Chip-on-glass architecture for thermal dissipation

Abstract

A glass substrate architecture for mounting RF components may be configured for heat dissipation. Existing millimeter wave radiofrequency (RF) systems mount the radiofrequency integrated circuits (RFICs) on a printed circuit board on the opposite side of a heat sink, making it difficult to dissipate heat away from the RFICs during operation. This architecture mounts the RFICs directly to a back side of a glass waveguide substrate, and thermally couples the top side of the RFICs to a conductive pad on the underlying printed circuit board with a thermal pathway to the heatsink. This leads to a much more effective dissipation of heat away from the RFICs and eliminates the need for additional cooling systems or throttling the performance of the radar system.

Description

Attorney Docket No. 080042- 1522031-44025385WO01CHIP-ON-GLASS ARCHITECTURE FOR THERMAL DISSIPATIONCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of and priority to U.S. Provisional Application No. 63 / 706,739, filed on October 13, 2024, and titled “CHIP-ON-GLASS ARCHITECTURE FOR THERMAL DISSIPATION,” the content of which is herein incorporated by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] This disclosure generally describes thermal dissipation techniques for radiofrequency integrated circuits.. More specifically, this disclosure describes techniques for mounting transmit and receive chips to a glass substrate with a thermally conductive path to a heat sink.BACKGROUND

[0003] Radar applications may use millimeter wave radio-frequency integrated circuits (RFICs) for a wide variety of applications, from automotive radar to wireless communication. These RFICs may have a number of different transmit and receive chains integrated onto a single RFIC, that may in turn connect to a plurality of transmit (Tx) and receive (Rx) antennas. This combination of RFICs and antennas may be used to implement a radar detection function that emits wireless signals through the transmit path (including power amplifiers) into the Tx antennas. These wireless signals may then be reflected off of objects in the path of the radar and returned back to the radar unit. These reflected signals may be received through the RX antennas and passed back to the RFIC.

[0004] When used in commercial applications, these millimeter wave RF systems may be exposed to harsh environmental conditions. Existing packaging techniques are primarily configured to protect the delicate components of the RF system. However, these packaging techniques present difficulties in managing the thermal output and thermal dissipation of these components. Therefore, improvements in the art are needed.SUMMARY

[0005] In some embodiments, a radar system may include a waveguide structure; a radiofrequency integrated circuit (RFIC) mounted to the waveguide structure; a printed circuit board (PCB) positioned beneath the RFIC opposite the waveguide structure and comprising a thermally conductive structure adjacent to the RFIC; and a heatsink positioned beneath the PCB, where the thermally conductive structure may be positioned to transfer heat from the RFIC to the heatsink.Attorney Docket No. 080042- 1522031-44025385WO01

[0006] In some embodiments, a method of manufacturing an electromagnetic transmission system may include mounting a radio-frequency integrated circuit (RFIC) to a waveguide structure;forming a thermally conductive pad in or on a printed circuit board (PCB); positioning the PCB beneath the RFIC opposite the waveguide structure such that the thermally conductive pad is adjacent to the RFIC; and positioning a heatsink beneath the PCB such that the thermally conductive pad transfers heat from the RFIC to the heatsink.

[0007] In some embodiments, an electromagnetic transmission system may include a glass waveguide structure that includes an interconnect layer; a redistribution layer including one or more air cavities forming waveguides; and a radiating layer including one or more slot antennas positioned over the waveguides. The system may also include a radio-frequency integrated circuit (RFIC) to mounted to the waveguide structure; and a heatsink thermally coupled to the RFIC through a thermally conductive path of less than 10° C / W.

[0008] In any embodiments, any and all of the following features may be implemented in any combination and without limitation. The RFIC may be mounted to a bottom side of the waveguide structure using a flip-chip orientation such that an active side of the RFIC faces the bottom side of the waveguide structure. The thermally conductive structure may include a thermally conductive pad that is embedded in or on the PCB; and a thermally conductive post that passes through the PCB to contact the thermally conductive pad at a first end of the thermally conductive post and to contact the heatsink at a second end of the thermally conductive post. The thermally conductive pad may be at least 1 mm thick and positioned directly below the RFIC. The thermally conductive pad may extend above a top surface of the PCB and below the top surface of the PCB. The RFIC and the thermally conductive structure may be separated by a gap, and the gap may be filled with a thermal paste to thermally couple the thermally conductive structure with the RFIC. The radar system may also include a radar processing unit mounted to a bottom side of the PCB between the PCB and the heatsink. A cavity may be formed in the PCB in which the thermally conductive pad is formed. A hole may be formed through the PCB beneath a location for the thermally conductive pad. A thermally conductive post may be inserted into the hole to contact the thermally conductive pad, where the thermally conductive post may be connected to the heatsink. An underfill may be applied to the RFIC between the RFIC and the waveguide structure, such that the underfill hermetically seals an area between the RFIC and the waveguide structure. A plurality of pillars may be positioned between the waveguide structure and the PCB such that a gap is maintained between the RFIC and the thermally conductive pad. At least some of the plurality of pillars may be configured to carry electrical signals from the RFIC to the PCB. An area between the waveguide structure and the PCB may be filled to hermetically seal an area between theAttorney Docket No. 080042- 1522031-44025385WO01 waveguide structure and the PCB. The distribution layer may include an embedded waveguide transition structure configured to receive an electrical signal from the RFIC and convert the electrical signal into a propagating EM wave within the waveguides. The heatsink may be thermally coupled to the RFIC via a thermally conductive structure that passes through a PCB positioned such that the RFIC is between the glass waveguide structure and the PCB. The thermally conductive structure may include a thermally conductive slug with a shape that matches a shape of the RFIC. The electromagnetic transmission system may be part of a radar system configured to detect objects in a surrounding environment.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A further understanding of the nature and advantages of various embodiments may be realized by reference to the remaining portions of the specification and the drawings, wherein like reference numerals are used throughout the several drawings to refer to similar components. In some instances, a sub-label is associated with a reference numeral to denote one of multiple similar components. When reference is made to a reference numeral without specification to an existing sub-label, it is intended to refer to all such multiple similar components.

