Multilayer Ceramic Capacitor External Electrode Moisture Resistance
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Solution Overview
Problem
Multilayer ceramic capacitors with reduced external electrode thickness suffer from decreased moisture resistance due to moisture ingress, compromising insulation resistance and reliability.
Innovation Solution
A multilayer ceramic capacitor design featuring a laminate with alternately stacked dielectric and internal electrodes, where external electrodes include a metal layer covered by a baked layer of glass and metal, and a plated film, with a glass film surrounding the metal layer to prevent moisture entry, and a manufacturing method involving the application of a conductive paste with a high glass content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the external electrode is reduced in thickness, then the size of the multilayer ceramic capacitor is reduced, but moisture resistance reliability deteriorates due to moisture ingress
Solution Approach 1:
The external electrode is constructed as a composite structure with multiple layers: a base metal layer, an intermediate layer containing glass powder and metal powder, and a plated film layer. This composite structure provides both the thin profile needed for miniaturization and the moisture barrier properties required for reliability. The intermediate layer with glass powder specifically blocks moisture ingress while maintaining electrode functionality.
Solution Approach 2:
An intermediate layer is introduced between the base metal layer and the plated film layer. This intermediate layer acts as a mediator that prevents moisture from reaching the base metal layer, thereby protecting against moisture-induced degradation while allowing the overall electrode structure to remain thin. The intermediate layer contains glass powder that forms a moisture barrier.
2Quantity of substance
If the external electrode is reduced in thickness, then the capacitance increases, but insulation resistance deteriorates due to moisture entry
Solution Approach 1:
The external electrode uses a composite structure with an intermediate layer containing glass powder and metal powder. This composite design allows the electrode to be thinner (increasing capacitance) while the glass powder in the intermediate layer prevents moisture ingress that would otherwise degrade insulation resistance.
Solution Approach 2:
The glass powder in the intermediate layer converts the potential harm of moisture ingress into a beneficial moisture barrier. The glass particles create a tortuous path for moisture, effectively blocking it from reaching the metal layers and compromising insulation resistance, while allowing the electrode to maintain thin dimensions for higher capacitance.
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 solution effectively enhances moisture resistance reliability by reducing moisture ingress through the external electrodes, allowing for thinner electrodes while maintaining high capacitance and reliability.
Implementation Method 1
a baked layer including glass and metal, being disposed so as to cover the metal layer
Implementation Method 2
a plated film disposed so as to cover the baked layer
Implementation Method 3
a glass film may preferably be provided around the metal layer while being adjacent to the metal layer on each of the first end surface and the second end surface
Data Source
AI summary
A multilayer ceramic capacitor includes a laminate in which dielectric layers and internal electrodes are alternately stacked, and a pair of external electrodes provided on the corresponding surfaces of the laminate. The laminate includes first and second principal surfaces facing each other in its thickness direction, first and second end surfaces facing each other in its lengthwise direction, and first and second side surfaces facing each other in its width direction. The external electrodes each include a metal layer covering the internal electrodes extended to the corresponding one of the end surfaces, a baked layer including glass and metal covering the metal layer, and a plated film covering the baked layer.