APPARATUS FOR TRANSFERRING SEMICONDUCTOR CIRCUITS

Abstract

An apparatus for transferring chips from a first position to at least a second position includes: a rotatable transfer assembly including at least two transfer heads, each head for picking up a chip in the first position, and positioning the chip in the at least second position through rotation of the transfer assembly about an axis of rotation; a transfer assembly actuator for driving the transfer assembly together with the at least two transfer heads about the axis; and at least a first transfer head actuator structured for actuating at least one transfer head in a radial direction relative to the axis, the at least first transfer head actuator being mounted to the rotatable transfer assembly actuator and including an actuator element coupled to the at least one transfer head, the actuator element structured to be actuated in the direction of the axis relative to the rotatable transfer assembly actuator.

Claims

1. An apparatus for transferring chips from a first position to at least a second position, the apparatus comprising: at least one rotatable transfer assembly comprising at least two transfer heads, each transfer head structured to pick up a chip in the first position, and to position the chip in the at least second position through rotation of the at least one rotatable transfer assembly about an axis of rotation; a transfer assembly actuator for driving the rotatable transfer assembly together with the at least two transfer heads about the axis of rotation; and at least a first transfer head actuator structured to actuate at least one transfer head in a radial direction relative to the axis of rotation, the at least first transfer head actuator being mounted to the rotatable transfer assembly actuator and comprising an actuator element coupled to the at least one transfer head, the actuator element structured to be actuated in the direction of the axis of rotation relative to the rotatable transfer assembly actuator.

2. The apparatus according to claim 1, wherein the actuator element is coupled to the at least one transfer head by a connecting mechanism.

3. The apparatus according to claim 1, wherein the at least first transfer head actuator comprises an actuator component mounted to the rotatable transfer assembly actuator, and the actuator element is structured to be actuated in the direction of the axis of rotation relative to the actuator component.

4. The apparatus according to claim 1, wherein the at least first transfer head actuator further comprises at least one sensing device to sense a displacement of the actuator element in the direction of the axis of rotation relative to the rotatable transfer assembly actuator.

5. The apparatus according to claim 1, wherein the number of transfer heads is at least four.

6. The apparatus according to claim 1, wherein the number of transfer heads is at least six.

7. The apparatus according to claim 1, wherein the number of transfer heads is at least eight.

8. The apparatus according to claim 1, wherein the number of transfer heads is at least sixteen.

9. The apparatus according to claim 1, wherein the rotatable transfer assembly is rotated in one direction.

10. The apparatus according to claim 1, further comprising at least one further transfer head actuator mounted to the at least first transfer head actuator seen in the direction of the axis of rotation.

11. The apparatus according to claim 3, wherein the at least first transfer head actuator comprises a magnet-coil drive unit to actuate the actuator element in the direction of the axis of rotation relative to the rotatable transfer assembly actuator.

12. The apparatus according to claim 3, wherein the at least first transfer head actuator comprises a guiding element interconnecting the actuator element and the actuator component.

13. The apparatus according to claim 10, wherein the actuator component of the at least one further transfer head actuator is mounted to the actuator component of the previous transfer head actuator.

14. The apparatus according to claim 10, wherein the number of transfer head actuators is equal to the number of transfer heads.

15. The apparatus according to claim 10, wherein the number of transfer head actuators is half of the number of transfer heads.

16. The apparatus according to claim 10, wherein the number of transfer head actuators is one quarter of the number of transfer heads.

17. The apparatus according to claim 11, wherein the magnet-coil drive comprises multiple magnet elements mounted to the actuator element surrounding a coil element being mounted to the actuator component.

18. The apparatus according to claim 12, wherein the guiding element is selected from the group consisting of a membrane element, a spring element, a ball bearing, and an air bearing.

19. The apparatus according to claim 1, further comprising a wafer-positioning device structured to position a wafer with chips surfaces thereof extending in a first plane in the first position, and a lead frame positioning device to position a lead frame with a bond surface thereof extending in a second plane at the second position.

20. The apparatus according to claim 19, further comprising a chip surface inspection device extending in a third plane in a third position.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0025] The disclosure will now be discussed with reference to the drawings, which is show in the following figures:

[0026] FIG. 1 is a schematic depiction of an apparatus for transferring semiconductor circuits according to the state of the art.

[0027] FIG. 2 is a schematic depiction of an apparatus for transferring semiconductor circuits according to the disclosure.

