Composition And Properties Of Low Thermal Expansion Coefficient Aluminoborosilicate Electronic Glass Fibers

Low expansion electronic glass fiber has adjustable low coefficient of thermal expansion,low dielectric constant,high specific modulus,high specific strength,good thermal stability,good chemical stability,high temperature resistance,strong impact resistance and many other excellent properties,is the core of chip packaging IC carrier board enhancement materials.At present,the global scope of only the United States of the AGY and Japan’s NTB companies to master the core technology,domestic R&D production is still in the blank stage.The development of low expansion electronic glass fiber has problems such as coefficient of thermal expansion（CTE）to be reduced,high melting and forming temperatures,high boron content and volatility,and poor glass fiber quality due to difficulties in homogenisation.In this thesis,the effects of different ratios of the components Al₂O₃/（MgO+CaO）and MgO/（MgO+CaO）on the structure,density,elastic modulus,thermal stability,CTE,high temperature rheological properties and monofilament properties of low expansion glass fibers were investigated in an aluminoborosilicate glass system.The results of the study show that:As the Al₂O₃/（MgO+CaO）ratio decreases,the total amount of Q³ and Q⁴ in the glass network gradually decreases and the degree of network polymerisation decreases.The density decreases from 2.460 g/cm³ to 2.420 g/cm³,the dielectric constant and dielectric loss increase from 5.22 and 0.23×10^-3 to 5.87 and 1.07×10^-3 respectively,and the modulus of elasticity decreases from 87.70 GPa to 78.70 GPa.The glass transition temperature（T_g）of the glasses gradually decreases.The thermal stability parametersΔT and S for the five groups of glasses had minimal values of 258.64 K and 18.41 K respectively.The CTE of the AR1-AR3 group was below 3.50×10^-6/K and the AR2 group（Al₂O₃/（MgO+CaO）=1.143）achieved a minimal value of 3.11×10^-6/K for CTE.The high temperature viscosity,melt temperature and brittleness values all decrease and then increase,with a gradual decrease in viscous activation energy and free volume.The continuous fiber forming parameter K_fib is more predictive in terms of glass fiber forming properties than the fiber forming temperature intervalΔT.The glass fiber monofilament tensile strength decreased from 1933.97±13.64 MPa to 1506.59±8.10 MPa.As the MgO/（MgO+CaO）ratio increases,the total amount of Q³ and Q⁴ in the network structure increases and then decreases,while the total amount of Q¹ and Q² changes in the opposite direction,and the network polymerisation increases and then decreases.The density of the glass decreases from 2.468 g/cm³ to 2.436 g/cm³,the dielectric constant and dielectric loss decrease from 5.62 and 0.87×10^-3 to 5.17 and 0.21×10^-3,respectively,and the modulus of elasticity increases from 80.83 GPa to 88.68 GPa.The glass transition temperature（T_g）and CTE decrease before increasing,and the thermal stability parametersΔT and S first increased and then decreased,with extreme values of 360.93 K and 42.18 K,respectively.the CTEs of the MR2-MR5 groups were all below 3.50×10^-6/K,with an extremely small value of 3.07×10^-6/K achieved in the MR4（MgO/（MgO+CaO）=0.75）.Melting temperature,viscous activation energy and brittleness are all consistent with high temperature viscosity first decreasing and then increasing,with a gradual decrease in free volume.Again,the continuous fiber forming parameter K_fib is more predictive of the glass fiber forming properties than the fiber forming temperature intervalΔT.The tensile strength of glass fiber monofilaments increased from1732.74±9.47 MPa to 1960.73±12.71 MPa.