JPS5938911B2 - Thermal printing head and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal printing head used in various thermal recording systems such as printers and facsimiles, and a method for manufacturing the same. In the thermal printing head that constitutes the heat-generating part, we aim to improve the adhesion strength of the abrasion-resistant layer formed on the electrode and improve reliability by preventing alloy reaction between the heat-generating resistor and the upper electrode of the electrode. Is it for that purpose? ).

In general, thermal printing heads used in thermal recording systems such as printers and facsimiles have minute heating resistors arranged in a row or in a matrix, and a specific heating resistor is selected from among the plurality of heating resistors. By selectively energizing and generating heat, the sensitive recording paper develops color and the electrical signal information is visualized as characters and symbols.

Depending on the structure of the heating element and antibody, there are various types of thermal printing heads, such as thin film type, thick film type, and silicon monolithic type.Recently, high-density F5. Thin film type devices are becoming popular because they can achieve higher speeds relatively easily.

This thin film type thermal printing head has a SiO2 film formed on the entire surface of the glazed layer of an insulating substrate 1 such as a glazed ceramic substrate as shown in FIGS. , a plurality of heating resistors 2 made of TaN, etc. are formed, and electrodes 3 are further formed on the heating resistors 2 to form a heating section 4.
It is constructed by forming a wear-resistant layer 5 of SiC or the like with a thickness of about 5 μm on the heat generating portion 4 .

In addition, it is necessary that the resistor material of the heating resistor 2 does not react with it and that it can be well connected to an external circuit. Cr. 2, such as a lower layer electrode 3a made of NiCr and an upper layer electrode 3d made of Au.
We use layered purchasing. However, when such an electrode structure is adopted, the upper layer electrode 3b made of Au is formed by etching using a photoresist as a mask;
Since the lower layer electrode 3a is formed by etching using the upper layer electrode 3b as a mask, the width becomes narrower than the upper layer electrode 3b due to side etching.

Further, since the heating resistor 2 is also etched using the lower electrode 3a as a mask, the width of the heating resistor 2 is also narrower than that of the lower electrode 3a. Therefore, in the case of this multilayer electrode, as shown in FIG. 3, the width becomes reversely stepped, with the width becoming narrower from the top to the bottom, and especially in the case of the upper layer electrode 3b, side etching of the upper layer electrode 3b itself is included. It hangs down unsteadily.

In other words, in the case of a reverse step-like shape, when the wear-resistant layer 5 is formed on the electrode 3, the lower part of the protruding part 6 of the electrode 3 becomes hollow and a cavity 7 is created, and the aging recording paper When the electrodes 5 are brought into contact with each other and slid, the wear-resistant layer 5 tends to peel off, and the peeled portion of the electrode 5 wears out, causing a problem of disconnection.

Further, since the upper electrode 3 tends to react with the heat generating resistor 2, the resistance value of the heat generating part 4 varies and reliability is reduced. Therefore, the inventors of the present invention
As shown in the figure and FIG. 5, after forming the lower layer electrode 3a by etching, the upper layer electrode 3b is etched again to expose the lower layer electrode 3a from the upper layer electrode 3b, thereby preventing the formation of a cavity 7. However, it is difficult to finish the end of the upper layer electrode 3b vertically.
In fact, as long as a normal Au etching solution is used, the end of the upper layer electrode 3b will have an inversely tapered shape as shown in FIGS. 6 and 7, and a cavity 8 will still be formed, and the disadvantages of conventional etching will not occur. Ta.

The present invention solves these conventional problems and will be described below with reference to the drawings of FIGS. 8 to 12, which show an embodiment of the thermal printing head of the present invention and its manufacturing method. FIG. 8 shows a cross-sectional structure of a thermal printing head according to an embodiment of the present invention when cut in the longitudinal direction of the heat generating resistors, and FIG. 9 shows a cross-sectional structure when the same head is cut in the direction in which the heat generating parts are arranged. It shows.

As shown in FIGS. 8 and 9, in the thermal printing head of the present invention, the end surface of the upper layer electrode 3b made of Au of the electrode 3 has a smooth forward tapered shape in which the upper surface width is narrower than the lower surface width, and the lower layer electrode 3a The width of the lower electrode 3a is made wider than the width of the lower surface of the upper electrode 3b, so that the lower electrode 3a is exposed from the upper electrode 3b.

