JPH0278575A - Heat-resistant insulating substrate and thermal head - Google Patents

Abstract

PURPOSE:To prevent damage to a heat-resistant resin layer in a production process and simplify the control of a value of resistance by a method wherein an amorphous substance layer containing at least one of hydrogen and halogen and mainly composed of silicon and at least one of nitrogen, carbon, and oxygen is provided as a resin protective layer, and thereon an amorphous silicon carbide layer is provided. CONSTITUTION:On a metal substrate 1, a heat-resistant resin layer 2 serving as a heat-accumulation layer and also an insulating layer is formed. On the heat resistant resin layer 2, a resin protective layer 3 made of a first layer of an amorphous substance containing at least one of hydrogen and halogen and mainly composed of silicon and at least one selected from among nitrogen, carbon, and oxygen and a second layer formed on the first layer and made of an amorphous silicon carbide containing silicon carbide as a main component and having a specific resistance value of 10''OMEGAcm or more at room temperature is provided to form a heat-resistant insulating substrate 4. In this manner, the possibility of damaging the heat-resistant resin layer 2 is eliminated when an electrode substance and a heating resistor substance are dissolved and removed into a required circuit pattern, and a gas generation can be prevented when the heating resistor substance is formed in vacuum, which stabilizing a resistance value.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a thermal head used in a thermal recording device such as a facsimile or a printer, and a heat-resistant insulation used in this thermal head and various electronic devices. Regarding the board.

(Prior Art) Recently, heat-resistant insulating substrates in which heat-resistant resins such as polyimide resins are provided as insulating layers or heat storage layers on various substrates have been developed for use in high-resistance substrates for thermal heads, multilayer circuit boards for hybrid ICs, etc. They are increasingly being used as support substrates for various electronic devices that require high reliability against such heat.

For example, in thermal heads, instead of the conventional high-resistance substrate formed by forming a glazed glass layer on a ceramic substrate such as alumina as a heat-retaining layer to control heat dissipation and heat accumulation, a ceramic substrate or a metal substrate is used as a high-resistance substrate. A heat-resistant insulating substrate on which a heat-resistant resin layer such as a polyimide resin layer is formed is used.

As a thermal head provided with this polyimide resin layer as a heat insulating layer, for example, one having the following structure is known.

That is, a heat-resistant resin layer made of polyimide resin or the like, which serves as a heat storage layer and an insulating layer, is formed on a metal substrate made of an Fe alloy or the like, and Ta-5in, Ti-5iO□
A heat-generating resistor made of the following is formed into a film by sputtering or the like. Furthermore, an opening that becomes a heat generating part is formed on this heat generating resistor, and individual electrodes and a common electrode made of AQ, AQ-3i-Cu, etc. are formed, and silicon oxynitride is formed so as to cover at least this heat generating part. (SL-0-N) or the like, and has a wear-resistant layer that also serves as an oxidation-resistant film.

By using a polyimide resin layer as a heat insulating layer, such a thermal head has a thermal diffusivity of polyimide resin that is 1/3 to 1/6 that of a conventional glazed glass layer.
Because of its low thermal efficiency, it has excellent thermal efficiency. In addition, since it is possible to use a flexible support substrate such as a metal substrate, it is also possible to perform bending processing, so it is attracting attention as a small, inexpensive, and high-performance thermal head. . However, such a thermal head has the following problems in its manufacturing process.

For example, the heat-resistant resin layer is damaged during etching processing performed when forming heating resistors and electrodes, or during ashing of a masking film.

Further, when depositing the heating resistor material in a vacuum, a large amount of gas is released from within the polyimide resin layer, and the influence of this gas causes a problem in that it is difficult to control the resistance value.

Furthermore, when wiring using the wire bonding method,
A problem arises in that bonding is difficult to perform due to the elasticity of the polyimide resin layer.

As a means to solve these problems, the present applicant has previously developed a method using alumina and silicon oxynitride between the heat-resistant resin layer and the heat-generating resistor layer.

We have proposed a thermal head with a protective resin layer made of an inorganic insulator such as Sialon (Japanese Patent Application No. 1986-21).
No. 428, No. 62-134326, No. 62-1916
No. 55).

