The interfacial reactions of Sn–Zn based solders and a Sn–Ag–Cu solder have been compared with a eutectic Sn–Pb solder. During reflow
soldering different types of intermetallic compounds (IMCs) are found at the interface. The morphologies of these IMCs are quite different for
different solder compositions. As-reflowed, the growth rates of IMCs in the Sn–Zn based solder are higher than in the Sn–Ag–Cu and Sn–Pb
solders. Different types of IMCs such as -Cu5Zn8, -CuZn and a thin unknown Cu–Zn layer are formed in the Sn–Zn based solder but in the
cases of Cu/Sn–Pb and Cu/Sn–Ag–Cu solder systems Cu6Sn5 IMC layers are formed at the interface. Cu6Sn5 and Cu3Sn interfacial IMCs are
formed in the early stages of 10 min reflow due to the limited supply of Sn from the Sn–Pb solder. The spalling of Cu–Sn IMCs is observed
only in the Sn–Ag–Cu solder. The size of Zn platelets is increased with an increase of reflow time for the Cu/Sn–Zn solder system. In the case
of the Sn–Zn–Bi solder, there is no significant increase in the Zn-rich phases with extended reflow time. Also, Bi offers significant effects on
the wetting, the growth rate of IMCs as well as on the size and distribution of Zn-rich phases in the -Sn matrix. No Cu–Sn IMCs are found in
the Sn–Zn based solder during 20 min reflow. The consumption of Cu by the solders are ranked as Sn–Zn–Bi > Sn–Ag–Cu > Sn–Zn > Sn–Pb.
Despite the higher Cu-consumption rate, Bi-containing solder may be a promising candidate for a lead-free solder in modern electronic
packaging taking into account its lower soldering temperature and material costs.
The interfacial reactions of Sn–Zn based solders and a Sn–Ag–Cu solder have been compared with a eutectic Sn–Pb solder. During reflowsoldering different types of intermetallic compounds (IMCs) are found at the interface. The morphologies of these IMCs are quite different fordifferent solder compositions. As-reflowed, the growth rates of IMCs in the Sn–Zn based solder are higher than in the Sn–Ag–Cu and Sn–Pbsolders. Different types of IMCs such as -Cu5Zn8, -CuZn and a thin unknown Cu–Zn layer are formed in the Sn–Zn based solder but in thecases of Cu/Sn–Pb and Cu/Sn–Ag–Cu solder systems Cu6Sn5 IMC layers are formed at the interface. Cu6Sn5 and Cu3Sn interfacial IMCs areformed in the early stages of 10 min reflow due to the limited supply of Sn from the Sn–Pb solder. The spalling of Cu–Sn IMCs is observedonly in the Sn–Ag–Cu solder. The size of Zn platelets is increased with an increase of reflow time for the Cu/Sn–Zn solder system. In the caseof the Sn–Zn–Bi solder, there is no significant increase in the Zn-rich phases with extended reflow time. Also, Bi offers significant effects onthe wetting, the growth rate of IMCs as well as on the size and distribution of Zn-rich phases in the -Sn matrix. No Cu–Sn IMCs are found inthe Sn–Zn based solder during 20 min reflow. The consumption of Cu by the solders are ranked as Sn–Zn–Bi > Sn–Ag–Cu > Sn–Zn > Sn–Pb.Despite the higher Cu-consumption rate, Bi-containing solder may be a promising candidate for a lead-free solder in modern electronicpackaging taking into account its lower soldering temperature and material costs.
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