JP2779810B2 - Resin resistance paste - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a resin-based resistor paste for a thick-film resistor formed on an insulating layer such as a resin substrate.

(Related Art) In recent years, with the demand for smaller and thinner electronic devices, electronic components and printed wiring boards on which the electronic components are mounted have been reduced in size and thickness by increasing the density of patterns. There is a demand for a thinner material.

At present, as one of the very effective methods for satisfying these requirements, there is a method in which a resistor required in a circuit is formed as a film element directly on a printed wiring board by a screen printing method. According to this method, the resistor can be formed with a very small area except for the limitation due to the rated power, and the thickness of the resistor is much thinner than the chip resistor.

However, when the electronic equipment is made thinner, the printed wiring board itself is naturally made thinner, and easily bends when a mechanical external stress is applied. When a thick film resistor is formed on such a thin printed wiring board, a large bending stress is applied to the resistor due to the bending of the substrate.

By the way, in a conventional resin-based resistive paste, a granular material such as carbon particles has been used as a conductor. In addition, the high-resistance paste and the low-resistance paste in the resin-based resistance paste differ in the mixing ratio of the granular conductor and a resin serving as a binder thereof (hereinafter, referred to as a binder resin). In other words, high resistance paste (100KΩ / cm ² or more)
In order to reduce the conductivity of the resistor, the mixing ratio of the binder resin to the granular conductor is large. Conversely, in the low-resistance paste (1 KΩ / cm ² or less), the mixing ratio of the binder resin to the granular conductor is small in order to increase the conductivity.

When a bending stress is applied to the resistor formed by the conventional resin-based resistor paste as described above, the resistor formed by the low-resistance paste has a large volume ratio of the granular conductor in the resistor. Therefore, the resistor itself is very brittle, and cracks easily occur with respect to bending stress. On the other hand, a resistor formed of a high-resistance paste has a smaller volume ratio of a granular conductor than a low-resistance resistor, and therefore is less likely to crack. However, when the volume ratio of the binder resin is large, the dimensional change of the binder resin due to heating, humidification, or the like becomes large, and the resistance value of the resistor also becomes large.
That is, it is very difficult for the conventional resin-based resistive paste to simultaneously satisfy both the crack resistance and the heat resistance and the moisture resistance in low resistance and high resistance.

(Problems to be Solved by the Invention) The present invention has been made to solve the problems of the conventional resin-based resistive paste as described above. On the other hand, it is an object of the present invention to provide a resin-based resist paste that forms a thick-film resistor having a very small change in resistance and excellent crack resistance.

(Means for Solving the Problems) In order to achieve the above object, the present inventors have conducted intensive studies and as a result, have found that the following resin-based resist pastes are significantly superior to conventional pastes. Was.

That is, the resin-based resistance paste according to the present invention is a resin-based resistance paste obtained by mixing a conductive short fiber, a fibrous insulating filler, and a high-boiling organic solvent with a binder resin.

 Hereinafter, a detailed description of the present invention will be described.

As the binder resin used in the present invention, an epoxy resin, a phenol resin, a melamine resin, a polyimide resin, a bismaleimide / triazine resin, a thermosetting resin such as a xylene resin, and a curing agent thereof, a polysulfone resin,
Examples thereof include thermoplastic resins having excellent heat resistance such as polyphenylene oxide and polyphenylene sulfide.

As the conductive short fibers, carbon fibers or fibers made of a non-conductive heat-resistant material such as ceramics such as silicon nitride, aluminum nitride, silicon carbide, and magnesium oxide; Substances coated (plated) with metals such as gold, silver, nickel, solder, lead, copper, silver / palladium alloy, or gold, silver, nickel, solder, lead, copper, aluminum, stainless steel, silver / palladium, etc. Metal fibers.

Further, in the resin-based resistance paste according to the present invention,
Granular conductive filler, fibrous insulating filler, and an organic solvent can be blended, and as the granular conductive filler, carbon, gold, silver, nickel, solder,
Examples include metals such as lead, copper, and silver / palladium alloys. Examples of the fibrous insulating filler include inorganic insulating fillers such as silicon nitride, aluminum nitride, silicon carbide, aluminum oxide, magnesium oxide, silica, aluminum hydroxide, and talc; and fluorine-containing resins, engine-nearing plastics such as polyphenylene oxide, and polysulfone. , Polyimide resin powder, benzoguanamine resin powder,
An organic insulating filler having high heat resistance such as an epoxy resin powder may be used. As the organic solvent, a solvent having a high boiling point, such as α-terpineol and butyl carbitol, is used. This is because when the boiling point is low, the change in the viscosity of the paste is remarkably unfavorable.

Furthermore, in addition to the binder resin, the conductive short fiber, the granular conductive filler, the fibrous insulating filler, and the organic solvent, the resin-based resistance paste according to the present invention includes a curing accelerator, a flame retardant, and a cup, if necessary. A ring agent, a thixotropy-imparting agent, a leveling agent, an adhesion-imparting agent, an antifoaming agent and the like can be added.

The above composition, crusher, three rolls, ball mill,
It can be prepared as a paste by a generally well-known kneader such as an ultrasonic disperser. This paste can be formed as a film element on a printed wiring board by a screen printing method, a dispenser method, or the like.

(Operation of the Invention) The present invention has the following operation by adopting the above means.

