JP3041352B2 - 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 having a protective layer for protecting a heating element and electrodes around the heating element from wear and the like.

[0002]

2. Description of the Related Art As shown in the sectional view of FIG. 7, a conventional thermal head is provided with a heating element 3 and a protective layer 7 covering an electrode 4 connected to the heating element. An overlying coating layer 20 made of an epoxy resin or the like was provided on the protective layer.

In the production of such a thermal head, the protective layer is formed by a method such as sputtering or CVD using an insulating material typified by a silicon compound.
At this time, as shown in the cross-sectional view of FIG. 8, it is common to form a film by covering a portion not covered with the protective layer 7 with a mask member 11 made of metal or ceramic.

[0004]

However, when a mask is used in this way, there occurs a problem that the mask member 11 and the electrode 4 of the thermal head rub against each other or the electrode is scraped off at a corner of the mask member. There has been a problem that the energization reliability of the electrodes is reduced and the production yield is reduced.
In particular, aluminum or copper is often used as an electrode material, and these problems are serious because these metals are soft and easily damaged.

[0005]

As a means for solving the problems, the present applicant has disclosed a technique for forming first and second protective layers in Japanese Patent Application Laid-Open No. Hei 3-190762, In order to solve the above-mentioned problem more reliably, the most characteristic feature is that a plating layer is formed on an electrode before forming a protection layer. Is carried out to form a protective layer.

[0006]

By providing a plating layer below the protective layer, even when the corner of the mask member hits the electrode surface during the formation of the protective layer, it does not come into direct contact with the electrode. When nickel plating, which is usually used as a monk, is applied, scratches due to external factors are prevented from being caused in the electrodes due to the hardness of nickel, and the problems of lowering the energization reliability of the electrodes and lowering the production yield are solved.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a thermal head manufactured by the manufacturing method of the present invention, and FIG. 6 is an enlarged sectional view of a main part of the thermal head.

A glaze layer 2 is provided on a substrate 1 made of alumina ceramic or the like, and a heating resistor layer and a conductor layer are formed as a thin film. These are patterned to form a heating element 3 and an electrode 4. Next, except for at least the connection portion 5 between the peripheral portion of the heating element 3 and the external circuit and the like, a plating layer 8 having a nickel base and a gold surface is formed. Thereafter, a protective layer 7 is formed on the peripheral surface of the heating element 3 so that at least the edge 6 of the protective layer covers the plating layer 8. Reference numeral 9 denotes a plating layer on a connection terminal for electrical connection with an external circuit formed simultaneously with the plating layer. Reference numeral 20 denotes a resin layer that covers a portion where the plating layer and the protective film 7 overlap with each other and further covers an exposed portion of the electrode 4.

As the electrode material, gold, copper, aluminum, an alloy of these metals, or the like is used. As the protective layer material having abrasion resistance and a function of preventing oxidation of the heating element, oxides, nitrides, and carbides of Si are used,
It is formed by a method such as sputtering or CVD.

On the other hand, with respect to the plating layers 8 and 9, nickel plating is firstly formed to a thickness of 1 to 3 μm by electroless plating or electrolytic plating, and gold plating is further thinly formed. In the formation of the protective layer, both the sputtering and the CVD require a high work temperature and a film thickness of usually about 5 μm, so that the film formation time is long. However, since the plating layer is a metal having a high melting point, sufficient heat resistance is obtained. There is. JP-A-3-1907 already disclosed by the present applicant.
In Japanese Patent No. 62, low-melting glass, polyimide or the like is formed at the edge of the protective layer. However, the plating layer in the present invention is thermally stable and does not need to worry about the process temperature.

In this plating step, a plating layer step usually performed on connection terminals for electrical connection with an external circuit to improve the reliability of the connection portion can be used as it is, and a new process is performed. There is also an advantage that it is not necessary. However, attention should be paid to the adhesion between the plating layer and the protective layer when a protective film is formed on the gold plating layer by sputtering or CVD. In other words, it is difficult to form an insulator such as a silicon compound on the gold surface with a strong adhesion,
The conditions for forming the protective layer are restricted. When the adhesion is not sufficient, the thermal head may cause a problem in environmental resistance.

