Multilayer Ceramic Device Electrode Continuity Gradient
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Solution Overview
Problem
Multilayer ceramic electronic devices face issues with crack generation due to contraction strain during sintering and thermal stress, leading to unreliable performance and desired properties, especially when subjected to heat shocks during mounting.
Innovation Solution
The solution involves controlling the continuity of internal electrodes by adjusting their material density, particularly in the topmost, bottommost, and central regions, to reduce stress on ceramic layers, using a nickel or nickel alloy for internal electrodes and maintaining a ceramic layer thickness of 10 μm or less with 100 or more layers, ensuring a 5% to 20% lower average continuity in edge regions compared to the central region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of ceramic layer is decreased and number of laminated internal electrodes is increased to reduce size and increase capacitance, then the size is reduced and capacitance is increased, but peeling occurs at the interface between internal electrode and ceramic layer due to contraction strain during sintering and cracking occurs in ceramic layer
Solution Approach 1:
The patent applies local quality by differentiating the continuity requirements of internal electrodes based on their position within the ceramic laminate. Internal electrodes in the central portion are given higher continuity values than those at the end portions, creating a gradient structure that adapts to the different stress conditions at various locations. This resolves the contradiction by allowing thin ceramic layers and high layer counts for miniaturization while preventing peeling and cracking through position-dependent electrode design.
Solution Approach 2:
The patent changes the parameter of internal electrode continuity across different regions of the laminate. By adjusting the continuity value of internal electrodes from the central portion to the end portions, the patent optimizes the stress distribution and prevents interface peeling and ceramic cracking. This parameter change enables the use of thinner ceramic layers and higher layer counts without compromising reliability.
2Stress or pressure
If materials for internal electrodes are adjusted to decrease continuity toward central portion to suppress contraction stress during sintering, then contraction stress generation is suppressed, but when thermal stress is applied during mounting, stress corresponding to difference in coefficient of thermal expansion is generated causing cracks
Solution Approach 1:
The patent applies local quality by assigning different continuity values to internal electrodes based on their position. The central portion internal electrodes have higher continuity to handle sintering contraction stress, while end portion internal electrodes have lower continuity to accommodate thermal expansion stress during mounting. This position-dependent differentiation resolves the contradiction between suppressing sintering stress and preventing thermal stress cracks.
Solution Approach 2:
The patent changes the continuity parameter of internal electrodes across different regions to simultaneously address both sintering and mounting stresses. By creating a continuity gradient from central to end portions, the patent optimizes performance under both thermal processes, preventing cracks during mounting while maintaining structural integrity during sintering.
3Ease of manufacture
If a multilayer ceramic capacitor is manufactured with uniform internal electrode continuity, then manufacturing is simplified, but cracks are generated in end portions of internal electrodes when heat shock is applied during mounting
Solution Approach 1:
The patent applies local quality by specifying different continuity requirements for internal electrodes at different positions within the laminate. End portion internal electrodes are designed with lower continuity values compared to central portion electrodes, creating a gradient structure that specifically addresses heat shock resistance at vulnerable end regions while maintaining overall manufacturing feasibility through systematic design guidelines.
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 approach effectively reduces stress and prevents crack generation in end portions of the ceramic laminate even under heat shocks, resulting in a highly reliable multilayer ceramic electronic device with improved heat shock resistance and desired electrical properties.
Implementation Method 1
when a thermal stress (heat shock) is applied to the multilayer ceramic capacitor, for example, in a step of mounting it on a circuit substrate by reflow soldering, a stress corresponding to the difference in coefficient of thermal expansion is generated in the ceramic laminate, thereby generating cracks
Implementation Method 2
peeling occurs at the interface between the internal electrode 22 and the ceramic layer 21 due to contraction strain in the ceramic laminate 20a generated during sintering
Data Source
AI summary
A highly reliable multilayer ceramic electronic device is obtained while preventing crack defects generated in a ceramic laminate by application of a heat shock in a mounting step or the like.The multilayer ceramic electronic device is constructed such that the average value of continuities of internal electrodes located in two regions (f) is lower by 5% to 20% inclusive than the average value of continuities of internal electrodes located in the central portion in a lamination direction. The two regions (f) are the regions from the topmost internal electrode and the bottommost internal electrode located in the lamination direction to the inside, respectively, within 10% of the distance (d) therebetween. Continuity is defined by (X−Y)/X in which X is the length of a cross section of an internal electrode in one direction and Y indicates the sum of gaps (g) formed by pores in the cross section of the internal electrode.