Abstract: Method for controlling the deposition of solder on a heat spreader or heat sink is disclosed. The method comprises applying an attaching flux and finishing flux to a heat spreader, placing a preform thereon and subjecting the same to reflow conditions. The finishing flux is applied to solubilize the normally insoluble corrosive residues that would occur when the attaching flux is subjected to reflow conditions with the preform and heat spreader. Alternatively, the attaching flux may be applied to the preform and heat spreader before undergoing reverse reflow conditions and then the finishing flux is applied to the solder deposit and heat spreader and the same subjected to second reflow conditions. After each method, the residues left from the attaching flux which are solubilized by the finishing flux, are cleaned by washing with a typical solvent. The solder deposit can be optionally flattened before coupling with a die.

Abstract: Method for controlling the deposition of solder on a base metal or substrate is disclosed. The method comprises applying an attaching flux and finishing flux to a substrate, placing a preform thereon and subjecting the same to reflow conditions. The finishing flux is applied to solubilize the normally insoluble corrosive residues that would occur when the attaching flux is subjected to reflow conditions with the preform and substrate. Alternatively, the attaching flux may be applied to the preform and substrate before undergoing reverse reflow conditions and then the finishing flux is applied to the solder deposit and substrate and the same subjected to second reflow conditions. After each method, the residues left from the attaching flux which are solubilized by the finishing flux, are cleaned by washing with a typical solvent.