Establishes the requirements for the evaluation of liquid and dry film solder mask material and for the determination of the acceptability of use on a standard printed board system. IPC-SM-840 provides two classes of requirements, T and H, to reﬂect functional performance requirements and testing severity based on industry/end use requirements. Coverage is given to adhesion, material qualification, resistances to solvents, and electrical requirements. Revision E incorporates requirements for flexible cover materials used as a flexible dielectric protective layer over etched conductors and other conductive features.19 pages. Released December 2010.