Thermoformable Dielectric Composition for Moisture-Safe Silver Circuits
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Solution Overview
Problem
Existing dielectric materials are not effectively used as moisture barriers during thermoforming procedures in capacitive switches, particularly when highly conductive silver is involved, leading to potential moisture interaction and substrate damage, such as cracking or crazing in polycarbonate substrates.
Innovation Solution
A polymer thick film moisture barrier layer dielectric composition comprising thermoplastic urethane resin, thermoplastic phenoxy resin, diacetone alcohol, and fumed silica, which provides a printable and thermoformable layer that protects polycarbonate substrates from moisture penetration and ensures compatibility with conductive silver layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dielectric materials are used as moisture barriers during thermoforming procedures, then the substrate may be damaged (cracking or crazing in polycarbonate), but the electrical elements are not adequately protected from moisture
Solution Approach 1:
The patent uses a composite dielectric material comprising thermoplastic urethane resin, thermoplastic phenoxy resin, diacetone alcohol, and fumed silica. This composite formulation provides both moisture barrier properties and substrate compatibility, preventing both moisture penetration and substrate damage during thermoforming procedures
Solution Approach 2:
The patent modifies the dielectric material composition by incorporating specific ratios of thermoplastic urethane resin (10-50 wt%), thermoplastic phenoxy resin (10-50 wt%), diacetone alcohol (1-20 wt%), and fumed silica (0.1-5.0 wt%). These parameter changes enable the material to simultaneously provide moisture protection and prevent substrate damage
2Reliability
If highly conductive silver is used in capacitive circuits, then electrical performance is improved, but moisture interaction with the silver conductor causes degradation
Solution Approach 1:
The dielectric composition acts as an intermediary protective layer between the highly conductive silver and moisture. The thermoplastic urethane resin, thermoplastic phenoxy resin, and fumed silica create a barrier that prevents moisture from reaching the silver conductor while maintaining the electrical performance of the circuit
Solution Approach 2:
The composite dielectric material provides both moisture barrier properties and electrical insulation, protecting the highly conductive silver from moisture interaction while maintaining circuit performance
3Reliability
If a moisture barrier dielectric layer is added to protect silver conductors, then moisture protection is improved, but the complexity of the circuit construction increases
Solution Approach 1:
The dielectric composition serves multiple functions simultaneously: it provides moisture barrier protection, electrical insulation, and substrate protection during thermoforming. This multi-functionality reduces the need for additional separate protective layers, thereby limiting the increase in construction 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 composition effectively prevents moisture penetration, maintains substrate integrity, and enhances the longevity of capacitive circuits by reducing resistance changes under accelerated aging conditions, as demonstrated by comparative experiments.
Implementation Method 1
a first organic medium comprising 10-50 wt % thermoplastic urethane resin dissolved in an organic solvent
Implementation Method 2
mitigates moisture penetration
Implementation Method 3
0.1-5.0 wt % fumed silica
Implementation Method 4
1-20 wt % diacetone alcohol
Data Source
AI summary
This invention is directed to a polymer thick film moisture barrier layer dielectric composition comprising thermoplastic urethane resin, thermoplastic phenoxy resin, diacetone alcohol and fumed silica. Dielectrics made from the composition can be used in various electronic applications to protect electrical elements and particularly to insulate and protect both the conductive thermoformable silver above it and the polycarbonate substrate below it in capacitive switch applications.