[0010] FIG. 1 illustrates a traditional millimeter wave RF system using patch antennas, according to some embodiments.

[0011] FIG. 2 illustrates a system that uses air waveguides instead of patch antennas, according to some embodiments.

[0012] FIG. 3A illustrates a radar system using a glass waveguide structure with thermal dissipation pathways for the RFICs, according to some embodiments.

[0013] FIG. 3B illustrates a radar system using a glass waveguide structure with the radar processing unit(s) integrated with the RFICs, according to some embodiments.

[0014] FIG. 4 illustrates a view of the glass waveguide structure , according to some embodiments.

[0015] FIG. 5 illustrates a flowchart of a method for manufacturing a radar system, according to some embodiments.

[0016] FIGS. 6A-F illustrate example structures relative to the operations of the method of FIG.5.Attorney Docket No. 080042- 1522031-44025385WO01DETAILED DESCRIPTION

[0017] Described herein are embodiments for a glass substrate architecture for mounting RF components configured for heat dissipation. Existing millimeter wave radiofrequency (RF) systems mount the RFICs on a printed circuit board on the opposite side of a heat sink, making it difficult to dissipate heat away from the RFICs during operation. This architecture mounts the RFICs to a back side of a glass waveguide substrate, and thermally couples the top side of the RFICs to a conductive pad on the underlying printed circuit board with a thermal pathway to the heatsink. This leads to a much more effective dissipation of heat away from the RFICs and eliminates the need for additional cooling systems or throttling the performance of the radar system.

[0018] FIG. 1 illustrates a millimeter wave RF system 100 using patch antennas, according to some embodiments. This system 100 may be implemented in a wide variety of different applications. By way of example, this system may be implemented as an automotive radar system that may be used to identify objects surrounding a motor vehicle. Wireless signals may be emitted from the system 100 that are then reflected off surrounding objects. These reflections may be received by the system 100 and processed to identify objects and object properties, such as size, distance, elevation, relative speed, and so forth. The system 100 may be mounted on an exterior portion of the automobile that faces out into the surrounding environment.

[0019] Note that the architectures and techniques described herein are not limited to automotive applications, but they may instead be used in any similar operating environment. For example, other systems may be subject to similar operating constraints, harsh operating environments, and thermal dissipation concerns. Other applications may include other radar applications, wireless communication, and entertainment systems. For example, augmented reality (AR) and virtual reality (VR) headsets worn by users may be battery-powered and may communicate with a central computing system using millimeter wave or similar RF technologies. Like automotive apl470183plications, AR / VR applications may similarly need to dissipate heat away from the RF components to a heatsink in a manner that does not cause discomfort to the user. Therefore, automotive applications are used only by way of example and are not meant to be limiting.

[0020] The system 100 may include an RF printed circuit board (PCB) 102 that may be used as a primary substrate to which the wireless components may be mounted. In practice, any wireless or RF system will typically benefit from tight integration between the antennas and the RFICs. This tight integration limits the interconnectivity loss between the RFIC inputs and outputs and the TX / RX antennas. The system 100 may include RFICs, such as an RX IC 106 and a TX IC 108Attorney Docket No. 080042- 1522031-44025385WO01 that are mounted directly to the RF PCB 102. Generally, the RX IC 106 and / or the TX IC 108 may include integrated circuit (IC) dies that are configured to handle the modulation and demodulation of RF signals received through the intendants. For example, these ICs may be configured to convert data into RF signals for transmission and vice versa for reception based on a particular protocol (millimeter wave radar, Bluetooth, Wi-Fi, etc.). The RX IC 106 and the TX IC 108 may include an RX die and a TX die, respectively. Additionally, these packages may include other circuitry that may be used in the RX and / or TX transmission chain. For example, these packages may include a full receive / transmit system such as a front end RF IC, or may alternatively include only individual components, such as a power amplifier or modulator.

[0021] To facilitate a tight integration with the RFICs, the RX / TX antennas may be implemented using a plurality of patch antennas 121. Patch antennas are flat, typically rectangular or circular antennas that are mounted or deposited directly on the RF PCB 102. The geometries of the patch antennas 121 may be designed for specific frequency ranges and / or directional radiation patterns. The placement of the patch antennas 121 may be important when optimizing performance of the system 100. For example, the patch antennas 121 illustrated in FIG. 1 face outward from the RF PCB 102 such that the system 100 can be directed outward from, for example, a motor vehicle into the surrounding environment. Traces may be routed on or in the RF PCB 102 between the patch antennas 121, the RX IC 106, and the TX IC 108.

[0022] In the example of FIG. 1, a heatsink 104 may be mounted adjacent to the bottom side of the RF PCB 102. While the RX IC 106, the TX IC 108, and the patch antennas 121 may be mounted or formed on the top side of the RF PCB 102, the bottom side of the RF PCB 102 may include a radar processing unit 112, such as a microprocessor or microcontroller that may decode and process information received through the RFICs. The bottom side of the RF PCB 102 may also include a power management circuit 110 that provides power and ground to the rest of the system 100. The radar processing unit 112 and the power management circuit 110 may be coupled directly to the heatsink 104. Therefore, it is very easy to dissipate power from these bottom-side components into the heatsink 104.

