CROSS-REFERENCE TO RELATED APPLICATION

[0001] This appl ication claims the benefit of U.S. Provisional Application No. 62/840,039, filed Apri l 29, 2019, the content of which is i ncorporated herein by reference.

FIELD

[0002] The invention relates to li near motor systems, and more particularly, to improved linear motors i ncluding moving magnet assemblies.

BACKGROUND

[0003] Linear motors are well known i n the art and used in many different industries. For example, l inear motor systems are used in wire bonding machi nes to provide high speed l inear motion along various axes. For example, in certai n wi re bonding machi nes, linear motors are used to provide precise high speed motion along an x-axis and a y-axis of the machi ne. Exemplary patents i ll ustrating examples of linear motion systems incl ude: U .S. Patent No. 7,825,549 to Wang (titled "LIN EAR MOTOR WITH REDUCED COGGING"), U .S. Patent No. 4,912,746 to Oishi (titled "LINEAR DC BRUSHLESS MOTOR"), U .S. Patent No. 5,642,013 to Wavre (titled "PERMANENT- MAGNET SYNCHRONOUS MOTOR") and U.S. Patent No. 5,910,691 to Wavre (titled "PERMANENT-MAGNET LINEAR SYNCHRONOUS MOTOR") .

[0004] There is continuous interest i n providing improvements in the operation of linear motors, in areas such as noise reduction, vi bration reduction, speed, force, efficiency, accuracy, and cost of the motor. Thus, it would be desira ble to provide improved linear motors.

SUMMARY

[0005] According to an exemplary embodiment of the invention, a l inear motor is provided. The li near motor i ncludes a movi ng magnet assembly incl uding (i) a magnet track, (ii) a first pl urality of permanent magnets coupled to the magnet track, and (i ii) a second plurality of permanent magnets coupled to the magnet track and arranged below the first plurality of permanent magnets. The linear motor also includes a first coil assembly arranged above the moving magnet assembly. The first coil assembly includes a first plurality of teeth having first slots therebetween. The first coil assembly also includes a first plurality of coils at least partially disposed in at least a portion of the first slots. The linear motor also includes a second coil assembly arranged below the moving magnet assembly. The second coil assembly includes a second plurality of teeth having second slots therebetween. The second coil assembly includes a second plurality of coils at least partially disposed in at least a portion of the second slots.

[0006] According to another exemplary embodiment of the invention, a wire bonding system is provided. The wire bonding system includes a bond head assembly carrying a wire bonding tool and a linear motor system for driving the bond head assembly along a first horizontal axis. The linear motor system includes a moving magnet assembly having (i) a magnet track, (ii) a first plurality of permanent magnets coupled to the magnet track, and (iii) a second plurality of permanent magnets coupled to the magnet track and arranged below the first plurality of permanent magnets. The linear motor system also includes a first coil assembly arranged above the moving magnet assembly. The first coil assembly includes a first plurality of teeth having first slots therebetween. The first coil assembly also includes a first plurality of coils at least partially disposed in at least a portion of the first slots. The linear motor system also includes a second coil assembly arranged below the moving magnet assembly. The second coil assembly includes a second plurality of teeth having second slots therebetween. The second coil assembly includes a second plurality of coils at least partially disposed in at least a portion of the second slots.

[0007] Other machines (besides wire bonding machines) are contemplated within the scope of the invention, to include the inventive linear motors. Examples of such machines include die attach machines, flip chip bonding machines,

thermocompression bonding machines, pick and place machines, and other

semiconductor packaging machines.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The invention is best understood from the following detailed description when read in connection with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following figures:

[0009] FIG. 1A is a cross-sectional view of a linear motor in accordance with an exemplary embodiment of the invention;

[0010] FIG. IB is a combination side and cross-sectional view of the linear motor of FIG. 1A;

[0011] FIG. 1C is a detailed view of a portion of FIG. 1A;

[0012] FIG. 2A is a cross-sectional view of another linear motor in accordance with another exemplary embodiment of the invention;

