JP2712726B2 - Positive characteristic thermistor heating element and method of manufacturing the same - Google Patents

Description

The present invention relates to a positive temperature coefficient thermistor heating element and a method for manufacturing the same.

[Conventional technology]

As a conventional positive temperature coefficient thermistor heating element, for example,
No. 57-63790.

In this PTC thermistor heating element, an aluminum electrode having an uneven surface is formed on the surface of the PTC thermistor element by thermal spraying.

By utilizing the convex portion of the aluminum electrode, the electrical conduction between the PTC thermistor element and the metal radiator is maintained, and the insulating adhesive provided in the concave portion of the aluminum electrode forms the PTC thermistor element. Adhesion and fixation with a metal radiator are performed.

[Problems to be solved by the invention]

In this conventional device, electrical continuity between the positive temperature coefficient thermistor element and the metal radiator is performed by the convex portion of the aluminum electrode.

However, the unevenness of the aluminum electrode surface is
When thermal spraying is performed, the unevenness is formed without controlling the size, and the size varies.

Therefore, especially with the variation of the convex portion of the aluminum electrode, the variation of the contact resistance between the convex portion of the aluminum electrode and the metal radiator increases, and a stable contact resistance cannot be obtained.

And, since the contact resistance between the convex portion of the aluminum electrode and the metal radiator cannot be stably obtained, when a voltage is applied to the metal radiators at both ends, the voltage is applied to a portion where the contact resistance is small. There is a problem that local heating occurs due to the concentration, which makes it difficult to control the temperature of the PTC thermistor heating element.

Therefore, the present invention provides a positive-characteristic thermistor heating element capable of stably obtaining a contact resistance between a positive-characteristic thermistor element and a metal radiator.

[Means for solving the problem]

Means for Solving the Problems In order to solve the above object, according to the present invention, a plate-like PTC thermistor element, metal electrodes provided on both main surfaces of the PTC thermistor element, and a conductor provided on the surface of the metal electrode A positive temperature coefficient thermistor heating element comprising particles and a metal radiator electrically connected to the conductive particles and bonded to the metal electrode by an adhesive provided between the conductive particles. Things.

Further, in the present invention, as a first method for producing the positive temperature coefficient thermistor heating element, a conductive metal electrode is formed on the surface of a plate-shaped positive temperature coefficient thermistor element, and conductive particles are formed on the surface of the metal electrode. An adhesive is applied to at least one of the opposing surfaces of the metal radiator and the metal electrode by spraying, so that the metal electrode and the metal radiator are electrically connected to each other through the conductive particles. Provided is a method for manufacturing a positive temperature coefficient thermistor element that is adhered and fixed to a substrate.

Further, as a second manufacturing method, a conductive metal electrode is provided on the surface of a plate-shaped positive temperature coefficient thermistor element, and conductive particles are sprayed on the surface of the metal electrode, and the metal electrode and the conductive particles are separated from each other. An adhesive is applied to at least one of the opposing surfaces of the metal radiator and the metal electrode so that the metal electrode and the metal radiator are electrically connected to each other through the conductive particles. Provided is a method for manufacturing a positive temperature coefficient thermistor element that is adhered and fixed to a substrate.

[Action]

In the present invention having the above-described configuration, electrical continuity between the positive temperature coefficient thermistor element and the metal radiator is performed by the convex portion formed by the conductive particles.

