IPC has established a testing standard for solder masks which is used as a industry guideline for material manufactures, OEM’s and PCB manufactures. IPC SM-840D classifies solder mask, Class T and Class H which are summarized below;

T – Telecommunication: includes computers, telecommunication equipment, sophisticated business machines, instruments, and certain non-critical military applications.) Solder mask on boards in this class is suitable for high performance commercial and industrial products in which extended performance life is required, but for which interrupted service is not life-threatening.

H – High Reliability/Military: includes that equipment where continued performance is critical, equipment down-time cannot be tolerated and/or the equipment is a life support item). Solder mask on boards of this class is suitable for applications where high levels of assurance are required and uninterrupted service is essential.

Below is a database of common solder mask materials for your reference: