JP2006269588A - Thick film resistor paste, thick film resistor, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thick film resistor paste whose rating can be improved. <P>SOLUTION: The thick film resistor 10 is provided with a pair of electrodes 2 formed on the front side of a substrate and a resistor 1 formed between a pair of the electrodes 2. The resistor 1 is formed by baking a resistor material and thick resistor paste containing carbon nanofibers. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a thick film resistor paste, a thick film resistor, and more particularly to a chip-type thick film resistor, and more particularly to a thick film resistor having a low resistance resistor mainly composed of copper and a method for manufacturing the same.

In recent years, a chip-shaped thick film resistor having a smaller shape has been developed for the demand for high-density mounting of electronic components. In high-density mounting, a power rating equal to or higher than the conventional one is required even in a small shape. This means that a large power load is applied to the resistor.
In conventional chip type thick film resistors, in order to cope with higher ratings, by changing the composition of the metal that constitutes the resistor, or by devising the electrode structure, by improving the heat dissipation using heat conduction The current situation is to support this.

In order to support high-density mounting in conventional chip-type thick film resistors, the resistor pattern can be optimized by changing the composition of the metal resistance material in order to reduce the size and increase the rating of the resistor. Is called. This requires many trials and evaluations based on empirical rules, and has a problem of requiring a great deal of time and labor.
Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a thick film resistor paste, a thick film resistor, and a method for manufacturing the same that can improve the rating. .

In the present invention, the thick film resistor paste includes carbon nanofibers.
The carbon nanofiber has an average diameter of 200 nm or less and a length of 10 to 20 μm.
The carbon nanotube content is preferably 1 wt% or less.
The resistor material includes an alloy mainly composed of copper.

The thick film resistor according to the present invention is a thick film resistor comprising a pair of electrodes formed on a substrate surface and a resistor formed between the pair of electrodes. These thick film resistor pastes are formed by firing.

Further, a method for manufacturing a thick film resistor according to the present invention includes a pair of electrodes formed on a substrate surface and a resistor formed between the pair of electrodes. The thick film resistor paste according to any of the above is printed between a pair of electrodes, and the thick film resistor paste is baked to form the resistor.

As described above, according to the present invention, the carbon nanofibers are added to the existing thick film paste to increase the thermal conductivity of the thick film resistor by thick film printing, thereby reducing the heat dissipation from the electrodes. There is an effect that the rating can be improved by increasing the size. Also, the temperature coefficient of resistance (TCR) can be reduced by reducing the thermal expansion coefficient of the thick film resistor. Accordingly, there is an effect that a resistor having a smaller size and an equivalent rating can be realized with the same structure as the conventional one.

Next, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory sectional view of a chip-type thick film resistor 10. The structure of the resistor 10 itself is a general one and is known.
That is, a pair of surface electrodes 2 are formed of, for example, silver or a silver alloy on the surface of an insulating substrate 12 such as an alumina substrate, a glass ceramic substrate, a glass epoxy substrate, or a polyimide substrate. Is formed.

Further, a first protective film 3 made of a glass insulating film or the like is formed so as to cover the resistor 1, and further, a second protective film 4 made of a resin insulating film or the like is formed so as to cover the first protective film 3. Has been.
A back electrode 9 is formed on the back side of the insulating substrate 12, and a plating film 6 such as Ni plating for electrically connecting the front electrode 2 and the back electrode 9 is formed on the end surface of the insulating substrate 12, An outer plating film 7 such as Sn is formed so as to cover the plating film 6 and formed on the resistor 10.
The structure of the resistor 10 is not limited to the above.

The thick film resistor paste for forming the resistor 1 is adjusted as follows, for example.
That is, first, a polymer solution is prepared by dissolving about 7 wt% of a linear polymer (vehicle) such as ethyl cellulose in an organic solvent such as texanol. Thereafter, carbon nanofibers (VGCF manufactured by Showa Denko; hereinafter abbreviated as VGCF) are added to this polymer solution, and ultrasonic waves are applied to disperse the VGCF. VGCF having an average diameter of 0.2 μm (200 nm) or less and a length of 10 to 20 μm is suitable.

The method of preparing a polymer solution and dispersing VGCF in this polymer solution in this way results in less tangled VGCF entanglement than when VGCF is added directly to an organic solvent and dispersed by application of ultrasonic waves. Excellent long-term stability of dispersion.
A metal film (alloy) powder composed of copper: 57 wt% and nickel: 43 wt% was placed in a polymer solution in which ethyl cellulose was dissolved in texanol, and kneaded and kneaded to prepare a thick film printing paste.

