MEMS package with actuator stator providing electrical connection points

Abstract

A MEMS device is provided which includes an actuator stator providing an electrical connection point. The MEMS device includes a power distribution board and an actuator stator located above it. The actuator stator has a bottom and an external frame extending upward from the bottom. The MEMS device includes a stator pad located above the power distribution board on the external frame. The MEMS device also includes an actuator rotor suspended within the external frame above the bottom, on which a sensor is mounted. A wire bond interconnect electrically couples the sensor to the stator pad. In some embodiments, the external frame includes vias extending through its interior, which electrically connect the stator pad to the power distribution board, thereby enabling an electrical connection between the sensor and the power distribution board. In some embodiments, a second wire bond interconnect electrically couples the stator pad to the board.

Description

Technical Field

[0001] The present disclosure relates to microelectromechanical system (MEMS) devices and related MEMS packages where the static structure (e.g., stator) of a MEMS actuator provides electrical connection points to a sensor.

Background Art

[0002] MEMS devices are generally known as tiny devices that incorporate both electronic and movable components. These devices typically include one or more components (e.g., sensors) that interact with the surrounding environment. Various environmental factors such as temperature changes and vibrations can affect the performance of the sensors.

Summary of the Invention

[0003] According to one embodiment, a MEMS device includes a power distribution substrate and an actuator stator located above the power distribution substrate and having an outer frame that extends upward from the bottom. The MEMS device further includes a stator pad disposed above the power distribution substrate on the outer frame, and an actuator rotor suspended within the outer frame above the bottom of the actuator stator. The MEMS device further includes a sensor disposed on the actuator rotor and a wire bond interconnect that electrically couples the sensor and the stator pad. The outer frame includes vias that extend through its interior, and the vias electrically connect the stator pad to the power distribution substrate, thereby enabling an electrical connection between the sensor and the power distribution substrate.

[0004] In one embodiment, the MEMS device includes an area array substrate; an actuator stator located above the area array substrate and having a bottom and an external frame extending upward from the bottom; a stator pad positioned above the area array substrate on the external frame; an actuator rotor suspended within the external frame above the bottom of the actuator stator; a sensor positioned on the actuator rotor; a first wire bond interconnect positioned on the sensor and the stator pad to electrically connect them; and a second wire bond interconnect positioned on the stator pad and the area array substrate to electrically connect them and enable an electrical connection between the sensor and the area array substrate.

[0005] In one embodiment, the MEMS device includes a power distribution board, an actuator stator located above the power distribution board and having a bottom, an actuator rotor suspended above the bottom of the actuator stator and configured to move perpendicular to the actuator stator, a stator pad disposed on the actuator stator and electrically isolated from the actuator stator, a sensor attached to the actuator rotor, and at least one wire bond interconnect configured to electrically couple the sensor to the power distribution board via the stator pad. [Brief explanation of the drawing]

[0006] [Figure 1] This is a cross-sectional view of a MEMS device and an associated MEMS package according to one embodiment of the present disclosure. [Figure 2] This is a cross-sectional view of a MEMS device and an associated MEMS package according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0007] Embodiments of the Disclosure are described herein. However, it should be understood that the embodiments disclosed are merely examples, and other embodiments may take various alternative forms. The figures are not necessarily to scale, and some features may be exaggerated or minimized to illustrate details of particular components. Accordingly, certain structural and functional details disclosed herein should not be construed as limiting, but merely as representative grounds for teaching those skilled in the art to adopt the embodiments in various ways. As those skilled in the art will understand, various features illustrated and described with reference to any one of the figures may be combined with features illustrated in one or more other figures to produce embodiments not expressly illustrated or described. Combinations of illustrated features provide representative embodiments for typical uses. However, various combinations and modifications of features consistent with the teachings of the Disclosure may be desired for particular uses or implementations.

[0008] As used herein, “a,” “an,” and “the” refer to both singular and plural referents unless the context clearly indicates otherwise. For example, “a stator” refers to one or more stators.

[0009] MEMS devices are generally known to incorporate both electronic and moving parts. These devices typically include one or more components (e.g., sensors) that interact with the surrounding environment. Various environmental factors, such as temperature changes and vibrations, can affect the performance of sensors.

[0010] Certain prior art systems include a MEMS device with an image sensor (e.g., a camera) mounted on a MEMS actuator that can move the focal plane of the image sensor along the optical axis to adjust the focal position. The image sensor is positioned either below or above the circuit board and wire-bonded to the circuit board. However, in such systems, if the MEMS device is used in environments with rapid movement, such as in automobiles, the relatively long wire bond may be susceptible to movement and short circuits. Furthermore, this approach consumes areas on both the top and bottom surfaces of the circuit board, especially when the image sensor is positioned below the circuit board. The shape of the wire bond is taller than typical solutions to relieve stress on the bond, but this may increase the risk of short circuits between bonds during operation and manufacturing. This makes miniaturization difficult.

[0011] Accordingly, according to various embodiments disclosed herein, the MEMS device is packaged in such a manner that it utilizes a stator for electrical connection to a circuit board (or other electrical distribution layer or substrate). In embodiments, the actuator has a rotor and a stator and is provided within the MEMS device to move a MEMS-mounted sensor. The MEMS-mounted sensor is mounted on the rotor and electrically connected to the stator via a wire-bond interconnect. This allows for further miniaturization of the MEMS device and its package while enabling the free movement of the sensor and actuator.

[0012] Figure 1 shows a cross-sectional view of a MEMS device 10 according to one embodiment of the present disclosure. The reference to MEMS “device” is intended to refer to a packaged device including a MEMS-mounted sensor (more commonly referred to herein as a sensor), a circuit with which the MEMS-mounted sensor communicates electrically, and the package itself. Thus, the MEMS device 10 may also be referred to as a MEMS system or microsystem.

[0013] The MEMS device 10 includes a sensor 12 housed within a package 14, also called a MEMS package or encapsulation. The sensor 12 may be a single sensor or a sensor array. The sensor 12 may be an image sensor such as a camera, lidar sensor, radar sensor, or similar, and may include an array of sensor cells (or pixels) for sensing light signals (e.g., a one-dimensional or two-dimensional array). For example, the sensor 12 may include a photodetector, such as a photodiode, which can generate a voltage signal or current signal corresponding to the intensity of the light signal illuminating the pixel. For example, each pixel may convert the light signal incident on the pixel into a current, or use a capacitor to integrate the current and generate a voltage signal. The current signal or voltage signal may be converted into digital pixel data by an analog-to-digital converter. Thus, each pixel may generate digital pixel data representing the intensity of light received by the pixel. The pixel data from pixels in the sensor array may represent an image of an object or scene. In certain embodiments, the sensor 12 includes a charge-coupled device (CCD) image sensor comprising a photodetector and an array of metal-oxide-semiconductor (MOS) capacitors, or a complementary metal-oxide-semiconductor (CMOS) or active pixel sensor (APS) image sensor comprising an array of photodiodes and MOS field-effect transistor (MOSFET) amplifiers.

[0014] Although sensor 12 is described above as an image sensor, this disclosure is not limited to such embodiments. For example, the sensor may be, or may include, a temperature sensor, a pressure sensor, a gyroscope, an accelerometer, or other such sensors commonly found in MEMS devices. Unless otherwise stated, the sensors of this disclosure are not limited to any particular type of sensor.

[0015] Furthermore, the MEMS device 10 may include a processor (e.g., a microprocessor) bonded to or integrated with the sensor 12 and configured to process at least partially the data received from the sensor 12 (e.g., pixel data in the above embodiment). In other embodiments, the processing of the sensor data is performed outside the package 14.

[0016] Package 14 at least partially encapsulates the sensor 12. Package 14 can be made of a polymer material or another dielectric material to provide physical protection and insulation to the sensor 12. Package 14 can be made of glass or other light-transmitting material and may include a cover 16 that protects the sensor 12 from above. In some implementations, for example, if the sensor is an image sensor, the sensor may further include one or more optical filters (e.g., a Bayer filter array, not shown) to filter or modify the light (e.g., intensity, phase, wavelength, or polarization of the light) received by each element of the sensor (also called a pixel or cell). In some embodiments, the cover 16 may be one of the one or more optical filters. In embodiments where the sensor 12 is an image sensor, the cover 16 may include or integrate a lens, and the image sensor is configured to detect light that has been focused and concentrated by the lens.

[0017] The MEMS device 10 also includes a MEMS actuator 18, which includes a rotor 20 (also called a MEMS rotor, MEMS actuator rotor, or actuator rotor) and a stator 22 (also called a MEMS stator, MEMS actuator stator, or actuator stator). The rotor 20 is a movable part of the actuator 18, and the stator 22 is a stationary part of the actuator 18. The MEMS actuator 18 also includes a mechanical spring (not shown in this figure) that connects the rotor 20 to the stator 22 and suspends the rotor 20. In embodiments, the sensor 12 is attached to the rotor 20 using die-bonding technology via adhesive or tack. The MEMS actuator 18 and the attached sensor 12 can move relative to the stator. In embodiments, when a voltage is applied across the rotor 20 and stator 22, an electrostatic force is generated perpendicularly between adjacent piston electrodes and tube electrodes. This electrostatic force moves the rotor 20 in pure translational motion (a piston-like motion, as disclosed in U.S. Patent No. 9,306,475, which is incorporated herein by reference) along the vertical axis (for example, up and down in the orientation of Figure 1, as indicated by arrow 24). When the voltage drops, the rotor 20 returns to its equilibrium position due to the restoring force of the support springs connecting the rotor 20 to the stator 22. If the sensor 12 is an image sensor, this movement allows for focusing, for example, to compensate for thermal effects on the focus of the image sensor lens.

[0018] In one embodiment, the rotor 20 is partially enclosed by a stator 22. For example, as shown in Figure 1, the stator 22 includes a base 26 and an outer frame 28 (or support or extension) extending upward from the base 26. The rotor 20 is located within the outer frame 28, and the upper surface 30 of the rotor 20 is lower vertically than the upper surface 32 of the outer frame 28. This helps to reduce the overall vertical footprint of the MEMS device 10, while also providing a suitable structure for electrical connections via the stator 22, as will be discussed later.

[0019] A series of wire bond pads 34 are formed on the upper surface of the frame 28 of the stator 22. A dielectric insulating layer 35 may be provided between the wire bond pads 34 and the metallized layer (or upper surface) of the stator 22. The sensor 12 is wire-bonded to the wire bond pads 34 via wire bond interconnects 36. The frame 28 of the stator 22 is provided with through-silicon electrodes (TSVs) 38 that electrically connect the wire bond pads 34 to a power distribution board 40 located beneath a silicon substrate or an electrical connection layer on silicon. In one embodiment, the power distribution board 40 is a redistribution layer (RDL) attached to a silicon substrate or integrated circuit via solder balls 42. The RDL is a conductive (e.g., metallic) layer, such as a metal interconnect, that redistributes input / output (I / O) access to different parts of the substrate. This allows for better electrical access to the pads as needed. In another embodiment, the electrical distribution layer is an area array substrate, such as a ball grid array (BGA) substrate, which has solder balls 42 on its bottom surface for making connections to a circuit board. Since various substrates exist for chipboards and similar types, this component can be more generally referred to as a substrate. In yet another embodiment, the electrical distribution layer is a land grid array (LGA).

[0020] The TSV38 enables connection from the sensor 12 to the power distribution board 40 through the stator 22. Wire bond interconnects 36 electrically connect the sensor 12 to wire bond pads 34 above the frame 28 of the stator 22, and the TSV38 provides electrical connection from these wire bond pads 34 to the power distribution board 40. The MEMS actuator 18 and sensor 12 can then be sealed in package 14 using the MEMS actuator 18 (or its stator 22) as the base of the RDL. This packaging provides electrical connection from the sensor 12 to the power distribution board 40 via the MEMS stator 22. This enables a compact package of the MEMS device 10 with reduced vertical footprint.

[0021] The package 14, the power distribution board 40, and the cover 16 (if provided) are sized to allow for large vertical movement of the rotor 20 and the sensor 12. For example, an air gap may exist above the sensor 12 and below the cover 16, the size of which exceeds the combined thickness of the sensor 12 and the rotor 20. In one embodiment, the size of the gap is approximately twice the combined thickness of the sensor 12 and the rotor 20. The interior of the package 14 can be filled with a gas (e.g., an inert gas, air, N2, etc.). In another embodiment, the interior of the package is filled with a liquid that matches the refractive index of the cover 16 to enhance thermal conductivity and shock absorption.

[0022] Figure 2 shows a cross-sectional view of a MEMS device 110 according to another embodiment of the present disclosure. The MEMS device 110 in Figure 2 has a similar structure to that described above with reference to Figure 1, except that the corresponding reference numbers of these similar or identical parts are increased by 100. For brevity, embodiments of structural details described above with reference to Figure 1 also apply to the embodiments shown in Figure 2 unless otherwise specified.

[0023] Similar to Figure 1, the MEMS device 110 has a sensor 112 that is at least partially housed within a package 114, which may include a transparent (e.g., glass) cover 116 positioned above the sensor 112. The sensor 112 can move vertically via a MEMS actuator 118, as indicated by arrow 124. The MEMS actuator 118 includes a rotor 120 and a stator 122. Here again, the MEMS stator 122 may have a bottom 126 and an external frame 128 extending upward from the bottom 126. This package design makes it possible to at least partially enclose the rotor 120 within the external boundary of the stator 122, for example, vertically below the upper surface of the external frame 128 of the stator 122.

[0024] In this embodiment, the stator 122 has pads that can accommodate dual wire bonds from the sensor 112 and to a power distribution substrate 140 such as an area array substrate like a BGA substrate. Specifically, the first wire bond interconnect 136 electrically couples the sensor 112 to the wire bond pad 134, and the second wire bond interconnect 137 electrically couples the wire bond pad 134 to the power distribution substrate 140 (e.g., via the pad 139). Only one wire bond pad 134 is shown on the stator 122, but of course multiple pads can be utilized. A dielectric insulating layer 135 can be provided between the wire bond pad 134 and the metallization layer (or top surface) of the stator 122. Since it is a dual wire bond, the stator 122 need not include TSVs such as the TSV 38 shown in FIG. 1. Rather, the dielectric insulating layer 135 can electrically insulate the wire bond pad 134 from the remainder of the outer frame 128 of the stator 122.

[0025] Similar to the case of the embodiment of FIG. 1, the power distribution substrate 140 (e.g., a BGA substrate) can be sealed using a sealing material (e.g., the package 114) together with the MEMS actuator stator 122, and this sealing material seals the MEMS device 110 when the glass cover 116 is attached thereto, but still has a cavity open above the sensor 112 to allow free vertical movement of the MEMS actuator rotor 120.

[0026] The final sealed package can be soldered onto a standard PCB using, for example, reflow technology. As an example, solder balls 142 are shown.

[0027] While exemplary embodiments are described above, these embodiments are not intended to describe all possible forms that are covered by the claims. The language used in the specification is descriptive, not restrictive, and it should be understood that various modifications can be made without departing from the spirit and scope of this disclosure. As stated above, features of various embodiments can be combined to form further embodiments of the invention that may not be expressly described or illustrated. Various embodiments may be described as offering advantages or being preferable to other embodiments or implementations of the prior art with respect to one or more desired characteristics, but those skilled in the art will recognize that one or more features or characteristics may be compromised to achieve desired overall system attributes that depend on the particular application and implementation. These attributes may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc. Therefore, to the extent that any embodiment is described as being less desirable than other embodiments or implementations of the prior art with respect to one or more characteristics, these embodiments are not outside the scope of this disclosure and may be desirable for a particular application.

