JPH06286187A - Thermal head - Google Patents

Abstract

PURPOSE:To provide a thermal head with construction that enables the density of a heating element to be high and, moveover, is manufactured readily, CONSTITUTION:On a substrate 3 having a heat resistor 1 thereon, a circuit substrate 4 is fixed that mounts driving ICs 2 for electrification of the heat resistor 1. The circuit substrate 1 has cut-in parts 4a in the arrangement direction of the heat resistor 1, and the driving ICs 2 are mounted on the upper side surface of the cut-in parts 4a. The driving ICs 2 and a lead electrode 6 formed on the heat resistor-formed substrate 3 are connected electrically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used for thermal recording or thermal transfer recording.

[0002]

2. Description of the Related Art Conventional flat plate type thermal heads include a separate type shown in FIG. 3 and an integrated type shown in FIG. First, the separation type structure of FIG. 3 will be described. FIG. 3A is a side view thereof and FIG. 3B is a plan view of the separation type structure. The heat generating element 1 is formed on the surface of the heat generating element array substrate 3 made of ceramics such as alumina, and the driving IC 2 for energizing the heat generating element 1 is separate from the substrate 3 and is a circuit board for external connection. Four
It has a structure in which the substrate 3 and the circuit board 4 are attached to a heat sink 5 made of an aluminum plate or the like by adhesion or by using an appropriate fixing tool such as a screw or a rivet. The heating elements 1 are linearly arranged in a direction perpendicular to the paper feeding direction to form a heating element row, and each heating element 1 generates heat when energized. The energization of each heating element 1 is controlled by the driving IC 2. When the energized heating element 1 generates heat, a recording medium such as a card or a sheet that slides and passes over the row of heating elements is formed. Thermal recording or thermal transfer recording is performed. Therefore, in order to perform high density recording, it is necessary to increase the density of the heating elements 1 forming the heating element row.

As shown in FIG. 3B, a lead electrode 6 for wiring for energizing the heating element 1 is formed on the surface of the substrate 3, and each lead electrode 6 is formed. The end portion on the side opposite to the heating element 1 is connected to the output terminal 2a of the driving IC 2 by a wire bond 8. The input terminal 2b of the driving IC 2 is connected to a conductor formed on the circuit board 4 by a wire bond 8 and is connected to the outside via a connector 9.

In such a conventional thermal head, there are technical restrictions on the mounting pitch of the driving IC 2 on the circuit board 4 and the pitch between the wire bonds 8 connecting the lead electrode 6 and the driving IC 2. Yes, in order to keep the pitch below a certain value (for example, it is difficult to keep the pitch between wires below 75 microns), the number of drive ICs 2 that can be mounted on the thermal head with the specified width and the drive of the specified size The number and pitch of the output terminals 2a provided in the IC 2 for use were limited. Therefore, the density of the heating element 1 is also limited, and when the driving IC 2 is placed horizontally (the longitudinal direction of the IC 2 is substantially parallel to the heating element row direction), up to about 300 dots per inch (300 DPI) can be achieved. Although possible, it has been difficult to achieve high densities of 400 DPI.

On the other hand, a side view of FIG. 4A and a side view of FIG.
The thermal head having an integrated structure shown in the plan view has a structure in which the heating element 1 and the driving IC 2 are both provided on the substrate 3 in addition to the thermal head having the separate structure described above. In the thermal head of the present example, a vertical driving IC 2 is mounted on the heating-element-side lead electrode 6a and the input-side lead electrode 6b formed on the upper surface of the substrate 3 (the longitudinal direction of the IC2 generates heat). The drive IC 2 is mounted so as to be substantially perpendicular to the body column direction), and the output terminal 2a and the input terminal 2 of the driving IC 2 are mounted.
b is the lead electrode 6a and the lead electrode 6b, respectively.
And a wire bond 8 to connect the output side wiring and the input side wiring of the driving IC 2.

