MEMS MICRO-MIRROR ASSEMBLY

Abstract

A MEMS micro-mirror assembly (250, 300, 270, 400) comprising, a MEMS device (240) which comprises a MEMS die (241) and a magnet (231); a flexible PCB board (205) to which the MEMS device (240) is mechanically, and electrically, connected; wherein the flexible PCB board (205) further comprises a first extension portion (205b) which comprises a least one electrical contact (259a,b) which is useable to electrically connect the MEMS micro-mirror assembly (250, 300, 270, 400) to another electrical component). There is further provided a projection system comprising such a MEMS micro-mirror assembly (250, 300, 270, 400).

Claims

1-15. (canceled).

16. An apparatus comprising: a microelectromechanical system (MEMS) device; and a flexible printed circuit board (PCB) coupled to the MEMS device, the flexible PCB comprising at least one electrical contact operable to couple the MEMS device to another electrical component.

17. The apparatus of claim 16, the MEMS device mounted on the flexible PCB.

18. The apparatus of claim 16, the MEMS device comprising a coil, the at least one electrical contact electrically coupled to the coil.

19. The apparatus of claim 16, the MEMS device a mirror to oscillate about at least one axis.

20. The apparatus of claim 16, the flexible PCB comprising a first alignment mark, the first alignment mark comprising an indication of a location on the flexible PCB to attach the MEMS device.

21. The apparatus of claim 20, the flexible PCB comprising a second alignment mark, the second alignment mark comprising an indication of a location on the flexible PCB to attach a magnet, the magnet to provide a magnetic field to actuate the MEMS device.

22. The apparatus of claim 16, the flexible PCB comprising at least one reinforced area.

23. The apparatus of claim 22, the at least one reinforced area thicker than other areas of the flexible PCB.

24. The apparatus of claim 16, a length of at least one dimension of the flexible PCB board substantially the same as a length of at least one dimension of the MEMS device.

25. A system comprising: a light source to emit a light beam; a microelectromechanical system (MEMS) device comprising a micro-mirror to oscillate about at least one oscillation axis, the micro-mirror in an optical path of the light beam; and a flexible printed circuit board (PCB) coupled to the MEMS device, the flexible PCB comprising at least one electrical contact operable to couple the MEMS device to another electrical component.

26. The system of claim 25, the MEMS device mounted on the flexible PCB.

27. The system of claim 25, the MEMS device comprising a coil, the at least one electrical contact electrically coupled to the coil.

28. The system of claim 25, the flexible PCB comprising a first alignment mark, the first alignment mark comprising an indication of a location on the flexible PCB to attach the MEMS device.

29. The system of claim 28, the flexible PCB comprising a second alignment mark, the second alignment mark comprising an indication of a location on the flexible PCB to attach a magnet, the magnet to provide a magnetic field to actuate the MEMS device.

30. The system of claim 29, comprising the magnet.

31. The system of claim 25, the flexible PCB comprising at least one reinforced area.

32. The system of claim 31, the at least one reinforced area thicker than other areas of the flexible PCB.

33. The system of claim 25, a length of at least one dimension of the flexible PCB board substantially the same as a length of at least one dimension of the MEMS device.

34. The system of claim 25, comprising the another electrical component, the another electrical component a power source.

35. An apparatus comprising: a die comprising a microelectromechanical system (MEMS) device; and a flexible printed circuit board (PCB) coupled to the MEMS device, the flexible PCB comprising at least one electrical contact operable to couple the MEMS device to another electrical component.

36. The apparatus of claim 35, the die mounted to a first side of the flexible PCB.

37. The apparatus of claim 35, the at least one electrical contact comprising a first electrical contact and a second electrical contact, the second electrical contact redundant to the first electrical contact.

38. The apparatus of claim 35, comprising at least one wire bond to electrically couple the at least one electrical contact to the MEMS device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The invention will be better understood with the aid of the description of an embodiment given by way of example only and illustrated by the figures, in which:

[0044] FIGS. 1a and b provide perspective views of a MEMS micro-mirror assembly according to a first embodiment of the present invention; FIG. 1c provides a perspective view illustrating how the MEMS micro-mirror assembly of FIGS. 1a and 1b can be integrated into a projection device;

[0045] FIG. 2a provides a perspective view of a MEMS micro-mirror assembly according to a further embodiment of the present invention; FIG. 2b provides a perspective view illustrating how the MEMS micro-mirror of FIG. 2a can be integrated into a projection device;

[0046] FIG. 3 provides a perspective view of a MEMS micro-mirror assembly according to a further embodiment of the present invention;

[0047] FIG. 4 provides a perspective view of a MEMS micro-mirror assembly according to a further embodiment of the present invention;

[0048] FIG. 5a provides a plan view of a known MEMS micro-mirror device; FIG. 5b provides a cross sectional view of the MEMS micro-mirror device shown in FIG. 5a, taken along line A-A of FIG. 5a;

[0049] FIG. 6 provides a plan view of another known MEMS micro-mirror device.

