Abstract: A method for detecting the completion of electrolessly depositing metal into a via. The method includes providing a non-autocatalytic detection mask with an opening over a via containing an autocatalytic material, electrolessly depositing a conductive metal into the via which fails to plate to the mask, and continuing the deposition until metal in the via contacts the mask, at which time the electrochemical potential of the mask changes and the metal plates to and covers the entire mask. The completion of the electroless via fill can be detected by changes in both the appearance and electrochemical potential of the mask.