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Breaking the 'Golden Film': A New High Performance Polyimide Ultra Thin Film Based on Special Structural Design
In today's pursuit of lightweight and flexible electronic devices, polyimide (PI) film remains an indispensable key material as the "golden film". However, traditional PI faces severe challenges in the process of ultra-thin (<5 μ m), such as sudden drop in mechanical strength, defect sensitivity, and poor dimensional stability. To break through this bottleneck, innovation must be carried out from the source of molecular structure design. This article introduces a strategy for preparing novel high-performance polyimide ultra-thin films through special molecular structure design, and conducts in-depth research on their disruptive properties.
1、 Innovation Core: Multi dimensional Special Structural Design
This study abandons the traditional single rigid chain structure and adopts a multidimensional collaborative molecular structure design concept. Its core lies in cleverly balancing the rigidity, flexibility, and interaction forces of molecules. The comparison between its design concept and traditional structure on performance is shown in the following figure.
This design is specifically reflected in:
Asymmetric twisted non coplanar structure: Introducing asymmetric biphenyl or large volume side groups in the main chain effectively breaks the tight packing of molecular chains, suppresses the formation of charge transfer complexes (CTCs), not only makes the film color lighter, but also enhances solubility, which is conducive to preparing more uniform precursor gel.
Rigid flexible block synergy: precise embedding of flexible ether bonds (- O -) or cycloaliphatic units in the molecular backbone. Flexible units endow molecular chains with appropriate mobility, making them easier to relax and align during film formation, thereby maintaining good toughness and processability even in ultra-thin states; Rigid elements ensure extremely high thermal stability and mechanical modulus of the material.
Directional intermolecular forces: Introducing specific functional groups (such as amide and carboxyl groups) into monomers to construct strong hydrogen bonding networks between molecules. This physical cross-linking point can significantly enhance the intermolecular interaction force between molecular chains without sacrificing processability, becoming the key to resisting external forces and preventing crack propagation in ultra-thin films.
2、 Precision preparation process of ultra-thin thin films
Based on the aforementioned special structural monomers, an improved casting stretching method was used to prepare ultra-thin films. The precise preparation process is shown in the following figure:
The key to the process lies in the synchronous biaxial stretching technology during the imidization process. In the process of converting PAA gel film into PI, the precisely controlled bidirectional stress is applied to make the molecular chains highly oriented and orderly arranged, which greatly improves the mechanical properties and dimensional stability of the film in the plane, and effectively overcomes the shortcomings of the anisotropy of ultra-thin films.
3、 Performance research: ultra-thin but stronger and more resilient
By testing thin films with a thickness of 3-5 μ m, their performance far exceeds that of traditional ultra-thin PI films:
Mechanical properties: tensile strength>450 MPa, Young's modulus>6 GPa, elongation at break>15%. Its strength is comparable to commonly used copper foil, and it can be repeatedly bent without damage.
Thermal stability: Glass transition temperature (Tg)>380 ° C, coefficient of thermal expansion (CTE)<10 ppm/° C, excellent matching with silicon chips, exhibiting excellent dimensional stability in high and low temperature cycles.
Electrical performance: High surface resistivity, dielectric strength>200 kV/mm, fully meeting the stringent requirements for insulation materials in the microelectronics field.
Comprehensive characteristics: Thanks to the structural design, the film maintains excellent comprehensive performance while having a lighter color (pale yellow) and improved transparency.
4、 Conclusion and Prospect
This study confirms that by combining multidimensional special molecular structure design with precise and controllable preparation processes, the performance degradation problem of polyimide materials in the ultra-thin process can be effectively solved, and a new generation of ultra-thin films with comprehensive performance disruption can be prepared.
This new type of high-performance polyimide ultra-thin film is expected to provide key material support for cutting-edge fields such as next-generation flexible displays (foldable OLEDs), fifth generation communication technology (high-frequency substrates), advanced 3D packaging, and micro flexible sensors, opening up new possibilities for the form innovation and performance leap of electronic devices. Future research will focus on further precise control of structure performance and its service behavior in specific devices.