[0013] FIG. 2B is a combination side and cross-sectional view of the linear motor of FIG. 2 A;

[0014] FIG. 3A is a cross-sectional view of yet another linear motor in accordance with another exemplary embodiment of the invention;

[0015] FIG. 3B is a combination side and cross-sectional view of the linear motor of FIG. 3 A;

[0016] FIG. 4A is a cross-sectional view of yet another linear motor in accordance with another exemplary embodiment of the invention;

[0017] FIG. 4B is a combination side and cross-sectional view of the linear motor of FIG. 4A;

[0018] FIG. 5A is a cross-sectional view of a moving magnet assembly in accordance with an exemplary embodiment of the invention;

[0019] FIG. 5B is a detailed view of a portion of FIG. 5A;

[0020] FIG. 5C is a perspective cross-sectional view of the moving magnet assembly of FIG. 5A;

[0021] FIG. 5D is a detailed view of a portion of FIG. 5C;

[0022] FIG. 5E is a top view of the moving magnet assembly of FIG. 5A; [0023] FIG. 6 is a cross-sectional view of another linear motor in accordance with an exemplary embodiment of the invention;

[0024] FIG. 7 is a cross-sectional view of yet another linear motor in accordance with an exemplary embodiment of the invention;

[0025] FIG. 8 is a cross-sectional block diagram of a wire bonding machine including the li near motor of FIG. 7 in accordance with an exemplary embodiment of the invention; and

[0026] FIGS. 9A-9C are various cross-sectional block diagram views of the wire bonding machi ne of FIG. 8 i n accordance with an exemplary embodiment of the invention.

DETAILED DESCRIPTION

[0027] As used herein, the terms "l inear motor", "l inear motor system", and "li near motion system" may be considered synonyms. For example, FIGS. 1A- 1C, 2A- 2B, 3A-3B, and 4A-4B i llustrate respective linear motors 100a, 100b, 100c, and lOOd. While FIG. 6 refers to a l inear motor system 600, and FIG. 7 refers to a linear motion system 700, each of these may also be considered a "linear motor" within the scope of the invention.

[0028] As used herein, the term "magnet track" is intended to refer to any of a number of structures in a linear motor carrying a plurality of permanent magnets arranged to magnetically i nteract with a coil assembly of the li near motor such that a desired li near motion of at least one of the magnet track and the coi l assembly is provided. As such, the magnet track is not intended to be l imited, for example, to any particular arrangement or spaci ng of the permanent magnets, nor is the magnet track intended to be l imited to any particular support structure for the permanent magnets.

[0029] FIG. 1A is a cross sectional view of l inear motor 100a . Linear motor 100a includes moving magnet assembly 102, first coil assembly 104a l, and second coi l assembly 104a2. As is understood by those skilled i n the art, certain components of linear motor 100a (e.g ., electrical connections, etc. ) have been omitted for si mpl icity. Moving magnet assembly 102 i ncludes (i) a magnet track 102a, (i i) a fi rst plural ity of permanent magnets 102b l, 102b2, . . ., 102b21, 102b22 coupled to magnet track 102a, and (i ii) a second plurality of permanent magnets 102cl, 102c2, . . ., 102c21, 102c22 coupled to magnet track 102a and arranged below the first plurality of permanent magnets 102b l, 102b2, . . 102b22. As shown in FIG. 1A, the permanent magnets are arranged in magnet pairs, one disposed directly above the other. For example, permanent magnet 102b l is positioned di rectly above permanent magnet 102cl, such that permanent magnets 102b l and 102cl form a "magnet pair".

According to exemplary aspects of the invention, magnetic attraction forces may exist between each magnet pai r.

[0030] Magnet track 102a (and any of the other magnet tracks described in this patent application) may be formed from a non-magnetic material (e.g., a material including al uminum such as al uminum or an aluminum alloy) . Other exemplary nonmagnetic materials i nclude carbon fiber, beryl lium, as well as many others.

