JPH11157112A - Manufacture of thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a coating thickness of a photoresist uniform when forming a thin film circuit pattern or the like by photolithography and to form the good thin film circuit pattern without disconnection or short circuit. SOLUTION: This manufacturing method for a thermal head comprises a process for emitting a laser light to a ceramic substrate 1 having a glaze layer 2 on the top face thereof from a side of the glaze layer 2 to vaporize a part of the glaze layer 2, a process for forming a via-hole 1a at a predetermined position on the ceramic substrate 1 by melting the substrate, a process for embedding a driver IC 5 having a terminal 5a on the top face thereof in the via-hole 1a and a process for providing a plurality of heating resistors 3 and a thin film circuit pattern 4 such that a part of the pattern 4 is extended to the terminal 5a on the top face of the driver IC.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thermal head incorporated as a printing device such as a video printer and a facsimile.

[0002]

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

[0003] As such a conventional thermal head, for example, a ceramic substrate made of alumina ceramics on which a glaze layer having an arc-shaped cross section is partially adhered is used.
A through hole is formed substantially parallel to the glaze layer at a position separated from the glaze layer by a predetermined distance, and a rectangular driver IC having terminals on the upper surface is embedded in the through hole, and a plurality of holes are formed on the glaze layer. There is known a structure in which a predetermined thin-film circuit pattern is applied to a plurality of heat generating resistors from the glaze layer to the terminals of the driver IC through the upper surface of the ceramic substrate.

According to such a thermal head, since the driver IC is buried in the through hole of the ceramic substrate, there is no one that protrudes more than the surface of the thermal head. Therefore, thermal recording is performed on a hard recording medium such as a plastic card. Is performed, the recording medium can be conveyed onto the heating resistor in a flat shape, that is, a flat pass of the recording medium can be performed.

The through hole of the ceramic substrate in the above-described thermal head is formed by performing laser processing on the ceramic substrate and drilling it before attaching and forming a thin film circuit pattern and the like on the upper surface of the ceramic substrate. I was Specifically, as shown in FIG.
CO ₂ laser or YAG laser on the upper surface of
A predetermined through-hole is formed by irradiating the ceramic substrate 11 in an annular shape along the contour of the region where the through-hole is to be formed on the upper surface of the ceramic substrate and fusing the ceramic substrate 11 by the irradiated laser light.

[0006]

However, in such a conventional thermal head, when a through hole is formed in the ceramic substrate 11, the laser light is directly irradiated on the upper surface of the ceramic substrate 11. Melting from the vicinity of the upper surface of the ceramic substrate 11 by light irradiation
The scattered particles such as alumina adhered again to the surface of the ceramic substrate 11 to form projections (diameter: 10 to 100 μm). Such protrusions are difficult to remove because they are fusion-fixed materials. Therefore, when a thin film circuit pattern is formed on the upper surface of the ceramic substrate 11 in a later step by a conventionally known photolithography technique, the above-described protrusions are required. The thickness of the photoresist applied varies between the area where the object is formed and the other areas, resulting in the disconnection and short-circuiting of the thin film circuit pattern, which significantly reduces the mass productivity of the thermal head. Was.

[0007]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned disadvantages, and a method of manufacturing a thermal head according to the present invention is directed to a method of manufacturing a thermal head with a laser beam on a ceramic substrate having a glaze layer formed on the upper surface. From the glaze layer side to evaporate a part of the glaze layer and blow the ceramic substrate to form a through hole in a required portion of the ceramic substrate; and a driver I having a terminal on the upper surface in the through hole.
Embedding C, and applying a plurality of heating resistors and a thin-film circuit pattern on the glaze layer such that a part of the pattern extends to a terminal on the upper surface of the driver IC. This is for manufacturing a thermal head.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. [First Embodiment] FIG. 1 is a sectional view of a thermal head manufactured according to a first embodiment of the present invention, wherein 1 is a ceramic substrate, 1a is a through hole, 2 is a glaze layer, 3 is a heating resistor,
4 is a thin film circuit pattern, 5 is a driver IC, and 5a is a terminal of the driver IC 5. The ceramic substrate 1 is made of, for example, alumina ceramic having a thickness of 0.5 to 1.5 mm. A through hole 1a is provided at the center of the ceramic substrate 1, and the glaze layer 2, the heating resistor 3, the thin film circuit pattern 4 and the like are formed on the upper surface in the through hole 1a. And functions as a supporting base material for supporting the driver IC 5.

