JP2011189720A - Thermal print head and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress electrostatic charging caused by friction with a printed medium without impeding conveyance of the printed medium. <P>SOLUTION: The heating element plate 20 of a thermal print head 10 is placed on a heat dissipation plate 30 and includes: a resistor 24 on the surface of an insulation substrate 22; an electrode 25 extending from a bonding pad 31 and connected to the resistor 24; and a protective film 26. A circuit substrate 11 is placed on the same side as the heating element plate 20 of the heat dissipation plate 30. Bonding wires 18 are stretched between the bonding pad 31 of the heating element plate 20 and a drive IC 17 mounted on the heating element plate 20 and between the drive IC 17 and an IC connection terminal 32 on the circuit substrate 11. The bonding pad 31, IC connection terminal 32, drive IC 17, and bonding wires 18 are sealed with a sealing resin 28. A conductive film 12 covers the protective film 26 and sealing resin 28. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thermal print head and a manufacturing method thereof.

  The thermal print head is an output device that heats a plurality of resistors arranged in the main scanning direction and forms images such as characters and figures on a printing medium such as a thermal recording paper by the heat. This thermal print head is widely used in recording devices such as barcode printers, digital plate-making machines, video printers, imagers, and seal printers.

  A general thermal print head includes a heat radiating plate, a heat generating plate attached to the heat radiating plate, and a circuit board attached to the heat radiating plate on the same side as the heat generating plate. Heat generating resistors are linearly arranged at predetermined intervals in a heat generating region extending in a band shape on the surface opposite to the surface of the heat generating plate opposite to the heat radiating plate. In addition, a driver IC that is a part of a drive circuit that drives the heating element is mounted on, for example, a heating element plate. A cover may be provided to protect the driver IC (see, for example, Patent Document 1).

  A printer using such a thermal print head generally includes a platen roller formed in a cylindrical shape with a material having a predetermined elasticity. The platen roller is disposed so that its side surface is in contact with the heat generation area on the support substrate with the main scanning direction as an axis, and is provided to be rotatable about the axis. Due to the rotation of the platen roller, the medium inserted between the platen roller and the heat generating area moves in the sub-scanning direction perpendicular to the main scanning direction. While pressing the medium against the heat generation area by the platen roller, the medium is moved in the sub-scanning direction, and the heat generation pattern of the heat generation area is changed with the movement of the medium, thereby forming a desired image on the printing medium.

  Since the printing medium moves while contacting the thermal phosphorus and the surface of the head, static electricity may be charged. The electrostatic charging may hinder the conveyance of the printing medium or may break the insulation of the protective film on the surface of the thermal print head. Thus, for example, Patent Document 2 discloses a method of further providing a conductive protective film on the surface of the insulating protective film of the heating plate.

JP-A-5-169699 JP 2001-47652 A

  Even if a conductive protective film is provided on the surface of the thermal print head to prevent static electricity due to friction with the printing medium, if the cover for protecting the drive IC is provided, the printing medium will be There is a case where the printing medium is hindered by being caught by the step. Even when a cover for protecting the driving IC is not used, a gap or a step is generated between the heating plate and the circuit board, which may hinder the conveyance of the printing medium. Further, in the absence of such a cover, there is a high possibility that the printed medium will collide with the driving IC or the resin sealing it, and the wiring between the driving IC or the driving IC and the heating plate will be damaged. Become.

  SUMMARY An advantage of some aspects of the invention is that static electricity due to friction with a printing medium is suppressed without hindering conveyance of the printing medium.

  In order to solve the above-described problems, the present invention provides a thermal print head, wherein a heat sink, an insulating substrate, a resistor provided on a surface of the insulating substrate, and a bonding pad are connected to the resistor. An electrode, an electrically insulating protective film covering the resistor and a part of the electrode excluding the bonding pad, and a heating element plate placed on the heat dissipation plate, and an IC connection terminal A circuit board placed on the same side of the heat dissipation plate as the heating element plate, a driving IC mounted on either the heating element plate or the circuit board, the bonding pad, and the driving IC. A bonding wire spanned between the drive IC and the IC connection terminal, the bonding pad, the IC connection terminal, the driver IC, and the bonding wire. Characterized by comprising a sealing resin, and a conductor film covering the sealing resin and the protective film.

