Grounded BGA waveguide interface

Abstract

To improve signal loss in ball grid array (BGA) waveguide interfaces.SOLUTION: A package-waveguide interface 300 includes a package substrate 320 that encapsulates solder balls 314, 318 and an integrated circuit die 305 and that includes signal transmitters 325, 330 that transmit or receive signals on the surface of the package substrate. A BGA includes a set of grounded solder balls arranged as a boundary around the signal transmitters. The interface further includes a printed circuit board (PCB) 310 having a waveguide interface side opposite a secondary waveguide side (3D antenna 360 side), and PCB through-holes 345, 350 that extend from the waveguide interface side to the secondary waveguide side and are perpendicular to the plane of the PCB. The BGA couples the package substrate to the waveguide interface side such that the surface of the package substrate faces the PCB through-holes and the signal transmitters and the PCB through-holes are substantially aligned.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] High-frequency integrated circuits (ICs) generate millimeter-wave signals, such as those used in automotive radar, from approximately 76 gigahertz (GHz) to 81 GHz. In traditional IC packaging, these signals are transitioned to planar transmission lines on a printed circuit board (PCB), for example, via a ball grid array (BGA). Planar transmission lines carry signals from one location on the PCB to another, such as from a signal ball pad to an external waveguide launch. External waveguides can be used to feed three-dimensional (3D) antennas. However, routing high-frequency signals through planar transmission lines increases the complexity and cost of PCB manufacturing and often results in signal power loss. Some ICs use a direct interface between the packaged device and the external waveguide rather than a planar transmission line. However, the direct interface must have low coupling loss, high isolation between signal channels, and be robust to manufacturing and assembly tolerances. Summary of the Invention

[0002] An example device includes a package substrate and a BGA. The package substrate encapsulates an IC die and includes a signal generator on a surface of the package substrate configured to emit or receive a signal. The BGA is attached to the surface of the package substrate and includes a set of grounded solder balls arranged as a boundary around the signal generator on the surface of the package substrate. Some implementations also include a PCB substrate having a waveguide interface side, a secondary waveguide side opposite the waveguide interface side, and a through-hole cavity perpendicular to the plane of the PCB substrate and extending from the waveguide interface side to the secondary waveguide side. The BGA couples the package substrate to the waveguide interface side such that the surface of the package substrate faces the through-hole cavity and such that the signal generator and the through-hole cavity are substantially aligned.

[0003] In some examples, a set of grounded solder balls forms a waveguide interface between the signal emitter and the through-hole cavity. In some implementations, the device further includes an external waveguide coupled to the secondary waveguide side of the PCB substrate such that the external waveguide and the through-hole cavity are substantially aligned. In some implementations, the external waveguide is included in a 3D antenna. In some examples, the set of grounded solder balls is arranged as a circular boundary around the signal emitter and the through-hole cavity, and in other examples, as a rectangular boundary.

[0004] In some implementations, the signal generator is a first signal generator configured to emit or receive a first signal, and the set of grounded solder balls includes a first set of grounded solder balls arranged as a boundary around the first signal generator. The package substrate further includes a second signal generator on the surface of the package substrate configured to emit or receive a second signal, and the BGA further includes a second set of grounded solder balls arranged as a boundary around the second signal generator on the surface of the package substrate. In some examples, the first and second sets of grounded solder balls have at least one grounded solder ball in common, and in other examples, none are common. In some implementations, the first and second sets of grounded solder balls are arranged such that the first and second signals are isolated from each other by a threshold amount.

[0005] For a detailed description of various examples, reference will now be made to the accompanying drawings. [Brief explanation of the drawings]

[0006] [Figure 1] 1 illustrates a direct interface between a packaged radar device, a waveguide, and a 3D antenna.

[0007] [Figure 2] 1 illustrates another direct interface between a packaged radar device, a waveguide, and a 3D antenna.

[0008] [Figure 3] 1 illustrates an example direct interface between a packaged radar device and a 3D antenna via a waveguide interface and a printed circuit board through-hole.

