JP2551767B2 - Thermal head - Google Patents

Description

The present invention relates to a thermal head used in a thermal recording apparatus, and more particularly to a thermal head equipped with a control IC for driving and controlling a heating resistor in a printing section of the thermal head. It is about.

(Prior art and its problems) A glaze layer is provided on an insulating ceramic substrate, and a heating resistor layer, an electrode layer, and a protective layer are sequentially formed on the glaze layer by using a thin film method such as a vacuum deposition method or a sputtering method. Stacked thin-film thermal heads have become the mainstream in recent years because they are more advantageous than thick-film thermal heads in terms of higher printing density and thermal response.

In such a thin film type thermal head, in order to cope with the speeding up of printing and to avoid complication of the configuration, a circuit for controlling heat generation of the heating element in the printing portion, that is, a heating element is provided. It is known that a driver that controls the energization of the device, a shift register that selectively controls the heating element to be energized, and an IC chip that integrates a latch circuit are mounted.

In such a thermal head equipped with a control IC,
If the control circuit part is manufactured by the thin film method similarly to the method of manufacturing the printing part, there is a problem that a sufficient current capacity cannot be obtained due to the large sheet resistance of the thin film electrode and the print density varies. Furthermore, when a so-called mesa-shaped glaze layer is used in which only the printed part is provided, the surface of the thin-film electrode is as rough as the ceramic substrate when the IC chip is wire-bonded in the control circuit part. Therefore, there is a problem in that the adhesive strength of wire bonding cannot be sufficiently obtained, and reliability cannot be expected.

Therefore, it is considered that only the control circuit section is manufactured on a substrate different from the printing section by a thick film method using gold paste, and then this control circuit section is connected to the printing section manufactured by the thin film method. However, in this case, another problem such as an increase in new steps for connection and difficulty in downsizing of the thermal head occurs. Therefore, recently, the printing unit is a thin film type on the same insulating ceramic substrate, In addition, an integrated thermal head has been proposed in which the control circuit section is manufactured by a thick film method.

However, as shown in FIG. 3, this integrated thermal head has a heating resistor layer 2, a thin film electrode layer 3, and a protective layer 4 of a protective layer 4 which are sequentially laminated on an insulating ceramic substrate 1 by a thin film method. Is connected directly to the thick film electrode 6 of the control circuit portion, and thus the protective layer 4 is made of ceramic, and the thick film electrode 6 has gold as one of its main components. There is a certain reason, that is, basically, the ceramic and the gold are connected to each other, so that the bonding force between the two becomes much weaker than that, so that the protective layer 4 may be peeled from this portion.
It has a problem of causing a contact failure between the printing section and the control circuit section.

(Means for Solving Problems) The present invention has been made in view of the above knowledge, and is a control IC.
By using the existing heating resistor layer or thin film electrode layer as an adhesive layer without providing a new adhesive layer when bonding the protective layer of the printed part and the thick film electrode of the control circuit part in the on-board thermal head The purpose of the present invention is to provide a highly reliable thermal head that eliminates the conventional problems.

That is, the present invention is a printing unit formed by a thin film method,
In a thermal head in which a control circuit unit formed by a thick film method for mounting a control IC for driving and controlling a heating resistor in the printing unit is formed on the same insulating substrate, A thermal head characterized in that a heating resistor layer and / or a thin film electrode layer of a printing portion are interposed between a thick film electrode containing one of the main components and a protective layer in the printing portion. Is.

(Example) Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 is a sectional view of an essential part showing an example of a thermal head according to the present invention. Reference numeral 1 is an insulating substrate such as alumina ceramic, 1a is a mesa-shaped glass glaze layer formed on the insulating substrate 1, 2 is a refractory metal silicide such as titanium, chromium or tantalum, or their nitrides, carbides, oxides,
In addition, a heating resistor layer made of tantalum nitride, nichrome, etc., 3
Is a thin-film electrode layer made of aluminum, aluminum alloy, gold, etc., and 4 is a protective layer made of silicon oxide, nitride, carbide, tantalum oxide, etc., which constitutes the printing portion A. Insulating substrate 1
A control circuit portion B is formed on the top. This control circuit B
Has a thick film electrode 6 mounted on it, and the control IC 5 is bonded to the insulating substrate 1 by die bonding and connected to the thick film electrode 6 by wire bonding. There is.

Thus, the printing section A and the control circuit section B, which are the features of the present invention,
As for the connecting portion C, the one end of the thick film electrode 6
6a is directly connected to only the heating resistor layer 2 in the printing portion A and is not in contact with the protective layer 4. In other words, in other words, since the heating resistor layer 2 is interposed between the thick film electrode 6 and the protective layer 4, the protective layer 4 and the heating resistor layer 2 are
Since the adhesion strength between the heating resistor layer 2 and the thick film electrode 6 is sufficient,
The peeling of the protective layer 4 from the starting point and the contact failure between the printing portion A and the control circuit portion B do not occur, and therefore the intended purpose can be achieved.

