Multi-Layer Ceramic Capacitor Internal Electrode Grain Growth Control
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Solution Overview
Problem
Multi-layer ceramic capacitors face issues with internal electrode discontinuity due to grain growth and sintering shrinkage, leading to reduced electrostatic capacity, and existing solutions either separate ceramic powder from metal particles or use expensive noble metals.
Innovation Solution
Forming internal electrodes with Ni metal particles coated with metals or metal oxides like Mn, Co, Fe, Cu, Nb, Ba, Ca, Sr, Ti, Zn, V, or rare earth metals, and firing in a reducing atmosphere with controlled oxygen partial pressure to suppress grain growth and shrinkage, ensuring good continuity at a lower cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ni metal particles are used in conductive paste without coating, then the unit price is low, but grain growth during firing causes internal electrode discontinuity and reduced electrostatic capacity
Solution Approach 1:
The patent uses composite material structure by coating Ni metal particles with a layer having controlled sintering characteristics. This composite structure combines the low cost advantage of Ni with the grain growth control benefits of the coating layer, resolving the contradiction between cost and reliability.
Solution Approach 2:
The patent changes the physical and chemical parameters of the Ni particles by applying a coating layer with specific sintering temperature characteristics. This parameter modification controls grain growth during firing, maintaining internal electrode continuity while using inexpensive Ni base material.
2Manufacturing precision
If ceramic powder is added to conductive paste to match firing shrinkage temperatures, then sintering temperature alignment is improved, but ceramic powder separates from metal particles during grain growth reducing internal electrode continuity
Solution Approach 1:
The patent extracts the ceramic powder from the conductive paste formulation and replaces it with a coating layer applied directly to the metal particles. This eliminates the separation problem between ceramic powder and metal particles while maintaining the sintering temperature alignment function.
Solution Approach 2:
The coating layer acts as an intermediary between the metal particles and the surrounding environment, providing both sintering temperature control and preventing particle separation. This intermediary layer resolves the contradiction by performing multiple functions that previously required separate components.
3Reliability
If noble metal coating is applied to Ni metal particles to prevent grain growth, then internal electrode continuity is improved, but the unit price of metal particles increases significantly
Solution Approach 1:
The patent uses a cost-effective coating material that is not as expensive as noble metals but provides sufficient grain growth control for the application. This disposable-like coating layer achieves the reliability goal without the high cost of noble metals.
Solution Approach 2:
The patent modifies the sintering behavior parameters by using a coating layer with specifically designed thermal properties. This parameter change provides grain growth control comparable to noble metals but at lower cost, resolving the contradiction between reliability and manufacturing cost.
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 approach results in a multi-layer ceramic capacitor with improved internal electrode continuity and electrostatic capacity while maintaining a relatively low cost, as the grain growth and firing shrinkage are effectively managed, maintaining the continuity and capacity within satisfactory ranges.
Implementation Method 1
sintering of the Ni metal particles initiates first to initiate shrinkage. Subsequently, sintering of the dielectric ceramic layer initiates
Implementation Method 2
grain growth of the metal particles in the course of firing, the ceramic powder and the metal particles are separated
Implementation Method 3
sintering of the Ni metal particles initiates first to initiate shrinkage. Therefore, shrinkage proceeds further to result in a disconnected state
Data Source
AI summary
A multi-layer ceramic capacitor, which has an internal electrode of good continuity and may be obtained at a relatively low cost, is disclosed. The internal electrode layer comprises metal particles, wherein the arithmetic mean particle diameter of the metal particles, which is determined based on the particle diameter in the direction parallel with the plane direction of the internal electrode layer, is made smaller than the thickness of the internal electrode layer. The multi-layer ceramic capacitor can be obtained by forming the internal electrode layer using a conductive paste containing a conductive power comprising Ni metal particles coated with particles of a base metal selected from Mn, Co, Fe, Cu, Nb, Ba, Ca, Sr, Ti, Zn, V, and rare earth metals, particles of an oxide thereof and applying a heat treatment in a reducing firing atmosphere having an oxygen partial pressure from about 10−14 to 10−18 atm.