[0009] [Figure 4A] FIG. 1 is an angled top view of an example signal emitter contained within an IC chip package configured to directly interface with a 3D antenna. [Figure 4B] FIG. 1 is a side view of an example signal generator contained within an IC chip package configured to directly interface with a 3D antenna. [Figure 4C] 10 is a simulation plot of the signal through the direct interface. [Figure 4D] 10 illustrates a plot illustrating insertion loss and return loss for a direct interface.

[0010] [Figure 5A] 1 illustrates an example direct interface between a packaged radar device and a 3D antenna with variations in the height of the grounded solder balls. [Figure 5B] 1 illustrates an example direct interface between a packaged radar device and a 3D antenna with variations in the height of the grounded solder balls. [Figure 5C] 1 illustrates a plot showing insertion loss and return loss for different grounded solder ball heights.

[0011] [Figure 6A] 1 illustrates an example layout of a packaged radar device and grounded solder balls. [Figure 6B] 1 illustrates an example layout of a packaged radar device and grounded solder balls. DETAILED DESCRIPTION OF THE INVENTION

[0012] The disclosed IC chip provides an interface to an external waveguide that is robust to manufacturing and assembly tolerances, resulting in high isolation and low insertion loss. The disclosed IC chip includes a radar device with a waveguide interface, which includes an integrated signal generator on a package that encapsulates the IC chip and grounded solder balls disposed as an enclosure around the signal generator on the surface of the package. The grounded solder balls isolate the signal generator and its received or transmitted signal from adjacent signal channels, improving insertion loss between the signal generator and an external waveguide that may couple the IC chip. The grounded solder balls can be included in a BGA that is attached to the package that encapsulates the radar device.

[0013] In some examples, the disclosed device includes a PCB substrate having first and second opposing surfaces and a substrate waveguide between the first and second surfaces, substantially perpendicular to the plane of the PCB substrate. Grounded solder balls couple a package encapsulating the radar device to the first surface of the PCB substrate such that the surface of the package faces the first surface and such that the signal generator and the substrate waveguide are substantially aligned. An external waveguide or external antenna having a waveguide opening can be coupled to the second surface of the PCB substrate. The waveguide interface, the substrate waveguide, and the external waveguide or waveguide opening form a signal channel between the signal generator and the external antenna.

[0014] FIG. 1 illustrates a direct interface between a packaged radar device and a 3D antenna with a waveguide feed. The package-waveguide interface 100 includes a packaged radar device 120 coupled to a PCB substrate 110 by an array of solder balls 115 and a 3D antenna 160 with a waveguide feed. The 3D antenna 160 is placed on the PCB substrate 110 above and around the packaged radar device 120 and is separated from the packaged radar device 120 by a gap 150. The packaged radar device 120 includes an IC die 105 and signal emitters 125 and 130 that emit and / or receive signals to and from the 3D antenna 160. Waveguide openings 185 and 190 reroute, fan out, split, etc., to other portions of the 3D antenna 160, depending on the particular antenna design. Rerouting, fan-outs, splits, etc. are not shown here and do not affect the interface between the waveguide openings 165 and 170 and the signal emitters 125 and 130 on the packaged radar device 120. Only the waveguide openings 185 and 190 of the 3D antenna 160 are shown here, with other portions of the 3D antenna 160 omitted for ease of illustration.

[0015] The signal generator 125 emits and / or receives signals to and / or from a waveguide opening 185 of the 3D antenna 160 via a signal channel 135. The signal channel 135 is comprised of a gap 150 and a waveguide opening 165. The signal generator 130 emits and / or receives signals to and / or from a waveguide opening 190 of the 3D antenna 160 via a signal channel 140. The signal channel 140 is comprised of a gap 150 and a waveguide opening 170. The width of the gap 150 varies due to manufacturing and assembly tolerances, for example, due to variations in the height of the solder balls 115 in the BGA that couple the packaged radar device 120 to the PCB substrate 110.

