Encapsulated environmental sensor

Abstract

An encapsulated environmental sensor includes a support structure and a sensor die containing an environmental sensor and disposed on a first side of the support structure. A control chip is coupled to the sensor die and disposed on a second side of the support structure opposite the first side. A cover is joined to the first side of the support structure and open to an exterior in a direction opposite the support structure. The sensor die is housed within the cover.

Description

Technical Field

[0001] This disclosure relates to an encapsulated environmental sensor. Background Technology

[0002] As is well known, environmental sensors are sensors that enable the detection of quantities in the external environment, such as pressure or humidity. The application areas of environmental sensors are extremely diverse. Among other applications, environmental sensors have recently been widely used in so-called wearable devices such as watches, bracelets, and smart bands, which also enable the detection of bodily parameters.

[0003] Environmental sensors typically consist of a sensor die, such as a MEMS (Micro-Electro-Mechanical Systems) type, and control circuitry integrated into a separate control chip, also known as an ASIC (Application-Specific Integrated Circuit) chip. The sensor die and control chip are enclosed within a package structure (usually called a package), which includes a support structure, typically ceramic, and a cap. A cavity is defined within the support structure, in which the sensor die and control chip are housed. The sensor die is typically stacked on top of the control chip. The cap is positioned to partially close the cavity, and this cap has a detection port that allows the sensor die to couple to the external environment, enabling the measurement of the quantity to be detected. In other cases, such as due to the shape of the cap itself, a cavity may be defined between the support structure and the cap. Furthermore, the cavity is generally filled with a protective material, such as a potting gel, which has properties that transmit the quantity to be detected while preventing the sensor and control chip from being directly exposed to the external environment, which could be harmful to electronic components and electrical connections (such as bonding wires). Furthermore, in devices typically used as wearables, environmental sensors may actually be exposed to corrosive agents such as chlorine in swimming pool water, seawater, mineral oil, or substances present on the skin (such as sweat or some perfumes). While an acceptable level of protection is often achieved using only gel for the sensor die and control device, the problem arises of sealing the device itself, which also contains the environmental sensor. In fact, a gap exists between the environmental sensor and the device housing, and this gap must be sealed to prevent the ingress of corrosive agents. The known packaging structure of environmental sensors makes this task problematic. Known solutions use gaskets and a housing that surrounds both the sensor and the gasket, thus keeping them pre-loaded. Other solutions use a complex metal cap with a dome-shaped portion that covers the control chip (which has a much larger area than the sensor die) and an arc-shaped to essentially cylindrical neck. This neck serves a dual function: ensuring the sensor die is coupled to the external environment and defining a sealing surface for receiving gaskets (O-rings, etc.). However, this solution is limited not only because the cap is complex and costly to manufacture, but also because of problems that arise during the soldering process. In reality, the coefficient of thermal expansion of the potting material is much greater than that of the material forming the cap. During welding, the potting material may apply force to the dome-shaped portion, a force that tends to cause the cap to detach from the support structure. The result is a significant risk of failure or weakening of the connection between the cap and the support structure. Summary of the Invention

[0004] In various embodiments, this disclosure provides an encapsulated environmental sensor that will enable the overcoming or at least mitigation of the described limitations.

[0005] In at least one embodiment of this disclosure, a packaged environmental sensor is provided, comprising a support structure and a sensor die containing an environmental sensor and disposed on a first side of the support structure. A control chip is coupled to the sensor die and disposed on a second side of the support structure opposite to the first side. A cover engages with the first side of the support structure and opens outward in a direction opposite to the support structure, the sensor die being housed within the cover.

[0006] In at least one embodiment, an electronic system is provided, including a housing and a processing unit within the housing. An environmental sensor is coupled to the processing unit. The environmental sensor includes a support structure and a sensor die containing an environmental sensor, and is disposed on a first side of the support structure. A control chip is coupled to the sensor die and is disposed on a second side of the support structure opposite to the first side. A cover engages with the first side of the support structure and opens outwardly in a direction opposite to the support structure, the sensor die being housed within the cover.

