MMIC ETL Ground Shielding for RF Coupling Isolation
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Solution Overview
Problem
The increasing miniaturization of radio frequency (RF) integrated circuits (ICs) in mobile devices leads to unwanted electromagnetic (EM) coupling with nearby metal features in the package or next higher assembly, affecting the performance of high-frequency RF circuits, especially above 2 GHz, due to fanout-style packaging technologies like fanout wafer-level packaging (FOWLP) or fanout panel-level packaging (FOPLP).
Innovation Solution
A monolithic microwave integrated circuit (MMIC) with embedded transmission line (ETL) ground shielding is introduced, featuring a topside ground plane over an ETL dielectric layer to reduce EM coupling between the RF transmission lines and external circuit assemblies, while also facilitating improved thermal paths for heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fanout-style packaging (FOWLP/FOPLP) is used to achieve high-density packaging, then packaging density is improved, but electromagnetic coupling between RF transmission lines and external metal features increases
Solution Approach 1:
An embedded transmission line (ETL) structure with dielectric material is introduced as an intermediary between the RF transmission lines and external metal features. The dielectric layer acts as a mediator that blocks electromagnetic field coupling while allowing signal transmission, thus reducing harmful EM coupling without sacrificing packaging density.
Solution Approach 2:
The transmission lines are embedded within the dielectric material, creating a nested structure where the conductive elements are contained within an insulating matrix. This nesting approach allows the RF lines to be protected from external electromagnetic interference while maintaining compact packaging.
2Volume of moving object
If miniaturization of RF ICs is pursued to reduce device size, then device dimensions are reduced, but susceptibility to electromagnetic coupling from nearby metal features increases
Solution Approach 1:
A thin dielectric layer is used to embed and protect the transmission lines. This thin film approach provides electromagnetic shielding while maintaining compact dimensions, allowing miniaturization without increasing susceptibility to EM coupling.
Solution Approach 2:
The dielectric material serves as an intermediary barrier that prevents direct electromagnetic interaction between miniaturized RF components and nearby metal features, enabling smaller device sizes while maintaining RF performance.
3Area of stationary object
If RF circuits are placed close to external metal features to achieve compact packaging, then packaging area is reduced, but RF circuit performance is degraded due to EM coupling
Solution Approach 1:
The dielectric material acts as an intermediary shield that allows RF circuits to be placed close to external metal features without performance degradation. The dielectric blocks harmful EM coupling while permitting the compact layout required for small packaging area.
Solution Approach 2:
The transmission lines are nested within the dielectric structure, creating a protected configuration that maintains RF performance even when positioned close to external metal features, thus enabling compact packaging without sacrificing reliability.
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 ETL ground shielding effectively decouples RF circuits from external metal structures, enhancing performance and allowing for high-density packaging without compromising RF circuit integrity, and improves thermal management by providing additional heat dissipation paths.
Implementation Method 1
an ETL dielectric layer disposed at least partially over the active side of the MMIC substrate and surrounding the transmission line
Implementation Method 2
a topside ground plane disposed over the ETL dielectric layer and configured to reduce EM coupling between the transmission line of the active side and an external circuit assembly
Implementation Method 3
The topside ground plane can also facilitate improved thermal paths for heat dissipation
Data Source
AI summary
A monolithic microwave integrated circuit (MMIC) with embedded transmission line (ETL) ground shielding is provided. In an exemplary aspect, an ETL MMIC according to this disclosure includes a MMIC substrate having an active side, an ETL dielectric layer covering the active side, and a topside ground plane over the ETL dielectric layer. The active side includes one or more transmission lines or other components which may undesirably couple to metal signal lines (e.g., package metal interconnects) in an external circuit assembly. The topside ground plane in the ETL MMIC provides shielding to reduce such electromagnetic coupling. The topside ground plane can also facilitate improved thermal paths for heat dissipation, such as through a redistribution layer (RDL) to a next higher assembly (NHA) and/or through a backside ground plane of the MMIC substrate.