Multilayer Ceramic Capacitor Electrode Layout for Crack Suppression
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Solution Overview
Problem
Multilayer ceramic capacitors face challenges in suppressing both electrostriction cracking and thermal cracking, which occur due to the piezoelectric effect and thermal expansion mismatch during voltage application and soldering processes.
Innovation Solution
The multilayer ceramic electronic component is designed with an internal electrode group comprising three types of internal electrodes with different thermal expansion coefficients. The first and second internal electrodes have lower thermal expansion coefficients, while the third internal electrodes have a higher thermal expansion coefficient, creating a stress distribution that suppresses cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If internal electrodes with uniform thermal expansion coefficients are used, then the manufacturing process is simple, but thermal cracking occurs during soldering due to thermal expansion mismatch
Solution Approach 1:
The patent applies local quality by differentiating the thermal expansion coefficients of internal electrodes based on their position within the laminate. First and second internal electrodes (at opposite ends) have a first thermal expansion coefficient, while third internal electrodes (intermediate positions) have a second thermal expansion coefficient that differs from the first. This localized variation in material property allows each region to accommodate thermal stress appropriately, preventing thermal cracking during soldering while maintaining manufacturing feasibility.
2Reliability
If internal electrodes with high thermal expansion coefficients are used, then thermal expansion during soldering is reduced, but electrostriction cracking occurs during voltage application due to piezoelectric effect
Solution Approach 1:
The patent applies parameter changes by carefully selecting and varying the thermal expansion coefficients of different internal electrode groups. The first thermal expansion coefficient (for first and second internal electrodes) and second thermal expansion coefficient (for third internal electrodes) are chosen within specific ranges to balance two competing requirements: reducing thermal expansion mismatch during soldering and minimizing stress concentration during voltage application. This parameter optimization prevents both thermal cracking and electrostriction cracking.
3Strength
If margins with high strength are used to prevent cracking, then structural integrity is improved, but stress concentration occurs at the interface between capacitance formation portion and margin
Solution Approach 1:
The patent applies beforehand cushioning by designing the internal electrode structure to preemptively compensate for stress concentration at the interface between the capacitance formation portion and margins. The differentiated thermal expansion coefficients of internal electrodes create a stress distribution that cushions the interface region, preventing crack initiation even when margins have high strength. This prior cushioning through structural design eliminates the harmful effect of stress concentration before it can cause 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
This configuration effectively suppresses both electrostriction cracking and thermal cracking by managing internal stress and thermal expansion, enhancing the reliability and durability of the multilayer ceramic capacitors.
Implementation Method 1
A first thermal expansion coefficient of the one or more first internal electrodes and a second thermal expansion coefficient of the one or more second internal electrodes are less than a third thermal expansion coefficient of the one or more third internal electrodes
Data Source
AI summary
A multilayer ceramic electronic component includes a laminate including an internal electrode group including internal electrodes laminated along a first axis, and ceramic layers, each of which is between adjacent internal electrodes; and a pair of external electrodes connected to the internal electrodes. The internal electrode group includes a first internal electrode group including one or more first internal electrodes at an end in a first direction of the first axis; a second internal electrode group including one or more second internal electrodes at an end in a second direction opposite to the first direction; and a third internal electrode group including one or more third internal electrodes between the first and second internal electrode groups. A first thermal expansion coefficient of the first internal electrode and a second thermal expansion coefficient of the second internal electrode are less than a third thermal expansion coefficient of the third internal electrode.