STRUCTURE AND METHOD TO GAIN SUBSTANTIAL RELIABILITY IMPROVEMENTS IN LEAD-FREE BGAs ASSEMBLED WITH LEAD-BEARING SOLDERS

An assembly having an interconnect structure comprising:

• a first substrate;
• a second substrate;
• and
• a homogenous hybrid interconnect structure joining said first and second substrates, said homogenous hybrid interconnect structure comprising a hybrid solder joint composed of a homogenous mixture of a lead free solder and a lead-containing solder to form a homogenous hybrid solder joint, whereby said homogenous hybrid solder joint has improved, reliable levels of thermo-mechanical fatigue.

An assembly having an interconnection grid array comprising:

• a first substrate;
• a second substrate;
• and
• a homogenous hybrid interconnect grid array joining said first and second substrates, said homogenous hybrid interconnect grid array having a plurality of hybrid solder joints each composed of a homogenous mixture of a lead free solder and a lead-containing solder, whereby said homogenous hybrid interconnect grid array has improved, reliable levels of thermo-mechanical fatigue.

An assembly having an interconnection grid array structure comprising:

• a first substrate;
• a second substrate;
• and
• a homogenous hybrid interconnect grid array joining said first and second substrates, said homogenous hybrid interconnect grid array having a plurality of hybrid solder joints being substantially oblate ellipsoid shaped and each composed of a homogenous mixture of a lead free solder and a lead-containing solder to form a homogenous hybrid interconnect grid array having improved, reliable levels of thermo-mechanical fatigue and characterized by having no distinct regions of said lead free solder joint and said lead-containing solder.