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 up to 10 wt % Ag, up to 10 wt % Bi, up to 3 wt % Cu, other optional additives, balance tin, and unavoidable impurities.
1. A lead-free, antimony-free solder alloy consisting of:
(a) 3 to 4.5 wt. % silver;
(b) 2.90 to 3.02 wt. % bismuth;
(c) 0.5 to 1.5 wt. % copper;
(d) 0.05 to 0.25 wt. % nickel;
(e) 0.005 to 0.05 wt. % of titanium; and
(f) the balance tin, together with any unavoidable impurities.
2. The solder alloy according to claim 1 , wherein the alloy comprises from 3.5 to 4.0 wt. % silver.
3. The solder alloy according to claim 1 , wherein the alloy comprises from 0.5 to 0.9 wt. % copper.
4. The solder alloy according to claim 1 , wherein the alloy comprises from 0.008 to 0.05 wt. % titanium.
5. The solder alloy according to claim 1 , wherein the alloy has a melting point of from 195 to 222° C.
6. The solder alloy according to claim 1 in the form of a bar, a stick, a solid or flux cored wire, a foil or strip, or a powder or paste, 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.
7. A soldered joint comprising an alloy as defined in claim 1 .
8. 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 1 ; and
(iii) heating the solder alloy in the vicinity of the work pieces to be joined.
9. A lead-free, antimony-free solder alloy consisting of:
(a) 3.0 to 4.5 wt. % silver;
(b) 3.5 to 5 wt. % bismuth;
(c) 0.3 to 1.2 wt. % copper;
(d) 0.05 to 0.3 wt. % nickel;
(e) 0.01 to 0.6 wt. % cobalt; and
(f) the balance tin, together with any unavoidable impurities.
10. The solder alloy according to claim 9 , wherein the alloy comprises from 0.01 to 0.1 wt. % cobalt.
11. A lead-free, antimony-free solder alloy consisting of:
(a) 3.0 to 4.5 wt. % silver;
(b) 2.90 to 3.02 wt. % bismuth;
(c) 0.3 to 1.2 wt. % copper;
(d) 0.05 to 0.25 wt. % nickel;
(e) 0.001 to 1.0 wt. % manganese; and
(f) the balance tin, together with any unavoidable impurities.
12. The solder alloy according to claim 11 , wherein the alloy comprises from 0.005 to 0.01 wt. % manganese.
13. The solder alloy according to claim 1 , wherein the alloy exhibits a coefficient of thermal expansion of about 23.8 μm/mK.
14. The solder alloy according to claim 1 , wherein the alloy exhibits a Vickers Hardness of from about 28 to about 30.
15. The solder alloy according to claim 1 , wherein the alloy is exposed to a heat treatment step at approximately 150° C. for about 200 hours.
16. The solder alloy according to claim 9 , wherein the alloy comprises 3.5 to 4.0 wt. % silver.