Electrolytic Capacitor Borate Ester Moisture Management
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Solution Overview
Problem
Conventional electrolytic capacitors with solid electrolyte layers and electrolyte solutions experience a sharp increase in Equivalent Series Resistance (ESR) over time when subjected to long-term load tests at high temperatures, leading to reliability issues.
Innovation Solution
Incorporating a borate ester into the electrolyte solution, which absorbs moisture and suppresses dedoping of the polymer dopant, thereby maintaining low ESR and preventing internal pressure increases during solder reflow processes, while using a conductive polymer and polymer dopant in the solid electrolyte layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional electrolyte solution is used in the electrolytic capacitor, then the capacitor can operate initially, but the ESR increases sharply over time under high-temperature conditions, reducing reliability
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte solution by incorporating a borate ester (specifically a polyalkylene glycol borate ester) into the electrolyte system. This parameter change modifies the electrolyte's interaction with the polymer dopant, preventing moisture-induced dedoping and thereby maintaining low ESR over extended periods under high-temperature operation, which directly addresses the reliability and energy loss contradiction
Solution Approach 2:
The patent creates a composite electrolyte system by combining traditional electrolyte components with a borate ester additive. This composite approach allows the borate ester to specifically address moisture absorption and dopant stabilization while the base electrolyte maintains its primary functions, achieving both initial performance and long-term stability without sacrificing either side
2Ease of manufacture
If moisture is present in the electrolyte solution, then the capacitor can be manufactured and assembled, but moisture causes dedoping of the polymer dopant, increasing ESR and reducing performance
Solution Approach 1:
The borate ester acts as an intermediary substance between the moisture and the polymer dopant. It preferentially binds to moisture through hydrogen bonding and coordination chemistry, preventing moisture from interacting with and extracting the polymer dopant. This intermediary action allows the capacitor to be manufactured with standard moisture levels while maintaining performance stability, resolving the contradiction between manufacturing ease and reliability
Solution Approach 2:
The patent converts the harmful effect of moisture into a beneficial interaction by having the borate ester deliberately and preferentially bind to moisture molecules. This transforms moisture from a harmful contaminant that causes dedoping into a bound species that is effectively sequestered by the borate ester, maintaining capacitor performance while allowing standard manufacturing processes that introduce some moisture
3Ease of manufacture
If the capacitor is subjected to solder reflow processes, then the capacitor can be mounted on circuits, but internal pressure increases due to moisture, risking capacitor failure
Solution Approach 1:
The borate ester performs preliminary action by absorbing and binding moisture in the electrolyte solution before the solder reflow process occurs. This pre-binding of moisture prevents the rapid vaporization and pressure buildup that would otherwise occur during high-temperature soldering, allowing the capacitor to withstand the thermal stress of assembly without internal damage, thus resolving the contradiction between assembly capability and pressure resistance
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 effectively maintains low ESR over time, enhances reliability, and prevents internal pressure increases in electrolytic capacitors, even under high-temperature conditions.
Implementation Method 1
Incorporating a borate ester into the electrolyte solution, which absorbs moisture and suppresses dedoping of the polymer dopant
Implementation Method 2
The solid electrolyte layer is provided on the dielectric layer and includes a conductive polymer and a polymer dopant
Data Source
AI summary
An electrolytic capacitor includes a capacitor element, a solid electrolyte layer, and an electrolyte solution. The capacitor element includes an anode body on a surface of which a dielectric layer is formed. The solid electrolyte layer is provided on the dielectric layer and includes a conductive polymer and a polymer dopant. The electrolyte solution is impregnated into the capacitor element and contains a polyhydric alcohol and a borate ester.