Patent ID: 7467468

Claim:
A method for manufacturing an ink-jet head comprising the steps of: forming a plurality of conductors on one face of a substrate of the ink-jet head; forming, in the substrate, a plurality of through holes corresponding to the plurality of conductors, respectively, and each of the through holes having a diameter increasing from the one face of the substrate toward an other face of the substrate that is parallel to the one face; attaching, from the other face, metal balls to the conductors that are exposed outside via the through holes; and heating and thus melting the metal balls, so that the conductors are bonded, through the melted balls, to a plurality of electrodes, respectively, that are formed in correspondence with the respective conductors along a plane parallel to the one face of the substrate, wherein, in the step of forming the plurality of through holes, each of the through holes are formed in such a manner as to satisfy Equation (1) below: R>d/ 2 +t /tan θ where: d represents a width of an opening of the through hole on the one face; θ represents an angle of inclination of a sidewall defining the through hole with respect to the one face; R represents a shortest distance from a center of the through hole to a periphery of one of the electrodes that neighbors another one of the electrodes corresponding to the through hole; and t represents a thickness of the substrate; wherein d, θ, R, and t are selected to satisfy Equation (1).