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.
Determination of the static and dynamic mechanical properties of FeCrSiB metallic glass wire
Abstract The static and dynamic mechanical properties of metallic glass wires of compositions Fe 85− x−y Cr x Si y B 15 ( x = 0−8, y = 7.5) or 10) have been investigated. A modified design of bending fatigue machine was employed for the dynamic tests. The static strength of the as-cast metallic glass wire ( σ f = 3000−3800 MPa and H v = 900−1080) increased relatively slowly on substitution of Fe by up to 10 at.% Cr. The fatigue strength was, however, strongly dependent on Cr content. This indicated that Cr substitution for Fe was effective in enhancing the fatigue strength of FeSiB at lower concentration than has previously been reported. X-ray photoelectron spectroscopy observations suggest that the Cr-induced fatigue strength enhancement is due mainly to the presence of an oxide film rich in Si and Cr (oxides) on the surface of the wire.
The influence of transition metal substitutions on the formation, stability and hardness of some Fe- and Ni-based metallic glasses
Abstract Iron- and nickel-based glassy alloys containing a wide variety of transition metal alloying additions have been prepared by melt-spinning and their thermal stability and glass-forming ability have been assessed. It is shown that the variation of the crystallization temperature (taken as an estimate of the glass-transition temperature and hence the thermal stability) with alloying additions is primarily a function of both the average outer-electron concentration of the transition elements in the alloy and the atomic size difference between solvent and solute metal species. The microhardness of the alloys is shown to be related to the outer-electron concentration in a similar way to thermal stability, but the effect of atomic size difference on microhardness is less pronounced. Within limited composition ranges the glass-forming ability of the materials is enhanced by alloying.