Solders

• US 20030007886A1
• Filed: 08/17/2001
• Published: 01/09/2003
• Est. Priority Date: 07/09/2001
• Status: Active Grant

• Current Assignee: Quantum Chemical Technologies (Singapore) Pte., Ltd., Singapore Asahi Chemical & Solder Ind. Pte., Ltd.
• Original Assignee: Quantum Chemical Technologies (Singapore) Pte., Ltd.
• Inventors: Hwa, Chew Kai, Wei, Chih Pan
• Granted Patent: US 6,843,862 B2
• Time in Patent Office: Days
• US Class Current: 420/560
• CPC Class Codes: B23K 35/262 Sn as the principal constituent

Abstract

A substantially lead-free solder with enhanced properties comprises from 88.5% to 93.5% tin; from 3.5% to 4.5% silver; from 2.0% to 6.0% indium; and from 0.3% to 1.0% copper. The solder may also comprise up to 0.5% of an anti-oxidant or anti-skinning additive. A solder embodying the invention finds particular utility in wave-soldering processes where it may be used as a direct replacement for conventional tin/lead solder.

Claims

1. A substantially lead-free solder comprising:

from 88.5% to 93.2% tin;

from 3.5% to 4.5% silver;

from 2.0% to 6% indium; and

from 0.3% to 1% copper.

2. A solder according to claim 1 which comprises up to 0.5% of an anti-oxidant or anti-skinning additive.

3. A solder according to claim 2 wherein the additive is phosphorous or another non-metallic compound or element.

4. A solder according to claim 1 which comprises 91.3% tin, 4.2% silver, 4.0% indium and 0.5% copper.

5. A solder according to claim 1 which comprises 91.39% tin, 4.1% silver, 4.0% indium, 0.5% copper and 0.01% phosphorous.

6. A method of preparing a substantially lead-free solder, comprising the step of mixing tin, silver, indium and copper such that:

the proportion of tin in the solder is from 88.5% to 93.2%;

the proportion of silver in the solder is from 3.5% to 4.5%;

the proportion of indium in the solder is from 2.0% to 6%; and

the proportion of copper in the solder is from 0.3% to 1.0%.

7. A method according to claim 6 comprising including up to 0.5% of an anti-oxidant or anti-skinning additive in the solder mixture.

8. A method according to claim 7 wherein the additive is phosphorous or another non-metallic compound or element.

9. A method according to claim 6 which comprises mixing tin, silver, indium, and copper such that:

the proportion of tin in the solder is 91.3%;

the proportion of silver in the solder is 4.2%;

the proportion of indium in the solder is 4%; and

the proportion of copper in the solder is 0.5%.

10. A method according to claim 6 which comprises mixing tin, silver, indium, copper and phosphorous such that:

the proportion of tin in the solder is 91.39%;

the proportion of silver in the solder is 4.31%;

the proportion of indium in the solder is 4%;

the proportion of copper in the solder is 0.5%; and

the proportion of phosphorous in the solder is 0.01%.

11. A method of soldering, comprising the step of using a substantially lead-free solder comprising:

from 88.5% to 93.5% tin;

from 3.5% to 4.5% silver;

from 2.0% to 6.0% indium; and

from 0.3% to 1.0% copper.

12. A method according to claim 11 which comprises using a solder having up to 0.5% of an anti-oxidant or anti-skinning additive.

13. A method according to claim 12, wherein the additive is phosphorous or another non-metallic element or compound.

14. A method according to claim 11 which comprises using a solder comprising 91.3% tin, 4.2% silver, 4.0% indium and 0.5% copper.

15. A method according to claim 11 which comprises using a solder comprising 91.39% tin, 4.1% silver, 4.0% indium, 0.5% copper and 0.01% phosphorous.

16. A method according to claim 11 which comprises the step of wave-soldering using the substantially lead-free solder.