No standard has emerged for lead-free solder

In the shift to lead-free solders, a standard for lead-free solder composition has not yet arrived. Some electronic components are being produced with pure tin, while others include additional metals such as nickel, silver, gold and others. “There are many different metallurgies for solder,” says a Lockheed Martin engineer who spoke on the condition of anonymity. “Problem is, nobody has an all-around tired-and-proven metallurgy for all applications the way PbSn (tin-lead) solder was broadly accepted.”

The engineer expects the industry to eventually settle on standard compositions. “In time, broader usage of lead-free solders will become more application-tested and the where’s and how-to’s will be better understood,” say the engineer. “The issue is complicated by the diversity of lead-free solders. That means that no one composition will be thoroughly tested.”

The engineer notes that each metal that has been added to pure tin to dampen the likelihood of tin whisker formation comes with its own problems. “Silver – with its corrosion and electromigration problems – is no solution for all,” says the engineer. “And gold – with its high costs and embrittlement of other solder types – is also not a solution that fixes all problems.”

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