JP3180980B2 - Manufacturing method of 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 method for manufacturing a thermal head used for a facsimile, an image recording apparatus, and the like. More specifically, a plurality of thermal head substrates are simultaneously obtained from a single electrically insulating substrate body. The present invention relates to a method for manufacturing a thermal head.

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS. 3 and 4, a thermal head substrate is made of an electrically insulating substrate 6 made of alumina ceramics or the like smoothed by providing a glaze layer 5 at a predetermined position on the surface. The heating resistor layer 7 is formed on the entire upper surface.
And a conductive layer 8 are sequentially formed, and then the photolithography technique is used to partially etch the conductive layer 8 to thereby connect the terminal electrode 3 along one side edge of the electrically insulating substrate 6 and the other. The common electrode 4 is provided along the side edges of the individual electrodes 9 and the individual electrodes 9 and the heat generating portions 10 are provided between the terminal electrode 3 and the common electrode 4.
Are formed in a predetermined pattern, and a protective layer 11 made of silicon nitride or the like is formed thereon. Finally, a driving IC element 12 is placed between the individual electrode 9 and the terminal electrode 3 by a face-down method such as a solder bump method. It has been manufactured by mounting by bonding and covering the driving IC element 12 with the protective resin 14.

[0003] In the production of such a thermal head substrate, it is inefficient to produce one thermal head substrate at a time. Therefore, one electric insulating substrate body is divided into a plurality of sections and each section is divided into a plurality of sections. It has been proposed that a circuit pattern and a heat generating portion 10 are respectively formed, and thereafter, a plurality of thermal head substrates are simultaneously obtained by dividing an electrically insulating substrate body into respective sections, as disclosed in Japanese Patent Publication No. 4-17796. Discloses a prior art relating to the arrangement of circuit patterns when a plurality of thermal head substrates are simultaneously obtained from one electrically insulating substrate body.

According to the publication, as shown in FIG. 5 (a), an electrically insulating substrate body is divided into three sections, and circuit patterns X, Y and Z are formed in each section. It is described that the X terminal electrode 3 is arranged to face the common electrode 4 of the circuit pattern Y, and the terminal electrode 3 of the circuit pattern Y is arranged to face the common electrode 4 of the circuit pattern Z. Insulating substrate body 1
Is divided into each section, so that three thermal head substrates can be obtained at the same time.

[0005] With the spread of home-use FAX in recent thermal heads, there has been a strong demand for cost reduction and miniaturization. For this reason, when a thermal head substrate is manufactured by the above-described manufacturing method. , FIG. 5 (b)
As shown in FIG.
Needs to be reduced to, for example, about 0.5 mm to reduce the depth dimension 15 of the electrically insulating substrate 6.

However, the interval 16 is set to 0.5 mm
If the width is reduced to such an extent, the division lines 2a and 2b may deviate from the ideal position due to the influence of the accuracy of the set position of the mask on the electrically insulating substrate body 1 in the photolithography process, and the like. When dividing the body 1,
If the division lines 2a and 2b deviate from the ideal positions,
As shown in FIGS. 5C and 5D, the common electrode 4 of the adjacent circuit pattern Y remains in a band shape at a position outside the terminal electrode 3 of the electrically insulating substrate 6 on which the circuit pattern X is formed. As a result, when the flexible wiring board is press-welded to the terminal electrode 3 of the thermal head substrate, as shown in FIG. 4 had the disadvantage of causing a short circuit.

As described above, in the prior art, as the size of the thermal head substrate is reduced, short-circuit failure is more likely to occur, and the yield rate is reduced. Therefore, the thermal head substrate is reduced in size for cost reduction. On one hand, the results were inconsistent.

The problem described above is a problem that occurs regardless of whether the conductive layer is thin or thick.

