Liquid Crystal Polymer Film Void Distribution for 5G Laminate Stability
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Solution Overview
Problem
The development of polymer films for 5G mobile communication systems requires materials with low dielectric loss tangent and minimal difference in linear expansion coefficient from copper foils to prevent warping and peeling during thermocompression, which existing films fail to adequately address.
Innovation Solution
A polymer film with specific hardness and void area proportion relationships throughout its thickness, utilizing a liquid crystal polymer with repeating units derived from parahydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, and a laminate structure with metal-containing layers to achieve a low dielectric loss tangent and reduced linear expansion coefficient mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a high hardness polymer film is used to achieve low dielectric loss tangent, then the dielectric loss tangent is reduced, but the difference in linear expansion coefficient from copper foil increases causing warping and peeling
Solution Approach 1:
The polymer film is designed with non-uniform void distribution where the void area proportion in the central region (Y) is specifically controlled to be at least 0.10% greater than in the surface layer region (X). This local structural differentiation allows the film to maintain high overall hardness for low dielectric loss while the central voids reduce the linear expansion coefficient to match copper foil, preventing warping and peeling during lamination.
2Reliability
If the void area proportion in the central region is increased to reduce linear expansion coefficient difference, then the linear expansion coefficient matches copper foil better, but the film strength may be compromised
Solution Approach 1:
The invention precisely controls the void area proportion parameter Y in the central region to be at least 0.10% greater than X in the surface layer, while maintaining the overall average void proportion at 0.01% or more but 7.00% or less. This parameter optimization ensures the linear expansion coefficient matches copper foil (15-25 ppm/°C) while the surface layer maintains sufficient density and strength for structural integrity.
Data Source
AI summary
An object of the present invention is to provide a polymer film having a low dielectric loss tangent and a small difference in a linear expansion coefficient from that of a copper foil; and a laminate.The polymer film of an embodiment of the present invention is a polymer film including a liquid crystal polymer, in which a hardness A at a distance of half of a thickness of the polymer film and a hardness B at a distance of 1/10 of the thickness of the polymer film satisfy a relationship of Expression (1A), and in a case where positions at distances of 1/10, 4/10, and 6/10 of the thickness of the polymer film are defined as a position T1, a position T2, and a position T3, respectively; and a region from the one surface to the position T1 is defined as a first surface layer region, and a region from the position T2 to the position T3 is defined as a central region, a void area proportion X in the first surface layer region and a void area proportion Y in the central region satisfy a relationship of Expression (2A).(Hardness A+Hardness B)/2≥0.10 GPa Expression (1A)Void area proportion Y−Void area proportion X≥0.10% Expression (2A)