JP2014188682A - Thermal print head and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the height of a resin projection which seals bonding wire.SOLUTION: A thermal print head 10 is provided with a heat radiation plate 30, a head substrate 20, a circuit substrate 40, and silicone resin 49. The head substrate 20 includes heating resistors 26 arranged on the surface of a rectangular insulation substrate at intervals, and an electrode connected to both end parts of each of the heating resistors 26, and is placed on the heat radiation plate 30. The circuit substrate 40 is placed on the heat radiation plate 30 so that longitudinal sides of the circuit substrate and the head substrate 20 face to each other. A plurality of bonding wires 44 electrically connecting the heating resistors 26 and the circuit substrate 40 are stretched between the head substrate 20 and the circuit substrate 40. The bonding wires 44 and the like are sealed by epoxy-system sealing resin 48. The silicone resin 49 is located at a butt part between the head substrate 20 and the circuit substrate 40.

Description

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

  In recent years, thermal print heads have attracted attention as output devices such as video printers, imagers, and seal printers. The thermal print head performs recording on thermal paper, plate-making film photographic paper, media, and the like by generating heat from heating resistors arranged on a support substrate having a heat retaining layer. Various developments have been made on thermal print heads due to advantages such as low noise and low running cost.

  The support substrate of the thermal print head is obtained by forming a glaze layer as a heat retaining layer on a ceramic substrate such as alumina. A resistor layer and a conductive layer are laminated on the surface of the support substrate by a thin film forming method such as sputtering, and a patterning process is performed to form a pair of heating resistors and individual electrodes on one line. Further, the head substrate of the thermal print head is formed by forming a protective coating layer on a necessary portion of the resistor layer and the conductive layer by a thin film forming method such as sputtering.

  The head substrate and a separately manufactured circuit board are combined with a heat sink. For bonding the head substrate to the heat sink, a method such as fixing with an adhesive or double-sided tape is generally used. After the combination of the head substrate, the circuit substrate, and the heat sink, the electrode is connected to the circuit substrate via a driving IC (Integrated Circuit) with a bonding wire. A thermal print head is completed by resin-sealing the bonding wires.

JP 2005-280204 A

  The resin that seals the bonding wire that spans between the head substrate and the circuit substrate protrudes in a band shape on the surfaces of the head substrate and the circuit substrate. If this resin is too small, the bonding wire is exposed and the soundness is impaired. Therefore, it is necessary to apply the resin with some margin. On the other hand, if the margin is too large, the protruding height of the resin increases. When the protruding height of the resin increases, the possibility of hindering the conveyance of the printing medium increases, and it takes time to cure the resin.

  Therefore, an object of the present invention is to reduce the height of a resin protrusion that seals a bonding wire spanned from a head substrate of a thermal print head to a circuit substrate.

  In order to solve the above-described problems, the present invention provides a thermal printhead, including a heat sink, heaters arranged at intervals on the surface of the insulating substrate, and electrodes connected to both ends of each heater. A rectangular head substrate placed on the heat radiating plate, a circuit board placed on the heat radiating plate so that the long sides of the head substrate face each other, and between the head substrate and the circuit substrate A plurality of bonding wires that are bridged to electrically connect each of the heaters and the circuit board; and a silicone-based resin body that is filled at a position where the long sides of the head substrate and the circuit board face each other. And an epoxy-based resin sealing body that extends in a strip shape across the head substrate and the circuit substrate and seals the bonding wire.

  Further, the present invention provides a method for manufacturing a thermal print head, wherein a plurality of heaters arranged on the surface of a rectangular insulating substrate at intervals in the longitudinal direction of the insulating substrate and electrodes connected to both ends of the heater Forming a head substrate, forming a circuit board on which a drive circuit for driving the heater is mounted, manufacturing a rectangular plate-shaped heat sink, and removing the head substrate from the heat sink A step of applying a silicone resin to a side surface of the head substrate far from the heater, and a side surface of the head substrate on which the silicone resin is applied. Placing the circuit board on the heat sink while pressing the board, bridging a bonding wire between the head board and the circuit board, and the bonding wire The Ya characterized by comprising the step of sealing with resin.

  According to the present invention, it is possible to reduce the height of a resin protrusion that seals a bonding wire spanned from a head substrate of a thermal print head to a circuit substrate.

1 is a cross-sectional view of an embodiment of a thermal print head according to the present invention. 1 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. This embodiment is merely an example, and the present invention is not limited to this.

  FIG. 1 is a 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 in the present embodiment.

  The thermal print head 10 according to the present embodiment includes a head substrate 20, a heat radiating plate 30, and a circuit substrate 40. The head substrate 20 has a rectangular plate-shaped insulating substrate 22. The insulating substrate 22 is an electrically insulating flat plate in which a glass glaze layer 25 is deposited on the surface of a ceramic plate 21 such as alumina.