By forming a resin protective layer between the heat-resistant resin layer and the heating resistor layer in this way, damage to the polyimide resin layer and gas release from the polyimide resin layer are prevented during the manufacturing process, and the overall rigidity is also improved. Since this increases to a certain extent, effects such as being able to perform the mounting process stably are obtained.

Forming a resin protective layer on a heat-resistant resin layer in this way is an effective means not only as a high-resistance base for thermal heads, but also as an insulating substrate for other electronic devices, allowing the mounting process to be performed stably. It is.

(Problem to be Solved by the Invention) As described above, a heat-resistant insulating substrate is provided in which a resin protective layer made of an inorganic insulating material such as alumina, silicon oxynitride, or sialon is provided on a heat-resistant resin layer such as polyimide resin. Although various advantages can be obtained by using it as a high-resistance substrate of a thermal head, for example, the above-mentioned inorganic insulating layer does not have sufficient film strength.

For example, the following problems occur.

In other words, when the present inventors installed the thermal head having the resin protective layer described above into a printer and actually conducted a printing running test, it showed abnormal resistance value changes during running, a phenomenon that adversely affected printing. was frequently recognized. A detailed investigation into this abnormal resistance change revealed that foreign matter such as dust caught between the thermal head and the thermal paper or between the thermal paper and the roller caused cracks in the wear-resistant layer that forms the surface layer of the thermal head. It has been found that when these cracks reach the heating resistor, they have an adverse effect on printing characteristics.

Such problems cannot be seen in thermal heads that use conventional high-resistance substrates with a glazed glass layer formed on a ceramic substrate or high-resistance substrates with a glass layer formed on a metal substrate, and which otherwise have the same structure. This is a phenomenon that was not possible.

This is because the hardness of the entire substrate is large in thermal heads that use a high-resistance substrate that uses a glazed glass layer or a glass layer as a heat-retaining layer. Because it only causes the same deformation as 1
It is thought that local deformation is prevented and racks as described above do not occur.

On the other hand, in the case of a high-resistance substrate made of a heat-resistant resin such as polyimide resin, although the rigidity of the substrate is increased to some extent by the resin protective layer as described above, the deformation of the resin makes it difficult to wear. This is because the deformation of the heat-resistant resin layer cannot be prevented by the resin protective layer or the wear-resistant layer when a locally concentrated load is applied to the wear-resistant layer. It is thought that the deformation of the resin protective layer and wear-resistant layer cannot follow the deformation of the heat-resistant resin layer, resulting in cracks.

Such problems are not limited to thermal heads, but also occur in multilayer circuit boards for hybrid ICs as mentioned above, where deformation of the heat-resistant resin layer during the mounting process causes disconnection of the wiring layer provided on top of it, defective bonding, etc. It invites.

The present invention was made in order to address the problems of the prior art, and includes a heat-resistant insulated substrate that has increased rigidity and reduced the incidence of defects in the mounting process, and a Prevents cracks in the wear-resistant layer,
The purpose is to provide a thermal head with improved reliability.

[Structure of the invention]

(Means for Solving the Problems) A heat-resistant insulating substrate of the present invention includes a highly thermally conductive support substrate,
a heat-resistant resin layer formed on this support substrate; and a heat-resistant resin layer provided on this heat-resistant resin layer that contains at least one of hydrogen and halogen elements and is made of at least one selected from nitrogen, carbon, and oxygen and silicon. A first layer made of an amorphous material, and a second layer made of amorphous silicon carbide, which is mainly composed of silicon carbide and has a resistivity value of 10"ΩS or more at room temperature, is formed on the first layer.
The invention is characterized by comprising at least a resin protective layer consisting of a layer and a resin protective layer. Note that the room temperature is approximately 25°C.

Further, the thermal head of the present invention includes a highly thermally conductive support substrate, a heat-resistant resin layer formed on the support substrate, a resin protective layer provided on the heat-resistant resin layer, and a resin protective layer formed on the resin protective layer. A thermal head comprising at least a large number of formed heating resistors, a conductor connected to each of the heating resistors, and a wear-resistant layer provided to cover at least a heat generating part of the heating resistor. .