[0023] By comparison, it is very difficult to dissipate power from the RF components mounted on the top side of the RF PCB 102 into the heatsink 104, since heat must pass through the body of the RF PCB 102 and through the components mounted on the bottom side of the RF PCB 102. Therefore, despite the advantages provided by the patch antennas 121 of the system 100, a technical challenge exists when dissipating heat away from the RFICs. Specifically, the RX IC 106 and the TX IC 108 typically generate very high thermal heat signatures, and the physicalAttorney Docket No. 080042- 1522031-44025385WO01 constraints of the system make it difficult to dissipate this heat away from these components. For example, the RF components in the system 100 may be over-molded to protect these components from the environment. Additionally, most applications will not allow for a heatsink to be placed in front of or on top of the RF components. For example, a plastic radome may be placed over the system 100 to protect the RF components, but a heatsink on top of the RF components would greatly limit and interfere with the radar operation. Therefore, most systems using patch antennas either require auxiliary cooling systems or require throttling or duty cycling the operation of the RF components to allow these components to cool down between cycles. These solutions add size and expense to the overall system footprint and / or reduce the performance of the system.

[0024] FIG. 2 illustrates a system 200 that uses air waveguides instead of patch antennas, according to some embodiments. In order to improve the performance of the patch antennas, emerging radar systems are beginning to adopt waveguide antennas and RFICs in copper redistribution layer (RDL) packages. While patch antenna systems are generally low performant and include signal loss and interference due to the copper traces between the antennas, the waveguide antennas are much higher performant with the connections to the waveguide antennas occurring within an air cavity and guided channels. Since the waveguide antennas are contactless and implemented in the waveguide launchers inside the RFIC package, the loss is much lower between the RFICs and the antennas.

[0025] The system 200 may include a heatsink 204 on the backside of the system 200. Instead of using a specialized RF radar PCB, the system may instead use a much less expensive FR4 material since the patch antennas are not mounted to the RF PCB 102. As described above, the radar processing unit 212 and the power management circuit 210 may still be mounted to the bottom side of the radar PCB 202 and may still be thermally coupled to the heatsink 204. An RX package 206 and the TX package 208 may be mounted to the top side of the radar PCB 202.

[0026] Instead of routing the RF signals on the radar PCB 202 from the RFICs into patch antennas, the system 200 may instead launch the RF signals from the RFICs into a waveguide structure that sits above the RFICs. For example, FIG. 2 illustrates a close-up view of the RX package 206. The RX package 206 may include an RX IC 230 that implements the circuitry for modulating the RF signal. The RX IC 230 may be connected to a redistribution layer 237, which is connected to the radar PCB 202 through, for example, copper pads, solder balls, and / or other connection techniques. The redistribution layer 237 may connect the RX signals to auxiliary structures within the RX package 206. Patterns may be formed from copper traces on the top of these auxiliary structures to form waveguide launchers 232 that transform the electrical signalAttorney Docket No. 080042- 1522031-44025385WO01 from the RX IC 230 into a radiating electromagnetic wave that is emitted from the top of the RX package 206. Although not shown explicitly, a similar architecture may be used by the TX package 208.

[0027] A plurality of copper layers may form a waveguide structure 220 that is placed above the RFICs. These copper layers may be held in place by plastic spacers that are secured to the copper layers to maintain spacing and alignment. The waveguide structure 220 may include an interconnect layer 222 that includes openings that are aligned with the RFICs. These openings may couple the electromagnetic (EM) wave emitted from the waveguide launchers 232 into the internal cavities of the waveguide structure 220. The distribution layer 224 may include air cavity waveguides that distribute and route the EM waves to different locations within the structure. A radiating layer 226 may include slots that act as waveguide antennas. These slots may be aligned with the air cavities of the waveguide distribution network on the distribution layer 224, and the geometry / size of the slots may be tuned to radiate specific frequencies in a given direction.

[0028] However, despite the performance improvements form using air cavity waveguides and antennas, the system 200 still suffers from a difficulty in radiating heat generated by the RFICs into the heatsink 204. This problem may even be exacerbated by the addition of the waveguide structure 220 that is placed above the RFICs. The over molding of the RX package 206 also insulates heat and minimizes the amount of heat that can escape through the top side of the system 200. For example, in order for heat to escape from the RX IC 230, the heat must travel through the copper traces in the redistribution layer 237, through the connections of the pads / balls on the bottom side of the RX package 206, through the radar PCB 202 and the ICs mounted to the bottom side of the radar PCB 202, and finally into the heatsink 204. The thermal resistance of this path is relatively high (e.g., approximately 40 C / W to 50 C / W). Another disadvantage of this architecture is that it requires the RFICs to be package in expensive, multi-layer packages that include the redistribution layer 237 and that incorporate the waveguide launchers 232.

[0029] FIG. 3A illustrates a radar system 300 using a glass waveguide structure 320 with thermal dissipation pathways for the RFICs, according to some embodiments. The radar system 300 may be one example of a more general class of electromagnetic transmission systems, which may operate using any frequency. Therefore, the radar, millimeter wave, and other types of EM transmission systems are provided only by way of example and are not meant to be limiting.

[0030] The FR4 material may be used again for the radar PCB 302 since the patch antennas are not mounted to the radar PCB 302. The radar processing unit and the power management circuit may be mounted to the underside of the radar PCB 302. However, instead of mounting the RFICsAttorney Docket No. 080042- 1522031-44025385WO01 to the top side of the radar PCB 302, the RFICs may be mounted directly to a glass waveguide structure 320 that sits above the radar PCB 302. For example, the RX IC 330 and the TX IC 331 may be mounted directly to a bottom side of the glass waveguide structure 320 in a “flip chip” orientation. The opposite sides of the RFICs may be thermally coupled to thermally conductive pads formed on the top side of the radar PCB 302, and these thermally conductive pads may be connected to the heatsink 304 through a thermally conductive pathway.

