Patent ID: 7897059

Claim:
A method is provided for removing tin solder residues from molds used in solder transfer processes such as the C4NP process comprising the steps of: providing a mold containing an array of openings (cavities) corresponding to an array of capture pads on a substrate surface such as a wafer surface, the openings being filled with a tin-containing solder; positioning the openings in the mold and the capture pads of the substrate surface so that the solder in the mold can be transferred to the corresponding capture pad on the substrate; transferring the solder in the mold to the corresponding capture pads of the substrate leaving an empty mold; removing the empty mold from the substrate; removing residual tin from the mold by immersing the empty mold within an aqueous composition comprising cupric ions and HCl for an effective time and temperature to remove the tin from the mold, wherein the cupric ions are in an amount of about 0.5 M to 3.0 M and the HCl in an amount of about 0.5 M to about 4.0 M and the effective temperature ranges from about 15 to 30° C.; and providing air or oxygen into the aqueous composition during the etching process to both agitate the aqueous composition to facilitate removal of insoluble cuprous chloride film and to regenerate the aqueous composition by oxidizing Cu + 1 to Cu + 2 thereby maintaining a suitable etch rate.