The present invention relates to a wiring board where a plurality of bumps are formed of conductive brazing material on an insulting film, as well as a manufacturing method for a wiring board.
Inkjet printers carry out color printing using a plurality of ink cartridges having colors such as cyan, magenta, yellow and black. Inks which are supplied from the ink cartridges are jetted from a plurality of discharging openings which are formed in an inkjet head by means of pressure applied by a piezoelectric element. The piezoelectric element has a plurality of individual terminals for applying a drive voltage corresponding to the ink discharging openings. A drive voltage is applied to each of the individual terminals from a driving IC via a flexible wiring board which is connected to the piezoelectric element. A flexible wiring board is used to convey a drive voltage, a control signal and the like, and thereby, flexibility in mounting can increase when the inkjet head is mounted on the inkjet printer. In addition, the inkjet printer can be miniaturized.
A plurality of solder bumps are provided on one surface (a surface for connection with the piezoelectric element) of the flexible wiring board such that terminals of the piezoelectric element correspond in position. The solder bumps on the flexible board and the terminals of the piezoelectric element are press bonded with heating, such that the flexible board and the piezoelectric element are electrically connected. The solder bumps are formed by providing solder to wires (terminal lands) of the flexible wiring board. The solder bumps are formed in accordance with a method having, for example, the following steps: (i) a mask for the formation of solder bumps is made to make contact with a flexible wiring board; (ii) cream solder that has been applied on the mask is wiped off using a squeegee; (iii) the cream solder with which the openings in the mask are filled in is transferred to the flexible wiring board when the cream solder is wiped off, (iv) the cream solder is heated and melted in a reflow furnace. As a result, solder is provided to the terminal lands of the wires.
The structure of connection on the flexible wiring board described in Japanese Patent Application Laid-Open No. 2004-114609 is formed in accordance with a method having the following steps: (i) a line of a plurality of terminal lands is provided to an insulator in band form; (ii) through holes are created in the insulator so as to correspond to locations where terminal lands are provided, such that the terminal lands are exposed from the surface of the insulator opposite to the side on which the terminal lands are provided; (iii) solder is provided to the exposed terminal lands, such that solder bumps are formed; (iv) the terminals of the piezoelectric element and the terminal lands are connected via the solder bumps.