LEAD-FREE AND ANTIMONY-FREE TIN SOLDER RELIABLE AT HIGH TEMPERATURES
A lead-free, antimony-free tin solder which is reliable at high temperatures and comprises from 3.5 to 4.5 wt.% of silver, 2.5 to 4 wt.% of bismuth, 0.3 to 0.8 wt.% of copper, 0.03 to 1 wt.% nickel, 0.005 to 1 wt.% germanium, and a balance of tin, together with any unavoidable impurities.
1 . A lead-free, antimony-free solder alloy comprising:
(a) 3 to 5 wt% of silver
(b) 2.5 to 5 wt% of bismuth
(c) 0.3 to 2 wt% of copper
(d) at least one of the following elements
up to 1 wt.% of nickel
up to 1 wt.% of titanium
up to 1 wt.% of cobalt
up to 3.5 wt.% of indium
up to 1 wt.% of zinc
up to 1 wt.% of arsenic
(e) optionally one or more of the following elements
0 to 1 wt.% of manganese
0 to 1 wt. % of chromium
0 to 1 wt.% of germanium
0 to 1 wt.% of iron
0 to 1 wt.% of aluminum
0 to 1 wt.% of phosphorus
0 to 1 wt.% of gold
0 to 1 wt.% of gallium
0 to 1 wt.% of tellurium
0 to 1 wt.% of selenium
0 to 1 wt.% of calcium
0 to 1 wt.% of vanadium
0 to 1 wt.% of molybdenum
0 to 1 wt.% of platinum
0 to 1 wt.% of magnesium
0 to 1 wt.% of rare earths
(f) the balance tin, together with any unavoidable impurities;
wherein the alloy affirmatively contains said Ni in a concentration of 0.01 to 1 wt%; and
wherein the alloy affirmatively contains said Ge in a concentration of 0.005 to 1 wt%.
2 . The solder alloy according to claim 1 , wherein the alloy comprises:
from 3.5 to 4.5 wt.% of silver;
from 2.5 to 4 wt.% of bismuth;
from 0.3 to 0.8 wt.% of copper;
from 0.03 to 1 wt.% nickel;
from 0.005 to 1 wt.% germanium,
the balance tin, together with any unavoidable impurities.
3 . The solder alloy according to claim 2 , wherein the alloy comprises from 2.8 to 4 wt% bismuth.
4 . The solder alloy according to claim 2 , wherein the alloy comprises from 0.6 to 0.8 wt% copper.
5 . The solder alloy according to claim 2 , wherein the alloy comprises from 0.03 to 0.6 wt.% nickel.
6 . The solder alloy according to claim 2 , wherein the solder alloy consists essentially of:
from 3.5 to 4.5 wt.% of silver;
from 2.8 to 4 wt.% bismuth;
from 0.4 to 0.7 wt.% copper:
from 0.1 to 0.3 wt.% nickel: and
from 0.005 to 0.01 wt.% germanium,
the balance tin, together with any unavoidable impurities.
7 . The solder alloy as claimed in claim 2 , wherein the alloy has melting point of from 195 to 222° C.
8 . The solder alloy as claimed in claim 2 in the form of a bar, a stick, a solid or flux cored wire, a foil or strip, or a powder or paste (powder plus flux blend), or solder spheres for use in ball grid array joints or chip scale packages, or other pre-formed solder pieces, with or without a flux core or a flux coating.
9 . A soldered joint comprising an alloy as defined in claim 2 .
10 . A method of forming a solder joint comprising:
(i) providing two or more work pieces to be joined;
(ii) providing a solder alloy as defined in claim 2 ; and
(iii) heating the solder alloy in the vicinity of the work pieces to be joined.
11 . The solder alloy as claimed in claim 2 , wherein the solder alloy comprises from 0.005 to 1 wt% of a rare earth metal.
12 . The solder alloy as claimed in claims 11 , wherein the rare earth metal is cerium.
13 . A lead-free, antimony-free solder alloy comprising:
(a) 3 to 5 wt% of silver;
(b) 2.5 to 5 wt% of bismuth;
(c) 0.3 to 2 wt% of copper;
(d) 0.03 to 1 wt.% nickel; and
(e) 0.005 to 1 wt% of a rare earth metal;
the balance tin, together with any unavoidable impurities.
14 . The solder alloy as claimed in claim 13 , where the rare earth metal is cerium.
15 . The solder alloy as claimed in claim 13 , wherein the alloy contains germanium in a concentration of 0.005 to 1 wt%.
16 . A lead-free, antimony-free solder alloy comprising:
(a) 3.5 to 5 wt% of silver;
(b) 2 to 5 wt% of bismuth;
(c) 0.3 to 2 wt% of copper;
(d) 0.03 to 1 wt.% nickel; and
(e) at least one of 0.01 to 0.2 wt% cerium, 0.01 to 0.08 wt% lanthanum, or 0.01 to 0.08 wt% neodymium;
the balance tin, together with any unavoidable impurities.
17 . The solder alloy as claimed in claim 16 , wherein the alloy contains germanium in a concentration of 0.005 to 1 wt%.
18 . A lead-free, antimony-free solder alloy comprising:
(a) 3.5 to 5 wt% of silver;
(b) 2 to 5 wt% of bismuth;
(c) 0.3 to 2 wt% of copper; and
(d) 0.01 to 3.5 wt.% indium; and
the balance tin, together with any unavoidable impurities.
19 . The solder alloy as claimed in claim 18 , wherein the alloy contains nickel in a concentration of 0.03 to 1 wt.%.
20 . The solder alloy as claimed in claim 19 , wherein the alloy contains germanium in a concentration of 0.005 to 1 wt%.