Multilayer Ceramic Capacitor Closed Void Layer Stress Relief
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Solution Overview
Problem
Multilayer ceramic capacitors (MLCCs) face issues with electrostrictive properties leading to mechanical stress-induced cracking and microphonic noise under high electric fields, particularly in AC applications, which limits capacitance per unit volume and causes component failure.
Innovation Solution
Incorporating a closed void layer between internal electrodes of opposite polarity within the MLCC, where the closed voids are circumnavigated by ceramic, to relieve mechanical stresses and reduce electric field coupling, thereby enhancing the capacitor's resistance to damage and minimizing microphonic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of active layers is increased to protect against degradation from electrostrictive stress, then reliability improves, but volumetric efficiency (capacitance per unit volume) deteriorates
Solution Approach 1:
The patent introduces a porous stress relief layer with controlled porosity (30-70%) between the active layers. This porous structure absorbs electrostrictive stress through the void spaces, preventing crack propagation while maintaining thin active layer thickness for high volumetric efficiency. The porous material acts as a cushion that deforms under stress without transmitting damaging forces to the active electrodes.
Solution Approach 2:
The patent creates a composite structure combining active dielectric layers with a stress relief layer having different mechanical properties. The stress relief layer is made from the same ceramic material but with modified density and porosity, creating a composite that combines the electrical functionality of the active layers with the mechanical stress-absorbing properties of the porous intermediate layer.
2Productivity
If high dielectric constant ceramics are used to achieve higher capacitance, then capacitance per unit volume improves, but electrostrictive stress and cracking risk worsen
Solution Approach 1:
The patent introduces a stress relief layer as an intermediary between the high-dielectric-constant active layers and the external environment. This intermediate layer mediates the electrostrictive stress generated by the polarized ceramic, absorbing and distributing the mechanical stress before it can cause cracking, thereby enabling the use of high-k materials without the usual reliability penalties.
3Adaptability or versatility
If AC electric fields are applied to enable alternating current operation, then versatility improves, but oscillatory movement and microphonic noise worsen
Solution Approach 1:
The patent incorporates the porous stress relief layer in advance, before AC operation begins. This pre-positioned cushioning layer is designed to absorb the oscillatory movements that occur during AC operation, preventing the ceramic body from generating microphonic noise. The layer acts as a mechanical damper that converts oscillatory kinetic energy into minimal heat through internal friction in the porous structure.
4Object-affected harmful factors
If open low density ceramic layers are used as stress relief layers, then stress mitigation improves, but manufacturing complexity and structural integrity worsen
Solution Approach 1:
The patent applies local quality by creating a stress relief layer with specific porosity characteristics (30-70%) that is localized between the active layers. This controlled porosity provides optimal stress relief while maintaining sufficient structural integrity for handling and assembly. The local modification of density and porosity in this specific region achieves stress mitigation without requiring complex manufacturing processes throughout the entire component.
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 closed void layer effectively mitigates stress propagation and reduces microphonic noise, allowing MLCCs to withstand higher electric fields without degradation, while maintaining or increasing capacitance per unit volume, thus addressing the limitations of existing technologies.
Implementation Method 1
the electrostrictive, or piezoelectric, properties of the ceramic. Ceramics with large electric dipoles such as ferroelectric and anti-ferroelectrics, that are desirable for their high dielectric constants to achieve higher capacitance, have a high degree of electrostriction where these dipoles that can be arranged into domains align with the electric field.
Implementation Method 2
the electrostrictive, or piezoelectric, properties of the ceramic
Data Source
AI summary
An improved multilayer ceramic capacitor is described. The multilayered ceramic capacitor comprises first internal electrodes and second internal electrodes. The first internal electrodes and said second internal electrodes are parallel with dielectric there between. A first external termination is in electrical connection with the first internal electrodes and a second external termination is in electrical contact with the second internal electrodes. A closed void layer, comprising at least one closed void, is between electrodes.