The resin protective layer includes an amorphous first layer containing at least one of hydrogen and a halogen element and consisting of silicon and at least one selected from nitrogen, carbon, and oxygen; At least a resin protective layer consisting of a second layer made of amorphous silicon carbide containing silicon carbide as a main component and having a resistivity value of 10'''Ω#1 or more at room temperature is provided thereon. It is something to do.

(Function) In the thermal head of the present invention, the resin protective layer and heat-resistant wear layer, and in the heat-resistant insulating substrate as the resin protective layer, contain at least one of hydrogen and halogen elements, and are composed of silicon, nitrogen, carbon, and oxygen. An amorphous layer containing at least one of these as a main component is formed, and amorphous silicon carbide is further formed thereon. These amorphous layers are kept in a very stable state by the hydrogen and halogen elements in the film, and also have a high toughness because they contain many dislocations. Furthermore, since it is an inorganic film, it has much higher hardness than polyimide or the like.

By the way, if we only consider preventing deformation of the heat-resistant resin layer in a thermal head, for example, this can also be achieved by increasing the thickness of the wear-resistant layer.

However, in this method, the distance between the heating resistor and the thermal paper becomes large, which not only causes significant performance disadvantages such as decreased efficiency and resolution, but also significantly reduces mass productivity. In contrast, in the present invention, since an amorphous material having the above properties is used, the strength of the entire substrate can be improved without increasing the film thickness.

Furthermore, by laminating amorphous silicon carbide, dry etching resistance, which is essential for device manufacturing, is ensured. Furthermore, the resistivity value of the amorphous silicon carbide is tol+Ω′−
By ensuring the above conditions, the role of the insulating substrate is fully fulfilled.

(Example) Next, two embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of the main parts of a thermal head according to an embodiment of the present invention, and 1 is a 0-thickness film made of Fe-Cr alloy.
, shows a metal substrate of about 5 mm. On this metal substrate 1, a heat-resistant resin layer 2 made of polyimide resin, polyamide-imide resin, or a mixture or laminate thereof, which serves as a heat storage layer and an insulating layer, is formed to a thickness of about 20 mm. A resin protective layer 3 is formed on the resin layer 2 to a thickness of 1 to 10 layers, and is made of an amorphous material mainly composed of at least one of nitrogen, carbon, and oxygen and silicon, and containing hydrogen or a halogen element. Thus, a heat-resistant insulating substrate 4 is constructed.

On this heat-resistant insulating substrate 4, Ta-SiO□, Ti
A heat generating resistor 5 made of -3iO, etc. is formed, and an opening serving as a heat generating portion is formed on the heat generating resistor 5.
Individual electrodes 6 and common electrodes 7 having a temperature of about 7-1°C are formed, and at least the openings serving as the heat-generating parts also serve as an adhesive layer 8 made of SiO□ and an oxidation-resistant film made of 5i-0-N. A wear-resistant layer 9 is formed.

This thermal head has an individual electrode 6 and a common electrode 7.
By applying a pulse voltage at predetermined time intervals between the two, the heating resistor corresponding to the opening serving as the heating section generates heat, and printing is performed.

This thermal head is manufactured, for example, as follows.

First, as shown in FIG. 2, a metal substrate 1 made of an Fe-16 wt% Cr alloy is cut into predetermined dimensions, degreased, cleaned, dried, and heated at 600°C to 800°C in a dry hydrogen atmosphere.
Heat treatment is performed (Fig. 2-A). Next, a predetermined amount of polyimide varnish or polyamide-imide varnish, for example, is applied onto this metal substrate 1 using a roll coater or a spin coater so that the film thickness will be 20 to 30 μs after baking.
Drying and baking are performed to form a heat-resistant resin layer 2 (Fig. 2 - opening).

