Simulation assisted investigation and improvement of the performance of an electronics assembly subjected to temperature cycling
Numerical simulation techniques are used increasingly in the (re-)design of micro-electronics because of their time and cost saving potentials. The current paper describes the application of such techniques for analysing and improving the thermo-mechanical performance of an electronics assembly. An initial finite element model is implemented and its predictions are compared to measurements. Based on this comparison, the model is further refined by an improved assessment of the input to the model in the form of materials properties: the properties of the moulding compound, failure behaviour of the lead-compound interface and failure behaviour of the lead material itself. Finally an updated model is used to determine directions for improvement of the behaviour of the assembly design.
Fatigue strength of amorphous alloy wires
Revue des caracteristiques fondamentales de la resistance a la fatigue des alliages amorphes a base de fer, cobalt et nickel. Comparaison de la resistance a la fatigue entre les differents alliages. Etude de la difference en resistance de fatigue entre les charges de traction et de flexion. Analyse du mecanisme de l'amorcage et de la propagation des fissures de fatigue. Influence du rapport de contraintes, de la temperature d'essai, de l'etirage a froid, de la relaxation structurale et de l'environnement sur la resistance a la fatigue et la morphologie de rupture
Microstructure and mechanical properties of Fe-Ni-Cr-Al steel wires produced by in-rotating-water spinning method
Nonequilibrium austenite, γ, or duplex austenite + lath martensite,γ+ α′L, phase wires with high strengths and large elongation have been produced in Fe-Ni-Cr-Al-C alloy system by the in-rotating-water spinning method in which a melt stream is ejected into a rotating water layer. These wires have a circular cross section and a white luster, and the wire diameter is in the range of 80 to 180 µm. The γ phase has a grain size as small as about 1 to 4 µm. The yield strength, Σy, tensile fracture strength, ay, and elongation, εp, are about 340 to 655 MPa, 440 to 975 MPa, and 12 to 22 pct for the γ single phase wires and about 465 to 865 MPa, 640 to 1350 MPa, and 2 to 18 pct for the α′L+γ duplex phase wires. A cold drawing causes significant increases in Σy and Σf, and the attained values are about 3200 MPa and 4030 MPa for Fe-8Ni-12.5Cr-2.5Al-3C wire drawn to about 95 pct reduction in area owing to the formation of a strain-induced α′L phase and a remarkable work-hardening ability of γ and α′L phases. On the subsequent low-temperature annealing around 673 K, the Σy and Σf increase further to 4000 MPa and 4240 MPa, respectively, probably because of the enhancement of the interaction between dislocations and interstitial carbon atoms. Around the temperature (≃800 K) where the γ phase decomposes into a stable mixed structure of α + ordered bec compound + M7C3 on annealing, the εp decreases drastically and the fracture surface morphology changes from a dimple pattern to a cleavage pattern. It has been therefore inferred that the high strengths and good ductility of the melt-quenched y and γ + α′L wires are due to the suppression of the phase transformation of y to a mixed structure of γ + ordered bec compound + M7C3 carbide by the melt-quenching technique.