Infrared Process Monitor for Glycerine/Edta Flux
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
This technique gives prior warning of solder defects due to faulty flux when a glycerine/EDTA (ethylenediaminetetraacetic acid) flux is used to flux circuit boards prior to soldering. This flux has a useful life of approximately 3-5 weeks. The use of this flux after that can result in extensive solder defects that necessitate replacing the flux with fresh flux. The flux can be tested in the following manner to determine if it is still good. A small drop of the flux is sandwiched between two zinc sulfide plates. An infrared absorbance spectrum is then taken of the resulting thin film. Sloping base lines are drawn of the absorbance peaks at 1735 cm-1 and 1600 cm-1 . The peak height or areas are measured and the 1735 cm-1 peak is ratioed to the 1600 cm-1 peak. This ratio is multiplied by 5 (Fig. 2).