In the present invention, by adding a conductive short fiber and a fibrous insulating filler to the binder resin, regardless of the mixing ratio between the granular conductor and the binder resin, as in the conventional resin-based resistive paste, low resistance is obtained. -A thick film resistor excellent in crack resistance, heat resistance and moisture resistance can be formed on a printed wiring board regardless of the high resistance.
That is, by adding the conductive short fibers, the short fibers are arranged in the formed thick film resistor endlessly in all directions, and when an external stress such as bending is applied to the substrate, the action of relaxing the stress ( Thus, a thick film resistor having a low crack generation rate can be obtained even if the volume ratio of the binder resin is small, such as a low-resistance paste. Further, by adding a fibrous insulating filler, a dimensional change due to heating and humidification of the binder resin is suppressed. Therefore, even if the volume ratio of the binder resin such as the high-resistance paste is large, a thick-film resistor having a small resistance change rate when left at high temperature or at high temperature and high humidity can be obtained. In addition, since a high-boiling organic solvent such as α-terpineol, butyl carbitol and the like is contained, the change in viscosity of the paste is small and the quality is stable.

In addition, when a non-conductive heat-resistant material coated (plated) with a conductive material is added, depending on the degree of coating (plating) of the non-conductive heat-resistant material with a conductive material, either a low-resistance or a high-resistance resin-based paste can be used. Is also obtained,
The thick film resistor formed in this way also has excellent characteristics described above. In particular, when this method is used, a high-resistance paste, which has been unstable in the related art due to thermal expansion and contraction of the binder resin, can be more easily and stabilized.

(Examples) Next, the present invention will be specifically described with reference to examples.

First, a mixing example of the resin-based resistance paste of the present invention will be described, but the present invention is not limited to the following mixing examples. In the following formulation examples, “%” means all weight percent of solid content only.

(Example) Example 1 Epoxy resin 75.0% as a binder resin, carbon short fiber 15.0% as a conductive short fiber, and ceramic short fiber 10.0% as a fibrous insulating filler were kneaded by a crusher, The viscosity was adjusted with α-terpineol as an organic solvent to obtain a thick film resistor paste shown in FIG.

Example 2 Example except that 75.0% of an epoxy resin was used as a binder resin, 15.0% of a carbon short fiber was used as a conductive short fiber, 5.0% of a ceramic short fiber was used as a fibrous insulating filler, and 5.0% of benzoguanamine fine powder was used as a granular insulating filler. 1, and the thick film resistor paste shown in FIG. 2 was obtained.

Comparative Example 1 The procedure of Example 1 was repeated except that 60.0% of an epoxy resin was used as a binder resin and 40.0% of carbon black was used as a particulate conductive filler.

Comparative Example 2 The procedure of Example 1 was repeated except that 75.0% of an epoxy resin was used as a binder resin, 15.0% of carbon black was used as a granular conductive filler, and 10.0% of benzoguanamine fine powder was used as a granular insulating filler.

As shown in FIG. 5, the thick film resistor pastes of the above Examples and Comparative Examples were applied to the surface of the substrate (20) having the surface of the electrode (30) treated by Ni-Au plating using a screen printer, Cured at 180 ° C. for 90 minutes. Then, a commercially available solder resist ink (trade name: CCR-506G, manufactured by Asahi Chemical Laboratory Co., Ltd.) is applied as an overcoat (40) on the formed thick film printed resistor (10) by a screen printing machine. And cured at 140 ° C. for 15 minutes. The heat resistance, humidity resistance and crack resistance of these thick film resistors (10) were evaluated by the following methods, and the results are shown in FIGS. 6 and 7 and Table 1.

(High-Temperature Leaving Test) The resistance change rate when the test piece was left in a thermostat at 100 ° C. for 1000 hours was measured. However, measurement of resistance value is performed for 24 hours at room temperature.
After leaving.

(High-temperature and high-humidity storage test) The resistance change rate when the test piece was left for 1000 hours in a thermo-hygrostat at 85 ° C.-85% Rh was measured. However, the resistance value was measured after standing at room temperature for 24 hours as in the high temperature standing test.

(Bending Test) The test piece was placed on a cylindrical tube, and the tube was bent while changing the radius of curvature of the tube, and the crack occurrence rate was measured.

As is clear from FIG. 6, FIG. 7, and FIG. 1, the rate of change of the resistance value of each example is larger than that of the comparative example.
It was almost half the value. Further, the crack generation rate was significantly lower than that of the comparative example. From these facts, it has been clarified that the thick film resistor using the resin-based resistor paste according to the present invention is much more excellent in heat resistance, moisture resistance, and crack resistance than the conventional one. .

(Effect of the Invention) As described above, according to the resin-based resistor paste of the present invention, the resistance value change rate due to high temperature storage, high temperature and high humidity storage, and mechanical external It is possible to provide a thick film resistor whose crack generation rate due to stress is extremely low, and since the viscosity change of the paste is small and the quality is stable, it is extremely effective as a resin-based resist paste for a thick film resistor. is there.

[Brief description of the drawings]

1 to 4 are partially enlarged views schematically showing the resin-based resistor paste according to the present invention, FIG. 5 is a partial cross-sectional view showing a substrate on which a printed resistor is formed, and FIGS. 6 and 7 are shown. Is a graph showing the time-to-resistance change rate characteristics. DESCRIPTION OF SYMBOLS 1 ... conductive short fibers, 2 ... binder resin, 3 ... fibrous insulating filler, 4 ... granular insulating filler, 5 ...
... Granular conductive filler, 10 ... Thick film resistor, 20 ... Substrate, 30 ... Electrode, 40 ... Overcoat.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-289077 (JP, A) JP-A-55-150583 (JP, A) JP-A-55-144180 (JP, A) JP-A-59-180180 177885 (JP, A) JP-A-60-110755 (JP, A) JP-B-39-26368 (JP, B1)

Claims (1)

(57) [Claims] 1. A resin-based resist paste for a thick-film resistor formed on an insulating layer such as a resin substrate, comprising a binder resin comprising conductive short fibers, a fibrous insulating filler, and a high-boiling organic solvent. A resin-based resistance paste, characterized by being included.