JPH09199302A - Chip thermistor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the change of a resistance value due to the alteration of a conductive polymer layer by providing a first electrode layer having a first opening in the one-side part, a conductive polymer layer and a second electrode layer having a second opening in the side part on the opposite side to the first opening. SOLUTION: A first electrode layer 2 made of a phenol series conductive resin and having a first opening 3 is provided in the one-side part on the upper surface of a substrate 1. A conductive polymer layer 4 comprising a composition of a crystalline polymer and a conductive particle is provided in the upper surfaces of the first electrode layer 2 and the first opening 3. In the upper surface of the conductive polymer layer 4, a second electrode layer 5 made of a phenol series conductive resin and having a second opening 6 in the side part on the opposite side to the first opening 3. Further, a protective layer 7 made of an epoxy series insulating resin is provided, and an end surface electrode 8 is provided. Therefore, the change of a resistance value due to the alteration of a conductive polymer layer is reduced, the divergence of a connection part between an electrode and a metal terminal is reduced at the time of mounting it on a printed circuit board.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a PTC (Positive
The present invention relates to a chip type PTC thermistor using a conductive polymer having a temperature coefficient and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a PTC thermistor using a conductive polymer having PTC characteristics in which carbon black or metal particles are dispersed in a crystalline polymer has been known. P
The TC characteristic is that the crystalline polymer rapidly changes in volume from a crystalline state to an amorphous state at the melting point, so that the spacing between the conductive particles dispersed in the crystalline polymer is widened, resulting in contact between the particles. This is caused by the sudden increase in resistance.

An electric device including a conductive polymer which is a conventional PTC thermistor will be described below as an example.

Japanese Patent Application Laid-Open No. 62-98601 discloses a conventional electric device containing a conductive polymer, which has at least two electrodes and a conductive polymer element, and at least one of the electrodes is a conductive polymer element. Those that are in direct physical contact are disclosed.

A conventional electric device will be described below. The conductive polymer comprises a particulate conductive filler dispersed in an organic polymer and exhibits what is known as PTC (Positive Temperature Coefficient) behavior. Further, the electrodes used together with the conductive polymer having the PTC property include a single wire, a metal foil, a metal sheet, etc. Such a metal foil etc. is electrically connected to both surfaces of the conductive polymer layer by soldering. It had been.

The electric device configured as described above is
It is mounted on a printed circuit board of an electric / electronic device. When an abnormality such as a short circuit occurs in the circuit, the current flowing through the circuit is limited to a predetermined current or less by a rapid increase in resistance value due to self-heating. After that, it is used as a circuit protection element that recovers when an abnormality such as a circuit short circuit is removed.

[0007]

However, in the electric device which is the conventional PTC thermistor described above,
When the electrodes are soldered, the conductive polymer layer having PTC characteristics (hereinafter referred to as “conductive polymer layer”) is exposed to a temperature of 183 ° C. or higher, which is the melting point of solder, so that the conductive polymer layer is It may deteriorate and become higher than the desired resistance value, or the metal terminal may be displaced when the solder at the joint between the electrode and the metal terminal is melted when mounting this PTC thermistor electric device on the printed circuit board by the flow method etc. Therefore, there is a demand for a material that is less susceptible to the melting temperature of solder.

The present invention provides a PTC thermistor and a method for manufacturing the PTC thermistor, in which the resistance value hardly changes due to the deterioration of the conductive polymer layer and the joint portion between the electrode and the metal terminal is not displaced during mounting on the printed circuit board. The purpose is.

[0009]

In order to achieve the above object, the present invention provides a first electrode layer provided on one side of a substrate so as to have a first opening, A conductive polymer layer having PTC characteristics provided on the upper surface of the first electrode layer and the first opening, and a second conductive film on the upper surface of the conductive polymer layer on the side opposite to the first opening. And a second electrode layer provided so as to have the opening.

