We report a molecular modelling study to validate the forcefields [condensed-phase optimised molecular potentials for atomistic simulation studies (COMPASS) and polymer-consistent forcefield (PCFF)] in predicting the physical and thermophysical properties of polymers. This work comprises of two key steps: (1) generating and validating the molecular model in predicting the material properties of the bulk amorphous emeraldine base polyaniline and (2) modelling the glass-rubber transition of the polymer. From all the molecular dynamics simulation results, it clearly shows that the more recent COMPASS forcefield provides a higher accuracy in predicting the polymer properties than PCFF and it enables a more accurate prediction of condensed-phase properties (density, glass transition temperature, solubility parameters, etc.) in a broad range of temperature for various applications.@en

Interface delamination is one of the most important issues in the microelectronic packaging industry. Silver filled die attach is a typical adhesive used between the die and copper die pad for its improved heat dissipation capacity. Delamination between die attach and die pad will severely impact the heat conduction and result in product failure. In order to predict this delamination, interface properties should be characterized. Tri-material, copper-die attach-EMC, samples are made according to the package processes. A four point bending test system is established in order to perform delamination tests at different temperatures using a universal tester Zwick/Roell Z005. In addition, a Keyence optical system is mounted to capture a series of pictures during the delamination processes. This will provide the delamination geometry information needed for determining the interface properties. Four point bending tests have been performed at room temperature, 40, 60, 85, and 150ºC respectively. In addition pre conditioning sample are also tested at room temperature and 85ºC respectively after 48 hours pre conditioned at 85ºC/85%RH. . Experiments show that the ¿critical delamination load¿ decreases steadily with temperature increasing. Experiments also show moisture has no effects on the ¿critical delamination load¿ compared with the dry samples tested at the same temperatures. This means that moisture has no effects on the interface toughness between copper and die attach. To quantify the interface properties, numerical simulations of the four point bending test have been performed by using a finite element model comprising cohesive zone elements which will describe the transient delamination process during the four point bending tests. Correspondently, the interface toughness decreases from 26.5J/m2 at room temperature to 1.9J/m2 at 150ºC as calculated from the cohesive zone element model. These results show that temperature has a large effect on the interface toughness. By means of an extensive model parameter sensitivity study, combined with the measured delamination length in horizontal direction along the copperdie attach interface at room temperature critical opening value has been determined.@en

An increasing number of semiconductor companies have research programs related to MEMS resonators. This can be explained by the possible wide range of application areas. Many resonators operate in vacuum and sealing of the cavity can be obtained by using a Wafer Level Thin Film Package (WLTFP). To fit the MEMS-die into a small package it needs to be thinned. In this paper the effect of wafer thinning on the WLTFP is investigated by means of simulation and experiments. The effects of tape removal on WLTFP's are simulated in 2 and 3 dimensions using the cohesive zones technique. Necessary adhesive properties of the grinding foil are measured by a grinding tape peeling experiment. In 2D FE simulation damage is included to predict the most likely cracking path.@en

In this paper, a fast moisture sensitivity level (MSL) qualification method and a fast moisture characterization method are discussed. The fast moisture characterization uses a stepwise method to obtain more reliable and more material moisture properties. The established relationships for moisture diffusion coefficients and moisture saturation levels with respect to the temperature and relative humidity can be used to predict moisture properties in the MSL range. Fast moisture sensitivity level qualification is accomplished with the aid of simulation combined with the characterized moisture diffusion properties. Moisture absorption processes at different conditions are simulated using a 3D model at conditions according to the moisture sensitivity test levels. Simulation of weight change at different condition and simulation of local moisture concentration are performed and compared between different conditions. Simulations show that at 696 h preconditioning time at 30°C/60%RH for MSL level 2a can be decreased to 42 h at 85°C/85%RH. Time required for package reliability and moisture sensitivity analysis is largely shortened.@en

Despite the fact that epoxy is continuously used as encapsulant in electronic packaging, its joint with copper-based substrate is prone to delaminate during reliability test. A prime reason is the lack of adhesion between Cu and epoxy compound. To solve the problem, self-assembly molecular structure (SAM) is adopted to improve adhesion of epoxy-copper system. In seeing that hydrophobic behaviour of the SAM structure may hinder moisture diffusion along the interface, further work in terms of the molecular structure of the SAM candidates is conducted in this study. This work aims at investigating the moisture effect on the interfacial adhesion with different types of SAM modified interfaces through molecular dynamic (MD) simulations. This study uses MD model as a tool to 1) predict the interfacial adhesion of the SAM modified interface in moisture sensitive condition; 2) investigate the moisture diffusion behavior of the modified interfaces under moisture sensitive conditions. The results demonstrate a reasonable qualitative co-relation between the MD prediction and the TDCB tested data. Nevertheless, without the experimental adsorption data for the SAM material, the moisture diffusion coefficient obtained from MD study cannot explain the adhesion degradation after aging.@en

Molecular dynamics (MD) and molecular mechanical (MM) analysis are carried out to provide reliable and accurate model for emeraldine base polyaniline. This study validate the forcefields and model with the physical and mechanical properties of the polyaniline. The temperature effects on non-bond energy, potential energy and solubility parameter during the transformation from the rubbery to the glassy state have been analysed in this work. A new method using the solubility versus temperature (delta-T) curve for predicting the Tg of polymer are suggested. Keywords: Emeraldine base; molecular dynamics; forcefields; glass transition.@en