Study On The Curing Mechanism And Properties Of Low-dielectric MOFs/Bismaleimide-triazine Resin Nanocomposites

Signal delay and crosstalk in integrated circuits are important factors restricting the development of the microelectronics industry.The development and demand of society require future electronic devices to have better signal transmission efficiency and higher signal propagation speed.As an important part of integrated circuits,Printed Circuit Board(PCB)substrates have a significant impact on the propagation of electronic signals.Therefore,choosing a resin matrix with a low dielectric constant as the adhesive for the PCB substrate has an important effect on the improvement of the dielectric performance.Bismaleimide-triazine resin(BT resin)has attracted wide attention in the field of dielectric communication materials in recent years due to its excellent dielectric properties and high heat resistance.However,the high curing temperature and low dielectric properties of BT resin limited its application in future electronic communication materials.Thus,the development of a new type of BT resin with low dielectric constant,low dielectric loss,and low curing temperature has become an urgent problem to be solved.In this paper,by introducing the pore structure and catalytic sites of MOFs into the BT resin system,BT resin nanocomposites with low curing temperature and excellent dielectric properties was prepared.In this work,three metal-organic frameworks of zeolite imidazole-based zinc-based MOFs(ZIF-8),amino-functionalized titanium-based MOFs(NH₂-MIL-125),and fluorine-functionalized zirconium-based MOFs(F₄-UiO-66)were synthesized.Then,ZIF-8,NH_2-MIL-125,F₄-UiO-66 were used to modify the BT resin,and further studied the curing mechanism,thermodynamic properties,dielectric properties and moisture resistance of different types and different contents of MOFs on the BT resin system impact.The specific research contents were as follows:(1)ZIF-8,NH₂-MIL-125,and F₄-UiO-66 were successfully prepared by reflux method and solvothermal method,respectively.Through a series of characterization methods,it was found that ZIF-8 had a regular dodecahedral crystal morphology,a high specific surface area(1509 m²g^-1)and a microporous structure(1.0 nm).The NH₂-MIL-125 crystal was a regular octahedron,and its specific surface area and micropore diameter were 1250 m²g^-1and 0.66 nm,respectively.Compared with ZIF-8and NH₂-MIL-125,F₄-UiO-66 had low structural regularity,no obvious crystalline morphology,and low specific surface area(282 m²g^-1),showing microporous/mesoporous structure(0.3?3.8 nm).In addition,ZIF-8 and NH₂-MIL-125had strong electronic complexing ability,while the electronic complexing effect of F₄-UiO-66 was not obvious.(2)ZIF-8 was used to modify Bismaleimide-triazine resin,and ZIF-8/BT nanocomposites were prepared.The research results showed that ZIF-8 had a significant catalytic effect on the curing process of BT resin.As the amount of ZIF-8 increased,the curing temperature of the ZIF-8/BT blend continued to decrease.When the addition amount of ZIF-8 reached 0.5 wt%,the DSC curves of the ZIF-8/BT blend was bimodal,corresponding to the self-polymerization of cyanate ester and the copolymerization of cyanate ester and bismaleimide.This was because Zn²⁺and imidazole in ZIF-8synergistically catalyzed the self-polymerization of cyanate esters,which could occur at low temperatures and change the curing process of BT resin.ZIF-8 was evenly dispersed in BT resin and had a certain toughening effect.After adding ZIF-8,due to the formation of more rigid triazine rings,the initial storage modulus of the composites material increased,but the steric hindrance effect of ZIF-8 reduced the crosslink density of the resin system and increased the free volume.Therefore,compared with high-added(?10 wt%)POSS,hollow Si O₂and other inorganic fillers,the ZIF-8/BT resin nanocomposites material was more effective due to the introduction of nanopores,the formation of triazine rings,and the increase in free volume.ZIF-8 with ultra-low addition(?1.0 wt%)effectively reduced the dielectric constant and maintained good heat resistance and moisture resistance of BT resin.(3)NH₂-MIL-125 was added to the Bismaleimide-triazine resin system to prepare the NH₂-MIL-125/BT nanocomposites.The research results showed that NH₂-MIL-125obviously catalyzed the self-polymerization reaction of cyanate ester,reduced the curing temperature,increased the triazine ring in the cross-linked structure,and increased the initial storage modulus of BT resin,but the steric hindrance effect of NH₂-MIL-125reduced the crosslink density and increased the free volume of the nanocomposites system.With the increase of NH₂-MIL-125 addition,in addition to the curing reaction of BT resin,there was also a"Michael"addition reaction between amino group and bismaleimide,which could help to effectively reduce the charge accumulation in BT resin.And it together with the introduction of nanopores,the formation of triazine ring and the increase of free volume reduced the dielectric constant of BT resin.At the same time,NH₂-MIL-125 was evenly dispersed in the BT resin,which could play a significant role in toughening with nanoparticles.In addition,the NH₂-MIL-125/BT nanocomposites system had excellent thermal stability and moisture resistance.(4)F₄-UiO-66/BT nanocomposites was prepared by F₄-UiO-66 modified Bismaleimide-triazine resin.The research results showed that F₄-UiO-66 effectively catalyzed the curing reaction of cyanate esters,promoted the curing of BT resin to form more triazine rings,and increased the initial storage modulus of the BT resin system,but the space steric hindrance of F₄-UiO-66 and the low polarity of the fluorine atom caused the crosslink density of the nanocomposites system to decrease,the free volume increases,and the T_gdecreases.The introduction of F₄-UiO-66 increased the porosity,triazine ring and fluorine atoms,and free volume in the BT reisn system.Thus,the dielectric constant of the F₄-UiO-66/BT nanocomposites was significantly reduced.F₄-UiO-66 was evenly dispersed in the BT resin,which enhanced the toughness of the BT resin and maintained the thermal stability and moisture resistance of the nanocomposites.