[0031] Each of the first plurality of permanent magnets 102bl, 102b2, . . ., 102b22, and each of the second plurality of permanent magnets 102cl, 102c2, . . . , 102c22, are connected (di rectly or indirectly) to magnet track 102a using any of a number of techniques such as an adhesive, fasteners, etc. Magnet track 102a includes a coupling portion 102d for connecti ng to another structure to be moved along the desired axis by linear motor 100a. For example, coupli ng portion 102d may be connected to a y-axis sl ide of a wi re bondi ng machine for moving a bond head assembly along the y-axis (e.g ., see FIG. 8) .

[0032] Linear motor 100a also includes a fi rst coi l assembly 104a l (which may also be referred to as stator 104a 1) arranged above moving magnet assembly 102.

First coil assembly 104a l i ncludes a fi rst plural ity of teeth having first slots 105a l therebetween. The first plurality of teeth i nclude end teeth 104a la at each end of first coil assembly 104a l, and a plural ity of teeth 104a lb disposed between the two end teeth 104a la. First coil assembly also incl udes coils 106 at least partially disposed in at least a portion of the fi rst slots 105a l . As shown i n FIG. 1A (and more clearly shown in FIG. IB), each slot 105a l (except the end slots adjacent end teeth 104a la, which has received a portion of only one coil 106) has received a portion of two adjacent coils 106. Linear motor 100a also incl udes a second coi l assembly 104a2 (which may also be referred to as stator 104a2) arranged below moving magnet assembly 102. Second coil assembly 104a2 includes a second plurality of teeth having second slots 105a2 therebetween. The second plurality of teeth include end teeth 104a2a at each end of second coil assembly 104a2, and a pl ural ity of teeth 104a2b disposed between the two end teeth 104a2a . Second coil assembly 104a2 also includes coi ls 106 at least partially disposed in at least a portion of the second slots 105a2. As shown in FIG. 1A (and more clearly shown in FIG. IB), each slot 105a2 (except the end slots adjacent end teeth 104a2a, which has received a portion of only one coil 106) has received a portion of two adjacent coils 106.

[0033] Each of first coil assembly 104al and second coil assembly 104a2 may include a plurality of laminations stacked together as is known to those skilled in the art. Thus, the stacked laminations define the respective first plurality of teeth 104a la, 104alb and the second plurality of teeth 104a2a, 104a2b.

[0034] As shown in FIG. 1C, an exposed surface of each of the first plurality of permanent magnets 102bl, 102b2, . . ., 102b22 is positioned adjacent first coil assembly 104a 1 at a first distance d l, and an exposed surface of each of the second plurality of permanent magnets 102cl, 102c2, . . ., 102c22 is positioned adjacent the second coil assembly 104a2 at a second distance d2. The first distance d l is substantially the same as the second distance d2.

[0035] To the extent possible, the features described above with respect to FIGS. 1A-1C are applicable to the additional embodiments of the invention described herein (and other embodiments within the scope of the invention). Thus, in connection with the remaining embodiments, certain details are omitted for simplicity, and certain reference numerals are duplicated across the various illustrated embodiments of the invention.

[0036] FIGS. 1A-1C illustrate first coil assembly 104al and second coil assembly 104a2, having teeth 104ala, 104a lb, 104a2a, and 104a2b. End teeth 104ala, 104a2a have a shape as shown in U.S. Patent No. 7,825,549. Teeth 104a lb, 104a2b have a "T" shaped configuration where the end of each tooth is wider than the body of the respective tooth (see FIG. 1A, where gap 104a lc, and gap 104a2c, between adjacent teeth are smaller at the end because of the "T" shape). Of course, these teeth designs are exemplary in nature, and the invention is not limited to such configurations.

[0037] FIGS. 2A-2B illustrate linear motor 100b which is very similar to linear motor 100a described above with respect to FIGS. 1A-1B. Linear motor 100b includes a magnet assembly 102 which is the same as magnet assembly 102 from FIGS. 1A-1B. Linear motor also includes first coil assembly 104bl (including teeth 104bla, 104blb) and second coil assembly 104b2 (including teeth 104b2a, 104b2b), which are very similar to first coil assembly 104a l and second coil assembly 104a2 from FIGS. 1A-1B. One difference is that in FIGS. 2A-2B teeth 104blb, 104b2b do not have the "T" shaped configuration described above. Rather, teeth 104blb, 104b2b have the same (or substantially the same) width along their entire length, which makes positioning of coils 106 relatively simple.

