Silicon dioxide plays an irreplaceable role in reducing the thermal expansion coefficient,improving the substrate modulus,and heat resistance of copper clad panels.The high filling of silica can reduce costs,improve thermal conductivity,reduce thermal expansion coefficient,and increase strength.However,as the filling amount increases,the viscosity of the system will sharply increase,and the fluidity and permeability of the material will deteriorate.The dispersion of silica in the resin is difficult,and agglomeration is prone to occur.How to further improve the filling amount of silica in materials is an important research topic in the copper clad plate industry.
　　In the epoxy molding material industry,the filling amount of angular silica is generally less than 70%of the total amount(weight ratio),and after using spherical silica,the filling amount can reach up to 94%;In the copper clad plate industry,the filling amount of angular silicon dioxide is generally less than 40%of the total amount,and after using spherical silicon dioxide,the filling amount can reach up to 60%.Therefore,despite the high price of spherical silica,due to its unique excellent performance,spherical silica is increasingly favored by the copper clad plate industry.
　　1.Situation of domestic and foreign manufacturers of spherical silica
　　The production technology of spherical silica using flame method is mainly mastered by countries such as Japan,the United States,and South Korea,especially Japan's spherical silica production technology has always been at the world's leading level.Spherical silica is the key core raw material for Integrated circuit packaging and copper clad laminate,which is related to national information and national defense security.At present,there are very few enterprises in China that can produce high-purity spherical silica and submicron level spherical silica,mainly distributed in areas such as Lianyungang in Jiangsu,Bengbu in Anhui,and Huzhou in Zhejiang.
　　2.Specification for the use of spherical silica
　　The national standard"GB/T 32661-2016 Spherical Silicon Dioxide Micropowder"released in 2016 specifies the testing methods and specification requirements for spherical silicon dioxide used in copper clad panels.Japanese CCL manufacturers often choose SiO2 with a purity of 99.8%and an average particle size of 0.5μM~1.0μM spherical silica varieties,such as products with grades SO-C2,SO-C3,and SO-25H,are widely used
　　3.Application Technology of Spherical Silica
　　The spherical silica used in copper clad panels is produced by gas combustion flame method.Due to its special surface properties,it has poor compatibility with organic systems in subsequent applications and is difficult to evenly disperse in organic systems,which seriously affects its application effect.Therefore,it is necessary to conduct technical research on the application of spherical silica products.The application technologies of spherical silica mainly include dispersion technology,surface treatment technology,and compounding technology.
　　Decentralization technology
　　In response to the problems of high surface energy,hydrophilicity and oil repellency,easy spontaneous coagulation in organic systems,and difficulty in dispersion of spherical silica powder,the main method is to choose a suitable external force field and appropriate dispersion equipment for dispersion.For submicron sized spherical silica,the dispersion problem of ultrafine spherical silica in copper clad plates can be solved by preparing a pre dispersed solvent based slurry of spherical silica.
　　Mechanical force dispersion mainly relies on mechanical energy such as external shear force or impact force to fully disperse ultrafine particles in the medium.The specific forms include grinding dispersion,colloid grinding dispersion,ball grinding dispersion,and sand grinding