MLCC External Electrode Design for Thermal Shock Resistance
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Solution Overview
Problem
Ceramic multi-layer chip capacitors (MLCCs) face reliability issues due to thermal shock and flexural stress, leading to cracks at the interface between external electrodes and ceramic layers, which can result in short circuits and decreased electrostatic capacitance, especially when mounted on circuit boards that undergo warpage or strong external forces.
Innovation Solution
A ceramic electronic component design featuring a ceramic sintered body with internal conductive layers and external electrodes, where the first electrode layer extends from the side surfaces to the top and bottom surfaces, covered by a conductive resin layer, and a second electrode layer with an extended length, reducing stress concentration and crack propagation by increasing the area of the conductive resin layer and distance to internal electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the external electrodes are made with standard length and structure, then the manufacturing process is simple, but cracks occur at the interface between external electrodes and ceramic layers under thermal shock and flexural stress
Solution Approach 1:
The external electrode is divided into multiple layers: a first external electrode layer directly on the ceramic layer, a conductive resin layer in the middle, and a second external electrode layer on top. This segmentation allows each layer to perform specific functions - the first layer provides electrical connection, the conductive resin layer absorbs thermal expansion stress, and the second layer provides soldering interface, thereby preventing cracks while maintaining manufacturing feasibility
Solution Approach 2:
A conductive resin layer is introduced as an intermediary between the first external electrode layer and the second external electrode layer. This conductive resin layer has different thermal expansion properties compared to the ceramic and metal layers, acting as a buffer to absorb thermal stress and prevent crack propagation at the interface, thus improving thermal shock resistance
2Reliability
If the external electrodes are made with longer length, then stress concentration is reduced, but the manufacturing precision and alignment become more difficult
Solution Approach 1:
The external electrode structure is segmented into multiple layers with different lengths and functions. The first external electrode layer has a specific length optimized for stress distribution, while the second external electrode layer extends further to provide soldering interface. This segmentation allows each layer to be optimized independently for its specific function, maintaining manufacturing precision while improving flexural strength
Solution Approach 2:
Different regions of the external electrode structure are given different properties and lengths. The first external electrode layer is positioned at the interface with the ceramic layer where stress concentration occurs, while the second external electrode layer extends to the end surface to provide mechanical support and soldering interface. This local differentiation of electrode properties optimizes both stress distribution and manufacturing alignment
3Reliability
If the distance from ceramic surface to internal electrodes is increased, then crack propagation to internal electrodes is prevented, but the capacitance value decreases
Solution Approach 1:
The external electrode system is segmented into multiple layers that work together to prevent crack propagation. The conductive resin layer acts as a stress-absorbing barrier that stops cracks from reaching the internal electrodes, while the multi-layer structure maintains adequate capacitance by preserving the necessary electrode area and spacing
Solution Approach 2:
The conductive resin layer serves as an intermediary barrier between external stress sources and the internal electrodes. This layer absorbs and dissipates mechanical stress and thermal expansion forces, preventing crack propagation to the internal electrodes while allowing the capacitor to maintain its electrical performance through proper layer design
Data Source
AI summary
There is provided a ceramic electronic component including a ceramic sintered body, internal conductive layers, and external electrodes. Each of the external electrodes includes a first electrode layer, a conductive resin layer covering the first electrode layer, and a second electrode layer covering the conductive resin layer and having an extension length greater than the length of the first electrode layer extending from one of the side surfaces of the ceramic sintered body to the portions of the top and bottom surfaces thereof. The distance from the top or bottom surface of the ceramic sintered body to the closest layer of the internal conductive layers is greater than or equal to the length of the first electrode layer extending from one of the side surfaces of the ceramic sintered body to the portions of the top and bottom surfaces thereof.