The glaze layer 2 on the ceramic substrate 1 is formed so as to partially protrude in an arc shape in cross section over the entire upper surface of the substrate 1. The glaze layer 2 is made of a low heat conductive material such as a high melting point glass, and the heating resistor 3 attached to the upper surface thereof is projected upward by a projection 2a to effectively increase the printing pressure on the recording medium and to increase the heating resistance. The heat generated by the body 3 is accumulated and dissipated in the protruding portion 2a so as to be at an appropriate temperature, and acts as a heat storage layer for maintaining the thermal response characteristics of the thermal head in a good condition.

The reason why the glaze layer 2 is applied not only directly under the heating resistor 3 but also over the entire upper surface of the ceramic substrate 1 is that a through hole 1a is formed in the ceramic substrate 1 by a known laser processing method. This is to prevent particles of alumina or the like, which are melted by laser light irradiation, from re-adhering to the upper surface of the ceramic substrate 1 during formation.

Further, the protrusion 2 of the glaze layer 2
a, a heating resistor 3 and a thin film circuit pattern 4 are partially connected to a terminal 5a of a driver IC 5 which will be described later.
It is applied so as to extend up.

Each of the heating resistors 3 is made of TaSi.
Since it is made of an electric resistance material such as O, TiSiO, TaN or the like, when electric power from an external power supply is applied through the thin film circuit pattern 4, Joule heat is selectively generated individually to form a print on a recording medium. To generate heat at a temperature required for the heating, for example, at a temperature of 150 to 250 ° C.

The thin film circuit pattern 4 is electrically connected to the heating resistor 3 and the terminal 5a of the driver IC 5 to apply power from an external power source to the heating resistor 3 and the driver IC 5, or To supply an external printing signal or the like.

On the other hand, the driver IC 5 buried in the through hole 1a of the ceramic substrate 1 is for controlling on / off of the power applied to the heating resistor 3 based on an external printing signal. The output from the terminal 5a is applied to the heating resistor 3 via the thin film circuit pattern 4 described above,
The heating resistors 3 are selectively and individually heated to generate Joule heat.

The driver IC 5 is buried in the through hole 1a of the ceramic substrate 1 in order to prevent the upper surface of the driver IC 5 from protruding significantly above the surface of the thermal head. A flat path of the recording medium, that is, the recording medium can be conveyed onto the heating resistor 3 in a flat shape.

The driver IC 5 is fixed at a predetermined position in the through hole 1a by an adhesive 6 such as an epoxy resin, a polyimide resin, or a polyether amide.

Then, a protective film 7 made of silicon nitride or the like is further deposited on the upper surface of the heating resistor 3, the thin film circuit pattern 4, the driver IC 5, etc. on the insulating substrate 1 as described above. Thus, the heating resistor 3 and the thin film circuit pattern 4 are protected from abrasion due to sliding contact of the recording medium and corrosion due to contact with moisture or the like contained in the atmosphere.

Thus, the above-described thermal head can be used, for example, when printing is performed using an ink ribbon.
Along with the driving of C5, a predetermined power is applied to the heating resistor 3 via the thin film circuit pattern 4 based on an external printing signal, and the heating resistors 3 are individually selectively Joule-heated. The ink on the ink ribbon is heated and melted by the applied heat, and is transferred to a recording medium using an external platen or the like, thereby forming a predetermined print on the recording medium.

Next, a method for manufacturing the above-described thermal head will be described with reference to FIGS. (1) First, as shown in FIG. 2A, a ceramic substrate 1 on which a glaze layer 2 is adhered over substantially the entire upper surface.
Then, as shown in FIG. 2B, the ceramic substrate 1 is irradiated with a laser beam from above the glaze layer 2 to form a through hole 1a.

When the ceramic substrate 1 is made of alumina ceramics, for example, Al ₂ O ₃ (alumina), S
A ceramic green sheet is formed by adding a suitable organic solvent and a solvent to ceramic raw material powders such as iO ₂ (silica) and MgO (magnesia) and mixing them to form a slurry, and employing a well-known doctor blade method. Thereafter, the ceramic green sheet is punched into a predetermined shape and fired at a high temperature (about 1600 ° C.) to produce a sheet having a thickness of, for example, 0.5 to 1.5 mm.

The glaze layer 2 on the upper surface of the ceramic substrate
For example, a glass paste obtained by adding and mixing an appropriate organic solvent and a solvent to a powder of high melting point glass is printed on the upper surface of the ceramic substrate 1 by a conventionally well-known screen printing method so that a part thereof protrudes.・ Apply and apply this to high temperature (1000
C. to 1200 ° C.), thereby forming a projection 2 a having a circular cross section on a part of the glaze layer 2.
Is formed. The projection 2a may be partially or double-applied with a glass paste,
The glaze layer 2 is formed, for example, by processing the surface shape by etching a part other than the part a, and has a thickness of, for example, 50 to 250 μm at the protruding part 2 a and 20 to 100 μm at the other part. .

