Multilayer Ceramic Capacitor Insulating Layer Thermal Expansion
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Solution Overview
Problem
Multilayer ceramic capacitors face challenges with low voltage endurance and thermal shock resistance due to exposure of internal electrodes, weak adhesion between ceramic and glass insulating layers, and inadequate compression stress reduction, leading to cracks and reliability issues.
Innovation Solution
A ceramic sintered body with insulating layers composed of a glass component, where the thermal expansion coefficient ratio (α/β) is between 0.25 and 1, ensuring appropriate compression stress and enhanced adhesion, and containing SiO2, BaO, Al2O3, and other components to form a Ba—Ti—Si—O phase, improving mechanical strength and thermal shock resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glass is used for the insulating layer to improve voltage endurance, then voltage endurance is improved, but adhesion between the end surfaces and the glass becomes weak, leading to crack generation due to thermal expansion differences
Solution Approach 1:
The patent changes the thermal expansion coefficient parameter of the insulating layer by selecting specific glass materials (with thermal expansion coefficients of 80 to 150×10^-7/K) to match the ceramic sintered body (100 to 180×10^-7/K). This parameter matching reduces thermal stress and improves adhesion while maintaining voltage endurance.
Solution Approach 2:
The patent uses composite materials by combining glass materials with specific thermal expansion properties with the ceramic sintered body. The glass insulating layer is formed as a composite structure that maintains both good adhesion and high voltage endurance through careful material selection.
2Reliability
If glass is used for the insulating layer, then voltage endurance is improved, but compression stress applied to the insulating layer is insufficient, making it vulnerable to tensile stress from thermal shock
Solution Approach 1:
The patent changes the thermal expansion coefficient parameter of the insulating layer to be within a specific range (80 to 150×10^-7/K) that is close to the ceramic sintered body. This creates sufficient compression stress on the insulating layer through thermal expansion differences, protecting it from tensile stress during thermal shock while maintaining voltage endurance.
3Stability of the object's composition
If the thermal expansion coefficient of the ceramic sintered body is decreased by containing glass as a ceramic component, then thermal expansion matching is improved, but almost no compression stress is applied to the insulating layer, making cracks easy to generate
Solution Approach 1:
The patent optimizes the thermal expansion coefficient of the insulating layer (80 to 150×10^-7/K) to be close to but not identical to the ceramic sintered body (100 to 180×10^-7/K). This controlled parameter difference maintains good thermal expansion matching while generating sufficient compression stress on the insulating layer to prevent cracks.
4Strength
If glass surface is scratched, then tensile stress concentrates on the scratched portion, but without sufficient compression stress, mechanical strength is decreased and thermal shock resistance is poor
Solution Approach 1:
The patent changes the thermal expansion coefficient parameter of the insulating layer to create a controlled mismatch with the ceramic sintered body. This generates compression stress on the insulating layer that counteracts tensile stress concentration at scratch sites, improving both mechanical strength and thermal shock 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
The solution significantly enhances thermal shock resistance, mechanical strength, and adhesion, reducing crack incidence and maintaining reliability under thermal and mechanical stress, while maintaining high electrostatic capacity and voltage endurance.
Implementation Method 1
differences in thermal expansion coefficient between the ceramic sintered body and the glass
Implementation Method 2
tensile stress from the ceramic sintered body to the insulating layer generated by thermal shock
Implementation Method 3
containing SiO2, BaO, Al2O3, and other components to form a Ba—Ti—Si—O phase
Implementation Method 4
a reaction phase where at least one of constituents of the insulating layer is diffused in the dielectric layer
Data Source
AI summary
A multilayer electronic component includes an element body having an internal electrode layer and a dielectric layer. These are substantially parallel to a plane including a first axis and a second axis and are alternately laminated along a third axis direction. Side surfaces facing each other in the first axis direction are respectively equipped with an insulating layer. End surfaces facing each other in the second axis direction are respectively equipped with an external electrode. The insulating layer includes a glass component. A formula (1) of 0.25<α/β<1 is satisfied, where α denotes a thermal expansion coefficient of the insulating layer, and β denotes a thermal expansion coefficient of one of the internal electrode layer and the dielectric layer that is larger than a thermal expansion coefficient of the other layer.