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 role of alloying elements in improving the corrosion resistance of amorphous iron base alloys
Abstract X-ray photo-electron spectroscopy has been used to investigate the correlation between the compositions of a surface film and the underlying alloy and the beneficial effects of alloying elements. The addition of alloying elements less noble than iron increases the corrosion resistance in the active region by improving the protective quality of the corrosion product film in which the cations of alloying elements are significantly concentrated. Even if the passivity of alloying elements is not stable in the passive region of alloys, the alloying asists the formation of passive hydrated iron oxy-hydroxide film by decreasing the dissolution rate of alloys prior to the passive film formation. The improvement of corrosion resistance by alloying with the elements more noble than iron has been interpreted in terms of the decrease in the anodic activity of alloys.