The above-described drilling of the ceramic substrate 1 is performed by forming the ceramic substrate 1 on the glaze layer 2 from the O.
While blowing assist gas such as ₂ (oxygen) and N ₂ (nitrogen) from above with a strength of ² to 10 kgf / cm ² ,
_{2 A} laser (50 W to 150 W) or a YAG laser (50 W to 150 W) is radiated in an annular shape along the contour of the area where the through hole 1 a is formed, and a part of the glaze layer 2 is evaporated by the radiated laser light. And the ceramic substrate 1 is blown to form a through hole 1
a is formed.

In this case, since the glaze layer 2 is adhered to the upper surface of the ceramic substrate 1 to which the laser beam is irradiated, particles such as alumina forming the ceramic substrate 1 melt and scatter around the surface. Also, particles of alumina and the like melted by the laser processing are released to the lower surface side of the ceramic substrate 1 by the above-described assist gas, so that the melted alumina particles and the like do not adhere to the upper surface of the ceramic substrate 1 again. In addition, a part of the glaze layer 2 which evaporates due to the irradiation of the laser beam is then not solidly adhered to the surface of the ceramic substrate 1 like alumina particles in the conventional example even if it is cooled and solidified. These particles are merely deposited on the surface of the ceramic substrate 1 as glass fine particles. Can be very easily removed by purification, a thin film circuit pattern 4, etc. can be extremely smooth forms the surface of the glaze layer 2 is deposited and formation.

The glaze layer 2 has a part (projection 2a) acting as a heat storage layer, and when forming such a glaze layer as a heat storage layer, a part other than the protrusion may be used. Because they can be formed at the same time,
The number of steps does not increase as compared with a conventional manufacturing method or the like.

(2) Next, as shown in FIG. 2C, the driver IC is inserted into the through hole 1a of the ceramic substrate 1 described above.
5 is buried.

The driver IC 5 has a plurality of terminals 5a provided on the upper surface thereof at a height substantially equal to the upper surface of the glaze layer 2 attached to the ceramic substrate 1 (± 3).
It is buried in the through-hole 1a using a vacuum suction collet so that the position is set to within 0 μm.

The driver IC 5 is fixed to the ceramic substrate 1 by temporarily fixing the driver IC 5 to a predetermined position in the through-hole 1a using an adhesive tape or the like, while keeping the side surface of the driver IC 5 and the inner wall of the hole 1a. In this process, a varnish such as an epoxy resin is filled using a dispenser or the like, and then the varnish is thermally cured and the adhesive tape is removed.

(3) Finally, as shown in FIG. 2D, a TaSi layer is formed on the glaze layer 2 on the upper surface of the ceramic substrate.
A plurality of heating resistors 3 made of O or the like and a thin-film circuit pattern 4 made of Al (aluminum) or the like are covered such that a part of the circuit pattern 4 extends to the terminal 5a on the upper surface of the driver IC. These are then covered with a protective film 7.

The heating resistor 3 and the thin film circuit pattern 4
First, TaSiO is formed over the entire upper surface of the ceramic substrate 1 in which the driver IC 5 is embedded in the through hole 1a.
And Al sequentially by a conventionally known sputtering method,
They are formed by applying them and processing them into a predetermined pattern by a conventionally known photolithography technique. The electrical connection between the thin film circuit pattern 4 and the terminal 5a is made by partially attaching the thin film circuit pattern 4 to the driver I when the thin film circuit pattern 4 is applied to the upper surface of the glaze layer 2 by the above-described photolithography technique or the like.
This is performed by extending the terminal 5a on the C upper surface.

At this time, since the upper surface of the glaze layer 2 is extremely smooth as described above, there is no large variation in the coating thickness of the photoresist. Circuit pattern 4
Can be formed relatively easily, and the mass productivity of the thermal head is significantly improved.

The protective film 7 covers the upper surface of the heating resistor 3, the thin film circuit pattern 4, the driver IC 5 and the like on the ceramic substrate 1 by a conventionally known sputtering method using Si ₃ N ₄ (silicon nitride) or the like. Thus, the thermal head as a product is completed.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to (a) to (d). However, description of contents overlapping with the above-described first embodiment will be omitted, and only points different from the first embodiment will be described.

In the second embodiment, the following (1) to (1)
The thermal head is manufactured by the process (3).