A first electrode layer is formed so as to have a first opening on one side of the upper surface of the substrate, and then on the upper surface of the first electrode layer and the first opening. A conductive polymer layer having PTC characteristics is formed, and then a second electrode layer is formed on the upper surface of the conductive polymer layer so as to have a second opening on a side opposite to the first opening. It is formed and manufactured.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention comprises: a substrate; and a first electrode layer provided so as to have a first opening on one side of an upper surface of the substrate. , The first
A conductive polymer layer having PTC characteristics provided on the upper surface of the electrode layer and the first opening, and a second conductive film on the upper surface of the conductive polymer layer on the side opposite to the first opening. A second electrode layer provided so as to have an opening, a protective layer provided on the upper surfaces of the second electrode layer and the second opening, and the first electrode layer on the end face of the substrate. And an end face electrode provided so as to be electrically connected to the second electrode layer. Therefore, the electrode and the terminal have an integrated structure, and even if heat is applied to the printed board during mounting, the joint between the electrode and the terminal is less likely to be displaced.

The invention described in claim 2 is the first invention.
Since the first and second electrode layers are made of a resin containing metal powder in the invention described above, there is an effect that there is little deviation in the bonded portion between the electrode and the conductive polymer layer.

[0013] The invention described in claim 3 is the first invention.
Since the protective layer is provided by the polyimide film in the invention described above, there is no need for alignment during printing, and the protective layer having an arbitrary thickness can be easily provided.

According to a fourth aspect of the invention, firstly, the first opening is formed on one side of the upper surface of the substrate.
A conductive polymer layer having PTC characteristics is formed on the upper surfaces of the first electrode layer and the first opening, and then the first conductive layer is formed on the upper surface of the conductive polymer layer. A second electrode layer is formed so as to have a second opening on the side opposite to the opening, and a protective layer is formed on the upper surface of the second electrode layer and the second opening. Next, primary substrate division is performed by cutting along the edges of the first and second openings into strips, and then the first and second strip-shaped substrates formed by the primary substrate division are separated. An end face electrode is formed on the end face having two openings so as to be electrically connected to the first electrode layer and the second electrode layer, and then the strip-shaped substrate is divided into individual secondary substrates. And manufactured.

By the above manufacturing method, the resistance value of the element can be lowered and the mass productivity is excellent.

(First Embodiment) A chip type PTC thermistor and a method of manufacturing the same according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional perspective view of a chip type PTC thermistor in one embodiment of the present invention.

In the figure, 1 is a substrate made of alumina or the like. Reference numeral 2 is a first electrode layer made of a phenolic conductive resin having a specific resistance of 10 ⁻³ Ω · cm or less, which is provided so as to have the first opening 3 on one side of the upper surface of the substrate 1. . Reference numeral 4 is a conductive polymer layer made of a composition of a crystalline polymer and conductive particles provided on the upper surfaces of the first electrode layer 2 and the first opening 3. 5 is a phenolic conductive material having a specific resistance of 10 ⁻³ Ω · cm or less, which is provided on the upper surface of the conductive polymer layer 4 so as to have the second opening 6 on the side opposite to the first opening 3. The second electrode layer is made of a conductive resin. Reference numeral 7 is a protective layer provided on the upper surfaces of the second electrode layer 5 and the second opening 6 and made of an epoxy-based insulating resin. Reference numeral 8 denotes an end face electrode provided on the end face of the substrate 1 so as to electrically connect the first electrode layer 2 and the second electrode layer 5.

The manufacturing method of the chip type PTC thermistor configured as above will be described below with reference to the drawings.

2 to 6 are process charts showing a method of manufacturing a chip type PTC thermistor in one embodiment of the present invention.

First, as shown in FIG. 2, a phenol-based conductive material having a specific resistance of 10 ⁻³ Ω · cm or less so as to have a first opening 3 on one side of the upper surface of a substrate 1 made of alumina or the like. The paste is screen-printed and cured at about 150 ° C. for about 30 minutes to form the first electrode layer 2.

