Nondestructive detection of intermetallics in solder joints by high energy X-ray diffraction

Abstract

X-ray diffraction permits direct and unequivocal identification of crystallographic phases, although conventional low-energy beams penetrate to a depth of only several micrometers. A high-energy X-ray beam (up to 320 keV) easily penetrates through a circuit board and the attached devices, permitting the identification of any intermetallic layers in the interior. Because the diffraction intensity is proportional to the concentration, this method might also assess the relative concentration of the intermetallics and thus develop some estimate of their effect on the package reliability. However, the combination of conventional X-ray diffraction concepts with a high-energy beam has not been utilized to a full extent yet, and so merits further investigation. We have demonstrated the concept on some simple specimens that we prepared in our laboratory. Through the presentation of this report, we hope to contact other researchers who are studying fracture through these intermetallics. We would like to evaluate our testbed system on a range of actual industrial intermetallic specimens over the next few years.