Pastes are disclosed that are configured to coat a passage of a substrate. When the paste is sintered, the paste becomes electrically conductive so as to transmit electrical signals from a first end of the passage to a second end of the passage that is opposite the first end of the passage. The metallized paste contains a lead-free glass frit, and has a coefficient of thermal expansion sufficiently matched to the substrate so as to avoid cracking of the sintered paste, the substrate, or both, during sintering.