Conductive Ink Composition for Stress-Resistant Printed Circuits
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Solution Overview
Problem
Conductive circuits formed using conductive ink compositions on semiconductor circuit boards face issues with stress resistance, shape stability, and high contact resistance due to the use of glass-based materials and large conductive particles, which are exacerbated by thermal stress and miniaturization demands.
Innovation Solution
A solvent-free, addition-curable conductive ink composition combining organopolysiloxane, organohydrogenpolysiloxane, conductive particles with a size of at least 5 µm, finer conductive micro-particles, a thixotropic agent, and a hydrosilylation catalyst, which maintains shape stability and reduces contact resistance through controlled thixotropy and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glass-based conductive ink composition is used, then conductivity is achieved, but stress resistance deteriorates under thermal stress
Solution Approach 1:
The patent changes the material composition parameters by replacing glass frit with silicone rubber as the binder, and by carefully controlling the particle size distribution of conductive particles (combining fine particles <5μm with larger particles ≥5μm). This parameter change transforms the material from glass-based to silicone-based, providing stress resistance while maintaining conductivity.
Solution Approach 2:
The patent creates a composite material system consisting of silicone rubber binder, conductive particles (metal or carbon), and controlled particle size distribution. This composite structure combines the flexibility and stress resistance of silicone rubber with the conductivity of metal particles, resolving the contradiction between conductivity and stress resistance.
2Shape
If only large conductive particles (≥5 μm) are used, then thixotropy is achieved for shape stability, but contact resistance increases
Solution Approach 1:
The patent segments the conductive particle population into two distinct size groups: fine particles (<5μm) for contact resistance reduction and larger particles (≥5μm) for thixotropy and shape stability. This segmentation allows each particle size to perform its specialized function without compromising the other.
Solution Approach 2:
The patent applies local quality by assigning different particle sizes to different functional requirements: fine particles are distributed throughout the composition to ensure low contact resistance at interfaces, while larger particles provide the thixotropic structure for shape stability. Each particle size serves its local function optimally.
3Ease of operation
If solvent-based conductive ink is used, then ease of printing is achieved, but shape control deteriorates due to solvent volatilization
Solution Approach 1:
The patent replaces the solvent (a temporary, volatile component) with a non-volatile silicone rubber binder system. The silicone rubber provides the necessary fluidity for printing during application, then maintains shape stability without requiring solvent evaporation, eliminating the shape control problems associated with solvent volatilization.
4Length of moving object
If conductive particles are densely packed for miniaturization, then circuit size is reduced, but contact resistance increases due to fewer contact paths
Solution Approach 1:
The patent changes the particle size parameter distribution by incorporating a significant portion of fine particles (<5μm). These fine particles can densely pack while maintaining numerous contact paths between particles, reducing contact resistance even in miniaturized circuits. The dual-size particle system allows dense packing without sacrificing conductivity.
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 ensures low ohmic resistance, high shape reproduction, and stress relaxation of conductive circuits, enabling high-speed printing and precise control of circuit shape, even under thermal stress, with improved contact resistance and stability.
Implementation Method 1
a liquid, addition curable, conductive circuit-forming ink composition comprising (A) an organopolysiloxane having at least two silicon-bonded alkenyl groups, (B) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms
Implementation Method 2
When only conductive particles having a particle size of at least 5 μm contributing to least thixotropy are used... when a thixotropic agent is added thereto. The printed circuit maintains its shape unchanged before and after curing.
Data Source
AI summary
A conductive circuit is formed by printing a pattern of an ink composition and curing the pattern. The ink composition is a substantially solvent-free, liquid, addition curable, ink composition comprising (A) an organopolysiloxane having at least two alkenyl groups, (B) an organohydrogenpolysiloxane having at least two SiH groups, (C) conductive particles having an average particle size ≥ 5 µm, (D) conductive micro-particles having an average particle size < 5 µm, (E) a thixotropic agent, and (F) a hydrosilylation catalyst.