Single Layer RFIC Package Grounded Coplanar Transmission Line Shielding
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Solution Overview
Problem
High-frequency RF circuits in automotive radar systems, particularly those operating at 80 GHz, face challenges with electromagnetic energy coupling from nearby structures, leading to performance degradation due to increasing complexity and size reduction of integrated circuit packages.
Innovation Solution
A single layer RFIC package with a redistribution layer (RDL) and low loss grounded coplanar transmission lines is developed, featuring a conductive ground shield and solder ball transitions to minimize electromagnetic interference, allowing efficient signal transmission between RFIC chips and antennas while providing an electrical return path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If integrated circuit packages are reduced in size to meet miniaturization requirements, then device compactness is improved, but electromagnetic energy coupling from nearby structures increases causing performance degradation
Solution Approach 1:
A ground shield structure is introduced as an intermediary element between the RF transmission lines and surrounding structures. This ground shield acts as a mediator that blocks electromagnetic coupling paths, preventing harmful energy coupling while allowing the package to maintain compact dimensions. The ground shield is connected to the RF ground plane through multiple vias, creating a protective barrier that isolates the sensitive RF signals from external electromagnetic interference.
Solution Approach 2:
The ground shield is implemented as a thin conductive layer or film structure that can be integrated into the compact package design. This thin film approach provides effective electromagnetic shielding without adding significant volume to the package, thus maintaining miniaturization while protecting against harmful electromagnetic coupling.
2Reliability
If ground shields are added to reduce electromagnetic interference, then signal integrity is improved, but manufacturing complexity increases
Solution Approach 1:
The ground shield structure is merged with the existing RF ground plane and via structure. By combining the ground shield function with the existing grounding infrastructure, the design achieves effective electromagnetic shielding without requiring completely separate manufacturing processes. The ground shield shares vias and ground connections with the RF ground plane, reducing the number of discrete components and simplifying assembly.
Solution Approach 2:
The ground shield structure serves multiple functions simultaneously: it provides electromagnetic shielding, maintains ground reference for RF signals, and acts as a mechanical support structure. This multi-functionality reduces the need for additional dedicated shielding components, thereby simplifying the overall manufacturing process while maintaining signal integrity.
3Reliability
If multiple layers are used to achieve low loss transmission, then signal quality is improved, but device complexity and cost increase
Solution Approach 1:
The ground shield is extracted as a separate functional element that can be independently optimized and manufactured. By extracting the shielding function from the multi-layer stack-up, the design achieves low-loss transmission without requiring complex multi-layer constructions. The ground shield can be implemented as a simple conductive layer or pattern that provides the necessary protection while maintaining a relatively simple layer structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves high performance with reduced manufacturing complexity and cost, maintaining signal integrity at 77-81 GHz frequencies, essential for reliable automotive radar systems.
Implementation Method 1
A conductive ground shield is fabricated on the single redistribution layer and operative to shield the plurality of coplanar RF transmission lines
Implementation Method 2
A plurality of coplanar RF transmission lines are fabricated on the single redistribution layer and are operative to conduct the RF output signals from the RFIC die to a first side of the printed circuit board via signal solder ball transitions
Implementation Method 3
The plurality of ground solder balls surround the plurality of coplanar RF transmission lines and signal solder ball transitions, and are operative to couple the ground shield to the ground plane on the printed circuit board and provide an electrical return path for the plurality of coplanar RF transmission lines
Data Source
AI summary
A novel and useful a single layer RFIC/MMIC structure including a package and related redistribution layer (RDL) based low loss grounded coplanar transmission line. The structure includes a package molded around an RF circuit die with a single redistribution layer (RDL) fabricated on the surface thereof mounted on an RF printed circuit board (PCB) via a plurality of solder balls. Coplanar transmission lines are fabricated on the RDL to conduct RF output signals from the die to PCB signal solder balls. The signal trace transition to the solder balls are funnel shaped to minimize insertion loss and maximize RF isolation between channels. A conductive ground shield is fabricated on the single RDL and operative to shield the plurality of coplanar transmission lines. The ground shield is electrically connected to a ground plane on the PCB via a plurality of ground solder balls arranged to surround the plurality of coplanar RF transmission lines and signal solder balls, and are operative to couple the ground shield to the ground plane on the PCB and provide an electrical return path for the plurality of coplanar transmission lines. Ground vias on the printed circuit board can be either located under the ground solder balls or between them.