An initiation system that includes a housing, an exploding foil initiator and a securing structure. The housing is formed of plastic and defines a cavity with an open end. The exploding foil initiator assembly has an initiator chip, a flyer layer and a barrel. The initiator chip has an electrically conductive bridge and is at least partly encapsulated in the plastic of the housing. The flyer layer has a first side, which faces the bridge, and a second side opposite the first side. The barrel is disposed between the second side of the flyer layer and an end of the cavity opposite the open end. The securing structure is formed of metal and is partly encapsulated in the plastic of the housing. The securing structure is disposed about the cavity and extends away from the housing about a perimeter of the open end of the cavity.