Therefore, the height of the protrusions can be easily controlled by the size of the conductive particles, so that the contact resistance between the positive temperature coefficient thermistor element and the metal radiator can be stably maintained.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First
FIG. 1 is a sectional view showing a first embodiment of the present invention. This first
In the figure, 1 and 3 are electrode plates, each of which is a power supply terminal.
Has 5,7. A radiation fin 11 is joined between the electrode plate 1 and the metal plate 9 by brazing or soldering to form a metal radiator. Similarly, a radiation fin 15 is joined between the electrode plate 3 and the metal plate 13 by brazing or soldering to form a metal radiator. The positive temperature coefficient thermistor 17 is connected to the metal plate 9 by the adhesives 19 and 21.
It is adhesively fixed between 13. FIG. 2 shows an enlarged cross-sectional view of a main part of FIG. On the main surface of the positive temperature coefficient thermistor element 17, a silver electrode 23 having a thickness of 2 μm to 20 μm was formed as a metal electrode.
Are printed and printed. On the surface of the silver electrode 23, copper particles 25 having a particle diameter of 10 μm to 100 μm are formed as conductive particles.
Are uniformly fixed by a thermal spraying method. As a result, as shown schematically in FIG. 3, on the surface of the silver electrode 23 uniformly distributed on the positive temperature coefficient thermistor element 17, the size of the protrusion is controlled by the conductive particles 25. 26 can be formed. The metal plate 9 and the conductive particles 25 provided on the silver electrode 23 are firmly joined by a silicon-based adhesive 19 as an adhesive having excellent heat resistance and thermal conductivity.

FIG. 2 shows only the main part of the metal radiator on the metal plate 9 side, but the metal plate 13 side has the same configuration.

Next, the present embodiment will be described according to the manufacturing order. First, a metal radiator is prepared. Therefore, the heat radiation fins 11 are joined between the rectangular electrode plate 1 and the metal plate 9 by brazing or soldering. Similarly, the electrode plate 3 and the metal plate
A radiator fin 15 is joined between the radiator and the radiator 13 by brazing or soldering to form a metal radiator. At this time, the electrode plate 1,
3, copper is used for the metal plates 9 and 13, and the radiation fins 11 and 15, and the thickness of the metal plates 9 and 13 is 2 μm to 20 μm.

Next, on both main surfaces of the plate-shaped positive temperature coefficient thermistor element 17,
A silver electrode 23 having a thickness of 2 μm to 20 μm is formed by printing or printing.

Next, copper conductive particles 25 are uniformly distributed on the surface of the silver electrode 23 by a thermal spraying method and are baked at the same time as the silver electrode 23 to form a projection 26. Here, the particle size of the copper conductive particles 25 is 10 μm to 100 μm, and the reason will be described later.

Next, the metal plate 9 and the metal plate 9
Silicone adhesives 19 and 21 having excellent heat resistance and heat conductivity are applied evenly to the surface of 13. As shown in FIG. 1, several thermistor elements 17 each having a projection made of conductive particles are sandwiched between the metal radiators through the adhesives 19 and 21 in parallel. 1.0 or more from above
A pressure of 5.0 kg / cm ² is applied to bond and fix.

By using the above method when the adhesives 19 and 21 are used, the adhesives 19 and 21
Workability is improved as compared with the case of applying to the side. That is, when the adhesive is applied to the surfaces of the metal plates 9 and 13, the electrode plates 1, 3 and the radiation fins 11, 15 can be held and applied.
The coating is easier than the coating on the positive characteristic thermistor element 17 side. When an adhesive is applied to the positive temperature coefficient thermistor element 17 side, it must be applied to each of the positive temperature coefficient thermistor elements 17.
By applying the adhesives 19 and 21 to the surfaces of the first and second adhesives, the adhesive need only be applied once.

In this embodiment having the above-described configuration, when power is supplied to the power supply terminals 5 and 7 from the external power supply 30, the power supply terminals 5 and 7 are composed of the electrode plates 1 and 3, the radiating fins 11 and 15, the metal plates 9 and 13, and the conductive particles 25. A current is supplied to the positive temperature coefficient thermistor element 17 via the convex portion 26 and the silver electrode 23, and the positive temperature coefficient thermistor element 17 generates heat. The heat generated in the positive temperature coefficient thermistor element 17 is transmitted to the metal radiator through the adhesives 19 and 21,
That is, the heat is transmitted to the metal plates 9 and 13, the radiation fins 11 and 15, and the electrode plates 1 and 3, and radiates heat from the metal radiator. Here, the thickness of the adhesives 19 and 21 is determined in advance by the silver electrode.
It is determined by selecting the particle size of the conductive particles 25 formed on the surface of 23, and has excellent adhesive strength, heater output, and excellent conduction rate.

