Lead-free soldering method and soldered article

Patent metadata

Field	Value
Publication number	US-2017012018-A1
Application number	US-201615276156-A
Country	US
Kind code	A1
Filing date	Sep 26, 2016
Priority date	Oct 17, 2014
Publication date	Jan 12, 2017
Grant date	—

Abstract

In a soldering method for Ag-containing lead-free solders to be soldered to an Ag-containing member, void generation is prevented and solder wettability is improved. The soldering method for Ag-containing lead-free solders of the present invention is a soldering method for Ag-containing lead-free solders includes a first step of bringing a lead-free solder having a composition that contains Ag that a relation between a concentration C (mass %) of Ag contained in an Sn—Ag-based lead-free solder before soldering of a mass M(g) and an elution amount B(g) of Ag contained in the Ag-containing member becomes 1.0 mass %≦(M×C+B)×100/(M+B)≦4.6 mass % and that the balance consists of Sn and unavoidable impurities into contact with the Ag-containing member, a second step of heating and melting the lead-free solder, and a third step of cooling the lead-free solder.

First claim

1 . A soldering method for Ag-containing lead-free solders to be soldered to an Ag-containing member comprising:
a first step of bringing a lead-free solder into contact with the Ag-containing member, the lead-free solder having a composition consisting of Ag and the balance of Sn and unavoidable impurities, which satisfies a relation between a concentration C (mass %) of Ag contained in an Sn—Ag based lead-free solder before soldering of a mass M(g) and an elution amount B(g) of Ag contained in the Ag-containing member being as follows:
1.0 mass %≦(M×C+B)×100/(M+B)≦4.6 mass %

a second step of heating and melting the lead-free solder; and a third step of cooling the lead-free solder.

2 . The soldering method for Ag-containing lead-free solders according to claim 1 , wherein
the composition of the lead-free solder in the first step is configured by a multiple eutectic system that a precipitation strengthening element that is not more than 0.1 mass % in solubility limit concentration has been added to a Sn—Ag eutectic system, and the lead-free solder in the third step has a composition that a total mass of Ag shifted from the Ag-containing member to the lead-free solder, Ag contained in the lead-free solder and the precipitation strengthening element is at least 1.0 mass % and not more than 4.6 mass % relative to the mass of the lead-free solder in the third step and the balance consists of Sn and the unavoidable impurities.

3 . The soldering method for Ag-containing lead-free solders according to claim 2 , wherein
the precipitation strengthening element is at least one or more kinds of elements selected from a group consisting of Cu, Ni, Fe, Cr, Co, Zn, Pt and Ti.

4 . The soldering method for Ag-containing lead-free solders according to claim 1 , wherein
the composition of the lead-free solder in the first step is configured by a multiple eutectic system that Sb is contained in the Sn—Ag eutectic system, and a composition of the lead-free solder in the third step is consisting Sb of not more than 9.5 mass % not including of 0 and the balance consisting of Sn and the unavoidable impurities.

5 . The soldering method for Ag-containing lead-free solders according to claim 4 , wherein
Ag concentration is 2.5 mass % to 3.9 mass %, and Sb concentration is at least 6.2 mass % and not more than 9.5 mass % relative to the mass of the lead-free solder after melted and brought into contact with the Ag-containing member.

6 . The soldering method for Ag-containing lead-free solders according to claim 1 , wherein
the lead-free solder in the third step is made such that a total mass of Ag shifted from the Ag-containing member to the lead-free solder and Ag contained in the lead-free solder is at least 2.5 mass % and not more than 3.9 mass % relative to the mass of the lead-free solder in the third step.

7 . The soldering method for Ag-containing lead-fee solders according to claim 1 , wherein
a thickness of the Ag-containing member before soldering is at least 0.2 μm and not more than 2 μm.

8 . A soldered article comprising:
a semiconductor chip; an Ag-containing electrode arranged on a surface of the semiconductor chip as the Ag-containing member; and an Ag-containing lead-free solder soldered by the soldering method for Ag-containing lead-free solders according to claim 1 .

9 . The soldered article according to claim 8 , comprising
an insulating circuit substrate equipped with a wiring circuit pattern, wherein the semiconductor chip is made such that a control electrode and a high potential side electrode are arranged on one surface and a low potential side Ag-containing electrode to be soldered to the wiring circuit pattern of the insulating circuit substrate with the Ag-containing lead-free solder is arranged on the other surface.

Assignees

• Fuji Electric Co Ltd

Inventors

• Watanabe Hirohiko
• Saito Shunsuke
• Ono Masahiro
• Watanabe Takashi
• Sano Shinji
• Onishi Kazunaga

Classifications

• H10W72/884

  Die-attach connectors and bond wires · CPC title

• H10W72/865

  Die-attach connectors and bond wires · CPC title

• H10W72/547

  Dispositions of multiple bond wires · CPC title

• H10W72/07554

  changes in dispositions · CPC title

• H10W90/756

  between a chip and a stacked lead frame, conducting package substrate or heat sink · CPC title