[0031] FIG. 3 A illustrates an enlarged image of how the RX IC 330 may be mounted to the glass waveguide structure 320. The electrical connections from the RX IC 330 may be connected to metal pads on the bottom side of the glass waveguide structure 320. These connections 362 may be made using solder balls or other mounting techniques. In some embodiments, the RX IC 330 may be mounted using a “flip chip” method where the active side of the die for the RX IC 330 is flipped over so that the active side faces the glass waveguide structure 320. Based on the orientation illustrated in FIG. 3 A, the RFICs may be said to be mounted to a bottom side of the glass waveguide structure 320. The terms “bottom / beneath” and “top / above” may describe the relative position of the components of the system 300 as depicted in FIG. 3A. Once the connections are made between the pads on the RX IC 330 and the corresponding pads on the bottom side of the glass waveguide structure 320, an underfill 360 may be applied, such as an epoxy resin to fill any gap between the RX IC 330 and the glass waveguide structure 320. The underfill 360 may provide mechanical support, moisture protection, and otherwise serve to hermetically seal the active side of the RX IC 330 from the outside environment.

[0032] In contrast to the other architectures described above, this technique can use the die of the RX IC 330 without the more expensive and complex components of the RX package described above. Specifically, this technique does not require any over molding, redistribution layer, and / or launch pad structures to be packaged together with the die for the RX IC 330. Instead, the die for the RX IC 330 may be connected directly to the glass waveguide structure 320. Additionally, the architecture of FIG. 2 left a gap of between 0.5 mm and 1.0 mm between the RX package 206 and the waveguide structure 220. In contrast, this architecture directly connects the RX IC 330 to the glass waveguide structure 320. Thus, this architecture eliminates the need for over-molding or any of the additional circuitry described above.

[0033] The radar PCB 302 may be configured to include thermally conductive pads that are located directly under the location for the RFICs. The radar PCB may be described as being positioned beneath the RFICs opposite the glass waveguide structure 320. In this example, a thermally conductive pad 352 may be positioned on or in the radar PCB 302 directly beneath theAttorney Docket No. 080042- 1522031-44025385WO01 location of the RX IC 330 when the system 300 is assembled. The thermally conductive pad may also be referred to as a thermally conductive slug. The thermally conductive pad, or slug, may be substantially thicker than a contact or mounting pad found on traditional PCB surfaces. More specifically, the thermally conductive pad 352 may be thicker than the copper traces that may be present on the surface of the radar PCB 302. For example, the thermally conductive pad 352 may be between about 0.1 mm thick and about 0.5 mm thick, between about 0.5 mm thick and about 1.0 mm thick, between about 1.0 mm thick and about 1.5 mm thick, between about 1.5 mm thick and about 2.0 mm thick, between about 2.0 mm thick and about 2.5 mm thick, between about 2.5 mm thick and about 3.0 mm thick, between about 3.0 mm thick and about 3.5 mm thick, between about 3.5 mm thick and about 4.0 mm thick, between about 4.0 mm thick and about 4.5 mm thick, between about 4.5 mm thick and about 5.0 mm thick, and / or greater than about 5.0 mm thick. The thickness of the thermally conductive pad 352 may also be defined using any combination of ranges described above (e.g., between about 0.5 mm thick and about 2.0 mm thick). The thickness of the thermally conductive pad 352 may also be defined using any individual value within the ranges described above (e.g., about 1.3 mm thick).

[0034] In some embodiments, the thermally conductive pad 352 may be formed on a top surface of the radar PCB 302. Alternatively, some embodiments the thermally conductive pad 352 may be positioned completely below the top surface of the radar PCB 302. As depicted in FIG. 3 A, some embodiments may embed the thermally conductive pad 352 within the radar PCB 302 with a top surface that extends above the top surface of the radar PCB 302 and a bottom surface that extends below the top surface of the radar PCB 302.

[0035] The thermally conductive pad 352 may have dimensions and / or a geometry that substantially matches the dimensions of the RX IC 330. For example, a thermally conductive pad may be manufactured to be a rectangle that substantially matches a rectangular shape of the corresponding RFIC. For example, a length and width of the thermally conductive pad 352 may be approximately the same as a length and width of the RX IC 330. Other embodiments may allow the thermally conductive pad 352 to be larger or smaller than the RX IC 330 to a certain degree. For example, the length and / or width of a thermally conductive pad may be less than 5% larger or smaller than the corresponding length and / or width of the corresponding RFIC, less than about 7% larger or smaller, less than about 10% larger or smaller, less than about 15% larger or smaller, less than about 20% larger or smaller, less than about 25% larger or smaller, less than about 30% larger or smaller, less than about 35% larger or smaller, less than about 40% larger or smaller, less than about 45% larger or smaller, and / or less than or about 50% larger or smaller. In some embodiments, the thermally conductive pad 352 may have a circular, diamond, hex, or otherAttorney Docket No. 080042- 1522031-44025385WO01 shape, while the RX IC 330 may have a rectangular shape. The thermally conductive pad 352 may be centered underneath the center of the RX IC 330. Alternatively, the thermally conductive pad 352 may have a shape and / or position corresponding to a hottest portion of the RX IC 330. Thus, the thermally conductive pad 352 may be smaller than the RX IC 330 and positioned directly below a hottest portion of the RX IC 330.

