Semiconductor device solder bump having intrinsic potential for forming an extended eutectic region and method for making and using the same

A method for performing direct chip attach comprising the steps of:

• providing a semiconductor device having a first metal layer overlying a bonding pad to provide adhesion for subsequent metal layers to the semiconductor device, a second metal layer overlying the first metal layer, and a solder bump comprising a first tin layer overlying the second metal layer, wherein the first tin layer and the second metal layer are mutually soluble such that an intermetallic of the second metal layer and the first tin layer may be formed, a lead layer overlying the first tin layer, wherein the lead layer is thicker than the first tin layer, and a second tin layer overlying the lead layer, wherein the second tin layer is thinner than the lead layer to provide localized eutectic formation at a top surface of the solder bump during solder reflow;
• positioning the semiconductor device with the solder bump overlying and facing a conductive trace on a mounting substrate;
• aligning the solder bump and the conductive trace such that the solder bump is approximately centered over the conductive trace;
• bringing the solder bump into physical contact with the conductive trace;
• and
• heating the solder bump to a temperature approximately in a range of 183.degree. C. to less than 250.degree. C., wherein a eutectic liquidus solder composed of the second tin layer and a portion of the lead layer is formed at a surface of the solder bump,
• wherein the eutectic liquidus solder wets to the conductive trace to join the semiconductor device to the mounting substrate.