THERMODYNAMIC ANALYSIS OF ALUMINATE STABILITY IN THE EUTECTIC BONDING OF COPPER WITH ALUMINA

摘要

The interfacial reactions between Cu and Al_2O_3 which occur during the eutectic bonding process have been examined. A thermodynamic analysis of phase equilibria in the Cu-Al-O system shows that a five-phase equilibrium exists among solid copper with oxygen in solution, liquid copper with oxygen in sol- ution, solid CaAlO_2, Al_2O_3 and oxygen gas at the invariant state T = 1348 K, po_2 = 5.6 × 10~(-7) atm (0.055 Pa). The existence of this invariant state has been confirmed experimentally by heating slightly oxi- dized copper disks placed in contact with alumina disks. The experimentally determined invariant state was found to be in good agreement with that calculated. During eutectic bonding the compound CuAlO_2 forms at the interface between copper and the alumina in specimens containing solid copper only at temperatures lower than 1348 ± 3 K.