Multilayer Capacitor Margin Composition for Electrostriction Crack Suppression
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Solution Overview
Problem
Multilayer capacitors face challenges with electrostriction cracks and thermal expansion defects at high voltages and temperatures, which existing solutions struggle to address effectively, particularly in terms of material property adjustments below threshold voltages.
Innovation Solution
A multilayer capacitor design incorporating a capacitor body with a twin boundary structure in the margin portions, featuring a molar ratio of Ba to Ti less than 1, and larger grain sizes compared to the active region, enhances mechanical strength by creating an elastically deformed and plastic deformed region with slip systems and high stacking fault energy, preventing electrostriction and thermal expansion cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If voltage per unit thickness is increased to meet market demand for high reliability, then power density improves, but electrostriction cracks occur at high voltages
Solution Approach 1:
The patent applies different material compositions to different regions of the capacitor body. The margin portion (non-active region) has a Ba/Ti molar ratio less than 1, creating a material with different properties than the active region. This local differentiation allows the margin portion to provide mechanical strength and crack resistance, while the active region maintains optimal electrical performance for high power density operation.
Solution Approach 2:
The capacitor body is constructed as a composite structure with at least two different material compositions. The margin portion uses a composite material with Ba/Ti ratio less than 1, which provides enhanced mechanical strength and resistance to electrostriction cracks and thermal expansion defects, while allowing the active region to use traditional high-k dielectric materials for maximum capacitance and power density.
2Temperature
If use temperature is increased to meet actual use case requirements, then operational reliability improves, but thermal expansion defects occur
Solution Approach 1:
The margin portion is designed with specific material properties (Ba/Ti ratio less than 1) that provide resistance to thermal expansion defects. This localized material optimization allows the capacitor to operate at high temperatures without compromising structural integrity, as the margin portion absorbs and mitigates thermal stress while the active region maintains electrical functionality.
3Reliability
If material properties are adjusted to suppress cracks, then reliability improves, but adjustment becomes difficult below threshold voltage
Solution Approach 1:
The patent changes the material composition parameter (Ba/Ti molar ratio) in the margin portion to less than 1, which fundamentally alters the material properties to provide crack suppression. This parameter change is applied during the manufacturing process by controlling the sintering conditions and material mixing ratios, making the crack suppression feature inherent to the manufacturing process rather than requiring post-processing adjustments.
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 enhanced microstructure increases the mechanical strength of the capacitor body, effectively suppressing crack defects and improving high-temperature reliability and moisture resistance, thereby addressing the limitations of existing multilayer capacitors.
Implementation Method 1
the margin portion excluding the active region in the capacitor body may include barium (Ba) and titanium (Ti) in amounts having a molar ratio of Ba to Ti of less than 1
Implementation Method 2
creating an elastically deformed and plastic deformed region with slip systems and high stacking fault energy
Implementation Method 3
A grain size of the margin portion may be larger than a grain size of the active region
Implementation Method 4
At high voltages, electrostriction cracks accompanied by an electrostriction phenomenon occur
Implementation Method 5
at high temperatures, defects accompanied by thermal expansion due to material expansion occur
Data Source
AI summary
A multilayer capacitor includes a capacitor body including first to sixth surfaces and including a plurality of dielectric layers and first and second internal electrodes alternately disposed with the dielectric layers interposed therebetween, and first and second external electrodes disposed on the third and fourth surfaces of the capacitor body and connected to the first and second internal electrodes, respectively, wherein the capacitor body includes an active region in which the first and second internal electrodes overlap in a first direction, and at least a portion of a margin portion excluding the active region in the capacitor body has a ratio of Ba to Ti less than 1 (Ba/Ti<1) and has a twin boundary structure.