Next, after cleaning the surface of this heat-resistant resin layer 2 (Fig. 2-
c), such as sputtering method, ion blating method,
Vacuum deposition method, plasma CVD method, ECR plasma VCVD
The resin protective layer 3 is formed by
(Figure 2-2).Among these methods, it is important that the adhesion of the film is good, that it can be processed at a relatively low temperature without damaging the properties of the substrate, and that the physical properties of the film, such as electrical and optical properties, are The plasma CVD method is suitable because the physical characteristics can be easily controlled. In particular, in the present invention, since the substrate to be adhered is made of a heat-resistant resin, the substrate temperature cannot exceed 550°C, which is the heat-resistant temperature of general polyimide resin, even when polyimide resin is used as the heat-resistant resin. A method that can process at low temperatures below the heat-resistant temperature is required.

This plasma CVD method uses SiH4 gas, SiF4 gas, etc. as the Si component of the raw material gas, and N2 gas, CH4 gas, N, O gas, etc. as the other component, and converts these gases into plasma in a vacuum. This is a method of forming a desired ceramic thin film on a substrate. At this time, hydrogen and halogen elements such as fluorine in the source gas are occluded in the film, and a thin film that can stably maintain an amorphous state due to the influence of these elements is obtained.

In this example, a heat-resistant insulating substrate 4 was produced by forming a resin protective layer 3 using a parallel plate type capacitively coupled plasma CVD apparatus shown in FIG. 3 according to the procedure shown below.

In FIG. 3, 11 is a vacuum chamber, and inside this vacuum chamber 11 there is a flat ground electrode 12 and a high frequency electrode 1.
3 are installed facing each other, and this flat ground electrode 1
A processing substrate 14, that is, a metal substrate on which a heat-resistant resin layer is formed, is placed on the substrate 2. Next, the inside of the vacuum chamber 11 is evacuated to about 10-' Torr by a vacuum pump (not shown), and then the processing substrate 14 is heated to about 150° C. to 450° C. by the heater 15 attached to the ground electrode 12. Next, while supplying the raw material gas into the vacuum chamber 11 from the gas inlet 16, the temperature is set at 0.05 Torr to 1,0 Torr.
While evacuating from the exhaust port 17 so as to maintain a degree of vacuum of approximately The raw material gas is turned into plasma, and a target thin film is formed on the processing substrate 14.

Here, specific examples of film forming conditions are shown in Table 1 below.

(Sales T-+ b) Table 1: For example, when depositing a film of SiO□ using the conventional sputtering method, it took 4000 people/hour, compared to 500 people/hour when depositing a 5i-0-N film. Then, plasma C
When using the VD method, as shown in Table 1, the film formation rate is significantly improved.

Therefore, the process time can be shortened.

This is advantageous in reducing costs.

Here, the resin protective layer has a thickness of, for example, a-3 inches.

A combination of 5/ffi and a-3iC0,3- can be considered.

From the experimental results, it was found that a-3iC has sufficient CDE resistance with a film thickness of about 0.2/7+1. Also, like a-5iO, the lower layer has a Knoop hardness of 500 to 600 Kgf.
It was found that even if the film has a relatively low hardness of about 1/m", by layering about 0.3 μm of a-3iO as the upper layer, the hardness can be increased to a Knoop hardness of 1300 and more than gflrrxm2. Next, Ta-3iO□ is deposited on the resin protective layer 3 of the heat-resistant insulating substrate 4 by sputtering or other known methods.
, Ti-3in, etc., to form a film.
- After forming a film of Cu, Au, etc. by a sputtering method (see Fig. 2), a masking film with a desired circuit pattern in which openings that will become heat generating parts are formed is formed, and then, for example, a chemical dry etching process is performed. and
Individual heating resistors 5, individual electrodes 6 and common electrode 7 are formed (FIG. 2-g).

After this, adhesive layers 8 and 5L-(1-
A wear-resistant layer 9 made of N and also serving as an oxidation-resistant film is formed by sputtering or other known methods (FIG. 2-H) to complete the thermal head.

Next, the results of measuring the hardness of the resin protective layer and the hardness of the wear-resistant layer serving as the surface layer in the manufacturing process of this thermal head will be described.