[0028] FIGS. 3, 4 and 5 are further examples of apparatuses for transferring semiconductor circuits according to the disclosure.

[0029] FIGS. 6, 7 and 8 are detailed views of an example of a transfer head actuator according to the disclosure for implementation in an apparatus according to the disclosure.

DETAILED DESCRIPTION

[0030] For a proper understanding of the disclosure, in the detailed description below corresponding elements or parts of the disclosure will be denoted with identical reference numerals in the drawings.

[0031] FIG. 1 depicts a schematic example of an apparatus for transferring semiconductor circuits from a first position to at least a second position according to the state of the art.

[0032] As outlined in the introduction, semiconductor circuits are manufactured on and in a circular plane substrate, also referred to as a wafer, in a matrix having a plurality of rows and columns of such circuits. For separating the plurality of individual semiconductor circuits (hereinafter also to be referred to as “chips” or “dies”) from the wafer and arrange them individually on e.g. a carrier film for further handling and transportation, FIG. 1 depicts a schematic, yet known example of an apparatus for transferring chips from a first position, e.g. in which position the wafer with the matrix of semiconductor circuits is positioned, to at least a second position, e.g. in which position a carrier film with the individual semiconductor circuits are positioned.

[0033] The apparatus for transferring chips according to the state of the art is denoted with reference numeral 10. Throughout this specification, the individual semiconductor circuits or chips are denoted with reference numeral 1.

[0034] The apparatus 10 is composed of a transfer assembly 11 which is rotatable driven by means of a rotational motor or transfer assembly actuator 13. The transfer assembly actuator 13 is provided with one or more transfer assembly actuator bearings 13′ and is capable for rotating the transfer assembly 10 around an axis of rotation, which axis of rotation is denoted with reference numeral 11z in FIG. 1.

[0035] To the transfer assembly 11 are mounted preferably at least two transfer heads 12 (denoted with 12a-12b). Although the apparatus 10 can operate with one transfer head 12 mounted to the rotatable transfer assembly 11, it is preferred—for machine speed considerations—to have at least two transfer heads 12a-12b mounted to the transfer assembly 11. Each transfer head 12; 12a-12b is structured for picking up a semiconductor circuit or chip 1 in the first position, and for positioning the chip 1 in the at least second position through rotation of the rotatable transfer assembly 11 by means of the transfer assembly actuator 13 around the axis of rotation 11z.

[0036] Furthermore, as shown in FIG. 1, for a proper manipulation of the semiconductor circuit (chip) 1 in each first and second position, e.g. for picking the chip 1 up from a wafer positioned in the first position and for placing the chip 1 on a carrier film in the second position, each transfer head 12a-12b are likewise driven by a corresponding rotational transfer head motor 14 (14a-14b). Each rotational transfer head motor 14a and 14b is provided with a transfer head actuator bearing 14a′-14b′ allowing rotation around their individual axis of rotation 14a-z and 14b-z respectively. The axis of rotations 11z, 14a-z and 14b-z are not in a perfect concentric orientation with each other, thus creating mechanical accuracies for the transfer heads 12a-12b. In addition, each rotational transfer head motor 14a and 14b is provided with a connecting mechanism 15a and 15b actuating the transfer head 12a-12b in order to pick up a semiconductor circuit or chip 1 in the first position, and to position or place the chip 1 in the second position.

[0037] In this known configuration, rotational motors 14a-14b are implemented for each transfer head 12a-12b. However, in a more common configuration, two or even four rotatably driven transfer heads 12 can be connected to the same rotational transfer head actuator 14. Such configuration has some significant structural and operational drawbacks. A main drawback is machine speed loss, when rotatably driven transfer heads being connected to the same rotational transfer head motor, requiring their semiconductor circuit manipulations being performed in time-sequential order, instead of parallel.

[0038] Another drawback pertains to quality issues due to friction occurring from the rotation bearings 13′, 14a′ and 14b′ from the rotational actuators or motors used, hampering the position control of the transfer heads manipulations. As a solution, each transfer head 12 could be connected to an individual rotational transfer head actuator (motor) 14 in order to individual transfer head manipulation control, however this is not possible due to volume constraints of the overall apparatus construction.

