Multilayer Capacitor External Electrode for Low ESR and Ion Migration
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Solution Overview
Problem
The formation of silver dendrites due to ion migration in multilayered capacitors and the increase in equivalent series resistance (ESR) due to copper oxidation in conductive resin layers pose challenges, along with issues of thermal decomposition and plating layer breaks.
Innovation Solution
A multilayered capacitor design with a conductive resin layer containing a noble metal, such as silver or platinum, and a metal layer on its surface, along with a sintered metal layer, to minimize noble metal usage and prevent ion migration, while maintaining low ESR and improving plating uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive resin layer including silver (Ag) is used in the external electrode, then good electrical conductivity is achieved, but silver dendrite formation occurs due to ion migration under high humidity and temperature conditions
Solution Approach 1:
A water-repellent coating layer is introduced as an intermediary between the silver-containing conductive resin layer and the external environment. This coating layer prevents moisture from reaching the silver particles, thereby eliminating the electrolyte medium required for ion migration and dendrite formation, while allowing the silver layer to maintain its electrical conductivity function
Solution Approach 2:
The water-repellent coating creates an inert (moisture-free) environment around the silver particles in the conductive resin layer. By excluding water and oxygen from the interface, the coating prevents oxidative and migratory processes that would otherwise degrade the silver layer, thus enhancing long-term reliability
2Reliability
If a conductive resin layer including copper (Cu) is used instead of silver, then ion migration is prevented and cost is reduced, but equivalent series resistance (ESR) increases due to surface oxidation and thermal decomposition
Solution Approach 1:
The water-repellent coating serves as a protective intermediary that prevents environmental factors (water, oxygen) from interacting with the copper particles in the conductive resin layer. This eliminates the root causes of surface oxidation and thermal decomposition, thereby maintaining low ESR and preventing energy loss
Solution Approach 2:
By creating a moisture-free and oxygen-excluded environment through the water-repellent coating, the copper particles are protected from oxidative reactions and thermal degradation. This inert environment preserves the electrical conductivity of the copper layer, preventing ESR increase and associated energy losses
3Object-affected harmful factors
If a water-repellent coating is applied on the surface to prevent silver dendrite formation, then ion migration is reduced, but manufacturing complexity and process steps increase
Solution Approach 1:
The water-repellent coating is designed to perform multiple functions simultaneously: it provides water repellency to prevent ion migration, offers protective barriers against environmental degradation, and maintains electrical insulation properties. This multi-functionality reduces the need for separate protective layers, thereby simplifying the overall device structure despite the additional coating step
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 reduces initial ESR, prevents ion migration, and enhances plating layer formation, thereby improving the capacitor's performance and reliability under temperature changes.
Implementation Method 1
when a temperature drops under high humidity, since moisture is condensed on the multilayered capacitor surface and serves as an electrolyte between both of electrodes
Implementation Method 2
continuous improvement is required in terms of increasing the equivalent series resistance (ESR) by surface oxidation of copper
Data Source
AI summary
A multilayered capacitor including a capacitor body including a dielectric layer and an internal electrode, and an external electrode outside the capacitor body, wherein the external electrode includes a conductive resin layer disposed outside the capacitor body and including a resin and a conductive metal, and a metal layer disposed on a surface of the conductive resin layer and including a noble metal.