Authors: Kevin Tan, Casey Ng, and Dennis Lim Company: Henkel Singapore Pte Ltd. Date Published: 5/19/2011
Abstract: The RoHS in the recent years have effectively limited the use of Sn/Pb alloy for use in electronics assembly applications. Of the various candidates to replace the Sn/Pb alloys, the most popular alloy is the Sn/3.0-Ag/0.5Cu (SAC305) alloy. The effects of material properties such as flux chemistry, powder size and also process parameters such as the reflow profile on flux spatter performance are examined using a simple manual print and reflow method. While the phenomenon of voiding in SAC alloy is thoroughly studied, the flux spatter characteristics of this alloy remain a myth. Thermo-gravimetric analysis (TGA) conducted on various solder pastes show that flux spatter has a relation to the amount of solvents in the paste, in particular, the more the weight loss; the worst the flux spatter performance. Differential scanning calorimetric analysis (DSC) of flux shows that the phase change temperature as well as the latent heat energy for phase change also affects flux spattering. Based on the experimental results, a mechanism to how flux spatter occur is hypothesized.