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

@en

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.@en

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.
@en

Delamination of interfaces is known as one of the root causes of failure in microelectronic industry and therefore is getting more and more attention. In order to be able for judging the risk of the interface fracture, the critical fracture properties of the interfaces should be available i.e. Interfacial fracture toughness. Interfacial fracture toughness is highly dependent to temperature, moisture and mode mixity. This work deals with the fracture toughness measurements of an EMC-Cu lead frame interface under pressure cooker conditions ( >100 oC & 100% RH). To deal with it, a chamber with high pressure, i.e. pressure cooker or pressure vessel, is needed. A mixed mode bending setup is installed in the pressure chamber. This will make it possible to have a prescribed opening displacement under combined mode I/ II conditions on a bi-material specimen.@en

In this investigation surface treatment of titanium is carried out by plasma ion implantation under atmospheric pressure plasma in order to increase the adhesive bond strength. Prior to the plasma treatment, titanium surfaces were mechanically treated by sand blasting. It is observed that the contact angle of de-ionized water decreases with the grit blast treatment time. Optical microscopy and scanning electron microscopic (SEM) analysis of untreated and atmospheric plasma treated titanium are carried out to examine the surface characteristics. A substantial improvement in the surface energy of titanium is observed after the atmospheric pressure plasma treatment. The surface energy increases with increasing exposure time of atmospheric pressure plasma. The optimized time of plasma treatment suggested in this investigation results in maximum adhesive bond strength of the titanium. Unmodified and surface modified titanium sheets by atmospheric pressure plasma were adhesively bonded by high temperature resistant polyimide adhesive. The glass transition temperature of this adhesive is 310 1C and these adhesively bonded joints were cured at high temperature. A substantial improvement in adhesive bond strength was observed after atmospheric pressure plasma treatment.@en