[0038] FIGS. 3A-3B ill ustrate linear motor 100c which is very similar to linear motor 100a descri bed above with respect to FIGS. 1A-1 B. Li near motor 100c includes a magnet assembly 102 which is the same as magnet assembly 102 from FIGS. 1A- 1B. Linear motor also includes fi rst coi l assembly 104cl (including teeth 104cla, 104clb) and second coi l assembly 104c2 (incl udi ng teeth 104c2a, 104c2b), which are very similar to first coil assembly 104a l and second coil assembly 104a2 from FIGS. 1A- 1B. However, in FIGS. 3A-3B, only one coil 106 is provided in each slot (See FIG. 3B for clarity) . Thus, in the example shown i n FIGS. 3A-3B, six coils 106 are provided, whereas in FIGS. 1A- 1B twelve coils 106 are provided.

[0039] FIGS. 4A-4B ill ustrate linear motor lOOd which is very simi lar to l inear motor 100a descri bed above with respect to FIGS. 1A-1 B. Li near motor lOOd i ncludes a magnet assembly 102 which is the same as magnet assembly 102 from FIGS. 1A-1B. Linear motor lOOd also includes fi rst coi l assembly 104d l (i ncluding teeth 104d la, 104d lb) and second coil assembly 104d2 (including teeth 104d2a, 104d2b), which are very si milar to fi rst coi l assembly 104a l and second coil assembly 104a2 from FIGS. 1A-1B. However, like FIGS. 3A-3B, in FIGS. 4A-4B, only one coil 106 is provided i n each slot (See FIG. 4B for clarity) . Thus, in the example shown in FIGS. 4A-4B, six coils 106 are provided, whereas in FIGS. 1A- 1B twelve coils 106 are provided . Another difference is that in FIGS. 4A-4B teeth 104d lb, 104d2b do not have the "T" shaped configuration descri bed above with respect to FIGS. 1A- 1B. Rather, teeth 104d lb, 104d2b have the same (or substantial ly the same) width along thei r enti re length, which makes positioning of coils 106 relatively si mple.

[0040] FIGS. 5A-5E i llustrate various details of magnet assembly 102. FIG. 5A illustrates a cross-sectional view of magnet assembly 102 shown in FIGS. 1A- 1C, 2A- 2B, 3A-3B, and 4A-4B, along with the direction of motion (along the y-axis in the examples shown in the appl ication) . FIG. 5B is a detai led view of a portion of FIG. 5A, which clearly il lustrates certain features of magnet assembly. Specifically, FIG. 5B illustrates that magnet track 102a defi nes a pl ural ity of tab portions 102e. As shown in FIG. 5B, each of the first plurality of permanent magnets 102b l, 102b2, . . ., 102b22 and the second pl urality of permanent magnets 102cl, 102c2, . . ., 102c22 includes a stepped portion "ST" configured to mate with corresponding ones of the pl urality of tab portions 102e. FIGS. 5C-5D provide additional perspective cross sectional views of magnet assembly 102. FIG. 5E ill ustrates a top view of magnet assembly 102 (not a cross sectional view, as i n FIGS. 5A-5D) . In FIG. 5E, connection portions 102f of magnet assembly 102 are visible. Connection portions 102f are used to engage some type of bearing assembly (see bearings 606, and bearing block 604, shown in FIG. 6) to assist in the motion of moving magnet assembly 102. For example, the beari ng assembly could be a li near bearing block engaged with a li near bearing rai l . Of course, other types of beari ng assemblies are contemplated .