[0016] Variations in the width of gap 150 can have a significant impact on the performance of package-waveguide interface 100. Isolation between adjacent signal emitters 125 and 130 decreases as the width of gap 150 increases, causing signals from one signal emitter to leak from that signal channel into another signal channel and interfere with signals through adjacent signal channels. Similarly, insertion loss for a signal channel increases as the width of gap 150 increases, degrading signal integrity through the signal channels.

[0017] FIG. 2 illustrates another direct interface between a packaged radar device and a 3D antenna with a waveguide feed. Package-waveguide interface 200 is similar to package-waveguide interface 100 shown in FIG. 1, except that 3D antenna 260 is separated from packaged radar device 220 by interposers 248A-C. During manufacturing, a layer of interposer material is adhered to packaged radar device 220, and both the adhesive and interposer material are selectively removed from over antenna emitters 225 and 230. The resulting adhesive sections 244A-C and interposers 248A-C are separated from 3D antenna 260 by gaps 250.

[0018] Although the interposers 248A-C somewhat mitigate the effects of variation on performance, the width of the gap 250 can still vary enough to affect the performance of the PCB 200, particularly the isolation between the signal channels 235 and 240 and the insertion loss for each signal channel. The additional manufacturing steps for adhering the interposer material to the packaged radar device 220 and selectively removing the adhesive and interposer material over the antenna emitters 225 and 230, as well as the complex assembly for aligning the antenna emitters 225 and 230, the interposers 248A-C, and the waveguide openings 265 and 270, increase the manufacturing cost of the package-waveguide interface 200.

[0019] FIG. 3 illustrates an example direct interface between a packaged radar device and a 3D antenna via a waveguide interface and PCB through-holes. Package-waveguide interface 300 includes a packaged radar device 320 coupled to the waveguide interface side of PCB substrate 310 by an array of solder balls 314 and 318. A 3D antenna 360 is coupled to the secondary waveguide side of PCB substrate 310, opposite from packaged radar device 320. There are no gaps between packaged radar device 320, PCB substrate 310, and 3D antenna 360. Waveguide openings 385 and 390 may be rerouted, fanned out, split, etc., to other portions of 3D antenna 360 based on the particular antenna design. The rerouting, fan-out, split, etc. are not shown here and do not affect the interface between waveguide openings 365 and 370 and signal emitters 325 and 330 on packaged radar device 320. Here, only waveguide openings 385 and 390 of 3D antenna 360 are shown, with other portions of 3D antenna 360 omitted for ease of illustration.

[0020] Packaged radar device 320 includes IC die 305 and signal emitters 325 and 330. As used herein, packaged IC die 305 includes a package substrate on which IC die 305 is mounted. In the case of top-mount flip-chip BGA packaging, IC die 305 is mounted on top of the package substrate, and a mold compound covers the top and sides of IC die 305 and a portion of the package substrate. The mold compound may be plastic, ceramic, resin, or other suitable material for encapsulating IC die 305. In the case of under-mount flip-chip BGA packaging, shown in FIGS. 1 and 2, IC die 305 is mounted on the bottom side of the package substrate on the same side as the BGA and remains exposed, and no mold compound is used.

[0021] Signal emitter 325 is substantially aligned with waveguide opening 385 of 3D antenna 360 and emits and / or receives signals through signal channel 335. Signal channel 335 is comprised of solder balls 318, PCB through holes 345, and waveguide opening 365 in 3D antenna 360. Signal emitter 330 is substantially aligned with waveguide opening 390 of 3D antenna 360 and emits and / or receives signals through signal channel 340. Signal channel 340 is comprised of solder balls 318, PCB through holes 350, and waveguide opening 370 in 3D antenna 360. The BGA package for radar device 320 includes open space above antenna emitters 325 and 330 without the solder balls. The solder balls 318 around the antenna emitters 325 and 330 are grounded and act as a waveguiding structure between the signal emitters 325 and 330 and the PCB through holes 345 and 350 .