First, a-3iO was formed on the heat-resistant resin layer 2 as a resin protective layer 3.
500 people, 1 polish, 2 instants, 3 IU, 5 p film thickness were formed by the above-mentioned procedure, and then an a-5iC film was deposited on top of it.
．． 3-The Knoop hardness of each layer was measured after lamination. The results are shown in FIG. As is clear from the figure, the Knoop hardness value became almost constant when the film thickness of a-3iO was about 2p to 3μs or more. Further, if the film thickness is less than one layer, sufficient hardness is not achieved.

Next, the a-5iO film of each thickness mentioned above and the a-5iO film of 0.3go
Using a heat-resistant insulating substrate having a resin protective layer made of a laminated film of 5iC films, a heating resistor, individual electrodes, and a common electrode were formed according to the above-mentioned procedure, and a 5in2 film with a thickness of IIm was added thereon as an adhesive layer. A 5i-0-N film having a thickness of 2 mm was sequentially formed as a wear-resistant layer, and the Knoop hardness on this 5i-0-N film was measured. The results are shown in FIG.

It can be seen from the figure that, similar to the hardness of the resin protective layer, the a-5iO film of the resin protective layer reaches a substantially constant hardness in about 2 μs or more, and does not reach a sufficient hardness if it is less than 1-. It was also found that even with a film made only of a-5iC, sufficient hardness could not be obtained with less than 1 hardness.

From these results, it was found that a sufficient effect of improving film hardness could not be obtained when the total film thickness of the resin protective layer was within a range of about 1 tm. In addition, if the film thickness is too thick, not only will no further effect be obtained, but the heat storage effect of the heat-resistant resin layer will weaken and the efficiency will decrease, so the preferred film thickness of the resin protective layer is 1/ffi to 10 - It will be about.

Next, a thermal head having a resin protective layer made of an a-3iN film and an a-5iC film having the respective film thicknesses described above was mounted on a heat dissipation board made of AQ using double-sided tape, and a driver board mounted in the same manner. When we conducted a wiring test using the above driving IC and ultrasonic wire bonding, we were able to perform stable bonding.

In addition, the thermal head obtained in this way was heated at 60°C, 9°C.
When a test was conducted for 1000 hours in a constant temperature and humidity chamber at 0%, there was no peeling of the film and no problems occurred.

In addition, each of these thermal heads was actually installed in a printer and a printing running test was conducted. The test environment was at room temperature and humidity. As a result of the 5k111 running test, a thermal head with a resin protective layer made of a laminated film of 500-thick a-5iO and 0.3-thick a-3iC film had five cracks in the wear-resistant layer, and the same film thickness In the case of 500 people using the a-5iC film as a resin protective layer, cracks occurred at 8 locations. On the other hand, when a 0.3 μs a-8iC film was laminated on a 54 μs a-5iO film with a film thickness of 1/ffi, 21M, and 3 μs, almost no cracks were observed.

In addition, as a comparison with the present invention, using a thermal head having the same structure except that a sialon layer with a thickness of 1 μs was formed as a resin protective layer using a sputtering method in the thermal head of the above-mentioned example, a printing run of 5 km was carried out in the same manner. When the test was conducted, 20 cracks were found in the wear-resistant layer.

It is clear from this test result that the thermal head of this example has excellent crack resistance.

That is, the thermal head of this embodiment uses the a-3iN film and the a-5iO film, which are formed by plasma CVD as a resin protective layer between the heat-resistant resin and the heat-generating resistor, to provide the desired electrode material and heat-generating resistor material. There is no risk of damaging the heat-resistant resin layer when dissolving and removing it into the circuit pattern, and the resistance value is stabilized because gas generation can be prevented during the formation of the heat-generating resistor material in vacuum. moreover.

During wire bonding in the mounting process, the cushioning effect of the heat-resistant resin layer is offset by the hardness of the resin protective layer, making it possible to perform wire bonding stably. In addition to these effects, the a-5iO of this example
The laminated film of film and a-5iO film has high toughness and hardness, so
Even if local pressure is applied to the wear-resistant layer during actual printing operations, this resin protective layer can prevent the heat-resistant resin layer from deforming without increasing the film thickness too much. In other words, local deformation is prevented. This prevents the wear-resistant layer from cracking. Therefore, printing can be performed stably over a long period of time, and reliability is greatly improved.

