JP2508923B2 - Thick film 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 thick film thermal head.

[0002]

2. Description of the Related Art A conventional thick film thermal head has an underglaze layer (heat storage layer) on the upper surface of an alumina ceramic substrate.
And forming an electrode pattern consisting of individual electrodes and a common electrode on this underglaze layer, and forming a heating resistor layer in a straddle shape on this electrode pattern, including this heating resistor and the electrode pattern. A glass protective layer is formed to cover the insulating substrate.

[0003]

In the above-mentioned conventional thick film thermal head, the electrode pattern (electrode pattern consisting of individual electrodes and common electrode) is formed by printing and firing a gold paste. However, since this gold paste is expensive, in recent years, it has been required to form an electrode pattern by using an inexpensive conductor paste for a popular thermal head. However, currently, there is no thermal head using an inexpensive conductor paste.

By the way, it is considered that an inexpensive thermal head can be obtained by using, for example, an inexpensive silver paste. However, in reality, silver paste is not currently used for forming electrodes. The reason is that the thick film thermal head is formed by printing and firing a heating resistor and a protective glass on the electrodes, and the firing temperature is 800 ° C.
It is around high temperature. Therefore, it is an essential condition that the electrode does not deteriorate even if it is fired at a high temperature of about 800 ° C. However, after forming the electrodes with silver,
When fired at a high temperature of ℃, the sintering of silver having a low melting point proceeds, and initially dense particles grow due to sintering, causing a gap between the particles. That is, as the sintering of silver progresses, the film shrinks and breaks, resulting in a high defective head ratio and poor reliability. As a result, it is considered that the reason why inexpensive silver paste cannot be used as the conductor paste.

The present invention solves the above problems and prevents the sintering of silver even when fired at a high temperature of 800 ° C.
An object of the present invention is to provide an inexpensive thick film thermal head that is free from the risk of disconnection.

[0006]

In order to achieve this object, the thick film thermal head of the present invention has the following structure. Thick film thermal head is an insulating substrate,
An underglaze layer formed on the insulating substrate, an electrode pattern including a common electrode and individual electrodes formed on the underglaze layer, and a heating resistor layer formed over the electrode pattern And a protective layer formed on the insulating substrate including the heating resistor layer and an electrode pattern, wherein the electrode pattern has a melting point higher than that of silver in a paste mainly composed of an organic compound of silver. It is characterized in that it is printed and fired with a thick-film conductor paste formed by mixing an organic compound of a noble metal having a high temperature.

In the thick film thermal head having such a structure, an organic compound of silver (silver paste) is used as a main component, and another noble metal organic compound having a melting point higher than that of silver, for example, a noble metal such as gold or platinum is mixed. The resulting thick film conductor paste is printed and baked on a substrate, and then patterned into a desired shape by photolithography to form an electrode pattern. Therefore, since the metal components are mixed at the paste stage, the metal components are uniformly dispersed. Further, a metal film is obtained by printing and firing this mixed paste, and this metal film has silver as a main component and other noble metals are uniformly dispersed therein. Therefore, the other noble metal dispersed in the silver film hinders the sintering of silver, and even if it is fired at a high temperature of 800 ° C., the sintering of silver can be prevented, and there is no fear of disconnection. As a result, it is possible to obtain a thick film thermal head that is inexpensive and has no disconnection.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a cross-sectional view of essential parts showing a concrete embodiment of a thick film thermal head according to the present invention.

As is well known, the thick film thermal head has an underglaze layer 2 formed on an upper surface of an insulating substrate (alumina ceramic substrate) 1, and a common electrode 3 and an individual electrode 4 are formed on the underglaze layer 2. The electrode pattern 5 is formed, the heating resistor 6 is formed over the electrode pattern 5, and the glass protective film 7 is formed on the insulating substrate 1 including the heating resistor 6 and the electrode pattern 5. Is configured.

FIG. 5 is a plan view showing a main part of the electrode pattern 5. The electrode pattern 5 includes a common electrode 3 and an individual electrode 4.
The common electrode 3 is provided with a comb tooth-shaped lead-out portion 31, and the individual electrodes 4 are arranged in a staggered manner between the adjacent lead-out portions 31. The heating resistor 6 has a strip shape and is formed so as to straddle the lead-out portion 31 and the individual electrode 4.

A feature of the present invention is that the electrode pattern (common electrode 3 and individual electrode 4) 5 is made of another noble metal organic compound (for example, gold) having a melting point higher than that of silver, not a gold paste but an organic compound of silver as a main component. Or organic compound of platinum)
It is formed by using a thick film conductor paste obtained by mixing .