[0022] The waveguide structure including the solder balls 318 isolates the signal channels 335 and 340 from each other and from other adjacent signal channels, improving impedance matching between the signal generators 325 and 330 and the 3D antenna 360. The solder balls 318 also reduce insertion loss between the signal generators 325 and 330 and the waveguide openings 385 and 390 of the 3D antenna 360. Because the solder balls 318 act as a waveguide structure between the packaged radar device 320 and the PCB substrate 310, which is directly connected to the waveguide feed of the 3D antenna 360, the performance of the package-waveguide interface 300 does not change significantly based on the width of the gap between the packaged radar device 320 and the 3D antenna 360. Additionally, the PCB 300 does not include additional components, such as interposers 248A-C, and can be manufactured without additional manufacturing steps, such as gluing on intervening materials or selectively removing adhesive and intervening materials on the antenna generators.

[0023] 4A-4D illustrate angled top and side views of an example signal generator included in an integrated circuit (IC) chip package configured to directly interface with a 3D antenna, as well as simulation plots of signals through the direct interface and plots illustrating insertion loss and return loss for the direct interface. FIG. 4A illustrates an angled top view of an example IC package 400 including an "E"-shaped signal generator 425. A signal trace 440 carries a signal to the signal generator 425. Ground vias 430 create a substrate integration cavity around the generator, improving isolation between the signal generator 425 and other generators and components on the IC package 400. Grounded solder balls 418 on the surface of the IC package 400 are positioned as a boundary around the signal generator 425 and are configured to couple the IC package 400 to a PCB substrate.

[0024] FIG. 4B shows a side view of an example IC package 400 coupled to a PCB substrate 410. The grounded solder balls 418 and signal emitter 425 are aligned with PCB through-hole cavities 435, which act as waveguides through the PCB substrate 410. During fabrication and assembly, the grounded solder balls 418, through-hole cavities 435, and antenna emitter 425 are aligned. FIG. 4C shows a simulated plot of the signal through the grounded solder balls 418 and through-hole cavities 435. The electromagnetic field strength is indicated by the shaded region. The electromagnetic field plot shows a well-matched transition from the signal emitter 425 to the PCB through-hole cavities 435, with very little signal leakage within the IC package 400 or within the region between the packaged radar device and the PCB coupled by the grounded solder balls 418.

[0025] The waveguide interface formed by the grounded solder balls 418 around the signal generator 425 contains the signal and reduces signal leakage between the signal generator 425 and the PCB through-hole cavity 435. Figure 4D shows a plot of insertion loss 492, antenna side 494 return loss, and waveguide side 496 return loss in decibels (dB) over the frequency range of 72 to 84 GHz. The direct interface shown in Figure 4B produces an insertion loss of approximately 1 dB and a bandwidth of approximately 7.8 GHz.

[0026] 5A-5C illustrate side views of an example direct interface between a packaged radar device and a 3D antenna with variations in grounded solder ball heights, and plots showing insertion loss and return loss for different grounded solder ball heights. FIG. 5A illustrates an example direct interface 500A in which an IC package 510 is coupled to a PCB substrate 520 by grounded solder balls 518A having a height 20% lower than the height of the grounded solder balls 418 shown in FIGS. 4A-4B. FIG. 5B illustrates an example direct interface 500B in which an IC package 510 is coupled to a PCB substrate 520 by grounded solder balls 518B having a height 20% higher than the height of the grounded solder balls 418 shown in FIGS. 4A-4B. The variation in height between the grounded solder balls 418, 518A, and 518B illustrates possible manufacturing variations in the grounded solder balls.

[0027] Figure 5C shows plots of insertion loss 492, antenna-side return loss 494, and waveguide-side return loss 496 from Figure 4D, with insertion loss 592A, antenna-side return loss 594A, and waveguide-side return loss 596A for direct interface 500A shown in Figure 5A, and insertion loss 592B, antenna-side return loss 594B, and waveguide-side return loss 596B for direct interface 500B shown in Figure 5B. As the overlapping plots show, variation in height between grounded solder balls 418, 518A, and 518B does not substantially affect the insertion loss or bandwidth of the direct interface.