  The present invention is also directed to a method of manufacturing a thermal printhead, wherein an insulating substrate, a resistor provided on a surface of the insulating substrate, an electrode extending from a bonding pad and connected to the resistor, and the electrode A first step of forming a heat generating plate including a part excluding a bonding pad and the electrically insulating protective film covering the resistor; and the heat generating plate of the heat radiating plate including an IC connection terminal; A second step of forming a circuit board placed on the same surface, a third step of mounting a drive IC on either the heating plate or the circuit board, the first step, and the second step. And after the third step, a fourth step of placing the heating element plate and the circuit board on a heat sink, and after the fourth step, between the bonding pad and the driving IC and between the driving IC and the IC connection terminal A fifth step of bridging a bonding wire therebetween, a sixth step of sealing the bonding pad, the IC connection terminal, the driver IC, and the bonding wire with a sealing resin after the fifth step; And a seventh step of covering the protective film and the sealing resin with a conductor film.

  ADVANTAGE OF THE INVENTION According to this invention, the electrostatic charge by friction with a printing medium can be suppressed, without inhibiting conveyance of a printing medium.

It is sectional drawing in one Embodiment of the thermal print head which concerns on this invention. FIG. 2 is a partially cut-out top view of an embodiment of a thermal print head according to the present invention. 1 is a cross-sectional view of a part of a thermal printer using an embodiment of a thermal print head according to the present invention.

  An embodiment of a thermal print head according to the present invention will be described with reference to the drawings. Note that this embodiment is merely an example, and the present invention is not limited thereto.

  FIG. 1 is a cross-sectional view of an embodiment of a thermal print head according to the present invention. FIG. 2 is a partially cutaway top view of the thermal print head of the present embodiment.

  The thermal print head 10 according to the present embodiment includes a heat generating plate 20, a circuit board 11, and a heat radiating plate 30. The heat generating plate 20 and the circuit board 11 are placed on the heat radiating plate 30. The heat sink 30 is a plate formed of a metal such as aluminum.

The heating element plate 20 includes a substrate 22, a glaze layer 23, a resistor 24, an electrode 25, a protective film 26, and a driving IC. The substrate 22 is formed in a rectangular plate shape with an insulator such as alumina (Al ₂ O ₃ ), for example. The glaze layer 23 is formed on one surface of the substrate 22 in a layered manner, for example, with silicon oxide (SiO ₂ ).

  The resistor 24 is formed on the surface of the glaze layer 23 in a layered manner, for example, with cermet. A plurality of resistors 24 are provided at intervals in the longitudinal direction of the substrate 22, that is, in the main scanning direction. The resistor 24 extends in the sub-scanning direction perpendicular to the main scanning direction.

  The electrode 25 is formed on the surface of the resistor 24 in a layered manner, for example, aluminum. The electrode 25 extends in the width scanning direction with a gap therebetween. An electrode 25 extending to one side with respect to the gap on the resistor 24 extends from the bonding pad 31. The electrodes 25 extending from the bonding pads 31 are independently connected to the respective resistors 24. The electrode 25 extending on the opposite side of the bonding pad 31 with respect to the gap on the resistor 24 is connected to the common electrode 33.

  Since the current flowing through the electrode 25 passes through the resistor 24 in the gap portion on the resistor 24, the portion corresponding to the gap of the resistor 24 becomes a heat generating portion. The heat generating portions are arranged at intervals in the longitudinal direction of the substrate 22, that is, in the main scanning direction, and form a heat generating region extending in the main scanning direction.

  A part of the electrode 25 excluding the bonding pad 31, the glaze layer 23, and the resistor 24 are covered with a protective film 26 formed of an electrically insulating material. The driving IC 17, which is a semiconductor integrated circuit that supplies current to the heat generating portion, is mounted on the surface of the glaze layer 23, for example, near the outer periphery in the vicinity of the bonding pad 31.

  The circuit board 11 is formed in a rectangular plate shape, for example. On the circuit board 11, an electric circuit including IC connection terminals 32 provided at intervals along the long side is formed. A ground portion 35 is formed in the electric circuit on the circuit board 11. Most of the surface of the circuit board 11 is covered with an electrically insulating film 34. The film 34 is not formed in the vicinity of the IC connection terminal 32 and a part of the ground part 35, and a part of the IC connection terminal 32 and the ground part 35 is exposed on the surface of the circuit board 11. Further, the circuit board 11 has, for example, the long side adjacent to the IC connection terminal 32 on the same side as the heat generating plate 20 of the heat radiating plate 30 faces the long side where the bonding pads 31 of the heat generating plate 20 are arranged. , Have been placed. The driving IC 17 may be mounted on the circuit board 11.

  Bonding wires 18 are bridged between the bonding pads 31 and the driving IC 17 and between the driving IC 17 and the IC connection terminal 32. The bonding pad 31, the IC connection terminal 32, the driving IC 17 and the bonding wire 18 are sealed with a sealing resin 28. The sealing resin 28 also covers a portion not covered with the protective film 26 in the vicinity of the bonding pad 31 and a portion not covered with the electrically insulating film 34 in the vicinity of the IC connection terminal 32.