As shown in FIGS. 8 and 9, the electrode 3 in which the end face shape of the upper layer electrode 3b is tapered and the lower layer electrode 3a is exposed from the upper layer electrode 3b can be formed by the following method. There is.

As shown in FIG. 10, after successively laminating two layers of heating resistors, a lower electrode 3a layer, and an upper electrode 3b layer on an insulating substrate 1, a photoresist film 9 is selectively formed on the upper electrode 3b layer. Then, using the photoresist film 9 as a mask, the upper electrode 3b layer is etched with a mixed solution of nitric acid and hydrochloric acid. Next, the upper layer electrode 3b is further etched with an aqueous solution containing at least potassium cyanide and benzoic acid to form a plurality of rows of upper layer electrodes 3b.
When the upper layer electrode 3b is separated into the upper layer electrode 3b, the end portion of the upper layer electrode 3b has a forward tapered shape as shown in FIG. At this time, if only a mixed solution of nitric acid and hydrochloric acid is used as the etching solution, the photoresist film 9 will be corroded.On the other hand, if the upper layer electrode 3b is etched only with a mixed solution of potassium cyanide and benzoic acid, the edge of the upper layer electrode 3b will be etched. The portion has a reverse tapered shape as shown in FIGS. 6 and 7. That is, in order to form the end portion of the upper electrode 3b into a forward tapered shape, two types of processing liquids are used in the order described above, as described above. Also,
In the thermal printing head of the present invention, the thickness of the upper layer electrode 3b is set to, for example, A.
When the thickness is 2μ, which is necessary for bonding using a u-Sn alloy, the width of the tapered end face portion is 5 to 10μ, and the end portion of the upper layer electrode 3b exhibits an extremely smooth surface shape. After etching the upper layer electrode 3b as described above, the next step is to etch the lower layer electrode 3a.
There are two methods for etching the lower electrode 3a. First, in the first method, after etching the upper layer electrode 3b, as shown in FIG. 11, the lower layer electrode 3a is etched with the photoresist film 9 in its original state.

When the lower electrode 3a is etched in this way,
An undercut occurs under the upper layer electrode 3b. Next, when the upper layer electrode 3b is etched again with a mixed solution of potassium cyanide and benzoic acid, the lower layer electrode 3a is exposed from the upper layer electrode 3b while maintaining the tapered end of the upper layer electrode 3b. Thereafter, the photoresist film 9 is peeled off and the heat generating portion 4 is covered with the wear-resistant layer 5, thereby obtaining a thermal printing head having the structure shown in FIGS. 8 and 9. In the second method, after etching the upper layer electrode 3b as shown in FIG. 10, baking is performed at, for example, 160° C. for 30 minutes, and the photoresist film 9 is etched as shown in FIG. The end portion is softened and hangs down to cover the tapered end portion of the upper layer electrode 3b and to be closely viewed from the upper surface of the lower layer electrode 3a.

In this state, if the lower electrode 3a is etched, and then the photoresist film 9 is peeled off and the heat generating part 4 is covered with the abrasion resistant layer 5, a thermal printing structure as shown in FIGS. 8 and 9 can be obtained. Head is obtained. As mentioned above, two methods have been described as methods after etching the upper layer electrode 3b.
The latter method requires less etching of the upper layer electrode 3b, so the width of the electrode 3 can be increased, and is more advantageous than the former method when obtaining a high-density head.

As is clear from the above description, in the thermal printing head of the present invention, the upper layer electrode 3b of the two-layer structure electrode 3 has an end tapered shape whose width becomes narrower from the bottom surface to the top surface.
In addition, since the width of the lower electrode in the arrangement direction of the heating resistors is wider than the width of the upper electrode so that the lower electrode 3a is exposed more than the upper electrode 3b, the wear-resistant layer 5 is formed on the heating part 4. In this case, the adhesion strength of the wear-resistant layer 5 is improved, and peeling of the wear-resistant layer 5 due to contact abrasion with the heat-sensitive recording paper can be prevented, thereby preventing disconnection of the electrode 3.

