Evaluation of the elevated temperature creep strength of three lead-free solder alloys in soldered joints

Amendments to the Safe Drinking Water Act mandated that soldered joints used in potable water systems be free of lead. In addition to lead contents, allowable pressures used in potable water systems are directly related to the elevated temperature creep strengths of the soldered joints. The National Institute of Standards and Technology (NIST) and the Copper Development Association (CDA) investigated the stress rupture behavior of lead-free soldered joints at four temperatures and various applied stresses. An extensive statistical analysis involving maximum likelihood techniques was used to generate estimated threshold stresses (below which failure in the soldered joints did not occur) as a function of composition and temperature. The results of that study for three solder alloys are given.