[0039] FIG. 2 shows a schematic depiction of a first example of the disclosure, wherein the apparatus for transferring semiconductor circuits or chips 1 from a first position to at least a second position is denoted with reference numeral 100. The apparatus 100 comprises at least one rotatable transfer assembly 110. To the rotatable transfer assembly 110 at least two transfer heads 120 (120a-120b) are mounted. Similarly, each transfer head 120 (120a-120b) serves for picking up a chip 1 in the first position, and for positioning the chip 1 in the at least second position through radial displacement relative to the axis of rotation of 110z the rotatable transfer assembly 110. Rotation of the at least one rotatable transfer assembly 110 about its axis of rotation 110z ensures that each transfer head 120 (120a-120b) is displaced, through rotation, from the first position towards the at least second position.

[0040] Rotation of the transfer assembly 110 about its axis of rotation 110z is achieved with a transfer assembly actuator 130. According to the disclosure, the transfer assembly actuator 130 drives or rotates the rotatable transfer assembly 110 together with the at least two transfer heads 120 (120a-120b) about one, single axis of rotation 110z. As the complete construction of the apparatus 100 according to the disclosure and as depicted in FIG. 2 is capable of rotating around one axis of rotation 110z with the use of only one rotational motor or actuator 130, a simpler construction is obtained with a significantly reduced number of moving parts, such as only one bearing 130′. Also, mechanical inaccuracies due to eccentric rotational axes as in the known device shown in FIG. 1 are absent. Overall, this results in an apparatus 100 of limited volumetric dimensions with an improved accuracy as to the manipulation of the individual semiconductor circuits, and limited machine uptime loss and servicing time.

[0041] Furthermore, at least a first transfer head actuator 140 (140a) is used to actuate at least one corresponding transfer head 120 (120a) in a radial direction relative to the axis of rotation 110z, as depicted by the arrows R in FIG. 2. In this example, two transfer head actuators 140a-140b are used to actuate corresponding transfer heads 120a-120b, each with the assistance of a connecting mechanism 150a-150b, such as a bar-linkage mechanism or a cable mechanism. As shown, the transfer head actuators 140 (140a-140b) are mounted to the rotatable transfer assembly actuator 130.

[0042] Accordingly, the complete configuration of the apparatus 100 according to the disclosure consisting of the transfer assembly 110, the several transfer heads 120, the transfer assembly actuator 130 and the transfer head actuators 140 are mounted on one single bearing 130′ and being capable of rotating entirely about the single axis of rotation 110z. The advantages of such simpler construction are clear. Next to a significantly reduced number of moving parts, also the volumetric dimension of such configuration is limited, and next to an increase of machine speed, chips 1 can be manipulated faster and at higher accuracies. Also, its simpler construction reduces machine uptime loss and servicing time.

[0043] FIGS. 3-5 depict in more detail, examples of an apparatus according to the disclosure, denoted with reference numerals 100 (FIG. 3), 100′ (FIG. 4) and 100″ (FIG. 5). In FIG. 3 chip transfer apparatus 100 according to the disclosure is composed of the transfer assembly 110, the transfer assembly actuator 130, several, here eight, transfer heads 120a-120h, and one transfer head actuator 140a. Note, that the number of transfer heads 120 is arbitrary and depends on the type of application of the apparatus 100. Accordingly, one, two, four, eight, even sixteen transfer heads 120 (in such case indicated with reference numerals 120a-120p) can be mounted to the rotatably transfer assembly 110.

[0044] In this example, each transfer head 120a-120h is composed of a transfer head body 121a-121h mounted to the transfer assembly 110, and a transfer head arm 122a-122h, which is movable or hinged connected with the transfer head body 121a-121h.

[0045] Each transfer head arm 122a-122h carries a pick-up element 123a-123h capable to interact with a chip 1 in a known matter. For the sake of simplicity, in FIG. 3 only the reference numerals 121a-122a-123a of the associate transfer head 120a are shown, it is clear that in the configuration of eight transfer heads 120, the other seven transfer heads 120b-120h likewise comprise corresponding parts 121x-122x-123x (with x representing the relevant suffix letter b till h).

[0046] The transfer head arm 122a-122h is connected through a corresponding cable mechanism 150a-150h with the transfer head actuator 140a. Actuation of the cable mechanism 150a-150h (which will be discussed in detail later in this description) allows the transfer head arm 122a-122h to displace relative to the corresponding transfer head body 121a-121h, moving the pick-up element 123a-123h in a radial direction relative to the axis of rotation 110z, e.g. away from and towards the axis 110z, as shown with the arrows R in FIG. 2. The radial movement of the pick-up element 123a-123h allows for picking a chip 1 up from a wafer positioned in the first position and for placing the chip 1 on a carrier film in the second position.

