Compliant Cable Termination for Controlled-Impedance PCB Interfaces
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Solution Overview
Problem
Conventional cable terminations often experience impedance mismatches and signal reflections due to permanent mechanical connections, which limit bandwidth and introduce signal integrity issues at the interface between cables and printed circuit boards (PCBs).
Innovation Solution
The development of a controlled-impedance cable termination system using compliant contacts that can mate directly with conductive pads on an electrical device, featuring an anchor block, compliant signal and ground contacts, and a clip for strain relief and compression, allowing for removability and adjustable compliance to minimize impedance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional cable terminations use permanent mechanical connections (soldering, crimping), then mechanical strength is improved, but impedance mismatch and signal reflections occur
Solution Approach 1:
The patent employs compliant contacts that can flex and adapt to non-planar device surfaces, creating a dynamic connection that maintains both mechanical strength and electrical integrity. The compliant nature allows the contact to conform to surface variations without requiring permanent mechanical attachment, thereby avoiding impedance mismatches while preserving connection strength.
Solution Approach 2:
The invention changes the mechanical parameters of the contact interface by using compliant materials and structures that can deform elastically. This parameter change allows the contact to accommodate surface non-planarities and maintain optimal electrical contact without the need for rigid permanent connections, thus preventing signal reflections and impedance mismatches.
2Strength
If conventional cable terminations use through-holes in PCBs for mounting, then mechanical attachment is improved, but controlled-impedance environment design becomes difficult
Solution Approach 1:
The patent removes the through-hole requirement from the mounting process by using surface-mount compliant contacts that attach directly to the PCB surface. This extraction of the through-hole element eliminates the disruption to the controlled-impedance environment while maintaining secure mechanical attachment through alternative surface-mount mechanisms.
3Strength
If conventional cable terminations use long transitions, then mechanical connection is improved, but signal reflections increase and higher frequency signals are inhibited
Solution Approach 1:
The compliant contacts enable a shorter transition length by allowing direct attachment to the device surface without requiring long mounting structures. The dynamic compliance compensates for surface variations, maintaining mechanical connection strength while minimizing the transition length and associated signal reflections.
4Reliability
If compliant contacts are used to mate directly with conductive pads, then signal integrity is improved, but mechanical strength may be reduced
Solution Approach 1:
The patent uses composite construction for the compliant contacts, combining materials with different properties to achieve both electrical compliance and mechanical strength. The composite structure allows the contact to be sufficiently compliant for signal integrity while maintaining adequate mechanical strength for reliable attachment.
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 solution reduces signal reflections and improves bandwidth by providing a compliant interface that adjusts to non-planarities on the device surface, maintaining optimal impedance control and signal integrity across higher frequency ranges.
Implementation Method 1
compliant contacts that can mate directly with conductive pads on an electrical device... providing a compliant interface that adjusts to non-planarities on the device surface
Implementation Method 2
a clip for strain relief and compression, allowing for removability and adjustable compliance
Data Source
AI summary
A controlled-impedance cable assembly for removably attaching a controlled-impedance cable to a surface of a device. Signal contacts are attached to signal conductors of cables and ground members are coupled to shields of the cables. Ends of the signal conductors and of elongated appendages extending from the ground members are positioned to make a pressure contact to pads and ground lands on the surface. Pressure to make those contacts may come from deflection of the ends of the signal conductors and elongated ground appendages or from a spring. The signal contacts and elongated appendages may be positioned to provide an impedance matching an impedance with the cables.