Thermal head, thermal head unit, and method of manufacture thereof

A thermal head unit comprising:

• a thermal head having a head chip, a plurality of heating elements disposed on an upper surface of the head chip at an end portion thereof, a plurality of electrodes disposed on the upper surface of the head chip and connected to the heating elements, a wiring substrate disposed on a lower surface of the head chip so that the end portion of the head chip protrudes from the wiring substrate, and a semiconductor integrated circuit mounted on the wiring substrate;
• a support member for supporting the thermal head, the support member having an upper step portion connected to the end portion of the head chip and a step difference portion;
• an adhesive agent layer disposed in a clearance formed between the step difference portion and the wiring substrate;
• and an adhesive layer for adhering the end portion of the head chip to the upper step portion of the support member, the adhesive agent layer having a thickness greater than that of the adhesive layer.

A method of manufacturing thermal heads, comprising the steps of:

• providing a plurality of head chips each having an upper surface, a lower surface, a plurality of heating elements disposed on the upper surface, and a plurality of electrodes disposed on the upper surface and connected to the heating elements;
• connecting the head chips to a wiring substrate forming plate;
• mounting a plurality of semiconductor integrated circuits onto the wiring substrate forming plate;
• connecting the electrodes of each head chip to a respective one of the semiconductor integrated circuits;
• and dividing the wiring substrate forming plate into a plurality of sections to form a plurality of thermal heads each having a wiring substrate connected to the lower surface of a respective one of the head chips.

A method of manufacturing a thermal head unit constructed so that a thermal head is held on a support member, the thermal head comprising a head chip having one surface on which heating elements and electrodes connected to the heating elements are provided, and a wiring substrate that is joined to the other surface of the head chip in a state that one end portion of the head chip in the width direction, which serves as a heating element forming portion, is protruded, and that mounts thereon a semiconductor integrated circuit connected to the electrodes, the thermal head unit manufacturing method characterized by comprising:

• a step of supplying an adhesive agent layer to a step difference portion of the support member, the support member having an upper step portion joined to the heating element forming portion, and the step difference portion recessed more deeply than a thickness of the wiring substrate;
• a step of placing the wiring substrate onto the adhesive agent layer provided to the step difference portion using as a reference a joining of the heating element forming portion to the upper step portion prior to hardening of the adhesive agent layer;
• and
• a step of subsequently hardening the adhesive agent layer.

A method of manufacturing a thermal head unit constructed so that a thermal head is held on a support member, the thermal head comprising a head chip having one surface on which heating elements and electrodes connected to the heating elements are provided, and a wiring substrate that is joined to the other surface of the head chip in a state that one end portion of the head chip in the width direction, which serves as a heating element forming portion, is protruded, and that mounts thereon a semiconductor integrated circuit connected to the electrodes, the thermal head manufacturing method characterized by comprising:

• a step of providing a support member having an upper step portion joined to the heating element forming portion, and a step difference portion recessed more deeply than a thickness of the wiring substrate, and fixing the wiring substrate to the step difference portion using as a reference a joining of the heating element forming portion to the upper step portion while placing the wiring substrate to the step difference portion with a clearance therebetween;
• a step of supplying an adhesive agent to the clearance;
• and
• a step of subsequently hardening the adhesive agent layer.

A thermal head comprising:

• a head chip having a first thickness, a first surface, and a second surface opposite the first surface;
• a plurality of heating elements disposed on the first surface of the head chip at a first end portion thereof;
• a plurality of electrodes disposed on the first surface of the head chip and connected to the heating elements;
• a wiring substrate disposed on the second surface of the head chip;
• a semiconductor integrated circuit mounted on the wiring substrate and having a second thickness smaller than the first thickness;
• a common electrode extending in a longitudinal direction along a second end portion of the head chip disposed opposite to the first end portion;
• a plurality of common electrode wirings disposed on the wiring substrate;
• and a plurality of connection wirings connecting the common electrode to the common electrode wirings and disposed at a plurality of locations in the longitudinal direction along the first end portion of the head chip.

A thermal head comprising:

• a head chip having an upper surface, a lower surface and a side surface;
• a plurality of heating elements disposed on the upper surface of the head chip;
• a plurality of electrodes disposed on the upper surface of the head chip and connected to the heating elements;
• a wiring substrate disposed on the lower surface of the head chip;
• a plurality of semiconductor integrated circuits each mounted on the wiring substrate and disposed in contact with the side surface of the head chip and connected to respective ones of the electrodes;
• a common electrode extending in a longitudinal direction along a first end portion of the head chip disposed opposite to a second end portion in a width direction thereof on which the heating elements are disposed;
• a plurality of common electrode wirings disposed on the wiring substrate;
• and a plurality of connection wirings connecting the common electrode to the common electrode wirings and disposed at a plurality of locations in the longitudinal direction along the first end portion of the head chip.

A thermal head comprising:

• a head chip having a first thickness, a first surface, and a second surface opposite the first surface;
• a plurality of heating elements disposed on the first surface of the head chip;
• a plurality of electrodes disposed on the first surface of the head chip and connected to the heating elements;
• a wiring substrate disposed on the second surface of the head chip;
• a semiconductor integrated circuit mounted on the wiring substrate and having a second thickness smaller than the first thickness;
• a common electrode extending in a longitudinal direction along a first end portion of the head chip disposed opposite to a second end portion in a width direction thereof on which the heating elements are disposed;
• a plurality of common electrode wirings disposed on the wiring substrate;
• and a plurality of connection wirings connecting the common electrode to the common electrode wirings and disposed at a plurality of locations in the longitudinal direction along the first end portion of the head chip.

A thermal head comprising:

• a head chip having an upper surface, a lower surface and a side surface;
• a plurality of heating elements disposed on the upper surface of the head chip;
• a plurality of electrodes disposed on the upper surface of the head chip and connected to the heating elements;
• a wiring substrate disposed on the lower surface of the head chip;
• a plurality of semiconductor integrated circuits each mounted on the wiring substrate and connected to respective ones of the electrodes;
• a common electrode extending in a longitudinal direction along a first end portion of the head chip disposed opposite to a second end portion in a width direction thereof on which the heating elements are disposed;
• a plurality of common electrode wirings disposed on the wiring substrate;
• and a plurality of connection wirings connecting the common electrode to the common electrode wirings and disposed at a plurality of locations in the longitudinal direction along the first end portion of the head chip, at least one of the connection wirings being disposed between one adjacent pair of the semiconductor integrated circuits.

A thermal head comprising:

• a head chip having an upper surface, a lower surface and a side surface;
• a plurality of heating elements disposed on the upper surface of the head chip;
• a plurality of electrodes disposed on the upper surface of the head chip and connected to the heating elements;
• a wiring substrate disposed on the lower surface of the head chip;
• a plurality of semiconductor integrated circuits each mounted on the wiring substrate and connected to respective ones of the electrodes;
• a common electrode extending in a longitudinal direction along a first end portion of the head chip disposed opposite to a second end portion in a width direction thereof on which the heating elements are disposed;
• a plurality of common electrode wirings disposed on the wiring substrate;
• and a plurality of connection wirings connecting the common electrode to the common electrode wirings and disposed at a plurality of locations in the longitudinal direction along the first end portion of the head chip, each of the connection wirings being disposed within a respective one of the semiconductor integrated circuits.