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46 SMT Magazine • July 2014 Following the plating process, 69 Copper C110 base metal coupons and 69 Alloy 42 base metal coupons were scratched along the surface. Brown paper wrapping material was cut in sheet sizes approximately 8.5in x 11in, wrinkled by "balling and crushing" and then unraveled and flattened. Each coupon was separately wrapped (one sheet/coupon), then individually laid on a hard surface (i.e., tabletop) and shuffled around several times on each of the flat sides thereby randomly creating light scratches on the tin surface. These scratches were intended to simu- late those found on the surface of component leads as a result of shipping and handling. The typical light scratch created by this method was photo documented. fEATURE TIN WHISKER RISK MANAGEMENT By CoNFoRMAl CoATING continues Also following the plating process, 30 cop- per C110 base metal coupons and 30 Alloy 42 base metal coupons had a 45° bend placed in 2 places as shown in Figure 2 using a machine vise with appropriate protection applied to the jaws of the vise (i.e., Teflon tape or equivalent). This bend was intended to put the tin plating under stress. Necessary precautions were taken to protect the transfer of metal to the tin plat- ing during the bending process. These coupons do not have scratches in the tin plated surfaces. The conformal coatings used in the test- ing were acrylic per MIL-C-46058, Type AR, polyurethane per MIL-C-46058, Type UR, and parylene per MIL-C-46058, type XY. Table 1 in- cludes mechanical properties of the coatings figure 2: Drawing of bent test coupons. (note: for the bent test coupons, the regions of compression and tension in the tin plating, caused through relaxation of the material following the bending process are identified in the schematic.)