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Characterizing Thermal Fatigue Reliability of Third Generation PB-Free Alloys



Characterizing Thermal Fatigue Reliability of Third Generation PB-Free Alloys
The progress of an experimental program for evaluating thermal fatigue performance of third generation alternative Pbfree solder alloys is discussed.
Analysis Lab

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Authored By:


Richard Coyle
Nokia Bell Labs, Murray Hill, NJ, USA

Richard Parker
iNEMI, Tipton, IN, USA

Keith Howell, Keith Sweatman
Nihon Superior Co., Ltd., Osaka, Japan

Dave Hillman
Rockwell Collins, IA, USA

Joe Smetana
Nokia, Plano, TX USA

Glen Thomas, Hongwen Zhang
Indium Corp., Utica, NY,USA

Stuart Longgood, Andre Kleyner
Delphi, Kokomo, IN, USA

Michael Osterman
CALCE, College Park, MD, USA

Eric Lundeen
i3 Electronics, Endicott, NY, USA

Polina Snugovsky
Celestica, Inc., Toronto, ON, Canada

Julie Silk
Keysight Technologies, Santa Rosa, CA, USA

Rafael Padilla, Tomoyasu Yoshikawa
Senju Metal Industry Co., Tokyo, Japan

Jasbir Bath
Bath & Associates Consultancy, Fremont, CA, USA

Mitch Holtzer
Alpha Assembly Solutions, South Plainfield, NJ, USA

Jerome Noiray, Frederic Duondel
Sagem, Paris, France

Raiyo Aspandiar
Intel Corporation, Hillsboro, OR, USA

Jim Wilcox
Universal Instruments Corporation, Conklin, NY, USA

Summary


Development of the first generation of current commercial Pb-free solder alloys was based on, high Ag content, neareutectic Sn-Ag-Cu (SAC) compositions. Subsequently, second generation, lower Ag alloys were developed to address the shortcomings of near-eutectic SAC, particularly poor mechanical shock performance. The development of third generation Pb-free solder alloys is proceeding along two prominent paths. In one case, high-Ag content alloys are being modified with various major alloying additions to improve thermal fatigue performance in aggressive use environments and increase resistance to damage from high strain rate mechanical loading. In the other case, alloys with Ag content lower than SAC305 are being developed to address needs for better drop/shock resistance, lower processing (melting) temperature, and lower cost.

This paper describes the planning and progress of an experimental program for evaluating the thermal fatigue performance of a number of third generation alternative Pbfree solder alloys. The program is being developed and executed through a collaboration of several major industrial consortia that includes membership from high reliability end users, solder suppliers, and electronic contract manufacturers.

Conclusions


The status of critical project items at the time of this writing is as follows:

The solder ball attachment has been completed on all of the components required to populate the thermal cycling and baseline test matrix.

The stencil printing process and surface mount reflow profile were developed using SAC305 components and solder paste during a pilot build conducted at Rockwell Collins. Multiple stencils have been ordered to facilitate the assembly of the complete test matrix.

All but one of the solder pastes have been delivered to Rockwell Collins and are in refrigerated storage.

The surface mount assembly of the test boards is anticipated to begin in early September 2016 depending on the delivery of the complete sets of components and solder pastes to Rockwell Collins.

Thermal cycling will be performed at four participant sites: CALCE (-40/125 Celsius), i3 (-40/150 Celsius), Nokia Bell Labs (0/100 Celsius), and Rockwell Collins (-55/125 Celsius).

Initially Published in the SMTA Proceedings

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