Multilayer Capacitor Dielectric Gradient for Moisture and Crack Resistance
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Solution Overview
Problem
Existing multilayer electronic devices face challenges in achieving high moisture resistance and reducing electrostrictive cracks, particularly during high-voltage applications.
Innovation Solution
A multilayer electronic device is designed with an element body having inner dielectric layers and external electrodes, where the dielectric layers include a main component with a perovskite crystal structure and a subcomponent comprising 'RE', 'M', and Si, with specific concentration gradients of 'RA' and 'RB' to ensure gradual sintering behavior and reduced stress differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the exterior region is sufficiently fired to densify the structure, then porosity is reduced and moisture resistance is improved, but stress differences between exterior and interior regions increase causing electrostrictive cracks
Solution Approach 1:
The patent applies local quality by creating a composition gradient where the rare earth element content varies between the interior and exterior regions. Specifically, the exterior region has a higher content of certain rare earth elements (RA) compared to the interior region (RB), where RA and RB are different elements. This local compositional difference enables the exterior region to achieve sufficient densification and moisture resistance while the interior region maintains properties that reduce stress concentration, thereby preventing electrostrictive cracks.
Solution Approach 2:
The patent employs parameter changes by controlling the concentration of rare earth elements (RA and RB) in different regions of the multilayer electronic device. By adjusting the mole ratios and types of rare earth elements in the interior versus exterior regions, the sintering behavior and stress distribution are optimized. The exterior region is formulated with higher RA content to achieve low porosity and high moisture resistance, while the interior region uses different RB content to manage stress during high-voltage application, thus resolving the contradiction between moisture resistance and crack prevention.
2Ease of manufacture
If uniform composition is used throughout the device, then manufacturing is simplified, but stress distribution becomes uneven during sintering causing cracks
Solution Approach 1:
The patent implements local quality by deliberately creating a non-uniform composition where the exterior region contains a higher concentration of specific rare earth elements (RA) compared to the interior region (RB). This localized compositional variation is designed to create favorable stress distribution during sintering and high-voltage operation. The exterior region's higher RA content promotes densification and reduces porosity, while the interior region's different composition helps equalize stress, preventing crack formation despite the added manufacturing complexity.
3Reliability
If high rare earth element content is used to improve moisture resistance, then porosity decreases, but stress concentration increases leading to more cracks
Solution Approach 1:
The patent applies local quality by spatially distributing different rare earth elements (RA and RB) at different concentrations in the interior and exterior regions. The exterior region has higher RA content to achieve low porosity and high moisture resistance, while the interior region uses different RB content to reduce stress concentration. This localized differentiation allows each region to optimize its function: the exterior for moisture barrier performance and the interior for stress management, thereby preventing electrostrictive cracks while maintaining high moisture resistance.
Solution Approach 2:
The patent employs composite materials by combining different rare earth elements (RA and RB) in a gradient distribution throughout the multilayer structure. The exterior region comprises a composite with higher RA content optimized for moisture resistance, while the interior region contains a different composite formulation with RB elements optimized for stress distribution. This composite approach with regional variation enables simultaneous achievement of low porosity and reduced electrostrictive cracking.
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 device achieves enhanced moisture resistance and reduced electrostrictive cracks, ensuring reliability under high humidity and high-voltage conditions.
Implementation Method 1
the exterior region is sufficiently fired for the inner dielectric layers and the outer dielectric layer of the multilayer electronic device according to the present invention have the compositions, particularly 'RE' and its content, satisfying the conditions described above, porosity of the exterior region can be reduced for its densification
Implementation Method 2
the main component being included in a main phase grain of the inner dielectric layers and a main phase grain of the outer dielectric layer and having a perovskite crystal structure represented by a general formula ABO3
Data Source
AI summary
A multilayer electronic device includes an element body including an interior region and an exterior region and a pair of external electrodes. The interior region includes inner dielectric layers and internal electrode layers laminated alternately. The exterior region is disposed outwards from the interior region in a lamination direction. The pair of external electrodes is disposed on a surface of the element body and connected to the internal electrode layers. DRAa<DRAb<DRAc and DRBa>DRBb>DRBc are satisfied, where “RA” includes an element having a highest mole ratio among “RE” in the inner dielectric layers of a third region at a center of the interior region in the lamination direction, “RB” includes an element having a highest mole ratio among “RE” in a first region at a center of the exterior region in the lamination direction, and “RA” and “RB” are different from each other.