JP2863283B2 - Thermal head and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention arranges a plurality of heating resistors linearly on a substrate and selectively heats the heating resistors to record on thermal paper or the like. More particularly, the present invention relates to a high-precision thermal head in which a space between heat-generating resistors is narrowed, a short-circuit or the like is hardly generated, and a heat-generating layer has a uniform resistance value, and a manufacturing method thereof.

[Conventional technology]

Thermal heads often used in facsimile machines are
The heating resistors arranged in a straight line selectively generate heat, and this heat-generating portion is brought into contact with the thermal paper to record small dots on the thermal paper. Etc. are recorded. Therefore, the quality of characters and the like printed depends on the density or size of the dots. Therefore, it is possible to record dots as small as possible, and furthermore, it is required to form a heating resistor array arranged at a high density.

For this purpose, various attempts have conventionally been made using photolithography technology.

FIG. 2 is an explanatory view of a process of manufacturing a heating element portion of a conventional thermal head as one example. 2 (A) is an explanatory view of the process, FIG. 2 (B) is a sectional structural view of the thermal head corresponding to the process of FIG. 2 (A), and FIG. 2 (C) is a plan structural view of the same thermal head. It is.

Step A polysilicon layer 2 ', for example, an electrode layer 3' made of Al is formed on a ceramic substrate 1 of, for example, alumina.

Step Next, a first patterning using a photoresist film is performed, a part of the Al electrode layer 3 'is removed by etching to form two parts 31', 32 'and a part of the polysilicon layer 2'. Expose 20 '.

Step A second photoresist film 4 is formed on the substrate surface including the Al electrode layers 31 'and 32'.

Step 2nd etching is performed, and lead electrodes 33 ', 3
3 ", 34 ', 34" are formed.

Step The polysilicon layer 2 'is etched using the photoresist film 4 to form a strip-shaped heating resistor 21'22'.

As another method, there has been proposed a method of forming a pattern of a lead electrode after forming a pattern of a heating resistor (see, for example, Japanese Patent Publication No. 56-51111).

FIG. 3 shows an example. FIG. 3A is a process explanatory view, FIG. 3B is a sectional structural view of the thermal head corresponding to FIG. 3A, and FIG. 3C is a plan structural view of the same.

Step A heating element layer 2 ′ is formed on a ceramic substrate 1.

Step The heating element layer 2 'is etched using a photoresist film (not shown) to form striped heating element patterns 21' and 22 '.

Step After the lead electrode material is formed on the heating element patterns 21 'and 22', the lead electrodes are etched using another photoresist film so that the width of the lead electrodes is slightly smaller than the width of the heating element patterns. Electrodes 33'-1,33 ''-1,34 '
At this time, the width of the electrode pattern is slightly reduced in consideration of the mask shift between the electrode pattern and the heating element pattern.

Since these methods use the photolithography technique, a thermal head having a large number of heating elements arranged at high density can be manufactured. In FIG. 2, however, a heating resistor formed by etching is used. However, there is a problem that the variation in the resistance value is large.

This is because in the process of FIG.
The etching solution penetrates from the void portion 41 formed without well entering the step portions of the Al electrode layers 31 'and 32', and as shown in the plan view of the step of FIG. It is because it is formed.

In the case of FIG. 3, the width of the heating resistor must be increased to some extent over the entire length of the heating resistor in consideration of mask misalignment in the process. There is.

In view of these points, the present inventors have previously proposed a thermal head in which the width of the heating resistor is slightly larger than the width of the lead electrode in and around the heating portion (Japanese Patent Application No. 2-1979). No.).

This will be described with reference to the manufacturing process diagram of FIG. FIG. 4A is a process explanatory view, and FIG. 4B is a plan or sectional structural view of the thermal head corresponding to the process of FIG. 4A.

Process Polysilicon layer 2 ', Al on ceramic substrate 1
The electrode layers 3 'are sequentially formed.

Process Pattern the Al electrode layer 3 'to form a lead electrode
33 ', 33 ", 34', 34" are formed.