Next, 51% by weight of high-density polyethylene having a crystallinity of 70 to 90% and 43% by weight of carbon black having an average particle diameter of 58 nm and a specific surface area of 38 m ² / g produced by the furnace method were used as an antioxidant. 1% by weight of the agent and 5% by weight of the coupling agent were mixed for about 20 minutes by a two-roll heated to about 150 ° C., and the mixture was taken out from the two-roll in a sheet form and had a thickness of about 0. The conductive polymer layer 4 is manufactured by cooling while pressing it with a metal plate so as to have a thickness of 2 mm, and cutting this into a size similar to that of the substrate 1.

Next, as shown in FIG. 3, the conductive polymer layer 4 prepared in the previous step is laminated on the upper surfaces of the first opening 3 of the substrate 1 and the first electrode layer 2, and the temperature is raised to about 150.degree. With a heated heat press machine, crimp at about 20 kg / cm ² for about 10 seconds,
The conductive polymer layer 4 is applied to the first opening 3 and the first opening 3 of the substrate 1.
To the electrode layer 2.

Next, as shown in FIG. 4, on the upper surface of the conductive polymer layer 4, the specific resistance 10 ^{−3 is formed} so as to have the second opening 6 on the side opposite to the first opening ^3. Screen-print a phenolic conductive paste of Ω · cm or less to about 120
The second electrode layer 5 is formed by curing at 30 ° C. for about 30 minutes.

Next, as shown in FIG. 5, the second electrode layer 5
An epoxy-based insulating resin is screen-printed on the upper surface of the second opening 6 and dried at about 120 ° C. for about 10 minutes to form the protective layer 7. In addition, the conductive polymer layer 4
Then, after irradiating about 20 Mrad of an electron beam in the electron beam irradiating device to crosslink the high-density polyethylene contained in the conductive polymer layer 4 with radiation, parallel to the first opening 3 and formed into strips by dicing. The primary substrate division for cutting is performed.

Next, as shown in FIG. 6, the first opening 3 and the second opening 3 of the strip-shaped substrate divided into the primary substrate in the previous step.
A phenolic conductive paste is applied to the end surface having the opening 6 of the above so as to be electrically connected to the first electrode layer 2 and the second electrode layer 5 and cured at about 120 ° C. for about 30 minutes. Then, the end face electrode 8 is formed by fixing the end face electrode 8 to the substrate 1. After this, the strip-shaped substrate is cut by dicing in a direction perpendicular to the cut surface of the primary substrate division, and the secondary substrate is divided into individual pieces.

Finally, the surface of the end face electrode 8 is nickel-plated or solder-plated to manufacture a chip type PTC thermistor.

The chip type PTC thermistor according to the embodiment of the present invention constructed and manufactured as described above was mounted on the printed circuit board by soldering by the reflow method. In visual inspection after mounting, there was no abnormality such as electrode displacement, and solder fillets between the end face electrodes and the printed circuit board were also sufficiently formed.

FIG. 7 is a diagram showing the relationship between the temperature and the resistance value of the chip type PTC thermistor in one embodiment of the present invention. The characteristics obtained in this figure are obtained by placing the chip type PTC thermistor in a constant temperature bath and measuring the resistance value when the temperature is raised to about 25 ° C to 150 ° C. The resistance value of this chip type PTC thermistor at room temperature (25 ° C.) is 0.6Ω, and it shows a low resistance value of 1Ω or less at room temperature. Further, since the resistance value changes abruptly at about 120 ° C. such as when a large current flows, the same effect as in the conventional case can be obtained.

In the embodiment of the present invention, the first electrode layer 2, the second electrode layer 5 and the end surface electrode 8 are made of a phenol-based conductive resin. It may be of a type,
Although the protective layer 7 is made of epoxy resin, a similar effect can be obtained even if it is made of phenol or polyester.

If the surfaces of the first electrode layer 2 and the second electrode layer 5 are made to have a surface roughness of 0.1 μm or more by plasma etching or blasting, the adhesive strength with the conductive polymer layer 4 is increased. Is something that can be done.

