Performance Of Underfill Materials Used For 3D Chip Packaging And Their Adhesion And Failure Behavior

Recently,three-dimensional integrated circuit(3D IC)heterogeneous integration technology has attracted increasing attention and been developing rapidly,in which the underfill technique palys a very important role,and accordingly the reliability issue associated with adhesion structures using underfill materials has become more and more significant.The robust adhesion interface formed by the underfill adhesive is vitally important for preventing interface cracking and delamination,thereby ensuring the reliability of electronic packaging structures and devices.In this thesis work,firstly the curing process of underfill adhesive materilas was determined based on the study of curing kinetics of underfills.Then,the mechanical performance and failure behavior of the underfill adhesion structures subjected to different curing processes and thermal histories under different loading rates were characterized.Finally,the influence of underfill layer thickness on viscoelastic properties of the underfill and the adhesion failure behavior of the adhered structures were studied.First of all,the curing kinetics model equations of two commencial underfills have been established through thermal analysis kinetic experiments.Based on non-isothermal curing kinetics experiments,a mathematical model related to the curing degree of the underfill,curing time and curing temperature is established.Subsequently,a mathematical model associated with the curing degree and the glass transition temperature(T_g)of the underfill is obtained by means of the study of isothermal curing kinetics,so as to correlate T_g of the underfill,an important material parameter,with the curing condition.The above study and obtained results have certain referential value for the selection of curing process of underfills and the evaluation of T_g of underfills.The results of shear tests of adhered structures using the two types of underfills under different loading rates show that the the shear fracture strength of two underfill adhered structures decreases gradually with the increase of curing temperature,while increasing gradually with increase in the curing degree,the number of reflow and the of loading rate.Except that the increase in the curing degree can reduce voids in the cured underfill matrix,other conditions have no significant effect on the microstructure of the cured underfill.The fracture occurs in adhered structures using two underfills mainly by three types,i.e.,delamination fracture along the upper interface,delamination fracture along the lower interface and the mixed mode fracture of the two.The above attempts and obtained results have important guiding significance for the production and service reliability of underfill packaged devices.Finally,the influences of thickness of underfill film samples on viscoelastic properties of the underfill,the adhesion and failure behavior of adhered structures have been clarified.Specifically,T_g and storage modulus of two underfills decrease slightly as the thickness of the underfill film decreases,in comparison to the increase of fracture strength of the adhered structures with the decrease in thickness of the adhesion layer in the structures.The voids and filler distribution at the interfaces of adhered structures may be the important reasons affecting the adhesion performance and failure behavior of the adhered structures with different adhesion layer thicknesses.