CN109484036B

CN109484036B - Thermal head

Info

Publication number: CN109484036B
Application number: CN201811063857.2A
Authority: CN
Inventors: 高田直希; 山地范男
Original assignee: Aoi Electronics Co Ltd
Current assignee: Aoi Electronics Co Ltd
Priority date: 2017-09-13
Filing date: 2018-09-12
Publication date: 2021-02-09
Anticipated expiration: 2038-09-12
Also published as: JP2019051628A; CN109484036A; JP6781125B2

Abstract

The invention provides a thermal head with improved adhesive strength of sealing resin. A thermal head is provided with: a common electrode formed on the insulating substrate and applying a driving voltage; a plurality of independent electrodes formed on the insulating substrate for each micro region of the heating element and applying a driving voltage to each micro region; a drive IC connected to the insulating substrate and provided on the circuit substrate, the drive IC controlling currents flowing through the individual electrodes; a protective film covering a protective region including the common electrode and the individual electrode; and a sealing resin covering the wires wired to the driving ICs and the driving ICs across the insulating substrate and the circuit substrate, connection pads connected to the driving ICs through the wires are provided along edges of the insulating substrate on the plurality of individual electrodes, and the protection region includes: and a region which is between one end of the common electrode and the other end of the common electrode and which is in contact with at least a part of an edge of the insulating substrate, of the regions covered with the sealing resin.

Description

Thermal head

Technical Field

The present invention relates to a thermal head.

Background

Conventionally, a thermal head in which a bonding wire is sealed with a sealing resin is known (for example, patent document 1).

Patent document 1: japanese patent laid-open No. 2008-68405.

Disclosure of Invention

In the prior art, the problem of insufficient adhesive strength of the sealing resin exists.

According to the 1 st aspect of the present invention, a thermal head includes: a common electrode formed on the insulating substrate and applying a driving voltage; a plurality of independent electrodes formed on the insulating substrate in accordance with micro regions of the heating element, and applying the driving voltage to each of the micro regions; a driver IC connected to the insulating substrate, provided on the circuit substrate, and configured to control currents flowing through the plurality of independent electrodes, respectively; a protective film covering a protective region including the common electrode and the individual electrode; and a sealing resin that spans the insulating substrate and the circuit substrate and covers wires connected to the driving ICs and the driving ICs, connection pads connected to the driving ICs through the wires are provided along an edge of the insulating substrate on the plurality of individual electrodes, and the protection region includes: a region between one end of the common electrode and the other end of the common electrode and in contact with at least a part of the edge of the insulating substrate, among the regions covered with the sealing resin.

According to the present invention, the adhesive strength of the sealing resin can be improved.

Drawings

Fig. 1 is a plan view showing a structure of a thermal head according to embodiment 1.

Fig. 2 is a view schematically showing a cross section of line I-I of fig. 1.

Fig. 3 is a plan view showing a structure of a thermal head according to embodiment 2.

Fig. 4 is a view schematically showing a cross section of line I-I of fig. 3.

Fig. 5 is a plan view showing a structure of a thermal head according to a modification.

Fig. 6 is a plan view showing a structure of a thermal head according to a modification.

Description of the reference numerals

100 … thermal head, 1 … heating element, 2 … common electrode, 3 … independent electrode, 4 … insulating substrate, 6a, 6b … driver IC, 7a, 7b, 7c … wire, 8 … sealing resin, 9 … circuit substrate, 12 … protection film.

Detailed Description

(embodiment 1)

Fig. 1 is a plan view showing a structure of a thermal head according to embodiment 1 of the present invention. Fig. 2 is a view schematically showing a cross section of line I-I of fig. 1. The thermal head 100 includes an insulating substrate 4 and a circuit board 9 fixed to a support plate 5. The insulating substrate 4 and the circuit board 9 are fixed to the support plate 5 by the adhesive layer 11.

