MLCC External Electrode Structure for Moisture and Corrosion Resistance
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Solution Overview
Problem
Multilayer ceramic capacitors face challenges in achieving corrosion resistance and moisture resistance reliability, particularly in the connectivity between internal and external electrodes.
Innovation Solution
The development of a multilayer ceramic capacitor design that includes a capacitor body with dielectric and internal electrode layers, and external electrodes with an inner layer of 95 atom % conductive metal and an outer layer containing glass with aluminum oxide (Al2O3) and silicon dioxide (SiO2), enhancing corrosion and moisture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If external electrodes are thinned to enable microminiaturization of MLCCs, then the size of the capacitor is reduced, but the corrosion resistance and moisture resistance reliability deteriorate
Solution Approach 1:
The external electrode is segmented into two distinct layers: an inner layer containing 95-100 atom% conductive metal for electrical connectivity, and an outer layer containing glass (Al2O3 and SiO2) for corrosion and moisture resistance. This segmentation allows each layer to specialize in its primary function, resolving the contradiction between thinning for miniaturization and maintaining protection for reliability.
Solution Approach 2:
The external electrode uses a composite structure combining highly conductive metal material in the inner layer with glass ceramic material (Al2O3-SiO2 system) in the outer layer. This composite approach enables the electrode to simultaneously achieve excellent electrical conductivity, corrosion resistance, and moisture resistance even at reduced thickness, thereby resolving the contradiction between size reduction and reliability maintenance.
2Device complexity
If the thickness of external electrodes is reduced, then manufacturing complexity is decreased, but the connectivity between internal electrodes and external electrodes deteriorates
Solution Approach 1:
The inner layer of the external electrode is designed with locally optimized high conductive metal content (95-100 atom%) specifically at the interface region with internal electrodes. This local quality enhancement ensures excellent electrical connectivity and stable bonding with internal electrodes, while the overall electrode thickness can be reduced. The glass-containing outer layer provides protection without compromising the local connectivity quality at the critical interface region.
Data Source
AI summary
A multilayer ceramic capacitor includes a capacitor body that includes an active portion including dielectric layers and internal electrode layers that are alternately disposed, and cover portions including dielectric layers disposed on upper and lower surfaces of the active portion in the thickness direction, and external electrodes disposed on the capacitor body. The external electrodes include inner layers disposed on the active portion to be electrically coupled to at least one of the internal electrode layers, and outer layers disposed on the inner layers and the cover portions to cover the inner layers. The inner layers include a conductive metal in an amount of 95 atom % to 100 atom % based on the total amount of the inner layers. The outer layers include a conductive metal, and glass including aluminum oxide and silicon dioxide. The thickness of the inner layers is within a range from 1 μm to 3 μm.