Semiconductor device having solder-free gold bump contacts for stability in repeated temperature cycles

A method for assembling a semiconductor device comprising the steps of:

• providing a semiconductor chip having a plurality of gold studs;
• providing a tape having a first substrate surface and a second substrate surface;
• the first substrate surface having a plurality of first copper contact pads in locations matching the gold studs on the chip;
• each of the plurality of first copper pads covered by a first continuous and conformal first nickel layer having a first thickness, and a first gold layer covering the first nickel layer;
• the second substrate surface having a plurality of second copper contact pads;
• each of the plurality of second copper pads covered by a second continuous and conformal second nickel layer having the first thickness, and a second gold layer covering the second nickel layer;
• attaching the chip to the first substrate surface by the steps of:
• putting the tape to a frame;
• pressing the plurality of gold studs onto the gold covered plurality of first copper contact pads;
• applying ultrasonic energy to create gold-to-gold interdiffusion contact;
• and
• attaching reflow bodies to the second substrate surface by the steps of:
• attaching each of the plurality of second contact pads with a solder body;
• applying thermal energy to reflow the solder body, thereby creating an alloy layer including gold, copper-nickel-tin alloy and a dominant alloy portion comprising (Cu, Ni, Au)6Sn5 intermetallic compound;
• and
• substantially consuming the entire thickness of the nickel layer on the second copper contact pads.