FISCHER COULOSCOPE® CMS
|INITIAL SN COATING THICKNESS||DURATION OF TEMPERING PROCEDURE [H]|
|ca. 0.5 µm||Mean value||0.52||0.12||0.04||(*)|
|ca. 1 µm||Mean value||1.01||0.60||0.50||0.43|
Mean values in µm of 9 (0 h tempering) and 3 (2, 4, 6 h tempering) measurement series; (*) not measurable because the remaining layer of pure tin is too thin.
The jump in de-plating potential between the pure tin coating and SnCu diffusion zone.
The Coulometric method makes obvious the drop in thickness of the pure tin coating. The measurement series with the 0.5 µm samples clearly shows that, even after only two hours of tempering, too little tin remains to guarantee proper solderability.
To check the solderability of coating systems on PCBs, the thickness of the remaining pure tin can be measured without being influenced by the SnCu-alloy using the FISCHER COULOSCOPE® CMS. For more information please contact your local FISCHER representative.