MLCC Corner Roughness for Thin Electrode Reliability
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Solution Overview
Problem
The challenge lies in miniaturizing multi-layer ceramic capacitors while maintaining high reliability and capacitance, as existing techniques struggle to form thin external electrodes without exposing internal electrodes, which is crucial for both miniaturization and reliability.
Innovation Solution
The solution involves creating a multi-layer ceramic capacitor with a ceramic body that has a corner portion with a surface roughness of 30 nm or more, allowing for increased coatability of external electrodes without trimming or rounding the corners excessively, thereby preventing internal electrode exposure and enabling the formation of extremely thin external electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the outer edge of the side margin is largely trimmed for chamfering to enable thin external electrodes, then the external electrode thickness can be reduced for miniaturization, but the internal electrodes may be exposed reducing reliability
Solution Approach 1:
The invention changes the surface roughness parameter of the corner portion from a smooth surface to a rough surface with Ra ≥ 30 nm. This parameter change allows the external electrode paste to mechanically interlock with the corner portion, preventing exposure even when the corner is not largely trimmed, thus enabling thin external electrodes while maintaining reliability
Solution Approach 2:
The invention performs preliminary roughening of the corner portion surface before external electrode formation. This preliminary action creates an anchoring effect that ensures the external electrode will adhere properly during subsequent thinning processes, preventing internal electrode exposure without requiring excessive trimming
2Length of moving object
If the corner portion is not chamfered to enable thin external electrodes, then miniaturization can be achieved, but the external electrode coatability is insufficient
Solution Approach 1:
The invention changes the surface roughness parameter of the corner portion to Ra ≥ 30 nm, which significantly improves the coatability of external electrode paste. The increased surface area and mechanical interlocking effect from the rough surface allow the paste to adhere properly even without traditional chamfering, enabling both thin external electrodes and ease of manufacture
3Volume of moving object
If the side margin is thinned for miniaturization, then the capacitor size can be reduced, but the corner portion becomes more susceptible to exposure
Solution Approach 1:
The invention changes the surface roughness parameter of the corner portion to Ra ≥ 30 nm, which creates a mechanical anchor that prevents the corner portion from being exposed even when the side margin is thinned for miniaturization. The rough surface ensures the external electrode paste adheres strongly, maintaining reliability while achieving smaller capacitor size
Data Source
AI summary
A multi-layer ceramic capacitor includes: a ceramic body including a multi-layer chip and a side margin, the multi-layer chip including a capacitance forming unit including internal electrodes laminated in a first direction, positions of end portions of the internal electrodes in a second direction orthogonal to the first direction being aligned with one another within a range of 0.5 μm, and a cover covering the capacitance forming unit in the first direction, the side margin covering the multi-layer chip in the second direction, the ceramic body having a main surface facing in the first direction, a side surface facing in the second direction, an end surface facing in a third direction orthogonal to the above directions, and a corner portion connecting those surfaces; and an external electrode covering the end surface and the corner portion, the corner portion having a surface roughness of 30 nm or more.