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The part of electronics packaging is steadily forced to adapt the requirements of the microelectronic industry. For future electronics application such needs will be: 1) steady miniaturisation of the electronic devices 2) high pin count up to 5000 i / o per device 3) pitches down to 20 mum 4) higher current density per devices 5) higher thermal dissipation loss This is only a small extract of the challenges facing the electronics packaging industry in the future. The aim and duty for electronics packaging is to realize a reliable package for future electronics. Commonplace materials for joining elements like solder are not able to solve these requirements. For example in [1] the authors describe that future IC's operating at high frequencies of 10-28 GHz, signal bandwidths of 20 Gbps and lower supply voltages require an estimated maximum of R (< 10 mOhm), L (<5-10pH) and C (<5-10 fF).[l] Current joining elements can not meet these requirements. To solve these problems the electronics packaging industry researches technologies and materials of the nanotechnology. Especially researches concerning new materials for electronics packaging rise up since the last three years. One of the most researched new materials are Carbon Nanotubes (CNT). Carbon Nanotubes have superior mechanical, electrical and thermal properties. Due to these properties CNT are considered as promising candidates in packaging technology. The most interesting field of application is the use of the Carbon Nanotubes as filler in electrical conductive adhesives. The aim is to improve the performance of conductive adhesives in comparison to common products. This study deals with characterization of carbon nanotube / epoxy adhesives in electronics packaging. For this study we optimize the CNT - adhesive system by modification of the CNT, use of different dispersion technologies and under variation of the epoxy matrix. The resulting adhesives are characterized by measuring their viscosity, mech- anical strength and their thermal and electrical conductivity. For all studies Multi Wall Nanotubes were used which can be purchased at a reasonable price. For modification of the CNT they can be treated by low pressure plasma (cvd), UV / ozone treatment or modifiedchemically in solution to achieve a higher polarity resulting in a better dispersibility. Also bonding to the polymer matrix is improved. Success of the processes is studied by XPS and REM. For dispersion technology ultrasonic bath, speed mixing and/or treatment with a roll calander can be used. The polymer matrix is also varied in order to achieve an appropriate viscosity at the CNT-content of interest that enables good results in screen printing. Also CNT-polymer interaction can be adapted by varying polarity of the resin used. The distribution of CNT in the matrix is studied by TEM. The first investigations show that ultrasonic finger is the favourable dispersion technology to achieve well dispersed CNT. For modification of the CNT the plasma treatment came out to be efficient to give appropriate am...

This paper addresses the influence of the viscoelastic material properties of adhesives on the functionality of SHM (Structural Health Monitoring) sensor applications. Epoxy adhesives behave viscoelastically and show a strong temperature and time dependency of their mechanical properties. Creep processes increase the deformation under mechanical load and relaxation can decrease the stress in the adhesives (polymer) with time. These processes are most effective in the temperature range of glass transition (Tg), at which the material behavior switches between the glassy and rubbery state and all material parameters change drastically. Additional the viscoelastic material properties are influenced by environmental loading like moisture as it behaves like a plasticizer in the epoxy matrix. In this study the moisture influence on the viscoelastic behavior of structural adhesives was investigated by DMA (Dynamic Mechanical Analysis) methodology for harsh environmental loading conditions like DI water immersion and relative humidity (r.h.) environment. For testing under RH (Relative Humidity) conditions, a novel DMA-RH equipment was applied, which allows online testing at different temperatures and RH levels between 0%r.h. and 90%.r.h. Commercially available two component epoxy adhesives (unfilled, high filled) with high potential of acceptance in avionic applications were studied. For the unfilled adhesive a significant material property change due to moisture absorption occured. The modulus decreased down to about 25 percent of the dry state modulus E'. As expected the Tg was reduced for "wet" samples. Additional the change in the time dependence was seen. The high filled adhesive showed much lower diffusion constants and the modulus change was not that remarkable

Organic packaging materials gain a steady increasing importance for electronics packaging assemblies. They are used in various ways in substrate materials, adhesives, encapsulations, underfills and many more. This paper outlines the importance of thermo-mechanical characterization of these polymeric packaging materials to improve the accuracy of Finite Element Modeling for advanced reliability analysis of electronics packaging solutions. Therefore the effects of including temperatureand time dependent mechanical material properties of a PPS molding compound were investigated. This molding compound should be used as a coupling element to decrease the occurring stresses in an array of solder connections between substrate and package. The setup was analyzed by FEM (Finite Element Modeling). For the material characterization a DMA 2980 equipment was utilized to determine the time-and temperature dependent elongation modulus of the molding compound material. A description of the measurement setup and parameter selection is given. Subsequently the measurement results are presented. To use this measurement results in a material model for time dependent elongation modulus the results needed to be fitted to a Prony series model which allows implementing this complex material beh~v!or in the FEM simulation software Ansys®. Additional the WLF (Williams-Landel-Ferry) shift function was determined and implemented to add the temperature effect to the viscoelastic material data used for s!mulation. For the stress analysis the package setup was implemented as geometric model of the real structure and the loading conditions were defined. The simulations showed that there are significant differences in the occurring stress levels in the setup. For higher temperatures the stress levels were decreased due to stress relaxation in the polymer.

