Multilayer Ceramic Capacitor Surface Roughness for Void-Free Resin Filling
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Solution Overview
Problem
The existing technologies face challenges in ensuring effective moisture resistance and reliability of multilayer ceramic capacitors due to voids formed between the capacitor and the circuit board, which can lead to reduced moisture resistance and increased stress from bending, especially when the mold resin has difficulty flowing into the small gaps.
Innovation Solution
The solution involves forming multilayer ceramic capacitors with a surface roughness difference between the facing surfaces, where the surface roughness of the lower surface is smaller than that of the side surfaces, facilitating the flow of mold resin and reducing void formation by enhancing wettability and pressure distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mold resin is poured onto the top surface of the mounted multilayer ceramic capacitor to cover the entire surface, then moisture resistance is improved, but voids are formed between the capacitor and circuit board due to difficulty in flowing into small gaps
Solution Approach 1:
The patent applies different surface roughness values to different surfaces of the multilayer ceramic capacitor. Specifically, the lower surface (first surface) has a smaller surface roughness than the side surfaces (second surfaces). This local differentiation allows the mold resin to flow more easily into the gap between the capacitor and circuit board at the lower surface, preventing void formation, while maintaining adequate wettability on the side surfaces for proper encapsulation.
2Reliability
If the surface roughness is increased to improve wettability of mold resin, then moisture resistance is enhanced, but voids are formed due to poor flow into small gaps
Solution Approach 1:
The patent implements local quality by assigning different surface roughness characteristics to different surfaces. The lower surface has a controlled, smaller surface roughness that facilitates mold resin flow into the gap, preventing voids. The side surfaces maintain higher surface roughness to ensure good wettability and adhesion of the mold resin, thus achieving both requirements in different locations.
3Ease of manufacture
If the surface roughness of all surfaces is made uniform, then manufacturing is simplified, but stress from bending is increased and moisture resistance is reduced
Solution Approach 1:
The patent rejects uniform surface roughness in favor of local differentiation. The lower surface has a smaller surface roughness optimized for mold resin flow and void prevention, while the side surfaces have larger surface roughness optimized for wettability. This local quality approach prioritizes reliability over manufacturing simplicity, as the differentiated surface roughness is achieved through controlled processing during capacitor fabrication.
Solution Approach 2:
The patent introduces asymmetry in the surface roughness characteristics of the capacitor. Rather than making all surfaces identical, the lower surface is deliberately made smoother than the side surfaces. This asymmetric design creates optimal conditions for mold resin flow at the critical lower surface while maintaining adequate wettability on the side surfaces, thereby improving moisture resistance and reducing bending stress.
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 prevents voids in the mold resin, improves moisture resistance, and alleviates stress from bending, thereby enhancing the reliability and performance of the multilayer ceramic capacitors.
Implementation Method 1
crimping the plurality of green sheets in a stacking direction with a pressing member
Implementation Method 2
cutting the plurality of green sheets along the stacking direction with a blade
Implementation Method 3
a pair of external electrodes that respectively cover a pair of facing end surfaces of the multilayer structure, and are alternately connected to the plurality of internal electrode layers
Data Source
AI summary
A multilayer ceramic electronic device includes a multilayer structure in which each of a plurality of internal electrode layers and each of a plurality of dielectric layers are alternately stacked, and a pair of external electrodes that respectively cover a pair of facing end surfaces of the multilayer structure, and are alternately connected to the plurality of internal electrode layers along a stacking direction of the multilayer structure. Among four surfaces of the multilayer structure excluding the pair of end surfaces, a surface roughness of at least one of a pair of first surfaces that face each other in the stacking direction is smaller than a surface roughness of at least one of a pair of second surfaces that face each other in an orthogonal direction approximately orthogonal to a facing direction in which the pair of end surfaces face each other and the stacking directions.