Flexible Circuit Cable Attachment Using Gold Bump Columns
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for attaching flexible circuit cables to a substrate, such as direct soldering, Anisotropic Conductive Film (ACF), and conductive epoxy, face challenges with overlapping cables, including wetting issues, co-planarity problems, and limited radio frequency (RF) bandwidth, especially in small assembly scenarios like optical sub assemblies.
Innovation Solution
The method involves bonding multiple gold bumps on interconnection pads of the substrate to create columns that assist in solder or epoxy wetting and bonding, using a weight for alignment and pressure, and applying heat or UV light to cure the bonding material, while also employing nonconductive underfill epoxy for mechanical strength, which reduces bridging and enhances RF performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct soldering is used to attach flexible circuit cables, then electrical connectivity is achieved, but heat reflow impacts pre-attached chips or flexible circuit cables and solder wetting is blocked by gaps from pre-attached cables
Solution Approach 1:
The patent changes the temperature parameter by using conductive epoxy instead of solder, eliminating the need for high-temperature reflow processes. This allows attachment without thermally impacting pre-attached components while still achieving reliable electrical connectivity through the conductive properties of the epoxy material.
Solution Approach 2:
The patent introduces conductive epoxy as an intermediary bonding material between the flexible circuit cable and substrate. This intermediary material fills the gap created by pre-attached cables and provides both mechanical bonding and electrical connectivity without requiring high-temperature processing that would harm pre-attached components.
2Reliability
If ACF or ACP processes are used for flexible circuit cable attachment, then electrical connectivity is achieved through conductive particles, but high thermal temperature is required to cure the film which impacts pre-attached components
Solution Approach 1:
The patent changes the temperature parameter from high-temperature curing (required by ACF/ACP) to room temperature or low-temperature curing by using conductive epoxy. This eliminates thermal damage to pre-attached components while maintaining electrical connectivity through the conductive particles embedded in the epoxy matrix.
3Temperature
If conductive epoxy is used for flexible circuit cable attachment, then bonding is achieved without high temperature, but variance in planarity, epoxy volume control, and higher resistance limit RF bandwidth
Solution Approach 1:
The patent optimizes the resistance parameter by using conductive epoxy with improved conductive particle formulations that achieve lower resistance values. This enhancement allows the material to support wider RF bandwidth while maintaining the advantage of low-temperature attachment and addressing the limitation of traditional conductive epoxy materials.
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 approach enables reliable attachment of overlapping flexible circuit cables with improved RF performance, increased mechanical strength, and reduced electrical resistance, suitable for high-density signal routing in limited spaces without impacting pre-attached components.
Implementation Method 1
A first set of predetermined levels of heat is applied to promote the bonding material to bond between the substrate and the first flexible circuit cable
Implementation Method 2
If conductive epoxy was printed or dispensed on the flexible circuit cable, then heat, ultraviolet (UV) light, or both can be applied to cure the epoxy between the flexible circuit cable and substrate
Implementation Method 3
Heat and capillary effect will draw the underfill epoxy in between the flexible circuit cable and substrate
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 (405, 505, 605, 610, 1610, 1910, 1920) are bonded on interconnection pads (210, 410) of a substrate (200, 400, 500, 600, 1305, 1320, 1605, 1805, 1905, 2045, 2210, 2260) to create a columnar structure and solder or conductive epoxy is dispensed on the flexible circuit cable (220, 230, 1300, 1325, 1600, 1705, 1800, 1900, 1915, 2005, 2010, 2030, 2040, 2265). The substrate (200, 400, 500, 600, 1305, 1320, 1605, 1805, 1905, 2045, 2210, 2260) and flexible circuit cable (220, 230, 1300, 1325, 1600, 1705, 1800, 1900, 1915, 2005, 2010, 2030, 2040, 2265) are aligned and pressed together using force or placement of a weight (2050, 2205, 2255, 2300) on either the substrate (200, 400, 500, 600, 1305, 1320, 1605, 1805, 1905, 2045, 2210, 2260) or flexible circuit cable (220, 230, 1300, 1325, 1600, 1705, 1800, 1900, 1915, 2005, 2010, 2030, 2040, 2265). Appropriate heat is applied to reflow the solder or cure the epoxy. The solder wets to the interconnection pads (210, 410) of the substrate (200, 400, 500, 600, 1305, 1320, 1605, 1805, 1905, 2045, 2210, 2260), assisted by the gold bumps (405, 505, 605, 610, 1610, 1910, 1920), and have reduced bridging risk due to the columnar structure. A nonconductive underfill epoxy is applied to increase mechanical strength.