Eutectic Metallurgy
High temperature microelectronic packaging relies on a specific gold tin eutectic alloy to establish both mechanical support and a high thermal conductivity path for semiconductor chips. When reflowed at temperatures above its melting point, the au80sn20 die attach forms a rigid joint with high shear strength and resistance to thermal fatigue. This joint is especially useful in power electronics and optoelectronic devices where operating temperatures remain high.
Reflow Profile
Assembly reliability depends on careful control of the reflow temperature profile and the metallurgy of the mating surfaces. If the metallization layer on the silicon die or substrate is too thick, it can dissolve into the molten solder, shifting the composition away from the eutectic point. This shifts the liquidus temperature upward and causes incomplete melting or void formation.
Interfacial Solder
Creep resistance of this eutectic structure prevents premature failures under constant thermal stress. High stress levels at the die corners can initiate microcracks that propagate through the joint if the thermal expansion mismatch between the die and substrate is not matched. The absence of flux or the use of reducing atmospheres during reflow minimizes voiding and ensures uniform heat transfer.
Liquidus Limit
Operating limits of the resulting joint are defined by the eutectic temperature of two hundred and eighty degrees Celsius. Above this threshold the material softens rapidly and loses its structural integrity.