Next, FIG. 4 is a graph showing the relationship between the heating element output ratio and the non-defective conduction rate when the particle size of the conductive particles 25 is changed in this embodiment. As can be seen from this graph, when the particle size of the conductive particles is 20 μm or less, the yield rate is low as indicated by the broken line. The reason for this is that the protrusions of the conductive particles 25
26 is low and the valley 27 is shallow, the adhesive 19 is almost pushed out from between the metal plate 9 and the silver electrode 23 when the metal radiator is bonded by applying pressure. 9
It is considered that the adhesion between the electrode and the silver electrode 23 becomes weak, resulting in a failure. The same applies to the relationship between the metal plate 13 and the silver electrode 23. In FIG. 4, when the particle size of the conductive particles becomes 120 μm or more, the output ratio of the heating element decreases because the conductive particles
Since the difference in the distance between the convex portion 26 and the valley portion 27 of FIG. 25 is large, that is, the distance between the metal plate 9 and the silver electrode 23 is large and the thickness of the adhesive layer is large, the heat generated in the PTC thermistor element 17 is large. Is difficult to transmit to the metal heat radiator including the metal plate 9.

In this embodiment, silver was used as the metal electrode.
Assuming that the contact resistance when 26 is directly formed on the positive characteristic thermistor element 17 is a predetermined value, any other conductive metal having a contact resistance smaller than this predetermined value may be used, for example, brass.

Next, FIG. 5 shows a graph comparing the effect of the present embodiment with the effect of the conventional device. In the positive temperature coefficient thermistor heating element, the heating element output changes depending on the amount of air passing through the positive temperature coefficient thermistor heating element. As shown in FIG. 5, in this embodiment, the output of the heating element is improved and the pressure loss is reduced with respect to the same air volume as compared with the conventional one. This is because by controlling the thickness of the adhesive layer by the particle size of the conductive particles, the contact resistance between the PTC thermistor element and the metal radiator can be stabilized, and the uniform and thin adhesive This is because the agent layer was formed, and the heat generated by the positive temperature coefficient thermistor element was efficiently transmitted to the metal radiator. Further, the pressure loss of the prior art disclosed in Japanese Patent Publication No. 1-268468 was higher than that of the present embodiment because of a predetermined pressing force for pushing off the adhesive along a parallel wave type pattern or the like. This is because the plate pressure is increased in order to allow the radiation fin to withstand the pressing force. However, in the present embodiment, the convex portion 26 of the conductive particle is attached to the adhesive, and the adhesive displaced by the peak portion 26 only needs to move to the valley portion 27 on the side. The pressing force can be reduced as compared with the conventional one, and the thickness of the radiation fin can be reduced. Therefore, the pressure loss of this embodiment can be reduced as compared with the conventional example.

As described above, according to the present embodiment, since the thickness of the adhesive could be controlled by the particle size of the conductive particles, the contact resistance between the PTC thermistor element and the metal radiator was stabilized. In addition, a uniform and desired thickness of the adhesive layer can be formed, the heat generated by the PTC thermistor is efficiently transmitted to the metal radiator, and the electrical connection between the PTC thermistor and the metal radiator is made possible. Good contact is also well maintained. In addition, since the convex portion made of the conductive particles is on a point, not on a line or a surface, it is easy to push the adhesive away from the adhesive. Thus, there is an effect that the thickness of the heat radiation fin can be reduced. Furthermore, there is also an effect that there is no need to process the shape of the metal radiator or the positive temperature coefficient thermistor itself.

