Lead free solders are being increasingly used in the electronic industry. While most of the electronic products, in terms of volume, are already built lead free, sectors of the industry including high end servers, networking and telecommunications are covered by “lead in solder” exemptions. It is unknown at this point how long these exemptions will last. In addition, many components such as memories have started appearing only in the Pb-free version. As a result, the industry has been pushed to either adopt a mixed assembly process or to transition early to a full Pb-free process. Even though numerous papers have outlined the successful implementation of a Pb-free process, few of them have actually looked at complex high-end multilayer boards in its entirety. This paper focuses on the issues involved in developing an acceptable Pb-free process window for thick, multilayer boards for SMT, Wave soldering, Rework and Press-fit operations. A laminate capable of withstanding Pb-free soldering temperatures was used to construct a 125-mil thick multilayer board with 18 layers which included 8 ground and 10 signal planes. This experiment utilized two popular Pb-free finishes commonly used in the industry: Immersion Silver and high temperature Organic Solderability Preservative (OSP). The widespread SAC 305 alloy with a composition of Sn3.0Ag0.5Cu was used for both SMT and wave soldering. Three sets of assemblies were built: Pb-free, Mixed and Sn/Pb. The mixed assembly mostly used Pb-free components with Sn/Pb solder paste. The impact of increased soldering temperatures on the board, components and reliability of the product were also studied as a part of this research endeavor. Board level reliability tests were conducted by subjecting the boards from 0°C to 100°C Air-to-Air thermal cycling as well as mechanical shock and vibration tests. A suite of reliability and destructive physical analysis (DPA) tests were carried out to establish the quality of the soldering using the eutectic Sn/Pb assembly as the baseline. The study compared the cycling performance of the three sets of assemblies and also looked at the potential impacts of moving to mixed assemblies. Results indicated a reduced process window for Pb-free, especially for the Pb-free wave soldering process due to reduced wetting of the plated through hole barrels as compared to Sn/Pb wave soldering process. The thermal cycling performance of the three sets of assemblies was found to be equivalent after 6000 cycles.
Skip Nav Destination
ASME 2007 InterPACK Conference collocated with the ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference
July 8–12, 2007
Vancouver, British Columbia, Canada
Conference Sponsors:
- Electronic and Photonic Packaging Division
ISBN:
0-7918-4277-0
PROCEEDINGS PAPER
Pb-Free Process Development for a High End Storage Area Network Application Available to Purchase
Manthos Economou
Manthos Economou
Palm, Inc., Sunnyvale, CA
Search for other works by this author on:
Sunil Gopakumar
Brocade, San Jose, CA
Francois Billaut
Brocade, San Jose, CA
Eric Fremd
Brocade, San Jose, CA
Manthos Economou
Palm, Inc., Sunnyvale, CA
Paper No:
IPACK2007-33857, pp. 937-943; 7 pages
Published Online:
January 8, 2010
Citation
Gopakumar, S, Billaut, F, Fremd, E, & Economou, M. "Pb-Free Process Development for a High End Storage Area Network Application." Proceedings of the ASME 2007 InterPACK Conference collocated with the ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference. ASME 2007 InterPACK Conference, Volume 1. Vancouver, British Columbia, Canada. July 8–12, 2007. pp. 937-943. ASME. https://doi.org/10.1115/IPACK2007-33857
Download citation file:
10
Views
Related Proceedings Papers
Related Articles
Numerical Modeling of the Wave Soldering Process and Experimental Validation
J. Electron. Packag (March,2022)
Isothermal Cyclic Bend Fatigue Test Method for Lead-Free Solder Joints
J. Electron. Packag (December,2007)
Environment-Friendly Electronics: Lead-Free Technology
J. Electron. Packag (December,2005)
Related Chapters
Reliability of Electronic Packaging
Essentials of Electronic Packaging: A Multidisciplinary Approach
Section III: Subsections NC and ND — Class 2 and 3 Components
Companion Guide to the ASME Boiler and Pressure Vessel Code, Volume 1, Fourth Edition
Performance Evaluation of an IP-SAN Initiator Based on Multi-Core Network Processors
International Conference on Computer Technology and Development, 3rd (ICCTD 2011)