JPS5929173A - Thermal head - Google Patents

Abstract

PURPOSE:To obtain a thermal head made inexpensive by reducing the amount of gold to be used in high yield, by constituting the electrode of the thermal head from a laminate consisting of a chromium layer, a copper layer formed thereon by a vapor deposition method and a gold layer formed on said copper layer by a vapor deposition method. CONSTITUTION:A heat generating resistance layer 2 comprising a tantalum nitride layer 2 is formed on a ceramic substrate 1 having a glaze glass layer on the surface thereof in a pattern form and pattern electrode 10 is formed on the upper surface of the part of said heat generating resistance layer 2. This electrode 10 is formed of a three-layered structure consisting of a chromium layer with a thickness of 300-3,000Angstrom , a copper vapor deposition layer 12 with a thickness of 300Angstrom -3mum and a gold vapor deposition layer with a thickness of about 1,000Angstrom . In the next step, an oxidation inhibiting layer 7 comprising silicon dioxide or the like and an anti-wear layer 8 comprising tantalum peroxide or the like are applied to the exposed part of the heat generating resistance layer 2 and the end part of the electrode 10 adjacent thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is used in printers, facsimile machines, etc., and converts information sent as electrical signals into letters and letters on thermal recording paper.
Regarding the circuit 1-゛ to be converted into a symbol or image,
Shi [! The present invention relates to the structure of a thin film type thermal head 1-' formed using tAlc manufacturing technology.

The structure of a conventional thermal head is shown in FIG.

■ is a thread plate made of ceramic or the like with a glazed glass layer on the surface - 〇, a heating resistor pattern made of a nitride tank layer k is formed on the top surface of the substrate, and the connection part of the heating resistor pattern] Electrode pattern on two sides 3 is formed. The electrode pattern 3 has a multilayer structure including a nichrome layer 4, a gold layer 5, and a gold plating layer 6. The nichrome layer 4 includes a tantalum nitride layer and a gold layer 5. The gold plating layer 6 is not only a conductive layer as the main and retreating part of the electrode, but also serves as a conductor layer to strengthen the adhesion between the electrode and the oxidation prevention film and the wear layer formed on the surface 4. RTL 1lil-C is formed to make the surface rough. Here, the portion of the heating resistor pattern 2 sandwiched between the four poles 3 is a heating portion. 17 is a heavy oxidation prevention film made of a sulfur dioxide sputtered film provided to prevent an increase in resistance due to oxidation of the heating resistor; 8
is a wear-resistant layer made of a tantalum pentoxide layer provided to protect the heating resistor from friction with the heat-sensitive recording paper.

Formation of such heating resistor patterns and electrode patterns is performed using photolithography technology.

At this time, since nichrome is an alloy, the etching of the nichrome layer 4 tends to result in overetching or side etching, and the electrode is likely to peel off from there. Further, there is also the problem that it is difficult to uniformly form the alloy layer by vapor deposition, sputtering, etc., and as a result, the structure having the nichrome layer has the problem of lowering the product yield.

Furthermore, in the configuration shown in FIG. 1, since the gold layer 5 is in contact with the nichrome layer 4, chromium diffuses into the gold layer 5, so that the total thickness of the gold layer 5 and the gold plating layer 6 is at least 0.5~. 1
71m is required. Usually, the thickness of the gold layer 5 is about (), 4
Since the thickness of the gold plating layer 6 is set to about 0.8 μm, one layer of gold is often used, which causes the zarple head to be expensive.

In view of the above problems, the present invention improves the yield by 4.
The purpose of this invention is to provide a chromium layer that can be manufactured at a low cost, with an electrode formed by a chromium layer formed by a vapor deposition method or a sputtering method, and a chromium layer formed by a vapor deposition method on top of the chromium layer formed by a vapor deposition method. By creating a multilayer structure of a copper layer and a gold layer formed on top of it by a vapor deposition method,
This aims to achieve the second objective.

Below, embodiments of the present invention will be described.

FIG. 2 shows a cross-sectional structure of one embodiment, and 1 and 2 are the same substrate and heating resistor layer as in FIG. 1. l.

is an electrode corresponding to the electrode 3 in FIG.
Copper deposited layer 12 with a thickness of 00λ to 3 μn1, and 1000
It is distinctive in that it has a three-layer structure of around six gold vapor deposited layers 13. 7 and 8 are the same oxidation-preventing IJ films and wear-resistant layer as in FIG.

In the electrode of this example, the chromium layer 11 not only acts as a conductor layer, but also aims to strengthen the (:1s force) between the copper layer 12 and the heating resistor layer 2. 11'' The second copper layer 12 acts as a conductor layer to flow current to the heating resistor pattern, and the gold layer 13 of the copper layer 121 in Φ acts as a conductor layer and prevents the copper layer 12 from being oxidized. It also has a preventive effect.

