Direct solder bumping of hard to solder substrate

Claim 2

A process for applying solder bumps to a hard to solder substrate, comprising the steps of: melting a modified solder composition comprising a solder base alloy modified by alloying with a light reactive metal in an amount effective to wet and bond to a hard to solder pad surface, selected from the group consisting of aluminum, and aluminum alloy, and indium tin oxide, to make a solder interconnect on a microelectronic part; heating the surface of the pad; creating and maintaining an inert gas atmosphere over the pad; producing a microdrop of the modified solder composition within the inert gas atmosphere; applying the microdrop to the heated surface of the pad while maintaining the inert gas atmosphere; and freezing the microdrop in electrical and mechanical contact with the surface of the pad.

Claim 3

The process of claim 1 wherein the base of the modified solder composition primarily comprises tin and lead.

Claim 4

The process of claim 2 wherein the base is modified with a light reactive metal consisting primarily of lithium.

Claim 5

The process of claim 1 wherein the solder base comprises at least two metals selected from the group consisting of Pb, Sn, In, Bi, Cd, Sb, Hg, Ga, Ag and Au.

Claim 6

The process of claim 4 wherein the light reactive metal is selected from the group consisting of Li, Na, K, Rb, Cs, Ca and Mg.

Claim 7

The process of claim 1 wherein the base of the modified solder composition primarily comprises tin and indium.

Claim 8

The process of claim 6 wherein the base is modified with a light reactive metal consisting primarily of lithium.

Claim 9

The process of claim 1 wherein the solder base comprises at least two metals selected from the group consisting of Pb, Sn, In, Bi, Cd, Sb, Hg, Ga, Ag and Au.

Claim 10

The process of claim 8 wherein the light reactive metal is selected from the group consisting of Li, Na, K, Rb, Cs, Ca and Mg.

Claim 11

A process for making solder interconnects directly on the surface of hard to solder microelectronic substrates, comprising the steps of: melting a modified solder composition comprising a solder base modified by alloying with a light reactive metal in an amount effective to make a solder interconnect on a substrate pad for a microelectronic part selected from the group consisting of aluminum, aluminum alloys, and indium tin oxide; providing a solder jetting device having a printhead in fluid communication with the melted modified solder composition; placing the printhead near the surface of the substrate which has not been altered to accept a conventional solder whereby the printhead is spaced a working distance from the surface of the substrate and creates a gap effective for printing liquid solder droplets on the surface; elevating the temperature of the substrate above ambient temperature and providing a shroud of inert gas in the gap created between the substrate and the printhead; emitting droplets of the modified solder composition from the printhead within said gap; depositing one of said droplets directly onto said surface of the hard to solder substrate while it is at said elevated temperature and shrouded by the inert gas within said gap whereby said one solder droplet wets, adheres to the surface and solidifies thereby providing a solder interconnect directly on the substrate.

Claim 12

A process for making solder interconnects directly on the surface of hard to solder microelectronic substrates, comprising the steps of: melting a modified solder composition comprising a solder base modified by alloying with a light reactive metal in an amount effective to make a solder interconnect on a substrate pad for a microelectronic part selected from the group consisting of aluminum, aluminum alloys, and indium tin oxide; providing a solder jetting device having a printhead in fluid communication with the melted modified solder composition; placing the printhead near the surface of the substrate which has not been altered to accept a conventional solder whereby the printhead is spaced a working distance from the surface of the substrate and creates a gap effective for printing liquid solder droplets on the surface; elevating the temperature of the substrate above ambient temperature and providing a shroud of inert gas in the gap created between the substrate and the printhead; emitting droplets of the modified solder composition from the printhead within said gap; depositing one of said droplets directly onto said surface of the hard to solder substrate while it is at said elevated temperature and shrouded by the inert gas within said gap whereby said one solder droplet wets, adheres to the surface and solidifies thereby providing a solder interconnect directly on the substrate.

Claim 13

The process of claim 10 wherein the base of the modified solder composition primarily comprises tin and lead.

Claim 14

The process of claim 11 wherein the base is modified with a light reactive metal consisting primarily of lithium.

Claim 15

The process of claim 10 wherein the solder base comprises at least two metals selected from the group consisting of Pb, Sn, In, Bi, Cd, Sb, Hg, Ga, Ag and Au.

Claim 16

The process of claim 13 wherein the light reactive metal is selected from the group consisting of Li, Na, K, Rb, Cs, Ca and Mg.

Claim 17

The process of claim 10 wherein the base of the modified solder composition primarily comprises tin and indium.

Claim 18

The process of claim 15 wherein the base is modified with a light reactive metal consisting primarily of lithium.

Claim 19

The process of claim 10 wherein the solder base comprises at least two metals selected from the group consisting of Pb, Sn, In, Bi, Cd, Sb, Hg, Ga, Ag and Au.

Claim 20

The process of claim 17 wherein the light reactive metal is selected from the group consisting of Li, Na, K, Rb, Cs, Ca and Mg.