JP3462083B2 - Thermal head - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head incorporated as a printer mechanism for video printers and facsimiles.

[0002]

2. Description of the Related Art In recent years, in order to perform thermal recording on a hard recording medium such as a plastic card which is difficult to bend, it has been attempted to make the surface of a thermal head in contact with the recording medium as flat as possible.

As such a conventional thermal head, a hole is provided in a ceramic substrate having a large number of heating resistors and a large number of conductive layers electrically connected to the heating resistors, and the holes are formed. There is known a structure in which a driver IC for controlling heat generation of a heat generating resistor is embedded in the section. According to such a thermal head, by embedding the driver IC in the hole of the substrate, there is no one that largely protrudes upward from the surface of the thermal head. Therefore, in a hard recording medium that is difficult to bend, such as a plastic card. Even when heat-sensitive recording is performed, a straight path is possible in which the recording medium is conveyed onto the heating resistor while maintaining a flat shape.

As shown in FIG. 5, a large number of output terminals 14a and 14b are arranged in two rows on the upper surface of the driver IC, and the conductive layer 12 on the upper surface of the substrate is connected to these output terminals 14 and 14b. By extending to the top, the conductive layer 12 and the corresponding output terminals 14a, 14b
And are individually electrically connected. Incidentally, the reason why the large number of output terminals 14a and 14b are arranged in two rows in this way is to correspond to the increase in recording density, and at this time, the output terminals 14b in the second row are arranged in the first row. The conductive layer 12 arranged so as to be located between the output terminals 14a of the columns and connected to the output terminals 14b extends between the output terminals of the first column and extends onto the corresponding output terminals 14b. Will be present.

[0005]

By the way, in the process of manufacturing the above-mentioned thermal head, it is necessary to inspect in advance whether the driver IC embedded in the hole of the substrate operates normally. In this inspection step, the operation of the driver IC is confirmed by actually contacting the probe terminals of the inspection device with the output terminals 14a and 14b of the driver IC and applying a predetermined electric signal. At this time, in order to make sure that the probe terminal of the inspection device is brought into contact with each output terminal 14a, 14b, the output terminal 1
It is preferable to form the diameters of 4a and 14b as large as possible. However, if the diameter of the output terminal 14a is made large, the distance between the output terminals forming the first row becomes short. Therefore, the line width of the conductive layer 12 passing therethrough must be made extremely thin. . For this reason, the conductive layer 12 is disconnected between the output terminals in the first row, or the conductive layer 12 comes into contact with another output terminal 14a, which causes a drawback that the productivity of the thermal head is significantly reduced. It was

[0006]

A thermal head according to the present invention has a hole in a substrate having a large number of heating resistors arranged in a straight line and a large number of conductive layers electrically connected to the heating resistors. In a thermal head in which a driver IC having a large number of output terminals is embedded in the hole and the conductive layer and the output terminals are electrically connected, a plurality of output terminals of the driver IC are arranged in a row. Are arranged so that the output terminals of the other row are located between the output terminals of the first row, and an insulating film having a tapered upper surface is interposed between the driver IC and the conductive layer. A through hole having a diameter smaller than that of the output terminal is provided in the insulating film, and one end of the conductive layer is further extended into the through hole through the insulating film. Further, the thermal head of the present invention is characterized in that the conductive layer on the substrate and the conductive layer in the through hole are collectively formed by the same process. Further, in the thermal head of the present invention, the surface roughness of the insulating film is 20 in terms of center line average roughness Ra.
It is characterized in that it is set within the range of 00 to 40,000Å.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings. 1 is a plan view of a thermal head according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the thermal head of FIG. 1, FIG. 3 is an enlarged view of a main part of FIG. 2, and FIG. 4 is an enlarged view of a main part of FIG. Yes, 1 is a substrate, 1a is a hole provided in the substrate, 3 is a heating resistor, 4b is a conductive layer, 5 is a driver IC, 5a,
Reference numeral 5b is an output terminal of the driver IC, 7 is an insulating film, and 7a is a through hole provided in the insulating film.

