Inductor Grain Size Gradient for Stress and Penetration Control
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Solution Overview
Problem
Inductors face issues with cracking and reliability due to increased sinterability, which affects frequency characteristics, and lowering sinterability leads to reduced reliability and strength due to plating solution penetration.
Innovation Solution
A protective layer with a larger grain size than the inductor body is applied, improving density and reducing plating solution penetration, while the body's smaller grain size reduces stress for better frequency characteristics, and adjusting the grain size of cover portions relieves stress for improved impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the sinterability of the body is increased, then the strength and reliability of the inductor body is improved, but frequency characteristics deteriorate due to stress
Solution Approach 1:
The patent applies different grain sizes to different regions of the inductor body. The protective layer has a larger grain size (1-10 μm) than the body (0.1-1 μm), creating local quality differences that simultaneously improve strength and frequency characteristics in their respective regions.
Solution Approach 2:
The inductor employs a composite structure consisting of the body and a protective layer with different ceramic material compositions and grain sizes. This composite approach allows optimization of each layer for its specific function while maintaining overall system performance.
2Reliability
If the sinterability of the body is lowered, then frequency characteristics are improved, but reliability deteriorates due to plating solution penetration and reduced body strength
Solution Approach 1:
The protective layer with larger grain size (1-10 μm) is specifically applied to regions where plating solutions contact the body, creating a dense barrier that prevents penetration while maintaining the body's fine grain structure for good frequency characteristics.
Solution Approach 2:
The protective layer acts as an intermediary barrier between the plating solution and the inductor body, preventing direct contact and penetration while allowing the body to maintain its optimal sinterability for frequency performance.
3Reliability
If the grain size in the protective layer is increased, then density is improved and plating solution penetration is prevented, but manufacturing complexity increases
Solution Approach 1:
The protective layer with larger grain size is formed on the body surface before the plating process, preliminarily establishing a barrier that prevents plating solution penetration and eliminates the need for additional protective measures during manufacturing.
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 enhances the reliability and frequency characteristics of inductors by preventing plating solution penetration and reducing stress, resulting in improved strength and impedance performance.
Implementation Method 1
A grain size in the protective layer is greater than a grain size in the body
Implementation Method 2
A grain size (Ga) in the active portion, a grain size (Gb) in the cover portion, and a grain size (Gc) in the protective layer satisfy Ga
Data Source
AI summary
An inductor includes a body having a coil portion disposed therein, and a protective layer disposed on a surface of the body. The body includes an active portion in which a coil portion is disposed, and a cover portion disposed on upper and lower surfaces of the coil portion. A grain size in the protective layer is greater than a grain size in the body.