[0036] The thermally conductive pad 352 may be positioned adjacent to the RX IC 330 as depicted in FIG. 3A. For example, the conductive pad 352 may be positioned directly beneath the RX IC 330 and separated by a gap as described below. In some embodiments, the RX IC 330 may also not be physically soldered or fixed to the radar PCB 302. Instead, the RX IC 330 may be soldered and / or epoxied to the glass waveguide structure 320 as described above. To make a thermal connection with the thermally conductive pad 352, the RX IC 330 and / or the thermally conductive pad may be coated with a thermal paste 356. Any other alternative material may also be used to form a thermally conductive coupling between the exposed surface of the RX IC 330 and the top surface of the thermally conductive pad 352. However, this connection need not be a rigid physical connection, although some embodiments may optionally create a physical connection between the RX IC 330 and the thermally conductive pad 352 (e.g., solder).

[0037] As described in greater detail below, the bottom surface of the glass waveguide structure 320 may include a metal (e.g., copper) cover that includes a solder mask, metal traces, metal pads, and so forth. In order for the RX IC 330 to communicate with the radar processing unit 312 and to receive power / ground from the power management circuit 310, the electrical connections from the RX IC 330 may be routed through the connections 362 to traces along the bottom surface of the glass waveguide structure 320. These traces may lead to connections for metal pillars 358 that may connect to the assembly of the glass waveguide structure 320 to the radar PCB 302. The signals may travel through the metal pillars 358 into connecting pads on the surface of the radar PCB 302, and the radar PCB 302 may route the signals to the radar processing unit 312 and / or the power management circuit 310.

[0038] The thermally conductive pad 352 may be thermally connected to a thermally conductive post 350. Together, the thermally conductive pad 352 and the thermally conductive post 350 may form a “thermally conductive structure” that may be positioned to transfer heat away from the RFIC to the heatsink 304. The thermally conductive post 350 may extend from the bottom of the thermally conductive pad 352 to a top surface of the heatsink 304. In some embodiments, the thermally conductive post 350 and the thermally conductive pad 352 may be separate pieces that are in physical contact to conduct thermal energy. In some embodiments, the thermallyAttorney Docket No. 080042- 1522031-44025385WO01 conductive post 350 may be connected to the thermally conductive pad 352 using an adhesive, solder, or some other permanent or semi-permanent connection technique. In some embodiments, the thermally conductive post 350 may be formed as a continuous piece with the thermally conductive pad 352. The thermally conductive post 350 and the thermally conductive pad 352 may be formed from any thermally conductive material, such as metals like aluminum, copper, and so forth.

[0039] The thermally conductive post 350 may have any geometrical cross-section. For example, the thermally conductive post 350 may have a square, circular, oval, rectangular, diamond, or other cross-section geometry. A radius or width of the thermally conductive post 350 may be between about 1.0 mm and about 1.5 mm, between about 1.5 mm and about 2.0 mm, between about 2.0 mm and about 2.5 mm, between about 2.5 mm and about 3.0 mm, between about 3.0 mm and about 3.5 mm, between about 3.5 mm and about 4.0 mm, between about 4.0 mm and about 4.5 mm, between about 4.5 mm and about 5.0 mm. The radius or width of the thermally conductive post 350 may also be defined using any combination of ranges described above (e.g., between about 0.5 mm and about 2.0 mm ). The radius or width of the thermally conductive post 350 may also be defined using any individual value within the ranges described above (e.g., about 1.3 mm).

[0040] In some embodiments, the thermally conductive post 350 may have a smaller diameter than the thermally conductive pad 352. For example, the diameter of the thermally conductive post 350 may be between about 5% and about 10% of the diameter of the thermally conductive pad 352, between about 10% in about 25%, between about 25% and about 50%, between about 50% and about 75%, and between about 75% and about 100%.

[0041] The thermally conductive pad 352 and the thermally conductive post 350 may form a direct thermal connection between the RX IC 330 and the heatsink 304. In contrast to the architectures described above, heat can travel directly from the RX IC 330 through the through the thermal paste 356 into the thermally conductive pad 352, down through the thermally conductive post 350, and into the heatsink 304. This thermal pathway has a relatively low thermal resistance compared to the thermal pathways available in previous architectures. This configuration eliminates the need for expensive or bulky cooling systems and allows the system 300 to run more continuously without duty cycling or overheating.

[0042] The height of the metal pillars 358 may depend on the thickness of the RX IC 330 and / or the thickness of the thermally conductive pad 352. The metal pillars 358 may be mounted onto the radar PCB 302 and / or the bottom surface of the glass waveguide structure 320. In someAttorney Docket No. 080042- 1522031-44025385WO01 embodiments, the metal pillars 358 may be inserted into corresponding holes in the radar PCB 302. The height of the metal pillars 358 may be sufficient to leave a small gap between the RX IC 330 and the thermally conductive pad 352. This gap may be filled with the thermal paste 356 or other thermal material. Alternatively, the height of the pillars 358 may be sized such that the RX IC 330 directly contacts the thermally conductive pad 352. The metal pillars 358 may be used to both conduct electrical signals and to provide mechanical stability to the system 300. For example, some of the metal pillars 358 may be electrically disconnected from other signals in the system 300 and only present for structural support. Other metal pillars 358 may provide structural support and route electrical signals.

[0043] The space 363 between the radar PCB 302 and the glass waveguide structure 320 may be filled with a fill material, such as epoxy or any other fill material. This may seal the space 363 between the radar PCB 302 and the glass waveguide structure 320 from the outside environment to protect the internal circuitry.

[0044] Note that the RX IC 330, the thermally conductive pad 352 and the thermally conductive post 350 have been used as representative examples for any RFIC present in the system 300. For example, the TX IC 331, the thermally conductive pad 353, and the thermally conductive post 351 for the TX system may be designed in a similar fashion and may operate as described above for the RX components. The thermal structure may provide a thermal pathway of less than 10 C / W, less than 5 C / W. This may be compared to the previous thermal pathway with greater than 40 C / W.