[0009]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above problems, and a method of manufacturing a thermal head according to the present invention is directed to a method of dividing an electrically insulating substrate body into a plurality of sections. Forming a circuit pattern including a common electrode, an individual electrode and a terminal electrode, and a heat generating portion interposed between the common electrode and the individual electrode, and thereafter dividing the electric insulating substrate body into respective sections. In the method for manufacturing a thermal head in which a flexible wiring substrate is pressure-welded to a plurality of thermal head substrates obtained by the method described above, each circuit pattern formed in each section of the electrically insulating substrate body is provided with a terminal electrode and a common electrode. Are disposed so as to face the terminal electrode and the common electrode of the circuit pattern of the adjacent section, and a reinforcing electrode is interposed between the common electrode and the upper surface of the electrically insulating substrate body in a film form. It is characterized in that to.

[0010]

When a plurality of thermal head substrates are simultaneously obtained from a single electrically insulating substrate element, a circuit pattern corresponding to the plurality of thermal head substrates is arranged as in claim 1, so that the electrical insulation in the photolithography process is achieved. Due to the influence of the mask setting position accuracy on the conductive substrate body, the division line may deviate from the ideal position, and the division line may touch the circuit pattern of the adjacent section. The common electrode of the adjacent circuit pattern never remains in a strip shape at a position outside of the flexible wiring board at the time of press-welding the wiring of the flexible wiring board to the terminal electrode of the thermal head board. The problem that the wires are short-circuited does not occur.

[0011] Even if the divided lines deviate from the ideal positions, even if some of the terminal electrodes of the circuit pattern adjacent to the position outside the terminal electrodes of the thermal head substrate remain, the remaining terminal electrodes are individually formed. Therefore, when the wires of the flexible wiring board are press-welded to the terminal electrodes of the thermal head substrate, there is no problem that the wires of the flexible wiring board are short-circuited.

Moreover, in this case, since the reinforcing electrode is interposed in a film form between the common electrode and the upper surface of the electrically insulating substrate body, a concave portion or the like for accommodating the reinforcing electrode is formed on the surface of the electrically insulating substrate body. No extra process is required for the formation, and the thickness of the electrically insulating substrate body without any concave portions is substantially constant, so that the mechanical strength of the electrically insulating substrate body is kept high. As a result, a situation in which the electrically insulating substrate body is damaged during the manufacturing process is effectively prevented, thereby dramatically improving the productivity of the thermal head.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. (Example 1) FIG. 3 is a cross-sectional view showing the structure of a thermal head substrate, and FIG. 4 is a plan view of the thermal head substrate.
A circuit pattern including the terminal electrode 3, the common electrode 4, and the individual electrode 9 and a heat generating portion 10 interposed between the individual electrode 9 and the common electrode 4 are formed in a predetermined pattern thereon.

In order to manufacture a thermal head substrate having such a structure by the manufacturing method of the present invention, (1) first, a partial glaze layer 5 corresponding to a plurality of thermal head substrates is provided on a predetermined region of the upper surface of an electrically insulating substrate body.
(Height: about 50 μm, width: about 1 mm) so as to form an arc-shaped cross section.

The electrically insulating substrate body is made of alumina ceramics or the like, and a ceramic raw material powder such as magnesia is mixed with an appropriate organic solvent and a solvent to form a slurry. A ceramic green sheet is formed by employing a roll method or the like, and thereafter, the ceramic green sheet is punched into a predetermined shape and fired at a high temperature.

The partial glaze layer 5 deposited on the electrically insulating substrate body is made of glass or the like. A glass paste obtained by adding a suitable organic solvent and a solvent to glass powder is mixed with an electrically insulating substrate. The upper surface of the element body is applied by employing a conventionally known screen printing method or the like, and then is baked at a predetermined temperature to cover the upper surface of the electrically insulating substrate body 1 so that the cross section forms an arc shape. Be worn.

(2) Next, on the electrically insulating substrate body and the partial glaze layer 5, a heating resistor layer 7 (thickness: 200 to 1000 mm) made of tantalum nitride or the like and a conductive layer made of aluminum or copper or the like 8 (thickness: about 1 μm).

The heating resistor layer 7 and the conductive layer 8 are respectively applied with a predetermined thickness on the electrically insulating substrate body and the partial glaze layer 5 by employing a conventionally known sputtering method or the like.

(3) Next, the conductive layer 8 is processed into a predetermined pattern by a photolithography process to divide the electrically insulating substrate body into a plurality of sections,
A circuit pattern including the common electrode 4, the individual electrode 9, and the terminal electrode 3 and a heat generating portion 10 interposed between the common electrode 4 and the individual electrode 9 are formed.

At this time, each circuit pattern formed in each section of the electrically insulating substrate body is shown in FIGS. 1 (a) to 1 (c).
As shown in the figure, the terminal electrode 3 and the common electrode 4 are formed so as to face the terminal electrode 3 and the common electrode 4 of the circuit pattern of the adjacent section.

The circuit pattern and the heat generating portion 10 are formed by partially etching the conductive layer 8 by using a conventionally well-known photolithography technique, so that the terminal of the circuit pattern of the section where the terminal electrode 3 and the common electrode 4 are adjacent to each other is formed. It is formed so as to face the electrode 3 and the common electrode 4.

Each circuit pattern formed in each section of the electrically insulating substrate body 1 has its terminal electrode 3 and common electrode 4 opposed to the terminal electrode 3 and common electrode 4 of the circuit pattern in the adjacent section. Therefore, the division line 2 is shifted from an ideal position due to the influence of the accuracy of the mask setting position on the electrically insulating substrate body 1 in the photolithography process, and the division line 2 is applied to the circuit pattern of the adjacent section. Even in such a case, the common electrode 4 of the adjacent circuit pattern does not remain in a strip shape at a position outside the terminal electrode 3 of the thermal head substrate, and the terminal electrode 3 of the thermal head substrate is flexible. When the wires of the flexible wiring board are press-welded, there is no problem that the wires of the flexible wiring board are short-circuited.

Further, since the division line 2 deviates from the ideal position, the terminal electrode 3 of the adjacent circuit pattern is located at a position outside the terminal electrode 3 of the thermal head substrate.
Even if some of the terminal electrodes 3 remain, the remaining terminal electrodes 3 are independent of each other.
When the wirings of the flexible wiring board are welded by pressure welding, there is no problem that the wirings of the flexible wiring board are short-circuited.

(4) Next, a protective layer 11 is deposited on the upper surface of the circuit pattern. The protective layer 11 is made of silicon nitride, sialon, or the like, and is formed with a thickness of about 4 μm on the upper surface of the heating resistor layer 7 or the like by a thin film technique such as a sputtering method.

(5) Next, an external force is applied to a predetermined position of the electrically insulating substrate body 1 to divide the electrically insulating substrate body 1 into a plurality of thermal head substrates.

In this case, each circuit pattern formed in each section of the electrically insulating substrate body 1 has its terminal electrode 3 and common electrode 4 facing the terminal electrode 3 and common electrode 4 of the circuit pattern in the adjacent section. Therefore, the division line 2 is deviated from an ideal position due to the influence of the accuracy of the setting position of the mask on the electrically insulating substrate body 1 in the photolithography process, and the circuit pattern of the division line adjacent to the division line 2 However, the common electrode 4 of the adjacent circuit pattern never remains in a strip shape at a position outside the terminal electrode 3 of the thermal head substrate. When the wires of the flexible wiring board are press-welded, there is no problem that the wires of the flexible wiring board are short-circuited.

Further, since the division line 2 deviates from the ideal position, the terminal electrode 3 of the adjacent circuit pattern is located at a position outside the terminal electrode 3 of the thermal head substrate.
Even if some of the terminal electrodes 3 remain, the remaining terminal electrodes 3 are independent of each other.
When the wirings of the flexible wiring board are welded by pressure welding, there is no problem that the wirings of the flexible wiring board are short-circuited.

(6) Finally, the driving IC elements 12 are mounted between the individual electrodes 9 and the terminal electrodes 3 of each thermal head substrate via a brazing material such as solder, and the driving IC elements 12 are protected by a protective resin. Cover with 14.

