Ceramic Capacitor with Wrapping Cu Electrodes for Low ESL
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Solution Overview
Problem
Ceramic capacitors face challenges in reducing equivalent series inductance (ESL) and adhesion to substrates, leading to issues with embedding into smaller-sized devices and increased risk of breakage or cracking due to low strength and poor electrical connections.
Innovation Solution
A ceramic capacitor design with Cu plated external electrodes and extended internal electrode portions to reduce ESL and improve adhesion, featuring a specific geometry and layer structure that enhances reflectivity to laser irradiation for via hole formation and increases the surface area for better substrate integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the height dimension of ceramic capacitors is reduced for embedding into substrates, then the capacitor becomes suitable for compact electronic devices, but the strength of the capacitor decreases causing breakage or cracks
Solution Approach 1:
The external electrodes are designed to extend not only on the principal surfaces but also wrap around the side surfaces of the capacitor body. This three-dimensional electrode configuration distributes mechanical stress across multiple surfaces and dimensions, preventing crack propagation that would normally occur in reduced-height capacitors. The electrodes act as reinforcement elements that span across potential fracture zones.
Solution Approach 2:
The external electrodes employ a multi-layer composite structure consisting of a Cu plated layer (for electrical conductivity and laser reflectivity), a NiCr or NiCu intermediate layer (for adhesion and stress distribution), and a base electrode layer. This composite construction provides both mechanical strength to prevent breakage and the required electrical properties for high-frequency applications.
2Reliability
If conventional multi-terminal capacitors are used, then ESL is reduced for high frequency use, but embedding into substrates and electrical connection to wirings becomes difficult
Solution Approach 1:
The capacitor incorporates multiple internal electrodes (at least three) that are selectively extended to different side surfaces. This segmentation allows different electrodes to be positioned optimally for both low ESL performance and substrate embedding. The extended portions of internal electrodes that reach side surfaces enable direct electrical connection to substrate wirings through via holes, simplifying the manufacturing process for built-in capacitors.
Solution Approach 2:
Internal electrodes are extended from their conventional position solely on principal surfaces to also reach the side surfaces of the capacitor body. This dimensional extension creates additional connection points that facilitate both low-inductance current paths and easy electrical connection to substrate wirings through lateral via holes, resolving the conflict between performance and manufacturability.
3Volume of moving object
If ceramic capacitors are built into substrates, then compact electronic devices are achieved, but adhesion to substrates becomes low causing separation and degradation
Solution Approach 1:
External electrodes wrap around the side surfaces of the capacitor body, creating contact areas on multiple surfaces including principal surfaces and side surfaces. When embedded in substrates, this multi-surface configuration increases the total adhesion area between the capacitor and substrate resin, preventing separation and improving reliability against water ingress and connection fracturing.
Solution Approach 2:
The external electrode structure uses a composite material system with Cu plated layer (for reflectivity), NiCr/NiCu intermediate layer (for adhesion promotion), and base electrode layer. This composite construction enhances both the electrical properties and the mechanical adhesion to substrate, preventing the separation issues that plague conventional embedded capacitors.
4Ease of manufacture
If external electrodes have Cu plated layer for laser reflectivity, then via hole formation is facilitated, but manufacturing complexity increases
Solution Approach 1:
The external electrodes incorporate a Cu plated layer specifically engineered with controlled thickness (typically 1-10 micrometers) and surface finish parameters. This parameter optimization ensures sufficient laser beam reflection for clean via hole formation while maintaining electrical conductivity and adhesion properties. The standardized plating parameters make the manufacturing process predictable and controllable despite the multi-layer complexity.
Solution Approach 2:
The electrode structure uses a composite material system where each layer serves a specific function: Cu plated layer (laser reflectivity and conductivity), NiCr/NiCu intermediate layer (adhesion and stress management), and base electrode layer (structural support). This functional segmentation allows optimization of each layer for its specific purpose while maintaining overall manufacturing feasibility through established multi-layer plating techniques.
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 low ESL and improved adhesion to substrates, reducing the risk of breakage and enhancing the reliability of ceramic capacitors in high-frequency applications and compact electronic devices.
Implementation Method 1
the outermost layers of the external electrodes include the Cu plated layers... laser light for irradiation for the formation of the via holes is reflected at high reflectivity by the external electrodes
Data Source
AI summary
A ceramic capacitor that has low ESL and is suitable to be built into a substrate includes a first external electrode including a first portion extending from a portion located on a first principal surface to a portion of a first end surface, a second portion extending from a portion located on a second principal surface to a portion of the first end surface, a third portion extending from a portion located on a first side surface to a portion of the first end surface, and a fourth portion extending from a portion located on a second side surface to a portion of the first end surface. The first external electrode includes an outermost layer that is a Cu plated layer.