[0007] In at least one embodiment, a device is provided including a support structure having a first side and a second side opposite to the first side. The support structure defines a cavity extending from the second side into the support structure. An environmental sensor die is disposed on the first side of the support structure, and a control chip is disposed within the cavity and attached to the support structure. A cover is attached to the first side of the support structure and opens outwardly in a direction opposite to the support structure. The sensor die is accommodated between the cover and the support structure. Attached Figure Description

[0008] To better understand this disclosure, some embodiments of the disclosure will now be described by way of non-limiting example and with reference to the accompanying drawings, wherein:

[0009] Figure 1 It is a simplified block diagram of an electronic system that includes a packaged environmental sensor;

[0010] Figure 2 yes Figure 1 A side view of the electronic system, taken in the longitudinal plane;

[0011] Figure 3 It is included Figure 1 An encapsulated environment sensor in an electronic system according to an embodiment of the present disclosure, in Figure 4 The front view taken from the plane of trace III-III;

[0012] Figure 4 From Figure 3 A plan view of the sensor's encapsulated environment from below;

[0013] Figure 5 yes Figure 3 A top view of the encapsulated environment sensor;

[0014] Figure 6 This is a front view, taken in a transverse plane, of a packaged environment sensor according to a different embodiment of the present disclosure, which can be used for... Figure 1 Electronic systems; and

[0015] Figure 7 This is a front view taken in a transverse plane of a packaged environment sensor according to another embodiment of the present disclosure, which can be used for... Figure 1 In electronic systems. Detailed Implementation

[0016] refer to Figure 1 The electronic device, as a whole, is designated by reference numeral 1 and can be any type of electronic device, particularly but not exclusively, a wearable device (such as a watch, bracelet, or smart band), a computer (such as a mainframe, personal computer, laptop, or tablet), a smartphone, a digital music player, a digital camera, or any other device suitable for processing, storing, transmitting, or receiving information. Electronic device 1 can be a general-purpose computer system or can be embedded in a device, apparatus, or other system.

[0017] Electronic device 1 includes a processing unit 2, a data storage medium 3, and an encapsulated environment sensor 10. It may also include input / output (I / O) devices 5 (e.g., a keypad, mouse, or touchscreen), a wireless interface 6, peripheral devices 7.1, ..., 7.N, and possibly other auxiliary devices (not shown). Components of electronic device 1 can be directly and / or indirectly coupled to each other via a bus 8. Furthermore, electronic device 1 may include a battery 9. It should be noted that the scope of this disclosure is not limited to embodiments that must have one or all of the listed devices.

[0018] Depending on design preferences, processing unit 2 may include, for example, one or more microprocessors, microcontrollers, etc.

[0019] The data storage medium 3 may include various types of volatile and non-volatile memory devices, such as SRAM and / or DRAM in the case of volatile memory, and solid-state memory, as well as disks and / or optical disks in the case of non-volatile memory.

[0020] refer to Figure 2The electronic device 1 includes a housing 11 that houses a printed circuit board (PCB) 12 and at least a portion of the components. Specifically, the encapsulation environment sensor 10 is mounted directly on the PCB 12, either directly or via a bracket 13. Additionally, the encapsulation environment sensor 10 communicates with the outside environment through an opening 15 in the housing 11. The gap between the edge of the opening 15 and the encapsulation environment sensor 10 is sealed by a gasket 16 (e.g., an O-ring).

[0021] The encapsulated environment sensor 10 can be any sensor suitable for detecting parameters or quantities of the external environment. By way of non-limiting example, the encapsulated environment sensor 10 can be a pressure sensor, a humidity sensor, a temperature sensor, or some other environmental sensor.

[0022] like Figures 3 to 5 As shown, the packaged environment sensor 10 includes a support structure 17, a sensor die 18, a control or ASIC chip 20, and a collar-shaped cover 21. The cover can be a collar, ring, etc.

