Investigation of the thickness of lubricant film on gold plated surface

Abstract

Lubricants for electrical contacts are usually diluted to low concentrations in order to keep boundary lubrication between contacts after solvent is volatilized. Evidence shows that the thickness and coverage of lubricants play an important role in reducing wear, preventing corrosion and blocking pores on the gold plating surface of electrical contacts. The distribution of lubricant film usually is observed by putting colorful dyes into lubricant. Average film thickness can be estimated by the weight of lubricant on the sample divided by surface area. Two new methods are introduced in this paper to measure the coverage and film thickness on a surface with much higher accuracy: (1) backscattering electron (BSE) method-by changing acceleration voltage of the scanning electron microscope (SEM) at low ratings, the film distribution can be shown visually by the BSE image; (2) three dimensional profiler (3D profiler) method-by insertion of the optical parameters of the lubricants, film thickness can be measured with accuracy. This paper illustrates and compares the advantages and disadvantages of the above four methods.