Lead-free solder alloy and lead-free solder paste using the same

• US 20030230361A1
• Filed: 06/16/2003
• Published: 12/18/2003
• Est. Priority Date: 06/17/2002
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Takahashi, Kuniaki
• Granted Patent: US 6,884,389 B2
• Time in Patent Office: Days
• US Class Current: 148/24
• CPC Class Codes: B23K 35/264 Bi as the principal constituent
• CPC Class Codes: C22C 13/02 with antimony or bismuth as the next major constituent

Abstract

Disclosed is a lead-free solder alloy containing 43 to 47% by weight of bismuth, 0.5 to 2.5% by weight of silver, 0.25 to 0.75% by weight of copper, 0.25 to 0.75% by weight of indium, 0.02 to 0.09% by weight of nickel and the balance of tin.

Claims

1. A lead-free solder alloy containing 43 to 47% by weight of bismuth, 0.5 to 2.5% by weight of silver, 0.25 to 0.75% by weight of copper, 0.25 to 0.75% by weight of indium, 0.02 to 0.09% by weight of nickel and the balance of tin.

2. A lead-free solder alloy according to claim 1, wherein the bismuth content falls within a range of between 44.5% by weight and 45.5% by weight, the silver content falls within a range of between 0.9% by weight and 2.2% by weight, the copper content falls within a range of between 0.4% by weight and 0.6% by weight, the indium content falls within a range of between 0.4% by weight and 0.6% by weight, and the nickel content falls within a range of between 0.05% by weight and 0.09% by weight.

3. A lead-free solder alloy according to claim 1, further containing antimony in an amount not larger than 0.5% by weight and germanium in an amount not larger than 0.5% by weight.

4. A lead-free solder paste comprising a lead-free solder alloy containing 43 to 47% by weight of bismuth, 0.5 to 2.5% by weight of silver, 0.25 to 0.75% by weight of copper, 0.25 to 0.75% by weight of indium, 0.02 to 0.09% by weight of nickel and the balance of tin, and a flux.

5. A lead-free solder paste according to claim 4, wherein the bismuth content of the lead-free solder alloy falls within a range of between 44.5% by weight and 45.5% by weight, the silver content of the lead-free solder alloy falls within a range of between 0.9% by weight and 2.2% by weight, the copper content of the lead-free solder alloy falls within a range of between 0.4% by weight and 0.6% by weight, the indium content of the lead-free solder alloy falls within a range of between 0.4% by weight and 0.6% by weight, and the nickel content of the lead-free solder alloy falls within a range of between 0.05% by weight and 0.09% by weight.

6. A lead-free solder paste according to claim 5, further containing antimony in an amount not larger than 0.5% by weight and germanium in an amount not larger than 0.5% by weight.