Next, a process of forming an electrode pattern and a heating resistor pattern in one embodiment will be described. First, glazed ceramic nail plate 1. A tantalum nitride layer 2 is formed on the tantalum nitride layer 2 to a thickness of about 25011A by sputtering, and a chromium layer 11 is formed to a thickness of about 15nOA by vapor deposition on the tantalum nitride layer 2. 1]-1: Copper layer 1
2 is formed to a thickness of about 1.57 on by vapor deposition, and then a gold layer 13 is formed on the copper layer 12'' to a thickness of about 100+ by vapor deposition.
'IA was formed.

Next is the gold layer] Apply a photoresist layer to -L in step 3, and then potresise it! Layer] Second, a photomask for an electrode pattern was applied, exposed, and developed to form a photoresist pattern.

Using this photoresist pattern as a mask, the multilayer electrode layer 10 was etched one after the other.

That is, first, the gold layer 13 is etched by immersion in an iodine potassium iodide solution, the copper layer 12 is etched by immersion in a ferric chloride solution, and then a mixture of potassium ferricyanide and potassium hydroxide is added to J. The chromium layer 11 was etched by dipping it in a liquid.

Next, after removing the remaining photoresist pattern with a stripping solution, apply photoresist again. Next, apply a photomask for the heating resistor pattern, expose and develop the photoresist pattern. formed a pattern. Next, it contains nitric acid and hydrofluoric acid in a ratio of 3:1? The tantalum nitride layer 2 was immersed in nitric acid and etched using the photoresist pattern as a mask to form a heating resistor pattern. After the edge puffing, the remaining photoresist pattern was peeled off using a stripping solution.

Next, heat treatment was performed at 300°C for 7 hours to stabilize the heat generating resistor pattern 2, and then a mask was placed over the heat generating part of the heat generating resistor pattern so that the region including a part of the pattern was opened, and sputtering was performed. A silicon dioxide layer 7 is formed to a thickness of about 1.57 zm by a method, and a tantalum oxide layer 8 is formed to a thickness of about 57 nl by a sputtering method with the mask still covered.Finally, the mask is removed. In this way, the zaple hem 1-' shown in FIG. 2 was formed.

[,S, As detailed above, the present invention uses a chromium layer as a layer to strengthen the 01 adhesion between the heating resistor layer and the electrode, so the chromium layer is smaller than the conventional structure using an alloy layer. Formation is facilitated, there is no overetching during etching, and a definite electrode pattern edge can therefore be formed, which has the effect of improving product quality and yield. Furthermore, in the present invention, since the main part of the electrode is made of copper, the amount of gold used is, for example, 115 to 1/10.
This, combined with the "two-layer yield ratio", is effective in reducing product costs. Furthermore, since the copper layer 12 and the □□□ layer 13 of the present invention are both formed by vapor deposition 11, the surface is smooth and the adhesion of the phase 4 is strong. Even when the tourmaline material was changed from the conventional one mainly made of gold to the one of the present invention mainly made of copper, no change in the characteristics of the thermal head was observed.

In the thin film thermal head according to the present invention, the heating resistor pattern forming layer is limited to a tantalum nitride layer as in this embodiment, a two-layer film of silicon dioxide and tantalum,
A two-layer film of silicon and tantalum, a nichrome layer, a nesa film, etc. are also known. 1 Also, as a protective film for a heating resistor, an oxidation prevention film made of silicon dioxide and a tantalum pentoxide film as shown in this example are used. Not only those with a two-layer structure of the wear-resistant layer, but also those with a Φ layer structure made of silicon carbide or alumina are known. The present invention has a feature in the electrode structure -C, and it is clear that even if the other components are replaced with the known two-layer structure, the same effect as in the above embodiment can be achieved. Therefore, it is easily understood that an invention in which structures other than electrodes are replaced, such as a two-layer structure, falls within the scope of the present invention. It is clear that the methods for forming the heating resistor layer, the electrode layer, and the protective film are not limited to those described in the embodiments, and may be carried out by appropriately combining known thin film forming techniques.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional thermal head, and FIG. 2 is a sectional view showing an embodiment of the present invention. ■...Foil plate, 2...Heating resistor layer, 3, 10...
Electrode, 7... Oxidation prevention 11. Membrane, 8... Wear-resistant layer, 1
1...Chromium layer, 12...Copper vapor deposition layer, 13...Gold vapor deposition layer. Talent! ``W1 Applicant Legal Company Ricoh Co., Ltd.'' Ao 111 2 other people Fig. 1 Fig. 2

Claims (1)

[Claims] A heating resistor pattern is formed on +11JiQ board 1-,
An electric fence pattern is formed on the upper surface of the connection part of the heating resistor pattern, and the electric fence pattern is formed on the heating part of the heating resistor pattern and on the surface of a part of the electrode pattern through an anti-oxidation film or directly. In a thin film type thermal head in which a ml wear layer is formed,
4, a copper layer formed by vapor deposition on two sides of the chromium layer, and a gold layer formed by vapor deposition on two sides of the copper layer. thermal head.