DETAILED DESCRIPTION OF THE DRAWINGS

[0050] FIGS. 1a and 1b provide perspective views of a MEMS micro-mirror assembly 250 according to a first embodiment of the present invention. The MEMS micro-mirror assembly 250 comprises a MEMS device 240 mounted on a flexible PCB board 205.

[0051] The MEMS device 240 comprises a MEMS die 241 and a magnet 231. The MEMS device 240 is mechanically connected to the flexible PCB board 205 by means of glue which is provided between the magnet 231 and the flexible PCB board 205. It will be understood that the MEMS device 240 may be mechanically connected to the flexible PCB board 205 using any suitable means.

[0052] The MEMS die 241 may comprise any of the features of the MEMS die 10,90 of the MEMS devices 1,20 mentioned in the introduction. In this example, the MEMS die 241 comprises a first support frame 2, first and second torsional arms 3a,b, a moveable part 4, a MEMS micro-mirror 8, and a first actuation coil 5. In particular it should be noted that in this embodiment the moveable part 4 is magnetically actuated in the same manner as described for MEMS devices 1,20. The MEMS die 241 further comprises two electrical contacts 255a,b which can be used to electrically connect the MEMS device 240 to the flexible PCB board 205.

[0053] The flexible PCB board 205 comprises a portion 205a on which the MEMS device 240 is mounted and a first extension portion 205b.

[0054] The first extension portion 205b comprises two electrical contacts 253a,b. In this example a plurality of wire bonds 252 electrically connect each of the two electrical contacts 253a,b on the first extension portion 205b of flexible PCB board 205, to the two electrical contacts 255a,b provided on the MEMS device 240, so as to electrically connect the MEMS device 240 to the flexible PCB board 205. Specifically, in this example two wire bonds 252 electrically connect each electrical contact 253a,b on the first extension portion 205b of the flexible PCB board 205 to each electrical contact 255a,b on the MEMS device 240. It will be understood that any number of electrical contacts may be provided on the first extension portion 205b of the flexible PCB board 205 or MEMS device 240 and any number of wire bonds 252 may be used to establish electrical connection between said contacts; using two or more wire bonds 252 to establish electrical connection will provide a more robust electrical connection because if one of the wire bonds 252 should break, the MEMS device 240 will still be electrically connected to the flexible PCB board 205 by means of the other, unbroken, wire bonds 252.

[0055] As shown in FIG. 1b the MEMS micro-mirror assembly 250 may optionally comprise a protective material 261 which is arranged to form an enclosure 263 which encloses the plurality of wire bonds 252. The protective material 261 protects the wire bonds 252 from mechanical tearing and or shearing and from dust and humidity.

[0056] The first extension portion 205b of the flexible PCB board 205 further comprises two electrical contacts 259a,b which are useable to electrically connect the MEMS micro-mirror assembly 250 to another electrical component. For example, if the MEMS micro-mirror assembly 250 is to be integrated into a projection device, the electrical contacts 259a,b can be used to electrically connect the MEMS micro-mirror assembly 250 to the appropriate electrical contacts provided in the projection device so that the MEMS micro-mirror assembly 250 becomes integrated in the projection device. In this example the electrical contacts 259a,b further comprise metalized vias 258a,b. In this case, a metalized via can be used to electrically connect the top of the flexible PCB to the top of another PCB placed underneath, the electrical connect is then done by providing metal in the vias, that by capillarity will, connect all the pads of both PCB (the flex PCB and the other PCB).

[0057] The flexible PCB board 205 further comprises conductive lines 257a,b, which are arranged to electrically connect the electrical contacts 253a,b to the electrical contacts 259a,b.

[0058] FIG. 1c illustrates how the MEMS micro-mirror assembly 250 can be integrated into a projection device 803 (or any other device or system). The first extension portion 205b of the flexible PCB board 205 is flexed so that the electrical contacts 259a,b of the MEMS micro-mirror assembly 250 abut with, or attach to, electrical contacts 801a,b provided on a part 800 of the projection device 803. The MEMS micro-mirror assembly 250 is thus electrically connected to the electrical contacts 801a,b provided on the part 800 of the projection device and is integrated into the projection device 803.

