Multilayer Ceramic Capacitor External Electrode Roughness Adhesion
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Solution Overview
Problem
Multilayer ceramic capacitors experience peeling issues with the resin insulating layers in multilayer printed wiring boards, leading to decreased component reliability and moisture ingress, due to inadequate adhesion.
Innovation Solution
A multilayer ceramic capacitor design featuring a ceramic body with stacked layers and external electrodes composed of a sintered metal base layer with a Cu plated layer, where the arithmetic mean roughness of the external electrode surface is greater than the ceramic body surface, ensuring strong adhesion and preventing moisture ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the multilayer ceramic capacitor is built into a multilayer printed wiring board, then the component size and height are reduced, but peeling occurs between the capacitor and resin insulating layers leading to decreased reliability
Solution Approach 1:
The patent applies different surface roughness characteristics to different parts of the capacitor. The external electrode surface is designed with a specific arithmetic mean roughness (Ra) that is greater than the ceramic body surface roughness, creating localized adhesion enhancement at the electrode-resin interface while maintaining the compact overall structure of the capacitor.
Solution Approach 2:
The patent changes the surface roughness parameter of the external electrode by controlling the arithmetic mean roughness (Ra) to be greater than that of the ceramic body surface. This parameter modification enhances the mechanical interlocking between the external electrode and the resin insulating layer, preventing peeling while maintaining the reduced size of the capacitor.
2Volume of moving object
If the capacitor is built into the multilayer printed wiring board, then space is saved, but moisture ingress through peeled sites causes decreased component reliability
Solution Approach 1:
The patent creates a localized protective feature at the external electrode surface by increasing its roughness relative to the ceramic body. This localized surface modification prevents peeling at the electrode-resin interface, thereby blocking the pathway for moisture ingress while maintaining the compact capacitor design.
Solution Approach 2:
The patent converts the potential harm of surface roughness (which could increase area and thus moisture exposure) into a benefit by strategically locating the rougher surface at the external electrode rather than the ceramic body. The increased roughness at the electrode creates mechanical interlocking that prevents peeling and blocks moisture ingress, transforming what could be a disadvantage into a protective feature.
3Strength
If the external electrode surface is made rougher to improve adhesion, then bonding strength increases, but manufacturing complexity increases
Solution Approach 1:
The patent applies surface roughness control selectively only to the external electrode surface, not the entire capacitor. This localized approach achieves the desired bonding strength enhancement at the critical electrode-resin interface while minimizing the overall manufacturing complexity compared to treating the entire capacitor surface.
Solution Approach 2:
The patent modifies the surface roughness parameter of the external electrode in a controlled manner, specifying that the arithmetic mean roughness (Ra) of the external electrode should be greater than that of the ceramic body. This controlled parameter change achieves improved adhesion while maintaining manufacturability through defined rather than arbitrary specifications.
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 design achieves robust adhesion between the capacitor and the resin, preventing peeling and ensuring reliable moisture resistance, even under external forces.
Implementation Method 1
the outermost layer of the plated layer of the external electrode includes a Cu plated layer
Implementation Method 2
a base layer including a sintered metal containing a metal and glass
Data Source
AI summary
A multilayer ceramic capacitor provided in a multilayer printed wiring board includes a ceramic body with a plurality of ceramic layers and internal electrodes stacked, and an external electrode including a base layer that includes a sintered metal containing a metal and glass and a plated layer provided on the surface of the base layer, which is provided on an end surface of the ceramic body to be connected to the internal electrodes. The external electrode includes a principal surface portion disposed on a principal surface of the ceramic body. The outermost layer of the plated layer includes a Cu plated layer. The ratio of arithmetic mean roughness (Ra) at the surface of the ceramic body/arithmetic mean roughness (Ra) at the surface of the external electrode satisfies a condition: about 0.06≦the arithmetic mean roughness (Ra) at the surface of the ceramic body/the arithmetic mean roughness (Ra) at the surface of the external electrode≦about 0.97.