Sinter Bonded Anode Leadwires for Low ESR Solid Electrolytic Capacitors
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Solution Overview
Problem
Conventional solid electrolytic capacitors face challenges in achieving ultralow equivalent series resistance (ESR) due to resistance issues from the anode termination to the lead wire, especially with high specific charge powders that tend to shrink and separate from the anode wire during sintering, increasing ESR.
Innovation Solution
A solid electrolytic capacitor design featuring a sintered porous anode body with a lead assembly containing two sinter-bonded anode wires, where one wire is larger for connection to the anode termination and the other is smaller for enhanced contact with the anode body, reducing path length and resistance, and formed using a valve metal composition with high specific charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lead wire diameter is increased to decrease resistance, then the resistance in the wire and between the wire and anode body decreases, but the capacitance is reduced by displacing porous anode body material
Solution Approach 1:
The patent divides the single lead wire into multiple smaller wires (typically two or more) that are positioned at different locations within the anode body. This segmentation allows the current to flow through multiple parallel paths, effectively reducing the overall resistance without requiring any single wire to have a large diameter that would displace anode material. The multiple wires collectively provide lower resistance while preserving capacitance.
2Quantity of substance
If high specific charge powders are used to increase capacitance density, then the capacitance per unit volume increases, but the powders tend to shrink and separate from the anode wire during sintering, increasing ESR
Solution Approach 1:
The patent uses a binder material as an intermediary to prevent the harmful shrinkage and separation of high specific charge powders from the anode wires during sintering. The binder maintains intimate contact between the powder particles and wire surfaces, ensuring good electrical bonding while allowing the use of high specific charge powders to achieve high capacitance density.
Solution Approach 2:
The patent modifies the sintering process parameters, specifically controlling the sintering temperature and atmosphere to minimize powder shrinkage. By optimizing these parameters, the patent enables the use of high specific charge powders while maintaining good electrical contact with the anode wires, thus achieving low ESR alongside high capacitance density.
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 results in a capacitor with significantly reduced ESR and improved mechanical stability, achieving ultralow ESR levels and maintaining excellent electrical performance, particularly effective for capacitors using high specific charge powders.
Implementation Method 1
sintering the compacted powder and the lead assembly to form a porous anode body and to sinter bond the first wire to the second wire
Implementation Method 2
the first and second wire both extending in a longitudinal direction... sinter bonded to
Implementation Method 3
anodically oxidizing the sintered anode body to form a dielectric layer
Implementation Method 4
applying a solid electrolyte to the anodically oxidized sintered anode body
Data Source
AI summary
A capacitor containing a solid electrolytic capacitor element having a porous anode body and an anode lead assembly is provided. At least one wire of the lead assembly is electrically connected to the anode body for connection to an anode termination. The lead assembly contains first and second lead wires embedded within the anode body and extending therefrom in a longitudinal direction. The first and second wires are bonded/fused together during sintering of the anode body (i.e., “sinter bonded”). The bond may be metallurgical, covalent, electrostatic, etc. Sinter bonding of the wires reduces the path length and resistance for current flow within the anode body, thus reducing ESR. This is particularly useful for anode bodies formed from powders of a high specific charge, which tend to shrink away from the wires after sintering. The sinter bonded wires also result in a lead assembly that is more robust and mechanically stable.