The substrate 1 functions as a support base material for supporting a partial glaze layer 2, a plurality of heating resistors 3 and conductive layers 4a to 4c, which will be described later, on its upper surface and has a thickness of 0.5 m.
It is formed in a long shape from an electrically insulating material such as alumina ceramics or glass having a thickness of m to 1.5 mm.

When the substrate 1 is made of, for example, alumina ceramics, a suitable raw material such as alumina, silica, or magnesia is mixed with an appropriate organic solvent or solvent to form a slurry, which is formed in a conventionally known doctor blade. Method is used to form a ceramic green sheet, and then the ceramic green sheet is punched into a predetermined shape and fired at a high temperature.

On the upper surface of the substrate 1, a partial glaze layer 2 having a mountain-shaped cross section, a plurality of heating resistors 3, and conductive layers 4a-4c having a predetermined pattern are respectively deposited. The partial glaze layer 2 is made of a low heat conductive material such as glass,
The substrate 1 is formed in a strip shape with a thickness of 20 μm to 200 μm in the length direction.

The partial glaze layer 2 has a large number of heating resistors 3 attached to the vicinity of the top thereof projected upward to effectively increase the pressing force (printing pressure) of the heating resistors 3 against the recording medium. The heat generated by these heat generating resistors 3 is accumulated and dissipated so as to have an appropriate temperature, whereby the thermal response characteristic of the thermal head is maintained well.

The heating resistor 3 is a partial glaze layer 2
Is deposited and arranged at a constant pitch near the top of the. Since each of the heating resistors 3 is made of an electric resistance material such as tantalum nitride, the conductive layers 4a and 4b described later are formed.
When an electric power is applied from the outside via Joule heat, Joule heat is generated, and heat is generated at a temperature necessary to form a print on a recording medium, for example, a temperature of 150 ° C to 250 ° C.

The conductive layers 4a to 4c are conductive layers 4 as a common electrode commonly connected to one end of the heating resistor 3.
a, the other end of the heating resistor 3 and a driver IC described later
Conductive layer 4b as an individual electrode for individually connecting the output terminals 5a and 5b of 5 and a conductive layer as a signal wiring connected to the input terminal of the driver IC 5 and led out to the vicinity of the rear edge of the substrate 1. 4c and. These conductive layers 4a to 4c are made of a metal such as aluminum, the conductive layers 4a and 4b serve to apply the power from the external power source to the heating resistor 3 described above, and the conductive layer 4c serves to print an image signal from the outside. It serves to supply electric power to the driver IC5.

The partial glaze layer 2 is formed by printing and applying a predetermined glass paste obtained by adding and mixing an appropriate organic solvent and a solvent to glass powder in a strip shape by conventionally known screen printing or the like. By baking at a temperature of about 1000 ° C. to 1200 ° C., it is deposited and formed in a strip shape on the upper surface of the substrate 1, and the heating resistor 3 and the conductive layers 4 a.
4c is deposited / formed to have a predetermined thickness and a predetermined pattern by adopting a conventionally known thin film forming technique, specifically, a sputtering method and a photolithography technique.

The substrate 1 is provided with a strip-shaped hole 1a which is substantially parallel to the partial glaze layer 2. The hole 1a is formed so as to penetrate through the substrate 1 in the thickness direction, and the driver IC 5 is embedded in the hole 1a so that the upper surface of the driver IC 5 does not significantly protrude from the surface of the thermal head. The medium can be conveyed onto the heating resistor 3 while maintaining the flat shape.

The hole 1a is formed so as to penetrate the substrate 1 by irradiating the upper surface of the substrate with laser light of a predetermined intensity and fusing the substrate 1 in the thickness direction.

A plurality of driver ICs 5 are embedded in the hole 1a in a line. Each of the driver ICs 5 is adhered and fixed to a predetermined position in the hole 1a by an adhesive 6 such as an epoxy resin, and a large number of outputs arranged in two rows are arranged on the upper surface of each driver IC 5. Logic circuits (not shown) such as terminals 5a and 5b, switching transistors, etc., passivation film 5
c, etc. are formed, between the output terminals of the first row (between 5a and 5a)
Is arranged such that the output terminal 5b of the second row is located at.

The driver IC 5 has a function of selectively causing Joule heat generation of the above-described many heating resistors 3, specifically, when a print signal from the outside is supplied to the driver IC 5 through the conductive layer 4c, A predetermined output is generated from the output terminals 5a and 5b by driving the above-mentioned logic circuit. By applying this output to the corresponding heating resistor 3 via the above-mentioned conductive layer 4b, the heating resistor 3 is generated. Is operated to selectively generate Joule heat based on the print signal.

Incidentally, such a driver IC 5 is manufactured by adopting a conventionally known semiconductor manufacturing technique,
Usually, a plurality of semiconductor wafers are simultaneously manufactured by dicing one semiconductor wafer.

The output terminal 5 of the driver IC 5
The electrical connection between the a and 5b and the conductive layer 4b is made by extending one end of the conductive layer 4b onto the corresponding output terminals 5a and 5b.

An insulating film 7 made of polyimide resin or the like is further interposed between the driver IC 5 and the extending portion of the conductive layer 4a with a thickness of about 2 μm to 20 μm. The insulating film 7 has through holes 7a and 7b having a diameter smaller than that of the output terminals 5a and 5b at positions corresponding to the respective output terminals 5a and 5b, and the inside of these through holes 7a and 7b is electrically conductive. One end of the layer 4b is electrically connected to the corresponding output terminal 5a, 5b.

The through holes 7a, 7b are formed with a small diameter of 30 .mu.m-60 .mu.m when the diameter of the output terminals 5a, 5b is 70 .mu.m-100 .mu.m, for example.
As a result, a space large enough to allow the conductive layer 4b to pass is secured between the through holes (7a-7a) provided on the output terminals 5a of the first column.

Therefore, it is not necessary to form a thin portion of the conductive layer 4b connected to the output terminal 5b of the second row,
It becomes possible to form the conductive layer 4b with a constant width in a good pattern without disconnection. And in this case,
Since the output terminals 5a and 5b can be formed to have a relatively large diameter, in the driver IC inspection process,
The probe terminal of the inspection device can be surely brought into contact with each output terminal 5a, 5b of the driver IC, and the operation check of the driver IC becomes easy. Therefore, it is possible to improve the productivity of the thermal head.

Since the conductive layer 4b is electrically connected to the output terminals 5a and 5b without being directly attached to the upper surface of the driver IC 5, "passage" is not formed in the passivation film 5c at the edge of the driver IC 5. Even in some cases, there is no short circuit between the conductive layer 4b and the logic circuit, and there is a "burr" at the edge of the driver IC5.
Even if the film is formed, the insulating film 7 is "burr".
Therefore, the conductive layer 4b is not broken, and the productivity of the thermal head is improved also in these points.

Further, in this case, when the conductive layer 4b and the like are patterned by the above-mentioned photolithography technique, even if the substrate 1 is immersed in the etching solution with the driver IC 5 buried in the hole 1a, the driver IC 5
Since the upper surface of is not covered with the insulating film 7 and the etching solution does not come into contact with the logic circuit through a film defect in the passivation film 5c, the corrosion of the logic circuit is surely prevented and the driver IC 5 is improved. Can be kept in good condition.

