Capacitor Anode Wire Bonding With Dual-Density Pressing
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Solution Overview
Problem
The challenge lies in forming a strong bond between high charge density anode powders and anode wires in solid electrolytic capacitors, particularly when using deoxygenation sintering, which often results in inadequate adhesion and dissociation, limiting the use of high CV/g powders due to increased sintering temperatures that reduce surface area and capacitance.
Innovation Solution
A method involving dual-density pressing of anode powders, where a high pressure portion distorts the anode wire, creating a strong bond without degrading the charge capacity, allowing for the use of high CV/g powders and smaller anode sizes, and enabling deoxygenation sintering without the need for additional sintering steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If deoxygenation sintering is used to process high CV/g powders, then the charge density increases, but the bond between anode wire and anode deteriorates leading to dissociation
Solution Approach 1:
The anode wire is inserted into the anode powder before the pressing and sintering operations. This preliminary positioning ensures the wire is properly embedded in the powder structure before densification occurs, allowing the bond to form during the pressing-sintering process rather than attempting to create bonds after the structure is already set
Solution Approach 2:
The pressing operation applies high pressure to densify the anode powder while the wire is embedded, creating a dense structure with strong mechanical interlocking. This pressure-induced densification creates adequate necks between particles and to the wire without requiring excessive sintering temperatures that would reduce surface area
2Strength
If sintering temperature is increased to improve bond strength, then the mechanical strength increases, but the surface area and capacitance decrease
Solution Approach 1:
The anode wire is inserted into the anode powder before pressing, establishing the correct geometric configuration and contact points before densification. This preliminary positioning allows subsequent pressing to create strong mechanical bonds through particle interlocking and deformation rather than relying solely on high-temperature sintering
Solution Approach 2:
High pressing pressure is applied to densify the anode structure, creating strong mechanical bonds through physical deformation and interlocking of particles. This pressure-induced bonding mechanism achieves adequate mechanical strength without requiring excessive sintering temperatures that would reduce surface area and capacitance
3Strength
If welding is used to attach anode wire, then the bond strength improves, but double sintering is required increasing complexity
Solution Approach 1:
The wire insertion and anode formation operations are combined into a single integrated process. The wire is inserted into the powder before pressing, so the bonding occurs simultaneously with the densification process rather than as a separate welding step followed by additional sintering
Solution Approach 2:
The anode wire is inserted into the anode powder before the pressing operation, establishing the correct geometric configuration and contact points before densification occurs. This preliminary positioning allows the bond to form during the pressing-sintering process itself, eliminating the need for separate welding and double sintering operations
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
This approach enhances the mechanical and electrical properties of anodes by maintaining high internal surface area and capacitance, achieving pull strengths over 10 kg and increasing the amount of anode powder within the same volume, while reducing wire length and cost, and allowing for deoxidation sintering with high charge density powders.
Implementation Method 1
pressing a second portion of the anode powder with the anode wire in the second portion to form a high density region with a second density wherein the pressing of the second portion is sufficient to distort the anode wire in the second portion
Implementation Method 2
pressing a portion of the anode powder to form a bulk region having a first density; and pressing a second portion of the anode powder with the anode wire in the second portion to form a high density region with a second density
Implementation Method 3
In each case the anode is sintered and, in the case of a welded wire, prior to anode wire attachment
Data Source
AI summary
An improved capacitor is provided wherein the capacitor has an improved bond between the anode and anode wire. The anode comprises a pressed anode powder comprising a first density region and a second density region wherein the second density region has a higher density than the first density region. An anode wire extends into the second density region wherein the anode wire in the second density region is distorted by compression. This allows for better utilization of the metal powder surface area by allowing a lower bulk press density and lower sinter temperature while still achieving the necessary wire pull strength. In addition, this invention when utilized with deoxidation steps, results in sufficient wire pull strengths not possible otherwise.