Solid Electrolytic Capacitor Thermal Stress Mitigation
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Solution Overview
Problem
Conventional solid electrolytic capacitors face issues with leakage current degradation due to mechanical and thermal stresses, and equivalent series resistance degradation due to thermal expansion coefficient differences between the capacitor and the substrate, especially when mounted on a substrate during temperature cycles.
Innovation Solution
A solid electrolytic capacitor design featuring a base member with insulating plates and conductors in a staggered or zigzag format, using a plate-like or foil-like valve-action metal anode and cathode bodies connected via conductive polymer layers and oxide films, with thermal expansion coefficients between 16 ppm/°C and 26 ppm/°C to mitigate thermal stress and maintain reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If through holes are formed in the porous substance portion and filled with conductors, then cathode conductors are connected to mounting terminals, but cracking occurs in the resin portions and damage occurs in the porous portion due to mechanical and thermal stresses
Solution Approach 1:
An insulating plate is introduced as an intermediary component between the porous substance and the mounting terminals. This plate receives through holes and conductors, serving as a mediator that protects the porous substance from direct mechanical and thermal stress while enabling conductor connection. The insulating plate absorbs the stress that would otherwise damage the porous portion, preventing cracking and maintaining leakage current characteristics.
Solution Approach 2:
The structure is segmented by introducing a separate insulating plate component distinct from the porous substance. This segmentation allows the stress-bearing function to be separated from the capacitor element function, with the insulating plate承担ing mechanical and thermal stress while the porous substance maintains its electrical properties without direct stress exposure.
2Device complexity
If anode and cathode mounting terminals are formed directly on the parent metal and porous substance portion, then terminal connection is simplified, but equivalent series resistance degrades due to thermal stress from difference in thermal expansion coefficients between substrate and capacitor
Solution Approach 1:
The insulating plate serves as a mediator between the capacitor element and the substrate, providing a mounting structure that decouples the thermal expansion differences. By forming mounting terminals on the insulating plate rather than directly on the porous substance, the plate absorbs thermal stress, preventing ESR degradation while maintaining terminal connection functionality.
Solution Approach 2:
The thermal expansion parameters are managed by introducing the insulating plate with appropriate material properties. The plate's thermal expansion coefficient is selected to bridge the gap between the capacitor element and substrate, changing the thermal parameter profile to reduce stress and prevent ESR degradation during temperature cycling.
3Reliability
If the number of mounting terminals is decreased and terminals are disposed in staggered or zigzag format, then loop inductance is reduced, but structural support and insulation become more challenging
Solution Approach 1:
The insulating plate performs multiple functions simultaneously: it provides structural support for staggered or zigzag terminal arrangements, ensures electrical insulation between adjacent terminals, and facilitates simplified mounting terminal formation. This multi-functionality enables complex terminal geometries (for low inductance) without proportionally increasing overall device complexity.
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 design effectively suppresses the degradation of equivalent series resistance and enhances the capacitor's reliability against thermal stress, maintaining excellent characteristics across temperature cycles.
Implementation Method 1
a dielectric made of an oxide film of the parent metal formed on a surface of the parent metal excluding the anode portion
Implementation Method 2
a cathode body made up of a conductive polymer layer overlying the dielectric and a cathode conductor layer overlying the conductive polymer layer
Implementation Method 3
with thermal expansion coefficients between 16 ppm/°C and 26 ppm/°C to mitigate thermal stress and maintain reliability
Data Source
AI summary
A solid electrolytic capacitor is provided which is capable of exhibiting an excellent characteristic and high reliability against thermal stress. The solid electrolytic capacitor includes a base member having a capacitor element connecting face on its upper surface side and an electrode mounting face on its lower surface side and being made up of an insulating plate having first conductors and second conductors, disposed in a staggered format, each providing conduction between the upper and lower surface sides of the base member, and the capacitor element having anode portions and cathode portions, each being disposed in a staggered format, connected to each of the first and second conductors.