The same effect can be obtained by using a substrate made of phenol resin or the like instead of the alumina substrate.

Although it has been described that the end surface electrode 8 is nickel-plated and solder-plated after the secondary division, the same effect can be obtained even if nickel-plating and solder-plating are performed after the primary division and then the secondary division is performed. It is possible to obtain a chip type PTC thermistor.

(Second Embodiment) A chip type PTC thermistor and a method of manufacturing the same according to another embodiment of the present invention will be described below with reference to the drawings.

FIG. 8 is a sectional perspective view of a chip type PTC thermistor according to another embodiment of the present invention.

In the figure, 11 is a substrate made of alumina or the like. 12 is a specific resistance 10 ⁻³ Ω · which is provided so as to have the first opening 13 on one side of the upper surface of the substrate 11.
The first electrode layer is made of a phenol-based conductive resin having a size of cm or less. 14 is the first electrode layer 12 and the first opening 1
3 is a conductive polymer layer made of a composition of a crystalline polymer and conductive particles provided on the upper surface of the conductive polymer. Reference numeral 15 designates a specific resistance of 10 ⁻³ Ω · cm or less provided on the upper surface of the conductive polymer layer 14 so as to have a second opening (not shown) on the side opposite to the first opening 13. The second electrode layer is made of a phenolic conductive resin. Reference numeral 16 is an insulating resin portion made of an epoxy insulating resin provided on the upper surface of the second opening. Reference numeral 17 denotes the second electrode layer 15 and the insulating resin portion 1.
6 is a protective layer made of a polyimide film provided on the upper surface. Reference numeral 18 denotes the first electrode layer 12 on the end face of the substrate 11.
And an end face electrode provided so as to be electrically connected to the second electrode layer 15.

The manufacturing method of the chip type PTC thermistor configured as described above will be described below.

First, a phenolic conductive paste having a specific resistance of 10 ⁻³ Ω · cm or less is screen-printed so as to have a first opening 13 on one side of the upper surface of the substrate 11 made of alumina or the like, and First cure at 150 ° C for 30 minutes
The electrode layer 12 of is formed.

Next, 51% by weight of high-density polyethylene having a crystallinity of 70 to 90% and 43% by weight of carbon black having an average particle size of 58 nm and a specific surface area of 38 m ² / g produced by the furnace method were used as an antioxidant. 1% by weight of the agent and 5% by weight of the coupling agent were mixed for about 20 minutes by a two-roll heated to about 150 ° C., and the mixture was taken out from the two-roll in a sheet form and had a thickness of about 0. The conductive polymer layer 14 is manufactured by cooling while pressing the metal plate so as to have a thickness of 2 mm, and cutting this into a size similar to that of the substrate 11.

Next, the conductive polymer layer 1 produced in the previous step
4 to the first opening 13 of the substrate 11 and the first electrode layer 1
2 is laminated on the upper surface of the substrate 2 and heated by a heat press machine at about 150 ° C. and pressure-bonded at about 20 kg / cm ² for about 10 seconds to form the conductive polymer layer 14 in the first opening 13 of the substrate 11 and the first electric machine. Bond to layer 12.

Next, a urethane-based conductive paste is screen-printed on one surface of the polyimide film forming the protective layer 17 so as to have the second opening, and the paste is cured at about 150 ° C. for about 30 minutes to make the second. The electrode layer 15 of is formed.

Next, an epoxy-based insulating paste is printed in the second opening formed on the upper surface of the polyimide film in the previous step and cured at about 120 ° C. for about 10 minutes to produce the insulating resin portion 16. did. This is laminated on the conductive polymer layer 14 bonded on the substrate 11 and is pressed at about 20 kg / cm ² for about 10 seconds using a heat press machine heated to about 150 ° C. to form the second electrode layer 15 Then, the insulating resin portion 16 and the protective layer 17 are formed. Further, the conductive polymer layer 1
4 was irradiated with an electron beam of about 20 Mrad in the electron beam irradiation device to perform radiation crosslinking on the high-density polyethylene contained in the conductive wire polymer layer 14, and then in parallel with the first opening 13.
The primary substrate is divided into strips by dicing.

