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IPC's SPVC Determines Best Lead-free Solder
July 5, 2005 |Estimated reading time: 1 minute
BANNOCKBURN, Ill. — The IPC Solder Products Value Council (SPVC) has created a lead-free testing program to aid in the transition to lead-free by researching which solder is the ideal choice. For three years, the SPVC invested an equivalent of one million dollars in volunteer time, equipment and supplies to create "Final Report — Round-robin Testing and Analysis of Lead-free Solder Pastes with Alloys of Tin, Silver and Copper.""The final report of the round-robin testing and analysis of the lead-free alloys is an excellent example of how companies, although fierce competitors in the marketplace, can come together and work for the benefit of the industry," says Roger Savage, Kester's president and the IPC SPVC's chair.
The final report answers two key questions: What alloys will most likely be used as tin/lead solder replacement, and what tests can accurately determine the differences (if any) in the properties of the most likely candidates? The SPVC determined that the majority of potential "standard" replacement alloys are composed of tin, silver and copper (a.k.a. SAC) alloys, and analyzed the three most commonly used lead-free alloys:
96.5/3.0/0.5 tin/silver copper 95.5/3.8/0.7 tin/silver/copper 95.5/4.0/0.5 tin/silver/copperTest methods used in the research included DSC melt analysis; wetting balance; area of spread; visual inspection of solder joints; X-ray analysis of solder joint voids; temperature cycle testing; thermal shock testing and metallurgical analysis.
The data contained in the 50-page final report supports the SPVC's recommendation of 96.5/3.0/0.5 tin/silver/copper (SAC305) as the alloy of choice for lead-free applications. The final report also includes summary findings on the effect of voiding on solder-joint reliability. Although the research project was not designed as a head-to-head comparison of lead-free vs. tin/lead solder, but because tin/lead solder was used as a control, the report does highlight solder-joint performance based on package type.
Also included in the report are 18 appendices as separate files on CD, covering such topics as alloy characterization, down-select data, an assembly-processing parameter summary, test-vehicle description, assembly-process data, void data, metallographic analysis of 500 cycles up to and including 6000 cycles, and results of thermal shock and temperature cycling. An executive summary is available for free download at www.ipc.org. The full final report is available on CD, and costs $99 for IPC members and $199 for non-members. Please click here to purchase the full report.