Thermal-Mechanical And Hygroscopic Characteristics Of Micro-electronic Packaging Polymer And Its Packaging Reliability Study

Information technology and electronic products have been the largest industries in the world. The core of integrated circuit (IC) is chip. Moreover, every chip has to be packaged suitably before it can be used. With the continuous improvements of IC integration, the electronic packaging, together with IC design and IC manufacturing, become the three stanchions of IC industry.In this dissertation, many emphases are laid on three aspects. One is the fatigue failure of packaging material by experiment and numerical simulation. Another is characteristic of flip chip underfill and flip chip reliability. And the last one is the hygroscopic effect on the viscoelasticity of packaging materials. Concretely the thesis is comprised of followings.Firstly, according to the ASTMD-638 standard, the specimen is made. Then the static tension experiments are studied at room temperature and high temperature. And the stress-strain curve and some mechanics performances of the packaging material are obtained. Next, the tension-tension fatigue experiments are investigated at the room temperature and high temperature separately. Through the test, the stress-strain curve and some mechanics performances and the fatigue life prediction function about the packaging material are gained. And the improved fatigue life of epoxy packaging polymer, which temperature is between 25℃ and 150℃, can be predicted by using the function. At the same time, the S-N curve is obtained at the room temperature.Ruptures of tension and fatigue, at room temperature and high temperature, are investigated. The failure microcosmic mechanisms are discussed by using the scanning electronic microscope. The main failure mechanisms are the delamination between the filler and epoxy, cracking of epoxy or filler at room temperature and the delamination between the filler and epoxy at high temperature because of soften of epoxy. The paper uses finite element modeling to simulate the actual mount, package and temperature cycle processes of a PBGA and that strain and stress are analyzed. Simultaneously the fatigue life is predicted by using the above fatigue life prediction function. The possible and most possible failure positions in epoxy polymer package are found.Secondly, flip chip is of the shortest connection, excellent electronic performance and very high I/O numbers and has the most potentials in high-density package. During the service, package component has to endure periodical cycling temperature due to circuits or environment and so dose the package material. Because of the mismatch of coefficient of thermal expansion and thermal conductivity of every material in thepackage, chip, package material and solder joints must be endured changes of stress and strain and finally result in failure such as chip or solder joints.For improving the thermal-mechanical characteristics of component based on research of thermal conductivity and thermal expansion, carbon fiber and silica filled epoxy underfill is studied and a prediction formula of thermal conductivity and a prediction formula of thermal expansion of fiber and silica filled composite are brought forward. And the best thermal conductivity and the best thermal expansion of underfills, better than now used ones, are predicted. Though finite element simulation, affects of thermal conductivity on temperature proves that high thermal conductive underfill can make temperature distribution equably and therefore decrease the stress and strain, increase the reliability of underfilled package. By comparison of high and low coefficient of thermal expansion (CTE) underfill, Affects of coefficient of thermal expansion on stress shows that if the CTE is doubled, the stress outside the solder joint will be 17～49% greater that of inside the solder joint. Solder joints life for underfilled flip chip are predicted using [C-M] and [E-W] formula and the Engelmaier'results is proved.Thirdly, hygroscopic effects have been one of key problem to the polymer packaging components. Mainly characteristic is high stress and strain induced by the hygroscopic expansion mismatch, delamination, and the changes of viscoelasticity. Tension creep tests prove the moisture effects viscoelasticity and relation between the viscoelasticity and moisture content is obtained. And also the relation between the filler content and moisture content is obtained. At last, moisture effect on the modulus and glass transition temperature are obtained by using the shear tests.