  On the surface of the insulating substrate 22, for example, a resistor layer 23 extending in the short side direction with a predetermined interval in the long side direction of the insulating substrate 22, and a metal wiring layer 28 formed on the surface of the resistor layer 23, Are stacked. In the metal wiring layer 28, a notch is formed in a part in the short side direction of the insulating substrate 22, and a portion of the resistor layer 23 that does not overlap with the metal wiring layer 28 becomes the heating resistor 26. The metal wiring layer 28 connected to the heating resistor 26 serves as an electrode for supplying current to the heating resistor. The row of the heat generating resistors 26 forms a heat generating region 24 extending in a strip shape along the long side on one surface of the insulating substrate 22. The direction in which the heat generating region 24 extends is called the main scanning direction. The insulating substrate 22, the heating resistor 26 and the metal wiring layer 28 are covered with a protective film 29. In the protective film 29, an opening exposing a part of the metal wiring layer 28 is formed.

  A drive circuit that generates heat from the heating resistor 26 is formed on the circuit board 40 by a driving IC 42, for example.

  The heat sink 30 is a plate formed of a metal such as aluminum. A heat radiating surface 55 and an adhesive surface 52 are formed on one surface of the heat radiating plate 30. The heat radiating surface 55 and the adhesive surface 52 are partitioned by a groove 53 extending in the main scanning direction.

  For example, silicone resin 62 is applied to heat radiation surface 55. A single double-sided tape 61 is affixed to the adhesive surface 52. The head substrate 20 and the circuit board 40 are placed so as to face the same surface of the heat dissipation plate 30. The long side in the vicinity where the opening for exposing a part of the metal wiring layer 28 of the head substrate 20 is arranged and the long side in the vicinity where the driving IC 42 of the circuit board 40 is arranged are arranged so as to face each other. Yes. More specifically, the head substrate 20 is placed on the heat dissipation plate 30 across the heat dissipation surface 55 and the adhesive surface 52. The circuit board 40 is placed on the adhesive surface 52.

  Therefore, the silicone resin 62 is interposed between the lower surface of the heat generating region 24 of the head substrate 20 and the heat radiating plate 30. The double-sided tape 61 extends between the circuit board 40 and the heat sink 30 from between the head substrate 20 and the heat sink 30. The head substrate 20 and the circuit board 40 are fixed to the heat sink 30 with a double-sided tape 61. The silicone resin 62 also contributes to some extent to the fixation between the head substrate 20 and the heat sink 30.

  The driving IC 42 and the metal wiring layer 28 are electrically connected by, for example, a bonding wire 44 through an opening formed in the protective film. The driving IC 42 and the wiring pattern formed on the circuit board 40 are also electrically connected by, for example, bonding wires 44. The driving IC 42 and the bonding wire 44 are sealed with a sealing resin 48, for example. A control signal and driving power for forming a predetermined heat generation pattern in the heat generation region 24 are input to the circuit board 40 via a connector, for example.

  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 of the present embodiment has a platen roller 58 formed in a cylindrical shape with a material having a predetermined elasticity. The platen roller 58 has a shaft 59 on a straight line parallel to the main scanning direction in which the heat generating region 24 extends. Further, the side surface of the platen roller 58 is disposed so as to be in contact with the heat generating region 24, and is provided to be rotatable around a shaft 59.

  Due to the rotation of the platen roller 58, the printing medium 57 such as thermal paper inserted between the platen roller 58 and the heat generating area 24 moves in the sub-scanning direction perpendicular to the main scanning direction. While the printing medium 57 is pressed against the heat generation area 24 by the platen roller 58, the printing medium 57 is moved in the sub-scanning direction, and the heat generation pattern of the heat generation area 24 is changed along with the movement of the printing medium 57, so that a desired An image is formed on the medium.

  Next, a method for manufacturing the thermal print head will be described.

  First, the head substrate 20, the heat sink 30, and the circuit board 40 are manufactured. Next, a thermosetting silicone resin 62 is applied to the heat radiating surface 55 of the heat radiating plate 30. In addition, a double-sided tape 61 is attached to the adhesive surface 52 of the heat sink 30.

  Thereafter, the head substrate 20 is placed on the heat radiating plate 30 so that the back side of the heat generating region 24 of the head substrate 20 faces the heat radiating surface 55, and the back surface on the side where the connection portion with the circuit board 40 is provided faces the adhesive surface 52. Placed on. Next, a silicone resin 49 is applied to the side surface of the head substrate 20 facing the circuit board 40.

  After the silicone resin 49 is applied to the side surface of the head substrate 20, the circuit board 40 is placed on the heat sink 30 so that the back surface faces the adhesive surface 52. At this time, the long side of the circuit board 40 in the vicinity where the driving IC 42 is disposed is pressed so as to face the long side of the head substrate 20. Thus, after temporarily fixing the head substrate 20 and the circuit board 40 to the heat sink 30, the atmosphere is reduced to about 0.2 atm, for example. Thereby, the silicone resins 49 and 62 are defoamed. Thereafter, the entire head substrate 20, circuit substrate 40, and heat sink 30 are heated to about 200 ° C. to cure the silicone resins 49 and 62.

  After fixing the head substrate 20 and the circuit board 40 to the heat sink 30 in this way, the driving IC 42 is attached to the circuit board 40. Further, the bonding wires 44 connect the driving IC 42 and the head substrate 20 and the driving IC 42 and the terminals on the circuit board 40. After the wire bonding, the driving IC 42 and the bonding wire 44 are resin-sealed. Thereafter, the thermal print head 10 is completed by soldering components such as connectors.