The driving IC element 12 is mounted between the individual electrode 9 and the terminal electrode 3 of each thermal head by face-down bonding such as a solder bump method. Thereafter, the driving IC element 12 is replaced with a conventionally known thick film. The thermal head substrate is completed by applying the technology and covering with the protective resin 14.

A reinforcing electrode 13 made of silver or the like is interposed between the common electrode 4 and the upper surface of the electrically insulating substrate body 1 in a film shape with a predetermined thickness. This reinforcing electrode 13
Is provided below the common electrode 4 and the heating resistor layer 7 to electrically reinforce the common electrode 4. The electric resistance of the common electrode 4 is increased by the reinforcing electrode 13, for example, per unit length. It can be as small as 1 × 10 ⁻³ Ω / mm or less, thereby effectively preventing a voltage drop on the common electrode 4.

The reinforcing electrode 13 is formed by applying a conductive paste such as a silver paste to a predetermined region of the upper surface of the electrically insulating substrate body 1 by a conventionally known screen printing or the like.
For example, the conductive paste is baked at a temperature of 600 ° C. for a baking time of 5 ° C.
It is formed by firing under conditions of up to 30 minutes.

Since the reinforcing electrode 13 is interposed in the form of a film between the common electrode 4 and the upper surface of the electrically insulating substrate body 1, the reinforcing electrode 13 reinforces the surface of the electrically insulating substrate body 1. An extra process for forming a concave portion for accommodating the electrode is unnecessary, and the thickness of the electrically insulating substrate body 1 having no concave portion is substantially constant. The mechanical strength of the thermal insulating head 1 is maintained high, and the situation that the electrically insulating substrate body 1 is broken during the manufacturing process is effectively prevented, thereby greatly improving the productivity of the thermal head.

While the occurrence rate of short-circuit failure is about 20% in the conventional manufacturing method, the occurrence of short-circuit failure can be eliminated in the manufacturing method of the present invention, and the mask used in the photolithography process can be eliminated. It can be dealt with simply by changing to a predetermined pattern. Therefore, there is no particular cost increase in implementing the present invention.

In this embodiment, the circuit patterns corresponding to the plurality of thermal head substrates are shown in FIGS.
Although they were arranged as shown in (c), in addition to these arrangements,
The same circuit pattern may be further adjacent to the short side of the pattern, so that a larger number of thermal head substrates can be obtained from one electric insulating substrate body 1 at a time.

(Embodiment 2) Each circuit pattern formed in each section of the electrically insulating substrate body 1 is left-right symmetrical, and its terminal electrodes 3 are adjacent to each other as shown in FIGS. 2 (a) and 2 (b). It faces the terminal electrode 3 of the circuit pattern of the section to be formed and is formed continuously. Other manufacturing methods are the same as in the first embodiment.

In this case, it is possible to eliminate the occurrence of short-circuit defects and to make the wiring area uniform by making the gold plating application area for forming the terminals the same area, thereby reducing the printing density on thermal paper or the like. It can be uniform.

The present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the scope of the present invention. Although the layers are formed by the thin film technology, the heating resistor layer and the conductor layer may be formed by the thick film technology, and the same effect as in the above embodiment can be obtained by forming the heating resistor layer and the conductor layer by the thick film technology. Can be obtained.

[0038]

According to the method of manufacturing a thermal head according to the present invention, each circuit pattern formed in each section of the electrically insulating substrate body has a terminal electrode and a common electrode, each of which has a terminal of the circuit pattern in the adjacent section. Since the electrodes are formed so as to face the electrodes and the common electrode, the division line deviates from the ideal position due to the influence of the accuracy of the setting position of the mask on the electrically insulating substrate body in the photolithography process, and the division lines are adjacent to each other. Even if the circuit pattern of the thermal head substrate is affected, the common electrode of the adjacent circuit pattern does not remain in a strip shape at any position outside the terminal electrode of the thermal head substrate. When the wires of the flexible wiring board are press-welded, there is no problem that the wires of the flexible wiring board are short-circuited.