Next, a second embodiment of the present invention is shown in FIG. The greatest feature of this embodiment is that the manufacturing method is slightly different from that of the first embodiment. That is, in the first embodiment, the silver electrode
23 was printed on the surface of the positive temperature coefficient thermistor element 13, and after baking, conductive particles were formed thereon by spraying.In this embodiment, however, the silver electrode 23 was formed on the surface of the positive temperature coefficient thermistor 17. Is printed, the conductive particles 25 on the spheres are uniformly dispersed in an undried state, and thereafter, printing is performed integrally. According to the manufacturing method as in this embodiment,
The same effects as in the first embodiment can be obtained.

Next, a third embodiment of the present invention is shown in FIG. In this embodiment, after printing and baking a silver electrode 23 on the surface of the positive temperature coefficient thermistor 17, conductive particles 33 such as copper having a particle size of 10 μm to 100 μm are mixed in advance in the electrode paste 35 and sufficiently expanded. In the soldered state, printing is performed on the silver electrode 23 through a screen, and a projection made of conductive particles is formed by scattering a solvent in the electrode paste 35 during printing.

In each of the embodiments described above, copper is used as the conductive particles. However, other materials may be used as long as they are excellent in heat resistance and heat conductivity and have low contact resistance, for example, brass.

〔The invention's effect〕

As described above, according to the present invention, since the convex portion made of conductive particles is provided between the PTC thermistor element and the metal radiator, the contact resistance between the metal radiator and the PTC thermistor element is increased. Can be obtained stably.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing a first embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of a main part of FIG. 1, and FIG. 3 explains the concept of a projection made of conductive particles of the present invention. FIG. 4 is a characteristic diagram in the case where the particle size of the conductive particles is changed in the first embodiment, and FIG. 5 is a diagram showing a positive temperature coefficient thermistor heating element in the first embodiment and a conventional example. Characteristic diagram for comparing
FIG. 7 is a sectional view of a principal part for explaining a second embodiment of the present invention, and FIG. 7 is a sectional view of a principal part showing a third embodiment of the present invention. 1,3 …… electrode plate, 9,13 …… metal plate, 11,15 …… radiation fin, 1
7 ... Thermistor element, 19,21 ... Adhesive, 23 ... Metal electrode, 26 ... Protrusion.

Continuation of the front page (56) References JP-A-57-63790 (JP, A) JP-A-57-109283 (JP, A) JP-A-58-14483 (JP, A)

Claims (5)

(57) [Claims] 1. A plate-like PTC thermistor element, metal electrodes provided on both main surfaces of the PTC thermistor element, conductive particles provided on the surface of the metal electrode, and the conductive particles A positive temperature coefficient thermistor heating element, comprising: a metal heat radiator electrically connected to the metal electrode by an adhesive provided between the conductive particles. 2. The PTC thermistor heating element according to claim 1, wherein said conductive particles have a particle size of 10 to 100 μm. 3. A conductive metal electrode is formed on the surface of a plate-shaped PTC thermistor element, and conductive particles are provided on the surface of the metal electrode by thermal spraying. A method of manufacturing a positive temperature coefficient thermistor element, comprising: applying an adhesive to at least one surface; and bonding and fixing said metal electrode and said metal heat radiator so as to be electrically conducted through said conductive particles. . 4. A conductive metal electrode is provided on the surface of a plate-shaped positive temperature coefficient thermistor element, conductive particles are sprayed on the surface of said metal electrode, and said metal electrode and said conductive particles are integrally baked. An adhesive is applied to at least one of the opposing surfaces of the metal radiator and the metal electrode, and the metal electrode and the metal radiator are bonded and fixed so as to be electrically connected via the conductive particles. A method for producing a positive temperature coefficient thermistor element. 5. The method of manufacturing a positive temperature coefficient thermistor heating element according to claim 3, wherein said conductive particles have a particle size of 10 to 100 μm.