1.Molecular Dynamics Simulation For The Vibration Characteristics Of Nonlinear Optical Material BBO 2.Reliability Research On Flip Chip Electronic Packaging

The thesis is composed of two independent partsIn the first part, the vibration characteristics of a nonlinear optical material β-BaB₂O₄ (BBO) were studied by molecular dynamics simulation The followingaspects were studied l the structure of BBO in glass state, 2 the state density of glassBBO, 3 the vibration characteristics and Rarnan spectra of glass BBO, and 4 thecrystal growth study of RbCl and BBOThe main conclusions in the first part are as followings The structure of BBO inglass state is very familiar to that in molten state The two state densities, calculatedrespectively by Hessian matrix and the autocorrelation function of velocity, were ingood agreement The vibration frequency is between 1200 cm^-1 and 600 cm^-1 or below400 cm^-1 for atom B, 196cm^-1 for atom O and 100 cm^-1 for atom Ba Moreover, thecalculation programs of some correlation functions, Fourier transmissions functionsand related dynamics properties have been developed in the first part Theautocorrelation function of the B-O bond lengths, the intercorrelation function of therelative displacements between O atoms, and the Raman spectra calculated from theFourier transmission have been obtained The simulation results showed that thebreathing mode of BO₃ could roughly reproduce the experimental Raman spectra Atlast, the two-layer crystal-liquid configuration method was carried out for crystalgrowth, which gave out the growth process of RbCl very well in the crystal growthsimulation for BBO, some simple and phenomenal restrictions were tried to modlfiedthe interactive potential and the simulation running of BBO crystal growth have beencarried oat when the ring-bonding restrlction was usedIn the second part, the rellability research of flip chip package was studied by finiteelement method The following aspects are studled 1 the reliability experiments onthe failure of SnPb solder under thermal cycling conditions, 2the viscoelasticmatenal model of underfill, 3 the stress and strain distribution calculated by two-dlmens1onal finlte element slmulatlon, 4 the lnfluence of undemll materlal models onthe rellablllty, 5 the three-dlmenslonal slmulatlon of filp chlp packageThe maln concluslons ln the second part are as follows The thermal cycle llfetlmesof SnPb solder Jolnts for filp chip package were determlned expenmentally Thestress/straln responses of SnPb solder Jolnis under thermal cycllng were slmulatedwlth tWO-dlmenslon fin1te elemeni method and the posltlons of hlgh plastlc stheln lnslmulat1on are ln great agreement wlth the expenmenial crack posltlons 1n cross-sectlon Based on the expenmental thermal cycle lIfet1mes and the calculated p1astlcstraln ranges, the parameters ln Coffin-Manson emplncal equat1on were then fittCdThe results show that the plastlc strsin ranges ln thermal cycllng of solder Jolnts wlthundeffill decreased tremendously The thermal cycle llfet1mes with undeffill areaPproxlmately 20 tlmes larger than that without underfill Moreovef, the lnfiuences ofstandoff helght on solder Jolnt rellablllty are weakened for undeffilled fi1p ch1ppackageThree dlfferent matenal models, l e constant elastlc, temperature dependent elastlcand llnear vlscoelastlc, were employed to represent the mechanlcal propertles ofunderfill U8437-3 The slmulatlon results revealed that the materlal models of, underfill play an lmportant role 1n the plastlc straln range of SnPb solder Jolfit, thedefOrmatlon of package assembly and the lnterfacIal stresses at the ch1P/underfill Itcould be concluded that the elastlc materlal models fOr underfill may overest1mate thethermal fatlgue llfet1mes of SnPb solder Jolnts and the chlpAndeffill lnterfac1alstresses In the deformatlon fOr whole package, the shear dlsplacement decreased andthe warpage 1ncreased with uslng undeffill The hlgheSt lnterfaclal strCss aPpeared atthe comer of chIp, that ls the beglnn1ng poslt1on of the undeffill delamlnalonThe plastlc stra...