[0045] FIG. 3B illustrates a radar system 301 using a glass waveguide structure 320 with the radar processing unit(s) integrated with the RFICs, according to some embodiments. The radar system 301 is similar to the reader system 300 of FIG. 3A where like numerals refer to like elements described above. However, in FIG. 3B the radar processing unit 312 may be cointegrated with the RX ICs 330, 331 in single system-on-chip (SoC) packages that may be mounted to the underside of the glass waveguide structure 320. For example, the discrete radar processing unit 312 previously mounted to the underside of the radar PCB 302 may omitted or reduced in functionality, as its processing functions may instead be provided within the SoC package that includes the RX IC 330 and / or the TX IC 331. The remainder of the system 300 may be as described for FIG. 3 A. The SoC package may be placed in the same position as the RX IC 330 as shown in FIG. 3A and may be electrically coupled to the interconnect layer of the glass waveguide structure 320 in a flip-chip orientation, with underfill 360 optionally applied as described above.Attorney Docket No. 080042- 1522031-44025385WO01

[0046] In this configuration, RF signals guided by the glass waveguide structure 320 may be received by the RX IC 330 and digitized and processed by the radar processing unit 312 within the same SoC package. Co-locating the radar processing unit 312 with the RX IC 330 shortens internal interconnects for baseband / digital paths and simplifies routing on the radar PCB 302. This configuration may also lower external I / O pin count and eliminate or reduce high-speed interfaces between a separate RX IC and a separate radar processing unit mounted on the PCB. Signals to and from the SoC package may be routed through the connections 362 to traces on the interconnect layer, and then through pillars 358 to the radar PCB 302 as described for FIG. 3A.

[0047] Thermal dissipation for the co-integrated SoC package may be provided by the same thermally conductive structures described with respect to FIG. 3 A. For example, heat generated by the RX IC 330 and the co-integrated radar processing unit 312 may be conducted into the thermally conductive pad 352 embedded in or on the radar PCB 302, and from there through the thermally conductive post 350 to the heatsink 304.

[0048] Some embodiments may also integrate a processing unit 312 with the TX IC 331 in a single SoC package that is mounted to the underside of the glass waveguide structure 320 at the TX IC location. In this configuration, the TX IC 331 may generate transmit waveforms from signals received from the co-integrated radar processing unit 312. However, any combination and / or placement of radar processing units is compatible with these embodiments. For example, a radar processing unit 312 may be cointegrated with the RX IC 330, a separate radar processing unit 312 may be cointegrated with the TX IC 331, and / or a separate radar processing unit may process signals from both of the RF ICs in any combination. For example, portions of the radar processing unit 312 may be distributed between the RX IC 330 and the TX IC 331 (e.g., initial baseband processing co-integrated with the RX IC 330 and higher-level processing or control functions co-integrated with the TX IC 331), while retaining the same mechanical mounting to the underside of the glass waveguide structure 320 and the same thermal management approach. In all such embodiments, the other components and structures of FIG. 3 A may function as described above.

[0049] FIG. 4 illustrates a view of the glass waveguide structure 320, according to some embodiments. The glass waveguide structure 320 may include a glass core, along with other nonglass components. For example, an interconnect layer 322 may be formed using a non-glass layer (e.g., a copper layer or dielectric layer) that may be placed over a glass core. Therefore, the term “glass waveguide structure” does not imply a structure formed only from glass, but instead may include other materials. The interconnect layer 322 may include metal traces, solder masks, andAttorney Docket No. 080042- 1522031-44025385WO01 other PCB features that may be printed on the interconnect layer 322. As described above, the interconnect layer 322 may include metal traces that route signals from the RX IC 330 and / or the TX IC 331 to locations for the pillars 358 to transmit signals to / from the radar PCB 302. The interconnect layer 322 may also include mounting pads for the RFICs.

[0050] The glass waveguide structure 320 may include a distribution layer 324 that routes the EM waves to the slot antennas. The distribution layer 324 may include embedded waveguide transition structures. For example, instead of using waveguide launchers for the RX IC 330, the glass waveguide structure 320 may include an embedded waveguide transition structure 402. The waveguide transition structure 402 may receive an electrical signal from the RX IC 330 and transform that electrical signal into a propagating wave within the glass waveguide structure 320. The waveguide transition structure 402 may include a copper patch 412 that receives the electric signal routed from a pin on the RX IC 330. The copper patch 412 may begin radiating the signal into a cavity 415. Tapered metal flanges 413 may be included in the waveguide transition structure 402 that amplify the radiating signal into the cavity 415. The EM signal may then be routed through air cavities in the distribution layer 324. In some embodiments, the cavity 415 and the other waveguides in the distribution layer 324 may be surrounded by copper posts 417 that line the edges of the waveguides. For example, the distribution layer 324 may be between about 300 pm and about 600 pm thick (e.g., about 500 pm thick). Holes may be drilled in the distribution layer 324 around the waveguide cavities with a diameter of about 80 pm to about 100 pm. These holes may then be filled with copper or other conductive materials. These copper pillars may connect the interconnect layer 322 and the radiating layer 326 with ground signals. Thus, these copper posts 41 may form a grounded barrier around the waveguide cavities that made guide and channel the radiating EM signals.

[0051] The glass waveguide structure 320 may also include a radiating layer 326. The radiating layer 326 may include slots 408 that act as slot antennas. The slot antennas may direct the propagated EM signals out away from the system 300 and / or receive reflected EM signals back into the system 300 as described above. The shape, number, and dimensions of the slots 408 may be sized based on a predetermined frequency used by the system 300.

