Low void solder joint for multiple reflow applications

摘要

A method is provided for the forming of a metallic solder joint without a liquid flux to create a solder joint that has minimal voids and can be reflowed multiple times without void propagation. This process can be done for any solder alloy, and is most specifically used in the application of first level thermal interface in a IC or micro processor or BGA microprocessor.

主权项

1. A method for attaching a heat spreader to a die, comprising:
disposing a solid volume of solder between a die and a heat spreader without disposing a liquid flux between the die and the heat spreader, wherein the die is mounted to one face of a substrate, the substrate comprising a plurality of metalized contacts for solder attachment on the opposite face; and reflow soldering an assembly comprising the die, the heat spreader and the substrate in the presence of an inert and oxide reducing gas mixture under a first temperature profile to form a package capable of undergoing subsequent reflow processes at equal or elevated temperature profiles; wherein reflow soldering the assembly in the presence of an inert and oxide reducing gas mixture under a first temperature profile comprises subjecting the assembly to a first temperature for a sufficient length of time for the oxide reducing gas to reduce an amount of oxides present on surfaces to be soldered, and subsequently subjecting the assembly to a second temperature sufficient to decompose the oxide reducing gas.