SMTA International Conference Proceedings


Authors: David Geiger, Todd Castello, Dr. Dongkai Shangguan
Company: Flextronics
Date Published: 9/26/2004   Conference: SMTA International

Abstract: Many aspects of printed circuit board assembly using leadfree solders have been investigated. The aspect to be presented in this paper will be the inspection of the solder joints of area array packages using 2D and 3D X-ray systems. The challenges of X-ray inspection for lead-free solder joints will be discussed in comparison with tin-lead assemblies.

There is some speculation that inspection of hidden solder joints may be impacted by the use of lead-free solders. The reason for this speculation is the absence of lead from the solder alloy thereby decreasing the density of the solder. The density of 63Sn/37Pb solder is around 8.41g/cc and the density of Sn/Ag/Cu lead-free alloy is around 7.39g/cc. This is about a 12% difference in the densities.

The question is how a 12% difference in the density affects the X-ray inspection of the hidden solder joints.

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