Ceramic Capacitor Electrode Structure to Limit Solder Wicking
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Solution Overview
Problem
Multilayer ceramic capacitors become taller after mounting due to solder wetting up to the top surface, leading to increased height and potential cracking issues due to reduced strength.
Innovation Solution
A ceramic electronic component design featuring external electrodes with a base layer and plating layer that covers the lower and side surfaces, an insulating layer on the upper surface, and a boundary between the insulating and plating layers positioned between the upper and lower surfaces, minimizing solder wetting and maintaining component height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the element body is made thinner to reduce the height of the multilayer ceramic capacitor, then the mounting area is reduced, but the strength of the capacitor is deteriorated causing cracks during mounting
Solution Approach 1:
The external electrode is segmented into two distinct layers: a base layer formed on the element body, and a plating layer formed on the base layer. This segmentation allows the base layer to provide mechanical strength and adhesion to the thin element body, while the plating layer provides solderability and prevents solder wicking, thereby resolving the contradiction between reducing height and maintaining strength
Solution Approach 2:
The external electrode uses a composite structure combining the base layer material and plating layer material. The base layer is made of a material suitable for bonding to the ceramic element body, while the plating layer is made of a solderable material. This composite material approach enables the thin capacitor to maintain both structural integrity and electrical connectivity without cracking during mounting
2Ease of manufacture
If the plating layer of external electrodes extends to the top surface of the element body, then solderability is improved, but solder wets up to the top surface causing increase in height after mounting
Solution Approach 1:
The plating layer is applied with local quality differentiation: it covers the base layer on the side surfaces and lower portions of the element body where solderability is needed, but is prevented from extending to the top surface where solder wicking would occur. This localized application of the plating layer ensures adequate solderability while preventing solder from weting up to the top surface and causing height increase
Solution Approach 2:
The base layer acts as an intermediary between the element body and the plating layer. It provides a substrate for the plating layer while controlling the extent of plating material deposition. By forming the plating layer on the base layer rather than directly on the element body, the structure prevents solder from wicking up the electrode while maintaining solderability at the mounting interface
3Reliability
If terminal electrodes are substantially formed on the bottom surface to improve electrical connection, then connectivity is enhanced, but the height cannot be reduced
Solution Approach 1:
Instead of forming terminal electrodes on the bottom surface (conventional approach), the invention inverts the approach by forming external electrodes on the side surfaces of the element body. The base layer is formed on the side surfaces and extends to cover portions of the top and bottom surfaces, providing electrical connection without requiring additional height for bottom-mounted terminals. This inverted electrode configuration achieves reliable connectivity while maintaining reduced height
Data Source
AI summary
A ceramic electronic component includes an element body including a dielectric and internal electrodes; a pair of external electrodes respectively formed on side surfaces of the element body, each of the external electrodes including a base layer and a plating layer formed on at least a part of the base layer, the base layer of each of the external electrodes containing metal and being formed to continuously cover a portion of a lower surface of the element body and the corresponding side surface of the element body connected to the lower surface, the base layer of each of the external electrodes being electrically connected to one or more of the internal electrodes; and an insulating layer formed on an upper surface of the element body, the insulating layer having a thickness that is less than a thickness of the plating layer of each of the external electrodes.