3D Lattice Contact Pad for Epoxy Interconnect Reliability
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Solution Overview
Problem
Existing electrical interconnects using conductive epoxy face challenges in achieving a robust connection during thermal cycling due to the difficulty in balancing the amount of epoxy applied, leading to either separation or electrical shorts, especially as interconnect density increases.
Innovation Solution
A method involving etching a lattice pattern into a contact pad on a circuit substrate, partially filling this pattern with conductive epoxy, and curing it, which creates a three-dimensional suspended lattice bond between connection points, allowing for increased epoxy volume and reduced precision in application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If too little conductive epoxy is used, then the connection fails during thermal cycling due to separation, but using more epoxy risks causing electrical shorts to other conductive surfaces
Solution Approach 1:
The patent transitions from a traditional two-dimensional flat pad structure to a three-dimensional suspended lattice structure. The lattice pattern creates vertical walls and internal volume, allowing the conductive epoxy to be contained in a 3D configuration rather than spreading horizontally. This dimensional change enables increased epoxy volume without increasing the horizontal footprint, thus preventing shorts to adjacent conductors while maintaining sufficient epoxy for reliable thermal cycling performance.
Solution Approach 2:
The suspended lattice structure inherently creates a porous configuration with internal voids and walls. This porous architecture provides increased surface area for epoxy adhesion while containing the epoxy within the lattice structure. The porous walls prevent the epoxy from flowing outward to cause shorts, while the internal volume accommodates sufficient epoxy to maintain connection integrity during thermal cycling.
2Reliability
If the amount of conductive epoxy is increased to prevent separation, then connection reliability improves, but the epoxy squeezes out beyond intended surfaces causing electrical shorts
Solution Approach 1:
By creating a three-dimensional suspended lattice structure, the patent provides vertical containment walls that restrict epoxy flow. This allows manufacturers to use more epoxy to ensure complete filling of the lattice structure without worrying about excessive horizontal spreading. The 3D structure acts as a physical barrier that tolerates variations in epoxy application amount while maintaining precise control over the final connection geometry.
Solution Approach 2:
The suspended lattice design accommodates partial or excessive epoxy application by providing internal volume and absorption capacity. The lattice structure can absorb varying amounts of epoxy material during dispensing, ensuring that even if the exact amount is not precisely controlled, the epoxy will be contained within the lattice walls and form an adequate connection without causing shorts to adjacent conductors.
3Reliability
If traditional flat pads are used, then manufacturing is simple, but the surface area for epoxy contact is limited reducing connection robustness
Solution Approach 1:
The patent creates a three-dimensional suspended lattice structure that extends vertically from the substrate surface. This 3D configuration provides both horizontal and vertical surface areas for epoxy contact, dramatically increasing the total adhesion area compared to a flat two-dimensional pad. The lattice walls and internal surfaces offer multiple contact points for the conductive epoxy, enhancing connection robustness while maintaining a compact horizontal footprint.
Solution Approach 2:
The contact pad is segmented into a lattice pattern consisting of multiple interconnected walls and cells. This segmentation creates numerous individual surface areas for epoxy adhesion distributed throughout the lattice structure. The segmented design provides increased total surface area for bonding while maintaining structural integrity and electrical connectivity through the conductive epoxy that fills and bonds to the lattice segments.
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 configuration enhances the robustness and thermal reliability of electrical interconnects by providing a larger surface area for epoxy contact, preventing separation and shorts, and accommodating higher interconnect densities.
Implementation Method 1
conductive epoxy provides many advantages in bonding different layers of an electrical apparatus... creating electrical connections
Implementation Method 2
conductive epoxy provides many advantages in bonding different layers of an electrical apparatus
Implementation Method 3
Many epoxies retain some elasticity after curing, offering advantages for flexible circuit substrates
Data Source
AI summary
A method of forming an electrical interconnect includes etching a lattice pattern into a contact pad on a circuit substrate as a first connection point, at least partially filling the lattice pattern with a conductive epoxy, contacting the conductive epoxy with a second connection point, and curing the epoxy.