In such an integrated structure, the driving IC 2
Is mounted vertically, the drive I on the substrate 3 is mounted.
Since the mounting pitch of C2 can be made small, the number of driving ICs 2 that can be mounted on the thermal head having the specified width can be increased, and the pitch of the heating element 1 due to the pitch between the wire bonds 8 is not limited, so that heat generation can be prevented. It is advantageous for increasing the body density. However, if the mounting pitch of the driving IC 2 on the thermal head is further reduced in order to achieve higher density, the heating element side lead electrode 6a and the input side lead electrode 6b are overlapped. If the lead electrode 6a is not connected, the lead electrode 6a cannot be wired, and the lead electrode 6a and the input side lead electrode 6b are prevented from being short-circuited.
After formation, a multi-layer structure in which an insulating layer is formed to cover a part of the lead electrode 6a and then the input side lead electrode 6b is formed is required, which complicates the manufacturing process. was there.

[0007] Further, the above-mentioned separated type and integral type of server
In the round head, it may be possible to increase the density by increasing the number of the driving ICs mounted on the thermal head having the specified width by changing the number of the driving ICs mounted from one row to a plurality of rows. And the lead electrode for wiring the driving IC in the front row must have a multilayer structure.
There is a problem in that the manufacturing process such as formation of the lead electrode pattern and formation of an insulating layer between the lead electrodes becomes complicated.

In view of the above problems, it is an object of the present invention to realize a thermal head which can increase the density of heating elements and is easy to manufacture.

[0009]

In order to achieve the above object, the present invention fixes a circuit board on which a driving IC for energizing the heating element is mounted on a substrate on which the heating element is formed,
The circuit board has cutouts or openings in the direction of arrangement of the heating elements, and the vertical driving IC is mounted on a side surface of the cutouts or openings on the circuit board. The driving IC and the lead electrode formed on the heating element forming substrate are electrically connected.

[0010]

According to the present invention, as described above, the circuit board on which the driving IC is mounted is fixed to the upper surface of the lead electrode formed on the board, and the notch or the opening formed on the circuit board is used. By electrically connecting the drive IC and the lead electrode, the lead electrode serves as an output side wiring of the drive IC, and the circuit board serves as the lead electrode and the circuit board. It serves as an insulating layer between the input side wiring and the built-in conductor pattern.

[0011]

1 (A) is a plan view of an embodiment of a thermal head according to the present invention, FIG. 1 (B) is a side view, FIG. 1 (C) is a partially enlarged view of the same (A), and FIG. [Fig. 4] is an enlarged cross-sectional view taken along line EE of the same (B). FIG. 2A is a plan view showing the state of the board 3 before the flexible cable board 4 as the external connection circuit board is fixed, and FIG. 2B is the flexible cable board 4 on which the driving IC 2 is mounted. Is a plan view, (C) is a cross-sectional view of the flexible cable substrate 4, and (D) is an IC2.
FIG. 6 is a plan view showing a connection structure between a conductor in the substrate 4 and the conductor in the substrate 4.

As shown in FIG. 2 (A), a lead electrode 6 for energizing the heating element 1 is formed on the upper surface of the heating element array forming substrate 3, and the lead electrode 6 of the lead electrode 6 is formed. The end portion 6c on the side opposite to the heating element 1 is arranged and formed at a position exposed from the cut portion 4a of the flexible cable substrate 4 fixed in a later step.

As shown in FIG. 2 (C), the flexible cable substrate 4 has a plurality of conductors 10 made of copper or the like integrally formed on the upper and lower surfaces of a flexible film 11 and has upper and lower surfaces. The conductors 10 are connected by through holes 12, and an insulating protection layer 14 made of a flexible resin such as polyimide resin is provided on the front and back surfaces of the substrate via an adhesive agent 13. Figure 2
As shown in (B), a plurality of cuts (or openings) 4a are formed in the substrate 4 in the arrangement direction of the heating elements 1, and one row or a line is formed on the surface of the side of the cuts 4a. A plurality of vertical driving ICs 2 are mounted (the figure shows the case of two rows). The driving IC 2 has a flexible cable substrate 4 so that the output terminal 2a is on the side of the cut portion 4a.
As shown in FIG. 2D, the input terminal 2b of the driving IC 2 is exposed by removing the upper insulating layer 4b (4d indicates a conductor exposed portion). It is connected to the conductor 10 by a wire bond 8.