'While forming the heating resistor 21 by patterning, the width l ₂ of this time the heating portion and the vicinity thereof is wider, other parts lead electrode 33' processes the polysilicon layer 2, 33 ",
34 ', and the width l ₁ and Ho Isuzu heating element pattern to the same width of 34 "(step see FIG. 4 (B)).

As described above, since the heat generating portions of the heat generating resistors 21 and 22 and the vicinity thereof are widened, the polysilicon deficient portion 42 as shown in the process of FIG. 2 does not occur, and the resistance value of the heat generating resistors is reduced. A high-density thermal head with extremely small variations can be obtained.

[Problems to be solved by the invention]

However, when a thermal head having a heating resistor provided on a ceramic substrate is formed, a glaze glass layer as an accumulation layer may be partially formed mainly only in the heating portion and in the vicinity thereof.

In this case, the polysilicon layer remains at the edge portion of the glaze glass layer without being etched, thereby causing a disadvantage that the completed thermal heads are short-circuited.

This problem will be described with reference to FIGS. 5 (A) is a view for explaining the manufacturing process of the thermal head, FIG. 5 (B) is a sectional structural view corresponding to FIG. 5 (A), and FIG. (C) is also a top view.

 FIG. 6 is an enlarged view of a portion D in FIG. 5 (B).

Step A polysilicon layer 2 and an Al electrode layer 3 are formed on a ceramic substrate 1 having a partial glaze glass layer 5.

Step Electrode pattern etching is performed using a photoresist film to form lead electrodes 33 ', 33 ", 34', 34". Here, L ₁ is the width of the glaze glass layer 5.

Step heating portion and the width l ₂ in the vicinity thereof, etching of the heating element pattern wider than the width l ₁ of the other part, forming the heating resistor 21.

At this time, a cross-sectional view taken along the line BB 'in FIG. 5C of the process As is clear from FIG. 5B, the edge portion of the glaze glass layer 5 becomes a kind of concave portion and the polysilicon layer At the time of etching of No. 2, it remains without being etched. If the residual polysilicon layer 6 is large, a short circuit occurs between adjacent lead electrodes as shown in FIG. 5 (C).

The cause of the formation of the residual polysilicon layer 6 is that when the polysilicon layer 2 is formed on the ceramic substrate 1 having the partial glaze glass layer 5, as shown in FIG. since the resist thickness h ₁ of R, which is formed over the polysilicon layer 1 is formed thicker than the thickness h ₂ of the other part, the exposure of the resist, at the time of development, the remaining part of the resist R, When the polysilicon layer immediately below is etched using the remaining resist as a mask, it is considered that only a part of the polysilicon layer remains.

Therefore, an object of the present invention is to provide a high-precision, high-density thermal head with little variation in resistance value even when a thermal head is formed on a substrate having a partial glaze glass layer.

[Means for solving the problem]

In order to achieve the above object, according to the present invention, the width of the heating resistor is made larger than the width of the lead electrode in and around the heating portion, and the width of the heating resistor is almost equal to the width of the lead electrode in other portions. (4) The width of the lead electrode is formed to be wider at the end portion than at the width of the other lead electrodes.

This provides a thermal head that meets the demands for high precision and high density, has little resistance variation, and is unlikely to cause a short circuit between adjacent leads even when formed on a substrate with a partial glaze glass layer. can do.

〔Example〕

FIG. 1 shows an embodiment of the present invention. FIG. 1 (A) is an explanatory view of a manufacturing process of a thermal head according to an embodiment of the present invention.
FIG. 1B is a sectional view of the thermal head, and FIG.
Are the planes of the thermal head, which are shown in FIG.
3 shows the structure of the heating element portion of the thermal head corresponding to each of the steps.

In FIG. 1, the same reference numerals as those in FIG.

 An embodiment of the present invention will be described with reference to FIG.

Step A polysilicon layer 2 and an Al electrode layer 3 are sequentially formed on a ceramic substrate 1 partially having a glaze glass layer 5.

Step The first etching of the Al electrode layer 3 is performed. That is, as shown in FIG. 1 (C), electrode patterns 31 and 32 having unevenness facing each other are formed by etching using a photoresist film.