The insulating substrate 4 is formed by an insulator such as ceramic. In the present embodiment, the insulating substrate 4 is configured such that the glaze layer 4b is provided on the ceramic substrate 4 a. On the insulating substrate 4, unnecessary portions of a conductor such as gold are removed by etching using photolithography, thereby forming the common electrode base 21 and the plurality of individual electrodes 3. A strip-shaped heating element 1 is formed, for example, by thick-film printing, above the common electrode 2 and the plurality of individual electrodes 3 (upward in the paper plane of fig. 1). A part of the entire area of the insulating substrate 4 (described later in detail) is covered with a protective film 12 shown by oblique lines in fig. 1 and 2. The protective film 12 is made of glass or the like, for example.

The circuit board 9, which is a printed wiring board or the like, is provided with a driver IC6a, a driver IC6b, and a connection terminal 10. The driver ICs 6a and 6b are driver ICs that are connected to the individual electrodes 3 and control the current flowing through each heating element 1 to be supplied or not supplied. In the following description, the driver IC6a and the driver IC6b are collectively referred to as a driver IC 6. Although the driver IC6 has input electrode pads for actually receiving signals from the connection terminals 10 and controlling the driver IC6, the input electrode pads are not shown in the figure.

The connection terminal 10 is a connection portion for connecting the thermal head 100 to an external apparatus that performs print control or the like. A plurality of connection terminals 10 are arranged in a row at the lower portion of the circuit board 9 in fig. 1, that is, at the edge of the circuit board 9 opposite to the insulating substrate 4 side. One end of each individual electrode 3 is connected to the driver IC6 through an electric wire 7 c. The wire 7c is a metal wire such as a gold wire that electrically connects the individual electrode 3 and the driver IC 6.

The common electrode 2 has a common electrode base 21 and a plurality of common electrode extensions 20. The common electrode base 21 is formed to surround the heating element 1 along 3 sides except for 1 side facing the circuit substrate 9 among 4 sides of the rectangular insulating substrate 4. The plurality of common electrode extending portions 20 extend in the sub-scanning direction 42 (vertical direction on the paper surface of fig. 1) from one region of the common electrode base portion 21 extending parallel to the heating element 1 in fig. 1. As described later, the extending direction of the heating element 1 is the main scanning direction.

One end 21a of the common electrode base 21 is electrically connected to a wiring pattern 13a provided on the circuit substrate 9 via a plurality of wires 7 a. The wiring pattern 13a is electrically connected to the connection terminal 10. The other end 21b of the common electrode base 21 is electrically connected to a wiring pattern 13b provided on the circuit substrate 9 via a plurality of wires 7 b. The wiring pattern 13b is electrically connected to the other side of the connection terminal 10.

Each of the individual electrodes 3 has a connection portion 32, an individual electrode extension portion 30, and a connection pad 31. The individual electrode extension 30 is positioned between a pair of common electrode extensions 20 of the common electrode 2 and extends along the sub-scanning direction 42. The connection portion 32 extends from an end of the individual electrode extension portion 30 in the sub-scanning direction 42.

The connection pad 31 is provided at the other end of the connection portion 32, that is, at the end of the connection portion 32 on the opposite side to the individual electrode extension portion 30. That is, the individual electrode extension 30 is provided at one end of the connection portion 32, and the connection pad 31 is provided at the other end. In other words, the individual electrode extensions 30 and the connection pads 31 are connected by the connection portions 32.

The plurality of common electrode extensions 20 and the plurality of individual electrode extensions 30 are formed to alternately and oppositely engage. The heating element 1 is formed so as to extend across the plurality of common electrode extending portions 20 and the plurality of individual electrode extending portions 30, in other words, so as to cross, and extends in a main scanning direction 41 (left-right direction of the paper surface in fig. 1) which is an arrangement direction of the common electrode extending portions 20 and the individual electrode extending portions 30.

