As Pb-free soldering becomes more accepted in the electronics community, the use of Pb-bearing surface finishes for printed circuit boards is being phased out.  Alternative circuit board finishes include organic solder preservatives (OSP); electroless nickel (Ni)/immersion gold (Au) or “ENIG”, nickel palladium (Ni/Pd) with a Au flash over the Pd; immersion tin (Sn) and immersion silver (Ag).  The surface finish that has become increasingly more attractive in the circuit board industry is immersion Ag. 

 
The solderability of an immersion Ag finish was evaluated after exposure to a Battelle Class 2 accelerated environment that is used to accelerate the chemical stresses associated with storage in an industrial environment.  The solderability metric was the contact angle, (θ_C), as determined by the meniscometer/wetting balance technique.  Auger surface and depth profile analyses were utilized to identify changes in the coating chemistry that are consistent with the trends in solderability.