Method for making nanostructured soldered or brazed joints with reactive multilayer foils

Abstract

Self-propagating formation reactions in nanostructured multilayer foils provide rapid bursts of heat at room temperature and therefore can act as local heat sources to melt solder or braze layers and join materials. This reactive joining method provides very localized heating to the components and rapid cooling across the joint. The rapid cooling results in a very fine microstructure of the solder or braze material. The scale of the fine microstructure of the solder or braze material is dependant on cooling rate of the reactive joints which varies with geometries and properties of the foils and components. The microstructure of the solder or braze layer of the joints formed by melting solder in a furnace is much coarser due to the slow cooling rate. Reactive joints with finer solder or braze microstructure show higher shear strength compared with those made by conventional furnace joining with much coarser solder or braze microstructure. It is expected that the reactive joints may also have better fatigue properties compared with conventional furnace joints.

1 . A method of joining together a first body and a second body comprising the steps of:
 disposing between the first body a second body, a reactive multilayer foil and at least one layer of braze or solder material adjacent the foil;   pressing the bodies together against the foil; and   igniting the foil to melt the braze or solder,   wherein the melted braze or solder has a cooling rate sufficient to produce a lamellar spacing when solidified of less than 100 nanometers.   
   
   
       2 . The method of  claim 1  wherein the reactive multilayer foil is a freestanding reactive multilayer foil. 
   
   
       3 . A method of joining together a first body and a second body comprising the steps of:
 disposing between the first body a second body, a reactive multilayer foil and at least one layer of braze or solder material adjacent the foil;   pressing the bodies together against the foil; and   igniting the foil to melt the braze or solder,   wherein the melted braze or solder has a cooling rate sufficient to produce a lamellar spacing when solidified of less than 50 nanometers.   
   
   
       4 . A method of joining together a first body and a second body comprising the steps of:
 disposing between the first body a second body, a reactive multilayer foil and at least one layer of braze or solder material adjacent the foil;   pressing the bodies together against the foil; and   igniting the foil to melt the braze or solder,   wherein the melted braze or solder has a cooling rate sufficient to produce a lamellar spacing when solidified of less than 10 nanometers.