[0052] FIG. 5 illustrates a flowchart of a method 500 for manufacturing a radar system, according to some embodiments. Each of the operations in the method 500 may be performed using one or more semiconductor manufacturing chambers, including etch chambers, deposition chambers, lithography chambers, polishing chambers, and so forth. The operations in method 500 may also be performed using systems for assembling printed circuit boards and associatedAttorney Docket No. 080042- 1522031-44025385WO01 components, such as pick-and-place machines, soldering machines, and so forth. FIGS. 6A-F illustrate example structures relative to the operations of the method 500. However, these example structures are not meant to be limiting, and the operations of the method 500 are intended to be broader than the specific examples provided in these structures.

[0053] The method 500 may include mounting an RFIC to a waveguide structure (502). FIG. 6A illustrates an example waveguide structure 320, which may include a radiating layer, a distribution layer, an interconnect layer, and so forth, as described above. The waveguide structure 320 may be a glass waveguide structure as depicted in FIGS. 3A-B. FIG. 6B illustrates how an RFIC, such as the RX IC 330, may be mounted to the waveguide structure 320. As described above, the RFIC may be mounted using solder balls or other mounting techniques in a flip-chip orientation. Optionally, the method may apply an underfill to the RFIC between the RFIC and the waveguide structure 320, such that the underfill hermetically sealed an area between the RFIC and the waveguide structure.

[0054] The method 500 may also include forming a thermally conductive pad in or on a PCB (504). The thermally conductive pad or slug may be formed on top of the PCB 302. For example, a metal slug may be secured to the PCB 302 using an adhesive. Alternatively, the thermally conductive pad or slug may be embedded within the PCB 302. FIG. 6C illustrates how a cavity 602 may be formed in the PCB 302. Some embodiments may also include a thermally conductive post as described above. A hole 604 for the thermally conductive post may also be formed or drilled in the PCB 302.

[0055] FIG. 6D illustrates how the thermally conductive pad or slug may be embedded or formed in the cavity 602. The thermally conductive pad or slug may be inserted into the cavity 602 and secured with an adhesive or solder. Alternatively, the thermally conductive pad 352 may be formed directly in the cavity 602. The bottom of the thermally conductive pad 352 may be exposed through the hole 604.

[0056] The method 500 may further include positioning the PCB beneath the RFIC opposite the waveguide structure such that the thermally conductive pad is adjacent to the RFIC (506). FIG. 6E illustrates how the PCB 302 may be positioned below the waveguide structure 320 with the thermally conductive pad 352 directly beneath (e.g., centered beneath) the RFIC. As described above, pillars 358 may be provided for structural support and for communication between the interconnect layer of the waveguide structure 320 and the PCB 302. A thermally conductive material, such as a thermal paste, may be applied to the RFIC and / or the thermally conductive pad 352 in order to thermally couple these components to each other. Optionally, the area between theAttorney Docket No. 080042- 1522031-44025385WO01 waveguide structure 320 and the PCB 302 may be filled to hermetically seal the area between the waveguide structure 320 and the PCB 302.

[0057] The method 500 may additionally include positioning a heatsink 304 beneath the PCB 302 such that the thermally conductive pad 352 transfers heat from the RFIC to the heatsink 304. In some embodiments, the thermally conductive post 350 may be an integrated part of the heatsink 304. For example, these components may be cast from a single piece of metal or other conductive material. Alternatively, the thermally conductive post may be soldered, screwed, or otherwise adhered to the heatsink 304. The thermally conductive post 350 may be passed through the hole 604 in order to contact the bottom side of the thermally conductive pad 352. Solder, adhesive, or thermally conductive paste may be applied to either the thermally conductive post 350 and / or the thermally conductive pad 352. This may provide a thermally conductive path from the RFIC to the heatsink 304 having a thermal conductivity of less than about 10° C / W.

[0058] It should be appreciated that the specific steps illustrated in FIG. 5 provide particular operations for manufacturing and electromagnetic transmission system according to various embodiments. Other sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments may perform the steps outlined above in a different order. Moreover, the individual steps illustrated in FIG. 5 may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. Furthermore, additional steps may be added or removed depending on the particular applications. Many variations, modifications, and alternatives also fall within the scope of this disclosure.

[0059] As used herein, the terms “about” or “approximately” or “substantially” may be interpreted as being within a range that would be expected by one having ordinary skill in the art in light of the specification. In specific cases, these terms may apply a variation of 10% to a stated value. For example, approximately 10 pm would include a range of between 9 pm and 11 pm.

[0060] In the foregoing description, for the purposes of explanation, numerous specific details were set forth in order to provide a thorough understanding of various embodiments. It will be apparent, however, that some embodiments may be practiced without some of these specific details. In other instances, well-known structures and devices are shown in block diagram form.

[0061] The foregoing description provides exemplary embodiments only, and is not intended to limit the scope, applicability, or configuration of the disclosure. Rather, the foregoing description of various embodiments will provide an enabling disclosure for implementing at least one embodiment. It should be understood that various changes may be made in the function andAttorney Docket No. 080042- 1522031-44025385WO01 arrangement of elements without departing from the spirit and scope of some embodiments as set forth in the appended claims.

[0062] Specific details are given in the foregoing description to provide a thorough understanding of the embodiments. However, it will be understood that the embodiments may be practiced without these specific details. For example, circuits, systems, networks, processes, and other components may have been shown as components in block diagram form in order not to obscure the embodiments in unnecessary detail. In other instances, well-known circuits, processes, algorithms, structures, and techniques may have been shown without unnecessary detail in order to avoid obscuring the embodiments.

[0063] Also, it is noted that individual embodiments may have beeen described as a process which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. Although a flowchart may have described the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed, but could have additional steps not included in a figure. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination can correspond to a return of the function to the calling function or the main function.

[0064] The term “computer-readable medium” includes, but is not limited to portable or fixed storage devices, optical storage devices, wireless channels and various other mediums capable of storing, containing, or carrying instruction(s) and / or data. A code segment or machine-executable instructions may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and / or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc., may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc.

[0065] Furthermore, embodiments may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine readable medium. A processor(s) may perform the necessary tasks.Attorney Docket No. 080042- 1522031-44025385WO01

[0066] In the foregoing specification, features are described with reference to specific embodiments thereof, but it should be recognized that not all embodiments are limited thereto. Various features and aspects of some embodiments may be used individually or jointly. Further, embodiments can be utilized in any number of environments and applications beyond those described herein without departing from the broader spirit and scope of the specification. The specification and drawings are, accordingly, to be regarded as illustrative rather than restrictive.

[0067] Additionally, for the purposes of illustration, methods were described in a particular order. It should be appreciated that in alternate embodiments, the methods may be performed in a different order than that described. It should also be appreciated that the methods described above may be performed by hardware components or may be embodied in sequences of machineexecutable instructions, which may be used to cause a machine, such as a general-purpose or special-purpose processor or logic circuits programmed with the instructions to perform the methods. These machine-executable instructions may be stored on one or more machine readable mediums, such as CD-ROMs or other type of optical disks, floppy diskettes, ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, flash memory, or other types of machine- readable mediums suitable for storing electronic instructions. Alternatively, the methods may be performed by a combination of hardware and software.

Claims

Attorney Docket No. 080042- 1522031-44025385WO01WHAT IS CLAIMED IS:

1. A radar system comprising: a waveguide structure; a radio-frequency integrated circuit (RFIC) mounted to the waveguide structure; a printed circuit board (PCB) positioned beneath the RFIC opposite the waveguide structure and comprising a thermally conductive structure adjacent to the RFIC; and a heatsink positioned beneath the PCB, wherein the thermally conductive structure is positioned to transfer heat from the RFIC to the heatsink.

2. The radar system of claim 1, wherein the RFIC is mounted to a bottom side of the waveguide structure using a flip-chip orientation such that an active side of the RFIC faces the bottom side of the waveguide structure.

3. The radar system of claim 1, wherein the thermally conductive structure comprises: a thermally conductive pad that is embedded in or on the PCB; and a thermally conductive post that passes through the PCB to contact the thermally conductive pad at a first end of the thermally conductive post and to contact the heatsink at a second end of the thermally conductive post.

4. The radar system of claim 3, wherein the thermally conductive pad is at least 1 mm thick and positioned directly below the RFIC.

5. The radar system of claim 3, wherein the thermally conductive pad extends above a top surface of the PCB and below the top surface of the PCB.

6. The radar system of claim 1, wherein the RFIC and the thermally conductive structure are separated by a gap, and the gap is filled with a thermal paste to thermally couple the thermally conductive structure with the RFIC.

7. The radar system of claim 1, further comprising a radar processing unit mounted to a bottom side of the PCB between the PCB and the heatsink.

8. A method of manufacturing an electromagnetic transmission system, the method comprising: mounting a radio-frequency integrated circuit (RFIC) to a waveguide structure;Attorney Docket No. 080042- 1522031-44025385WO01 forming a thermally conductive pad in or on a printed circuit board (PCB); positioning the PCB beneath the RFIC opposite the waveguide structure such that the thermally conductive pad is adjacent to the RFIC; and positioning a heatsink beneath the PCB such that the thermally conductive pad transfers heat from the RFIC to the heatsink.

9. The method of claim 8, further comprising: forming a cavity in the PCB in which the thermally conductive pad is formed.

10. The method of claim 8, further comprising: forming a hole through the PCB beneath a location for the thermally conductive pad.

11. The method of claim 10, further comprising: inserting a thermally conductive post into the hole to contact the thermally conductive pad, wherein the thermally conductive post is connected to the heatsink.

12. The method of claim 8, further comprising: applying an underfill to the RFIC between the RFIC and the waveguide structure, such that the underfill hermetically seals an area between the RFIC and the waveguide structure.

13. The method of claim 8, further comprising positioning a plurality of pillars between the waveguide structure and the PCB such that a gap is maintained between the RFIC and the thermally conductive pad.

14. The method of claim 8, wherein at least some of the plurality of pillars are configured to carry electrical signals from the RFIC to the PCB.

15. The method of claim 14, further comprising filling an area between the waveguide structure and the PCB to hermetically seal an area between the waveguide structure and the PCB.

16. An electromagnetic transmission system comprising: a glass waveguide structure comprising: an interconnect layer; a distribution layer comprising one or more air cavities forming waveguides; andAttorney Docket No. 080042- 1522031-44025385WO01 a radiating layer comprising one or more slot antennas positioned over the waveguides; a radio-frequency integrated circuit (RFIC) to mounted to the waveguide structure; and a heatsink thermally coupled to the RFIC through a thermally conductive path of less than 10° C / W.

17. The electromagnetic transmission system of claim 16, wherein the distribution layer comprises an embedded waveguide transition structure configured to receive an electrical signal from the RFIC and convert the electrical signal into a propagating EM wave within the waveguides.

18. The electromagnetic transmission system of claim 16, wherein the heatsink is thermally coupled to the RFIC via a thermally conductive structure that passes through a printed circuit board (PCB) positioned such that the RFIC is between the glass waveguide structure and the PCB.

19. The electromagnetic transmission system of claim 18, wherein the thermally conductive structure comprises a thermally conductive slug with a shape that matches a shape of the RFIC.

20. The electromagnetic transmission system of claim 16, wherein the electromagnetic transmission system is part of a radar system configured to detect objects in a surrounding environment.

Images