Multilayer Ceramic Capacitor Thickness Ratios Prevent Delamination
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Solution Overview
Problem
Multilayer ceramic capacitors (MLCCs) face issues with delamination and cracks due to thermal or mechanical shocks from warpage of printed circuit boards, leading to insulation resistance degradation and reliability concerns, as steps between electrode and dielectric layers create vulnerabilities.
Innovation Solution
The MLCC design includes a ceramic body with specific thickness ratios between the active layer, cover layers, and external electrodes, where 0.25≦S/T≦0.75 and 3≦A/C≦10, along with plating layers, to minimize step-related stress and prevent delamination and warpage cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If internal electrodes are printed on ceramic sheets and stacked, then capacitance is achieved, but steps are generated between marginal portions and dielectric layers causing delamination and cracks
Solution Approach 1:
The patent applies local quality by creating a ground electrode layer with non-uniform thickness. The ground electrode has a first thickness in regions adjacent to internal electrodes and a second thickness (greater than the first) in marginal portions, allowing different regions to serve different functions: the thinner region minimizes steps near electrodes while the thicker region provides mechanical support and stress distribution in marginal areas.
Solution Approach 2:
The ground electrode layer is formed in advance during the green sheet stacking process, before sintering and electrode formation. This preliminary action of creating the ground electrode with controlled thickness variations prevents step formation issues from the outset, rather than attempting to correct them after capacitor assembly.
2Reliability
If thermal shock or mechanical stress is applied, then electrical function is maintained, but delamination and cracks occur due to step stress concentration
Solution Approach 1:
The ground electrode layer acts as a cushioning layer formed beforehand during the green sheet stacking process. By positioning the ground electrode between the internal electrodes and the external electrode, and by controlling its thickness to be greater in marginal portions, it absorbs and distributes thermal and mechanical stress before it can concentrate at step locations, preventing delamination and cracks under thermal shock or PCB warpage conditions.
3Reliability
If moisture infiltrates through delamination or cracks, then insulation resistance degrades, but proper design can prevent infiltration
Solution Approach 1:
The patent converts the potentially harmful effect of step formation into a benefit by using the ground electrode layer to manage the steps. Instead of eliminating steps entirely (which would require redesigning the electrode structure), the ground electrode is deliberately designed with thickness variations that accommodate the steps while preventing moisture infiltration pathways, turning the step defect into a controlled feature that protects against moisture damage.
Data Source
AI summary
A multilayer ceramic capacitor includes a ceramic body; an active layer including a plurality of first and second internal electrodes alternately exposed to both end surfaces of the ceramic body with a dielectric layer interposed therebetween; upper and lower cover layers formed on upper and lower surfaces of the active layer; and first and second external electrodes formed on the end surfaces of the ceramic body, wherein when a thickness of the ceramic body is defined as T, a thickness of the active layer is defined as S, a thickness of the lower cover layer is defined as C, and a distance from an end of a lowermost internal electrode in a length direction to an end of a band portion of an external electrode close to the end of the lowermost internal electrode is defined A, 0.25≦S/T≦0.75 and 3≦A/C≦10 are satisfied.