In the present embodiment, the heating resistor layer 2 is interposed between the protective layer 4 and the thick film electrode 6 to prevent the adhesion failure of the protective layer 4. Instead,
The thin film electrode layer 3 may be provided so as to be interposed therebetween, or the two layers of the heating resistor layer 2 and the thin film electrode layer 3 may both be interposed between the protective layer 4 and the thick film electrode 6. Although it is good, it is particularly preferable to interpose a heating resistor layer made of a refractory metal silicide or a nitride, carbide, or oxide thereof. The reason for this is that the refractory metal silicide-based heating resistor is heated to 400 ° C. or higher in a vacuum or in a non-oxidizing gas atmosphere during or after its formation by the thin film method. It is necessary to crystallize the heating resistor layer) to stabilize the resistance value, and during this heating, silicon in the refractory metal silicide and gold in the thick film electrode form a eutectic (eutectic of silicon and gold). This is because a stronger bond strength can be obtained as a result.

Next, a method of manufacturing a thermal head according to the present invention will be described based on the above embodiment.

First, a glass paste and a gold paste are screen-printed on the insulating substrate 1 and baked in air to form the mesa-shaped glaze layer 1a and the thick film electrode 6. Next, as shown in FIG. 2, a metal mask 7 is used to mask the connection portion of the thick film electrode 6 in the control circuit portion B with the printing portion A, and the above-mentioned heating resistor layer 2 is sputtered by about 200 to 2000Å. And a thin film method such as a vacuum deposition method. At this time, it is necessary to heat to 400 ° C or higher in the vacuum chamber during or after the formation. Next, the thin film electrode layer 3 made of aluminum alloy or the like is formed by the thin film method using the metal mask 7 '.
In this case, as another method, the thin-film electrode layer 3 is manufactured by using the same metal mask 7 as in the case of forming the heating resistor layer 2, and thereafter unnecessary portions are removed by various etchings to remove the heating resistor layer 2. May be partially exposed. Next, a register pattern is formed on the thin-film electrode layer 3 so that the connection portion C has the same pitch as the thick-film electrode 6 pattern, and unnecessary portions of the thin-film electrode layer 3 and the heating resistor layer 2 are removed by etching. Here, when etching the heating resistor layer 2, it is preferable to use dry etching in consideration of side etching. Next, using a metal mask 7 ″, for example, SiNx
A protective layer 4 composed of (5 ≦ x ≦ 40) is formed by a reactive sputtering method, and finally a control IC 5 is fixed on the insulating substrate 1 by die bonding, and further connected to a thick film electrode 6 by wire bonding. Then, in order to protect the control IC 5, it is completed by coating it with a silicon-based resin 8.

(Effects of the Invention) As described above, the present invention is a control circuit formed by a thick film system in which a printing unit formed by a thin film system and a control IC for driving and controlling a heating resistor in the printing unit are mounted. In a thermal head in which a portion is formed on the same insulative substrate, a heating resistor layer of a printing portion is provided between a thick film electrode of the control circuit portion containing gold as one of the main components and a protective layer of the printing portion. And / or because a thin film electrode layer is interposed, for control
Not only can the advantages of a thermal head with an IC be exhibited, but it is also possible to reduce the risk of peeling of the protective layer in the printed area and contact failure between the printed area and the control circuit as much as possible. This is what a high thermal head can provide.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an example of a thermal head according to the present invention, FIG. 2 is a sectional view of an essential part showing a manufacturing process of the thermal head shown in FIG. 1, and FIG. 3 shows a conventional example of a thermal head. FIG. 1 ... Insulating substrate, 1a ... Glaze layer, 2 ... Heating resistor layer, 3 ... Thin film electrode layer, 4 ... Protective layer, 5 ... Control IC, 6 ...
Thick film electrode, A …… printing part, B …… control circuit part, C …… connecting part

Claims (2)

(57) [Claims] 1. A printing section formed by a thin film method, and a control IC for driving and controlling a heating resistor in the printing section.
In the thermal head in which the control circuit section formed by the thick film method for mounting is configured on the same insulating substrate,
Between the thick film electrode containing gold as one of the main components of the control circuit section and the protective layer of the printing section, the heating resistor layer and / or the heating resistor layer of the printing section are provided so that the two do not come into direct contact with each other. A thermal head having a thin film electrode layer interposed. 2. The thermal head according to claim 1, wherein the heating resistor layer is made of a refractory metal silicide or a nitride, carbide or oxide thereof.