Silver plating include both good solderability and electrical contact characteristics, with high electrical and thermal conductivity. Other engineering applications include thermo-compression bonding, wear resistance of load-bearing surfaces, and spectral reflectivity.
QQ-S-365 Silver Plating, Electrodeposited (This cancelled specification is still in wide use.)
Grade A: With supplementary tarnish-resistant treatment (chromate treatment)
Grade B: Without supplementary tarnish-resistant treatment
C0.00032" (0.0004" for steel)
D0.0006" (0.0008" for steel)
ASTM B 700 Electrodeposited Coatings of Silver for Engineering Use
99.9% silver minimum
99.0% silver minimum
98.0% silver minimum
A Matte, no brighteners in plating bath
B Bright, by use of brighteners in plating bath
C Bright, by mechanical or chemical polishing of Grade-A
D Semi-bright, by use of brighteners in plating bath
N No chromate treatment
S With supplementary tarnish-resistant chromate treatment
ABOUT SOLDERABILITY & TARNISH RESISTANCE
Silver plating with chromate-type supplementary dips have a low contact resistance in the order of 300 to 400 microhms per square inch. The items must be soldered using rosin core solder.
ABOUT CORROSION PROTECTION
For applications where corrosion protection is important, the use of an electrodeposited nickel undercoat is advantageous.
a) Silver plating on steel, zinc and zinc-based alloys should have an undercoat of nickel over copper.
b) Silver plating on copper and copper alloys should have a nickel undercoat. Copper and copper alloy material on which a nickel undercoat is not used, and other basis metals where a copper undercoat is employed, should not be used for continuous service at a temperature in excess of 300 degrees F (149 degrees C). Adhesion of the silver plating is adversely affected because of the formation of a weak silver and copper intermetallic layer.