Further, according to the method of manufacturing a thermal head of the present invention, the terminal line of the adjacent circuit pattern is located at a position outside the terminal electrode of the thermal head substrate because the division line deviates from the ideal position. Even if a part of the wiring remains, the remaining terminal electrodes are independent of each other. Therefore, when the wiring of the flexible wiring board is press-welded to the terminal electrode of the thermal head substrate, the wirings of the flexible wiring board are connected to each other. The problem of short circuit does not occur.

Further, according to the method of manufacturing a thermal head of the present invention, since the reinforcing electrode is interposed between the common electrode and the upper surface of the electrically insulating substrate body in a film form, the surface of the electrically insulating substrate body can be formed. No extra process is required to form a recess or the like for accommodating the reinforcing electrode, and since the thickness of the electrically insulating substrate body having no recess or the like is substantially constant,
The mechanical strength of the electrically insulating substrate body is maintained at a high level, effectively preventing the electrically insulating substrate body from being damaged during the manufacturing process, thereby dramatically improving the productivity of the thermal head. .

Further, according to the method of manufacturing a thermal head of the present invention, each circuit pattern formed in each section of the electrically insulating substrate body is opposed to the terminal electrode of the circuit pattern in an adjacent section of the adjacent section. When the electrical insulating substrate body is divided, there is no residual conductor independent of the terminal electrodes, and the flexible wiring substrate is press-welded to the thermal head substrate. In this case, it is possible to reliably prevent a short circuit between the wirings of the flexible wiring board, and when performing gold plating for a certain distance from the end of the electrically insulating substrate to form the terminal portion, the plating area is reduced between the heads. As a result, the wiring resistance can be made uniform.

As described above, in the method of manufacturing a thermal head according to the present invention, the thermal head can be manufactured in a small size with a high yield, so that a low-cost thermal head can be provided, and a mask used in a photolithography process can be provided in a predetermined manner. It can be dealt with simply by changing the pattern. Therefore, there is no particular cost increase in implementing the present invention.

[Brief description of the drawings]

FIGS. 1A to 1C are views showing a first embodiment of the manufacturing method of the present invention.

FIG. 2A is a view showing a second embodiment of the manufacturing method of the present invention, and FIG. 2B is an enlarged view of a portion A of FIG.

FIG. 3 is a cross-sectional view illustrating a structure of a thermal head substrate.

FIG. 4 is a plan view of a thermal head substrate.

FIGS. 5A to 5D are diagrams showing a conventional method for manufacturing a thermal head.

FIG. 6 is a partially enlarged view of a conventional thermal head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric insulating substrate body, 2 ... Dividing line, 3
... terminal electrode, 4 ... common electrode, 8 ... conductive layer,
Reference numeral 9: individual electrode, 10: heating section, 11: protective layer, 12: driving IC element, 13: reinforcing electrode,
18 flexible wiring board, 18a wiring

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/335 B41J 2/345

Claims (2)

(57) [Claims] An electric insulating substrate body is divided into a plurality of sections, and each section includes a circuit pattern including a common electrode, an individual electrode, and a terminal electrode, and a heating section interposed between the common electrode and the individual electrodes. Each formed, and thereafter, a plurality of pieces obtained by dividing the electric insulating substrate body into respective sections.
Pressure welding of flexible wiring board to thermal head board
That in the manufacturing method for a thermal head, each circuit pattern formed on each section of the electrically insulating substrate body, so that the terminal electrodes and a common electrode facing the terminal electrode and the common electrode of a circuit pattern sections adjacent With the arrangement
Between the common electrode and the upper surface of the electrically insulating substrate body.
A method for manufacturing a thermal head, wherein a reinforcing electrode is interposed in the form of a film therebetween . 2. A circuit pattern formed in each section of the electrically insulating substrate body, and a terminal electrode thereof is formed to be continuous with a terminal electrode of a circuit pattern in an adjacent section. Item 2. The method for manufacturing a thermal head according to Item 1.