Further, in this case, the upper surface of the driver IC 5 is covered with the insulating film 7 except for the portions where the through holes 7a and 7b are provided, so that a hard recording medium such as a plastic card is placed on the surface of the thermal head. Even when a large amount of dust is caught between the recording medium and the driver IC 5 due to the action of static electricity or the like when it is conveyed along and printing, the insulating film 7 acts as a cushion, so that the pressing force of the dust is alleviated. This effectively prevents damage to the logic circuit due to the trapping of dust.

Further, if the periphery of the hole 1a of the substrate 1 is covered with a part of the insulating film 7, the hole 1a can be formed.
Hole 1a when forming by melting with laser light
Even if "chipping" occurs in the peripheral portion of the conductive layer 4b, since this portion is well covered with the insulating film 7, the conductive layer 4b
Etc. can be formed as a good continuous film from the upper surface of the substrate 1 to the upper surface of the insulating film 7. Therefore, it is preferable to cover the periphery of the hole 1a of the substrate 1 with a part of the insulating film 7.

Furthermore, if the upper surface of the insulating layer 7 is formed so as to have a gentle taper shape, patterning of the conductive layer 4b and the like deposited thereon can be performed very well and easily. Therefore, the productivity of the thermal head will be further improved. Therefore, it is preferable that the upper surface of the insulating layer 7 is formed so as to have a gentle tapered shape.

Furthermore, by arranging the upper surface of the insulating film 7 at a height substantially equal to that of the partial glaze layer 2 (within ± 10 μm), when the conductive layer 4b is patterned by the photolithography technique, the heating resistor 3 is formed. Since exposure conditions can be made substantially equal in the vicinity and in the vicinity of the output terminals 5a and 5b of the driver IC 5, fine processing of the conductive layer 4b and the like becomes easy. Therefore, it is preferable that the upper surface of the insulating film 7 is located at substantially the same height as the partial glaze layer 2.

The insulating film 7 is made of, for example, a precursor of epoxy resin, polyimide resin, polyetheramide or the like in a liquid state, and a spin coater is applied to a predetermined area on the upper surface of the substrate 1 in which the driver IC 5 is embedded. It is formed by applying it and curing it by applying heat or irradiating light (infrared ray), and then adopting a well-known photolithography technique and providing through holes 7a and 7b at predetermined positions. It At this time, if the insulating film 7 is made of a soft resin (epoxy resin or the like) having a Shore hardness of 95 or less, the hard recording medium is conveyed along the surface of the thermal head to perform printing. The cushioning effect can be exhibited more effectively.

The conductive layer 4b and the output terminals 5a and 5b are also provided.
For electrical connection of the driver IC 5, after the insulating film 7 is deposited on the upper surface of the driver IC 5 as described above, the conductive layer 4b is output from the upper surface of the substrate 1 through the upper surface of the insulating film 7 by the thin film forming technique described above. It is performed by patterning so as to extend onto the terminals 5a and 5b. The electrical connection between the conductive layer 4c and the input terminal is similarly made.

Thus, the above-described thermal head of the present invention conveys the recording medium along the surface of the thermal head (on the heating resistor 3 via the driver IC 5),
As the driver IC 5 is driven, electric power is applied to the heating resistors 3 via the conductive layers 4a and 4b to selectively cause the heating resistors 3 to generate Joule heat individually based on a print signal from the outside and generate the heat. It functions as a thermal head by conducting heat to the recording medium and forming a predetermined print on the recording medium.

The present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention.

For example, in the above embodiment, the driver IC 5
Although the output terminals 5a and 5b are arranged in two columns, they may be arranged in three or more columns instead. In this case, all the output terminals of the second and subsequent columns are located between the output terminals of the first column.

In the above-mentioned embodiment, if the surface roughness of the insulating film 7 is set in the range of 2,000 to 40,000Å as the center line average roughness Ra, the conductive layer 4b or the like is extremely strong on the surface by the anchor effect. The conductive layer 4b can be effectively prevented from peeling off even when the recording medium is in strong sliding contact with this portion, and the reliability of the thermal head can be improved. Therefore, the surface roughness of the insulating film 7 is the center line average roughness R.
It is preferable that a is set in the range of 2,000 to 40,000Å.

