Polymeric Monolithic Capacitor High-Temperature Stability
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Solution Overview
Problem
Metallized film capacitors face limitations in reducing thickness and extending operating temperature beyond 125°C while maintaining stable capacitance and dissipation factor, and require improved self-healing and corrosion resistance for high-temperature applications like electric vehicle inverters.
Innovation Solution
Development of polymer monolithic capacitors with multiple dielectric and electrode layers, where at least one dielectric layer has a hydrogen-to-carbon ratio of 1.0 and oxygen-to-carbon ratio of 0.1, and a glass transition temperature greater than 100°C, combined with passivated aluminum electrodes and a specific geometry to enhance self-healing and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of polymer film is reduced to decrease capacitor size, then the dimensions of capacitor are reduced, but the film-manufacturing process limitation prevents thickness reduction below a few microns
Solution Approach 1:
The capacitor is divided into multiple thin dielectric layers (thousands of layers) interleaved with electrode layers. Each individual dielectric layer is vacuum-deposited as an ultrathin film that would be impossible to manufacture as a standalone film, but when stacked together they achieve the required total thickness while maintaining manufacturing feasibility.
2Temperature
If conventional polymer film capacitors are used, then manufacturing is straightforward, but they cannot operate at temperatures exceeding 125°C with stable capacitance and dissipation factor
Solution Approach 1:
The dielectric material parameters are fundamentally changed by using vacuum-deposited polymer layers with specific chemical compositions and cross-linked structures. These material parameter changes enable the capacitor to maintain stable capacitance and dissipation factor at temperatures up to 150°C, exceeding the capabilities of conventional polymer film capacitors.
3Reliability
If metallized polypropylene film capacitors are used for DC-link applications, then self-healing properties are provided, but dissipation factor increases significantly at elevated temperatures
Solution Approach 1:
The capacitor uses a composite structure with vacuum-deposited polymer dielectric layers combined with metal electrode layers. This composite material approach creates a dielectric with optimized properties that maintains low dissipation factor at high temperatures while preserving self-healing capabilities through the metallized electrode structure.
4Use of energy by moving object
If vacuum-deposited ultrathin dielectric layers are used to overcome film thickness limitations, then capacitor energy density increases, but fabrication complexity increases due to cross-linking requirements
Solution Approach 1:
The mechanical film deposition and handling process is replaced with vacuum deposition technology. This substitution enables the creation of ultrathin dielectric layers that cannot be manufactured mechanically, achieving higher energy density while the vacuum process inherently provides the controlled environment needed for cross-linking without additional complex fabrication steps.
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 capacitors exhibit stable dissipation factor and self-healing properties, maintaining performance and minimizing capacitance loss at elevated temperatures, effectively addressing the need for broader temperature range operation and reduced size and cost.
Implementation Method 1
During the fabrication, the dielectric materials are cross-linked with the use of electron beam or UV radiation.
Implementation Method 2
During the fabrication, the dielectric materials are cross-linked with the use of electron beam or UV radiation.
Implementation Method 3
a thickness of a polymer film constituent of such capacitor should be reduced. The reduction of the thickness of the polymer film (such as, for example, a polypropylene film) is limited by the film-manufacturing process to a few microns. The related art (such as U.S. Pat. Nos. 6,165,832; 6,092,269; 5,731,948; 5,716,532; 5,097,800; 5,018,048 and 4,954,371) proposed some solutions to overcome this limitation by devising a new technological approach in which ultrathin vacuum-deposited polymer dielectrics are interleaved with vacuum-deposited metal electrode layers
Data Source
AI summary
Prismatic polymer monolithic capacitor structure operating at temperatures exceeding 140° C. and including multiple interleaving radiation-cured polymer dielectric layers and metal layers. Method for fabrication of same. The geometry of structure is judiciously chosen to increase sheet resistance of metal electrodes while reducing the capacitor's equivalent series resistance. Metal electrode layers are provided with a thickened peripheral portion to increase strength of terminating connections and are passivated to increase corrosion resistance. Materials for polymer dielectric layers are devised to ensure that the capacitor's dissipation factor remains substantially unchanged across the whole range of operating temperatures, to procure glass transition temperature that is no less than the desired operating temperature, and to optimize the absorption of ambient moisture by the polymeric layers.