Using this paste, a resistor pattern was formed on the alumina substrate 8 on which the surface electrode 2 was previously formed by a known thick film printing technique. After printing the resistor pattern, heat treatment (baking treatment) was performed in nitrogen.
Further, the back electrode 9 is formed by thick film printing, and if necessary, the resistor adjusts the resistance value by known laser trimming, and then the first protective film 3 and the second protective layer 4 are formed.
After the end face electrode 5 was formed by sputtering, a chip type thick film resistor 10 (FIG. 1) having a structure in which nickel and tin plating layers 6 and 7 were formed was produced.

In the above, a thick film prepared by mixing and kneading a metal powder composed of 80 wt% or more of copper and 20 wt% or less of manganese and Fe in a polymer solution in which ethyl cellulose is dissolved in texanol and in which VGCF is dispersed. Even when the printing paste was printed, the characteristic improvement described below was the same.

FIG. 2 shows the amount of VGCF added to the resistor paste (0 wt%, 0.7 wt%, 1.75 wt%), the resistance temperature coefficient (TCR), and the linear expansion coefficient. As apparent from FIG. 2, it can be seen that the TCR decreases with respect to the amount of VGCF added. FIG. 3 shows the results of measurement of the amount of VGCF added, the surface temperature of the resistor, and the thermal conductivity. It shows that the thermal conductivity is improved up to about 1 wt% of VGCF. However, if it is about 1 wt% or more, the thermal conductivity decreases conversely. This is because the resistance paste containing VGCF and copper as main components is poorly wet and VGCF is unevenly distributed during the heat treatment after thick film printing.

Therefore, the amount of VGCF added is preferably 1 wt% or less in order to improve the thermal conductivity for improving the rating of the resistor. On the other hand, the surface temperature of the resistor decreases as the amount of VGCF added increases, indicating that heat radiation and heat dissipation due to heat conduction are improved. The same thing occurs for the average diameter. That is, if the average diameter is larger than 0.2 μm, VGCF tends to precipitate non-uniformly after the heat treatment and acts as a foreign substance, so that the average diameter is preferably 0.2 μm or less.

As a second example of the present invention, when VGCF was dispersed in an organic solvent in which ethyl cellulose was dissolved in texanol, dispersion by a shaker was performed. As a result, the same relationship was obtained between the TCR of the resistor, the thermal expansion coefficient, the surface temperature, and the thermal conductivity with respect to the added amount of VGCF. However, in the dispersion by the shaker, VGCF tends to deposit non-uniformly by post-printing heat treatment with a thick film printing paste prepared by adding metal powder mainly composed of copper, and the maximum value of VGCF added is An amount less than 1% by weight is desirable.

In the above description, a resistor having copper as a main component is described as an example of a low-resistance resistor. However, the resistor is not limited to this. The resistor may be, for example, a metal oxide such as RuO ₂ , SnO, ZnO, Cu ₂ O, CuO, NiO, TaO, or the like.

It is sectional drawing which shows the cross-section of a square chip resistor. It is a graph which shows the relationship between the addition amount (wt%) of VGCF, TCR, and a linear thermal expansion coefficient. It is a graph which shows the relationship between the addition amount (wt%) of VGCF, the surface temperature of a resistor, and thermal conductivity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Resistor 2 Surface electrode 3 1st protective film 4 2nd protective film 5 End surface electrode 6 Nickel plating layer 7 Tin plating layer 8 Alumina substrate 9 Back surface electrode 10 Resistor

Claims (6)

  A thick film resistor paste comprising carbon nanofibers in a thick film resistor paste.   The thick film resistor paste according to claim 1, wherein the carbon nanofiber has an average diameter of 200 nm or less and a length of 10 to 20 µm.   The thick film resistor paste according to claim 1 or 2, wherein the carbon nanotube content is 1 wt% or less.   The thick film resistor paste according to any one of claims 1 to 3, wherein the resistor material includes an alloy mainly composed of copper. In a thick film resistor comprising a pair of electrodes formed on a substrate surface and a resistor formed between the pair of electrodes,
A thick film resistor, wherein the resistor is formed by firing the thick film resistor paste according to any one of claims 1 to 4. In a method of manufacturing a thick film resistor comprising a pair of electrodes formed on a substrate surface and a resistor formed between the pair of electrodes,
The thick film resistor paste according to any one of claims 1 to 4 is printed between the pair of electrodes, and the thick film resistor paste is baked to form the resistor. Method for manufacturing a membrane resistor.

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