Amorphous brazing foil
Eutectic solder foils as amorphous alloys of the transition metals such as nickel, iron, copper, etc. are produced which contain large amounts of semi-metals / metalloids of silicon and boron and / or phosphorus. These alloys are due to the high proportion of said semi- metals too hard and brittle to produce them on conventional manufacturing routes such as hot and cold rolling in the form of films. Sufficient plastic and elastic properties can be found only if one of these alloys without crystal structure, ie amorphous, manufactures. The content of metalloids in eutectic concentrations is very conducive to the formation of the amorphous structure. In conventional crystalline metal alloys, the atoms are arranged strictly regularly. The atoms of amorphous materials, however, are completely disordered, as in a liquid or melt. Since this is also true for glass, referred to amorphous metals as metallic glass. The Greek term amorphous means shapeless or formless.
Production
The production of amorphous metals is due to the necessary cooling rates, a manufacturing technology that - the rapid solidification technique ( engl. melt spinning ). The liquid metal melt is pressed onto a rotating at 100 km / h Cooling roll. Upon impact with the roll, the melt is cooled in a millisecond to about 1000 ° C.. This corresponds to a cooling rate of one million degrees per second. This creates a very uniform, thin amorphous film with thicknesses between 0.02 to 0.05 mm and film widths between 0.5 mm and 125 mm.
Application forms
Amorphous solder foils are offered exclusively in the form of thin metal foils or produced therefrom moldings. These moldings can be manufactured as cut to length film strips, punched, or photochemically produced molded parts for special applications. The films / parts will be placed between the components to be joined and brazed in the brazing furnace under this inert gas atmosphere or in vacuum. For ready-made solder foils waste is avoided, thus saving material. Solder foils, or moldings are very well suited to be implemented in automatic assembly processes. About the film thickness, which can be finely varied, it is possible to precisely adjust the amount of solder required on the specific application. By the use of films or molded parts made of film, which are specifically designed for the particular application, the avoidance of waste and increases the production rate, which increases the efficiency of the soldering process.
Properties
Amorphous solder foils have even after the crystallization on a particularly uniform composition. Because of this property, the atoms of the alloying elements involved must during melting of the solder foil very short diffusion paths to travel, to form a completely molten phase. As a result, amorphous brazing foils have the most uniform melt and flow behavior of all soldering materials. Therefore, they differ greatly in their soldering properties of similar soldering materials in powder or paste form. The quality of the solder joints produced with amorphous films is very consistent and of the highest quality. Compared to conventional nickel solders, which are applied primarily in paste form, are amorphous brazing foils are characterized by a metal content of 100%. On drying and Ausgasungsprozesse as are required in these pastes can be omitted completely when using amorphous solder foils. The absence of organic components, and the particularly low content of gaseous impurities (oxygen, nitrogen), to bring the particular method of preparation, is very particularly advantageous for Vakuumlötungen. They form no deposits of organic residues on solder joint, components or the brazing furnace.