JPS5941872B2 - Method of manufacturing thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a thermal head used in various heat-sensitive recording systems, and in particular to a method for manufacturing a thermal head used in various heat-sensitive recording methods, and in particular, to reduce variations in etching in the photo-etching process of the conductive film thickness that becomes the electrode of the thermal head, and to reduce the variation in the thickness of the photoresist film. This is a manufacturing method in which acid resistance is relaxed, the shape and resistance value of the heating resistor layer of the heating section are made uniform, and a thermal head with good printing quality is obtained.

Conventionally, a thin film type thermal head has been manufactured by the manufacturing process shown in FIGS. 1 to 3. That is, as shown in FIG. Layer 2 is coated with a thickness of about 0.4μ by vapor deposition, etc.
On top of this, a conductive thin film layer 3 is uniformly formed with a thickness of about 0.2μ by vapor deposition or the like, and then electroplating is performed on this thin film layer 3 using the thin film layer 3 as a cathode to make it conductive. After forming a thick film layer 4 having a thickness of about 2 μm, a heating resistor layer 2 and a thin film layer 3 are formed on the substrate 1 as shown in FIG.
Then, the thick film layer 4 is photo-etched at regular intervals to form a plurality of rows of elongated wiring patterns that define the width W of the heating resistor layer of the heating section, and then, as shown in FIG. In order to expose a part of the heat generating resistor layer 2 and form a length L of the heat generating resistor layer of the heat generating part as shown in FIG. This is a manufacturing method in which the film is removed by photo-etching. By the way, in this conventional manufacturing method, it is necessary to perform etching of the thick film layer 4 and the thin film layer 3 with strong acid because of their large thickness, and therefore it is necessary to use a resist film with high acid resistance. In order to improve the properties, it was necessary to make the resist film thicker.

However, when the thickness of the resist film is increased in this manner, variations occur in the pattern dimensions (W width and L length of the heat generating portion) of the photoresist film (not shown) of the wiring pattern.
Furthermore, when the thick film layer 4 is thick, the side etching is large in that part, and the thick film layer 4, thin film layer 3, and heating resistor layer 2 each have a W width several μ smaller than the W pattern width of the photoresist film. Although a plurality of rows of elongated wiring patterns are formed, since the side etching of the thick film layer 4 is uneven, the W width of the heat generating resistor layer 2 in the heat generating section also varies, resulting in variations in resistance value. .

Further, a similar variation occurs in the process of forming the length L of the heat generating portion. The variation due to this side etching is 1 mm per 1 mm.
To explain this using a thermal head with a 6-dot heating section, for example, the thickness of the thick film layer 4 is 2μ, the side etching is 4μ, which is twice the film thickness, and the pattern dimension of the mask is 40μ in W width.
If the L length is 100 μm, the variation in pattern dimensions is 10% in the W width and 4% in the L length, for a total of 14%.
This causes variations in the resistance value, and the same variation occurs in the resistance value.

As described above, variations in the pattern dimensions and side etches of the photoresist combine to cause variations in the shape and resistance value of the heat generating portion, resulting in the problem of non-uniform print density. The present invention solves these conventional problems, and will be described below with reference to FIGS. 4 to 7, which show an embodiment of the method for manufacturing a thermal head according to the present invention.

Note that the same parts as in FIGS. 1 to 3 are given the same numbers. As shown in FIG. 4, a heating resistor layer 2 such as Si-Ta alloy is uniformly formed on an insulating substrate 1 such as ceramic by vapor deposition, and a conductive layer 2 such as Au is uniformly formed on this layer. After forming the thin film layer 3, as shown in FIG. 5, mask alignment is performed using a glass mask or the like, and a plurality of rows of elongated wiring patterns formed of a resist film (not shown) are used as a mask to form a pattern on the substrate 1. Parts of the heat generating resistor layer 2 and the thin film layer 3 are removed by etching at regular intervals to form a plurality of rows of elongated wiring patterns and to define the dimension W width in the width direction of the heat generating portion.

Next, as shown in FIG. 6, electroplating is performed using the thin film layer 3 on the heat generating resistor layer 2 in multiple rows as a cathode, and A is applied thereon.
A conductive thick film layer 4 such as u is formed. Thereafter, a resist film (not shown) is used to remove part of the thin film layer 3 and thick film layer 4 on the heat generating resistor layer 2 by etching in order to form a heat generating part as shown in FIG. Mask alignment is performed using a glass mask or the like to form an elongated pattern in which a part of the thick film layer 4 is exposed in a direction that crosses the multiple rows of thick film layers 4. Using the resist film as a mask, the exposed thickness is The film layer 4 and the thin film layer 3 are removed by etching to form the length L of the heating resistor layer of the heating section. Thereby, it can be manufactured. Note that the heating resistor layer 2 has a film thickness of 0.4 to 1
．． When using a 0μ Si-Ta alloy film, HF+HNO3+CH3COOH may be used as the etching solution, and when using an Au film with a thickness of 0.1 to 0.3μ as the thin film layer 3, K+I2 or HNO3+ may be used as the etching solution.
HCt may be used, and the thin film layer 3 may be used as the thick film layer 4.
Au may be formed so that the film thickness is approximately 2 μm. As can be seen from the above description, the method for manufacturing a thermal head according to the present invention differs from the conventional method in that the steps of forming the conductive thick film layer 4 and forming a plurality of rows of elongated wiring patterns are performed in reverse. In the conventional method, multiple rows of elongated wiring patterns were formed after forming the thick film layer 4, so photo
The thickness of the resist film must be increased, and the variation in pattern dimensions and side etching of the thin film layer 3 and thick film layer 4 are large.This variation causes variation in the resistance value of the heat generating resistor layer 2 of the heat generating part. However, since the method of the present invention first forms a long and thin wiring pattern in multiple rows, the acid resistance of the photoresist film is relaxed, and the photoresist film is - The thickness of the resist film can be made thinner, thereby reducing the variation in pattern dimensions, and since the thickness of the thin film layer 3 is as thin as 0.1 to 0.3 μm, it is possible to Even if the film is twice the same thickness as the conventional example, 0.
Side etching can be reduced to 2 to 0.6 microns, variations in the resistance value of the heating resistor layer 2 of the heating section can be reduced, and printing density can be made uniform.

Furthermore, this effect increases as the thickness of the thick film layer 4 increases and as the ratio of the W width to the L length increases. Furthermore, the amount of material constituting the thick film layer 4 can also be reduced. As described above, the method for manufacturing a thermal head according to the present invention can obtain excellent effects by simply changing the process order.

[Brief explanation of the drawing]

1 to 3 are perspective views showing manufacturing steps in a conventional thermal head manufacturing method, and FIGS. 4 to 7 are perspective views showing manufacturing steps in an embodiment of the thermal head manufacturing method of the present invention. It is. 1...Substrate, 2...Heating resistor layer, 3
... Thin film layer, 4... Thick film layer.

Claims (1)

[Claims] 1. A first step of sequentially laminating a heating resistor layer and a conductive thin film layer on an insulating substrate, and forming a plurality of rows of elongated patterns on the conductive thin film layer, leaving the plurality of rows of elongated pattern parts. A second step of etching away the conductive thin film layer and the heating resistor layer, and electroplating is performed using the plurality of rows of conductive thin film layers remaining on the insulating substrate as cathodes to form a conductive thick film layer on the conductive thin film layer. and forming an elongated pattern in which a part of the conductive thick film layer is exposed in a direction that crosses the plurality of rows of conductive thick film layers, and the exposed conductive thick film layer and the conductive thin film layer. a fourth step of etching away the heating resistor layer to expose the heating resistor layer.