Abstract: An integrated circuit chip is alloyed to a ceramic header for a standard semiconductor package in an elongated preheater fixture. The fixture has a heating position laterally spaced from a loading position, with slots running from the loading to heating positions accommodating the pins of the header. The slots also function as fins to radiate heat so that a temperature gradient is created between loading and heating positions. As the headers slide from the loading position along the length of the fixture, the headers are heated to the bonded temperature without producing undue thermal stress.