Method for electrically interconnecting large contact arrays using eutectic alloy bumping

A method of forming electrical interconnects comprising:

• forming an array of first bumps and an array of second bumps on a first substrate, wherein said first bumps comprise a first material and said second bumps comprise a second material which is different than the first material;
• forming an array of third bumps and an array of fourth bumps on a second substrate, said array of third bumps corresponding to said array of first bumps and comprising a third material, wherein said first material and said third material form a eutectic composition having a eutectic temperature;
• aligning said array of first bumps with said array of third bumps and said array of second bumps with said array of fourth bumps;
• contacting said array of first bumps with said array of third bumps at a contact temperature above the eutectic temperature, said array of first and third bumps forming a plurality of joined bumps that electrically interconnect said first and second substrates;
• and
• contacting said second bumps with said fourth bumps to provide structural support between said first substrate and said second substrate and provide a common electrical connection.

A method of forming electrical interconnects comprising:

• forming a plurality of first bumps of a first material having a first melting temperature on a first substrate;
• forming a plurality of second bumps of a second material having a second melting temperature on a second substrate, wherein said first material and said second material form a composition having a eutectic temperature and each of said first bumps has a first volume and each of said second bumps has a second volume;
• forming a plurality of third bumps of a third material on said first substrate, wherein said third material is different than the first material;
• forming a plurality of fourth bumps of a fourth material on said second substrate;
• aligning said first and second plurality of bumps;
• and
• contacting said first and second plurality of bumps at a contact temperature above the eutectic temperature and below the lowest of the first and second melting temperatures to form a plurality of first joined bumps that electrically interconnect said first and second substrates, wherein a ratio of said first volume to said second volume results in first joined bumps having a mostly solid phase at said contact temperature and aligning said first and second plurality of bumps aligns said third and fourth plurality of bumps and contacting said first and second set of bumps causes contact between said third and fourth plurality of bumps to form a plurality of second joined bumps which electrically interconnects said first and second substrates.