SOLDER ALLOYS
A solder comprising a bismuth matrix, between about 5-24% copper; and about 0.5-36% tin or antimony or zinc; having a solidus temperature of ≧271° C., a reflow temperature of ≦375° C., and at least one intermetallic composition precipitate comprising copper and at least one of tin, antimony and zinc substantially excluding bismuth formed within the solidus phase.
1 . A solder comprising:
between about 5-24% copper;
about 4-25% tin or antimony or zinc; and
at least 50% by weight bismuth;
having a solidus temperature of ≧271° C., a reflow temperature of ≦375° C., and at least one intermetallic composition precipitate comprising copper and at least one of tin, antimony and zinc substantially excluding bismuth formed within the solidus phase.
2 . The solder according to claim 1 , comprising Bi-xCu-8Sn, where x=8-21.
3 . The solder according to claim 1 , comprising 78Bi-14Cu-8Sn.
4 . The solder according to claim 1 , comprising Bi-xCu-10Zn, where x=8-21.
5 . The solder according to claim 1 , comprising 74Bi-16Cu-10Zn.
6 . The solder according to claim 1 , comprising Bi-xSb-10Cu, where x=9-36.
7 . The solder according to claim 1 , comprising 70Bi-20Sb-10Cu.
8 . A ternary bismuth alloy comprising:
at least 50% bismuth;
5-24% copper; and
4-25% tin or antimony or zinc;
having:
a solidus temperature of ≧271° C.;
a liquidus temperature of ≦660° C.; and
copper intermetallic composition nanoparticles having a hardness greater than the bismuth matrix comprising at least one of tin, antimony and zinc formed within the solidus phase, having a thermal conductivity greater than pure bismuth.
9 . The ternary bismuth alloy according to claim 8 , comprising Bi-xCu-8Sn, where x=8-21.
10 . The ternary bismuth alloy according to claim 8 , comprising 78Bi-14Cu-8Sn.
11 . The ternary bismuth alloy according to claim 8 , comprising Bi-xCu-10Zn, where x=8-21.
12 . The ternary bismuth alloy according to claim 8 , comprising 74Bi-16Cu-10Zn.
13 . The ternary bismuth alloy according to claim 8 , comprising Bi-xSb-10Cu, where x=9-36.
14 . The ternary bismuth alloy according to claim 8 , comprising 70Bi-20Sb-10Cu.
15 . A soldering method, comprising:
providing two respective surfaces separated by a gap;
placing a ternary bismuth alloy having a solidus temperature of ≧271° C. within the gap, comprising at least 50% bismuth, 5-24% copper, and 4-25% tin or antimony or zinc, forming at least one intermetallic composition precipitate comprising copper and at least one of tin, antimony and zinc substantially excluding bismuth formed within a solidus phase;
heating the ternary bismuth alloy to a temperature above the solidus temperature, to melt at least a bismuth matrix phase of the ternary bismuth alloy, and wet the respective surfaces with the ternary bismuth alloy; and
reducing the temperature of the ternary bismuth alloy to below the solidus temperature, to solidify the ternary bismuth alloy and thereby join the two metals.
16 . The soldering method according to claim 15 , wherein the at least one intermetallic composition precipitate comprising copper and at least one of tin, antimony and zinc substantially excluding bismuth formed within the solidus phase comprises copper intermetallic composition nanoparticles having a hardness greater than a bismuth matrix surrounding the nanoparticles, and a thermal conductivity greater than pure bismuth.
17 . The soldering method according to claim 15 , wherein the ternary bismuth alloy has a liquidus temperature ≦660° C.
18 . The soldering method according to claim 15 , wherein the ternary bismuth alloy comprises Bi-xCu-8Sn, where x=8-21.
19 . The soldering method according to claim 15 , wherein the ternary bismuth alloy comprises Bi-xCu-10Zn, where x=8-21.
20 . The soldering method according to claim 15 , wherein the ternary bismuth alloy comprises Bi-xSb-10Cu, where x=9-36.