Porous Tin External Electrode for Ceramic Components
Solution Overview
Problem
Ceramic electronic components with tin-based external electrodes are prone to whisker generation due to compressive stress, leading to potential short circuits, as existing solutions fail to effectively prevent whisker formation under various stress conditions.
Innovation Solution
Incorporating a tin layer with dispersed pores as the outermost layer of the external electrode, which relaxes compressive stress and suppresses whisker growth, and using a copper layer adjacent to the tin layer to form an intermetallic compound while maintaining production efficiency through sputtering processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a tin layer is formed on the copper layer as the outermost layer of the external electrode, then mountability with tin-based lead-free solder is improved, but whiskers are generated due to compressive stress from intermetallic compound formation
Solution Approach 1:
A nickel layer is introduced as an intermediary between the tin layer and copper layer. This nickel layer prevents direct contact between tin and copper, thereby suppressing the formation of tin-copper intermetallic compounds that generate compressive stress. The nickel layer acts as a barrier that maintains the tin layer's integrity while preserving solderability.
Solution Approach 2:
The external electrode structure is divided into distinct layers with specific functions: the tin layer provides solderability, the nickel layer prevents intermetallic compound formation, and the copper layer provides electrical conductivity. Each layer has localized properties optimized for its specific function, resolving the contradiction between mountability and whisker prevention.
2Object-generated harmful factors
If a nickel layer is provided between the tin layer and copper layer to prevent intermetallic compound formation, then whisker generation is suppressed, but device complexity increases
Solution Approach 1:
The thickness of each layer (tin, nickel, copper) is optimized within specific ranges to achieve the desired balance between preventing whisker formation and maintaining structural simplicity. By controlling layer thickness parameters, the patent achieves effective whisker suppression without excessive structural complexity.
3Strength
If the tin layer is made dense to improve mechanical strength, then compressive stress resistance is improved, but whisker generation is suppressed less effectively compared to porous tin layers
Solution Approach 1:
The tin layer is designed with a controlled porous structure rather than being completely dense. The pores act as stress relief points that reduce compressive stress within the tin layer, thereby suppressing whisker formation. The porous structure maintains sufficient mechanical strength while effectively preventing stress accumulation that leads to whiskers.
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 tin layer with dispersed pores effectively prevents whisker generation, reducing the risk of short circuits and improving mountability and production efficiency of ceramic electronic components.
Implementation Method 1
The forming an external electrode includes forming a tin layer as an outermost layer of the external electrode by sputtering
Data Source
AI summary
A ceramic electronic component includes a ceramic body and an external electrode. The external electrode is formed along a surface of the ceramic body and includes a tin layer as an outermost layer. The tin layer includes dispersed pores.