Rapidly solidifying Pb-free Sn-Ag-Cu-Al or Sn-Cu-Al solder

Patent metadata

Field	Value
Publication number	US-10625378-B2
Application number	US-201413999284-A
Country	US
Kind code	B2
Filing date	Feb 6, 2014
Priority date	Apr 23, 2010
Publication date	Apr 21, 2020
Grant date	Apr 21, 2020

Abstract

A solder alloy includes Sn, optional Ag, Cu, and Al wherein the solder alloy composition together with the solder alloy superheat temperature and rapid cooling rate from the superheat temperature are controlled to provide a dispersion of fine hard Cu—Al intermetallic particles in an as-solidified solder alloy microstructure wherein the particles are retained even after multiple solder reflow cycles often used in modern electronic assembly procedures to provide a particle strengthening to the solder joint microstructure as well as exert a grain refining effect on the solder joint microstructure, providing a strong, impact- and thermal aging-resistant solder joint that has beneficial microstructural features and is substantially devoid of Ag 3 Sn blades.

First claim

We claim:

1. A solder comprising an alloy comprising aluminum, copper, optionally silver, and tin with copper present in an amount of about 0.7 to about 3.5 weight %, with aluminum present in an amount of 0.10 to 0.25 weight %, with silver optionally present in an amount of about 3 to about 4 weight %, and with the balance of the solder alloy consisting essentially of tin, said solder including, before solder reflow, a dispersion of Cu 33 Al 17 intermetallic particles in a solder alloy matrix whose largest particle dimension, averaged, is about 0.1 micron to about 0.5 micron.

2. The solder of claim 1 in the form of a solder ball before solder reflow.

3. The solder of claim 1 in the form of a solder ribbon or foil before solder reflow.

4. The solder of claim 1 wherein the alloy consists essentially of about 3 to about 4 weight % Ag, about 0.7 to about 1.7 weight % Cu, and about 0.10 to about 0.25 weight % Al, and balance consisting essentially of Sn.

5. The solder of claim 1 wherein the alloy also intentionally comprises about 3 to about 4 weight % Ag.

6. A solder comprising a Sn—Cu—Al alloy consisting essentially of about 3.2 minus y weight % Cu, y weight % Al, and balance consisting essentially of Sn wherein y is about 0.15 to about 0.25 weight %, said solder including, before solder reflow, a dispersion of Cu 33 Al 17 intermetallic particles in a solder alloy matrix whose largest particle dimension, averaged, is about 0.1 micron to about 0.5 micron.

Assignees

• Univ Iowa State Res Found Inc

Inventors

• Anderson Iver E
• Reeve Kathlene Nicole

Classifications

• B23K35/286

  Al as the principal constituent · CPC title

• B23K35/025

  Pastes, creams or slurries · CPC title

• B23K35/38

  Selection of media, e.g. special atmospheres for surrounding the working area · CPC title

• B23K35/383

  mainly containing noble gases or nitrogen · CPC title

• B23K35/302

  Cu as the principal constituent · CPC title