Three-Terminal MLCC Electrode Interface for Crack-Resistant Mounting
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Solution Overview
Problem
Conventional multilayer ceramic capacitors are prone to performance degradation and reliability issues due to stress transmission and crack generation when the substrate undergoes thermal shock or deflection, as existing stress relief mechanisms are inadequate.
Innovation Solution
A three-terminal multilayer ceramic capacitor design featuring a multilayer body with specific internal and external electrode configurations, including organic layers with controlled Si to Cu atomic concentration ratios and surface roughness, which facilitates stress dispersion by easily peeling off plating layers, thereby reducing crack and deformation risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wraparound portions with proximal end-side joint portions are used to prevent ceramic body cracking, then some stress protection is provided, but stress is still transmitted through the joint portions causing insufficient crack prevention
Solution Approach 1:
The patent introduces a resin layer as an intermediary between the external electrode and the ceramic body. This resin layer has lower mechanical strength and elasticity compared to the ceramic and metal components, allowing it to absorb and dissipate stress before it reaches the ceramic body, thereby preventing crack propagation while maintaining electrical connectivity.
Solution Approach 2:
The patent changes the material parameters of the interface between the external electrode and ceramic body by introducing a resin layer with specific mechanical properties (lower strength, higher elasticity). This parameter change allows the interface to deform under stress without transmitting damaging forces to the ceramic body, resolving the contradiction between maintaining connection and preventing stress transmission.
2Reliability
If external electrodes are joined to principal planes to ensure electrical connection, then electrical connectivity is maintained, but stress from substrate deflection is transmitted to the multilayer body causing cracks
Solution Approach 1:
The resin layer serves as a mediator that maintains electrical connection between the external electrode and the internal electrode while simultaneously protecting the multilayer body from stress. The resin's elastic properties allow it to deform under stress without breaking the electrical circuit or transmitting damaging forces to the ceramic structure.
Solution Approach 2:
The patent creates a composite structure at the electrode interface by combining metal (external electrode), organic resin (intermediate layer), and ceramic (multilayer body). This composite material approach allows each component to contribute its advantageous properties: electrical conductivity from metal, stress absorption from resin, and structural integrity from ceramic.
Data Source
AI summary
In a three-terminal multilayer ceramic capacitor, each of first through fourth external electrodes includes a base electrode layer including a conductive metal and a glass component, an organic layer including an organosilicon compound covering the base electrode layer, and a plating layer on the organic layer. On a surface of the organic layer in a portion facing the plating layer, an atomic concentration ratio of Si to Cu is greater than or equal to about 1.5% and less than or equal to about 5.5%, or greater than or equal to about 0.8% and less than or equal to about 2.8%, and a surface roughness is greater than or equal to about 0.334 and less than or equal to about 0.371, or greater than or equal to about 0.352 and less than or equal to about 0.395.