JP2997963B2 - Silver-nickel based resinate paste, conductor forming method using the resinate paste, and thick film type thermal print head including conductor layer formed using the resinate paste - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silver-nickel resinate paste, a method for forming a conductor using the resinate paste, and a thick film type thermal print head including a conductor layer formed using the resinate paste.
The conductor layer formed by printing and baking the silver-nickel-based resinate paste is characterized in that the rise in the conductor resistance is extremely small even when baking is repeated at about 800 ° C.

[0002]

2. Description of the Related Art For example, a wiring pattern on a substrate of a thick film thermal print head mounted with an IC is usually formed as follows. First, between the output section of the drive IC and the heating resistor forming section, for example, 1
In order to individually drive each heating dot divided at a rate of 8 dots in a length of mm, it is necessary to form an extremely fine comb-like wiring pattern. Therefore, as a conductor material, while adopting gold which is resistant to current corrosion such as migration, and forming a relatively thin gold film by printing and firing using this resinate gold as a form of the resinate gold, The first conductor layer made of the fine wiring pattern is formed by applying a photo-etching technique to the first conductive layer. Next, especially for the common wiring portion, in order to secure a sufficient amount of common current, reduce a voltage drop in the middle of the common conductor wiring, and improve print quality, the first conductor layer formed by the above method is used. , A second conductor layer formed by printing and firing a relatively inexpensive silver paste is formed on the common wiring pattern.

[0003]

However, as described above, in the case of including a wiring structure in which the first conductor layer made of gold and the second conductor layer made of silver are laminated, the gold film and the silver There is a problem that the formation of the alloy layer at the boundary with the film causes a relatively high value of interface resistance. As described above, even if the thickness of the silver coating layer as the second conductor is increased to reduce the resistance value of the entire first conductor layer and the second conductor layer, the resistance value never falls below the above-described interface resistance. is there.

Therefore, as one measure for avoiding the above-described problem of the occurrence of interface resistance, silver is used instead of gold to form the first conductor layer, and the first conductor layer and the second conductor layer are formed. It is conceivable that both layers are formed of silver. However, as is apparent from the above, the first conductor layer is a thin conductor layer formed by printing, baking and etching in the form of a resinate, particularly in the form of a resinate, in order to form a fine wiring pattern. A new problem such as

That is, in order to form a substrate of a thermal print head, after forming a wiring pattern, printing and baking of a heating resistor and printing and baking of a glass protective film are performed.
A firing step usually performed at a temperature of 800 ° C. or higher is performed a plurality of times. And, as described above, when the first conductor is formed of silver, the firing step at 800 ° C. or more is repeated a plurality of times.
The sintering of the silver film as the first conductor layer proceeds as the firing process is repeated, and a scum occurs in the silver film, and the resistance value of the first conductor layer increases, or a fine wiring pattern. Therefore, there is a problem that the wire is disconnected. Therefore, adoption of silver as the first conductor layer of the wiring pattern of the thermal print head has not been put to practical use yet.

Therefore, an object of the present invention is to provide a first conductive layer which employs a silver-based metal film while significantly reducing the interface resistance between the first and second conductive layers. At the same time, it is an object of the present invention to avoid a problem of occurrence of skewing of the first conductor layer due to repetition of the firing step or an increase in conductor resistance or disconnection due to this.

[0007]

SUMMARY OF THE INVENTION The inventor of the present application has stated that (1) that the conductor resistance does not increase even if firing is repeated five times at 800 ° C.
That is, sintering does not progress even by repeated firing, and no inflammation occurs. (2) The conductor resistance after firing is 2
In order to satisfy the condition of being smaller than 00 mΩ / □ · 1 μm, a study was conducted on an appropriate substance to be added to silver and the proportion of the substance added.

First, nickel (Ni), gold (Au), palladium (Pd), platinum (Pt), cobalt (Co), zinc (Zn), chromium (Cr), tungsten (W), molybdenum (M
o), antimony (Sb), and aluminum (Al) were selected, and the pattern printed using resinate silver containing each of them was examined for changes in the conductor resistance as a result of repeating firing at 800 ° C. five times. As a result, it was found that only the case of resinate silver containing nickel satisfies the above condition (1).

FIG. 1 shows a case of a first conductor layer containing only silver and a case of a first conductor layer containing nickel in silver (silver contained 9%).
5 shows the rate of change in conductor resistance with the number of firings at 800 ° C. for 5% by weight and 5% by weight of nickel. As can be seen from FIG. 1, in the case of the first conductor layer made of only silver, 800
When the number of firings at 6 ° C. is repeated six times, the resistance value doubles or more. On the other hand, the silver-nickel first conductor layer increases the number of firings and does not increase the resistivity, but rather decreases slightly. It turns out that it changes to. This indicates that nickel as an additive to silver has an effect of preventing sintering of silver.

Next, when the conductor resistance value after firing was examined by changing the addition ratio of nickel to silver, FIG.
As shown in the figure, when the nickel addition rate is about 5% by weight or less, the conductor resistance value of the baked silver-nickel film is 200%.
It was found to be less than mΩ / □ · 1 μm. Although the minimum of the nickel addition rate is not always clear,
When the content is 1.0% by weight or more, it is assumed that the above-mentioned effect of preventing sintering of silver is exerted.

