Conductive Adhesive Layer Bimodal Particle Design
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Solution Overview
Problem
Isotropic conductive adhesive layers exhibit high contact resistance in the thickness direction, while anisotropic conductive adhesive layers have insufficient conductive particles for electromagnetic wave shielding, leading to poor connection stability, especially when subjected to high temperatures during the reflow step.
Innovation Solution
A conductive adhesive layer comprising a binder component and conductive particles, where conductive particles A have a median diameter of 100% or more of the adhesive layer thickness and conductive particles B have a median diameter of 1 to 50% of conductive particles A, with a mass ratio of 0.1 to 7.2, providing excellent connection stability even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an isotropic conductive adhesive layer is used, then the adhesive layer provides uniform conductivity in all directions, but the contact resistance in the thickness direction is high and the resistance value increases
Solution Approach 1:
The patent employs conductive particles with different size distributions where larger particles (first conductive particles) provide primary conduction paths with lower contact resistance, while smaller particles (second conductive particles) fill interstitial spaces to enhance overall conductivity. This local quality differentiation resolves the contradiction by optimizing particle roles at different spatial scales.
Solution Approach 2:
The adhesive layer combines binder resin with a composite particle system consisting of two distinct conductive particle types with different median diameters. This composite structure enables the material to achieve both low contact resistance through optimized particle packing and uniform conductivity through the synergistic interaction of different particle sizes.
2Quantity of substance
If an anisotropic conductive adhesive layer with smaller conductive particles is used, then the amount of conductive particles is reduced, but the conductivity between ground circuit and reinforcing member decreases and connection stability becomes poor
Solution Approach 1:
The patent optimizes the mass ratio parameter of first and second conductive particles within 0.1 to 7.2, and controls the median diameter ratio between 0.003 to 0.5. These parameter changes enable sufficient conductive particle content while maintaining excellent connection stability even after high-temperature reflow processing.
Solution Approach 2:
The smaller second conductive particles nest within the interstitial spaces between the larger first conductive particles, creating a hierarchical particle arrangement. This nesting structure maximizes the utilization of conductive particle material while ensuring reliable electrical connection through multiple conduction paths.
3Object-affected harmful factors
If the diameter of the opening on the electromagnetic wave shielding film is reduced, then the shielding effectiveness is improved, but the amount of conductive particles filled in the opening is reduced and connection stability decreases
Solution Approach 1:
The patent uses a bimodal particle size distribution where larger particles establish primary conduction bridges across small openings, while smaller particles fill gaps to ensure continuous conductive paths. This local quality optimization enables effective electromagnetic shielding through small openings while maintaining connection stability.
4Strength
If the conductive adhesive layer is subjected to high temperature in reflow step, then the adhesion is enhanced, but the conductivity decreases and connection stability deteriorates
Solution Approach 1:
The patent selects conductive particles with appropriate hardness and size distribution that can withstand high-temperature reflow processing without excessive deformation or aggregation. The binder resin is also selected to maintain its adhesive properties while allowing particle rearrangement that preserves conductive paths, cushioning against conductivity deterioration during thermal processing.
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 conductive adhesive layer maintains excellent connection stability between conductive members, ensuring effective conductivity and adhesion, even with small-diameter openings and under high-temperature conditions, enhancing the performance of printed circuit boards.
Implementation Method 1
the conductive particles include conductive particles A having a median diameter of 100% or more of a thickness of the conductive adhesive layer, and conductive particles B having a median diameter of 1 to 50% of the median diameter of the conductive particles A
Data Source
AI summary
An object of the present disclosure is to provide a conductive adhesive layer in which the connection stability between objects that are conductive members is excellent, and the connection stability is maintained even when the conductive adhesive layer is subjected to high temperature. The conductive adhesive layer is a conductive adhesive layer including a binder component and conductive particles, wherein the conductive particles include conductive particles A having a median diameter of 100% or more of a thickness of the conductive adhesive layer, and conductive particles B having a median diameter of 1 to 50% of the median diameter of the conductive particles A, a content of the conductive particles is 110 to 900 parts by mass based on 100 parts by mass of the binder component, and a mass ratio of the conductive particles A to the conductive particles B is 0.1 to 7.2.