[0047] Although all transfer heads 120a-120h can be linked with one and the same transfer head actuator 140a, e.g. as depicted in FIG. 3, further transfer head actuators 140b, 140c, 140d, etc. can be implemented. For example, as shown in FIG. 4, as the overall construction of the chip transfer apparatus 100′ according to the disclosure rotates around one single axis of rotation 110z, at least one further transfer head actuator 140b can be mounted to the first transfer head actuator 140a seen in the direction of the axis of rotation 110z. This allows for the advantageous upscale of the apparatus of the disclosure along its axis of rotation 110z also in terms of machine speed, by expanding the apparatus with additional transfer head actuators 140(a-d) for actuating one or more additional transfer heads 120a-120h mounted to the rotatable transfer assembly 110.

[0048] Such example is shown in FIG. 5, depicting a chip transfer apparatus 100″ according to the disclosure, which rotates around one single axis of rotation 110z, and is provided with four transfer head actuators 140a-140b-140c-140d, each mounted to a previous transfer head actuator seen in the direction of the axis of rotation 110z. The complete arrangement of multiple transfer head actuators is mounted to the rotatable transfer assembly 110.

[0049] As clearly shown in FIGS. 3-5, the several examples of an apparatus 100-100′-100″ according to the disclosure exhibit limited volumetric dimensions as only the elongated constructional dimension of the apparatus, seen in the direction of the axis of rotation, changes with the number of transfer head actuators 140 mounted to the rotatable transfer assembly 110. Accordingly, this design configuration has less mechanical inaccuracies, and less friction between its moving parts as the overall construction rotates about one single axis of rotation 110z, requiring on single bearing 130′ (FIG. 2).

[0050] This principle of adding additional transfer head actuators 140 along the axis of rotation 110z allows for each transfer head 120 to be actuated by its own transfer head actuator 140. On other hand, each transfer head actuator 140 can be structured to actuate two or more transfer heads 120, depending on the implementation of the chip transfer apparatus 100-100′-100″. For example, in FIG. 3, the eight transfer heads 120a-120h can be actuated together and simultaneously by the single transfer head actuator 140a, whereas in the apparatus 100′ of FIG. 4, the eight transfer heads 120a-120h can be grouped in two separate sets of four transfer heads each, e.g. one set consisting of transfer heads 120a, 120c, 120e and 120g and the other set consisting of transfer heads 120b, 120d, 120f and 120h, each set being actuated together and simultaneously by one of the two transfer head actuators 140a and 140b. Likewise, in the apparatus 100″ of FIG. 5, the eight transfer heads 120a-120h can be grouped in four separate sets of two transfer heads each, e.g. one set consisting of transfer heads 120a and 120e, a second set consisting of transfer heads 120b and 120f, a third set consisting of transfer heads 120c and 120g, and the fourth set consisting of transfer heads 120d and 120h. Similarly, each set is being actuated together and simultaneously by one of the four transfer head actuators 140a-140d, all actuation/manipulation taking placing through the respective cable mechanisms 150a-150h.

[0051] As each transfer head 120 can be actuated by its own transfer head actuator 140 operational flexibility and accuracy per transfer head can be significantly improved, as such 1-on-1 configuration allows accuracy corrections per transfer head 120/semiconductor circuit 1. Alternatively, two (or more) transfer heads can be actuated by one transfer head actuator allowing parallel manipulations of semiconductor chips.

[0052] FIGS. 6-8 show in more detail the functionality of a transfer head actuator 140. In the FIGS. 6-8 the transfer head actuator is denoted with reference numeral 140a. However, if more than one transfer head actuator 140 is used as depicted for example in FIGS. 4 and 5, subsequent letter suffixes are applied for the first and any further transfer head actuator 140. Accordingly, as stated above, in an example each transfer head 120x can be actuated by its own transfer head actuator 140x (with x representing the relevant suffix letter a till h or even more such as a till p). The transfer head actuator 140 (a-h) can have a more or less cylindrical configuration, having a reduced impact mass, and balanced inertia during rotation about the axis of rotation 110z. Each transfer head actuator 140 (a-h) has an actuator element 142 (a-h), which is coupled to at least one transfer head 120 (a-h) through a corresponding connecting mechanism 150 (a-h). The actuator element 142 (a-h) is structured to be actuated in the direction of the axis of rotation 110z relative to the rotatable transfer assembly actuator 130. With the movement of the actuated actuator element 142 (a-h) in the direction of the axis of rotation 110z relative to the rotatable transfer assembly actuator 130 the problem of mechanical inaccuracies in the known applications is solved.

