JPS6312368B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a chip-type carbon film resistor.

Conventionally, carbon film resistors, in which pyrolytic carbon is deposited on the surface of an insulator, have often been used in a leaded or leadless form. In recent years, demand for leadless, so-called chip resistors has rapidly increased.

As shown in FIG. 1, this chip-type carbon film resistor has a carbon film 2 formed on the surface of an insulator 1.
It has a structure in which iron caps 3 are press-fitted at both ends. For this reason, the shape of the final product is larger than the original shape of the resistor, and the iron cap 3 increases the weight.Therefore, a reduction in weight and size is desired.

The present inventors investigated a method for improving the above-mentioned drawbacks of chip-type carbon film resistors, and found that instead of press-fitting the iron cap, by plating metal on both ends of the resistor, a lightweight and small chip-type resistor was developed. He discovered that it was possible to manufacture resistors.

As a solution to this problem, there are chip-type resistors whose electrodes are plated with metal, but it is difficult to electroplate on high-resistance films, and when electroless plating is used, the plating adhesion is insufficient. There are problems such as the inability to obtain

The method for manufacturing a carbon film resistor of the present invention includes the steps of forming a protective film on the surface of the carbon film formed on the surface of an insulating substrate except for the electrode-forming part, and the surface of the carbon film that is not covered with the protective film. This method involves the process of making the carbon film hydrophilic and the process of metal plating on the surface of this hydrophilic carbon film.The electrode is formed on the carbon film, which is inherently water repellent, and is usually used for direct electroless plating. On the surface of pyrolytic carbon, where it is difficult to create a plating layer with strong adhesion, we apply a metal plating layer that will become an electrode to the carbon film part that will be used as a resistor. It is something that can be formed without any change.

The material for the protective film will vary depending on the surface treatment method used in the next step to make the carbon film hydrophilic, but if anodizing or vacuum discharge treatment is used, the material that can form the film will vary. That's fine as long as it is. In the case of heating in air, materials that can withstand heating, such as glass, metal oxides, metal carbides,
It is necessary to use inorganic compounds such as metal silicides, aromatic polyimides, and other heat-resistant polymer materials.

There are the three methods mentioned above to make the surface of the carbon film hydrophilic.The first method is to anodize the carbon film in an electrolyte solution. That is, as shown in FIG. 2, a carbon film resistor 5 formed by forming a carbon film on the surface of an insulating substrate and a protective film in the center is immersed in an electrolyte solution 4, and this resistor 5 is used as an anode. Water is electrolyzed, and the surface of the carbon film is oxidized by the nascent oxygen to make it hydrophilic. Although noble metals such as carbon and platinum can be used as the material for the cathode 6, a carbon electrode is sufficient. As the electrolyte, inorganic acids, organic acids, alkalis, salts thereof, etc. can be used. As the solvent, not only water but also an organic solvent may be used.

The second method is to oxidize the surface of the carbon film in heated air. Processing conditions vary depending on the conditions for forming the carbon film, but in general heating at a temperature of 550°C or lower can prevent problems such as disappearance of the carbon film due to excess oxygen.

The third method is a method of discharging in a gas at a low degree of vacuum. Gases include air, argon, nitrogen,
Oxygen, etc. or fluorine compounds, chlorine compounds, etc.
Any compound that gasifies at a vacuum of 10 ^-2 torr to 1 torr can be used. The discharge power source may be any power source as long as it generates a voltage capable of starting a discharge in gas, and any frequency from direct current to extremely short waves can be selected. The degree of vacuum during discharge is
A vacuum level that generates a so-called glow discharge of 10 ^-3 torr to 1 torr is preferable, but processing at a vacuum level of 10 ^-4 torr is also possible by using a high frequency power source.

After the above hydrophilic treatment, depending on the hydrophilic treatment method, the electrode can be attached by metal plating either immediately or after coating the carbon film with a non-hydrophilic material except for the part where the electrode will be formed. Form.

In other words, if a non-hydrophilic material is used for the protective film and it is made hydrophilic by anodic oxidation, it is possible to proceed immediately to the metal plating process, but if heat treatment or vacuum discharge treatment is used, for example Even if the protective film is non-hydrophilic, it is likely to become hydrophilic during treatment of the carbon film, so it is desirable to recoat the portions where no electrodes will be formed with a non-hydrophilic material prior to metal plating. However, even if a metal layer is formed on the protective film without being coated again, the adhesion strength of this metal layer to the protective film is weak.
It is possible to peel it off mechanically afterwards.

Note that methods such as transfer, brushing, and spraying can be used to coat the carbon film with the non-hydrophilic material. As the non-hydrophilic material, various waxes such as paraffin wax, various thermoplastic resins such as polystyrene, and various thermosetting resins such as phenolic resin can be used.

Resistors recoated with these non-hydrophilic materials or as-is resistors treated to make them hydrophilic are
Electrodes are then formed by metal plating. As the metal plating method, a conventionally known electroless plating method is used. Further, when a thick electrode is required, it is preferable to increase the electrode thickness by electroplating followed by electroless plating because a thick electrode can be obtained in a short time. As the electroplating method, barrel plating or an improved method thereof can be used.

The resistor with electrodes formed in the above manner may be coated with a protective film or non-hydrophilic material, or after it has been peeled off, grooves are cut to determine the resistance value, and a protective coating is applied to the final product. It becomes a carbon film resistor.

