblies of the prior art require pitch trackers adjusted by spring systems to provide a positive force to ensure the pitch adjustment is maintained. A biasing force is applied by a variety of mechanisms, which react against the spring force applied by the spring system.

[0018] However, spring systems are an inefficient means of maintaining a precise position of the individual pickers. Picker assemblies are subjected to a rapid rate of processing of IC units. However, as the mass of the picker array moves against the spring system, the springs are subjected to jerking or jittering. There is consequently a limit on the speed by which a picker assembly, using a spring system, can operate.

[0019] Further, on application of a force to the spring, there is an initial compression before the spring can respond. This leads to imprecise positioning of the pickers by the spring system and so hampering the ability to change rapidly the pitch. As is discussed below, this is compared to the application of a positioning force from a rigid arrangement, as show demonstrated by the present invention, with no such initial compression and effectively an instantaneous response time.

[0020] Figures 1 to 4 show an embodiment of the present invention that provides a substantial improvement to pitch tracking for a picker array.

[0021] A picker assembly 1 includes a pitch tracker 5. The pitch tracker 5 includes an array 10 of pickers 15, with each picker 15 including a vacuum nozzle 20 arranged to engage an IC unit. The picker array 10 is positioned on a rotatable shaft 25, having an actuator 35 arranged to rotate the shaft.

[0022] Located on the shaft 25 is a plurality of internal positioning plates 30. Each internal positioning plate 30 placed intermediate, and in contact with adjacent picker, with end positioning plates placed on an outer side of the end pickers. The end and internal positioning plates 30, 37 are mounted as a sleeve over the shaft 25. As shown in Figure 4, each end and internal positioning plate 30, 37 includes a peripheral edge 57 that varies uniformly in thickness circumferentially about the respective positioning plate 30, 37. As the end and internal positioning plates rotate, the ridge either pushes outwards or allows the picker to be drawn inwards, as the thickness varies on the ridge 57.

[0023] At both end of the shaft, and coupled to the end positioning plates 37, is a cam 40 in rolling engagement with a cam follower 45. The cam follower 45 contacts the cam 40 on a helical follower surface 50 through a roller in rotating engagement with the follower 45. Thus the roller rolls along the cam surface as the cam 40 rotates.

[0024] As the shaft 25 rotates, the cam followers 45 bias against the cam 40. The helical path of the follower surface consequently reacts against the cam 40 to either open or close the interstitial spaces of the internal positioning plates 30. The internal positioning plates 30, using the uniformly variable thickness edge 57 then adjust the pitch of the pickers to either a wider or narrower pitch, as required. T will be appreciated that the uniform variability of the ridge thickness may be replaced by a step arrangement, such that the size of the steps correspond to preferred pitch spacing of the pickers.

[0025] Thus, to position the pickers to the desired pitch, the shaft is rotated, which consequently rotates the cam 40. Having a helical follower surface 50, rather than a system of spring, provides for a fine adjustment through the cam follower, which improves the speed of adjustment of the pitch of the picker array, without lag or jittering caused by a spring. Figure 3 shows a follower plate 65 to which the cam follower is mounted. The follower plate is mounted to the pitch tracker block through screws or bolts, which fit into slots of the plate 65. The slots allow the follower plate to slide 70 when the mounting screws are loosened, which permits a fine adjustment of the cam follower, and so ensuring a tight engage between the cam follower and the cam.

Claims

Claims:

1. A picker assembly comprising: a plurality of pickers in selective variable spaced relation; a shaft; a plurality of internal positioning plates in sliding engagement with the shaft, each of said internal positioning plates placed intermediate adjacent pickers, a pair of end positioning plates coupled in sliding engagement with the shaft, each of said end positioning plates placed on an outer side of end pickers; said end and internal positioning plates co-axial with said shaft; a pair of cams, each placed in sliding engagement at either end of said shaft, and coupled longitudinally with the end positioning plates; a pair of fixed cam followers each in rolling engagement with a corresponding helical follower surface on each of said cams; wherein on rotation of the shaft, the cam is biased by the pair of cam followers, said rotation of the cams rotating the end and internal positioning plates, such that the selective variability in spacing is provided by rotation of the shaft such that thickness variation of the cam plates move the respective pickers along an axis parallel to the shaft.

2. The assembly of claim 1 wherein the thickness variation of the end and internal positioning plates is continuous about the circumference of the end and internal positioning plate.

3. The assembly according to claim 1 wherein the thickness variation is stepped, said stepped thickness a function of predetermined spacing of said pickers.

4. The assembly according to claim 1 wherein the internal positioning plates are placed so as to be engaged with adjacent pickers, said internal positioning plates arranged on the shaft such that the thickness of each of the internal positioning plates is the same at each point around the circumference of each plate.

5. A method for picker assembly for selectively varying the spacing of pickers within a picker assembly, the method comprising the steps of: rotating a shaft having a plurality of co-axial end and internal positioning plates, said cam having a variable thickness, said cam plates in engagement with said pickers; biasing said pickers using said end and internal positioning plates, and consequently; wherein the selective variability in spacing is provided by rotation of the shaft moving the respective pickers along an axis parallel to the shaft so as to vary the respective picker spacing.

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