Effects of Lead-Free Solders on Imaging Characteristics of the HP 5DX Laminographic X-ray Inspection System

As concerns of the environmental impact of lead waste increase, the electronics industry is coming under increasing pressure to reduce or eliminate the use of lead in their manufacturing processes. Circuit assembly providers consequently must develop alternatives to eutectic tin-lead solder for use in their operations. Many ramifications are likely, including an initial decrease in process yield, modifications to process equipment, higher material cost, and an increased need for process control information. The HP 5DX laminographic x-ray inspection system is currently used both to find structural defects in solder joints after reflow and also to provide statistical process control information. However, since the existing HP 5DX is predominantly designed for use with eutectic tin-lead solder compounds, customers purchasing the machine have a valid concern regarding its ability to inspect solder joints constructed with lead-free solders. In this paper we provide a theoretical comparison of x-ray attenuation for various solder compounds. Such a comparison indicates the relative effects of lead-free solders on imaging characteristics in the HP 5DX. To help visualize our theoretical indications, we additionally show both actual and simulated images of joints made with lead-free solder compounds.