Polyimide Insulated Wire Layer Structure for Crack-Resistant Coils
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Solution Overview
Problem
Conventional insulated wires suffer from insulation failures due to film defects and cracks caused by thermal and mechanical stresses, leading to reduced reliability and performance in electronic equipment.
Innovation Solution
The insulated wire design includes a thermosetting resin adhesion layer and insulating layer with controlled interlayer adhesion properties and varying polyimide resin content, combined with a reinforcing thermoplastic layer, to prevent cracks and ensure high reliability under stress and heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If interlayer adhesion strength is excessively increased to prevent delamination, then adhesion between layers is improved, but cracks occur all over the film when defects generate
Solution Approach 1:
The patent applies local quality by creating different adhesion strength characteristics in different regions of the insulating film. The inner layer (adjacent to conductor) has higher adhesion strength to prevent delamination, while the outer layer has lower adhesion strength to allow stress absorption and prevent crack propagation. This spatial differentiation of adhesion properties resolves the contradiction between preventing delamination and preventing widespread cracking.
Solution Approach 2:
The patent changes the adhesion strength parameter across different layers of the insulating film. By controlling the adhesion strength to be different in the inner layer versus the outer layer (through different resin compositions, crosslinking densities, or material selections), the system optimizes both delamination resistance and crack propagation resistance simultaneously.
2Reliability
If film thickness is increased to satisfy higher PDIV requirements, then insulation performance is improved, but the film cannot stand the stress given by bending
Solution Approach 1:
The patent segments the insulating film into multiple layers with different thicknesses and adhesion characteristics. The inner layer can be thinner with higher adhesion to the conductor, while the outer layer provides additional thickness for PDIV protection. This segmentation allows the total film thickness to meet PDIV requirements while distributing mechanical stress more effectively across layers, preventing bending-induced failure.
Solution Approach 2:
The patent uses composite material structures with different resin compositions in different layers. By combining materials with different mechanical properties (such as different moduli, elongations, or crosslinking characteristics), the multi-layer structure achieves both high PDIV (through sufficient total thickness) and high bending resistance (through material composition optimization in each layer).
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 prevents insulation defects and maintains high reliability even under processing stress or heating, enhancing the performance of coils and electronic equipment.
Implementation Method 1
a film defect becomes easy to generate by a linear expansion difference at the high temperature, or by a thermal shrinkage due to a thermal deterioration
Implementation Method 2
a film defect becomes easy to generate by a linear expansion difference at the high temperature
Data Source
Figure 1~3
Figure 4
AI summary
An insulated wire, containing a conductor, an adhesion layer provided in direct contact with the conductor, and an insulating layer composed of a polyimide resin, which is provided on the adhesion layer, in which, in the adhesion layer, the content rate of a total formula weight of an imide structure represented by Formula (a) in a polyimide resin skeleton is 27% or more and 33% or less; and, in the polyimide resin of the insulating layer, the content rate of a total formula weight of the imide structure in a polyimide resin skeleton is more than 27% and 37% or less: a coil; and an electric or electronic equipment.