Currently, the use of electronic components for automotive and aerospace applications is developing quickly. More and more components will be exposed to harsh environments, such as high temperature and high moisture. In general, this high temperature is always above the glass transition temperature (Tg) of the encapsulation material, being Epoxy Molding Compound (EMC). EMC exposed to high temperature could induce reliability problems of components due to changes of its material properties accompanied with volume shrinkage. Therefore, the characterization and modelling of the aging process in EMCs during high-temperature conditions has become an important issue. In our previous work [1], the characterization methods to obtain the material properties as function of aging time were discussed and introduced. The present work focuses on a new and efficient method to model the impact of the aging process of EMCs on the warpage and the stress state of a package using FEM simulation. Here, an “equivalent layer” model, which includes a fully oxidized layer and an unaged core, is applied to simplify the modelling of the thermal aging effects. The current thickness of the “equivalent oxidized layer” is obtained by combining the experimental results and numerical analyses of properly chosen samples. At the end of the paper the aging shrinkage is estimated by using the equivalent thickness concept

It is well known that epoxy moulding compound (EMC) plays an important role in the reliability of electronic packages. In order to predict the mechanical behaviour of electronic packages that are encapsulated with moulding compound, the material properties of EMCs should be carefully characterized and modelled. Currently, more and more components are exposed to severe environments. Among these, high temperature conditions can lead to irreversible changes in EMCs. These changes can be attributed to chemical processes such as oxidation and can lead to degradation of the applied resins, which we refer to here as aging. As a result, the thermo-mechanical properties of the EMCs change severely with time. Due to ongoing changes in the aging EMC of a package, the stress and strain distributions in the package change with time, while embrittlement affects the fracture strength. As a consequence, the long-term reliability of a package is severely affected. Since an appropriate constitutive representation of the material properties of the slowly growing oxidation layers is not available, it is cumbersome to predict the reliability of real packages for long term applications. Being motivated by this limitation, in the present work, we focus on the experimental characterization as well as on the numerical modelling of aging of EMCs at high temperature storage (HTS). As a result the long term stress-strain distribution of a package can be simulated.

This investigation highlights the rationale of adhesive bonding of atmospheric pressure plasma treated high temperature resistant polymeric sheet such as polyimide sheet (Meldin 7001), with titanium sheets. The surface of polyimide (PI) sheet was treated with atmospheric pressure plasma for different exposure times. The surface energy was found to increase with increase in exposure time. However, longer exposure time of plasma, results in deterioration of the surface layer of PI resulting in degradation and embrittlement.

Contact angle measurements with sessile drop technique were carried out for estimation of surface energy. SEM (EDS) and AFM analyses of treated and untreated specimens were carried out to examine the surface characteristics and understanding morphological changes following surface treatment. Untreated samples and atmospheric pressure plasma treated samples of polyimide Meldin 7001 sheet were bonded together as well as with titanium substrates to form overlap joints. Single lap shear tensile testing of these adhesively bonded joints was performed to measure bond strength and to investigate the effect of surface treatment on adhesive bond strength. An optimized plasma treatment time results in maximum adhesive bond strength and consequently, this technology is highly acceptable for aviation and space applications.

The high temperature resistant polymers and metal composites are used widely in aviation, space, automotive and electronics industry. The high temperature resistant polymers and metals are joined together using high temperature adhesives. Polyimide and epoxy adhesives that can withstand high temperature (200 °C-300 °C) are commonly used for joining high temperature metals and polymers. The performance of adhesively bonded metals and polymers depends upon physical properties of these high temperature adhesives. The physical properties like modulus, Tg. coefficient of thermal expansion (CTE) etc., are affected by external factors such as force, temperature, humidity etc. The external factors play a vital role in the adhesive bond strength and the durability of bond between metal and polymer. In this investigation moisture absorption analysis of polyimide adhesive is performed using Q5000 moisture absorption analyzer. The moisture absorption data of polyimide at different temperatures and humidity level is obtained. Further, the moisture absorption data is fitted to well known Fickian-fit model to determine the diffusion coefficient (D) and saturated moisture gain Msat. Diffusion coefficient (D) and Msat of polyimide and epoxy adhesive are calculated at different temperature and different humidity level. It is observed that diffusion coefficient changes with the change in temperature and humidity level. The diffusion coefficient (D) and M sat data are used in Fick¿s second law of diffusion to estimate the time needed for preconditioning of the adhesively bonded titanium samples in humidity chamber at elevated temperature and higher moisture level. After preconditioning of adhesively bonded Titanium samples in moisture chamber for estimated time, samples will be subjected to lap shear tensile test to study the effect of these elevated conditions on adhesive bond strength.

Semi-conductor devices are mostly encapsulated by epoxy molding compound (EMC) materials. During encapsulation, stresses are generated due to the curing of the molding compound. Moreover, additional stresses will build up during cooling down from molding to ambient temperature caused by the differences in the coefficient of thermal expansion. These residual stresses add up to the stresses generated during mechanical loading and may lead to product failure. The viscoelastic properties of the encapsulation material depend highly on temperature and degree of cure. In this paper, the thermo-mechanical properties of an epoxy molding compound with and without filler are investigated both experimentally and theoretically. The cure-dependent properties of the EMCs, likewise, the cure kinetics, coefficient of thermal expansion and cure shrinkage were measured using a Differential Scanning Calorimetry (DSC) and GNOMIX high pressure dilatometer. In addition using a Dynamic Mechanical Analyzer (DMA) the time and temperature dependent storage modulus was measured and mastercurves were constructed.

Delamination between copper and epoxy molding compound (EMC) is one of the common failure modes in packages due to relatively weak adhesion at the interface. Delamination is difficult to predict because a package is often with a complex structure design constructed with different materials and under combined normal and shear loading. Development of cohesive zone elements applied in FEM has emerged into the application of cohesive zones as an effective tool for crack propagation simulation. In this study, a methodology to obtain useful parameters for cohesive zone modeling from experimental measurements is proposed. The approach is demonstrated with the adhesive joint between epoxy molding compound and copper that was under residual stresses and applied mixed-mode loading. The proposed approach to determine the traction-separation function does not rely on the uncertainties of crack tip stresses. The predicted load-displacement result is matched with experimental measurement results at the crack propagation region. Package delamination can be predicted by implementing the proposed testing and modeling scheme within the cohesive zone model.