Binder Resin Composition for Printable, Adhesive MLCC Electrode Pastes
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Solution Overview
Problem
Existing mixed binder resins for electrically conductive pastes used in multilayer ceramic capacitors (MLCCs) exhibit increased elastic rheological characteristics and decreased homogeneity, leading to nonuniform internal electrodes, reduced capacity, and reliability issues due to printing defects.
Innovation Solution
A binder resin comprising a mixture of polyvinyl acetal and cellulose derivative, with a specific mixing ratio and inclusion of carbodiimide, carboxylic acid, and an optional accelerator, formulated to achieve a phase difference greater than 45° and viscosity ratio of 4.5 or less, enhancing printability and adhesiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a mixed binder resin (cellulose derivative + butyral-based resin or acrylic resin) is used to improve mechanical strength and adhesion, then adhesion to green sheet is improved, but rheological characteristics become excessively elastic and homogeneity decreases
Solution Approach 1:
The patent changes the chemical parameters of the binder resin by specifying polyvinyl acetal with 70-90% acetalization degree and controlling the mixing ratio with cellulose derivative at 20:80 to 80:20. This parameter optimization achieves the desired balance between adhesion strength and rheological homogeneity, eliminating excessive elasticity while maintaining improved mechanical properties.
Solution Approach 2:
The patent creates a composite binder resin system by combining polyvinyl acetal with cellulose derivative in specific ratios. This composite approach leverages the complementary properties of both materials: polyvinyl acetal provides adhesion and mechanical strength, while cellulose derivative contributes to printability and rheological stability, achieving a balanced performance that neither material could provide alone.
2Quantity of substance
If particle size of electrically conductive material is reduced to achieve miniaturization, then capacity increases, but dispersivity in binder resin deteriorates
Solution Approach 1:
The patent optimizes the chemical composition parameters of the binder resin by controlling the acetalization degree of polyvinyl acetal at 70-90% and the mixing ratio with cellulose derivative. These parameter adjustments enhance the binder's dispersing capability, allowing fine electrically conductive particles to remain uniformly distributed without aggregation, thus maintaining dispersivity even as particle size decreases for miniaturization.
3Shape
If mixed binder resin is used to compensate step-like sections, then leveling property improves, but printing uniformity and film homogeneity decrease
Solution Approach 1:
The patent optimizes the rheological parameters of the binder resin by controlling the mixing ratio of polyvinyl acetal and cellulose derivative, and specifying the acetalization degree. This parameter optimization adjusts the viscosity and elasticity balance, providing sufficient leveling property to compensate for step-like sections while maintaining printing uniformity and film homogeneity through controlled flow characteristics.
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 binder resin improves the uniformity and adhesion of internal electrodes, reducing defects and maintaining capacity, thereby enhancing the reliability and performance of MLCCs.
Implementation Method 1
A binder resin for an inorganic particle-dispersed paste includes a mixture in which a polyvinyl acetal and a cellulose derivative are mixed so as to satisfy 0.2 ≤ X/(X + Y) ≤ 0.8, where X and Y stand for parts by mass of the polyvinyl acetal and the cellulose derivative, respectively, and further carbodiimide is mixed
Data Source
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AI summary
A binder resin for an inorganic particle-dispersed paste that excels in both printability and adhesiveness and such an inorganic particle-dispersed paste are provided. The resin includes a mixture in which a polyvinyl acetal and a cellulose derivative are mixed so as to satisfy 0.2 ≤ X/(X + Y) ≤ 0.8, where X and Y stand for parts by mass of the polyvinyl acetal and the cellulose derivative, respectively. When a paste is formulated by mixing and kneading the resin with spherical nickel particles with an average particle diameter of 0.3 µm, barium titanate particles with an average particle diameter of 0.05 µm, a nonionic surfactant, dihydroterpineol, and mineral spirit at the prescribed mixing ratio, the paste is as follows: when strains of 0.02 and 0.2 are applied to the paste at an angular frequency of 6.284 rad/s, a value of a phase difference δ between each strain and a stress caused by each strain is greater than 45°; and a ratio of the viscosity at a shear rate of 4 (1/s) to the viscosity at a shear rate of 40 (1/s) is 4.5 or less.