Process Figure 1 (C) of the process on Al electrode patterns 31 and 32
Using the photoresist pattern 7 shown by the dotted line in FIG.
The electrode layer is etched a second time, and the lead electrodes 33, 33 ',
34, 34 'are formed.

The shape of the lead electrode to be formed, as shown in FIG. 1 process according to the present invention (C), the width W ₂ in the vicinity of the end portion, including the vicinity of the edge of the glaze glass layer, the width of the other portions large have been designed from the W _3.

Step The polysilicon layer 2 is etched using the same photoresist pattern 7 as that used in the second etching of the electrode layer to form the heating resistors 21 and 22.

Here, according to the present invention, the heat generating portion and the width W ₁ in the vicinity of the heating resistor 21 and 22, wider than the width W ₃ of the lead electrodes 33 ... width W ₃ and Ho of Isuzu equal other heating resistor on it are wider design than the width W ₂ of the end portion of the lead electrode. That is
A _{W 1> W 2> W 3} .

By making the shape as in the present invention, the distance between the adjacent lead electrodes can be increased at the edge portion 5-1 of the glaze glass layer 5, but the distance between the heating resistors is different from that shown in FIG. It can be configured with high density without change.

As a result, even if the polysilicon layer remains at the edge of the glaze glass layer 5, the fear of short-circuiting between adjacent lead electrodes is greatly reduced.

In this embodiment, an example in which Al is used as the electrode layer has been described. However, the present invention is not limited to this, and it goes without saying that another electrode material such as W may be used.

〔The invention's effect〕

According to the present invention, since the heat generating portion of the heat generating resistor and its vicinity are wide, the defective portion 42 of the polysilicon layer as shown in the step of FIG. 2 does not occur. Therefore, a high-density thermal head with very little variation in the resistance value of the heating resistor can be obtained.

Further, since only the heat generating portion and its vicinity are wide, the design of the thermal head including the lead electrode portion is facilitated.

Further, by making the shape of the lead electrode as in the present invention, the distance between the adjacent lead electrodes can be increased without increasing the distance between the adjacent heat generating portions. As a result, even if a polysilicon layer as a heating resistor layer is provided on a substrate having a partially glaze glass layer, a short circuit between adjacent leads due to the remaining layer of polysilicon formed near the edge of the glaze glass layer is unlikely to occur. Was.

[Brief description of the drawings]

 FIG. 1 is an explanatory view of an embodiment of the present invention, FIG. 2 is a view showing a first conventional example, FIG. 3 is a view showing a second conventional example, and FIG. 4 is a third conventional example. FIG. 5, FIG. 5, and FIG. 6 are diagrams for explaining the problems of the conventional example. DESCRIPTION OF SYMBOLS 1 ... Ceramic substrate, 2 ... Polysilicon layer, 3 ... Electrode layer, 4 ... Photoresist film, 5 ... Glaze glass layer, 6 ... Residual polysilicon layer, 21,22 ... Heating resistor, 33,33 ', 34,34' ... Lead electrode.

Claims (2)

(57) [Claims] In a thermal head having a large number of heating resistors and lead electrodes provided on a substrate, the width of the heating resistor is made larger than the width of the lead electrode in a heating portion and in the vicinity thereof, and other portions are formed. A thermal head characterized in that the width of the heating resistor is made substantially equal to the width of the lead electrode, and the width near the end of the lead electrode is formed wider than the width of the lead electrode in other parts. 2. A method for manufacturing a thermal head, comprising the steps of providing a heating resistor layer and a lead electrode layer on a substrate, wherein a part of the lead electrode layer is etched to form lead electrodes having unevenness facing each other. A step of forming a pattern, a step of etching the lead electrode pattern again, and a step of forming a lead electrode pattern in which the width in the vicinity of the end of the lead electrode is wider than the width of the lead electrode in other portions; The heating element layer pattern is etched so that the width of the heating element layer is wider than the lead electrode width in and around the heating part of the heating resistor, and is almost equal to the lead electrode width in other parts. Forming a thermal head.