[0041] According to certain aspects of the invention, the design of the substrate (i .e., the magnet track) carrying the plural ity of permanent magnets (i ncluding both the first and second plural ity of permanent magnets) of the movi ng magnet assembly 102 is i mportant. It may be particularly beneficial that the magnets are carried without a cover or skin between the magnets and the respective stator (i .e., between the fi rst plura lity of permanent magnets and the fi rst coi l assembly, and between the second plura lity of permanent magnets and the second coil assembly) . This lack of an inclusion of a cover or ski n substantially reduces the electrical and mechanical gap between the magnets and the respective stator, and further reduces unnecessary mass in the linear motor. Further sti ll, such a substrate (i .e. , the magnet track) does not appreciably interfere with the magnetic flux path.

[0042] Further still, the design of movi ng magnet assembly 102 (i ncluding symmetric magnet pairs disposed one above the other), along with the dual stator design (including the first coil assembly and the second coil assembly) desirably creates a substantial ly equal force constant for each stator, and creates a substantially equal and opposite magnetic attraction force to each stator. This results in a mini mal (substantially net zero) load on the moving magnet assembly 102 and the associated beari ngs.

[0043] FIG. 6 i llustrates a linear motor system 600 with additional components. While li near motor system 600 i ncludes linear motor 100b from FIGS. 2A-2B, it is understood that any other l inear motor withi n the scope of the invention (e.g ., linear motor 100a, 100c, lOOd, or any other li near motor withi n the scope of the i nvention) may be i ncluded in linear motor system 600. Linear motor system 600 i ncludes housing portions 602a, 602b, and 602c. Collectively, housing portions 602a, 602b, and 602c are part of a common housing, where the common housing couples (either directly or indirectly) first coil assembly 104b l with second coil assembly 104b2 to provide a combi ned coil assembly. For example, first coil assembly 104bl and second coil assembly 104b2 may be secured i n the common housing using adhesive, fasteners, a combi nation of both, among other techniques. It is understood that a common housing for first coil assembly 104bl and second coil assembly 104b2 may take any desired configuration (e.g., a single piece, or multiple different pieces, of material and not three distinct housing portions as shown) . FIG. 6 also i llustrates bearings 606 supported by beari ng blocks 604 (where bearing blocks 604 may be considered to be part of the combined coil assembly). Through operation of linear motor system 600, moving magnet assembly 102 moves along the Y axis, while riding along bearings 606.

[0044] FIG. 7 i llustrates linear motion system 700 which includes linear motor system 600 from FIG. 6. While FIG. 7 ill ustrates linear motor system 600 i ncluding linear motor 100b from FIGS. 2A-2B, it is understood that any other l inear motor withi n the scope of the i nvention (e.g., li near motor 100a, 100c, lOOd, or any other linear motor within the scope of the invention) may be included in linear motor system 600. Duri ng operation of linear motion system 700, motion of the moving magnet assembly 102 along a horizontal axis (the Y axis shown i n FIG. 7) results in some resultant motion of the combined coil assembly (includi ng housing portions 602a, 602b, and 602c, as well as first coil assembly 104b l and second coil assembly 104b2) along the same horizontal axis. In the block diagram view of FIG. 7, this motion is provided for via bearings 702e. More specifically, li near motion system 700 includes base structure 702a, side block portions 702b, dampers 702c, springs 702d, and bearings 702e.

Bearings 702e are supported by base structure 702a. Springs 702d and dampers 702c are provided between the common housing (i ncluding housing portions 602a, 602b, and 602c, and the combined coil assembly) and side block portions 702b. Springs 702d assist in re-centeri ng the common housing (including the combined coil assembly of fi rst coi l assembly 104b l and second coil assembly 104b2) after motion of moving magnet assembly 102. Dampers 702c assist i n controll ing stabil ity of li near motion system 700 i n connection with motion of moving magnet assembly 102.

