Flexible Circuit Cable Attachment Using Gold Bumps to Prevent Bridging
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Solution Overview
Problem
Existing methods for attaching flexible circuit cables to substrates face challenges in overlapping scenarios, including wetting issues due to gaps created by pre-attached cables, co-planarity issues, and high resistance, which affect signal integrity and reliability.
Innovation Solution
The use of gold bumps on interconnection pads to assist solder or conductive epoxy attachment, combined with underfill epoxy, to ensure proper bonding and mechanical strength, while minimizing bridging and smearing risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a rigid support member is used to maintain the shape of a flexible circuit cable, then the structural stability is improved, but the flexibility and bendability of the cable deteriorates
Solution Approach 1:
The support member is divided into multiple discrete clips distributed along the flexible circuit cable rather than using a single continuous rigid support. Each clip provides localized support while allowing the cable to bend between clips, resolving the contradiction between structural stability and flexibility.
Solution Approach 2:
The support member is designed with varying clip configurations - some areas have clips for rigid support while other areas have gaps or different clip densities to allow bending. This local variation in support quality enables the cable to be rigid where needed and flexible where needed.
2Reliability
If a complex attachment mechanism is used to secure the flexible circuit cable to the support member, then the connection reliability is improved, but the ease of assembly deteriorates
Solution Approach 1:
The clips are designed to automatically grip and retain the flexible circuit cable through elastic deformation and friction forces, eliminating the need for additional fastening operations. The cable insertion itself activates the retention mechanism, making assembly simple while ensuring reliable connection.
Solution Approach 2:
Traditional mechanical fastening systems (screws, clips, adhesives) are replaced with a simple elastic clip design that uses spring force and friction to secure the cable. This substitution simplifies the attachment mechanism while maintaining connection 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 method enhances signal integrity, reduces electrical resistance, and improves RF performance by ensuring reliable attachment of multiple flexible circuit cables with minimal impact on pre-attached components.
Implementation Method 1
Appropriate heat is applied to reflow the solder or cure the epoxy
Implementation Method 2
Heat, ultraviolet (UV) light, or both can be applied to cure the epoxy
Implementation Method 3
Heat and capillary effect will draw the underfill epoxy in between the flexible circuit cable and substrate
Implementation Method 4
The gold bumps create a standoff height, assisting in the underfill path, solder wicking, and reducing risk of bridging
Data Source
Figure 1~2C
Figure 3
Figure 4~6
AI summary
A method and apparatus for multiple flexible circuit cable attachment is described herein. Gold bumps are bonded on interconnection pads of a substrate to create a columnar structure and solder or conductive epoxy is dispensed on the flexible cable circuit. The substrate and flexible cable circuit are aligned and pressed together using force or placement of a weight on either the substrate or flexible cable circuit. Appropriate heat is applied to reflow the solder or cure the epoxy. The solder wets to the substrate pads, assisted by the gold bumps, and have reduced bridging risk due to the columnar structure. A nonconductive underfill epoxy is applied to increase mechanical strength.