Process for controlled braze joining of electronic packaging elements

Claim 1

A method of forming a brazed bond between a flat surface of a I/O pin head and a flat surface of a metallized pad on a ceramic substrate of a semiconductor package comprising the steps of; providing a Au metal layer on at least one of said flat pin head surface or said flat metallized pad surface, placing the mask of a low melting Au-Sn alloy with a composition of 80% Au±5% with the balance being Sn between said pin head surface and said metallized pad surface, heating the resultant assembly to a temperature in the range of 350° to 450° C., simultaneously with said heating, applying a pressure in the range of 250 to 2500 dynes/cm 2 to said surfaces sufficient to squeeze the major portion of the resultant molten Au-Sn alloy from between the surfaces, and cooling the assembly, the bond between said pin head and said metallized pad formed of a relatively higher melting Au-Sn alloy resulting when the major portion of the alloy is removed allowing the major portion of the Sn in the small remaining portion of the alloy to combine with the Au layer to reduce the relative amount of Sn in the brazing bond alloy leaving a higher melting alloy.

Claim 2

A method of forming a brazed bond between a flat surface of a I/O pin head and a flat surface of a metallized pad on a ceramic substrate of a semiconductor package comprising the steps of; providing a Au metal layer on at least one of said flat pin head surface or said flat metallized pad surface, placing the mask of a low melting Au-Sn alloy with a composition of 80% Au±5% with the balance being Sn between said pin head surface and said metallized pad surface, heating the resultant assembly to a temperature in the range of 350° to 450° C., simultaneously with said heating, applying a pressure in the range of 250 to 2500 dynes/cm 2 to said surfaces sufficient to squeeze the major portion of the resultant molten Au-Sn alloy from between the surfaces, and cooling the assembly, the bond between said pin head and said metallized pad formed of a relatively higher melting Au-Sn alloy resulting when the major portion of the alloy is removed allowing the major portion of the Sn in the small remaining portion of the alloy to combine with the Au layer to reduce the relative amount of Sn in the brazing bond alloy leaving a higher melting alloy.