The plurality of connection pads 31 are arranged in a row at a predetermined pitch along an edge portion 4x (fig. 1 and 2) of the insulating substrate 4 on the circuit board 9 side, that is, along the main scanning direction 41. The driver IC6 has an elongated rectangular shape (an elongated quadrangular prism as a whole) in a plan view, and is soldered to the circuit board 9 with its longitudinal direction aligned in the extending direction of the edge portion 4x on the circuit board 9 side. A plurality of IC electrode pads 60 are formed on the upper surface of the driver IC6 along the edge portion facing the insulating substrate 4, that is, along the main scanning direction 41. The plurality of connection pads 31 are arranged at the same interval as the plurality of IC electrode pads 60. The 1 connection pad 31 corresponds to the 1 IC electrode pad 60. Each connection pad 31 is electrically connected to the corresponding IC electrode pad 60 through the wire 7 c.

The driver IC6 controls the current flowing from the common electrode 2 to each individual electrode 3 via the heating element 1. Thereby, a current flows in a minute region of the heating element 1 between the portions formed so that the common electrode extension portions 20 and the individual electrode extension portions 30 are alternately and oppositely engaged, and heat is generated at the portion. Printing is performed by supplying this heat to a printing medium such as thermal paper.

In addition, in fig. 1, the individual electrodes 3 are shown in a simplified diagram less than the actual number for convenience of drawing. Therefore, the number of common electrode extension portions 20, the number of individual electrode extension portions 30, the number of connection pads 31, the number of IC electrode pads 60, and the like are also shown less than the actual number. Although the connection pads 31 have the same pitch as the IC electrode pads 60, they are not necessarily arranged in the same row along the main scanning direction 41, and may be 2 rows or 3 rows.

A part of the area of the insulating substrate 4 is covered with a protective film 12 indicated by oblique lines in fig. 1. The region protected by the protective film 12 includes the heating element 1, most of the common electrode extension portion 20 including at least the common electrode 2, and the portion of the individual electrode 3 other than the connection pad 31 (i.e., most of the individual electrode extension portion 30 and the connection portion 32). In other words, these components are protected by the protective film 12.

The sealing resin 8 is formed by curing an epoxy resin, and thereby seals the boundary region between the insulating substrate 4 and the circuit board 9, including the driver IC6, the electric wire 7a, the electric wire 7b, and the electric wire 7c, in the planar state in the ranges up to the positions of both edges of the insulating substrate 4 and the circuit board 9 in the orthogonal direction, and the heating element 1. The sealing resin 8 prevents the

electric wires

7a, 7b, 7c, and the like from being broken or detached due to contact or collision from the outside. The sealing resin 8 has the following properties: it is difficult to fix the surfaces of the insulating substrate 4 and the common electrode 2 and the individual electrodes 3 formed on the insulating substrate 4, and it is easier to fix the surfaces of the protective film 12 than they are. In addition to the suitability of the structural materials, the surface roughness Ra of each of the insulating substrate 4, the common electrode 2, the individual electrode 3, and the protective film 12 is approximately 0.025 μm, and 0.079 μm, and the surface roughness Ra of the protective film 12 is 3 times or more larger than that of the insulating substrate 4, the common electrode 2, and the individual electrode 3. As a result, it is found that the protective film 12 is more easily fixed even by the anchor effect.

For example, a Flexible Printed Cable (FPC) is connected to the connection terminal 10 by solder or the like. The connection of the connection terminal 10 and the FPC is performed by applying heat to the FPC using a heater or the like to melt solder or the like, for example. At this time, heat is transferred to the insulating substrate 4, the circuit board 9, the sealing resin 8, and the like, and these portions expand. The insulating substrate 4, the circuit substrate 9, the sealing resin 8, and the like have different thermal expansion coefficients, and therefore the sealing resin 8 may be detached from the insulating substrate 4 and the circuit substrate 9 by heat.

In the present embodiment, the protective film 12 for protecting the heating element 1, the common electrode 2, and the individual electrode 3 is extended as far as possible to the edge portion 4x of the insulating substrate 4 on the circuit board 9 side. Specifically, in the following regions (1) to (3), the protective film 12 is extended from a line 12P (a region line of the conventional protective film 12) indicated by a broken line in fig. 1 to the edge portion 4 x.

(1) A region R1 between the end portion 21a of the common electrode 2 and the plurality of connection pads 31 corresponding to the driver IC6 a.

(2) An area R2 between the end portion 21b of the common electrode 2 and the plurality of connection pads 31 corresponding to the driver IC6 b.

(3) A region R3 between the plurality of connection pads 31 corresponding to the driver IC6a and the plurality of connection pads 31 corresponding to the driver IC6 b.

These regions R1 to R3 are all located between the one end portion 21a of the common electrode 2 and the other end portion 21b of the common electrode 2 and are in contact with the edge portion 4x of the insulating substrate 4.

In this way, since the area of contact between the protective film 12 and the sealing resin 8 is as large as possible, the sealing resin 8 is more reliably fixed and is less likely to be detached by heat.

With time, moisture in the air may gradually permeate from the boundary portion between the insulating substrate 4 and the circuit substrate 9. In addition, if foreign matter is present in the contact surface between the sealing resin 8 and the adhesive surface, the foreign matter absorbs moisture and expands, which hinders adhesion of the sealing resin 8, and the sealing resin 8 may be detached from the insulating substrate 4 and the circuit substrate 9.

In the present embodiment, as described above, the protective film 12 extends to the edge portion 4x in the regions R1 to R3 defined by the surface of the insulating substrate 4 between the plurality of connection pads 31 corresponding to the

end portions

21a, 21b of the common electrode 2 and the driver ICs 6a, 6 b. In this way, since the area of the protective film 12 in contact with the sealing resin 8 is increased as much as possible, the sealing resin 8 is more reliably fixed, and it becomes difficult to detach due to moisture absorption.

According to the above embodiment, the following operational effects can be obtained.

(1) The sealing resin 8 covers the electric wire 7c wired to the driver IC6 and the driver IC6 across the insulating substrate 4 and the circuit substrate 9. The protective film 12 covers the common electrode 2 and the individual electrodes 3, and covers a region which is located between one end portion 21a of the common electrode 2 and the other end portion 21b of the common electrode 2 and is in contact with at least a part of the edge portion 4x of the insulating substrate 4, of the region covered with the sealing resin 8. In this way, the adhesive strength of the sealing resin 8 can be further increased, and the possibility of detachment of the sealing resin 8 due to heat or moisture absorption can be reduced.

(2) The range covered with the sealing resin 8 is a range of the insulating substrate 4, the circuit substrate 9, and both edge portions of the heating element 1 in the right angle direction on the plane, and does not extend to the support plate 5, so that the application area of the sealing resin 8 is not required on the support plate 5, and the length of the thermal head 100 in the main scanning direction 41 can be shortened and the size can be reduced.

(embodiment 2)

Fig. 3 is a plan view showing a structure of a thermal head according to embodiment 2 of the present invention. Fig. 4 is a view schematically showing a cross section of line I-I of fig. 3. Differences between the thermal head 100 according to the present embodiment and the thermal head 100 according to embodiment 1 will be described below.

The thermal head 100 of the present embodiment shown in fig. 3 and 4 has a larger area than the protective film 12 of embodiment 1. Specifically, the protective film 12 covers the edge portion 4x of the insulating substrate 4 on the circuit board 9 side. That is, the protective film 12 covers the region R4 below the

electric wires

7a, 7b, 7 c. The region R4 is located between the one end portion 21a of the common electrode 2 and the other end portion 21b of the common electrode 2 and contacts the edge portion 4x of the insulating substrate 4.

As described above, in the thermal head 100 according to the present embodiment, since the range in which the protective film 12 is in contact with the sealing resin 8 is increased, the adhesive strength of the sealing resin 8 is higher than that of embodiment 1.

