Multilayer Ceramic Capacitor Electrode Design for Crack Resistance
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Solution Overview
Problem
Multilayer ceramic capacitors face reduced mechanical strength and cracking issues due to size reduction and residual stress from conductive paste contraction, especially when mounted on smaller electronic devices.
Innovation Solution
A multilayer ceramic capacitor design with specific dimensions and electrode configurations, including Cu plated layers and glass-based base layers, is implemented to enhance mechanical strength and reduce stress, featuring a ceramic body with internal and external electrodes arranged to disperse mounting loads and improve adhesion to substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multilayer ceramic capacitors are reduced in height to achieve dense arrangement on wiring boards, then productivity and space utilization are improved, but mechanical strength decreases and cracking likelihood increases
Solution Approach 1:
The patent changes the material composition parameters of the external electrodes, specifically formulating a conductive paste containing glass particles (10-30 μm diameter) mixed with metal powder in specific ratios. This material parameter change allows the external electrodes to provide mechanical reinforcement to the ceramic body while maintaining the reduced height dimension, thus resolving the contradiction between compact size and mechanical strength
Solution Approach 2:
The patent uses composite materials in the external electrodes by combining metal powder (such as Cu, Ag, or their alloys) with glass particles in a specific ratio (metal powder 60-80 wt%, glass particles 20-40 wt%). This composite structure provides both electrical conductivity and mechanical reinforcement, enabling the capacitor to maintain high mechanical strength despite reduced height, thereby resolving the contradiction between compactness and strength
2Reliability
If external electrodes are increased in volume to improve electrical connection, then electrical conductivity is improved, but residual stress increases and mechanical strength decreases
Solution Approach 1:
The patent optimizes the volume ratio and size distribution parameters of the conductive paste components. By controlling the glass particle diameter (10-30 μm) and the metal-to-glass ratio (60-80 wt% metal powder), the external electrodes achieve sufficient electrical conductivity without excessive volume, thereby reducing residual stress while maintaining reliable electrical connection
Solution Approach 2:
The patent applies different material properties to different regions of the external electrodes. The glass particles provide mechanical reinforcement and stress relief in the bulk, while the metal powder ensures electrical conductivity at the contact interfaces. This local differentiation of material functions allows the external electrodes to satisfy both electrical and mechanical requirements without compromising overall strength
3Reliability
If conductive paste is applied and baked to form external electrodes, then electrical connectivity is achieved, but contraction force creates residual stress that decreases mechanical strength
Solution Approach 1:
The patent uses a composite conductive paste formulation where glass particles serve as a refractory skeleton that maintains structural integrity during the baking and contraction processes. The metal powder fills the spaces between glass particles and provides conductivity. This composite structure absorbs and distributes the contraction forces, preventing excessive residual stress while ensuring electrical connectivity
Solution Approach 2:
The glass particles act as an intermediary material between the ceramic body and the metal powder in the external electrodes. During baking, the glass particles form a stable matrix that mediates the thermal and mechanical stresses, reducing the direct contraction force on the ceramic body while still allowing the metal powder to establish electrical connections
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 design effectively prevents cracking and enhances the mechanical strength of the ceramic body, ensuring reliable operation and preventing short circuits, while maintaining excellent moisture resistance and adhesion to resin in printed wiring boards.
Implementation Method 1
the conductive paste is applied to ends of ceramic bodies, and baked, and in this case, the contraction force (tensile stress) of the conductive paste itself is also applied to the ceramic bodies
Implementation Method 2
The first external electrode includes a first base layer provided over the ceramic body and including a metal and glass; and a first Cu plated layer provided over the first base layer
Data Source
AI summary
A multilayer ceramic capacitor includes a ceramic body which is unlikely to be cracked. A dimension in a length direction L is referred to as L0. A distance in the length direction L is referred to as L1 between an end in the length direction L of a portion of a first external electrode located on a first principal surface and an end of a second internal electrode closer to the first end surface. The ratio L1/L0 is about 0.05 to about 0.35.