Tin whisker problem looms over aerospace and defense

Budget cuts at industry OEMs and a “ho hum” attitude at the Department of Defense (DoD) may allow tin whiskers to form in electronics systems, according to a Lockheed Martin engineer and at retired DoD engineer. According to the Lockheed Martin engineer, budget cuts at OEMs are preventing full consideration of potential system failures due to tin whisker growth on RoHS compliant parts. “Managers are concentrating on the problems in the present and not looking to the future,” said the engineer. “Right now managers are dealing with budget cuts. They’re looking to save dollars now, while not seeing that a few dollars spent now will save thousands, millions, perhaps billions of dollars later.”

The problem that is getting ignored, according to the engineer, is the potential formation of tin whiskers in aerospace, defense and medical equipment. Tin whiskers – which form easily on pure tin solder and finishes – can break off and short out a component. Although aerospace and defense are mostly exempt from the RoHS directive, commercial parts that are becoming RoHS-compliant will find their way into these systems as component suppliers retire their leaded parts. The engineer believes potential system failures can be avoided if managers commit to testing to make sure components are free from potential tin whisker growth. “If the managers allowed a few dollars in expenditures now so components can be vetted, it could save heartache later.”

A retired DoD engineer – who also spoke anonymously – says the DoD is failing to take precautions against tin whisker growth in lead-free components. “DoD under the U.S. Defense Advanced Research Projects Agency (DARPA) should be addressing the tin whisker mitigation and lead-free solder issue,” says the engineer. “But I have not heard of any DARPA program that addresses this issue. High level managers in both industry and at the DoD choose to bury their heads in the sand and hope somebody else will address the issue.”

The engineer’s concern is that lead-free components will soon be only parts available in some component groups as the components industry moves to RoHS-compliant parts. Industry groups such as International Electronics Manufacturing Initiative (iNEMI) have called for parts suppliers to continue making high-reliability non-compliant parts for the aerospace, defense and medical industries. iNEMI formed the High-Reliability RoHS Task Force for this purpose.

The retired DoD engineer believes the DoD should also take a role in making sure RoHS compliant parts that use pure tin for solder and finishes– pure tin comes with a high risk of tin whisker formation – don’t find their way into systems that are destined to be used in high-stress environments. “What are the DoD and its contractors going to do when the only available finish left is pure tin? How are they going to defend our country when the military systems are at jeopardy because a tin whisker can bring down a system?”