Anisotropic Conductive Film Lattice Pattern for Narrow Pitch Reliability
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Solution Overview
Problem
Existing anisotropic conductive films face issues with 'non-presence' and 'arrangement shift' of conductive particles, leading to shorts and conduction failures, particularly at narrow pitches and during miniaturization of electronic devices.
Innovation Solution
The anisotropic conductive film is designed with a planar lattice pattern where a proportion of lattice points without conductive particles is 25% or less, and some particles are shifted in the longitudinal direction by less than 50% of their average diameter, using a manufacturing method involving a transfer body with columnar convex portions and a weak adhesive layer to ensure precise placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If electrically conductive particles are densely packed in a single layer on the stretchable film surface, then the pitch can be reduced for miniaturization, but the particles aggregate causing short circuits
Solution Approach 1:
The patent applies preliminary action by pre-forming a planar lattice pattern on the stretchable film surface before transferring conductive particles. This predetermined pattern ensures particles are positioned at correct intervals, preventing aggregation while enabling narrow pitches. The lattice pattern serves as a guide that pre-establishes proper particle spacing before the actual particle placement occurs.
Solution Approach 2:
The patent uses an intermediary approach by introducing a transfer body with a lattice pattern as a mediating element between the particle source and the final application surface. This transfer body carries the lattice pattern that guides particle placement, acting as an intermediary tool that ensures precise particle positioning without direct manual placement, thereby preventing aggregation while achieving narrow pitches.
2Reliability
If electrically conductive particles are regularly arranged to prevent shorts, then reliability improves, but manufacturing complexity increases due to precise positioning requirements
Solution Approach 1:
The patent applies copying by creating a master lattice pattern on the transfer body that can be repeatedly used to transfer conductive particles in regular arrangements. This master pattern serves as a template that is copied onto multiple substrates, ensuring consistent particle positioning without requiring complex real-time control systems. The lattice pattern is replicated across the entire surface, simplifying the manufacturing process while maintaining high reliability.
Solution Approach 2:
The patent uses segmentation by dividing the continuous surface into discrete lattice points where conductive particles are placed. This segmentation approach transforms the complex problem of continuous particle positioning into a simpler task of placing particles at specific discrete locations defined by the lattice pattern. The lattice structure segments the surface into manageable units, reducing manufacturing complexity while ensuring regular particle arrangement for reliable conduction.
3Manufacturing precision
If concave portions are used to hold particles, then particle placement is improved, but non-presence occurs when particles are removed by squeegee
Solution Approach 1:
The patent applies inversion by reversing the conventional approach: instead of using concave portions to hold particles and risking their removal, the invention uses convex lattice patterns that protrude from the surface. The conductive particles are placed on these convex portions, which actively push particles into the adhesive layer during lamination. This inverted approach eliminates the non-presence problem because the convex structures ensure particle retention and proper transfer, maintaining conduction continuity.
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 design achieves good initial conduction resistance and reliability after aging, while suppressing shorts and conduction failures, enabling reliable anisotropic conductive connections between IC chips and wiring boards with narrow pitches.
Implementation Method 1
a weak adhesive layer is formed on a top surface of the convex portions
Implementation Method 2
electrically conductive particles are disposed at lattice points with a planar lattice pattern... good initial conduction resistance and good conduction reliability
Data Source
AI summary
An anisotropic conductive film with a structure wherein an electrically insulating adhesive base layer and cover layer are stacked, and electrically conductive particles are disposed at lattice points with a planar lattice pattern in the vicinity of the interface of the layers. In the anisotropic conductive film, a proportion of lattice points at which no electrically conductive particles are disposed with respect to all lattice points with the planar lattice pattern assumed in any reference region is 25% or less, and some of the electrically conductive particles disposed at lattice points with planar lattice pattern are disposed to be shifted in longitudinal direction of anisotropic conductive film with respect to corresponding lattice points, and a shift amount defined as a distance between a plane projection center of the electrically conductive particles disposed to be shifted and the corresponding lattice point is less than 50% the electrically conductive particles' average diameter.