[0023] The support structure 17 is, for example, ceramic and has a first surface 17a and a second surface 17b. The sensor die 18 is fixed to the first surface 17a via a die attachment area 22, and the surface 17b is opposite to the first surface 17a.

[0024] For example, cap attachment regions 23a-23c of the metal solder paste are arranged around the sensor die 18 on the first surface 17a of the support structure 17. In one embodiment, cap attachment regions 23a-23c extend along corresponding closed continuous paths. Specifically, cap attachment regions 23a-23c have similar geometric relationships to each other, and one of the cap attachment regions 23a-23c conforms to the edge of the cap 21 that engages with the support structure 17. Furthermore, cap attachment regions 23a-23c are nested within each other without contacting each other. For example, cap attachment regions 23a-23c may be three concentric circular or elliptical concentric rings, separated from each other. However, it should be understood that the shape and number of cap attachment regions 23a-23c can be freely chosen according to design preferences, for example, to correspond to the shape and size of the cap available or used in any case. For example, cap attachment regions 23a-23c may have a polygonal shape. Instead, the size of the cap is selected according to the size of the gasket 16.

[0025] Sensor die 18 includes an environmental sensor 19. In particular, sensor die 18 may include a MEMS sensing structure, such as a membrane structure, which can be used as a pressure sensor or a sensor for detecting some other environmental quantity, such as temperature or humidity.

[0026] Cavity 24 is formed in the second surface 17b of support structure 17 and accommodates control chip 20. In one embodiment, step 25 is formed around one or more sides of control chip 20. Thus, control chip 20 is actually accommodated in a recess on the bottom of cavity 24, and therefore on the opposite side of support structure 17 relative to sensor die 18. Control chip 20 may include control circuitry for driving the MEMS structure and for converting physical quantities into useful signals.

[0027] The sensor die 18 and the control chip are coupled together via bonding wire 29, connecting wire 32, and bonding wire 35. Bonding wire 29 is located between the contact pad 30 of the sensor die 18 and the contact pad 31 on the first surface 17a of the support structure 17. Connecting wire 32 is embedded in the support structure 17 between contact pad 31 and contact pad 34, which is located on a step 25 of the support structure 17 surrounding the control chip 20. Bonding wire 35 is located between contact pad 34 and contact pad 37 of the control chip 20. Further, contact pad 37, bonding wire 35, contact pad 34, and connecting wire 32 connect the control chip to a conductive solder pad 40, which is used to bond the support structure 17 to the PCB 41. The PCB 41 is then mechanically and electrically coupled to the bracket 13 (or directly coupled to the PCB 12 if the bracket 13 is not present). Alternatively, the support structure 17 can be directly soldered to the PCB 12.

[0028] The protective structure 45 (e.g., the top structure of the mass) fills at least a portion of the cavity 24 and includes or covers the control chip 20 and the connection wiring 35.

[0029] The lid 21 is defined by an annular wall and engages with one of the lid attachment regions 23a-23c (in Figure 3 In the example, the cover 21 is engaged with the intermediate fixing region 23b, and the edge of the cover 21 is conformal to the intermediate fixing region 23b. In one embodiment, the cover 21 has a frustoconical shape, and its generatrix G forms an angle α greater than 80° with a plane (externally) parallel to the first face 17a of the support structure 17. Alternatively, the cover 21 may be cylindrical. A gasket 16 is arranged around the cover 21, which seals the gap between the edge of the opening 15 of the housing 11 and the encapsulated environment sensor 10.

[0030] The cover 21 has openings on both of its bases. The smaller base 21a of the cover 21 engages with the first surface 17a of the support structure 17 and has a profile conforming to one of the cover attachment regions 23a-23c, particularly the intermediate cover attachment region 23b. The larger base 21b of the cover 21 opens outward in a direction opposite to that of the support structure 17. The height of the cover 21 is such that the sensor die 18 is completely contained within the cover 21.

[0031] Furthermore, the cap 21 is at least partially filled with a protective layer 43 that completely encloses the sensor die 18 and the bonding wires. The protective layer 43 is made of a material that couples the sensor die 18 to the measured environmental quantity and simultaneously protects the sensor die 18, bonding wires 29, and pads 31 from corrosive external agents. For example, the protective layer 43 could be a silicone potting gel.

