Vapor-Phase Thermal Conductivity of Binary Mixtures of Cyclopentane and R134a with R365mfc
The thermal conductivity of mixtures of R365mfc (1,1,1,3,3-pentafluorobutane), with R134a (1,1,1,2-tetrafluoroethane) and cyclopentane were measured using a transient hot-wire method, in the pressure range between 0.1013 and 0.7 MPa and temperatures between 311 and 413 K. The composition of the measured mixtures was 93.0% R365mfc + 7.0% R134a (kg/kg), 27.0% R365mfc + 73.0% R134a (kg/kg) and 62.8% R365mfc + 37.2% Cyclopentane (kg/kg). The Wassiljewa mixing rules modified by Mason and Saxena and the Extended Corresponding States Theory were used to correlate and to predict the experimental results obtained, with an average absolute deviation of 1.8 and 10%, respectively.
Thermal conductivity of polyurethane foam cell gases: Improved transient hot wire cell - data of isopentane + n-pentane mixtures - Extended Wassiljewa-model
Abstract The thermal conductivity of pure components and binary mixtures of n -pentane, isopentane and nitrogen was measured at temperatures between 309 and 414 K and at pressures up to 1.0 MPa using an apparatus based on the transient hot wire method. These mixtures are important in the assessment of the progress of the thermal insulation capacity of closed cell polyurethane foams during the total life time of the respective applications. The experimental thermal conductivity data were correlated with the Wassiljewa mixing rules as modified by Mason and Saxena, and predicted using two new empirical models, with average deviations under 0.4% and 0.6%, respectively. Significant changes were performed in the apparatus, with the design of a new measuring cell and the simplification of the tubing system. A new experimental procedure was also developed leading to a considerable improvement in the precision of the results.
“ PARTIALLY-ACTIVATED ” FLUX RESIDUE IMPACTS ON ELECTRONIC ASSEMBLY RELIABILITIES
The reliabilities of the flux residue of electronic assemblies and semiconductor packages are attracting more and more attention with the adoption of no-clean fluxes by majority of the industry. In recent years, the concern of “partiallyactivated” flux residue and their influence on reliability have been significantly raised due to the miniaturization along with high density design trend, selective soldering process adoption, and the expanded use of pallets in wave soldering process. When flux residue becomes trapped under low stand-off devices, pallets or unsoldered areas (e.g. selective process), it may contain unevaporated solvent, “live” activators and metal complex intermediates with different chemical composition and concentration levels depending on the thermal profiles. These partially-activated residues can directly impact the corrosion, surface insulation and electrochemical migration of the final assembly. In this study, a few application tests were developed internally to understand this issue. Two traditional liquid flux and two newly developed fluxes were selected to build up the basic models. The preliminary results also provide a scientific approach to design highly reliable products with the goal to minimize the reliability risk for the complex PCB designs and assembly processes.