Multilayer Ceramic Capacitor Electrodes for Reliable Wire Bonding
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Solution Overview
Problem
Conventional multilayer ceramic capacitors connected by wire bonding face challenges with high-frequency impedance due to non-uniform external electrode thickness, leading to unreliable connections and reduced moisture resistance, especially as ceramic components are miniaturized.
Innovation Solution
A multilayer ceramic capacitor design with external electrodes having a difference of 3 μm or less in thickness between the center and peripheral portions, and an angle of 4 degrees or less in the field of view, featuring an underlying electrode layer with a metallic and ceramic component, and a plating layer to ensure accurate wire bonding and improved moisture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the external electrode is formed by direct plating to achieve high accuracy, then the thickness uniformity is improved, but moisture resistance is reduced due to moisture penetration between the external electrode and ceramic body
Solution Approach 1:
The patent applies a multi-layer electrode structure consisting of a base electrode layer and a plating layer. The base electrode layer provides adhesion to the ceramic body, while the plating layer (formed by electroplating) provides the desired thickness uniformity and surface quality for wire bonding. This composite structure combines the advantages of different formation methods while mitigating their individual disadvantages.
Solution Approach 2:
The electrode formation process is divided into two distinct stages: first forming a base electrode layer through screen printing or similar methods that ensure good adhesion to the ceramic body, then forming a separate plating layer through electroplating that ensures thickness uniformity. This segmentation allows each layer to optimize for its specific function without compromising the other.
2Ease of manufacture
If conventional wire bonding is performed on non-uniform external electrodes, then the bonding process is simpler, but the connection reliability is reduced due to interference with the external electrode
Solution Approach 1:
The patent replaces the conventional screen printing method with electroplating for forming the external electrode surface layer. This substitution transforms a mechanical/screen-based process into an electrochemical process that naturally produces uniform thickness through controlled deposition, eliminating the thickness variation problems inherent in conventional methods.
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 reliable wire bonding connections and enhanced moisture resistance, reducing high-frequency impedance and improving the functionality of ceramic electronic devices by ensuring a flat and uniform external electrode surface.
Implementation Method 1
a plating layer on the underlying electrode layer
Data Source
AI summary
A multilayer ceramic capacitor includes a multilayer body including dielectric layers and internal electrode layers, and external electrodes electrically connected to the internal electrode layers. A difference of about 3 μm or less exists between a maximum thickness of a center portion of the external electrode and a thickness of a peripheral portion of the external electrode, and in a range of a field of view of about 50 μm square centered at a point located farther inward by about 15% than a peripheral end portion of the external electrode, an angle θ of about 4 degrees or less is defined by a straight line connecting two points of intersection of a surface of the external electrode and a sectional line defining the range of the field of view of about 50 μm square and a perpendicular line to a vertical line passing through one of the two points of intersection.