[0032] As mentioned, the dimensions of the cover 21 are related to the dimensions of the opening 15 to be sealed and the dimensions of the gasket 16.

[0033] exist Figure 6 In this embodiment, except for the size of the cover, the encapsulation environment sensor 100 is the same as the encapsulation environment sensor 10 already described, and the cover is specified herein by reference numeral 121. In this case, the size of the cover 121 is compatible with the size of the outermost cover attachment region 23a, and the cover 121 is engaged to the first surface 17a of the support structure 17 through the outermost cover attachment region 23a.

[0034] Figure 7 This designation represents a packaged environment sensor 200 according to a different embodiment of the present disclosure, wherein the described elements are designated by the same reference numerals. The packaged environment sensor 200 includes a support structure 217, a sensor die 18, and a control chip 20. In this case, the control chip 20 is bonded to the support structure 217 using flip-chip technology. A cavity 224 is formed on the second surface 217b of the support structure 217, and the cavity 224 accommodates the control chip 20 without requiring steps around the control chip 20 itself. Furthermore, connection lines 232 connect contact pads 31 on the first surface 217a of the support structure 217 to a first set of contact pads 37 of the control chip 20, and connect a second set of contact pads 37 to solder pads 240 of the support structure 217. Cap attachment regions 223a-223c are formed on the first surface 217a of the support structure 217, in this case, the three cap attachment regions also having a circular shape and being concentric with respect to each other. A cap 221 is engaged with the innermost cap attachment region 223c.

[0035] The described encapsulated environment sensor offers several advantages. First, the control chip, located on the opposite side of the support structure relative to the sensor die, is enclosed in a space that can be conveniently sealed during use using a gasket between the edge of an opening in the collar and the housing of the electronic device, within which the encapsulated environment sensor is mounted. Therefore, the encapsulated environment sensor is never exposed to physically and / or chemically corrosive external environments. Consequently, compared to known environmental sensors, not only is the control circuitry inherently safer, but there is also greater freedom in selecting the protective material embedded in the control circuitry. Furthermore, the control chip is isolated from external light so that it remains unaffected by external light even if its surface may be photosensitive.

[0036] The shape and size of the cap are independent of the size of the control chip, which is typically five to six times larger than the area of ​​the sensor die. The control chip can be easily housed within the cavity of the ceramic support structure, and the size of the cap can be conveniently selected based solely on the structural and dimensional characteristics of the sensor die.

[0037] In contrast to what happens in some known environmental sensors (especially between a large, rectangular area protecting the control chip and a circular neck for coupling with an O-ring used as a gasket), the shape of the cover can be extremely simple because no specific connector is required.

[0038] The shape, size, and number of cap attachment areas can be chosen with maximum flexibility according to design preferences. Therefore, numerous examples of the support structure itself can be mass-produced, thus reducing manufacturing costs. In cases where multiple cap attachment areas exist, the same type of support structure can be used with caps and gaskets of various sizes without any expensive custom intervention.

[0039] During the welding process, the shape of the cap (whether cylindrical or truncated conical, with the small base joining to the support structure) allows for the accommodation of a higher degree of thermal expansion of the potting material (compared to the thermal expansion of the material forming the cap) without causing damage to the structure itself. For example... Figure 3 As indicated by the arrows, specifically in the direction parallel to the first surface of the support structure, the forces generated by the different coefficients of thermal expansion are released on the sidewall, which can withstand the load without any risk. Conversely, in the direction perpendicular to the first surface of the support structure, the potting material can expand freely outward without exerting a force that tends to detach the cap from the support structure.

[0040] Finally, it will be apparent that modifications and variations can be made to the described packaged environment sensor without departing from the scope of this disclosure.

[0041] Other embodiments can be provided by combining the various embodiments described above. These and other changes can be made to the embodiments based on the detailed description above. Generally, the terminology used in the appended claims should not be construed as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be interpreted to include all possible embodiments and the full scope of equivalents enjoyed by such claims. Therefore, the claims are not limited to this disclosure.

