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In this paper, the characteristics of polymeric packaging materials for Pre-mold QFN type CMOS Image Sensor (CIS) have been carefully investigated. Hygro-mechanical property, the coefficient of moisture expansion (CME) for different materials was measured through Thermal Mechanical Analysis (TMA) and Thermal Gravitational analysis (TGA) at given humidity and temperature. Moisture absorption/desorption diffusivity were determined under Arrhenius behavior. The transient moisture diffusion analysis described by Fick's equation is performed to evaluate the overall moisture distribution. In accordance with the JEDEC pre-conditioning standard JESD22-A120, reliability and thermal design were carried out due to mismatch of the coefficient of thermal expansion (CTE) and CME for multi-material package of CIS. A threedimensional solid model of CIS based on finite element ANSYS software is developed to predict the thermal-induced strain, hygroscopic swelling deformation and the residual thermo-hygro-mechanical stress distributions. A series of comprehensive parametric studies were conducted in this research.

scarcity of characterization approach and lack of hygroscopic swelling material property. Engineers are also inexperienced in The objective of this paper is focused on the hygroscopic swelling moisture diffusion and hygroscopic swelling modeling. However, effect on polymeric material used in electronic package and thermo-these difficulties can be overcome and will be fully explored in this hygro-structure coupled design and reliability analysis for finger paper. printer package. For moisture absorption/desorption analysis, the ambient environment for temperature and humidity are set to be Polymeric materials transport moisture primary by diffusion, 60°C60%RH, 85OC60%RH and 85OC85%RH, respectively. The which can be analogically modeled in standard Fick's transient transient moisture diffusion analysis described by Fick's equation is diffusion equation. In moisture diffusion model, field variable (local performed to evaluate the overall moisture distribution. Hygroscopic moisture concentration) is discontinuous across different material swelling properties such as coefficient of saturation (Csat), boundaries when it exposed to the same temperature-humidity coefficient of moisture expansion (p) and activation energy (Q) can condition [3][4]. This can be resolved by using temperature-wetness be extracted through TMA (Thermal Mechanical Analysis) and TGA technique for modeling multi-material interfacial moisture diffusion. (Thermal Gravitational Analysis). A three-dimensional solid model The same wetness technique is also applied to model moisture of finger printer package based on finite element ANSYS software is desorption during dry baking and IR reflow process. Aside moisture, developed to predict the thermal-induced strain, hygroscopic temperature loading is another important factor for reliability of swelling and the residual stress distributions. The predicted thermal-plastic IC packages. In order to conduct the integrated thermoinduced displacements were found to be very good agreement with hygro-mechanical analysis the hygroscopic strain is treated as an the Moire interferometer experimental in-plane deformation. The additional term adding to the thermal strain. The particular stress developed finite element 3D model, therefore, is applied to predict pattern and overall stress distribution at stressed region represent the the mechanism of thermo-hygro-mechanical induced stress in potential failure site. The proposed moisture diffusion model is accordance with JEDEC pre-condition standard JESD22-A120. An designated to evaluate the overall moisture distribution and the local analytical expression for the total expansion strain due to thermo-moisture concentration at the critical interfaces. hygro-mechanical coupled effect was proposed and the implementation procedures using software ANSYS were described in From practical view, manufacturing process needs moisture details. A series of comprehensive parametric studies were absorption/desorption data for entire package rather than bulk conducted in this paper.

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In the present paper, a comprehensive moisture diffusion model and characterization for encapsulated plastic Flip Chip (FC) Ball Grid Array (BGA) package are investigated. The transient moisture diffusion analysis described by Fick's second law is performed to evaluate the overall moisture distribution. Diffusivities in the moisture desorption model are determined under Arrhenius behaviors. Hygroscopic swelling properties of polymeric materials are characterized by using an existing TMA/TGA extraction method. With the so-called -thermal-wetness‖ analogous technique, finite element analysis (FEA) is developed to evaluate the entire moisture distribution on FC BGA package. The analytical expression for total expansion strain due to hygro-thermomechanical coupled effect is implemented using finite element software ANSYS. Finite element predictions reveal the significance of contribution of hygroswelling induced strain. Reliability analysis for FC BGA is performed in accordance with JEDEC standard JESD22-A120. A series of comprehensive experimental works and parametric studies are conducted in this research.

The modified Reynolds equation for power-law fluid is derived from the viscous adsorption theory for thin film elastohydrodynamic lubrication (TFEHL) of circular contacts. The lubricating film between solid surfaces is modeled as three fixed layers, which are two adsorption layers on each surface and a middle layer. The differences between classical EHL and TFEHL with power-law lubricants are discussed. Results show that the TFEHL power law model can reasonably calculate the pressure distribution, the film thickness, and the velocity distribution. The thickness and viscosity of the adsorption layer and the flow index significantly influence the lubrication characteristics of the contact conjunction.

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