The following modifications are also within the scope of the present invention, and one or more modifications may be combined with the above-described embodiment.

(modification 1)

The range covered by the protective film 12 may be different from the above embodiments.

Fig. 5 is a plan view showing a structure of a thermal head 100 according to a modification. The thermal head 100 shown in fig. 5 does not cover the regions R1 to R3 shown in fig. 1, but covers the edge portion 4x on the circuit substrate 9 side of the insulating substrate 4, i.e., the region R4 shown in fig. 3. The thermal head 100 thus configured also has higher adhesive strength than the conventional sealing resin 8.

Fig. 6 is a plan view showing a structure of a thermal head 100 according to a modification. With the thermal head 100 shown in fig. 6, the arrangement pitch of the IC electrode pads 60 is wider than that of the above embodiments. Therefore, the arrangement pitch of the connection pads 31 of the individual electrodes 3 also becomes wider than that of the above embodiments. In this case, since the areas indicated as the regions R1 to R3 in fig. 1 are small, there is no sufficient space for extending the protective film 12.

In this case, the protective film 12 hardly covers the regions R1 to R3, but can cover the region R4 of the edge portion 4x on the circuit board 9 side of the insulating substrate 4. The thermal head 100 thus configured also has higher adhesive strength than the conventional sealing resin 8.

In addition, in fig. 1, the same effect can be achieved even in a structure in which the protective film 12 covers only one of the regions R1 to R3, or only 2 of the regions R1 to R3. As described above, the scope of the present invention includes various modes capable of improving the adhesion as compared with the conventional one.

(modification 2)

The number of driver ICs 6 may be other than 2. For example, only 1 driver IC6 may be provided, or 3 or more driver ICs 6 may be used. When there are 3 or more driver ICs 6, any region may be covered with the protective film 12 in the region between the driver ICs 6. Even in the case of such an arrangement, the same effects as those of the above-described embodiment can be obtained.

While various embodiments and modifications have been described above, the present invention is not limited to these embodiments. Other modes that can be conceived within the scope of the technical idea of the present invention are also included in the scope of the present invention.

Claims

1. A thermal head is characterized by comprising:

a common electrode formed on the insulating substrate and applying a driving voltage;

a plurality of independent electrodes formed on the insulating substrate for each micro region of the heating element, and applying the driving voltage to each micro region;

a driver IC connected to the insulating substrate, provided on the circuit substrate, and configured to control currents flowing through the plurality of individual electrodes, respectively;

a protective film covering the protective region; and

a sealing resin covering the wires wired to the driver ICs and the driver ICs across the insulating substrate and the circuit substrate,

on the plurality of individual electrodes, connection pads connected to the driving ICs by the wires are provided along an edge of the insulating substrate,

the protection region includes at least a portion of the common electrode extension of the common electrode and a portion of the individual electrode other than the connection pad,

the protection area comprises the following areas: a region between one end of the common electrode and the other end of the common electrode and in contact with at least a part of the edge of the insulating substrate among the regions covered with the sealing resin,

the sealing resin is more easily fixed to the surface of the protective film than to the surface of the insulating substrate, the surface of the common electrode, and the surface of the individual electrode.

2. A thermal head according to claim 1,

the protection region includes a region of the insulating substrate extending between one end of the common electrode and the plurality of connection pads.

3. The thermal head according to claim 1 or 2,

the protection region includes a region of the insulating substrate extending between a portion of the plurality of connection pads and another portion of the plurality of connection pads.

4. The thermal head according to claim 1 or 2,

the protection region includes a region of the insulating substrate extending between an end of the common electrode and the edge.

5. The thermal head according to claim 1 or 2,

the protection region includes a region of the insulating substrate extending between the plurality of connection pads and the edge.

6. The thermal head according to claim 1 or 2,

the sealing resin also seals wires that electrically connect both ends of the common electrode with a wiring pattern provided on the circuit substrate.