X-ray Inspection
By Robert Meller
VJ Electronix Inc.
234 Taylor Street
Littleton, MA 01460
tel:978-486-4777
fax:978-486-4550

How does lead-free solder impact X-ray images?

In the beginning, it was feared by some that X-ray would become impracticable with lead-free solder. Most customers knew this to be untrue. The metals used to replace the lead in solder pastes, like silver, copper, zinc, and bismuth, provide absorption rates to create solder joints with good contrast to justify X-ray inspection as the inspection tool, not just for hidden solder joints. X-ray inspection is the most efficient technology to reveal voiding and wetting problems in the soldering process on the production floor.

More concerns arose about the long-term integrity of solder joints in lead-free products being more susceptible to thermal cycling. Cracks can occur after a reasonable low number of thermal cycles. Materials, even the base material, are not yet fully characterized as to the effects of the increased thermal stress due to the higher solder temperatures. It will be interesting to see how manufacturers of components and materials can solve these issues.