A method for high temperature bonding of substrates may include providing a top substrate and a bottom substrate, and positioning an insert between the substrates to form a assembly. The insert may be shaped to hold at least an amount of Sn having a low melting temperature and a gap shaped to hold at least a plurality of metal particles having a high melting temperature greater than the low melting temperature. The assembly may be heated to below the low melting temperature and held for a first period of time. The assembly may further be heated to approximately the low melting temperature and held for a period of time at a temperature equal to or greater than the low melting temperature such that the amount of Sn and the amount of metal particles form one or more intermetallic bonds. The assembly may be cooled to create a bonded assembly.