[0028] 6A-6B illustrate example layouts of a packaged radar device and grounded solder balls. The packaged radar device can include any number of signal generators having various shapes and arrangements. FIG. 6A illustrates an example layout 600 of rectangular signal generators 610A-G and grounded solder balls 620 around each signal generator. The signal generators 610A-G are positioned close together so that some of the grounded solder balls 620 are included in the boundary around multiple signal generators. Solder balls 630 are included in the BGA package for the IC chip containing the antenna generators 610A-G and may be grounded or may carry a signal. Both the grounded solder balls 620 and the solder balls 630 are configured to couple the IC die to a PCB substrate.

[0029] FIG. 6B illustrates an example layout 650 of signal generators 660A-G and grounded solder balls 670 arranged on a circular boundary around each signal generator. The circular boundary can be used with designs having circular PCB through-hole cavities. In layout 650, signal generators 660A-G can be circular or rectangular in shape. Grounded solder balls 670 are arranged circularly around each signal generator such that the cross-sectional shape of the corresponding signal channel is defined by the grounded solder balls 670 that partition the transmitted or received signal around signal generators 660A-G. Similar to layout 600 shown in FIG. 6A, grounded solder balls 670 can be shared between boundaries around multiple signal generators 660A-G and included with solder balls 680 in a BGA package for an IC die including signal generators 660A-G, configured to couple the IC die to a PCB substrate.

[0030] The term "couple" is used throughout this specification. This term may encompass a connection, communication, or signal path that enables a functional relationship consistent with the description of this disclosure. For example, in a first example, device A is coupled to device B when device A generates a signal to control device B to perform a certain operation, or in a second example, device A is coupled to device B through an intervening component C such that device A controls device B through a control signal generated by device A, where intervening component C does not substantially change the functional association between device A and device B. Unless otherwise specified, as used herein, "matched" or "substantially matched" means that two things are 90% or more matched to each other.

[0031] Modifications may be made to the exemplary embodiments described, and other embodiments are possible, within the scope of the claims of the invention.

Claims

1. A device, a package substrate encapsulating an integrated circuit (IC) die, the package substrate including a signal emitter on a surface of the package substrate configured to emit or receive a signal; a ball grid array (BGA) attached to the surface of the package substrate and including a set of grounded solder balls arranged as a boundary around the signal generator on the surface of the package substrate; Including, the device.

2. 10. The device of claim 1, Further comprising a printed circuit board (PCB) substrate, the PCB substrate comprising: a waveguide interface side; a secondary waveguide side opposite the waveguide interface; a through-hole cavity perpendicular to the plane of the PCB substrate and extending from the waveguide interface side to the secondary waveguide side; and a BGA coupling the package substrate to the waveguide interface side such that the surface of the package substrate faces the through-hole cavity and such that the signal emitter and the through-hole cavity are substantially aligned.

3. 3. The device of claim 2, The device wherein the set of grounded solder balls forms a waveguide interface between the signal emitter and the through-hole cavity.

4. 3. The device of claim 2, The device further includes an external waveguide coupled to the secondary waveguide such that the external waveguide and the through-hole cavity are substantially aligned.

5. 5. The device of claim 4, The device, wherein the external waveguide is included in a three-dimensional antenna.

6. 3. The device of claim 2, A device wherein the set of grounded solder balls are arranged as a circular boundary around the signal emitter and the through-hole cavity.

7. 3. The device of claim 2, A device wherein the set of grounded solder balls are arranged as a rectangular boundary around the signal emitter and the through-hole cavity.

8. 10. The device of claim 1, the signal emitter includes a first signal emitter configured to emit or receive a first signal; the set of grounded solder balls includes a first set of grounded solder balls arranged as a boundary around the first signal generator; the package substrate further includes a second signal emitter on the surface of the package substrate configured to emit or receive a second signal; The device, wherein the BGA further includes a second set of grounded solder balls arranged as a boundary around the second signal emitter on the surface of the package substrate.

