There are no set requirements for minimum lead free solder finishes. In addition, tin-lead thickness varies dramatically based on pad size. Furthermore, minimum coating thickness is more critical to the solderability of SN100CL more than it is to standard tin-lead finish.
After analyzing thousands of panels in coordination with subsequent solderability results, we established the following guidelines and coupon.
Click here for Coupon Description
SEC also provides a gerber of this coupon that you can insert into waste area of your boards.