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

In microelectronic packages, generally the chip is encapsulated by a molding compound (MC). The MC provides a mechanical support for the chip and isolates it from the environment and as a result protects the encapsulated chip. It is well known that MC's are polymer-based materials. When packages are exposed to a harsh environment such as to high-temperature storage or to thermal cycling, the mechanical properties of the MC's can change significantly. Consequently this could result into reliability issues of these packages. For a long time, there was no simple and efficient model method available to simulate the mechanical behavior of these packages under thermal aging conditions. As a result, it was hard to forecast the package reliability after a period of thermal aging. Since in our previous work [1,2] the thermomechanical properties of MC's before and after thermal aging were systematically characterized, the above problem was merely solved. A simple and efficient modeling method was proposed to simulate the thermal aging effects on MC's [2]. In this paper, a bi-material sample consisting of a MC layer on a Copper substrate is prepared and used to verify the proposed modeling method at two different thermal conditions: High-temperature storage (HTS) and Temperature cycling (TC). Based on the proposed modeling method the mechanical behavior of the bi-material sample after aging under these (different) thermal conditions are established throug FEM simulation. The simulation results match the experiment results quite well.@en

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