An example of a carbon film resistor produced in this manner is shown in FIG. In the figure, 7 is an insulator which is an insulating base, 8 is a carbon film formed on the surface of this insulator, and 9 is an electrode formed by metal plating on both ends of the insulator 7 on which the carbon film 5 is formed.

Note that if the protective film or non-hydrophilic material is not removed, the protective film remains in the central portion. Although not shown, a protective paint is also applied.

This carbon film resistor is highly reliable because the electrode plating thickness is much thinner than that of a conventional cap, and it is small, lightweight, and is in full contact with the carbon film.

Examples of the method for manufacturing a carbon film resistor of the present invention will be described below.

Example A A resistor was manufactured by depositing a carbon film on the surface of an alumina rod having a diameter of 3 mm and a length of 11 mm by a conventional method.

Apply resol type phenol resin to the center part excluding a width of 2 mm from both ends of this resistor, and
After curing at ℃ for 10 minutes, it was immersed in a 5% oxalic acid solution to make it hydrophilic using the apparatus shown in FIG.

Next, the entire resistor was treated with a sensitizing solution and an activating solution, and electroless nickel plating was performed using a conventional method to form nickel electrodes at both ends of the resistor.

Next, grooves were cut to determine the resistance value, and the usual protective coating was applied to complete the chip-shaped carbon film resistor.

The characteristics of this chip-type carbon film resistor, such as heat resistance characteristics, moisture resistance characteristics, and noise characteristics, are completely the same as those of ordinary cap resistors, and the resistance value depends on the surface treatment of the resistor. No changes occurred at all. On the other hand, the weight is compared to the conventional one,
The weight was reduced by approximately 30%.

Example B A good treatment effect was also obtained when the electrolyte solution used to treat the carbon film in Example A was a 1% aqueous sodium hydroxide solution, and a copper wire was soldered to the electrode part of the resistor. When the adhesion strength was measured, it was 2.0 Kg/mm ² .

Example C A low-melting glass frit was applied to the center of the same untreated carbon film resistor as used in Example A, with a distance of 2 mm removed from each end, and the glass was protected by heating to 600°C in nitrogen. A film was applied. Next, this resistor was heated to 550°C in air to make the exposed carbon film hydrophilic. Thereafter, both ends of the resistor were plated with electroless copper using a conventional method, and then placed in a barrel plating device for electroplating with copper to obtain a resistor having copper electrodes on both ends.

Example D A resol-type phenol resin was applied to the center of the same untreated carbon film resistor as used in Example A, leaving 2 mm from both ends, dried at 150°C for 10 minutes, and then placed in a vacuum container. Put it inside, 5×10 ^-1 torr
Surface treatment was performed by direct current sputtering in air. Next, resol type phenolic resin was applied to the center of the resistor again, and after curing at 180℃ for 30 minutes,
Electrodes were formed in the same manner as in Example C. The adhesion force of this electrode to the resistor was 2.5 Kg/mm ² .

Example E In Example D, the same results as in Example D were obtained when a 12.7 MHz high frequency power source was used as the discharge power source and the carbon film was treated in argon at 5×10 ⁻⁴ torr.

Example F In Example D, when a chlorinated fluorinated alkyl (trade name: DAIFLON, manufactured by Daikin Corporation) was used instead of air to treat the carbon film, the same treatment effect as that of air was obtained.

In Examples A to F, the explanation was mainly about nickel and copper plating, but by adopting the above carbon film treatment method, gold, copper plating, etc.
Electroless plating of silver, palladium, platinum, tin, solder, and others can also be applied.

As described above, by the method of manufacturing a carbon film resistor of the present invention, metal plating debris can be easily formed on the surface of pyrolytic carbon, which is inherently water repellent and difficult to directly apply electroless plating to.

Furthermore, the carbon film resistor manufactured by the method of the present invention is small and lightweight, and has high reliability since the electrodes are in full contact with the carbon film.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional carbon film resistor, Figure 2 is a cross-sectional view of a conventional carbon film resistor.
The figure is a schematic diagram of an anodizing apparatus used in an embodiment of the method of the present invention, and FIG. 3 is a sectional view showing an example of a carbon film resistor manufactured by the method of the present invention. 4... Electrolyte solution, 5... Carbon film resistor, 6
... Cathode, 7 ... Insulator (insulating base), 8 ... Carbon film, 9 ... Electrode (metal plating scrap).

Claims (1)

[Claims] 1. A step of forming a protective film on the surface of the carbon film formed on the surface of the insulating substrate except for the portion where the electrode is to be formed, and making the surface of the carbon film not covered with the protective film hydrophilic. and a step of plating metal on the surface of the hydrophilic carbon film to form electrodes on the carbon film. 2. The method of manufacturing a carbon film resistor according to claim 1, wherein the surface of the carbon film is made hydrophilic by anodizing in an electrolyte solution. 3. The method of manufacturing a carbon film resistor according to claim 1, wherein the surface of the carbon film is made hydrophilic by heating in air. 4. The method of manufacturing a carbon film resistor according to claim 1, wherein the surface of the carbon film is made hydrophilic by electric discharge in a low vacuum gas. 5. A method for manufacturing a carbon film resistor according to claim 1, wherein metal is plated on the surface of the carbon film by an electroless plating method. 6. The method of manufacturing a carbon film resistor according to claim 1, wherein metal is plated on the surface of the carbon film by an electroless plating method and subsequently an electroplating method.