Influence of Multiple Reflows and Surface Finishes on Solder Joint Resistivity

Abstract

The main purpose of this paper is the analysis of the electrical resistivity of solder joints depending on various surface finishes and on the number of reflow processes. The electrical resistivity was determined after 1, 2, 3, 5 and 6 reflow cycles as a replacement for the basic accelerated aging test. In this article, various surface finishes are compared by measuring electrical resistivity of solder joints between two soldering pads. The influence of standard surface finishes (ENIG, Lead HASL, Lead-free HASL, Cu, ImSn) with the new developed surface finish based on SnAg7 is also compared. Measurements show that the electrical resistivity is dependent on surface finish type and the thickness of the solder joint. The results prove that the new developed surface finish based on SnAg7 is stable against multiple reflows and comparable to the surface finish based on Au. The new developed surface finish based on SnAg7 can be recommended as a replacement for other conventional surface finishes.

Keywords

• surface finish
• electrical resistivity
• multiple reflows