This part of IEC 61249 gives requirements for properties of prepreg that are mainly intended to be used as bonding sheets in connection with laminates according IEC 61249-2-37 when manufacturing multilayer boards according to IEC 62326-4. Multilayer boards comprised of these materials are suitable for lead-free assembly processes. This material may also be used to bond other types of laminates. Prepreg according to this standard is of defined flammability (vertical burning test). The flammability rating on fully cured prepreg is achieved through the use of non-halogenated flame retardants contained as an integral part of the polymeric structure. After curing of the prepreg according to the supplier’s instructions, the glass transition temperature is defined to be 150 °C and 200 °C.