# US 10,442,037 B2 · Pb-free Sn—Ag—Cu—Al or Sn—Cu—Al solder

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- Number: US 10,442,037 B2
- Document ID: US10442037B2
- Status: Granted
- Kind: B2
- Application number: 14/544,833
- Filed: 2015-02-24
- Published: 2015-08-20
- Granted: 2019-10-15
- Earliest claimed: 2010-04-23
- Assignees: Iowa State University Research Foundation, Inc.
- Applicants: Iowa State University Research Foundation, Inc.
- Inventors: Iver E. Anderson; Joel L. Harringa; Adam J. Boesenberg
- Web page: https://patentgrep.com/patent/US10442037B2

## CPC

- B23K 35/262: {Sn as the principal constituent}
- B23K 35/001: {Interlayers, transition pieces for metallurgical bonding of workpieces}
- B23K 35/0244: {Powders, particles or spheres; Preforms made therefrom}
- C22C 13/00: Alloys based on tin
- H05K 3/346: Solder materials or compositions specially adapted therefor
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS

## Abstract

A solder alloy includes Sn, optional Ag, Cu, and Al wherein the alloy composition is controlled to provide a strong, impact-and thermal aging-resistant solder joint that has beneficial microstructural features and is substantially devoid of Ag3Sn blades.

## Claims

### Claim 1

A solder alloy that is solidified on an electrically conductive substrate comprising copper, said solder alloy consisting essentially of 0.95 to about 3.5 weight % Cu, from 0.15 to about 0.25 weight % Al, and balance consisting essentially of Sn, wherein the Al promotes nucleation of pro-eutectic Cu6Sn5 within the solder alloy which pro-eutectic Cu6Sn5 provides additional interface area for Sn nucleation, said solder alloy providing reduced undercooling that is less an 8 degrees C. upon solder solidification on the electrically conductive substrate as compared to a solder alloy free of Al.

### Claim 2

A solder alloy that is solidified on an electrically conductive substrate comprising copper, said solder alloy consisting essentially of about 0.95 to about 3.05 weight % Cu, 0.15 to about 0.25 weight Al, and balance consisting essentially of Sn, wherein the Al promotes nucleation of pro-eutectic Cu6Sn5 within the solder alloy which nucleation, said solder alloy providing reduced undercooling that is less then 8 degrees C. upon solder solidification on the electrically conductive substrate as compared to a solder alloy free of Al.

### Claim 3

A solder alloy consisting essentially of 0.95 to about 3.5 weight % Cu, from 0.20 to about 0.25 weight % Al, and balance consisting essentially of Sn, said solder alloy providing reduced undercooling upon solder solidification on an electrically conductive substrate comprising copper as compared to the solder alloy free of Al, wherein said reduced undercooling is less than 8 degrees C. upon solder solidification.