There are dozen of different alloys but here is what I know would be best guess:
Alloy Selection Team: Press Releases
NEMI Group Recommends Tin/Silver/Copper Alloy as Industry Standard for Lead-Free Solder Reflow in Board Assemblies
Less Expensive Tin/Copper Alloy Recommended for Wave Solder Applications
Herndon, Va. — January 24, 2000 — The National Electronics Manufacturing Initiative (NEMI) today announced the alloy its Lead-Free Assembly Project is recommending for use by industry as a “standardized” lead-free solder alternative.
For reflow applications (which represent at least 70% of all board assembly production), the NEMI group is recommending use of Sn3.9Ag0.6Cu — a predominantly tin-rich alloy with 3.9% silver and 0.6% copper. For wave solder production (which requires larger amounts of solder), the group is recommending Sn0.7Cu, a less expensive tin/copper alloy (0.7% copper), or — as an alternative — Sn3.5Ag (tin with 3.5% silver).
Based on findings of its 1998 roadmap, NEMI organized an industry task force in early 1999 to investigate process and material considerations of lead-free electronics assemblies (see addendum for list of task force participants). The task force investigated past efforts and developed a program plan to address lead-free electronics manufacturing solutions. The first step of this plan, which is being implemented by NEMI’s Lead-Free Assembly Project, was to evaluate, select and recommend a single lead-free solder alloy to pursue as an industry standard.
“Task force participants felt strongly that it would be of significant benefit to industry to focus on one standard alloy for replacing lead in solder,” says Jim McElroy, executive director and CEO of NEMI. “By cooperatively developing a single solution, the industry can implement a replacement sooner, avoid multiple manufacturing processes and, by concentrating on one alloy, enhance basic understanding of the material and assure its reliability.”
The Lead-Free Assembly Project found no drop-in replacement for tin/lead solder. The group compiled a worldwide patent database of candidate alloys and collected all available material properties. In addition to information compiled or generated by the group, data was obtained from two industry reports: the final report of the NCMS Pb-Free Solder Project, a $10.3M in-kind program performed in the US between 1993 and 1997 (http://www.ncms.org/3portfolio/1ProjectPortfolio/pubs.htm), and a report on lead-free soldering from the U.K. Department of Trade and Industry (http://www.dti.gov.uk).
Based on thorough analysis of the data collected, the most promising solutions for the types of high-reliability products made by the majority of North American electronics manufacturers were combinations of tin, copper and/or silver. After consideration of the data on available alloys, the particular combination of Sn3.9Ag0.6Cu was chosen as it could be readily supplied by four different solder manufacturers.
“The NEMI Lead Free Assembly Project is solving a critical industry wide problem,” according to Dr. David Lando, chairman of the NEMI Board of Directors and Engineering & Environmental Technologies Vice President for Lucent Technologies. “The project is providing solutions that can be readily implemented, are cost effective, and are available in the marketplace. We will seek cooperation with groups in other regions of the world in order to help ensure that these solutions become routinely deployed on a worldwide basis.”
Use of the recommended alloys will raise the melting point by as much as forty degrees, which obviously has an impact on a number of the materials and steps in the assembly process, and affects companies throughout the supply chain. The NEMI Lead-Free Assembly Project is also working to identify the impacts that eliminating lead will have on the manufacturing infrastructure and will work closely with component, board and equipment manufacturers to provide a smooth transition of manufacturing processes for member companies wishing to implement lead-free solders (see addendum for further details).
About NEMI
The National Electronics Manufacturing Initiative was formed in November 1994 to facilitate long-term North American leadership in electronics. The industry-led consortium is made up of over 50 electronics equipment manufacturers, suppliers, associations, government agencies and universities. NEMI’s members represent a combined total of more than $200 billion in revenues (1998) and employ more than 1.25 million people.
NEMI roadmaps the needs of the North American electronics industry, identifies gaps in the technology infrastructure, establishes implementation projects to eliminate these gaps, and stimulates standards activities to speed the introduction of new technologies. The consortium also works with government, universities, and other funding agencies to set priorities for future industry needs and R&D initiatives.
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ADDENDUM — NEMI’s Lead-Free Assembly Project
The NEMI Lead-Free Assembly Project was formed in 1999 to help North American companies develop the capability to produce lead-free products by 2001, with an eye toward total lead elimination by 2004 (with timing of actual deployment left to the participating companies). Activities are focused on the following objectives:
to select an alloy to be used as a “standardized” lead-free solder alternative
to demonstrate production-ready parts, materials and processes for lead-free printed wiring board (PWB) assemblies
to cooperate with component, board and equipment manufacturers to allow for the smooth transition to manufacturing processes requiring temperatures up to 260°C
to develop criteria for the industry to evaluate lead-free processes
to modify or develop appropriate JEDEC, IPC or other related standards for lead-free electronics manufacturing
Project work is organized into four sub-groups. The Solder/Alloy Selection sub-group made the alloy recommendation. The Solder Reliability group’s task is to identify holes in the lead-free data in the public domain and work with other organizations — such as the High Density Packaging User’s Group (HDPUG) and the Integrated Electronics Engineering Center (IEEC) at Binghamton University — to recommend tests and lend support where needed. The Components sub-group will rank cost-effective lead-free component/PWB terminations (based on compatibility with the recommended lead-free solder system), and work with component/PWB manufacturers (through ITRI) to facilitate manufacture of high temperature rated components and PWBs. This group will also work with JEDEC, IPC and other related standards bodies to adapt standards to reflect processing parameters associated with use of lead-free solder and high temperature rated components/PWBs, and provide components and PWBs to assess reliability. Finally, the Environmental Legislation group will monitor and report on legislative initiatives throughout the world.
Organization of the NEMI Lead-Free Assembly Project and definition of the group’s activities are based on the recommendations of an industry-wide task force comprised of the following organizations:
3Com Corporation
AIM Solder
Alpha Metals
Celestica International, Inc.
ChipPAC Incorporated
Compaq Computer Corporation
Connor Winfield Corporation
Cookson Electronics
CTS Corporation
Delphi Delco Electronics Systems
Eastman Kodak
Electronic Industries Alliance (EIA)
HADCO
Heraeus Cermalloy
IBM Corporation
IEEC, SUNY-Binghamton
Indium Corporation of America
Intel Corporation
Interconnection Technology Research Institute (ITRI)
IPC
Johnson Manufacturing Company
KEMET Electronics Corporation
Litton Kester Solder
Lucent Technologies
Metallic Resources Inc.
Motorola Inc.
Multicore Solder
National Center for Manufacturing Sciences (NCMS)
National Institute of Standards and Technology (NIST)
Newbridge Networks Corporation
Nortel Networks
Philips Components
Plexus Electronic Assembly Co.
Praxair, Inc.
Raytheon Systems Company
Rogers Corporation, Circuit Materials Division
Shipley Ronal
Solectron Corporation
Storage Technology Corporation
Texas Instruments
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Project information:
Ron Gedney
NEMI
703-834-2084
rgedney@nemi.org
Press information:
Cynthia Williams
Edelman/GTT
207-871-1260
cwilliams@mindspring.com
nemi.org |