[0045] FIG. 7 also illustrates a position encoder system 702f for providing position information related to the combi ned coil assembly (includi ng fi rst coi l assembly 104bl and second coi l assembly 104b2) . Position encoder system 702f (includi ng elements 702fl and 702f2) may be any of a number of types of position encoder systems (e.g ., an optical encoder system, a magnetic encoder system, etc.) . Position encoder system 702f, shown in FIG. 7, may be considered of varyi ng type of position encoder system. For example, in an optical encoder system, a scale portion 702fl is provided coupled (either directly or indirectly) to the combi ned coil assembly, and an optical portion 702f2 is provided for imaging the scale portion. In such an example, optical portion 702f2 is coupled (either di rectly or indirectly) to another portion of linear motion 700 (e.g ., base portion 702a) that does not move with the combi ned coil assembly. In another example, elements 702fl and 702f2 may be portions of a magnetic encoder system.

[0046] In any event, inclusion of position encoder system 702f may be particularly beneficial if linear motor 100b is a three phase motor, where the position information provided by position encoder system 702f is used to control a commutation angle of linear motor 100b.

[0047] FIG. 8 i llustrates wire bonding system 800 i ncluding linear motion system 700 from FIG. 7. Wi re bondi ng system 800 also i ncludes bond head assembly 804 (carryi ng wire bonding tool 806), y-axis sl ide 802, beari ng block 810 (for supporting y- axis slide 802), and beari ngs 812. As wil l be appreciated by those ski lled i n the art, y- axis slide 802 may incorporate bearing block 810 (i .e., y-axis sl ide 802 would be carried on bearings 812 di rectly) . Motion of moving magnet assembly 102 along the y- axis results in correspondi ng motion of bond head assembly 804. Wire bonding system 800 also includes linear motion system 700' which carries y-axis slide 802 and beari ng block 810 along bearings 812. While shown as a block in FIG. 8, it is understood that linear motion system 700' is a li near motion system withi n the scope of the invention, such as a dupl icate of linear motion system 700. Li near motion system 700' provides linear motion of bond head assembly 804 along the x-axis of wire bonding system 800 (where the x-axis is substantial ly perpendicular to the y-axis) . Wi re bondi ng system 800 also includes a decoupling element 808 for decoupling operation of linear motion system 700 from operation of linear motion system 700'. Thus, operation of li near motion system 700 is decoupled from operation of linear motion system 700'.

[0048] FIGS. 9A-9C i llustrate operation of li near motor 100b along the y-axis of wi re bondi ng machine 800. In FIG. 9A, wire bonding tool 806 (carried by bond head assembly 804) is moved to the right ("FORWARD") in the drawing, resulting i n a reverse motion of the common housing (shown as compression of the left spring element 702d) . In FIG. 9B, wire bonding tool 806 is shown in its centered position. In FIG. 9C, wire bondi ng tool 806 (carried by bond head assembly 804) is moved to the left ("BACKWARD") i n the drawing, resulting in a reverse motion of the common housing (shown as compression of the right spring element 702d) .

[0049] The linear motors of the i nvention may find application in a number of technical fields. One exemplary area of use is with a wire bonding machi ne, wherein a linear motor accordi ng to the present i nvention may be used to provide linear motion along the x-axis or the y-axis, or both. More specifically, for example, such linear motors may be used to provide linear motion to a bond head assembly of a wi re bonding machi ne along the x-axis of the bond head assembly, the y-axis of the bond head assembly, or both. Of course, the l inear motors of the invention wi ll fi nd use in any of a number of other technical fields.

[0050] Although certai n embodiments (see FIG. 8) of the invention show the y- axis slide 802 carried by the x-axis linear motion system 700', it is understood that this is exemplary in nature. In a different embodiment within the scope of the invention, an x-axis slide may be carried by a y-axis linear motion system.

[0051] Although aspects of the invention are ill ustrated with respect to li near motors including 6 coils and 12 coi ls, the i nvention is not l imited thereto. These are examples, and any number of coils may be provided, as desired, within the scope of the invention.

[0052] Although the invention is i llustrated with respect to exemplary tooth designs (including end teeth, and i ntermediate teeth between the end teeth), it is understood that al l tooth designs are exemplary in nature - and any other tooth design may be i ncorporated, as desired, within the scope of the i nvention.

[0053] Although the invention is i llustrated and described herei n with reference to specific embodiments, the invention is not intended to be l imited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the i nvention.