Ceramic Electrode Interface with Boundary Layer for Thermal Shock
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Solution Overview
Problem
Ceramic electronic devices with baked electrodes face reliability issues due to stress generated at the interface when subjected to thermal shock, leading to potential peeling off from the element body.
Innovation Solution
A ceramic electronic device with a perovskite compound-based ceramic layer, an external electrode containing a conductor and glass frit with specific compositions of B, Si, and Zn, and a boundary layer comprising an oxide with Ba, Zn, and Si, which enhances joint reliability through mutual diffusion and stress reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a baked electrode is formed by applying conductive paste containing glass frit to the surface of the element body, then the joint strength is improved compared to plating or resin electrodes, but stress is generated at the interface under thermal shock causing the electrode to peel off
Solution Approach 1:
A boundary layer comprising an oxide including Ba, Zn, and Si is introduced between the external electrode and the ceramic layer. This boundary layer acts as an intermediary that reduces thermal stress at the interface and prevents peeling, while still allowing the glass frit in the external electrode to bond effectively to the ceramic structure.
Solution Approach 2:
The invention changes the compositional parameters of the boundary layer by introducing specific oxides (Ba, Zn, Si) that have thermal and mechanical properties intermediate between the ceramic layer and the external electrode. This parameter adjustment creates a gradient that reduces thermal stress concentration at the interface.
2Strength
If the glass frit contains B, Si, Ba, and Zn to improve diffusion and joint strength, then the bonding is enhanced, but the thermal stress mismatch between electrode and ceramic layer remains
Solution Approach 1:
The boundary layer serves as a mediator that decouples the thermal stress issue from the bonding requirement. It allows the glass frit to maintain strong chemical bonding with the ceramic layer while the boundary layer itself absorbs and distributes thermal stress through its intermediate thermal expansion properties.
Solution Approach 2:
The external electrode is formulated as a composite material containing conductor powder and glass frit with specific composition (B, Si, Ba, Zn). This composite structure provides both electrical conductivity and bonding capability, while the boundary layer composite (oxide mixture) provides stress management.
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 solution significantly improves the joint reliability between the element body and external electrode, preventing peeling even under thermal shock, by facilitating mutual diffusion and reducing thermal stress through a boundary layer with a specific composition that matches the external electrode.
Implementation Method 1
the mutual diffusion phenomenon contributes to the improvement in joint reliability. In the present invention, Ba, Zn, and Si are common elements between the external electrode and the boundary layer. Thus, the above-mentioned common elements are considered to mutually be diffused between the external electrode and the boundary layer
Implementation Method 2
the boundary layer containing the predetermined elements as mentioned above is considered to exhibit a function of reducing the thermal stress generated between the element body and the external electrode
Data Source
AI summary
A ceramic electronic device includes an element body and an external electrode. The element body includes a ceramic layer and an internal electrode layer. The external electrode is formed on an end surface of the element body and electrically connected to a part of the internal electrode layer. The ceramic layer includes a perovskite compound represented by ABO3 as a main component. The external electrode includes a conductor and a glass frit diffused in the conductor. The glass frit includes B, Si, Ba, and Zn. A boundary layer is present at an end of the ceramic layer in contact with the external electrode on the end surface of the element body and comprises an oxide including Ba, Zn, and Si.