Solid Electrolyte Capacitor Welding Control
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Solution Overview
Problem
In solid electrolytic capacitors, the core part of valve metal substrates can liquate during resistance welding, reducing bonding strength between the substrate and spacer, especially as the number of stacked substrates increases, leading to undesired stresses on the negative electrode layer.
Innovation Solution
The solution involves controlling the resistance welding current to ensure only the bonding material in the spacer melts, with the bonding material having a lower melting point than the valve metal substrate, allowing it to penetrate the etching part of the substrate and improve bonding strength, while maintaining a thickness difference between core parts at positive and negative electrode regions within 10% to prevent liquation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If resistance welding is carried out to bond the spacer to the valve metal substrate, then bonding strength is improved, but the core part of the valve metal substrate may liquate out, reducing bonding strength and structural integrity
Solution Approach 1:
The patent changes the physical state parameter of the bonding material by controlling its melting point to be lower than that of the valve metal substrate. This allows the bonding material to melt and penetrate the etching part during resistance welding without causing the core part of the substrate to liquate, thus achieving strong bonding while maintaining structural integrity.
Solution Approach 2:
The patent applies local quality by creating a thickness difference between the core part and the etching part of the valve metal substrate. The etching part has a reduced thickness to facilitate penetration by the melted bonding material, while the core part maintains sufficient thickness to prevent liquation during welding. This localized thickness variation enables selective melting and penetration without compromising overall substrate integrity.
2Quantity of substance
If the number of stacked valve metal substrates is increased to achieve higher capacitance, then product performance is improved, but the welding current increases, making core part liquation more significant
Solution Approach 1:
The patent changes the melting point parameter of the bonding material to be significantly lower than that of the valve metal substrate. This parameter change ensures that even when welding current increases due to stacking more substrates, the bonding material melts at a lower temperature while the substrate core remains solid, preventing liquation and maintaining welding stability regardless of the number of stacked substrates.
3Ease of manufacture
If the bonding material has a low melting point to facilitate penetration, then ease of manufacture is improved, but bonding strength may be reduced if the material is too soft
Solution Approach 1:
The patent optimizes the bonding material's melting point parameter to be lower than the valve metal substrate but not excessively low. This controlled parameter change allows the material to melt and penetrate the etching part effectively during welding, while maintaining sufficient strength after solidification to provide strong bonding between the spacer and substrate.
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 prevents liquation of the core part during welding, enhances bonding strength between the valve metal substrate and spacer, and maintains the integrity of the valve metal substrate, thereby improving the reliability of the solid electrolytic capacitor.
Implementation Method 1
the bonding material is not shown in the figure. When the spacer 2 is superimposed on the positive electrode part of the valve metal substrate 1 as shown in FIG. 8(A), and resistance welding is carried out, the core part 3 of the valve metal substrate 1 may liquate out as shown in FIG. 8(B) depending on conditions for resistance welding
Implementation Method 2
resistance welding is carried out, the core part 3 of the valve metal substrate 1 may liquate out as shown in FIG. 8(B) depending on conditions for resistance welding because a heavy current passes in resistance welding
Data Source
AI summary
In a solid electrolytic capacitor, resistance welding is carried out to bond a valve metal substrate and a spacer together while controlling a welding current so that only a bonding material provided in spacers and having a relatively low melting point is melted. At least a portion of the bonding material provided in the spacer penetrates an etching part of the valve metal substrate, and thickness Ta of a core part located at a positive electrode part in the valve metal substrate and thickness Tc of the core part located at a negative electrode part satisfy the requirement of |Tc−Ta|/Tc×100≦10[%].