Laminated Terminal Electrode Structure for Reliable Coil Connections
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Solution Overview
Problem
Existing coil devices with terminal electrodes formed at low temperatures suffer from poor acid and impact resistance, leading to insufficient connection reliability due to the use of conductive pastes that deteriorate organic components and have poor bonding strength.
Innovation Solution
A coil device with a terminal electrode structure comprising a first electrode layer with low resin content and low resistance, and a second electrode layer with higher resin content, where the second electrode layer is laminated on the first electrode layer to enhance adhesion and resistance, using conductive powders with specific particle sizes and distributions to improve electrical properties and resistance to acid and impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conductive paste with metal fine grains is used to form terminal electrodes at low temperature (250°C or lower), then the organic component in the element body is preserved without deterioration, but the terminal electrodes exhibit poor resistance to acid and impact, resulting in insufficient connection reliability
Solution Approach 1:
The terminal electrode is segmented into multiple layers: a first electrode layer containing conductive paste with metal fine grains for low-temperature formation and good adhesion to the coil, and a second electrode layer with higher resin content for enhanced acid and impact resistance. This segmentation allows each layer to specialize in different functions, resolving the contradiction between low-temperature formation and reliability.
Solution Approach 2:
The terminal electrode uses a composite structure combining conductive paste (metal particles + resin) in the first electrode layer with a resin-rich second electrode layer. This composite material approach enables the electrode to simultaneously achieve low-temperature formability (from the conductive paste) and high reliability (from the protective resin layer), directly resolving the technical contradiction.
2Ease of manufacture
If a single-layer terminal electrode structure is used, then the manufacturing process is simple, but the adhesion strength and connection reliability are insufficient
Solution Approach 1:
The terminal electrode is segmented into two layers applied in sequence: first the conductive paste layer for adhesion and conductivity, then the resin layer for protection. This segmentation maintains manufacturing simplicity through a straightforward two-step process while dramatically improving adhesion strength and connection reliability compared to a single-layer structure.
Solution Approach 2:
The terminal electrode employs a composite two-layer structure combining conductive paste and resin materials. This composite approach enhances adhesion strength and connection reliability while maintaining ease of manufacture through conventional coating and curing processes, resolving the contradiction between manufacturing simplicity and reliability.
Data Source
AI summary
A coil device including: a core containing magnetic particles and a resin component; a coil including a conductor having a coil shape; and a terminal electrode formed on a part of an outer surface of the core and electrically connected to an end of the conductor drawn from the coil. The terminal electrode includes a first electrode layer in contact with the end of the conductor and a second electrode layer located outside the first electrode layer. The first electrode layer and the second electrode layer both include conductive powder and resin, and a content of the resin in the second electrode layer is higher than a content of the resin in the first electrode layer.