Solid Electrolytic Capacitor Thermal Expansion Layer
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Solution Overview
Problem
Solid electrolytic capacitors using conducting polymers as electrolyte layers experience decreased capacitance when stored at high temperatures due to moisture reduction causing contraction and separation of dielectric and conducting polymer layers.
Innovation Solution
A thermal expansion layer with a higher thermal expansion coefficient than the silver paste and resin outer package is provided to contact the exposed conducting polymer layer, reducing stress and preventing separation, thereby maintaining capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conducting polymer is used as an electrolyte layer to reduce ESR, then the equivalent series resistance is reduced, but the capacitance decreases when preserved under high temperature
Solution Approach 1:
The patent changes the thermal expansion parameter by introducing a thermal expansion layer with a specific thermal expansion coefficient that is higher than the conducting polymer layer. This parameter change allows the thermal expansion layer to compensate for the contraction of the conducting polymer layer during high-temperature storage, preventing separation and maintaining capacitance while preserving the low ESR benefit of the conducting polymer electrolyte.
2Stability of the object's composition
If the conducting polymer layer loses moisture under high temperature, then the polymer contracts, but this causes separation from the dielectric layer and capacitance decrease
Solution Approach 1:
The patent applies thermal expansion principles by selecting a thermal expansion layer material with a thermal expansion coefficient higher than that of the conducting polymer layer. During high-temperature storage, this thermal expansion layer expands to compensate for the contraction of the conducting polymer layer caused by moisture loss, thereby preventing separation and maintaining the adhesion between layers while allowing the conducting polymer to maintain its low ESR properties.
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 thermal expansion layer effectively suppresses the decrease in capacitance by expanding with the conducting polymer layer, ensuring the dielectric and conducting polymer layers remain intact at high temperatures, resulting in improved capacitance retention.
Implementation Method 1
a thermal expansion layer which is provided on the side surface of the anode as well as on the conducting polymer layer corresponding to a part of the outer circumferential surface continuing from the side surface; and a resin outer package provided so as to cover the anode, the dielectric layer, the cathode layer, and the thermal expansion layer
Data Source
AI summary
An aspect of the present invention provides a solid electrolytic capacitor that comprises: an anode mainly formed of a valve metal or an alloy thereof; an anode lead terminal a part of which is buried in a side surface of the anode; a dielectric layer formed on surfaces of the anode and mainly formed of an oxide; a conducting polymer layer formed on the dielectric layer; a cathode layer formed on the conducting polymer layer on an outer circumferential surface of the anode, the cathode layer comprising: a carbon layer; and a silver paste layer formed on the carbon layer; a thermal expansion layer provided on the side surface of the anode and on a part of the outer circumferential surface continuing from the side surface; and a rein outer package provided to cover the anode, dielectric layer, cathode layer, and thermal expansion layer, wherein a thermal expansion coefficient in a temperature range lower than a glass transition temperature of the thermal expansion layer is larger than that of each of the silver paste layer and the resin outer package.