Polymeric Monolithic Capacitor Structure for Heat and Moisture Stability
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Solution Overview
Problem
Existing polymeric monolithic capacitors face limitations in high-temperature and high-ripple current applications due to thermomechanical stress, moisture absorption, and electrode corrosion, which affect their reliability and lifespan.
Innovation Solution
The development of a polymeric monolithic capacitor with non-thermoplastic submicron-thick polymer dielectric layers and aluminum-metallized electrodes, where the electrodes have distinct thicknesses for self-healing and mechanical strength, and the polymer dielectric has a high glass transition temperature and specific chemical structure to minimize moisture absorption and maximize energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the polymer dielectric is made thinner to increase energy density, then the volumetric efficiency improves, but the capacitor becomes more susceptible to dielectric breakdown and moisture absorption
Solution Approach 1:
The patent changes the fundamental parameters of the polymer dielectric by using submicron thickness (less than 1 micron) combined with radiation curing to create a cross-linked non-thermoplastic structure. This parameter change allows the thin dielectric to maintain high breakdown voltage resistance despite reduced thickness, resolving the contradiction between energy density and reliability.
Solution Approach 2:
The patent creates a composite structure by combining the polymer dielectric with metallized aluminum electrodes in a vacuum-deposited multilayer configuration. This composite approach enhances the overall reliability of the thin dielectric structure through the protective metallization layers while maintaining high energy density.
2Temperature
If the capacitor operates at higher temperatures to extend operational range, then the temperature stability improves, but thermomechanical stress increases causing degradation
Solution Approach 1:
The patent changes the thermal parameters by selecting polymer dielectrics with glass transition temperatures above 100°C and using radiation curing to create cross-linked structures. These parameter changes enable the capacitor to operate at elevated temperatures while maintaining structural integrity and resistance to thermomechanical stress.
Solution Approach 2:
The patent addresses thermal expansion issues by using a vacuum-deposited monolithic structure where all layers are bonded together, creating a unified thermal expansion behavior. This reduces internal stress during temperature cycling compared to assembled capacitor constructions.
3Loss of energy
If aluminum foil electrodes are used to reduce resistance, then the electrical conductivity improves, but electrode corrosion increases in extreme environments
Solution Approach 1:
The patent uses thin metallized aluminum layers deposited in vacuum instead of thick aluminum foil electrodes. These thin films provide sufficient conductivity while being more resistant to corrosion. The vacuum deposition process creates a dense, adherent metallization that is less susceptible to environmental degradation.
Solution Approach 2:
The patent changes the electrode parameters by using metallized layers with controlled thickness and properties deposited in vacuum. This creates electrodes with optimized balance between conductivity and corrosion resistance, unlike conventional aluminum foil electrodes that are thicker and more prone to corrosion in extreme environments.
4Ease of manufacture
If thermoplastic polymer film is used for ease of manufacture, then the manufacturing process simplifies, but self-healing capability is reduced
Solution Approach 1:
The patent replaces the mechanical self-healing mechanism of thermoplastic films (which rely on melting and flowing) with a chemical self-healing mechanism. The radiation-cured cross-linked polymer provides self-healing through chemical bond formation and rearrangement, eliminating the need for thermal melting while maintaining ease of vacuum deposition manufacturing.
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 configuration enhances the capacitor's ability to withstand extreme thermomechanical environments, reduces electrical resistivity, and extends operational temperature range, leading to improved reliability and energy density while minimizing degradation.
Implementation Method 1
the polymer dielectric is formed with radiation curing of a liquid monomer layer
Implementation Method 2
the polymer dielectric has a high glass transition temperature
Implementation Method 3
PMCs are produced in a one-step process in a vacuum chamber, where the polymer dielectric is formed with radiation curing of a liquid monomer layer
Implementation Method 4
enhances the capacitor's ability to withstand extreme thermomechanical environments
Data Source
AI summary
Prismatic polymer monolithic capacitor structure that includes multiple interleaving radiation-cured polymer dielectric layers and metal layers. Method for fabrication of same. The chemical composition of polymer dielectric and the electrode resistivity parameters are chosen to maximize the capacitor self-healing properties and energy density, and to assure the stability of the capacitance and dissipation factor over the operating temperature range. The termination electrode that extends beyond the active capacitor area and beyond the polymer dielectric layers has a thickness larger than that used industrially to provide resistance to thermomechanical stress. The glass transition temperature of the polymer dielectric is specifically chosen to avoid mechanical relaxation from occurring in the operating temperature range, which prevents high moisture permeation (otherwise increasing a dissipation factor and electrode corrosion) into the structure. The geometry and shape of the capacitor are appropriately controlled to minimize losses when the capacitor is exposed to pulse and alternating currents.