Hermetic Polymer Capacitor Package for Low ESR in Harsh Humidity
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Solution Overview
Problem
Hermetically sealed capacitors face performance degradation in harsh environmental conditions, particularly high temperature and high humidity, with existing technologies failing to provide high capacitance and low Equivalent Series Resistance (ESR) while maintaining a small footprint and being surface mountable.
Innovation Solution
A hermetically sealed polymer capacitor design featuring a hermetic metal package with multiple sintered tantalum slugs, electrochemically oxidized to create tantalum pentoxide dielectric layers, surrounded by conductive polymer layers, and sealed with a conductive paste to ensure electrical connections, using glass-to-metal seals to maintain moisture content below 25% relative humidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hermetically sealed capacitors use traditional electrolyte solutions or solid conductors, then they can maintain basic electrical function, but they fail to achieve high capacitance and low ESR simultaneously while maintaining small footprint
Solution Approach 1:
The patent uses intrinsically conducting polymer (ICP) material as the cathode conductor, which is a composite material combining organic polymer backbone with conjugated double bonds and dopant molecules. This ICP material provides both high electrical conductivity (reducing ESR) and high capacitance density while maintaining a compact form factor, resolving the contradiction between performance and size.
Solution Approach 2:
The patent optimizes multiple parameters including the polymer chain length, dopant concentration, and cross-linking density of the ICP material to achieve the optimal balance between electrical conductivity and capacitance. By adjusting these parameters, the capacitor achieves low ESR and high capacitance in a small footprint.
2Object-affected harmful factors
If hermetically sealed capacitors are designed for harsh environmental conditions, then they can resist high temperature and humidity, but existing designs still experience performance degradation
Solution Approach 1:
The patent employs a hermetic seal that creates an inert environment inside the capacitor, isolating the ICP cathode conductor from external moisture and oxygen. The seal prevents harmful environmental factors from penetrating into the capacitor interior, thereby maintaining stable electrical performance under high temperature and humidity conditions.
Solution Approach 2:
The patent uses a moisture-absorbing desiccant material placed inside the hermetic seal to actively scavenging any residual moisture. This desiccant acts as a sacrificial element that absorbs moisture over time, protecting the ICP material from degradation and ensuring long-term reliability in harsh environments.
3Reliability
If intrinsically conducting polymer is used as cathode conductor, then high electrical conductivity and benign failure mode are achieved, but proper electrical connection and moisture protection become critical challenges
Solution Approach 1:
The patent uses a conductive adhesive as an intermediary material between the ICP cathode conductor and the external electrical terminals. This conductive adhesive ensures proper electrical connection while being compatible with the polymer material. Additionally, the hermetic seal acts as an intermediary barrier that protects the ICP from moisture without requiring complex encapsulation structures.
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 achieves high capacitance values and low ESR, providing stable performance in harsh environments with a small footprint, suitable for surface mounting.
Implementation Method 1
twoteen sintered tantalum slugs, electrochemically oxidized to create tantalum pentoxide dielectric layers
Implementation Method 2
sealed with a conductive paste to ensure electrical connections, using glass-to-metal seals to maintain moisture content below 25% relative humidity
Data Source
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AI summary
A hermetically sealed polymer capacitor and a method of forming the same are disclosed. The method preferably includes dispensing an amount of conductive paste inside a case and inserting one or more capacitor elements into the conductive paste. The conductive paste may surround sides of the one or more capacitor elements. Optionally, a bushing may be placed on the one or more capacitor elements. The bushing may have one or more holes that allow one or more positive leads coupled to the one or more capacitor elements to pass through. A cover is preferably welded to the opening of the case. The capacitor assembly is preferably dried to evacuate moisture from inside the case. The one or more positive leads are preferably welded to one or more metal tubes of a glass to metal seal (GTMS) in the cover to seal the capacitor assembly.