In this embodiment, as described above, the portion where the plating layer and the protective film overlap is covered with the resin 20, and this resin layer is provided to cover and protect the exposed portions of the electrodes even in the thermal head having the conventional structure. No new process is required. Therefore, when the adhesion is obtained,
The resin layer 20 at the portion where the plating layer and the protective layer overlap may not be provided as long as the adhesion does not matter.

FIG. 4 is a sectional view of a step of forming a protective layer of the thermal head shown in FIG. 1. Reference numeral 11 denotes a mask for covering a portion where the protective layer is not formed. This mask 11
It is made of metal such as stainless steel. In a so-called edge type thermal head in which the heating element 3 is provided near the end of the substrate 1, the thermal head substrate may be stacked in a roof tile type, and the thermal head itself may be used as a mask.

When the mask 11 is set as shown in FIG.
This mask does not directly contact the electrode 4 by the plating layer 8, and the hard plating layer 8 protects the soft electrode even if it comes into contact with and rubs against the plating layer. Even if the plating layer 8 is scratched by the mask 11, scratches due to interference with the mask in a normal process do not cause any problem in function and reliability. The present inventors formed a nickel plating thickness of 0.5 μm on an electrode made of pure aluminum, which is the softest among the commonly used electrode materials, and investigated the occurrence of scratches, but found no problem.

FIG. 2 shows an application example of the present invention in a serial thermal head, and is a plan view of the thermal head. The plating layer 8 below the protective film edge portion and the plating layer 9 at the connection terminal portion are not separated but are integrally connected.

FIG. 3 shows an application example of the present invention in an end face type thermal head, in which plating layers 8 are formed on both sides of the thermal head. FIG. 5 is a cross-sectional view of the end-face type thermal head when the protective layer is formed. Even if the thermal heads are arranged in an overlapping manner, the plating layer 8 causes the electrode 4 to be defective due to scratches even if the thermal heads rub against each other. Does not occur.

[0017]

As described above, according to the present invention, the formation of a protective layer having a wear-resistant and oxidation-resistant function can prevent film adhesion and electrode flaws,
By improving the ease of manufacture and expanding the effective area of the protective layer, there are various effects such as providing a thermal head having excellent quality and reliability at low cost.

[Brief description of the drawings]

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

FIG. 2 is a plan view of a thermal head according to another embodiment of the present invention.

FIG. 3 is a sectional view of a thermal head according to another embodiment of the present invention.

FIG. 4 is a sectional view of a thermal head when a protective layer is formed in the present invention.

FIG. 5 is a sectional view of a thermal head when a protective layer is formed in another embodiment of the present invention.

FIG. 6 is an enlarged sectional view of a main part of the thermal head of the present invention.

FIG. 7 is a sectional view of a conventional thermal head.

FIG. 8 is a cross-sectional view of a conventional thermal head when a protective layer is formed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 3 Heating element 4,13,14 Electrode 6 Edge of protective layer 7 Protective layer 8,9 Plating layer 11 Mask member 20 Resin layer

Continuation of the front page (56) References JP-A-3-190762 (JP, A) JP-A-62-149461 (JP, A) JP-A-59-29172 (JP, A) JP-A-62-119058 (JP, A) JP-A-61-297160 (JP, A) JP-A-5-169703 (JP, A) JP-A-4-52056 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B41J 2/335

Claims (4)

(57) [Claims] A heating element, an electrode connected to the heating element, a surface of the heating element, and a part of a surface of the electrode;
A method for manufacturing a thermal head having a protective layer having wear resistance and oxidation resistance, comprising: forming a plating layer on a surface of a selected area of an electrode except for at least a periphery of the heating element; A method for manufacturing a thermal head, comprising forming a protective layer so that an edge portion is located. 2. A plating layer is formed on a terminal portion of a thermal head substrate for making an electrical connection with an external circuit, and the same plating layer as the plating layer is formed on an edge portion of the protective layer in a lower layer. The method for manufacturing a thermal head according to claim 1, wherein: 3. The method according to claim 1, wherein the plating layer is a layer composed of at least nickel. 4. The method for manufacturing a thermal head according to claim 1, wherein a portion where the plating layer and the protective layer overlap at an edge of the protective layer is covered with a resin.