[0059] Advantageously, since the PCB board 205 is a flexible PCB board 205 it may be flexed to allow the electrical contacts 259a,b to directly contact the electrical contacts 801a,b provided on the part 800 of the projection device 803. Thus, the use of a flexible PCB board 205 obviates the need for fragile wire bonds 252 to electrically connect the MEMS micro-mirror assembly 250 to the appropriate electrical contacts 801a,b provided in the projection device 803. Accordingly, the MEMS micro-mirror assembly 250 of the present invention enables easier and more robust integration into a projection device 803 (or other device or system).

[0060] Disadvantageously, flexing the first extension portion 205b of the flexible PCB board 205 may induce stress on the wire bonds 252. Accordingly, as the first extension portion 205b of the flexible PCB board 205 is flexed so that the electrical contacts 259a,b directly contact the electrical contacts 801a,b provided on the part 800 of the projection device 803, the wire bonds 252, which electrically connect the MEMS device 240 to the flexible PCB board 205, may break. FIG. 2a provides a perspective view of a MEMS micro-mirror assembly 300 according to another embodiment of the present invention, which addresses this problem.

[0061] The MEMS micro-mirror assembly 300 shown in FIG. 2a has many of the same features as the MEMS micro-mirror assembly 250 shown in FIG. 1 and like features are awarded the same reference numbers.

[0062] The first extension portion 205b comprises two electrical contacts 259a,b which are useable to electrically connect the MEMS micro-mirror assembly 300 to another electrical component.

[0063] The flexible PCB board 205 of the MEMS micro-mirror assembly 300 further comprises a second extension portion 205c which comprises two electrical contacts 253a,b to which the MEMS device 240 is electrically connected. Importantly, unlike the MEMS micro-mirror assembly 250 shown in FIGS. 1a and 1b, the two electrical contacts 253a,b on the flexible PCB board 205 to which the MEMS device 240 is electrically connect are not provided on the first extension portion 205b, rather they are provided on the second extension portion 205c.

[0064] A plurality of wire bonds 252 electrically connect the two electrical contacts 253a,b provided on the second extension portion 205c of the flexible PCB board 205 to the two electrical contacts 255a,b provided on the MEMS device 240, so as to electrically connect the MEMS device 240 to the flexible PCB board 205. In this example two wire bonds 252 electrically connect each electrical contact 253a,b on the second extension portion 205c of the flexible PCB board 205, to each electrical contact 255a,b on the MEMS device 240. However, it will be understood that any number of electrical contacts may be provided on the second extension portion 205c of the flexible PCB board 205 or MEMS device 240, and any number of wire bonds 252 may be used to establish electrical connection between said contacts. Using two or more wire bonds 252 will provide a more robust electrical connection because if one of the wire bonds 252 should break, the MEMS device 240 will still be electrically connected to the flexible PCB board 205 by means of the other, unbroken, wire bonds 252

[0065] Since, in the MEMS micro-mirror assembly 300, the MEMS device 240 is electrically connected to the flexible PCB board 205 by means of wire bonds 252 which connect to electrical contacts 253a,b provided on the second extension portion 205c of the flexible PCB board 205, little or no stress is induced in the wire bonds 252 when the first extension portion 205b of the flexible PCB board 205 is flexed. Accordingly, there is reduced risk of the wire bonds 252 breaking when the first extension portion 205b of the flexible PCB board 205 is flexed to integrate the MEMS micro-mirror assembly 300 into a projection device 803 (or other device or system).

[0066] FIG. 2b illustrates how the MEMS micro-mirror assembly 300 can be integrated into a projection device 803 (or any other device or system), the electrical contacts 259a,b being used to electrically connect the MEMS micro-mirror assembly 300 to the electrical contacts 801a,b provided on the part 800 of the projection device 803.

[0067] The first extension portion 205b of the flexible PCB board 205 is flexed so that the electrical contacts 259a,b of the MEMS micro-mirror assembly 300 abut with, or attach to, electrical contacts 801a,b provided on a part 800 of the projection device 803. As the first extension portion 205b of the flexible PCB board 205 is flexed while the second extension portion 205c remains undistorted.

