Multilayer Capacitor BT-YSZ Covers Bending Strength
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Solution Overview
Problem
Multilayer capacitors used in vehicles face challenges with weak bending strength, leading to potential bending cracks and disconnection of internal electrodes, which can cause product defects and reduce capacity.
Innovation Solution
The use of a multilayer capacitor design featuring upper and lower covers made of a BT-YSZ composite material, with YSZ nanoparticles mixed into a barium titanate (BT) matrix, applied only to the covers to enhance mechanical strength, while maintaining a different composition for the active region to improve bending strength without affecting capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the multilayer capacitor uses conventional materials for covers, then the manufacturing cost is low and the structure is simple, but the bending strength is weak leading to bending cracks
Solution Approach 1:
The patent applies composite materials by forming a BT-YSZ composite in the cover regions through co-sintering of barium titanate and yttria-stabilized zirconia powders. The YSZ component (5-50 wt%) provides exceptional bending strength and crack resistance, while the BT matrix maintains dielectric properties. This composite structure resolves the contradiction by significantly improving bending strength without requiring fundamental structural changes to the capacitor design.
Solution Approach 2:
The patent implements local quality by applying the BT-YSZ composite material specifically to the cover regions (upper and lower covers) while keeping the active region with internal electrodes made of different composition. The cover regions contain 10-30 volume percent YSZ particles distributed in the BT matrix, creating localized high-strength zones that prevent bending cracks at the most vulnerable locations without affecting the electrical performance of the active region.
2Strength
If the multilayer capacitor uses BT-YSZ composite material in covers, then the bending strength is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges the formation of the BT-YSZ composite cover and the active region into a single co-sintering process. Both the BT-YSZ cover regions and the BT active region are formed from mixed green bodies that are sintered simultaneously at the same temperature (1200-1400°C). This integrated manufacturing approach resolves the contradiction by avoiding separate manufacturing steps while achieving the desired composite structure and high bending strength.
Solution Approach 2:
The patent utilizes parameter changes by controlling the sintering temperature range (1200-1400°C) to achieve complete densification and phase formation of both BT and YSZ components. The specific sintering conditions enable the BT-YSZ composite to develop optimal microstructure with YSZ particles distributed in the BT matrix, achieving maximum bending strength while maintaining manufacturing feasibility through a single sintering cycle.
3Strength
If the cover thickness is increased to improve bending strength, then the mechanical reliability is improved, but the overall size of the capacitor increases
Solution Approach 1:
The patent employs composite materials with YSZ (5-50 wt%) that has inherently high bending strength (1000-2000 MPa) to achieve enhanced mechanical reliability with minimal thickness increase. The YSZ particles (5-25 times smaller than BT particles) create a reinforced composite structure that provides superior crack resistance, allowing thin covers (10-40% of total capacitor thickness) to achieve high bending strength without increasing overall capacitor dimensions.
Solution Approach 2:
The patent applies local quality by concentrating the high-strength BT-YSZ composite material specifically in the cover regions where bending stresses are highest, while keeping the active region with different composition. This localized reinforcement provides maximum bending strength improvement at the critical locations without adding unnecessary material or increasing the overall capacitor size, as the enhanced strength is precisely where needed to prevent bending cracks.
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 BT-YSZ composite material significantly increases the bending strength of the multilayer capacitor, reducing the likelihood of cracks and maintaining high electrical reliability, as demonstrated by improved survival rates under increased pressing depths.
Implementation Method 1
the upper and lower covers include barium titanate (BT, BaTiO3) and Yttria-stabilized zirconia (YSZ)
Data Source
AI summary
A multilayer capacitor includes a body having a plurality of dielectric layers and first and second internal electrodes alternately disposed with the dielectric layers interposed therebetween, and further including an active region in which the first and second internal electrodes overlap each other, and upper and lower covers disposed above and below the active region, respectively; and first and second external electrodes disposed on the body to be connected to the first and second internal electrodes, respectively, wherein the upper and lower covers include barium titanate (BT, BaTiO3) and Yttria-stabilized zirconia (YSZ).