  When the head substrate 20 and the circuit board 40 are disposed in direct contact with each other, it is inevitable that a gap is generated due to the unevenness of the side surface of the head substrate 20 and the side surface of the circuit substrate 40. When a resin to be sealed is applied after wire bonding, the resin does not flow into all the gaps because the viscosity of the resin is high. However, since the sealing resin flows into a part of the gap, a part of the gap becomes a bubble surrounded by the resin before curing.

  If bubbles exist in the resin before curing, the bubbles grow and escape to the surface due to heating during curing, so that unevenness may occur on the surface after curing. For this reason, it is necessary to apply the resin to some extent so that the bonding wire 44 is not exposed even if the surface of the cured sealing resin is uneven.

  It is effective to form a groove in the heat radiating plate 30 as an escape path for such bubbles and let the gas in the bubbles escape to the outside of the thermal print head 10 via the groove. However, since not all of the gaps between the side surface of the head substrate 20 and the side surface of the circuit board 40 communicate with this groove, it is difficult to eliminate bubbles in the sealing resin.

  On the other hand, in the present embodiment, the abutting portion between the head substrate 20 and the circuit substrate 40 is filled with the silicone resin 49. By pressing the circuit board 40 against the head substrate 20 before the silicone resin 49 is cured, the gap between the side surface of the head substrate 20 and the side surface of the circuit board 40 is filled with the silicone resin 49. This state is maintained even when the silicone resin 49 is cured.

  As a result, when the bonding wire 44 is sealed with the sealing resin 48, the occurrence of irregularities on the surface of the sealing resin 48 due to bubble swelling is suppressed. For this reason, the application amount of the sealing resin 48 for sealing the bonding wire 44 can be reduced, and the protruding amount of the sealing resin 48 from the head substrate 20 and the circuit substrate 40 can be reduced. For this reason, possibility that the conveyance of the to-be-printed body 57 will be reduced becomes small.

  Further, it is not necessary to form a groove as a gas escape path from the sealing resin 48 for sealing in the heat radiating plate 30. For this reason, the molding cost of the heat sink 30 is reduced. Along with this, the head substrate 20 and the circuit board 40 can be fixed to the heat sink 30 with a single double-sided tape 61, so that the time and cost required for assembly are reduced.

DESCRIPTION OF SYMBOLS 10 ... Thermal print head, 20 ... Head substrate, 21 ... Ceramic board, 22 ... Insulating substrate, 23 ... Resistor layer, 24 ... Heat generating area, 25 ... Glaze layer, 26 ... Heat generating resistor, 28 ... Metal wiring layer, 29 DESCRIPTION OF SYMBOLS ... Protective film, 30 ... Heat sink, 40 ... Circuit board, 42 ... Driving IC, 44 ... Bonding wire, 48 ... Sealing resin, 49 ... Silicone resin, 52 ... Adhesion surface, 53 ... Groove, 55 ... Heat dissipation surface, 57 ... Printed body, 58 ... Platen roller, 59 ... Shaft, 61 ... Double-sided tape, 62 ... Silicone resin

Claims (4)

A heat sink,
A rectangular head substrate placed on the heat sink with heaters arranged on the surface of the insulating substrate at intervals and electrodes connected to both ends of each heater;
A circuit board placed on the heat sink so that the long side of the head substrate faces the circuit board;
A plurality of bonding wires that are bridged between the head substrate and the circuit board and electrically connect each of the heaters and the circuit board;
A silicone-based resin body filled in a position where the long sides of the head substrate and the circuit board face each other;
An epoxy-based resin sealing body that extends in a strip shape across the head substrate and the circuit substrate and seals the bonding wire;
A thermal print head comprising:   And a double-sided tape for fixing the head substrate and the circuit board to the heat radiating plate so as to extend from between the head substrate and the heat radiating plate between the circuit board and the heat radiating plate. Item 2. The thermal print head according to Item 1.   The heat radiating plate is formed with a heat radiating surface and an adhesive surface partitioned by a groove extending in the long side direction on one main surface, and the back surface of the area where the heaters are arranged faces the heat radiating surface of the head substrate. The thermal print head according to claim 2, wherein the thermal print head is disposed across the heat dissipation surface and the adhesion surface, and the circuit board is disposed on the adhesion surface. Forming a plurality of heaters arranged on the surface of the rectangular insulating substrate at intervals in the longitudinal direction of the insulating substrate and electrodes connected to both ends of the heater to obtain a head substrate;
Forming a circuit board on which a drive circuit for driving the heater is mounted;
A step of manufacturing a rectangular plate-like heat sink;
Placing the head substrate on the heat sink;
Applying a silicone-based resin to the side surface of the long side farther from the heater of the head substrate;
Placing the circuit board on the heat sink while pressing the circuit board against the side surface of the head substrate on which the silicone resin is applied; and
Spanning a bonding wire between the head substrate and the circuit board;
Sealing the bonding wire with resin;
A method of manufacturing a thermal print head, comprising:

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