JPS63317357A - Thermal head - Google Patents

Abstract

PURPOSE:To obtain a thermal head with a simple structure, and high connection reliability at low manufacturing cost by using molybdenum as a material for a wiring layer, an alloy Cr-Si-O as a material for a heat generating resistor layer and an Ni alloy layer as a material to be inserted between the wiring layer and solder. CONSTITUTION:A Cr-Si-O membrane is sputter-coated as a heat generating resistor layer 3 on an alumina substrate 1 with glazed layer for heat accumulation 2. Subsequent to this, an Mo membrane is formed as a wiring layer 5 by a sputtering technique. Only the Mo wiring layer 5 is photoetched and in succession, the Cr-Si-O layer 3 is photoetched to patternize the heat generating resistor layer 3 and the wiring layer 5. An SiO2 protective layer 6 is formed on the entire surface, and then is removed from the surface of a soldered connection terminal part and a padded part to allow the wiring layer 5 to be exposed. After this, an Ni-Cu alloy layer or an Ni-P, or Ni-B alloy layer 13 is formed on wiring by a DC magnetron sputtering method. Solder is supplied to a soldered connection part to mount a driver IC 12 and connect an externally outgoing electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film type thermal head suitable for application to facsimiles, printers, and the like.

[Conventional technology]

The structure of a conventional thermal head is shown in FIG. 2, in which a glaze layer (heat storage layer) 2, a heating resistor layer 3, a diffusion prevention layer 4, and a distribution layer 5 are sequentially laminated on an alumina substrate 1. A protective layer 6 is formed on the entire surface except for the solder connection part and the external lead terminal part (not shown), and if necessary, a wear-resistant layer 7 is formed on the protective layer 6, and further, For the solder connection part, an adhesive layer 8 and a solder diffusion prevention layer 9 are sequentially formed in contact with the wiring layer 5, and if necessary, a placement prevention layer (J
It had an extremely multi-layered structure, with 10 layers (such as u).

To be more specific, conventionally, as a heating resistor, one with an electrical resistance value of several hundred ohms was normally used due to the power supply voltage, and as a wiring layer, the electrical resistance value was Cu or At was used because it was necessary to keep the value of the resistor to 1 to 5 inches, but ('a or At is
A diffusion prevention layer 4, which also serves as a dense layer, is inserted between the wiring layer and the heat generating resistor layer due to the poor layer properties with the heat generating resistor layer and the ease of diffusion into the heat generating resistor layer. I needed to. In addition, regarding the solder joints, if a material with good solder wettability (and low solder diffusivity) is used, a C= structure can be used, but since no consistent material has been found, the wiring layer 5 It was necessary to form an adhesive layer 8 and a solder diffusion prevention layer thereon, and further, if necessary, to provide an oxidation prevention layer 10 on the solder diffusion prevention layer.

Here, regarding the solder connection part, the wiring layer 5 and the solder 11
It is conceivable to use Cu as an insertion material between C1L, but although C1L has good wettability with solder, at least 1 μm or more of it melts into the molten solder phase in one soldering operation. Considering the modification of the connection, a thickness of at least 3 to 4 layers will be required, and if such a thick Cu layer is formed, the internal stress will cause damage to the substrate or the metal layer itself. There is a problem that cracks are likely to occur.Furthermore, if a material other than Cu is used as the insert material, the thickness of the solder diffusion prevention layer is only about 1 μm, but poor solder wettability causes connection failures. In order to solve this problem, Japanese Patent Application Laid-Open No. 165211/1983 discloses that Cu, Ni
, an example has been given in which 5n layers are sequentially formed and the lack of solder wettability of N& is compensated for by 5n, but this structure increases the number of manufacturing steps and the solder component metals are brittle. There are problems such as the risk of forming an alloy layer, which is unfavorable in terms of connection reliability.

[Problem that the invention seeks to solve]

As mentioned above, conventional thermal heads require the formation of multiple skins in order to satisfy conditions such as ensuring adhesion and preventing diffusion, resulting in a large number of manufacturing steps and high manufacturing costs ( However, there were problems in that the connection reliability was not fully satisfactory.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems encountered in the prior art, and to provide a thermal head that has a simpler structure, thus lower manufacturing costs, and has high connection reliability.

[Means for solving problems]

The above purpose is to use a combination of heat generating resistor layer material and wiring layer material that has good adhesion and does not diffuse from the wiring layer to the heat generating resistor layer, and also to As an insertion material between IfMN1 and solder, it is recommended to use a material that has good solder wettability and a solder component metal (for example, S
This can be achieved by using a metal material with a low diffusion rate of n, pb, l, etc.).

That is, the inventors have conducted intensive studies on combinations of heat generating resistor layers and wiring materials that have good adhesion and do not diffuse from the wiring layer to the heat generating resistor layer. The material is tungsten (F) or moly7denum (
It has been found that it is suitable to use a Cr-5i-o alloy material as the heating resistor layer material in combination with the use of Mo).

In addition, regarding the solder connection part, as an insert material between the wiring layer and the solder, the conditions are that it has good solder wettability (and low diffusion rate of solder components, excellent corrosion resistance, and easy surface formation). As a result of consideration, Ni-C cram school,
It has been found that Ni-p and Ni-B alloys are suitable.

[Effect]

The electrical resistance value of the Cr-5i-0 alloy thin film can be changed over a wide range by changing its composition, and it is possible to easily explode a resistive thin film of about Ω at t5 to 2. . On the other hand, the resistance value of the Mo layer when formed as a wiring layer is about 45Ω, and the resistance value of the Mo layer is about 45Ω.
In combination with the r-Sz -0 heating resistor layer, 2 to
The power loss is only 5 cm, which is enough to withstand use. Also, M
The diffusibility of O into the Cr-Si-0 layer is extremely small;
Therefore, there is no need for a diffusion prevention layer between the heat generating resistor layer and the wiring layer, which was required in the prior art. In addition, in order to use it as a thermal head, StO
, a protective layer is formed, but the layer density of the 5io2 layer with respect to No is good, and there is no problem in using MO as a wiring layer material.

In addition, Ni-gold alloys such as N-Cu, Nc-p, and Ni-B have no qK problem in solder wettability and have low solder diffusivity, so they are used as insert materials between wiring layers and solder. When compared to the case where Cu is used in the prior art, it is about 1/. It is possible to make it as thick as 1. Moreover, since the combination of metal ribs for boiling and solder diffusion prevention layer, which was seen in the Jubei-gi I lamp, is not necessary, the time for film formation is shortened, and the possibility of failure of the board or layer cracking due to internal stress occurs. Nor.

〔Example〕

Hereinafter, the present invention will be explained in more detail based on the drawings.

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

First, the heat storage glaze layer 2ya-provided alumina substrate 1
A Cr--Si-04 film having a thickness of about 600 mm was sputter-distilled thereon as a heat-generating resistor layer 5, and subsequently.

A thin No film having a thickness of approximately 1 μm was formed as the wiring layer 5 by sputtering. Next, K over 70'C, IJII s
Cr-Si-
Without damaging the 0 layer 3, only the -1 do pattern #/@5 is photo-etched, and then the Cr-SL-0 layer 3 is photo-etched with a mixed solution of nitric acid and hydrofluoric acid to form the heating resistor layer 3. and described layer 5 was patterned.

Next, a protective layer 6 of Sin is formed on the entire surface by high frequency sputtering method, and in this state, a film of 550 to 4so'C is formed.
Heat treatment was performed to stabilize the resistance value of the heating resistor.

Next, by a photoetching method using a mixed solution of hydrofluoric acid and ammonium chloride (7), the Sin and protective layer 6 on the solder connection terminal portion and the butt portion are removed to expose the wiring layer 5, and the wiring layer 5 is exposed. , Thickness ~ CL5μm jM/L -C
The tb alloy layer 13 was formed by a DC magneto non-sputtering method. Here, in the alloy layer composition, the atomic ratio of Ni to Cu is 8/2 to 2/8, and the more Ni there is, the lower the solder diffusivity (and the more Cu, the better the solder wettability) This alloy layer 13 was patterned by a photoetching method using ferric chloride.

Next, a preliminary solder layer is added by supplying solder in advance to the solder joints formed by the above method or by dipping them in a solder bath, and the driver IC 12 is mounted and the external lead electrodes are connected. Completed the head.

Through the above steps, the electrical resistance of the heat generating resistor of the thermal head produced was approximately 1.6 KQ, the electrical resistance of the wiring layer was approximately 45 KΩ, and the power loss due to the wiring layer was within a non-problematic range. Also, even if you replace the chip twice,
No abnormality was observed.

Note that the exposed No. wiring layer 5 of the solder connection portion and the Ni-Cu
'! with alloy layer 13! Regarding the BN property, when the MO wiring layer 5 is exposed for a long time due to process reasons, N1-〇tL
Although the adhesion with the alloy layer may decrease, it is known that in such cases, adding a layer of Cr, Ti, or J(o) on the No layer can improve the layer density. Ta.

Example 2 Solder connection N by the same method as described in Example 1.