  Further, on the surface of the thermal print head 10 of the present embodiment, a conductor film 12 having a thickness of, for example, about 1 to 2 μm is formed to cover the protective film 26 and the sealing resin 28. The conductor film 12 is formed of a material having electrical conductivity such as a metal such as TiC, Ti, TiCN, Cr, or CrN or an intermetallic compound. Depending on the material forming the conductor film 12, the material may be too hard and brittle. Therefore, the thickness of the conductor film 12 is appropriately adjusted according to characteristics such as ductility of the material.

  The conductor film 12 is also formed on a part of the surface of the ground portion 35 that is not covered with the electrically insulating film 34 of the circuit board 11. For this reason, the entire conductor film 12 has the same potential as the ground portion 35 of the circuit board 11.

  FIG. 3 is a cross-sectional view of a part of a thermal printer using the thermal print head of the present embodiment.

  The thermal printer using the thermal print head 10 has a platen roller 50 formed in a cylindrical shape with a material having a predetermined elasticity. The platen roller 50 has a shaft 52 on a straight line parallel to the main scanning direction, and is provided to be rotatable about the shaft 52. Further, the platen roller 50 is disposed such that its side surface is in contact with the conductive film 12 on the heat generating portion on the resistor 24 of the heat generating plate 20. A control signal and driving power for forming a predetermined heat generation pattern in the heat generating portion of the thermal print head 10 are input to the circuit board 11 and further input to the heating element plate 20 electrically connected to the circuit board 11. .

  Due to the rotation of the platen roller 50, the printing medium 60 inserted between the platen roller 50 and the heat generating portion of the thermal print head 10 moves in the sub-scanning direction perpendicular to the main scanning direction. The printing medium 60 is, for example, thermal paper that develops color when heated to a color development temperature or higher. While the printing medium 60 is pressed against the heat generating portion by the platen roller 50, the printing medium 60 is moved in the sub-scanning direction, and the heat generation pattern of the heat generating area 24 is changed along with the movement of the heat sensitive recording medium 60. Are formed on the printing medium 60.

  Next, a method for manufacturing the thermal print head according to the present embodiment will be described.

  First, an insulating plate to be the substrate 22 is formed, and a glass paste is printed on the surface of the insulating plate. Next, the insulating plate on which the glass paste is printed is fired. Thereby, the glass on which the pattern is printed is melted and fixed to the insulating plate. Thereafter, a resistance material such as cermet is fixed to the surface of the glaze layer 23 by sputtering or the like.

  Thereafter, the resistance material is patterned by etching so as to form a resistor 24 having a predetermined shape. Further, a conductive material such as aluminum is fixed to the plate on which the resistor 24 is formed by sputtering or the like. Thereafter, the conductive material is patterned by etching so as to form the electrode 25 having a predetermined shape.

  Further, a protective film 26 is formed on the surface of the plate on which the electrode 25 is formed. Further, the drive IC 17 is disposed at a predetermined position.

  Thereby, the heating element plate 20 is completed. In addition, after forming the glaze layer 23, the resistor 24, the electrode 25, and the protective film 26 corresponding to the plurality of heating element plates 20 on an insulating plate larger than one heating element plate 20, a plurality of heat generations are performed by dicing or the like. The body plate 20 may be divided. Further, after forming the glaze layer 23, after forming the electrode 25, or after forming the protective film 26, it may be divided into portions corresponding to the plurality of heating element plates 20.

  The heating plate 20 thus formed is placed on the heat sink 30 together with the circuit board 11. Thereafter, the heating plate 20 and the circuit board 11 are connected by the bonding wire 18, and the connection portion by the bonding wire 18 is sealed by the sealing resin 28.

  Thereafter, the conductor film 12 is formed on the surface of the assembly of the heat generating plate 20, the circuit board 11, and the heat radiating plate 30 partially sealed with the sealing resin 28. The conductor film 12 is formed by vapor deposition, for example. The conductor film 12 can be formed not only by vapor deposition but also by ion plating or sputtering.

  When the conductor film 12 is deposited on the assembly, the assembly is first placed in a container, and the degree of vacuum is increased by discharging gas from the container. Thereafter, TiC or the like is vapor-deposited on the assembly at room temperature, for example. At this time, it is preferable to form the film relatively slowly so that the temperature of the assembly does not become excessively high. Before vapor deposition of the conductor film 12, it is preferable to increase the surface roughness of the surface on which the conductor film 12 is formed.

