Ceramic Electronic Component Dual-Layer External Electrode Solder Burst
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Solution Overview
Problem
Ceramic electronic components face issues with solder burst due to moisture absorption and decomposition in thermosetting conductive pastes, leading to water vapor and gas generation, which can cause solder to be blown off during the reflow step, especially when there are defects or thin portions in the plating film.
Innovation Solution
A ceramic electronic component design featuring a dual-layer external electrode structure, where the inner external electrode includes a mixture of resin and metal components with a first metal component forming an alloy with the internal electrode and a second metal component with a higher melting point forming an alloy with the first, ensuring a metal concentration of at least 17% in the surface layer, and an outer external electrode is applied through plating, effectively preventing solder burst by confining water vapor and decomposition gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermosetting conductive paste containing resin and metal powders is used for the external electrode, then the electronic component can be resistant to shock and heat cycles, but moisture absorption by the resin leads to water vapor and decomposition gas generation causing solder burst
Solution Approach 1:
The external electrode is segmented into a resin-rich inner layer (for shock absorption and adhesion) and a metal-rich outer layer (for gas barrier and conductivity), dividing the functional requirements between two distinct regions within the same electrode structure
Solution Approach 2:
The external electrode uses a composite structure combining resin and metal components in specific layers, where the inner layer has high resin content (60-80 wt%) for mechanical properties and the outer layer has high metal content (80-95 wt%) for gas barrier properties, creating a material system that simultaneously achieves shock resistance and gas containment
2Reliability
If the external electrode layer is plated to form a protective film, then the electrode is protected from corrosion, but defective or thin portions in the plating film allow water vapor and decomposition gas to burst through
Solution Approach 1:
A metal powder layer is applied to the resin-based external electrode before plating, creating a primer layer that improves plating adhesion and ensures uniform plating deposition, thereby preventing thin or defective spots in the final plating film
Solution Approach 2:
The metal powder layer serves as an intermediary between the resin-based external electrode and the plating film, providing a surface that is chemically compatible with both the resin substrate and the plating metal, ensuring uniform and defect-free plating coverage
3Ease of manufacture
If thermosetting conductive paste is directly applied to the ceramic laminate, then the manufacturing process is simplified, but moisture from the ceramic laminate is absorbed by the resin, increasing water vapor generation and solder burst risk
Solution Approach 1:
The external electrode is segmented into a resin-rich inner layer (for shock absorption and adhesion) and a metal-rich outer layer (for gas barrier and conductivity), dividing the functional requirements between two distinct regions within the same electrode structure
Solution Approach 2:
The external electrode uses a composite structure combining resin and metal components in specific layers, where the inner layer has high resin content (60-80 wt%) for mechanical properties and the outer layer has high metal content (80-95 wt%) for gas barrier properties, creating a material system that simultaneously achieves shock resistance and gas containment
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
Significantly reduces or prevents solder burst occurrences by ensuring a uniform and robust external electrode structure that absorbs physical and thermal shocks, maintaining the integrity of the solder and ceramic components during mounting and heat cycles.
Implementation Method 1
a first metal component of which a portion forms an alloy with the internal electrode so as to connect the internal electrode and the inner external electrode to each other
Implementation Method 2
a second metal component higher in melting point than the first metal component, of which a portion forms an alloy with the first metal component so as to connect the inner external electrode and the outer external electrode to each other
Implementation Method 3
a resin is high in hygroscopicity and tends to absorb moisture. As a resin which has absorbed moisture is heated, moisture is vaporized and water vapor is generated in the resin
Implementation Method 4
The water vapor and the decomposition gas are confined by a plating film on a surface of the external electrode
Implementation Method 5
maintaining the integrity of the solder and ceramic components during mounting and heat cycles
Data Source
AI summary
A ceramic electronic component includes a rectangular or substantially rectangular parallelepiped shaped laminate in which a ceramic layer and an internal electrode are alternately laminated and an external electrode provided on a portion of a surface of the laminate and electrically connected to the internal electrode. The external electrode includes an inner external electrode covering a portion of the surface of the laminate and including a mixture of a resin component and a metal component and an outer external electrode covering the inner external electrode and including a metal component. The inner external electrode includes, as a metal component, a first metal component of which a portion forms an alloy with the internal electrode so as to connect the internal electrode and the inner external electrode to each other, and a second metal component higher in melting point than the first metal component, of which a portion forms an alloy with the first metal component so as to connect the inner external electrode and the outer external electrode to each other. A concentration of a metal in a surface layer of the inner external electrode is not lower than about 17%.