The transition from lead solder to lead-free alternatives occurred a few years ago, but it is still causing problems. Aircraft suppliers who need to know whether parts have lead or not are getting some help from i-Nalysis, which is marketing a comparatively low-cost portable tester that determines the makeup of solder alloys on chips.
Many aerospace companies have exemptions from Europe’s RoHS regulation, which effectively ended the use of lead in solder in 2006, because lead-free solders still have some long-term durability issues that make their use an issue given the long lifetimes of aircraft and satellites.
However, it is difficult to know if chips have lead. Processing temperatures and times vary widely for different alloys, so running parts through the wrong processes can cause long-term failures even in parts that seem to pass initial tests with flying colors.
Many companies no longer make lead-free parts, given the small volumes left in the market. When they are available, labeling is sometimes no different than lead-free part numbering, so testing is needed to assure the type of solder being used.
"Aerospace manufacturers have exemptions from RoHS, but it’s difficult to get parts that really have lead,” said i-Nalysis President Drew Hession-Kunz. He noted that a range of problems can still arise, even issues that are not as common as they were from 2004 to 2007 when the changeover was a huge concern throughout the electronics industry.
Hession-Kunz said i-Nalysis had a customer with six production lines—one for leaded parts, the others for lead-free parts. Parts were sometimes mismarked, other times they were accidentally used on the wrong production line, so many chips popped off boards a few months later.
Another issue for aircraft owners, especially those in the military, arises when boards fail and new chips are soldered onto boards. Both sides must have the same materials to prevent problems such as tin whiskers, which grow over time, from appearing.
i-Nalysis is addressing this dilemma with a handheld tester that brings the cost of X-ray fluorescence equipment down substantially. “X-ray fluorescence is the most accepted technology. The tests are inexpensive and they don’t damage parts. But equipment has been expensive,” said Hession-Kunz.
The company’s iD-Prime unit will cost less than $10,000, well below the $30,000 price tag for large systems that now sit in many manufacturing facilities and large depots.
A new X-ray technology that uses pyroelectric crystals makes the technology affordable for smaller businesses. In operation, a small X-ray force is transmitted through the unit’s aperture. The rays are absorbed by metals at different rates, so the type of metal is determined by measuring the rays that bounce back. The device holds a library so operators can determine whether they have got, say, a tin-lead solder with a 40-60 ratio.
Test times depend in part on the type of materials being examined. “If it’s a high-lead-content part, the test takes only a couple seconds,” said Hession-Kunz.
Portability will be a benefit for military maintenance teams. “In the military, there’s a lot of rework. They remove and replace chips from the board. It’s a real challenge to figure out which type solder was used on each board,” said Hession-Kunz.
The handheld tester requires no special protection of users. However, he cautioned that units should not be pointed directly at people.