[0053] In particular, the use of a connecting mechanism 150 (a-h), such as a bar-linkage mechanism or a cable mechanism, interconnecting the actuator element 142 (a-h) with at least one transfer head 120 (a-h) provides a sturdy and reliable actuation mechanism due to the absence of any friction and mechanical play. This actuation mechanism thus improves the mechanical accuracy of the manipulation of the semiconductor circuits 1.

[0054] As further shown in FIG. 6, reference numeral 141 (a-h) denotes an actuator component as a further part of the associated transfer head actuator 140 (a-h). The actuator component 141 (a-h) is fixedly mounted to the rotatable transfer assembly actuator 130. In a non-limiting example, the actuator component 141 (a-h) can be formed as a ring-shaped base element 141-1 (a-h) provided with several extension parts 141-2 (a-h) evenly distributed along the circumference of ring shaped base element 141-1 (a-h) and extending in the direction of the axis of rotation 110z. The extension parts 141-2 (a-h) are to be mounted in a fixed manner to the rotatable transfer assembly actuator 130.

[0055] The actuator element 142 (a-h) is also structured as a ring-shaped element having several openings 142-1 (a-h) also evenly distributed along its circumference. Each extension parts 141-2 (a-h) is accommodated in corresponding openings 142-1 (a-h), allowing a contactless movement of the actuator element 142 (a-h) in the direction of the axis of rotation 110z relative to the actuator component 141 (a-h).

[0056] Similarly, when looking at FIGS. 4 and 5 showing multiple transfer head actuators 140a-140d mounted in line with each other along the axis of rotation 110z, the actuator component 141b-141d of at least one further transfer head actuator 140b-140d is mounted to the actuator component 141a-141c of the previous transfer head actuator 140a-140c thus creating one rigid construction further increasing mechanical accuracy with limited moving parts, hence reduced friction.

[0057] In an example shown in FIGS. 7 and 8, each transfer head actuator 140 (a-h) comprises a magnet-coil drive unit 148 (a-h) for actuating the actuator element 142 (a-h) in the direction of the axis of rotation 110z relative to the rotatable transfer assembly actuator 130 (and the actuator component 141 (a-h)). Such contact less actuating principle ensures proper mechanical accuracy and instantaneous response times, further increasing overall machine speed.

[0058] In particular, in order to further increase instantaneous response times and machine speed, the magnet-coil drive 148 (a-h) comprises multiple magnet elements 144 (a-h) mounted at the inner circumference of the ring-shaped actuator element 142 (a-h) surrounding a coil element 145 (a-h) being mounted to the actuator component 141 (a-h).

[0059] In an alternative embodiment the multiple magnet elements 144 (a-h) are mounted to the actuator component 141 (a-h), whereas the coil element 145 (a-h) is mounted to the actuator element 142 (a-h).

[0060] To ascertain mechanical accuracy and instantaneous response times, when displacing the actuator element 142 (a-h) relative to the actuator component 141 (a-h) in the direction of the axis of rotation 110z, each transfer head actuator 140 (a-h) comprises a guiding element 143 (a-h) interconnecting the actuator element 142 (a-h) and the actuator component 141 (a-h). The guiding element 143 (a-h) can be chosen from the group not limited consisting of a membrane element, a spring element, a ball bearing, an air bearing, etc. In the depicted example of FIG. 8, the guiding element 141 (a-h) is formed as a disc shaped spring element having first mounting points 143-1 (a-h) for mounting/interconnecting with an extension part 141-2 (a-h) of the actuator component 141 (a-h) and second mounting points 143-2 (a-h) for mounting/interconnecting with the actuator element 142 (a-h). Such construction allows frictionless movements of the several parts without any mechanical play, thus ensuring operational reliability and accuracy.