Further, in the above-mentioned embodiment, the surfaces of the heating resistor 3, the conductive layers 4a to 4c, etc. may be covered with a protective film made of silicon nitride or the like in order to improve wear resistance and corrosion resistance. Of course.

[0037]

According to the thermal head of the present invention, the output terminals of the driver ICs are arranged in a plurality of rows and the output terminals of the other rows are positioned between the output terminals of the first row, In addition, an insulating film is interposed between the driver IC and the extended portion of the conductive layer, and a through hole having a diameter smaller than that of the output terminal is provided in the insulating film, and one end of the conductive layer corresponds to the through hole. Since it is configured to be electrically connected to the output terminal, a space large enough to pass the conductive layer is secured between the through holes provided on the output terminals in the first row, and the conductive layer is It is possible to form a good pattern without disconnection and the like, and it is possible to relatively easily inspect the driver IC by forming the output terminal of the driver IC to be relatively large. Therefore, it is possible to improve the productivity of the thermal head.

According to the thermal head of the present invention, the conductive layer is electrically connected to the output terminal without being directly attached to the upper surface of the driver IC.
Even if the passivation film has a "chip" at the edge of C, a short circuit does not occur between the conductive layer and the logic circuit, and a "burr" is formed at the edge of the driver IC. Even if there is, disconnection of the conductive layer is effectively prevented, which also improves the productivity of the thermal head. Further, according to the thermal head of the present invention, since the upper surface of the insulating film is formed in a taper shape, it is possible to pattern the conductive layer and the like deposited thereon very well and easily. Therefore, the productivity of the thermal head will be further improved. Further, according to the thermal head of the present invention, the surface roughness of the insulating film is 2000 to 4000 in terms of center line average roughness Ra.
By setting it within the range of 0Å, a conductive layer or the like can be extremely strongly adhered to the surface by the anchor effect, and the peeling of the conductive layer is effectively prevented even when the recording medium is strongly slid on this portion. However, the reliability of the thermal head can be improved.

[Brief description of drawings]

FIG. 1 is a plan view of a thermal head according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the thermal head shown in FIG.

FIG. 3 is an enlarged view of a main part of FIG.

FIG. 4 is an enlarged view of a main part of FIG.

FIG. 5 is an enlarged plan view of a main part of a conventional thermal head.

[Explanation of symbols]

1 ... substrate 1a --- hole 3 ・ ・ ・ ・ ・ ・ Heating resistor 4b ... ・ ・ ・ Conductive layer 5 ... Driver IC 5a, 5b ... Output terminal of the first row 5b ... Output terminal of the second row 7 ... Insulating film 7a, 7b ... through hole

Claims (3)

(57) [Claims] 1. A substrate having a large number of heating resistors linearly arranged and a plurality of conductive layers electrically connected to the heating resistors is provided with holes, and a large number of holes are formed on the upper surface of the holes. embedded driver IC having an output terminal of said
In a thermal head in which a conductive layer and the output terminal are electrically connected , the output terminals of the driver IC are arranged in a plurality of rows, and the output terminals of the other rows are located between the output terminals of the first row. And the upper surface is tapered between the driver IC and the conductive layer.
Provided a through hole of smaller diameter than the output terminal in the insulating film with make interposed insulating film constituting the over-like, further, the
Extend one end of the conductive layer through the insulating film into the through hole
Zaisa thermal head, wherein the allowed. 2. A conductive layer on the substrate and a conductor in a through hole.
Special feature is that the electrode layer is formed collectively by the same process.
The thermal head according to claim 1, which is used as a characteristic. 3. The surface roughness of the insulating film is the center line average roughness R.
Set a within the range of 2000 to 40000Å in a.
The thermal head according to claim 1 or 2, characterized in that
Dead.