This paper addresses the influence of the viscoelastic material properties of adhesives on the functionality of SHM (Structural Health Monitoring) sensor applications. Adhesives behave viscoelastically and show a strong temperature and time dependency of their mechanical properties. Creep processes increase the deformation under mechanical load and relaxation can decrease the stress in the adhesives (polymer) with time. These processes are most effective in the temperature range of glass transition (Tg), at which the material behavior switches between the glassy and rubbery state and all material parameters change drastically. Additional the viscoelastic material properties are influenced by environmental loading like moisture as it behaves like a plasticizer in the epoxy matrix. In this study the moisture influence on the viscoelastic behavior of structural adhesives was investigated by DMA (Dynamic Mechanical Analysis) methodology for different moisture loading conditions. Water immersion (DI) and relative humidity (RH.) at different temperature levels showed the strong temperature dependence of the absorption process. For testing under RH (Relative Humidity) conditions a novel DMA-RH equipment was used. It allows online modulus measurement at temperatures and RH levels between 0% r.h. and 90% r.h. Commercially available two component epoxy adhesives (unfilled, high filled) with high potential of acceptance in avionic applications were studied. For the unfilled adhesive a significant material property change due to moisture absorption occurred. The modulus decreased down to about 25 percent of the dry state modulus E' and kept constant for further conditioning. As expected a Tg reduction for "wet" samples was visible. Additional the time dependence increased proportional to the square root of conditioning time. The high filled adhesive showed much lower diffusion constants at room temperature and the modulus change was not that remarkable. For 85°C/85% r.h conditioning the modulus decrease to about 40% of the initial room temperature value

In this study, two highly filled molding compounds were used as example to demonstrate the characterization scheme. In addition, two low filled packaging polymers are included for comparison. The characterization scheme consists of the steps sample preparation, measurement of the material data, and modeling the material behavior. The dasiasample preparationpsila step included a DSC analysis to understand the cure reaction and to establish the cure kinetics model. In the dasiameasurementpsila step, two different sets of equipment were applied. The elongation modulus is determined by dynamic mechanical analysis (equipment: DMA dasiaQ800psila) in a wide range of temperatures and frequencies. The other parameters are measured by pressure-volume-temperature experiments (equipment: PVT dasiaGnomixpsila). Conducting these characterization tests, the bulk modulus (K), coefficient of thermal expansion (CTE), and the cure shrinkage was determined. The paper describes this comprehensive characterization with the measurement setups and parameter selection. E(T,t), K(T,t), CTE(T), Tg and cure shrinkage are determined to define a complete and consistent material model [JAN07]. Subsequently, the characterization results are presented, discussed and further work to implement the complete material model into FEM simulation tools like ANSYStrade is outlined

Structural Health Monitoring (SHM) is a wide spread field for material condition observation of differential structure components. At the IZFP the guided wave (Lamb wave) technology is under higher investigation. Actual investigations are in progress to apply SHM-systems at structures in airplanes to perform condition monitoring. New materials like Carbon Fibre Reinforced Plastics (CFRP) will be placed in airplanes partially, because they provide very high stiffness, high rupture strength and reduced total mass. These SHM-systems are using different damage indicators, which are based on differences in amplitude or phase relation between two measured signals at two different times points (condition). Additionally, these signals are affected by environmental loads, sensor setup and changes in material properties of the adhesive layer. A successful material application can only be achieved by using an integrated reliable SHM-system. The validation of reliability comes along with high probability of detection and high robustness regarding environmental loads. This study tests and analyses the robustness of a novel piezo-sensor-package. The sensor package is very slim and consists of LTCC ceramic, which encloses a PZT piezo ceramic sheet and carries electronic components on its surface. Using the piezoelectric effect the package generates lamb waves and transmits them into a base substrate. The package is assembled on a 2 mm (thick) aluminium plate for study purposes, because aluminium possesses an isotropic material behaviour. Frequency ranges from 25 kHz up to 400 kHz produce excited symmetrical S0 and asymmetrical A0 lamb waves that are guided into the aluminium plate. Subsequently, a FEM-model of the package is calibrated to ensure correct physical behaviour of the simulation using analytical solutions of lamb wave propagation and experimental data. The calibration of the FEM-model provides the base for further investigations. The principle of wave propagation based - - on the new package configuration is studied and effects resulting from the package shape and construction are defined. Also, influences of the adhesive layer between the ceramic package and the aluminium plate are determined as a function of thickness and temperature depended stiffness and for the case of a delaminating progress

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