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A Scanning-Probe Technique for Mapping the Hardness of Lead-Free Solders

Published online by Cambridge University Press:  27 February 2014

Jennifer L. Hay ,
Carlos Morillo  and
Julie Silk
Jennifer L. Hay
Affiliation:
Nano-Scale Sciences Division, Agilent Technologies, 105 Meco Lane, Suite 200, Oak Ridge, TN 37830, U.S.A.
Carlos Morillo
Affiliation:
Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD, 20142, U.S.A.
Julie Silk
Affiliation:
Electronics Measurement Group, Agilent Technologies, 1400 Fountaingrove Pkwy, MS 1USF, Santa Rosa, CA, 75403, U.S.A.
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Abstract

A rapid nano-indentation measurement technique is employed to produce surface maps of hardness. Each indentation cycle requires less than three seconds, including surface approach, contact detection, force application, withdrawal, and movement to the next indentation site. Traditional nano-indentation analyses are applied to the force-displacement measurements from each indentation, but information storage and presentation owe much to scanning-probe technology. Consequently, this nano-indentation technique produces three-dimensional images of mechanical properties which are stored and manipulated just like scanned images.

In the present work, we use this technique to map the hardness of a SAC 305 solder joint with gold plating. After extended isothermal aging, the solder joint comprises three constituents: a tin-rich matrix, a bulk intermetallic AuSn4, and an interfacial intermetallic (Cu, Ni, Au)6Sn5. The softest material is the tin-rich matrix, which has a hardness of 0.51±0.07 GPa. The hardness of the bulk intermetallic is 2.12±0.18 GPa. The interfacial intermetallic has extraordinary hardness— greater than 8 GPa. Under uniform plastic strain, the mismatch in hardness between the interfacial intermetallic and surrounding material may increase the local stress intensity factor which drives interfacial fracture.

Keywords

solderingpackagingnano-indentation
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1652: Symposium LL – Advances in Scanning Probe Microscopy , 2014 , mrsf13-1652-ll07-09
Copyright
Copyright © Materials Research Society 2014 

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References

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