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.

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.

INTRODUCTIONCorrosion reliability recently becomes an issue due to the trend of miniaturization of electronic products. The phenomenon of electronic corrosion is ionic migration which is also known as electrochemical migration (ECM) by surplus moisture remained inside the package. High temperature may also deteriorate the ECM failure. The hydrated metal ions (positively charged) will migrate towards the cathode and form a dendrite. In this paper, electrochemical migration failure caused by hygro-thermal swelling and residual moisture has been carefully investigated for FR-4 PCB board plated with Cu. An analytical moisture diffusion solution is proposed to determine the moisture distribution and consequent hygroscopic induced strain as well as stress. By applying Fickian diffusion law, the "thermal wetness" analogous technique is used to solve moisture absorption and desorption models. The analytical expression for total expansion strain due to hygro-thermo-vapor pressure coupled effect is implemented using finite element software ANSYS. Finite element predictions reveal the significance of contribution of hygroswelling induced effective stress/strain. Hygroscopic properties such as moisture diffusivity and coefficient of moisture expansion are characterized by an integrated TMA/TGA scheme. Solubility and vapor pressure effect are included to study popcorn failure during reflow process.

Moisture properties such as moisture diffusivity and hygroscopic swelling have been carefully investigated for polymeric materials used on the MEMS-based pressure sensor. An improved TMA/TGA integrated method is used to characterize the hygroscopic swelling property. An analytical moisture diffusion solution is proposed to determine the moisture distribution and consequent hygroscopic induced strain as well as stress. By applying Fick's second law of diffusion, the "thermal wetness" analogous technique is applied to solve moisture absorption/desorption models. The analytical expression for total expansion strain due to hygro-thermo-mechanical coupled effect is implemented using finite element software ANSYS. Finite element predictions reveal the significance of contribution of hygroswelling induced effective stress/strain. Reliability analysis and hygro-thermo-mechanical design for a MEMS-based pressure sensor are performed in accordance with JEDEC preconditioning standard JESD22-A120. A series of comprehensive experimental works and parametric studies were conducted in this paper.