Next, the first electrode layer 12 and the second electrode layer 15 are formed on the end face having the first opening 13 and the insulating resin portion 16 of the strip-shaped substrate obtained by dividing the primary substrate in the previous step. A phenol-based conductive paste is applied so as to be electrically connected to, and cured at about 120 ° C. for about 30 minutes, and fixed to the substrate 4 to form the end face electrode 18. Then, the strip-shaped substrate is divided into individual secondary substrates by dicing in a direction perpendicular to the cut surface of the primary substrate division.

Finally, the surface of the end face electrode 10 is nickel-plated or solder-plated to manufacture a chip type PTC thermistor.

Chip type P constructed and manufactured as described above
When the relationship between the temperature and the resistance value of the TC thermistor is examined as in the first embodiment, the resistance value of this chip type PTC thermistor is 0.8Ω at room temperature (25 ° C.), which is as low as 1Ω or less at room temperature. It showed a resistance value. Further, since the resistance value changes abruptly at about 120 ° C. such as when a large current flows, the same effect as in the conventional case can be obtained.

In the other embodiment of the present invention, the polyimide film is used as the protective layer 17, but the same effect can be obtained by using a film such as PET.

[0047]

As described above, according to the present invention, there is little change in resistance value due to alteration of the conductive polymer layer, and the joint portion between the electrode and the metal terminal is less likely to be displaced during mounting on the printed circuit board. Can be provided.

It is also possible to provide a method of manufacturing a chip type PTC thermistor which is excellent in mass productivity.

[Brief description of drawings]

FIG. 1 is a chip PTC according to an embodiment of the present invention.
Cross sectional perspective view of the thermistor

[Fig. 2]

[Fig. 3]

[Fig. 4]

[Fig. 5]

FIG. 6

FIG. 7 is a diagram showing the relationship between the same temperature and resistance value.

FIG. 8 is a chip-type PT according to another embodiment of the present invention.
Sectional perspective view of C thermistor

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 1st electrode layer 3 1st opening part 4 Conductive polymer layer 5 2nd electrode layer 6 2nd opening part 7 Protective layer 8 End surface electrode

Claims (4)

[Claims] 1. A substrate, a first electrode layer provided so as to have a first opening on one side of an upper surface of the substrate, the first electrode layer and the first opening. A conductive polymer layer having PTC characteristics provided on the upper surface of the first conductive layer, and a second conductive layer provided on the upper surface of the conductive polymer layer on a side opposite to the first opening. 2 electrode layers,
A protective layer provided on the upper surface of the second electrode layer and the second opening, and provided on the end surface of the substrate so as to electrically connect the first electrode layer and the second electrode layer. Chip-type PTC thermistor having an end face electrode. 2. The chip type PTC thermistor according to claim 1, wherein the first and second electrode layers are made of a resin containing metal powder. 3. The chip type PTC thermistor according to claim 1, wherein the protective layer is a polyimide film. 4. A first electrode layer is first formed on one side of an upper surface of a substrate so as to have a first opening, and then an upper surface of the first electrode layer and the first opening is formed. A conductive polymer layer having PTC characteristics, and then forming a second electrode layer having a second opening on a side opposite to the first opening on the upper surface of the conductive polymer layer. Forming a protective layer on the upper surface of the second electrode layer and the second opening, and then cutting the substrate into strips along the ends of the first and second openings. Primary substrate division is performed, and then the first electrode layer and the second electrode layer are formed on the end face having the first and second openings of the strip-shaped substrate formed by the primary substrate division. A method of manufacturing a chip type PTC thermistor in which an end face electrode is formed so as to electrically connect to each other, and then the strip-shaped substrate is divided into individual secondary substrates. .