[0061] Accordingly, with the actuator component 141 (a-h) being mounted to the transfer assembly actuator 130, the complete transfer head actuator 140 (a-h) rotates together with the transfer assembly actuator 130 (and the rotatable transfer assembly 110 with the several transfer heads 120) about the axis of rotation 110z, whereas the separate actuator component 141 (a-h) can be displaced—upon actuation of the magnet-coil drive 148 combined with the guiding element 143 (a-h)—in the direction of the axis of rotation 110z relative to the rotatable transfer assembly actuator 130 (and the rotatable transfer assembly 110 with the several transfer heads 120), in order to actuate via the associated cable mechanism 150 (a-h) the one or more transfer heads 120 (a-h) for semiconductor circuit manipulation.

[0062] Upon actuation of the magnet-coil drive 148 (a-h) the actuator element 142 (a-h) is displaced in the direction of the axis of rotation 110z relative to the actuator component 141, due to the electromagnetic forces generated. The actuator element 142 (a-h) is fixedly connected with one end of a corresponding cable mechanism 150 (a-h), whereas the other end of the cable mechanism 150 (a-h) is fixedly connected with a corresponding transfer head 120 (a-h), in particular with the corresponding transfer head arm 122a-122h. The displacement (back and forth along the axis of rotation) of the actuator element 142 (a-h) is transferred via the cable mechanism 150 (a-h) towards the transfer head arm 122 (a-h) and the associated pick-up element 123 (a-h) can be displaced in a radial direction relative to the axis of rotation 110z, as depicted by the arrows R in FIG. 2, for performing the respective picking up and placing of a chip 1.

[0063] In the FIGS. 3-5 and 8, reference numeral 146 (a-d) denotes a sensing device for sensing a displacement of the actuator element 142 (a-h) in the direction of the axis of rotation 110z relative to the actuator component 141 (a-h)/the rotatable transfer assembly actuator 130/the rotatable transfer assembly 110/the transfer heads 120 (a-h). Such sensing allows for an accurate actuating of the corresponding transfer head 120 in the radial direction relative to the axis of rotation 110z thus improving the accuracy of the semiconductor circuit manipulation. As the sensing device 146 (a-h) is mounted to the transfer head actuator 140 (a-h), which in turn is mounted to the rotatable transfer assembly actuator 130, the displacement change is sensed in the direction of the axis of rotation 110z irrespective of the rotation (direction and/or speed) of the overall construction 100-100′-100″.

[0064] For redundancy purposes, further improving mechanical accuracy, each transfer head 120 (a-h) can be provided with more than one sensing devices 146 (a-h).

[0065] In an example, the sensing device 146 can be embodied as a linear encoder sensing an encoding scale 147 (a-h) placed on a surface, e.g. the outer circumference of the disc-shaped actuator element 142 (a-h), which encoding scale encodes a position along the axis of rotation 110z. The linear encoder 146 is structured to scan the encoding scale 147 in order to convert the encoded position into an analog or digital signal.

LIST OF REFERENCE NUMERALS

[0066] 1 semiconductor circuit or chip

State of the Art

[0067] 10 apparatus for transferring chips [0068] 11 rotatable transfer assembly [0069] 11z axis of rotation of transfer assembly [0070] 12a-12b transfer heads [0071] 13 transfer assembly actuator [0072] 13′ transfer assembly actuator bearing [0073] 14a-14b rotatable transfer head actuator [0074] 14a′-14b′ transfer head actuator bearing [0075] 14a-z axis of rotation of transfer head actuator 14a [0076] 14b-z axis of rotation of transfer head actuator 14b [0077] 15a-15b connecting mechanism for transfer head 12a-12b

Disclosure

[0078] 100-100′-100″ apparatus for transferring chips (1st-2nd-3rd embodiment) [0079] 110 rotatable transfer assembly [0080] 110z axis of rotation of transfer assembly [0081] 120(a-h) transfer heads [0082] 121(a-h) transfer head body [0083] 122(a-h) transfer head arm [0084] 123(a-h) pick up element [0085] 130 transfer assembly actuator [0086] 130′ transfer assembly actuator bearing [0087] 140(a-h) transfer head actuator for transfer head 120a-120h [0088] 141(a-h) actuator component [0089] 142(a-h) actuator element [0090] 143(a-h) guiding element, e.g. a spring element, ball bearing, air bearing [0091] 144(a-h) magnet elements [0092] 145(a-h) coil element [0093] 146(a-h) sensing device (linear encoder) [0094] 147(a-h) encoding scale [0095] 148(a-h) magnet-coil drive unit [0096] 150(a-h) connecting mechanism for transfer head 120a-120h