Abstract
As the miniaturization of electronic appliances and microprocessors progresses, low-permittivity interlayer materials are becoming increasingly important for their suppression of electronic crosstalk, signal propagation delay and loss, and so forth. Herein, a kind of copolyimide (CPI) film with a “fluorene” rigid conjugated structure was prepared successfully. By introducing 9,9-Bis(3-fluoro-4-aminophenyl) fluorene as the rigid conjugated structure monomer, a series of CPI films with different molecular weights were fabricated by in situ polymerization, which not only achieved the reduction of permittivity but also maintained excellent thermodynamic stability. Moreover, the hydrophobicity of the CPI film was also improved with the increasing conjugated structure fraction. The lowest permittivity reached 2.53 at 106 Hz, while the thermal decomposition temperature (Td5%) was up to 530 °C, and the tensile strength was ≥ 96 MPa. Thus, the CPI films are potential dielectric materials for microelectronic and insulation applications.
Highlights
Polyimides (PIs) have been widely applied in packaging and insulation fields due to their excellent mechanical properties, ease of processing, temperature resistance, and so forth [1,2,3,4,5]
Zhang et al reported that a kind of PI fabricated by fluorinated polybenzoxazole derived from the benzoxazine monomer possessed the combined excellent properties of facile synthesis, easy processability, and low permittivity [13]
Compared to ordinary PI film, introducing a porous structure can significantly suppress the permittivity of polyimide film [15]
Summary
Polyimides (PIs) have been widely applied in packaging and insulation fields due to their excellent mechanical properties, ease of processing, temperature resistance, and so forth [1,2,3,4,5]. Fluorinated or porous PIs could reach relatively low permittivity, undesirable weakened thermal and mechanical properties hinder their practical applications [1,24]. A rigid conjugated network according to the intrinsic molecular structure of polyimide was designed and fabricated to improve all of the dielectric, thermal, mechanical, and hydrophobic properties. A rigid conjugated structure could significantly restrain the intramolecular chain movement and reduce the polarization, which will exhibit satisfactory dimensional stability, low permittivity, and excellent mechanical properties. The successful combination of rigid conjugated structures, flexible ether bonds, and fluorine atoms in the polyimide skeleton reduced the dielectric properties of the polyimide and maintained excellent mechanical and thermal properties
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