In addition, due to the temperature rise when the wear-resistant layer 5 is formed by sputtering or the like, the Au of the upper layer electrode 3b and the S of the heating resistor 2
It is possible to prevent an alloy reaction with the i-Ta-based resistance material, reduce variations in resistance value, and achieve high reliability. Moreover, according to the method of manufacturing a thermal printing head of the present invention, a head having the above-mentioned effects can be easily obtained. In addition, in the above explanation, the heating resistor 2 is of Si--Ta type,
Although the electrode 3 has a two-layer structure of Au and Cr, in the present invention, even if the material is changed, the electrode 3
The same applies even if the structure is three or four layers, and this does not depart from the purpose of the present invention.

As described above, according to the thermal printing head and the method for manufacturing the same of the present invention, it is possible to improve the adhesion strength of the wear-resistant layer and to obtain a highly reliable head.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a general thermal printing head, FIG. 2 is a cross-sectional view of the head taken along line A-A in FIG. 1, and FIG. A cross-sectional view cut along line B,
FIG. 4 is a sectional view showing the thermal printing head developed by the present inventors at the development stage of the present invention, cut in the longitudinal direction of the heating resistor, and FIG. 5 shows the arrangement of the heating parts of the thermal printing head. 6 is a sectional view corresponding to FIG. 4 for explaining the defects of the same head, and FIG. 7 is a sectional view corresponding to FIG. 5 for explaining the defects of the same head. FIG. 8 is a sectional view showing a thermal printing head according to an embodiment of the thermal printing head and its manufacturing method according to the present invention, cut in the longitudinal direction of the heating resistor, and FIG. 10 and 1 are cross-sectional views cut in the arrangement direction of
FIG. 1 is a sectional view showing a manufacturing process of a thermal printing head and a method of manufacturing the same according to an embodiment of the present invention, and FIG. 12 is a sectional view showing another example of the manufacturing process shown in FIG. 11. It is a diagram. 1...Insulating substrate, 2...Heating resistor,
3...electrode, 3a...lower layer electrode 3b
... Upper layer electrode, 4 ... Heat generating part, 5 ...
... Wear-resistant layer, 9... Photoresist film.

Claims (1)

[Scope of Claims] 1. A plurality of heat generating resistors formed on an insulating substrate, an electrode having at least a two-layer structure formed so that a heat generating portion is formed on the heat generating resistors, and a heat generating portion formed on the heat generating resistor. and a wear-resistant layer covering the electrode, the end of the upper electrode of the electrode has a forward tapered shape in which the upper surface width is narrower than the lower surface width, and the width of the lower electrode in the arrangement direction of the heating resistors is the lower surface of the upper electrode. A thermal printing head characterized by being wider than its width. 2. The thermal printing head according to claim 1, wherein the electrode is composed of an upper layer electrode made of Au and a lower layer electrode made of Cr. 3. A step of providing a heating resistor layer on an insulating substrate, a step of providing a lower electrode layer on the heating resistor layer, a step of providing an upper electrode layer made of Au on the lower electrode layer, and a step of providing the upper electrode layer. selectively providing a resist film thereon, and etching the upper electrode layer with a mixture of nitric acid and hydrochloric acid using the resist film as a mask to separate the upper electrode layer into a plurality of rows, and then removing at least potassium cyanide and benzoic acid. etching the ends of the upper layer electrode into a forward tapered shape by etching with an aqueous solution containing the material; and etching the lower electrode layer to separate it into multiple rows of lower electrodes, and then etching the upper electrode again. A method for manufacturing a thermal printing head, characterized in that: 4. A step of providing a heating resistor layer on an insulating substrate, a step of providing a lower electrode layer on the heating resistor layer, a step of providing an upper electrode layer made of Au on the lower electrode layer, and a step of providing the upper electrode layer on the upper electrode layer. a step of selectively providing a resist film on the substrate, and etching the upper electrode layer with a mixture of nitric acid and hydrochloric acid using the resist film as a mask to separate the upper electrode layer into a plurality of rows of upper electrode layers containing at least potassium cyanide and benzoic acid. etching the ends of the upper layer electrode into a forward tapered shape by etching with an aqueous solution of A method for manufacturing a thermal printing head, comprising the step of etching a layer.