Lead-free solder compositions
A solder wire composition may include 85 to 95 weight percent bismuth, and at least 5 weight percent copper. The solder wire composition may have a diameter of less than about 1 millimeter, and an elongation at break of at least 20%.
1. A method of forming a solder wire, the method comprising:
extruding a billet to form a solder wire having a diameter of less than about 1 millimeter;
heat treating the extruded wire at a temperature of between about 93° C. and about 121° C.; and
winding the heat treated extruded wire onto a spool while the extruded wire is above its solidus temperature.
2. The method of claim 1 , wherein the extruded wire is subjected to said heat treating step for at least 10 seconds.
3. The method of claim 1 , wherein the solder wire is wound on the spool within 10 seconds following said heat treating step.
4. The method of claim 1 , wherein in said extruding step, the wire is extruded at a temperature of from about 220° C. to about 250° C.
5. The method of claim 4 , wherein in said extruding step, the wire is extruded at a pressure of from about 12,410 kPa to about 13,445 kPa.
6. The method of claim 1 , wherein the solder wire comprises:
about 85 to 95 weight percent bismuth;
at least 5 weight percent copper.
7. The method of claim 6 , wherein the solder wire consists of bismuth, copper, and about 1 weight percent or less gallium.
8. The method of claim 1 , wherein the solder wire comprises:
about 88 to 92 weight percent bismuth;
about 8 to 12 weight percent copper; and
about 0.001 to 0.1 weight percent gallium.
9. The method of claim 1 , wherein the extruded wire is subjected to said heat treating step for at least 5 seconds and at most 60 seconds.
10. The method of claim 1 , wherein the solder wire has an elongation of at least about 20% as measured according to ASTM E8.
11. The method of claim 1 , wherein the solder wire has an elastic modulus below about 15 GPa.
12. The method of claim 1 , wherein the solder wire has a thermal conductivity greater than 20 W/m−K.
13. The method of claim 1 , wherein the step of winding the heat treated extruded wire onto a spool includes rolling or coiling.
14. The method of claim 1 , wherein the solder wire is lead free and tin free.
15. A method of forming a solder wire, the method comprising:
extruding a billet at a temperature of from 220° C. to 250° C. and a pressure of from 12,410 kPa to 13,445 kPa to form a solder wire having a diameter of less than 1 millimeter;
heat treating the extruded wire at a temperature of between 93° C. and 121° C.; and
winding the heat treated extruded wire onto a spool while the extruded wire is above its solidus temperature; and
wherein the solder wire comprises:
about 85 to 95 weight percent bismuth;
5 weight percent or greater copper.
16. The method of claim 15 , wherein the solder wire comprises:
about 88 to 92 weight percent bismuth;
about 8 to 12 weight percent copper; and
about 0.001 to 0.1 weight percent gallium.
17. The method of claim 15 , wherein the extruded wire is subjected to said heat treating step for at least 5 seconds and at most 60 seconds.
18. The method of claim 15 , wherein the solder wire has an elastic modulus below about 15 GPa.
19. The method of claim 15 , wherein the solder wire has a thermal conductivity greater than 20 W/m−K.
20. A method of forming a solder wire, the method comprising:
extruding a billet at a temperature of from 220° C. to 250° C. and a pressure of from 12,410 kPa to 13,445 kPa to form a solder wire having a diameter of less than 1 millimeter;
heat treating the extruded wire at a temperature of between 93° C. and 121° C.; and
winding the heat treated extruded wire onto a spool while the extruded wire is above its solidus temperature; and
wherein the solder wire consists of:
about 88 to 92 weight percent bismuth;
about 8 to 12 weight percent copper; and
about 0.001 to 0.1 weight percent gallium.