[0068] Advantageously, since the PCB board 205 is a flexible PCB board 205 the first extension portion 205b may be flexed so that the electrical contacts 259a,b directly contact the electrical contacts 801a,b provided on the part 800 of the projection device 803, so as to integrate the MEMS micro-mirror assembly 300 into the projection device 803. Thus, the use of a flexible PCB board 205 obviates the need for fragile wire bonds 252 to electrically connect the MEMS micro-mirror assembly 300 to the electrical contacts 801a,b provided on the part 800 of the projection device 803. Accordingly, the MEMS micro-mirror assembly 300 enables easier and more robust integration into a projection device (or other device or system). Furthermore, as the MEMS device 240 is electrically connected to the flexible PCB board 205 by means of wire bonds 252 which connect to electrical contacts 253a,b provided on the second extension portion 205c of the flexible PCB board 205, little or no stress is induced in the wire bonds 252 when the first extension portion 205b of the flexible PCB board 205 is flexed so that the electrical contacts 259a,b directly contact the electrical contacts 801a,b provided on the part 800 of the projection device 803. Accordingly, there is a reduced risk of the wire bonds 252 breaking when the first extension portion 205b of the flexible PCB board 205 is flexed to integrate the MEMS micro-mirror assembly 300 into the projection device 803 (or other device or system).

[0069] FIG. 3 provides a perspective view of a MEMS micro-mirror assembly 400 according to a further embodiment of the present invention. The MEMS micro-mirror assembly 400 shown in FIG. 3 has many of the same features as the MEMS micro-mirror assembly 250 shown in FIG. 1 and like features are awarded the same reference numbers.

[0070] In the MEMS micro-mirror assembly 400 the flexible PCB board 205 is interposed between the MEMS die 241 and a magnet 231. The MEMS device 240 is mechanically connected to the flexible PCB board 205 by means of glue 430 which is provided between the magnet 231 and a first surface 402 of the flexible PCB board 205 and between the MEMS die 241 and a second, opposite, surface 403 of the flexible PCB board 205. It will be understood that any suitable glue maybe used.

[0071] Advantageously, in the MEMS micro-mirror assembly 400, shorter wire bonds 252 are required to electrically connect the MEMS device 240 to the flexible PCB board 205.

[0072] FIG. 4 provides a perspective view of a MEMS micro-mirror assembly 270 according to a further embodiment of the present invention. The MEMS micro-mirror assembly 270 has many of the same features as the MEMS micro-mirror assembly 250 shown in FIGS. 1a and 1b and like features are awarded the same reference numbers.

[0073] In this embodiment the MEMS device is not mounted on the flexible PCB board. In the MEMS micro-mirror assembly 270 the electrical contacts 253a,b on the flexible PCB board 205 are not connected to the electrical contacts 255a,b on the MEMS device 240 by means of wire bonds 252; rather the flexible PCB board 205 is arranged so that the electrical contacts 253a,b on the flexible PCB board 205 are connected directly to the electrical contacts 255a,b on the MEMS device 240. Specifically, the electrical contacts 255a,b on the flexible PCB board 205 are soldered to the electrical contacts 253a,b on the MEMS device 240 so as to electrically and mechanically connected the MEMS device 240 to the flexible PCB board 205. The electrical contacts 255a,b 253a,b may each comprise Anisotrope Conductive Film (ACF)

[0074] It will be understood that in each of the above described embodiments, each of the electrical contacts 253a,b on the flexible PCB board 205 may be configured so that they are accessible from opposite sides of the flexible PCB board 205 (e.g. accessible at the first and second surfaces 402,403 of the flexible PCB board 205); for example the electrical contacts 253a,b may be provided in through holes which are defined in flexible PCB board 205, so that the electrical contacts 253a,b are accessible from opposite sides of the flexible PCB board 205. Alternatively the electrical contacts 253a,b may be wrapped around a side edge of the flexible PCB board 205 so that a portion of each electrical contact 253a,b extends along the opposite surfaces of the flexible PCB board 205 (e.g along the first and second surfaces 402,403 of the PCB board). Advantageously, electrical contact with the electrical contacts 253a,b can then be achieved from opposing sides of the flexible PCB board 205 e.g. at both first and second surfaces 402,403 of the flexible PCB board 205.

[0075] It will also be understood that any of the electrical contacts provided on the flexible PCB board or on the MEMS device may each comprise Anisotrope Conductive Film (ACF).

[0076] It should be understood that the flexible PCB boards 205, in each of the above mentioned embodiments, may be further mounted on a metallic plate; the MEMS device may be maintained attached to the metallic plate by means of the magnetic attraction force between the magnet and the metal plate, thereby obviating the need for glue.

[0077] Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined in the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiment.