JPH09213454A - Lead wire terminal connecting structure of thin plate-shaped far infrared radiation heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin plate-shaped far infrared radiation heater having lead wire connecting structure which is simple but has high safety, and high reliability by applying both of a conductive inorganic adhesive and an insulating inorganic adhesive to the connecting part of lead wire terminals. SOLUTION: In an aluminum thermal splay electrode 7 of a thin plate-shaped far infrared radiation heater (51: a heat generating layer, 6: an insulating layer) using aluminum silicate as a main component and Si or FeSi as a conductive material, a Kovar plate to which a lead wire is welded is bonded to the surface of the electrode 7 with a conductive inorganic adhesive 8, and the surface of a terminal connecting part is coated with an insulating inorganic adhesive 9, then the adhesive 9 is solidified. As the conductive material of the conductive inorganic adhesive, Ag or Ni powder is used, and as the insulating filler of the insulating inorganic adhesive, zircon (ZrSiO4 ) and magnesia (MgO) are used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead wire terminal joining structure of a ceramic thin plate far infrared heater used in, for example, a heater or a dryer.

[0002]

2. Description of the Related Art Far-infrared heaters radiate radiant heat energy in the far-infrared region at a spectral emissivity (ε) of about 0.8, which is close to that of a black body, and provide efficient heating. It is widely used in a wide range of fields. Particularly, the far infrared heater disclosed by the present applicant (Japanese Patent Laid-Open No. 63-307682) has Si or FeS as a conductive material in a ceramic insulating and heat resistant structural material.
This is a resistance heating element containing i in an amount of 5 to 60% by weight, and the far-infrared radiator itself shaped into an arbitrary shape can directly cause resistance heating, so that it is easy to design a heater and excellent in a small heat capacity. It has the features of rapid heating and sufficient thermal efficiency. Further, since the heater can easily form an arbitrary shape, the thin plate far infrared heater disclosed by the present applicant (Japanese Patent Laid-Open No. 6-208883) has a doctor blade method of 0.5 to 2.
A thin plate of about 0 mm is possible. With respect to the electrodes of the thin plate heater, an aluminum film is attached to the cross sections of both ends of the heating element by gas spraying. When a metal other than aluminum, for example, brass or nickel is attached as the sprayed metal, the sprayed surface is peeled off due to the difference in thermal expansion coefficient between the heating element and the sprayed metal. Aluminum, which is a highly ductile and soft material, absorbs the stress due to the difference in the coefficient of thermal expansion from the present ceramic element, and does not peel off the sprayed surface even when heat is generated by a cycle load. Conventionally, an electrode structure is employed in which an aluminum film is attached to the cross-sections of both ends of the thin plate-shaped heater by gas spraying, and sandwiched by a stainless steel electrode clip as shown in FIG. 6 and brought into contact with the aluminum sprayed film. Was there. In addition, soldering or brazing of a lead wire on the aluminum sprayed electrode surface of the present ceramic heating element is also under study.

[0003]

However, in the electrode structure as described above, since the aluminum spray electrode and the electrode clip are in point contact with each other, when the heater is heated by a cycle load, the thermal expansion coefficient of both materials is increased. From the difference of
The contact resistance is generated in the contact portion to locally overheat, and as a result, the sprayed film is peeled off to shorten the life of the heater. Further, in the above-mentioned electrode structure, it is difficult to design the shape of the electrode clip for a small heater for heating a minute portion. Further, as a method other than the above, a method of directly soldering and brazing a lead wire to an aluminum sprayed surface has been studied. For soldering, an aluminum braze having a melting temperature of about 300 ° C. at the maximum is used, so that the maximum operating temperature of the present heating element is 500 ° C., which is not a suitable method. On the other hand, regarding brazing, the melting temperature of Al-Si system, Al-Mg system, etc. is 700 ° C.
A method of joining a lead wire to an aluminum sprayed surface using a brazing material of a certain degree is used. However, if the main joining is carried out by heat treatment in the atmosphere, the sprayed aluminum film is oxidized and the brazing material does not get wet. Therefore, a method of brazing in vacuum is usually employed. The brazing process in a vacuum requires an expensive vacuum furnace and has a drawback that the cost and productivity are not suitable. Further, as a simple method for compensating for various drawbacks caused by the vacuum heating, a method of joining a lead wire to an aluminum sprayed surface by vibration by ultrasonic waves is disclosed in Japanese Patent Laid-Open No. 141978/1992. However, it is known that when the above-mentioned joining method is used for joining the lead wire of the present heating resistor, minute cracks are generated on the ceramic element side of the lead wire joining portion and the joining strength is reduced. The present invention was developed to solve such problems, and an object thereof is to provide a thin plate far-infrared heater having a lead wire terminal joining structure which is simple, highly safe and reliable.

[0004]

That is, according to the present invention, in an aluminum sprayed electrode of a thin plate far-infrared heater containing aluminosilicate as a main component and Si or FeSi as a conductive material, a conductive inorganic adhesive is adhered to the surface of the electrode. A thin plate far-infrared heater characterized by having a structure in which a Kovar plate with lead wires welded with an adhesive is adhered, and a structure in which the surface of the terminal joint is coated with an insulating inorganic adhesive and solidified. Is a lead wire terminal joining structure. In the present invention, the conductive adhesive is a paste-like inorganic adhesive containing Ag or Ni in the conductive material, and is solidified by heat treatment at 90 ° C. after coating. The heat resistant temperature of this adhesive after solidification is 900 ° C for Ag-containing products and 670 ° C for Ni-containing products. Both adhesives have a heater temperature of 500 ° C.
Has sufficient heat resistance. The insulating inorganic adhesive in the present invention is an inorganic coating agent containing zircon (ZrSiO ₄ ) and magnesia (MgO) powder as an insulating filler, and is solidified by heat treatment at 90 ° C. after coating. Heat resistance temperature after solidification is 150
It has a temperature of 0 ° C., has sufficient heat resistance at a heater temperature of 500 ° C., and also has an insulating property in the lead wire bonding portion, thereby increasing the bonding strength.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION By electrically bonding an aluminum sprayed surface to a ceramic and a Kovar plate having a thermal expansion coefficient close to each other with a conductive adhesive containing a heat-resistant conductive material such as Ag or Ni, the electrical conductivity between the electrode and the sprayed surface is improved. The effect of increasing the physical contact is obtained. However, since the heat resistance of the inorganic adhesive itself is not so high in this adhesive, the adhesive effect of the inorganic adhesive deteriorates when the heat generation temperature rises. Therefore, the above-mentioned electrode bonding portion is coated and solidified with an insulating inorganic adhesive to increase the bonding strength. This insulating inorganic adhesive is zircon (Z
It contains an insulating powder of rSiO ₄ ) and magnesia (MgO), has heat resistance up to 1500 ° C., has a high insulating property and a good withstand voltage, and has a coefficient of thermal expansion close to that of a heating element.
Therefore, according to the present invention, it is possible to provide a highly reliable heater for an electrode of a ceramic thin plate far-infrared heater used in, for example, a heater or a dryer by simple work and without deterioration of the electrode over time. Become.

[0006]

EXAMPLES The present invention will be described in more detail based on the following examples. (Example 1) Mullite raw material (3Al
40% by weight of ₂ O ₃ .2SiO ₂ ), 25% by weight of ball clay and 35% by weight of borosilicate glass having a softening point of 700 ° C. or higher were mixed to prepare a mixed raw material system. This mixed raw material system 100
An acrylic binder, a plasticizer, and ethanol were added to parts by weight, and the mixture was thoroughly kneaded with a ball mill and uniformly dispersed.
After the resulting slurry is vacuum-stirred, a sheet is formed using a doctor blade forming device and dried to a thickness of 0.5 m.
m green sheets were obtained. On the other hand, as a heater layer sheet, 30% by weight of Si raw material, 25% by weight of ball clay and 35% by weight of borosilicate glass having a softening point of 700 ° C. or more were blended to prepare a mixed raw material system. An acrylic binder, a plasticizer, and ethanol were added to 100 parts by weight of this mixed raw material system, which was sufficiently kneaded by a ball mill and uniformly dispersed. The obtained slurry was vacuum-stirred, then formed into a sheet using a doctor blade forming apparatus and dried to obtain a green sheet having a thickness of 0.25 mm. Width of the green sheet is 60mm,
Cut to a length of 110 mm, laminated and pressure-bonded with a press machine as shown in FIG. 1, and φ3.5 at both upper ends as shown in FIG.
mm through holes (4) were punched. After performing degreasing treatment in a nitrogen atmosphere at a temperature of 700 ° C., it was transferred to a tunnel furnace kept in the air atmosphere, heated at a rapid rate of 50 ° C./min, and fired at a temperature of 1250 ° C. to obtain a thickness of 1.8 m.
m, a width of 50 mm, and a length of 100 mm to obtain a thin plate-shaped far-infrared radiating resistance heating element. The vitreous protective film on the cross-sections of both ends of the resistance heating element was removed, and aluminum was sprayed by an electrospraying apparatus as shown in FIG. 3 to be fused to form an aluminum sprayed electrode (7). 0.3 mm Kovar plate (10) with lead wire (11) welded as shown in FIG.
The lead wire through the through hole of the resistance heating element,
Conductive inorganic adhesive (8) with aluminum sprayed electrode (7)
(Product name "PYRO-DUCT598" AREMCO △
Bonding was performed using a conductive agent: Ni) manufactured by PRODUCT. 2
Insulating inorganic adhesive (9) (trade name "Hyper Random C-919", Showa Highpolymer Co., Ltd.)
Was made into a paste by dissolving it in water, and was applied so as to coat the entire joint portion of the Kovar plate (10) as shown in FIG. Then, after performing natural drying for 2 hours, it was solidified by treating at 90 ° C. for 4 hours in a dryer. The obtained thin plate far-infrared heater with lead wire has a resistance of 19.8 Ω, a specific resistance of 0.16 Ωcm, and a surface temperature of 50 at 160 W (70 V).
It was possible to generate heat at 0 ° C, and the heat generation distribution was also good. Further, as a result of measuring the spectral emissivity at each wavelength by heating the surface temperature to 500 ° C., it was confirmed that far infrared rays of 3 to 30 μm were efficiently radiated. The heater was subjected to a load heat generation test in a cycle of 10 minutes on-10 minutes off. Load power is 160W, surface temperature is 500
The results are shown in Table 1. (Example 2) The conductive inorganic adhesive of Example 1 was used as the conductive material A.
Conductive inorganic adhesive containing g (trade name "PYRO-D
Instead of UCT597 "AREMCOΔPRODUCT), the same insulating inorganic adhesive and lead wire were used to produce a thin plate far-infrared heater. With 20.6Ω, specific resistance 0.17Ωcm, and 160 W (70 V), it was possible to generate heat at a surface temperature of 500 ° C., and the heat generation distribution was also good.
A load heat generation test with a -10 minute OFF cycle was performed.
The load power is 160W and the surface temperature is 500 ° C.
The results after 00 hours are also shown in Table 1. (Comparative Example 1) The same resistance heating element as in Example 1 was produced by performing doctor blade molding, green sheet processing, lamination, degreasing and firing under the same composition and conditions as in Example 1. The vitreous protective film on the cross-sectional heating layer at both ends of the resistance heating element was removed, and aluminum was sprayed with a width of 5 mm on both ends to form an aluminum sprayed electrode (7) as shown in FIG. As shown in FIG. 6, the aluminum sprayed electrode (7) was replaced with SUS.
The electrode clip (12) made of aluminum was sandwiched and the lead wire (13) was joined to this electrode clip (12). The obtained thin plate-shaped far-infrared heater with a lead wire has a resistance of 18.
It was 9Ω and the specific resistance was 0.15Ωcm. As with Example 1, the heater was subjected to a load heat generation test in a cycle of 10 minutes ON-10 minutes OFF. The load power is 160W,
The surface temperature was 500 ° C., and the results after 1000 hours are also shown in Table 1.

[0006]

[Table 1] From Table 1, a structure in which a Kovar plate having lead wires welded thereto with a conductive inorganic adhesive is adhered to the surface of an aluminum sprayed electrode, and the surface is solidified with an insulating inorganic adhesive to be bonded to a lead terminal Regarding the heaters of Examples 1 and 2, no change in resistance occurred even after 1000-hour cycle load heat generation. Also, in terms of appearance, there were no problems such as peeling of terminals and disconnection of lead wires, which were good results. On the other hand, in the heater of Comparative Example 1 having an electrode structure in which a stainless steel electrode clip is sandwiched between aluminum sprayed films and brought into contact with the aluminum sprayed electrode, the resistance is increased by 9.52% after 1000 hours cycle load heat generation,
It was found that the cause of the increase in resistance was the aluminum sprayed electrode part. Further, as a result of observing the aluminum sprayed surface with the electrode clip removed, it was found that the sprayed surface of the clip contact portion was peeled off.

[0008]

As described above, according to the present invention, in the electrode portion of the thin plate far-infrared heater containing aluminosilicate as a main component and Si or FeSi as a conductive material, the electrode is not deteriorated with time and is highly reliable. It is possible to provide a long-life heater.

[Brief description of drawings]

FIG. 1 is a perspective view showing a method of stacking green sheets.

FIG. 2 is a plan view of processing a through hole of a laminated green sheet.

FIG. 3 is a perspective view showing electrode formation of the heating resistor of the present invention by aluminum spraying.

FIG. 4 is a cross-sectional view showing an electrode structure for joining lead wires of the present invention.

FIG. 5 is a perspective view showing electrode formation of a conventional resistance heating element by thermal spraying of aluminum.

FIG. 6 is a cross-sectional view showing an electrode structure for conventional lead wire bonding.

[Explanation of symbols]

 1. Insulation layer green sheet 2. Green sheet for heating layer 3. Laminated green sheet 4. Through hole 5. Heating layer 6. Insulating layer 7. Aluminum sprayed electrode 8. Conductive inorganic adhesive 9. Insulating inorganic adhesive 10. Kovar board 11. Lead wire 12. Electrode clip 13. Lead wire 14. Thin plate far infrared heater

Claims (2)

[Claims] 1. An aluminosilicate as a main component, containing Si
Alternatively, in an aluminum sprayed electrode of a thin plate far infrared heater using FeSi as a conductive material, a structure in which a Kovar plate having lead wires welded to the surface of the electrode is bonded to the surface of the electrode, and an insulating inorganic adhesive The lead wire terminal joining structure of the thin plate far-infrared heater, which has a structure in which the surface of the terminal joining portion is coated and solidified. 2. A thin plate far infrared ray according to claim 1, wherein the conductive material of the conductive inorganic adhesive contains Ag or Ni powder, and ZrSiO ₄ and MgO are contained in the components of the insulating inorganic adhesive. Heater lead wire terminal joint structure.