Multilayer Ceramic Capacitor Layout to Suppress Corner Cracks
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Solution Overview
Problem
Multilayer ceramic capacitors with tall structures face issues of crack generation in the ceramic body due to the diffusion of Cu from external electrodes into internal electrodes, leading to internal stress concentration at corner portions.
Innovation Solution
The multilayer ceramic capacitor design includes a ceramic body with internal electrodes stacked in the width direction, reducing the number of stacked electrodes and minimizing the expansion of internal electrodes, thereby reducing stress on corner portions. Additionally, internal electrodes are positioned away from corner portions to avoid stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the firing temperature of external electrodes is lowered to inhibit Cu diffusion into internal electrodes, then crack generation is reduced, but sintering quality and connection strength deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the external electrode by adding specific elements (Al, Si, B, P, or S) that form low-melting-point compounds with Cu. This allows the external electrode to be fired at lower temperatures (reducing Cu diffusion and crack risk) while still achieving adequate sintering and connection strength through the formation of eutectic phases that enhance bonding at reduced temperatures.
2Quantity of substance
If internal electrodes are stacked in the height direction to increase capacitance, then electrostatic capacitance increases, but stress concentration and crack generation increase
Solution Approach 1:
The patent applies local quality by adding specific elements (Al, Si, B, P, or S) to the external electrode material composition. This creates a localized chemical modification at the interface between external and internal electrodes, where the added elements form protective low-melting-point compounds that specifically address the stress concentration problem at corner portions without changing the overall stacking configuration or capacitance design.
Solution Approach 2:
The external electrode is designed as a composite material containing Cu along with additional elements (Al, Si, B, P, or S). This composite structure creates a multi-phase system where the added elements form eutectic compounds with Cu, resulting in a material that combines good conductivity with reduced diffusion tendency and improved stress distribution at the electrode-ceramic interface.
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 inhibits the generation of cracks in the ceramic body by reducing the expansion of internal electrodes and minimizing stress concentration at corner portions, while maintaining electrostatic capacitance.
Implementation Method 1
Cu contained in the external electrodes diffuses into the internal electrodes while reacting with Ni
Implementation Method 2
Cu contained in the external electrodes diffuses into the internal electrodes while reacting with Ni
Implementation Method 3
when the firing temperature of the external electrodes to the ceramic body is lowered
Implementation Method 4
by lowering the firing temperature, the reaction rate between Cu and Ni is reduced
Data Source
AI summary
A multilayer ceramic capacitor has a dimension in a first direction equal to or greater than 1.5 times a dimension in a second direction orthogonal to the first direction, and includes a ceramic body, which has main surfaces perpendicular to the first direction, an end surface perpendicular to a third direction orthogonal to the first and second directions, and internal electrodes mainly composed of Ni, stacked in the second direction, and led out to respective connection ends on the end surface, and an external electrode, which is mainly composed of Cu and covers the end surface. The internal electrodes include outer-side internal electrodes located in both outer sides and inner-side internal electrodes located an inner side in the second direction. Distances from the main surfaces are larger at the connection ends of the outer-side internal electrodes than in central portions in the third direction of the inner-side internal electrodes.