From the above, nickel is contained in the silver film at 1.
If it contains 0% to 5% by weight, such a silver film will
This means that a sufficiently low resistance value can be achieved as a conductor layer on which a fine wiring pattern is to be formed, and furthermore, it can withstand repeated firing at a high temperature and no increase in resistance value due to the progress of sintering occurs.

Of course, the main component of the first conductor layer thus formed is silver. When a silver film is formed as the second conductor layer, an alloy layer is formed between the first conductor layer and the second conductor layer. No increase in the interfacial resistance value occurs. When forming a silver-nickel-based first conductor layer to form a wiring pattern such as a thermal print head as described above, it is necessary to form a resinate paste as a printing material because it is necessary to form a fine wiring pattern. You. Such a resinate paste is preferably prepared by mixing an organic compound of silver and an organic compound of nickel and adding a resin to the mixture to have a viscosity suitable for screen printing. In this case, the compounding ratio of silver and nickel as the metal solid finally deposited after firing may be set in the above range.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below.
This will be specifically described with reference to the drawings. The first conductor layer 2 of the thermal print head 1 is formed by using the silver-nickel-based resinate paste of the present invention, and among the wiring patterns thus formed, the first conductive layer 2 is superimposed on the common wiring pattern portion, and the silver-based second conductive layer is formed. Two conductor layers 3 were formed.

First, a resinate paste containing 26.0% by weight of silver, 1.0% by weight of nickel, and a fine additive in addition thereto was prepared.
A silver-nickel-based metal film is formed on the surface of the substrate by printing and firing. After the firing, the coating is 95.8% by weight of silver and 3.4% by weight of nickel, and has a thickness of about 1 μm. By etching this silver-nickel-based film using an aqueous solution of potassium iodide, a wiring pattern including the first conductor layer 2 including a fine wiring pattern is formed.

Next, a second conductive layer 3 having a thickness of 12 μm is formed on the common wiring pattern portion by printing and baking a silver paste. This silver paste is obtained by dispersing silver powder and glass powder in a resin, similarly to the one used for ordinary thick film printing. Then, screen printing is performed using a ruthenium oxide (RuO ₂ ) -based resistance paste, and the screen is fired at 800 ° C., thereby forming the heating resistor 4. Then, a predetermined portion of the wiring pattern on the substrate including the heating resistor 4 is covered,
The protective film 5 is formed by printing and firing.

The interface resistance between the first conductor layer thus formed and the second conductor layer could be reduced by about 60% as compared with the case where the first conductor layer was made of gold. Of course, since the coating of the first conductor layer 2 contains nickel, sintering of silver, which is the main component of the first conductor layer 2, can be performed even when the above-described repeated firing at 800 ° C. is performed. Do not proceed
There is no occurrence of scalp and no increase in conductor resistance value due to this.

[0017]

As described above, when a wiring pattern is formed using the silver-nickel-based resinate paste of the present invention, a fine wiring pattern employing an etching technique can be formed because of the resinate paste. In addition, a sufficiently small conductor resistance value can be secured as compared with the case where a fine wiring pattern is formed using resinate gold. The cost of an electronic component substrate on which a wiring pattern is formed using the resinate paste is significantly reduced as compared with the related art.

A thick film type thermal print head including a common wiring pattern in which a second conductive layer using a silver paste is formed on the first conductive layer thus formed is cost-effective for the same reason as described above. As well as being able to achieve a reduction, compared to the conventional method in which the first conductor layer is formed of gold, a remarkable decrease in the interfacial resistance between the first conductor layer and the second conductor layer can be seen. Provided is a thermal printhead in which a voltage drop in a common wiring portion is small and printing quality is improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the rate of change in conductor resistance according to the number of firings at 800 ° C. for a conductor containing only silver and for a silver-nickel conductor.

FIG. 2 is a graph showing a change in conductor resistance depending on the amount of nickel added to silver.

FIG. 3 is a partial cross-sectional view showing a wiring pattern configuration on a substrate of a thick film type thermal print head.

FIG. 4 is a sectional view taken along line IV-IV in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic base 2 First conductor layer 3 Second conductor layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification code FI B41J 3/20 111H (58) Investigated field (Int.Cl. ⁷ , DB name) H01B 1/22 B41J 2/335 C09D 5 / 24 H01C 7/00 H01C 17/06

Claims (3)

(57) [Claims] 1. A resinate paste containing at least an organic compound of silver and an organic compound of nickel and mixed with these resins to form a paste, wherein 95 to 99% by weight of silver is contained in the metal element component. Is 1 to 5% by weight of a silver-nickel resinate paste. 2. A method for forming a conductor, comprising printing on a substrate using the silver-nickel resinate paste of claim 1 and firing the printed material. 3. A thick film type thermal print head having a drive IC mounted on a substrate, wherein all or a part of the wiring pattern formed on the substrate is the silver-nickel resinate paste according to claim 1. Including a first conductor layer formed by etching a silver-nickel film printed and fired by using a second conductor layer formed by printing and firing a silver paste on a part of the first conductor layer. A thick-film type thermal print head, characterized by being formed of: