MEMS package with actuator stator providing electrical connection points

Abstract

The MEMS device is provided with an actuator stator providing an electrical connection point. The MEMS device includes a power distribution substrate and an actuator stator over the power distribution substrate. The actuator stator has a bottom plate and an outer frame extending upwardly from the bottom plate. The MEMS device includes a stator pad disposed on the outer frame and over the power distribution substrate. The MEMS device also includes an actuator rotor suspended above the base plate within the outer frame with a sensor mounted thereon. A wire bond interconnect electrically couples the sensor to the stator pad. In some embodiments, the outer frame includes a through-hole extending therethrough that electrically connects the stator pad with the power distribution substrate, thereby enabling an electrical connection between the sensor and the power distribution substrate. In some embodiments, a second wire bond interconnect electrically connects the stator pad and the substrate.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to microelectromechanical system (MEMS) devices and associated MEMS packaging in which a static structure of a MEMS actuator (e.g., a stator) provides an electrical connection point for a sensor. BACKGROUND

[0002] MEMS devices are generally considered to be micro devices that incorporate both electronic and moving components. They 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

[0003] According to one embodiment, a MEMS device includes a power distribution substrate and an actuator stator positioned above the power distribution substrate, the actuator stator having a base plate and an outer frame extending upwardly from the base plate. The MEMS device also includes a stator pad disposed on the outer frame and above the power distribution substrate, and an actuator rotor suspended above the base plate of the actuator stator and within the outer frame. The MEMS device further includes a sensor disposed on the actuator rotor, and a wire bond interconnect electrically coupling the sensor and the stator pad. The outer frame includes a through hole extending therethrough that electrically connects the stator pad with the power distribution substrate, thereby enabling an electrical connection between the sensor and the power distribution substrate.

[0004] In one embodiment, a MEMS device includes a region array substrate; an actuator stator positioned above the region array substrate, the actuator stator having a base plate and an outer frame extending upwardly from the base plate; a stator pad disposed on the outer frame and above the region array substrate; an actuator rotor suspended above the base plate of the actuator stator and within the outer frame; a sensor disposed on the actuator rotor; a first wire bond interconnect disposed on and electrically connecting the sensor and the stator pad; and a second wire bond interconnect disposed on and electrically connecting the stator pad and the region array substrate to enable an electrical connection between the sensor and the region array substrate.

[0005] In one embodiment, a MEMS device includes a power distribution substrate; an actuator stator positioned above the power distribution substrate and having a base plate; an actuator rotor suspended above the base plate of the actuator stator, wherein the actuator rotor is configured to move in a vertical direction relative to the actuator stator; a stator pad disposed on the actuator stator and electrically insulated from the actuator stator; a sensor mounted to the actuator rotor; and at least one wire bond interconnect configured to electrically couple the sensor to the power distribution substrate through the stator pad. BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1is a cross-sectional view of a MEMS device and associated MEMS package according to one embodiment of the present disclosure.

[0007] Figure 2 is a cross-sectional view of a MEMS device and associated MEMS package according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0008] Embodiments of the present disclosure are described herein. It is to be understood, however, that the embodiments disclosed are merely examples, and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features can be exaggerated or minimised for clarity. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those skilled in the art will appreciate, the various features shown and described either with reference to any one figure or more figures can be combined with those of other figures to produce embodiments that are not explicitly shown or described. The combination of features from different figures serves to produce embodiments that are not specifically mentioned or implied in the following disclosure.

[0009] As used herein, the singular forms "a", "an" and "the" refer to both the singular as well as plural, unless the context clearly indicates otherwise. For example, "a stator" refers to one stator or more than one stator.

[0010] MEMS devices are generally considered to incorporate both electronic components and moving components. They often 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.

[0011] Certain prior art systems include MEMS devices with image sensors (e.g., cameras) mounted on MEMS actuators that can move the image sensor focal plane along the optical axis in order to adjust the focal position. The image sensor is located below or above the circuit board and wire-bonded to the circuit board. However, in systems such as these, the relatively long wire-bonds can be prone to movement and shorting when the MEMS device is used in a harshly moving environment such as a car. Furthermore, this approach consumes top and bottom circuit board area, particularly in cases where the image sensor is located below the circuit board. The wire-bond profile is higher than typical solutions to mitigate stress on the bond, but can increase the risk of the bond shorting to the bond during operation and manufacturing. This makes miniaturization difficult.

[0012] Therefore, according to the various embodiments disclosed herein, MEMS devices are packaged in a manner that utilizes a stator to electrically connect to a circuit board (or other power distribution layer or substrate). In embodiments, the actuator has a rotor and a stator and is disposed within the MEMS device to move a sensor mounted with the MEMS; the sensor mounted with the MEMS is mounted on the rotor and electrically connected to the stator via wire bonding interconnects. This allows for greater miniaturization of the MEMS device and its package, while enabling free movement of the sensor and actuator.

[0013] Figure 1 A cross-sectional view of a MEMS device 10 according to an embodiment of the present disclosure is shown. The reference to "MEMS device" is intended to refer to a device comprising a package containing a sensor (also more generally referred to as a sensor herein) on which the MEMS is mounted, the circuitry electrically connected thereto, and the package itself. Therefore, the MEMS device 10 may also be referred to as a MEMS system or a microsystem.

[0014] MEMS device 10 includes a sensor 12 housed within a package 14, also referred to as a MEMS package or encapsulation. Sensor 12 can be a single sensor or a sensor array. Sensor 12 can be an image sensor, such as a camera, LiDAR sensor, radar sensor, etc., and can include an array (e.g., a one-dimensional or two-dimensional array) of sensor units (or pixels) for sensing optical signals. For example, sensor 12 can include a photoelectric sensor, such as a photodiode, which can generate a voltage or current signal corresponding to the intensity of a light signal illuminating a pixel. For example, each pixel can convert the light signal incident on the pixel into a current, or integrate the current using a capacitor to generate a voltage signal. The current or voltage signal can be converted into digital pixel data by an analog-to-digital converter. Thus, each pixel can generate digital pixel data representing the intensity of light received by that pixel. The pixel data from the pixels in the sensor array can represent an image of an object or scene. In a particular embodiment, sensor 12 includes a charge-connected device (CCD) image sensor comprising an array of photoelectric sensors and 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.

[0015] 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 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 in this disclosure are not limited to a particular type of sensor.

[0016] MEMS device 10 may also include a processor (e.g., a microprocessor) coupled to or integrated into sensor 12, configured to at least partially process data received from sensor 12 (e.g., pixel data in the above embodiments). In other embodiments, sensor data processing occurs outside of package 14.

[0017] Encapsulation 14 at least partially encapsulates sensor 12. Encapsulation 14 may be made of a polymer material or another dielectric material to provide physical protection and insulation to sensor 12. Encapsulation 14 may include a cover 16 made of glass or other optically transparent material that protects sensor 12 from above. In some embodiments, such as when the sensor is an image sensor, the sensor may also include one or more optical filters (e.g., a Bayer filter array, not shown) to filter or modify light received by each element (also referred to as a pixel or cell) of the sensor (e.g., the intensity, phase, wavelength, or polarization of the light). In some embodiments, cover 16 may be one of one or more filters. In embodiments where sensor 12 is an image sensor, cover 16 may include or integrate a lens, wherein the image sensor is configured to detect light collected and focused by the lens.

[0018] MEMS device 10 also includes a MEMS actuator 18, which includes a rotor 20 (also referred to as a MEMS rotor, MEMS actuator rotor, or actuator rotor) and a stator 22 (also referred to as a MEMS stator, MEMS actuator stator, or actuator stator). The rotor 20 is the moving portion of the actuator 18, and the stator 22 is the stationary portion of the actuator 18. The MEMS actuator 18 also includes a mechanical spring (not shown in this view) that connects the rotor 20 to the stator 22, thereby suspending the rotor 20. In an embodiment, sensor 12 is attached to the rotor 20 via glue or adhesive using die-bonding technology. The MEMS actuator 18 and the attached sensor 12 can move relative to the stator. In an embodiment, when a voltage is applied across the rotor 20 and stator 22, an electrostatic force is generated in the vertical direction between adjacent pistons and tube electrodes. This electrostatic force causes the rotor 20 to move from its static position along the vertical axis (e.g., in…). Figure 1 The rotor 20 moves toward the stator 22 in a purely translational (piston-like, such as that disclosed in U.S. Patent No. 9,306,475, the entire contents of which are incorporated herein by reference) manner, moving up and down as indicated by arrow 24. When the voltage drops, the rotor 20 moves back to its equilibrium position due to the restoring force in the support springs that connect the rotor 20 to the stator 22. For example, in the case where the sensor 12 is an image sensor, this movement allows for focus adjustment to compensate for thermal effects at the lens focus of the image sensor.

[0019] In one embodiment, the rotor 20 is partially surrounded by the stator 22. For example, as Figure 1 As shown, the stator 22 includes a base plate 26 and an outer frame 28 (or column or extension) extending upward from the base plate 26. The rotor 20 is located within the outer frame 28, with its upper surface 30 vertically below the upper surface 32 of the outer frame 28. This helps to reduce the overall vertical footprint of the MEMS device 10 while still providing a suitable structure for electrical connections via the stator 22, as further described below.

[0020] A series of wire bonding pads 34 are fabricated on the top surface of the frame 28 of the stator 22. A dielectric insulating layer 35 may be disposed between the wire bonding pads 34 and the metallization layer (or top surface) of the stator 22. The sensor 12 is wirebonded to the wire bonding pads 34 via wire bonding interconnects 36. The frame 28 of the stator 22 is provided with through-silicon vias (TSVs) 38, which electrically connect the wire bonding pads 34 to the underlying power distribution substrate 40, such as a silicon substrate or an electrical connection layer on silicon. In one embodiment, the power distribution substrate 40 is a redistribution layer (RDL) attached to the silicon substrate or integrated circuit via solder balls 42. The RDL is a conductive (e.g., metal) layer, such as a metal interconnect, that redistributes input / output (I / O) access to different portions of the substrate. This allows for better electrical access to the pads when necessary. In another embodiment, the power distribution layer is a region array substrate, such as a ball grid array (BGA) substrate, having solder balls 42 on its bottom surface for connection to a circuit board. Because various substrates exist for use with chipsets, etc., this component can be more generally referred to as a substrate. In other embodiments, the power distribution layer is a planar grid array (LGA).

[0021] TSV 38 allows connection from sensor 12 to power distribution substrate 40 via stator 22. Wire bond interconnects 36 electrically connect sensor 12 to wire bond pads 34 above frame 28 of stator 22, and TSV 38 in turn provides electrical connections from these wire bond pads 34 to power distribution substrate 40. MEMS actuator 18 (or its stator 22) can then be used as the base of RDL, encapsulating MEMS actuator 18 and sensor 12 in package 14. This package provides electrical connections from sensor 12 to power distribution substrate 40 via MEMS stator 22. This results in a compact package of MEMS device 10 with a reduced vertical footprint.

[0022] The package 14, the power distribution board 40, and the cover 16 (if provided) are sized to allow the rotor 20 and sensor 12 to move significantly vertically. For example, an air gap may exist above the sensor 12 and below the cover 16, where the size of this gap exceeds the combined thickness of the sensor 12 and rotor 20. In one embodiment, the gap is approximately twice the combined thickness of the sensor 12 and rotor 20. The interior of the package 14 may 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 whose refractive index matches that of the cover 16 to increase thermal conductivity and shock absorption.

[0023] Figure 2 A cross-sectional view of a MEMS device 110 according to another embodiment of the present disclosure is shown. Figure 2 The MEMS device 110 has the same characteristics as the reference above. Figure 1 The description uses similar structures, and the corresponding reference numerals for these similar or identical parts are increased by 100. For the sake of brevity, unless otherwise stated, the above references... Figure 1 The embodiments described in the structural details are also applicable to Figure 2 The embodiment shown.

[0024] Similar to Figure 1 The MEMS device 110 has a sensor 112 at least partially contained within a package 114, which may include a transparent (e.g., glass) cover 116 located above the sensor 112. The sensor 112 is movable in a vertical direction, as indicated by arrow 124, via a MEMS actuator 118. The MEMS actuator 118 includes a rotor 120 and a stator 122. Again, the MEMS stator 122 may have a base plate 126 and an outer frame 128 extending upward from the base plate 126. This packaging design allows the rotor 120 to be at least partially enclosed within the outer boundaries of the stator 122, for example, vertically below the upper surface of the outer frame 128 of the stator 122.

[0025] In this embodiment, the stator 122 has pads capable of accommodating double wire bonding, one from the sensor 112 and the other to a power distribution substrate 140, such as a region array substrate like a BGA substrate. Specifically, a first wire bonding interconnect 136 electrically connects the sensor 112 to the wire bonding pad 134, and a second wire bonding interconnect 137 electrically connects the wire bonding pad 134 to the power distribution substrate 140 (e.g., via pad 139). Although only one wire bonding pad 134 is shown on the stator 122, multiple pads can certainly be used. A dielectric insulating layer 135 may be disposed between the wire bonding pad 134 and the metallization layer (or top surface) of the stator 122. Due to the double wire bonding, the stator 122 does not need to include a TSV, for example... Figure 1The TSV 38 is shown. Conversely, the dielectric insulating layer 135 can electrically insulate the wire bonding pads 134 from the rest of the outer frame 128 of the stator 122.

[0026] As in Figure 1 Figure 1 In the embodiments described, the power distribution board 140 (e.g., a BGA board) together with the MEMS actuator stator 122 can be encapsulated with an encapsulation material (e.g., a package 114). When the glass cover 116 is mounted to the MEMS device 110, the encapsulation material will seal the MEMS device 110, but there will still be an open cavity above the sensor 112 to allow free vertical movement of the MEMS actuator rotor 120.

[0027] For example, reflow soldering technology can be used to solder the final encapsulated package onto a standard PCB. Solder ball 142 is shown as an example.

[0028] While exemplary embodiments have been described above, it is not intended that these embodiments describe all possible forms contained in the claims. The language used in this specification is descriptive rather than restrictive, and it should be understood that various changes may be made without departing from the spirit and scope of this disclosure. As previously stated, features of various embodiments may be combined to form further embodiments of the invention that may not be explicitly described or shown. While various embodiments may have been described as providing advantages or superiority over other embodiments or prior art implementations in one or more desired characteristics, those skilled in the art will recognize that one or more features or characteristics may be compromised to achieve desired overall system properties, depending on the specific application and implementation. These properties may include, but are not limited to, cost, strength, durability, lifecycle cost, marketability, appearance, package, size, maintainability, weight, manufacturability, ease of assembly, etc. Therefore, any embodiment described as less desirable than other embodiments or prior art implementations in one or more characteristics is not outside the scope of this disclosure and may be desirable for a particular application.

Claims

1. A MEMS device, comprising: Power distribution board; An actuator stator is positioned above the power distribution board, the actuator stator having a base plate and an outer frame extending upward from the base plate; Stator pads are disposed on the outer frame and above the power distribution substrate; An actuator rotor, which is suspended above the base plate of the actuator stator and within the outer frame; A sensor is disposed on the actuator rotor; and Wire bonding interconnects electrically connect the sensor and the stator pads; The outer frame includes a through hole extending therethrough, which electrically connects the stator pad to the power distribution board, thereby realizing the electrical connection between the sensor and the power distribution board.

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

3. The MEMS device according to claim 1, wherein, The stator pads are disposed on the upper surface of the outer frame of the actuator stator.

4. The MEMS device according to claim 1 further includes a dielectric insulating layer, the dielectric insulating layer electrically insulating the stator pads from the metallization layer of the actuator stator.

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

6. The MEMS device of claim 1, further comprising a package that at least partially encapsulates the actuator rotor and the sensor, wherein, The size and configuration of the package allow the actuator rotor and the sensor to move vertically 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 to move the actuator rotor relative to the actuator stator from a first vertical position to a second vertical position.

8. A MEMS device, comprising: Regional array substrate; An actuator stator is positioned above the regional array substrate, the actuator stator having a base plate and an outer frame extending upward from the base plate; Stator pads are disposed on the outer frame and above the regional array substrate; An actuator rotor, which is suspended above the base plate of the actuator stator and within the outer frame; A sensor is disposed on the actuator rotor; A first wire bonding interconnect is disposed on the sensor and the stator pad and electrically connects the sensor and the stator pad; and The second wire bonding interconnect is disposed on the stator pad and the area array substrate and electrically connects the stator pad and the area array substrate to realize the electrical connection between the sensor and the area array substrate.

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

10. The MEMS device according to claim 8, wherein, The stator pads are disposed on the upper surface of the outer frame of the actuator stator.

11. The MEMS device of claim 8, further comprising a dielectric insulating layer that electrically insulates the stator pads from the metallization layer of the actuator stator.

12. The MEMS device of claim 8, further comprising a package that at least partially encapsulates the actuator rotor and the sensor, wherein, The size and configuration of the package are designed to enable the actuator rotor to move vertically within the package.

13. A MEMS device, comprising: Power distribution board; An actuator stator is positioned above the power distribution board and has a base plate. An actuator rotor is suspended above the base plate of the actuator stator, wherein the actuator rotor is configured to move vertically relative to the actuator stator. Stator pads, the stator pads being disposed on the actuator stator and electrically insulated from the actuator stator; Sensor, the sensor being mounted to the actuator rotor; and At least one wire bonding interconnect is configured to electrically connect the sensor to the power distribution substrate via the stator pad.

14. The MEMS device according to claim 13, wherein, The actuator stator includes a frame extending from the base plate along the vertical direction, wherein the stator pads are disposed on the frame.

15. The MEMS device according to claim 14, wherein, The frame includes through-holes extending therethrough, which electrically connect the stator pads to the power distribution substrate, thereby enabling electrical connection between the sensor and the power distribution substrate via the stator pads.

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

17. The MEMS device according to claim 13, wherein, The at least one wire bonding interconnect includes: The first wire bonding interconnects the sensor and the stator pads; and The second lead is bonded to interconnect the stator pads and the power distribution substrate.

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

19. The MEMS device of claim 13, further comprising a package that at least partially encapsulates the actuator rotor and the sensor, wherein, The size and configuration of the package are designed to enable the actuator rotor to move vertically within the package.

20. The MEMS device of claim 13, further comprising a dielectric insulating layer that electrically insulates the stator pads from the metallization layer of the actuator stator.

Images