The substrate 3 and the flexible cable substrate 4 are prepared in this way, and as shown in FIGS. 1A and 1B, the end portion 6c of the lead electrode 6 is cut into the cut portion. 4a
The substrate 3 and the flexible cable substrate 4 are fixed to each other with an adhesive 7 or a double-sided tape so as to be exposed from the end portion 6c exposed from the cut portion 4a and the driving IC 2
The output head 2a of FIG. 1 is connected by a wire bond 8 as shown in FIG. 1C, whereby the thermal head shown in FIG. 1A is manufactured.

In the above embodiment, the driving IC 2 is mounted on the flexible cable substrate 4 in advance, and the driving IC 2
Flexible cable with two input terminals 2b connected
The case where the flexible substrate 4 is fixed to the substrate 3 and then the output terminal 2a of the driving IC 2 is connected is shown. However, after the flexible cable substrate 4 is fixed to the substrate 3, the driving IC is
2 may be mounted to connect the input terminal 2b and the output terminal 2a.

Thus, the flexible cable substrate 4
By accommodating the input-side conductor 10 in the inside, without forming a conductor pattern of a multilayer structure on the heating element row forming substrate 3,
Since the vertically arranged driving ICs can be mounted in two rows, it is possible to increase the density of the heating elements 1. In addition, the flexible cable substrate 4 itself serves as an insulating layer, and it is not necessary to form a dedicated insulating layer between the conductor 10 on the input terminal 2b side and the lead electrode 6 on the output terminal 2a side, which improves productivity. improves.

In the above embodiment, the driving IC is used.
The flexible cable board 4 was used as the circuit board on which the conductor 2 and the conductor 10 are connected.
It is sufficient if the laminated structure allows insulation between the electrode 6 and
It does not necessarily have to be flexible.

[0018]

According to the present invention, the circuit board on which the driving IC is mounted has the conductor connected to the input terminal of the driving IC and the lead electrode connected to the output terminal of the driving IC. Since it serves as an insulating layer between them and it is not necessary to form an insulating layer on the heating element array forming substrate, the manufacturing process is simplified,
Productivity is improved.

According to the second aspect of the present invention, the number of the drive ICs mounted can be increased without being restricted by the pitch of the drive ICs mounted in the heating element row direction, so that high density can be easily achieved.

[Brief description of drawings]

1A is a plan view of an embodiment of a thermal head according to the present invention, FIG. 1B is a side view thereof, FIG. 1C is a partially enlarged view of FIG. 1A, and FIG. It is an EE partial expanded sectional view.

2A is a plan view showing a state of the circuit board before the circuit board is fixed, FIG. 2B is a plan view of a circuit board on which a driving IC is mounted, and FIG. 2C is a sectional view of the circuit board. (D) is a plan view showing a connection structure between an IC and a conductor in a substrate.

FIG. 3A is a side view showing an example of a conventional thermal head having a separation type structure, and FIG. 3B is a plan view thereof.

FIG. 4A is a side view showing an example of a conventional thermal head having an integrated structure, and FIG. 4B is a plan view thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating element 2 Driving IC 3 Heating element row formation substrate 4 Circuit board 4a Cut part 4b, 4c Insulating layer 4d Exposed part 5 Heat sink 6 Lead electrode 7 Adhesive 8 Wire bond 9 Connector 10 Conductor 11 Connection part

Claims (2)

[Claims] 1. A circuit board on which a driving IC for energizing the heating element is mounted, is fixed to a substrate on which a heating element made of an electric resistor is formed, and the circuit board has a cut portion or an opening portion for generating heat. A lead formed in the body arranging direction, the driving IC being mounted on the side surface of the notch or opening on the circuit board, and formed on the driving IC and the heating element forming substrate. A thermal head characterized by being electrically connected to the electrodes. 2. A thermal head according to claim 1, wherein the driving ICs are mounted in a plurality of rows.