Preparation And Study On Properties Of Low Dielectric Polyimide

With the rapid development of portable devices,integrated circuits are rapidly developing towards low power consumption,small size,and high performance.With the advent of the 5G era,advanced packaging applications such as fan-out wafer-level packaging emerged in order to reduce signal loss and accelerate signal transmission rates.As one of the key materials,interlayer dielectric materials directly affect signal transmission and device reliability.Among them,polyimide?PI?has become an important interlayer dielectric material because of its excellent comprehensive properties.However,in order to meet the needs of 5G high-frequency and high-speed circuits,it is inevitable to further reduce the dielectric constant and dielectric loss of polyimide.This thesis focuses on this topic and the research works are shown as follows:1.The low dielectric constant and dielectric loss polyimide was prepared through the introduction of fluorine atoms and polymer molecular structure control.First,two kinds of fluorinated diamine?HFBAPP and TFDB?and fluorinated dianhydride monomer?6FDA?were selected,and the polyimide was synthesized by a two-step method.The experimental results show that as the content of HFBAPP gradually increases,the dielectric constant of the polyimide prepared gradually decreases,that is,the smaller the proportion of the imide ring,the lower the dielectric constant.PI1:0possess the lowest dielectric constant of 2.86.But PI2:3 shows the lowest dielectric loss of 0.00595.In terms of mechanical properties,with the gradual increase of the TFDB content,the breaking strength and Young's modulus of the polyimide gradually increased,its breaking strength increased from 93 MPa to 114 MPa,and its elastic modulus increased from 1.73 GPa to 2.69 GPa.But the elongation at break gradually decreases;in terms of thermal properties,as the TFDB content gradually increases,its thermal decomposition temperature?T₅?is increased from 514.4 ? to 519 ? and the glass transition temperature is increased to 337 ?.At the same time,fluorine-containing polyimide proves better hydrophobicity.2.Lower dielectric constant of fluorinated polyimide material was achieved by introducing fluorinated graphene.Firstly,few-layered fluorinated graphene was prepared by solvent thermal intercalation and mechanical stripping of fluorinated graphite,and characterized by TEM and AFM.As the amount of FG added increases,the dielectric constant of FG/PI gradually decreases,the minimum dielectric constant can reach as low as 2.64,and the dielectric loss is less than 0.0026.As the amount of FG added is very little??0.5wt%?,the mechanical properties and thermal do not change significantly.But it is worth noting that the addition of FG improves the hydrophobicity of the polyimide remarkably,and the contact angle is increased from83^o to 92^o.At the same time,the influence on the light transmission performance is limited,and 88%light transmittance is maintained at a wavelength of 550 nm for 0.5wt%addition of FG,indicating that it has a good application prospect in the field of flexible display and lithography.The as-prepared polyimide films possess excellent comprehensive properties,and exhibit wide application prospects in the field of microelectronics,especially in fan-out wafer-level packaging.