Solid electrolytic capacitor and method for forming a solid electrolytic capacitor
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Solution Overview
Problem
Existing solid electrolytic capacitors face challenges with the mechanical integrity of cathode connections, particularly at high temperatures, due to the degradation of polymeric adhesives and silver migration, leading to increased equivalent series resistance (ESR) and leakage current.
Innovation Solution
The use of sintered transient liquid phase sintering adhesives forms metallurgical bonds between the cathode lead and the lead frame, providing enhanced adhesion and conductivity through metallic interconnections, which are more robust than chemical bonds in traditional polymeric adhesives, and can withstand high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polymeric adhesives are used to attach the cathode layer to the lead frame, then ease of manufacture is improved, but reliability deteriorates at high temperatures due to adhesive degradation and silver migration
Solution Approach 1:
The patent changes the fundamental parameter of the adhesive material from polymeric to metallic composition. The conductive adhesive comprises metal particles (silver, copper, or aluminum) combined with a metallic binder, transforming the material properties to achieve both high-temperature reliability and manufacturability. This parameter change eliminates adhesive degradation and silver migration issues while maintaining ease of application.
2Reliability
If the concentration of conductive particles in the adhesive is increased to improve electrical conductivity, then electrical properties are improved, but adhesive strength deteriorates
Solution Approach 1:
The patent employs a composite material system where metal particles (silver, copper, or aluminum) are combined with a metallic binder in specific proportions. This composite structure allows the conductive particles to provide electrical conductivity while the metallic binder maintains adhesive strength. The synergistic combination resolves the trade-off between conductivity and adhesion by distributing functions across different material phases.
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 solution significantly improves the peel strength and ESR stability of cathode connections, maintaining electrical integrity under high humidity and temperature conditions, while allowing for rapid manufacturing and increased productivity without compromising electrical properties.
Implementation Method 1
The use of sintered transient liquid phase sintering adhesives forms metallurgical bonds between the cathode lead and the lead frame
Implementation Method 2
forms metallurgical bonds between the cathode lead and the lead frame, providing enhanced adhesion and conductivity through metallic interconnections
Implementation Method 3
The adhesive properties of the conductive adhesive, the solder coating on the lead frame, the surface characteristics of lead frame
Data Source
Figure 1~2
Figure 3~4B
AI summary
A solid electrolytic capacitor with an anode and a dielectric on the anode. A cathode is on the dielectric and a conductive coating on said dielectric. A cathode lead is electrically connected to the conductive coating by an adhesive selected from the group consisting of a transient liquid phase sinterable material and polymer solder.