  When forming the conductor film 12, the assembly of the heating plate 20, the circuit board 11, and the heat dissipation plate 30 partially sealed with the sealing resin 28 is not heated to a high temperature. Damage due to thermal deterioration or high temperature of constituent materials such as the circuit board 11 is suppressed. On the other hand, by increasing the surface roughness of the surface on which the conductor film 12 is formed, the conductor film 12 is more firmly fixed to the surface, and the morphological stability of the conductor film 12 is improved.

  The conductor film 12 is formed only in a predetermined portion by forming the conductor film 12 such as a terminal portion to which electric power or a signal from the outside is input in a state where a portion where the conductor film 12 should not be formed is covered with a cover or the like. can do. The conductor film 12 may also be formed on the side surface or the back surface of the thermal print head 10, for example. When the conductor film 12 is formed also on the side surface and the back surface, the conductor film 12 is prevented from coming into contact with the common electrode 33 by covering it with a cover other than the conductor that should be at the ground potential.

  In the thermal print head 10 of the present embodiment, the surfaces of the protective film 26 and the sealing resin 28 are covered with the conductor film 12. For this reason, electrostatic charging due to friction with the printing medium 60 can be suppressed.

  Further, the drive IC 17, the bonding wire 18 and the sealing resin 28 for sealing them are covered with the conductor film 12. For this reason, the damage by the collision of the printing medium 60 can be suppressed. As a result, there is no need to provide a cover for protecting the drive IC 17 and the like, and the joints or steps that are inevitably generated by providing the cover are eliminated. Further, by covering the entire surface portion with which the printing medium 60 may be in contact with the conductor film 12, the surface portion with which the printing medium 60 may be in contact is seamless. Therefore, the cause of obstructing the conveyance of the printing medium 60 is reduced, and the conveyance of the printing medium 60 is smooth.

  A high frequency drive circuit is formed on the circuit board 11 and other portions. However, since the circuit board 11 and the like are covered with the conductor film 12, the intrusion of noise from the outside or the leakage of noise to the outside is shielded. The effect of noise suppression can be enhanced by covering a wider portion, for example, the side surface and the back surface of the thermal print head 10 with the conductor film 12.

  When the conductor film 12 is formed by vapor deposition or the like, the conductor film 12 is connected to the ground, so that it is not necessary to separately connect the conductor film 12 for preventing electrostatic charge to the ground. . For this reason, the number of parts is reduced and the time required for assembly is reduced.

DESCRIPTION OF SYMBOLS 10 ... Thermal print head, 11 ... Circuit board, 12 ... Conductor film, 17 ... Drive IC, 18 ... Bonding wire, 20 ... Heat generating body plate, 22 ... Substrate, 23 ... Glaze layer, 24 ... Resistor, 25 ... Electrode , 26 ... protective film, 28 ... sealing resin, 31 ... bonding pad, 32 ... IC connection terminal, 33 ... common electrode, 34 ... film, 35 ... ground part, 30 ... heat sink, 50 ... platen roller, 52 ... shaft , 60 ... Printed medium

Claims (5)

A heat sink,
An insulating substrate; a resistor provided on a surface of the insulating substrate; an electrode extending from a bonding pad and connected to the resistor; An insulating protective film, and a heating element plate mounted on the heat sink,
A circuit board provided with an IC connection terminal and placed on the same side as the heating plate of the heat sink;
A driving IC mounted on any of the heating plate and the circuit board;
A bonding wire spanned between the bonding pad and the driving IC and between the driving IC and the IC connection terminal;
A sealing resin for sealing the bonding pad, the IC connection terminal, the driver IC, and the bonding wire;
A conductor film covering the protective film and the sealing resin;
A thermal print head comprising:   The thermal print head according to claim 1, wherein the conductive film is grounded.   The thermal print head according to claim 1, wherein the conductor film also covers a surface of the circuit board.   4. The thermal print head according to claim 1, wherein the conductor film also covers side surfaces of the heating element plate and the circuit board. 5. An insulating substrate; a resistor provided on a surface of the insulating substrate; an electrode extending from a bonding pad and connected to the resistor; A first step of forming a heating element plate comprising an insulating protective film;
A second step of forming a circuit board provided with an IC connection terminal and placed on the same side of the heat dissipation plate as the heating element plate;
A third step of mounting a driving IC on either the heating plate and the circuit board;
After the first step, the second step, and the third step, a fourth step of placing the heating element plate and the circuit board on a heat sink,
A fifth step of bridging a bonding wire between the bonding pad and the driving IC and between the driving IC and the IC connection terminal after the fourth step;
After the fifth step, a sixth step of sealing the bonding pad, the IC connection terminal, the driver IC, and the bonding wire with a sealing resin;
A seventh step of covering the protective film and the sealing resin with a conductor film;
A method of manufacturing a thermal print head, comprising:

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