9. 9. The device of claim 8, the first set of grounded solder balls and the second set of grounded solder balls have at least one grounded solder ball in common.

10. 9. The device of claim 8, the first set of grounded solder balls and the second set of grounded solder balls do not have a common grounded solder ball.

11. 9. The device of claim 8, the first and second sets of grounded solder balls are positioned such that the first and second signals are isolated from each other by a threshold amount.

12. 1. A printed circuit board (PCB), comprising: a PCB substrate having a first surface and a second surface opposite the first surface, the PCB substrate further having a through-hole cavity from the first surface to the second surface; an integrated circuit (IC) package substrate including a signal generator thereon; a waveguide interface including a set of grounded solder balls, the waveguide interface coupling the IC package substrate to the first surface of the PCB substrate such that the surface of the IC package substrate faces the first surface of the PCB substrate; an external antenna including a waveguide and coupled to the second surface of the PCB substrate; a signal channel between the signal emitter and the external antenna; Including, The signal channel is the waveguide interface; the through-hole cavity; the waveguide; Including, a PCB in which the signal generator, the through-hole cavity, and the waveguide are substantially aligned, and the cross-sectional shape of the signal channel is defined by an enclosure around the signal generator including the set of grounded solder balls.

13. 13. The PCB of claim 12, a ball grid array (BGA) attached to the surface of the IC package substrate, coupling the IC package substrate to the first surface of the PCB substrate; a PCB, wherein the BGA includes the waveguide interface;

14. 13. The PCB of claim 12, A PCB wherein the signal channel has a circular cross-sectional shape, and the set of grounded solder balls is disposed within a circular enclosure around the signal emitter.

15. 13. The PCB of claim 12, A PCB in which the signal channel has a rectangular cross-sectional shape, and the set of grounded solder balls is disposed within a rectangular enclosure around the signal emitter.

16. 13. The PCB of claim 12, the PCB substrate further includes a second through-hole cavity from the first surface to the second surface; the IC package substrate further includes a second signal emitter on the surface of the IC package substrate; the external antenna further includes a second waveguide; The PCB further comprises: a second waveguide interface including a second set of grounded solder balls; a second signal channel between the second signal generator and the external antenna; Including, the second signal channel includes the second waveguide interface, the second through-hole cavity, and the second waveguide; the second signal generator, the second through-hole cavity, and the second waveguide are substantially aligned; a PCB, wherein the cross-sectional shape of the second signal channel is defined by an enclosure around the second signal emitter including the second set of grounded solder balls;

17. An integrated circuit (IC) chip comprising: a radar device including a signal emitter on a surface thereof; a waveguide interface including a set of grounded solder balls arranged as an enclosure around the signal emitter on the surface of the radar device; An IC chip including:

18. 18. The IC chip according to claim 17, The waveguide interface defines a cross-sectional shape of a signal channel corresponding to the signal emitter.

19. 18. The IC chip according to claim 17, The IC chip further includes a ball grid array (BGA) package that encapsulates the radar device, the set of grounded solder balls included in the waveguide interface.

20. 18. The IC chip according to claim 17, the IC chip is bonded to a PCB substrate; The PCB substrate is a first surface; and a second surface opposite the first surface; and a substrate through-hole waveguide from the first surface to the second surface; and an IC chip, wherein the set of grounded solder balls couples the radar device to the first surface such that the surface of the radar device faces the first surface and such that the signal emitter and the substrate through-hole waveguide are substantially aligned;

21. 21. The IC chip of claim 20, an external antenna coupled to the second surface of the PCB substrate and including a waveguide aperture, the waveguide interface, the substrate through-hole waveguide, and the waveguide aperture forming a signal channel between the signal emitter and the external antenna;

22. 22. The IC chip of claim 21, An IC chip wherein the cross-sectional shape of the signal channel is defined by a set of grounded solder balls arranged as the enclosure around the signal emitter.

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