Claims

1. Power distribution board and An actuator stator located above the power distribution board and having a bottom and an external frame extending upward from the bottom, A stator pad is positioned above the power distribution board on the external frame, An actuator rotor suspended within the external frame above the bottom of the actuator stator, A sensor placed on the actuator rotor, A wire bond interconnection electrically connects the sensor and the stator pad, A MEMS device including, A MEMS device in which the external frame includes vias extending through its interior, the vias electrically connecting the stator pad to the power distribution board, thereby enabling an electrical connection between the sensor and the power distribution board.

2. The MEMS device according to claim 1, wherein the power distribution board is a redistribution layer (RDL).

3. The MEMS device according to claim 1, wherein the stator pad is located on the upper surface of the external frame of the actuator stator.

4. The MEMS device according to claim 1, further comprising a dielectric insulating layer that electrically insulates the stator pad from the metallized layer of the actuator stator.

5. The MEMS device according to claim 1, wherein the via is a through-silicon electrode (TSV).

6. The MEMS device according to claim 1, further comprising a package that at least partially encloses the actuator rotor and the sensor, wherein the package is sized and configured to allow vertical movement of the actuator rotor and the sensor within the package.

7. The MEMS device according to claim 6, wherein the actuator rotor and the actuator stator are configured such that when a voltage is applied across the actuator rotor and the actuator stator, an electrostatic force is generated, causing the actuator rotor to move from a first vertical position to a second vertical position relative to the actuator stator.

8. Area array substrate and An actuator stator located above the area array substrate and having a bottom and an external frame extending upward from the bottom, A stator pad is positioned above the area array substrate on the external frame, An actuator rotor suspended within the external frame above the bottom of the actuator stator, A sensor placed on the actuator rotor, A first wire bond interconnection is disposed on the sensor and the stator pad and electrically connects the sensor and the stator pad, A second wire bond interconnect is disposed on the stator pad and the area array substrate, electrically connecting the stator pad and the area array substrate to enable an electrical connection between the sensor and the area array substrate. MEMS devices, including those mentioned above.

9. The MEMS device according to claim 8, wherein the area array substrate is a ball grid array (BGA) substrate.

10. The MEMS device according to claim 8, wherein the stator pad is located on the upper surface of the external frame of the actuator stator.

11. The MEMS device according to claim 8, further comprising a dielectric insulating layer that electrically insulates the stator pad from the metallized layer of the actuator stator.

12. The MEMS device according to claim 8, further comprising a package that at least partially encloses the actuator rotor and the sensor, wherein the package is sized and configured to allow vertical movement of the actuator rotor within the package.

13. Power distribution board and An actuator stator located above the power distribution board and having a bottom, An actuator rotor suspended above the bottom of the actuator stator, the actuator rotor is configured to move perpendicular to the actuator stator, A stator pad is disposed on the actuator stator and electrically insulated from the actuator stator, A sensor attached to the actuator rotor, At least one wire bond interconnect configured to electrically couple the sensor to the power distribution board via the stator pad, MEMS devices, including those mentioned above.

14. The MEMS device according to claim 13, wherein the actuator stator includes a frame extending vertically from the bottom, and the stator pads are arranged on the frame.

15. The MEMS device according to claim 14, wherein the frame includes vias extending through its interior, the vias electrically connecting the stator pad to the power distribution board, thereby enabling an electrical connection between the sensor and the power distribution board via the stator pad.

16. The MEMS device according to claim 13, wherein the power distribution board is a redistribution layer (RDL).

17. The aforementioned at least one wire bond interconnection is A first wire bond interconnection electrically connects the sensor and the stator pad, A second wire bond interconnection electrically connects the stator pad and the power distribution board, The MEMS device according to claim 13, including the above.

18. The MEMS device according to claim 13, wherein the power distribution board is a ball grid array (BGA) board.

19. The MEMS device according to claim 13, further comprising a package that at least partially encloses the actuator rotor and the sensor, wherein the package is sized and configured to allow vertical movement of the actuator rotor within the package.

20. The MEMS device according to claim 13, further comprising a dielectric insulating layer that electrically insulates the stator pad from the metallized layer of the actuator stator.

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