it will be understood that it is not necessary that elevated temperature 812 be held constant e g in the illustrated embodiment an elevated temperature may be varied from above the melting point temperature of the initial eutectic au u2014 sn solder layer composition up to the melting point temperature of pure au for example it may be desirable to increase the temperature to accelerate the solidification process or to decrease the temperature to slow the solidification process following solidification the solderable layer and contacting solder layer may be optionally held at the same elevated temperature 812 e g of from about m p 1 u00b0 c to about m p 30 u00b0 c for an additional period of time suitable to allow additional au atoms to continue to transfer to and migrate within the solidified bonding material further increasing the au content of the bonding material by diffusion to greater than about 90 au and less than about 10 sn as represented by point 808 of fig8 e g from about 15 minutes to about 60 minutes or for any other suitable period of time during this time the au concentration may also be allowed to homogenize within the layer of bonding material as illustrated in fig8 the au content of the solidified bonding material and homogenized phase 808 is higher than in the original solder composition 802 e g of solder layer 206 of fig7 and therefore the melting point 810 of this solidified bonding material phase is higher than that of the original solder composition 802 for example a further increase in au content to about 91 by weight increases the melting point of the now solidified bonding material to a final melting.