Solid Electrolytic Capacitor Terminal Structure for Low ESR
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Solution Overview
Problem
Solid electrolytic capacitors face challenges in reducing Equivalent Series Resistance (ESR) and Equivalent Series Inductance (ESL) while maintaining a compact size, and there is a need to prevent peeling of capacitor elements from the leading conductor layer, especially in high temperature and high humidity environments, which affects reliability.
Innovation Solution
The design includes a solid electrolytic capacitor with a plurality of capacitor elements stacked such that their current collector layers are electrically connected, a leading conductor layer connected to only one capacitor element, and an insulating resin body covering them. The leading conductor layer is positioned closer to one end surface, and its length is optimized relative to the resin body's dimensions. Conductive particles and plating layers enhance adhesion, and the resin body's surface roughness and chamfered portions improve electrode adhesion and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the anode terminal and cathode terminal are drawn out from the center of the stack to the outside of the resin, then the capacitor structure is simplified, but the ESR and ESL cannot be further reduced and the size cannot be minimized
Solution Approach 1:
The patent transitions from a conventional terminal arrangement to a side-surface mounting configuration. The anode terminal is mounted on one side surface of the resin while the cathode terminal is mounted on an adjacent side surface, representing a dimensional reconfiguration that reduces current path length and optimizes electrical performance while maintaining compact size
2Ease of manufacture
If the external electrode is formed to extend from end surface to main surface without processing the end surface, then the manufacturing process is simplified, but the external electrode poorly adheres and peels off at the boundary
Solution Approach 1:
The patent applies preliminary surface treatment to the resin end surface before external electrode formation. The end surface undergoes processing (such as roughening or chemical treatment) to create enhanced adhesion properties, ensuring that the external electrode firmly bonds to the resin surface and prevents peeling during subsequent manufacturing steps or product lifecycle
Solution Approach 2:
The patent applies different surface properties to different regions of the resin. The end surface where the external electrode contacts receives special surface treatment to enhance adhesion, while other surfaces maintain their original properties. This localized quality enhancement ensures reliable electrode bonding without affecting the overall resin structure
3Reliability
If the leading conductor layer is configured to have a size equal to or larger than the capacitor element, then conduction between the leading conductor layer and capacitor elements is ensured, but the capacitor element expands due to heat and the leading conductor layer peels off
Solution Approach 1:
The patent optimizes the dimensional parameters of the leading conductor layer. Instead of making it equal to or larger than the capacitor element, the conductor layer is designed with specific length and width parameters that ensure adequate electrical contact while accommodating thermal expansion. The parameters are carefully selected to maintain bonding strength under thermal stress
4Quantity of substance
If the capacitor elements are stacked with current collector layers electrically connected, then the capacitance is increased, but the ESR and ESL need to be further reduced
Solution Approach 1:
The patent merges multiple capacitor elements into a stacked configuration where current collector layers of adjacent elements are electrically connected. This combining approach increases total capacitance while the compact stacked arrangement and optimized current paths help control ESR and ESL by reducing parasitic inductance and resistance through the merged structure
Data Source
AI summary
A solid electrolytic capacitor that includes a plurality of capacitor elements each including an anode portion, a dielectric layer, and a cathode portion having a solid electrolyte layer and a current collector layer; a leading conductor layer; an insulating resin body; a first external electrode; and a second external electrode. The plurality of capacitor elements are stacked in layers, with mutually adjacent capacitor elements having their respective current collector layers connected to each other. The current collector layer of only the capacitor element adjacent to the leading conductor layer is connected to the leading conductor layer. The first external electrode is connected to the leading conductor layer at the first end surface.