In addition, in the above examples, a-5iN was used as the resin protective layer.
Although the explanation has been made regarding the use of the film and the a-3iC film individually, similar effects were obtained when a laminate of these films was used as the resin protective layer.

For example, a-
By forming a 3iN film on a heat-resistant resin layer to a thickness of about 2-2, and then forming an a-5iC film with a thickness of about 1i, which is advantageous in etching resistance (against chemical dry etching), on top of it. , a similar effect was obtained. Similar effects were also obtained when a stack of films with different film properties was used by changing the composition ratio of the constituent elements of these a-5iN films and a-3iC films.

In addition, in the above-mentioned embodiment, α-eye evaluation was explained as a thermal head, but the heat-resistant insulating substrate is not limited to a thermal head, but can also be used as a multilayer circuit board for a hybrid IC, etc. due to the hardness of the resin protective layer. This improvement effect improves the stability of the mounting process and effectively prevents the occurrence of defects due to breakage of wiring layers.

〔Effect of the invention〕

As explained above, according to the heat-resistant insulating substrate of the present invention,
By improving the hardness of the resin protective layer, the mounting process can be carried out stably, and the incidence of defects such as wire breakage is reduced, and when used as a high-resistance substrate for a thermal head, the printing run of the thermal head can be improved. can be stabilized.

In addition, it has good chemical dry etching resistance, so it has excellent process compatibility. Furthermore, it has sufficient insulation properties when used in thermal heads and the like.

Further, according to the thermal head of the present invention, damage to the heat-resistant resin layer during the manufacturing process is prevented.

The resistance value can be easily controlled, wire bonding during the mounting process can be performed stably, and cracks in the wear-resistant layer, which is the surface layer during actual character running, can be effectively prevented, making it possible to perform stable printing. Therefore, its reliability is greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a partially exploded perspective view showing the main parts of a thermal head according to an embodiment of the present invention, FIG. 2 is a flow chart showing the manufacturing process of a thermal head according to an embodiment of the present invention, and FIG. FIG. 4 is a diagram showing the configuration of the plasma CV Da apparatus used to form the amorphous layer in the embodiment of the invention, and is a graph showing the relationship between the thickness of the resin protective layer and its Knoop hardness in the embodiment of the invention. FIG. 5 is a graph showing the relationship between the thickness of the resin protective layer and the Knoop hardness on each wear-resistant layer in an example of the present invention. 1... Metal substrate, 2... Heat-resistant resin layer, 3
... Resin protective layer, 4. Heat-resistant insulating substrate, 5.
...heating resistor, 6...individual electrode. 7...Common electrode. 9. A wear-resistant layer that also serves as an oxidation-preventing film. Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) A support substrate with high thermal conductivity, a heat-resistant resin layer formed on the support substrate, and a heat-resistant resin layer provided on the heat-resistant resin layer containing at least one of hydrogen and halogen elements, containing nitrogen, carbon, and oxygen. A first layer of an amorphous material made of silicon and at least one selected from the above, and a material having a resistivity value of 10^1^1 Ωcm at room temperature and containing silicon carbide as a main component on this first layer.
A heat-resistant insulating substrate comprising at least a second layer made of amorphous silicon carbide as described above and a resin protective layer made of the above-mentioned amorphous silicon carbide. (2) A highly thermally conductive support substrate, a heat-resistant resin layer formed on this support substrate, a resin protective layer provided on this heat-resistant resin layer, and a large number of heat generating units formed on this resin protective layer. A resistor, a conductor connected to each of these heating resistors,
In the thermal head, the resin protective layer contains at least one of hydrogen and a halogen element, and contains nitrogen, carbon, and oxygen. a first layer of an amorphous material made of silicon and at least one selected from among the above, and a layer containing silicon carbide as a main component and having a specific resistance value of 10^1^1 Ωcm or more at room temperature on this first layer; A thermal head comprising at least a second layer made of amorphous silicon carbide and a resin protective layer made of a certain amorphous silicon carbide.