For the sample whose layer has been exposed, use a commercially available N1-P chemical plating solution and immerse it for about 1 minute to deposit an N1-p film with a thickness of about 0.5 - on the exposed MO layer,
A preliminary solder layer was added on the y Ni-p film in advance, and the driver IC 12 was mounted and the external extraction electrodes were connected by solder to create a thermal head.

As a result of measuring and inspecting the characteristics of the obtained thermal head, the electrical resistance value of the heating resistor and the electrical resistance value of the wiring layer were the same as those described in Example 1, and
No abnormality was observed even after the chip was replaced twice.

In the above example, the case where a Ni-P chemical plating layer is provided as an insert material between the Me layer and the solder has been described, but the same result can be obtained also in the case where an N1-B chemical plating layer is provided. was gotten.

Furthermore, the No. N-Cu gold alloy, the Ni-p alloy, and the Ni-B alloy have good solder wettability, and can be connected by solder using ordinary solder flux. However, if left for a long period of time, the surface of these alloy layers may oxidize and the solder wettability may deteriorate; however, in such cases, a layer of approximately 1000 to 200 mm thick may be coated on the alloy layer using a dipping method. It has been found that the problem can be solved by forming an A layer.

〔Effect of the invention〕

According to the present invention, by using a combination of a Cr-5i-○ series alloy as a heating resistor material and a wiring layer material (Mo), it is possible to eliminate the gap between the heating resistor layer and the wiring layer seen in the prior art. There is no need to install a diffusion prevention layer, and by using an appropriate Ni alloy skin as the solder connection wiring layer to solder interpolation layer.

The combination of a contact metal layer and a solder diffusion prevention layer, which is required in the prior art, is no longer necessary, and as a result, the number of manufacturing steps can be greatly reduced. In other words, in the case of the structure of the present invention, the required minimum number of films to be formed is three layers excluding the protective layer, which is much smaller than six layers in the case of the conventional technology. This means that the number of steps can be reduced significantly, and a low-cost thermal head can be provided.

In addition, if chemical plating is used to form the wiring layer to the solder threshold Ni alloy layer, the plating layer will be formed only on the wiring layer, which eliminates the need for a photoetching process compared to when forming by sputtering. This has the effect of reducing manufacturing costs in terms of aspects.

In addition, Ni-Cu is used as the wiring layer to solder interpolation material.

By using Ni-p or Ni-B,
As a result, the thickness of the insertion layer can be reduced to about 10 times that of the conventional Cu layer, which eliminates the occurrence of substrate destruction or film cracking due to internal stress, which is seen in conventional examples, and improves solder connections. This has the effect of improving reliability.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a thermal head according to the present invention, and FIG. 2 is a sectional view showing the structure of a conventional thermal head. 1... Alumina substrate 2... Glaze layer 5...
・Heating resistor layer 4...Diffusion prevention layer 5...Wiring layer 6...Protective layer 7...Wear-resistant layer
8...W! Layer metal layer 9...Solder diffusion prevention layer 10...Antioxidation layer 11/Shaft solder 1
2...Driver ICl3...Ni alloy layer

Claims (1)

[Claims] 1. In a thermal head consisting of a heating resistor layer, a placement layer, a protective layer, and a solder connection portion formed in sequence on a substrate having a glaze layer, Cr-Si-O is used as the heating resistor.
Using a molybdenum (Mo) alloy as a wiring layer, after patterning these, a protective layer is formed on the entire surface, the wiring layer is exposed to the solder connection part, and the wiring layer is applied directly to the solder connection part, or A thermal head comprising a Ni alloy layer formed through a Cr, Ti, or Mo layer. 2. As the Ni alloy layer formed on the solder connection part, N
The thermal head according to claim 1, characterized in that an i-Cu alloy, a Ni-P alloy, or a Ni-B alloy is used. 3. In a thermal head consisting of a heating resistor layer, a wiring layer, a protective layer, and a solder connection portion formed in sequence on a substrate having a glaze layer, Cr-Si-O is used as the heating resistor.
Using a molybdenum (Mo) alloy as a wiring layer, after patterning these, a protective layer is formed on the entire surface, the wiring layer is exposed to the solder connection part, and the wiring layer is applied directly to the solder connection part, or A thermal head characterized in that a Ni alloy layer is formed through a layer of Cr, Ti, or Mo, and further an Au layer is formed on the Ni alloy layer. 4. As the Ni alloy layer formed on the solder connection part, N
The thermal head according to claim 5, characterized in that an i-Cu alloy, a Ni-P alloy, or a Ni-B alloy is used.