In the embodiment, as the thick film conductor paste, a mixture of a silver organic compound paste and a gold organic compound paste is used. For example, the gold content is 10% by weight in the silver organic compound paste. This thick film conductor paste is printed on the underglaze layer 2 and
It is baked at 0 ° C. to obtain a conductor film having a thickness of 1 μm. Then, etching with an aqueous solution of potassium iodide iodine, 8 dots / mm
Is formed. Further, the heating resistor 6 and the protective glass 7 are formed on the electrode pattern 5 at 800 ° C. to obtain a thick film thermal head of 1728 dots / Head.

In the electrode pattern 5 thus obtained,
Since gold is mixed at the paste stage, the metal component is uniformly dispersed. Further, when the mixed paste is printed and baked, a metal film is obtained. This film contains silver as a main component and other noble metal (gold) is uniformly dispersed therein. Therefore, even if it is fired at a high temperature of around 800 ° C., the other metal (metal having a high melting point / gold) dispersed in the silver film inhibits the sintering of silver. Therefore, the sintering of the silver conductor does not proceed, and there is no fear of a disconnection defect.

FIG. 3 shows the results of examining the wire breakage rate by changing the gold content in the silver conductor film. In FIG. 3, the horizontal axis represents the gold content (% by weight) in the silver film, and the vertical axis represents the disconnection defective head ratio (%). According to this result, when the gold content rate is 0, the disconnection defective head rate is 100%.
As shown in FIG. 5, as a result of firing at a high temperature of 800 ° C., the sintering of silver proceeds, causing the film to contract and breaking. Also,
If the gold content is 1%, the defective head ratio for disconnection is extremely good, but it is not yet perfect. As shown in FIG. 6, partly due to the sintering of silver, there is a slight gap between the particles (the silver conductor contracts). Further, when the gold content was set to 10%, the disconnection defect rate was almost 0% in a perfect state.
That is, in the case of the example (when the gold content is 10%), as shown in FIG. 4, the sintering of silver is completely prevented and the disconnection due to the shrinkage of the film does not occur at all.

In the above embodiment, an example in which the gold organic compound paste is mixed with the silver organic compound paste is used, but in the present invention, the noble metal mixed with the silver organic compound paste is used. The paste of the organic compound is not limited to one kind of gold, and may be a mixture of a plurality of noble metal organic compounds if necessary. For example, when Rh (Rhodium) is mixed with an organic compound mixed paste of silver and gold, the rhodium is hard to solidify and tends to maintain a film shape, so that the rhodium becomes a mesh shape and silver and gold are evenly mixed. There is an advantage that

[0016]

According to the present invention, as described above, the electrode pattern is formed in the paste containing the organic compound of silver as the main component.
Since printing and firing was performed using a thick film conductor paste made by mixing other noble metal organic compound having a melting point higher than silver, silver sintering can be completely prevented and the risk of wire breakage can be eliminated. By using a mixed paste containing inexpensive silver as a main component and a little expensive gold, it is possible to provide an inexpensive thick film thermal head with good quality performance. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example thick film thermal head.

FIG. 2 is a plan view of a principal portion showing an electrode pattern of a thick film thermal head according to an embodiment.

FIG. 3 is an explanatory diagram of a result of examining a wire breakage rate by changing a gold content rate in a silver conductor film.

FIG. 4 is an explanatory diagram showing a result of a wire breakage rate when 10% of gold is contained in a silver conductor film.

FIG. 5 is an explanatory diagram showing a result of a wire breakage rate when gold is not contained at all in a silver conductor film.

FIG. 6 is an explanatory diagram showing a result of a wire breakage rate when 1% of gold is contained in a silver conductor film.

[Explanation of symbols]

 1 Insulating Substrate 2 Underglaze Layer 5 Electrode Pattern 6 Heating Resistor 7 Glass Protective Layer

Claims (1)

(57) [Claims] 1. An electrode pattern comprising an insulating substrate, an underglaze layer formed on the insulating substrate, and a common electrode and an individual electrode formed on the underglaze layer.
A thick film thermal head comprising a heating resistor layer formed over the electrode pattern and a protective layer including the heating resistor layer and the electrode pattern and formed on the insulating substrate. Is a thick-film thermal head characterized by being printed and fired with a thick-film conductor paste made by mixing a noble metal organic compound having a melting point higher than silver in a paste containing an organic compound of silver as a main component.