Leveraging Modularity of Chiplets to Form a 4×4 Automotive FMCW-Radar in an eWLB-Package

By Pascal Stadler ¹; Jan Schoepfel ²; Lars Kleditsch ³; Christian Geissler ⁴; Reinhold Herschel ⁵; Ram K. Arumugam ², Patrick Wallrath ², Klaus Aufinger ⁶, Steffen Paul ³, Nils Pohl ^1,2 and Tobias T. Braun ^1
1 Institute of Integrated Systems, Ruhr University Bochum, 44801 Bochum, North-Rhine Westphalia, Germany
² Fraunhofer Institute, FHR, 53343 Wachtberg, North-Rhine Westphalia, Germany
³ Institute of Theoretical Electronic and Microelectronic, University Bremen, 28334 Bremen, Germany
⁴ Infineon Technologies AG, IFX, 93049 Regensburg, Baveria, Germany
⁵ WavesenseDD GmbH, 01069 Dresden, Saxony, Germany
⁶ Infineon Technologies AG, IFX, 93049 Neubiberg, Baveria, Germany

Abstract:

Dividing a System on Chip (SoC) into multiple smaller chiplets and embedding them into a single package has gained significant traction in recent years through more widespread adoption in digital circuitry. Despite benefits of reduced interference, protection against environmental influences and overcoming the “Interconnection Gap”, its usage in integrated analog circuits fails to match pace with digital designs. Adoption is likely impeded by an over-reliance on single-chip packages as they prioritize high-frequency performance over integration densities. We therefore demonstrate the first modular system approach with an embedded Wafer-Level Ball grid array (eWLB) package that does not compromise on either integration density nor performance. Restricted only by the maximum package dimensions, the number of channels can be adjusted application-specifically. This allows the system to scale down for low-cost, low-power applications while conversely facilitating massive MIMO. Exemplarily, a 4 × 4 radar System in Package (SiP) with five 130 nm B11HFC SiGe chiplets in a small form factor of 7.8 mm × 8.8 mm was manufactured for this work. It contains a central VCO that feeds four transceivers of identical design that can be configured as receivers or transceivers through the package’s layout. The configuration is solely package-based, enabling chip designs to be reused and thus drastically reducing development time. It also permits homogeneous or heterogeneous substitution of the chiplets based on available fabrication facilities and economic considerations. With its 15.6 dBi comb-line antennas, target detection within 76–77 GHz has been verified up to 36 m in range and ±30° in azimuth. Adverse to single-chip solutions, this novel chiplet approach splits up temperature hotspots into smaller, localized areas of elevated temperature. While advantageous for the dissipation of heat, it imposes additional challenges thermomechanically as well as electromagnetically. The compromise between performance and reliability is therefore addressed with a detailed examination of the solderball placement and package-to-PCB interfaces.

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