Single Layer Polymer Film for Etching-Resistant Electronic Devices
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Solution Overview
Problem
The industry faces challenges in creating single layer polymer films that are matte in appearance with deep, rich saturated colors, while also providing optical security and durability, especially as electronic devices become thinner and more compact, and existing multilayer structures are prone to etching issues during circuit production processes.
Innovation Solution
A single layer polymer film composed of 60-99 wt% crosslinked polyimide with a gel fraction of 20-100% and a refractive index of 1.74 or less, incorporating 1-40 wt% colorant, textured to achieve an L* color of 30 or less and a 60° gloss of 15 or less, formed through a process involving dianhydrides and diamines, including alicyclic and aliphatic monomers, with crosslinking and texturing to enhance mechanical and chemical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the amount of matting agent is increased to achieve low gloss, then the surface roughness increases and gloss decreases, but the color becomes muted and L* increases
Solution Approach 1:
The patent changes the refractive index parameter of the polyimide base material to 1.74 or less, which fundamentally alters the optical properties. This parameter change enables the film to achieve low gloss through surface texturing (Spv ≥ 6 μm) without requiring high amounts of matting agent that would mute the color. The low refractive index reduces specular reflectance, allowing the surface texture to provide matting effect while preserving color saturation (L* ≤ 30).
Solution Approach 2:
The patent creates a composite material system combining polyimide with refractive index ≤ 1.74, crosslinking agents (forming gel fraction 20-100%), and colorants (1-40 wt%). This composite structure enables simultaneous achievement of low gloss (through crosslinked network and surface texture) and deep saturated colors (through optimized colorant distribution and low refractive index base material), resolving the contradiction between matting effect and color saturation.
2Length of moving object
If the outer layer thickness is reduced to accommodate thinner electronic devices, then the device compactness improves, but the film becomes susceptible to etching during circuit processing
Solution Approach 1:
The patent changes the chemical structure parameter by incorporating crosslinking agents to form a crosslinked polyimide network with gel fraction of 20-100%. This crosslinked structure significantly enhances chemical resistance and etching durability. The crosslinked network creates a three-dimensional structure that resists degradation during pumice, desmear, and plasma processes, allowing the film to maintain its protective function even at reduced thicknesses suitable for thin electronic devices.
Solution Approach 2:
The patent develops a composite material with crosslinked polyimide (gel fraction 20-100%), low refractive index (≤ 1.74), and integrated colorants. This composite structure provides both the mechanical/chemical durability needed for etching resistance and the optical properties required for appearance and security. The crosslinked network acts as a reinforcing structure that protects against etching while maintaining film integrity at thin thicknesses.
3Illumination intensity
If multilayer structure is used to achieve low L* and low gloss simultaneously, then the optical properties improve, but the manufacturing complexity and etching control difficulty increase
Solution Approach 1:
The patent merges the functions of multiple layers into a single layer by incorporating all necessary components (polyimide base material with refractive index ≤ 1.74, crosslinking agents, colorants, and surface texture) into one integrated film. This single layer simultaneously provides low gloss (through surface texturing and low refractive index), deep saturated colors (through optimized colorant distribution), and etching resistance (through crosslinked network), eliminating the need for separate base layer and top layer structures.
Solution Approach 2:
The patent fundamentally changes the refractive index parameter of the polyimide base material to 1.74 or less, which simplifies the overall structure by eliminating the need for multiple layers. This parameter change enables a single layer to achieve the optical properties previously requiring multilayer construction, reducing manufacturing complexity while maintaining color depth (L* ≤ 30) and gloss (60° ≤ 15).
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 solution enables the production of thin, chemically resistant coverlays that maintain low L* color and low gloss properties, resisting etching processes and providing improved durability and optical security for electronic components.
Implementation Method 1
a crosslinked polyimide, having a gel fraction in the range of from 20 to 100%
Implementation Method 2
A surface of the single layer polymer film has been textured and has a maximum roughness (Spv) of 6 μm or more, an L* color of 30 or less and a 60° gloss of 15 or less
Implementation Method 3
a crosslinked polyimide film including a dianhydride and a diamine
Data Source
AI summary
In a first aspect, a single layer polymer film includes 60 to 99 wt % of a crosslinked polyimide, having a gel fraction in the range of from 20 to 100% and a refractive index of 1.74 or less, and 1 to 40 wt % of a colorant. A surface of the single layer polymer film has been textured and has a maximum roughness (Spv) of 6 μm or more, an L* color of 30 or less and a 60° gloss of 15 or less. In a second aspect, a coverlay for a printed circuit board includes the single layer polymer film of the first aspect. In third and fourth aspects, processes are disclosed for forming a single layer polymer film including a crosslinked polyimide film including a dianhydride and a diamine.