Cavity PCB Structure for Lower Dielectric Loss in RF Transmission
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Solution Overview
Problem
Conventional PCBs experience significant dielectric loss during high-speed signal transmission, affecting signal transmission rate and quality, particularly in communication antennas, necessitating a reduction in dielectric loss to enhance performance.
Innovation Solution
The PCB design incorporates a substrate with cavities and a filler material that reduces dielectric constant and loss, featuring a copper foil bonded by a bonding layer with conductive metal plating and through holes for interconnectivity, ensuring the filler is in a closed environment to maintain mechanical stability and electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional PCB materials are used, then manufacturing cost is controlled, but dielectric loss is high which affects signal transmission quality
Solution Approach 1:
The patent uses a composite substrate structure combining PTFE (polytetrafluoroethylene) and air cavity regions. The PTFE material provides low dielectric loss properties (Df≤0.002) while the air cavity regions reduce the overall dielectric constant. This composite approach achieves superior RF performance compared to conventional single-material PCBs while maintaining cost-effectiveness through optimized material usage.
Solution Approach 2:
The substrate incorporates air cavity regions that create a porous or hollow structure within the PCB. These air-filled cavities reduce the effective dielectric constant of the substrate (Dk≤2.2) and contribute to lowering dielectric loss. The porous/air-filled design allows electromagnetic waves to propagate with minimal energy loss while keeping manufacturing costs reasonable.
2Reliability
If dielectric loss is reduced to improve signal transmission, then signal transmission quality improves, but substrate structure complexity increases
Solution Approach 1:
The substrate is segmented into distinct regions: PTFE material regions with low dielectric loss and air cavity regions with minimal dielectric constant. This segmentation allows each region to contribute its optimal properties to the overall PCB performance. The segmented design achieves superior signal transmission quality (Df≤0.002) while the modular structure can be manufactured using standard PCB fabrication techniques, limiting complexity increase.
Solution Approach 2:
Different regions of the substrate are assigned different material properties: PTFE regions provide low dielectric loss for signal integrity, while air cavity regions provide low dielectric constant for impedance control. This local differentiation of material quality allows the PCB to optimize RF performance in specific areas without requiring complete structural redesign, thus improving signal transmission quality while managing overall structure complexity.
3Adaptability or versatility
If device density is increased to improve functionality, then functional extensibility improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes the vertical dimension by creating through-holes that penetrate the substrate and bonding layers, enabling multi-layer interconnections. This three-dimensional approach to circuit routing allows higher device density and functional extensibility without requiring proportionally increased planar manufacturing precision. The through-hole plating and multi-layer stacking enable complex functionality while using established manufacturing processes.
Solution Approach 2:
The PCB structure employs nested layers with copper foils and bonding layers stacked vertically, creating a multi-layer configuration. Through-holes provide vertical interconnections between layers, enabling compact integration of multiple functional elements. This nested, multi-layer design achieves high functional extensibility and device density while relying on standard precision manufacturing capabilities for each individual layer and connection point.
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
This design effectively lowers dielectric constant and loss, improving radio frequency performance, enabling higher device integration and stability while maintaining cost-effectiveness.
Implementation Method 1
the copper foil is bonded to the substrate by using the bonding layer
Implementation Method 2
an outer surface of the copper foil is plated with a conductive metal layer
Implementation Method 3
a hole wall of the through hole is plated with a conductive metal layer
Data Source
AI summary
A printed circuit board, which may be included an electronic communication device, includes a substrate, a bonding layer, a copper foil, and a filler. The substrate is provided with a cavity, and the cavity penetrates through the substrate. Two surfaces of the substrate are covered with the copper foil. The copper foil is bonded to the substrate by using the bonding layer. An outer surface of the copper foil is plated with a conductive metal layer. The filler is located inside the cavity. The substrate is provided with a through hole, and the through hole penetrates through the substrate and the bonding layer. A hole wall of the through hole is plated with a conductive metal layer. In this application, a dielectric constant Dk and a dielectric loss Df of the printed circuit board can be effectively reduced, and cost control is ensured.