Claims

1. A packaged environmental sensor, comprising: a support structure; a sensor die containing an environmental sensor and arranged on a first side of the support structure; a control chip coupled to the sensor die and arranged on a second side of the support structure opposite the first side; and a lid opening towards an exterior in a direction opposite the support structure, the sensor die being housed inside the lid; a plurality of lid attachment areas on the first side of the support structure around the sensor die, wherein the lid is joined to the first side of the support structure through one of the plurality of lid attachment areas, and wherein the plurality of lid attachment areas extend along respective closed continuous paths and are nested with each other.

2. The sensor of claim 1, wherein the plurality of lid attachment areas have a mutual similar geometric relationship and a lid edge attached to the support structure is conformal with one of the plurality of lid attachment areas.

3. The sensor of claim 1, wherein the plurality of lid attachment areas comprise circular or elliptical concentric rings and are separated from each other.

4. The sensor of claim 1, wherein the lid comprises an annular wall having a profile conformal with one of the plurality of lid attachment areas.

5. The sensor of claim 4, wherein the lid has a shape of a portion of a surface of revolution.

6. The sensor of claim 5, wherein the lid has a truncated conical shape, a large base of the truncated conical shape opening towards an exterior in a direction opposite the support structure and a small base of the truncated conical shape opening and being joined to the first side of the support structure through one of the plurality of lid attachment areas.

7. The sensor of claim 1, wherein the lid is at least partially filled with a protective layer covering the sensor die.

8. The sensor of claim 7, wherein the protective layer is made of a material coupling the sensor die to an environmental quantity to be measured.

9. The sensor of claim 1, wherein the support structure has a cavity in the second side and the control chip is housed in the cavity.

10. The sensor of claim 9, comprising a protective structure covering the control chip inside the cavity.

11. The sensor of claim 1, wherein the sensor die and the control chip are coupled to each other through a connection line embedded in the support structure.

12. An electronic system, comprising: a housing; a processing unit inside the housing; and a packaged environmental sensor coupled to the processing unit, the packaged environmental sensor comprising: a support structure; a sensor die containing an environmental sensor and arranged on a first side of the support structure; a control chip coupled to the sensor die and arranged on a second side of the support structure opposite the first side. ​ a control chip coupled to the sensor die and disposed on a second side of the support structure opposite the first side; and a lid open to an exterior in a direction opposite the support structure, the sensor die being housed inside the lid; a plurality of lid attachment areas on the first side of the support structure around the sensor die; wherein the lid is joined to the first side of the support structure through one of the plurality of lid attachment areas, and wherein the plurality of lid attachment areas extend along respective closed continuous paths and nest with one another.

13. The electronic system of claim 12, wherein the package environmental sensor is in communication with an exterior through a hole in the housing, and a gap between an edge of the opening and the lid of the package environmental sensor is sealed by a gasket.

14. A sensor device, comprising: a support structure having a first side and a second side opposite the first side, the support structure defining a cavity extending into the support structure from the second side; an environmental sensor die on the first side of the support structure; a control chip disposed within the cavity and attached to the support structure; and a lid open to an exterior in a direction opposite the support structure, the sensor die being housed between the lid and the support structure, a plurality of lid attachment areas on the first side of the support structure around the sensor die, wherein the lid is joined to the first side of the support structure through one of the plurality of lid attachment areas, and wherein the plurality of lid attachment areas extend along respective closed continuous paths and nest with one another.

15. The sensor device of claim 14, wherein the control chip is electrically coupled to the environmental sensor die via the support structure.

16. The sensor device of claim 14, further comprising a printed circuit board, wherein the second side of the support structure is electrically and physically coupled to the printed circuit board.

17. The sensor device of claim 14, wherein the lid is at least partially filled with a protective layer covering the sensor die.

18. The sensor device of claim 14, comprising a protective structure covering the control chip inside the cavity. ​

Images