Electrical Characterization of Lead-Free Solder Separable Contact Interface

Objectives

Background

Approach

Objectives

1. Determine the contact resistance versus contact force characteristics of Sn3.9Ag0.6Cu, Sn0.7Cu and Sn3.5Ag solder separable contact interfaces.
2. Determine the contact resistance versus contact force characteristics as a function of aging for selectively aged selected lead-free solder alloys.
3. Determine the fretting corrosion behavior of the selected lead-free solder separable contact interfaces. (second year)

Background

Other CALCE projects (C01-01, C01-02 and C01-03) are directed towards characterization of lead-free solders in their role as permanent solder connections. As with tin-lead solders, it is expected that lead-free solders will also be used for mechanical permanent or separable connections. This project is directed towards determining the electrical characteristics of the selected lead-free solders and comparing their behavior to the current tin-lead solders.

It is well known that the limiting factor in the use of tin or tin alloy separable connections is their susceptibility to fretting corrosion. Lead-free solders are expected to show similar susceptibility. The fretting behavior of the selected lead-free solders will be investigated and compared to that of currently used tin and tin alloy systems.

Approach

1. Develop a methodology for preparing lead-free solder samples in a configuration suitable for use with the CALCE contact resistance probe.
2. Determine the contact resistance versus contact force characteristics for the selected solders.
3. Determine an appropriate aging exposure for the selected solders. Exposures to be considered include steam or heat aging and flowing mixed gas.
4. Determine the contact resistance versus contact force characteristics for the aged solders.
5. Compare the performance of the selected lead-free solders to that of currently used solder alloys.
6. Define a fretting corrosion simulation process. Mechanical and thermal driving forces will be considered. (second year)
7. Determine the fretting corrosion behavior of the selected lead-free solders. (second year)
8. Compare the performance of the selected lead-free solders to that of currently used solder alloys. (second year)