Effect of heat treatment on the electrical resistivity of near-eutectic Sn-Ag-Cu Pb-free solder alloys

摘要

The electrical rsistivity of solder joints prepared from Sn-Ag,Sn-Ag-Cu,and Sn-Ag-Cu-X alloys (where X=Co,Fe,or Bi) was characterized by a four-point probe technique and interpreted in terms of microstructure and composition.The resistivity is also reported of drawn solid wires of these alloys.The solder-joint samples were prepared by hand soldering to copper substrates and were electrically characterized over a temperature range from 293-423 K,covering the anticipated range of elevated-temperature operation for Pb-free solders.Selected joint specimens were measured before and after a 72-h heat treatmentat 423 at 423K.Metallographic inspection of the solder joints was performed to characterize coarsening effects and to determine the degree to which these changes affected electrical conduction.