RF Interposer with Spring Finger Grounds for PWB Interconnection
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Solution Overview
Problem
Existing methods for interconnecting large-area printed wiring boards (PWBs) in phased array antennas are costly and time-consuming, particularly when using solder connections or 'fuzz buttons', and are not suitable for high-power applications, while existing connectors like conductive elastomeric pads are not suitable for high-power use.
Innovation Solution
An RF interposer with embedded coaxial transmission lines in a metal carrier structure, featuring spring finger ground planes for blind-mate connections across air-gaps between PWBs, reducing the need for multilayer assemblies and providing low-loss, well-isolated RF transmission lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder connections or fuzz buttons are used to interconnect large-area PWBs, then reliable electrical connection is achieved, but manufacturing cost and assembly time increase significantly
Solution Approach 1:
The invention divides the interconnection system into modular units with standardized RF interposer components. Each PWB assembly is segmented into discrete units that can be independently manufactured and then quickly assembled using the simplified interposer interface, reducing overall assembly complexity and time while maintaining connection reliability.
Solution Approach 2:
The RF interposer acts as an intermediary component between PWB assemblies, providing a standardized interface that simplifies the interconnection process. The interposer with its embedded coaxial transmission lines and ground plane structures serves as a mediator that enables reliable RF signal transmission without requiring complex solder connections or fuzz buttons, thereby reducing assembly time and cost.
2Reliability
If traditional connectors are used for PWB interconnection, then electrical connection is established, but manufacturing cost increases due to expensive connectors and bullets
Solution Approach 1:
The invention extracts the essential interconnection function from expensive traditional connectors and bullets, implementing it directly through integrated RF interposer structures. By removing the need for separate connector components and replacing them with embedded coaxial transmission lines and spring finger ground planes, the design achieves reliable connection at lower manufacturing cost.
Solution Approach 2:
The RF interposer uses cost-effective materials and structures such as spring finger ground planes made from conductive elastomeric material instead of expensive traditional connectors. These components are designed to be economical while maintaining sufficient reliability for the application, reducing overall manufacturing cost.
3Ease of manufacture
If conductive elastomeric pads are used for connection, then assembly is simplified, but high-power applications are not supported
Solution Approach 1:
The invention merges the advantages of conductive elastomeric materials with traditional rigid connector structures. The spring finger ground planes use conductive elastomeric material for simplified assembly and tolerance compensation, while the embedded coaxial transmission lines and metal carrier structure provide the necessary power handling capability, combining both simplicity and high-power support.
Solution Approach 2:
The RF interposer employs composite structures combining conductive elastomeric material for the spring finger ground planes with rigid metal carrier structures and embedded coaxial transmission lines. This composite approach allows the flexible elastomeric portion to provide assembly simplicity and tolerance compensation, while the rigid metal portions handle high-power RF signals effectively.
4Device complexity
If large-area multilayer PWB assemblies are used, then all RF ports are integrated in one board, but manufacturing complexity and cost increase
Solution Approach 1:
The invention segments the large-area multilayer PWB assembly into multiple smaller, simpler PWB units connected through standardized RF interposers. Each individual PWB can be manufactured more easily with fewer layers and components, while the interposers provide the necessary RF interconnection, reducing overall manufacturing complexity and cost while maintaining the integrated functionality.
Solution Approach 2:
The RF interposer serves as an intermediary that enables the distribution of RF ports across multiple simpler PWB assemblies. Instead of requiring one complex multilayer board, the interposers facilitate interconnection between multiple simpler boards, reducing manufacturing complexity while achieving the same level of RF port integration.
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 RF interposer enables reliable, cost-effective RF interconnection across multiple ports, supporting high power applications and reducing assembly complexity, while eliminating the need for expensive connectors and improving reliability in AESA systems.
Implementation Method 1
a ground plane having spring fingers to make electrical contact across air-gaps between a PWB RF ground plane and a ground plane of the RF interposer
Implementation Method 2
an RF interposer structure having a plurality of coaxial transmission line connections embedded in metal (or metallized) carrier structures enables blind-mate RF interconnection
Data Source
Figure 1
Figure 1A
Figure 2
AI summary
An radio-frequency (RF) interposer enables low-cost, high-performance RF interconnection of two or more large-area printed wiring boards (PWBs). The RF interposer may be provided as a multi-port coaxial structure embedded in a metal (or metalized) earner. The RF interposer may include one or more conductive shims having spring fingers to provide contact across air-gaps between a PWB RF ground plane and a ground plane of the RF interposer. Retractable pins may be used as the coaxial transmission line center conductors. The RF interposer may be provided as an NxM grid of unit cells each having one or more RF ports and a cavities to provide clearance for a PWB component.