(1) First, as shown in FIG. 3 (a), a ceramic substrate 1 on which a first glaze layer 2A and a second glaze layer 2B are adhered on the upper surface at a predetermined interval is prepared. Then, a predetermined laser beam is radiated in a circular shape from above the second glaze layer 2B of the ceramic substrate 1 while blowing an assist gas, thereby evaporating the second glaze layer 2B as shown in FIG. 3B. By fusing the ceramic substrate 1, a through hole 1 is formed at a required portion of the ceramic substrate 1.
a is formed.

The first glaze layer 2A and the second glaze layer 2B are formed by printing a glass paste on the upper surface of the ceramic substrate 1 and baking the same, similarly to the glaze layer 2 of the first embodiment. Are formed simultaneously on the upper surface.

(2) Next, as shown in FIG. 3C, the terminal 5a is provided on the upper surface in the through hole 1a of the ceramic substrate 1 described above.
Is embedded.

(3) Finally, on the first glaze layer 2A on the ceramic substrate 1, a plurality of heating resistors 3 and a thin film circuit pattern 4 are formed by partially forming the pattern 4 on the upper surface of the ceramic substrate 1 It is applied so as to extend over the terminal 5a of the driver IC 5 via the upper surface of the 2 glaze layer 2B.

In the manufacturing method of the second embodiment, unlike the first embodiment in which the glaze layer 2 is formed on the entire upper surface of the ceramic substrate 1, the glaze layers 2A and 2B are partially formed only at necessary places. However, also in this manufacturing method, the glaze layer 2B is adhered to the upper surface of the ceramic substrate 1 irradiated with the laser beam, and particles such as alumina forming the ceramic substrate 1 are melted near the surface. The particles such as alumina which are not scattered and are melted by the laser processing are released to the lower surface side of the ceramic substrate 1 by the above-described assist gas.
The melted alumina particles and the like do not adhere again to the upper surface of the ceramic substrate 1, and a part of the second glaze layer 2B that evaporates by the irradiation of the laser beam is then cooled and solidified. Are not adhered firmly to the surface of the ceramic substrate 1 as large projections as described above, but are merely accumulated on the surface of the ceramic substrate 1 as mist-like glass fine particles. It can be removed very easily by ultrasonic cleaning, and the surface of the ceramic substrate 1 or the like on which the thin film circuit pattern 4 and the like are attached and formed can be made extremely smooth. Therefore, when the thin film circuit pattern 4 and the like are formed by a conventionally known photolithography technique, there is no large variation in the coating thickness of the photoresist, and a good thin film circuit pattern 4 without disconnection or short circuit can be formed relatively easily. Will be able to

The manufacturing method according to the present invention employs the first and second methods described above.
The present invention is not limited to the embodiment, and various changes and improvements can be made without departing from the spirit of the present invention.

[0040]

According to the present invention, a glaze layer is adhered on the upper surface of a ceramic substrate irradiated with a laser beam, and particles such as alumina forming the ceramic substrate are melted and scattered near the surface. Therefore, the molten alumina particles do not re-adhere to the upper surface of the ceramic substrate, and a part of the glaze layer that evaporates due to the irradiation of the laser beam becomes large projections even after being cooled and solidified. Instead of firmly adhering to the surface of the ceramic substrate, they only become mist-like glass fine particles and accumulate on the surface of the ceramic substrate, so these should be removed very easily by brush cleaning or ultrasonic cleaning. Thus, the surface of the ceramic substrate or the like on which the thin film circuit pattern is deposited and formed can be made extremely smooth. Therefore, when a thin film circuit pattern or the like is formed by a conventionally known photolithography technique, there is no large variation in the coating thickness of the photoresist, and a good thin film circuit pattern without disconnection or short circuit can be formed relatively easily. Will be able to

[Brief description of the drawings]

FIG. 1 is a sectional view of a thermal head manufactured according to a first embodiment of the present invention.

FIGS. 2A to 2D are cross-sectional views for explaining steps of a first embodiment of a method of manufacturing a thermal head according to the present invention.

FIGS. 3A to 3D are cross-sectional views for explaining steps in a second embodiment of the method of manufacturing a thermal head according to the present invention.

FIG. 4 is a sectional view of a conventional thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ceramic substrate 1a ... Through-hole 2 ... Glass glaze layer 3 ... Heating resistor 4 ... Thin film circuit pattern 5 ... Driver IC 5a ... Terminal

Claims (1)

[Claims] A ceramic substrate having a glaze layer adhered to an upper surface thereof is irradiated with a laser beam from the glaze layer side to evaporate a part of the glaze layer and blow the ceramic substrate to melt the ceramic substrate at a required portion. Forming a through hole in the through hole; embedding a driver IC having a terminal on the upper surface in the through hole; forming a plurality of heating resistors and a thin film circuit pattern on the glaze layer; A step of extending and attaching to terminals on the upper surface of the driver IC.