Preparation And Properties Of Bn And Aln Doped Pi Composite Films With High Thermal Conductivity

With the continuous improvement of chip technology,integrated electronic components are gradually developing towards high density and high power chips.This tendency will eventually concentrate more heat on the limited volume of the components,making the working environment warmer and even burning the electronic components.Therefore,it is particularly important to find a high thermal conductivity polymer material for electronic circuit integration.In this paper,a series of polyimide（PI）composite films were prepared by in-situ polymerization using polyimide as matrix,aluminum nitride（AlN）,boron nitride（BN）,silane coupling agent modified 560-AlN,550-BN and 560-AlN and550-BN composite fillers as doped phases.The surface modification of the filler particles and the characteristic structure of the polyimide were characterized by infrared spectroscopy（FT-IR）.Scanning electron microscopy（SEM）was used to analyze the dispersion uniformity of filler particles in the matrix and the bonding between the filler particles and the matrix.It was found that the bonding ability between AlN particles and PI matrix was poor,while the agglomeration of BN particles occurred when the content of BN particles was high.To solve these problems,AlN was modified by KH560 to optimize the interface,BN was modified by KH550 to improve the dispersibility.The thermal conductivity of the composite film was studied.It was found that the thermal conductivityλof the composite film increased with the increase of the thermal conductivity filler content,whether it was the single filler or the composite filler,and the thermal conductivity after modification was higher than the unmodified one.At the same time,due to the synergistic effect of the two fillers and the compact accumulation of particles of different sizes,the thermal conductivity of the composite films was improved.The insulation properties of the composite films were analyzed.It was found that the dielectric constant and dielectric loss of the composite films increased with the increase of filler particle content.When 560-AlN was used as filler,the breakdown field strength E and volume resistivityρ_v reached the maximum at 3 vol%,and the maximum values were 230 kV/mm and 1.008×10¹⁴Ω·m.When 550-BN was used as filler,it reached the maximum at 5 vol%and the maximum values were 191.53 kV/mm and 8.832×10¹³Ω·m,respectively.Therefore,3 vol%AlN and 5 vol%BN were the optimum fillers for the electrical properties of the AlN/PI and BN/PI composite films,respectively.When 560-AlN and 550-BN were used as fillers,3 vol%560-AlN was a fixed value,theρ_v and E of the composite films decreased continuously with the increase of 550-BN content.When the fixed value was5 vol%550-BN,theρ_v of the composite films reached the maximum when the content of 560-AlN was 2 vol%,and the value was 1.3×10¹³Ω·m.While the value of E decreased with the increase of filler content,when 550-BN content was 5 vol%and 560-AlN content was 2 vol%,the breakdown field strength of the composite films was 185.47 kV/mm.The mechanical properties of the films showed that the addition of filler particles reduced the tensile strength of PI composite films,but the modified particles could improve the tensile strength of the composite films compared with the unmodified particles.