Multilayer External Terminal for Ceramic Chip Components
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Solution Overview
Problem
The use of metal external terminals with high thermal expansion coefficients in electronic devices leads to stress at solder connections, reducing the strength and reliability of the connection between ceramic element bodies and external terminals, particularly affecting thermal shock resistance.
Innovation Solution
A multilayer structure of metals with specific thermal expansion coefficients is employed for the external terminals, where the first and third metals have higher expansion coefficients than the ceramic element body, and the second metal has a lower expansion coefficient, configured to reduce stress at the connection point and improve equivalent series resistance (ESR).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal such as copper and copper alloy is used as the external terminal to reduce electronic resistance, then the electric resistance is reduced, but a stress is generated at the solder part due to the larger thermal expansion coefficient compared to the ceramic element body
Solution Approach 1:
The patent changes the thermal expansion coefficient parameter of the external terminal by using a metal alloy composition where the thermal expansion coefficient is specifically designed to be smaller than that of the ceramic element body, thereby reducing stress at the solder connection while maintaining low electric resistance
Solution Approach 2:
The patent employs a composite metal alloy material for the external terminal that combines the properties of low electric resistance with a reduced thermal expansion coefficient, creating a material that simultaneously addresses both electrical performance and thermal-mechanical compatibility
2Reliability
If a metal with a larger thermal expansion coefficient than the ceramic element body is used as the external terminal, then the electric resistance is reduced, but the strength at the connection part between the terminal electrode and external terminal is decreased
Solution Approach 1:
The patent modifies the thermal expansion coefficient parameter of the external terminal material to be smaller than that of the ceramic element body, which prevents stress generation during thermal cycles and thereby maintains the strength of the solder connection while preserving low electric resistance
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
This configuration effectively reduces stress at the connection point, enhancing the strength and reliability of the connection, including thermal shock resistance, while maintaining low electric resistance and improving ESR.
Implementation Method 1
a thermal expansion coefficient of the external terminal is smaller than that of the ceramic element body
Data Source
AI summary
An electronic device includes a chip component with a terminal electrode formed on an end surface of a ceramic element body including an internal electrode and an external terminal electrically connected to the terminal electrode. The external terminal includes a terminal electrode connection part arranged to face the terminal electrode and a mounting connection part connectable to a mounting surface. The terminal electrode connection part includes a multilayer structure of a first metal connected to the terminal electrode, a second metal arranged outside the first metal, and a third metal arranged outside the second metal. A thermal expansion coefficient of the external terminal is smaller than that of the ceramic element body.