JPH07211516A - Chip-type thermistor and its production - Google Patents

Abstract

PURPOSE:To obtain a chip-type thermistor with a large mechanical strength by forming a chip body easily, completing the formation of insulation inorganic layer one time and adjusting resistance values precisely. CONSTITUTION:A surface electrode 11 for adjusting resistance value is formed on the end surface of a chip-shaped thermistor base body 10 excluding both end faces facing each other in the body 10, and the body 10 is entirely covered with an insulation inorganic layer 14. A wrapping electrode 16 is formed on both end parts of the body covered with the inorganic layer and plating layers 18 and 19 are further formed on the surface of the wrapping electrode. The wrapping electrode is formed by applying and baking a conductive paste containing a metallic powder and inorganic binding material in smaller area than the electrode 11 in a manner to wrap both end parts of the body. The thickness of the inorganic layer is 0.1-10mum and its melting point or softening point is higher than the baking temperature where an inorganic layer is formed into a wrapping electrode, and the inorganic layer in the base part of the paste partly reacts on the inorganic binding material and melts when the wraping electrode is formed, then it is absorbed into the wrapping electrode and disappears thereafter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip type NTC thermistor which is surface-mounted on a printed circuit board or the like and whose resistance value is precisely adjusted, and a method for manufacturing the same. More specifically, the present invention relates to a chip type thermistor in which a resistance value adjusting surface electrode is formed by printing on a green sheet and then cut into chips so that the resistance value can be precisely adjusted, and a manufacturing method thereof.

[0002]

2. Description of the Related Art As a method of manufacturing a chip type thermistor, the present applicant first adjusts the resistance value by printing and firing a silver paste or a silver / palladium alloy paste in a strip shape on both sides of a sintered sheet for a thermistor body. Forming a front surface electrode, printing and firing glass paste on both sides of this sheet to form a glass layer, then cutting the sintered sheet into strips in the direction orthogonal to the row direction of the front surface electrode, and cutting the glass surface on this cut surface. The paste is printed and baked to form a glass layer, and then the strip-shaped thermistor element is finely cut into chips in a direction perpendicular to the cut surface and along the center line in the width direction of the surface electrode. Silver paste or silver / palladium alloy paste is applied to both ends of the element body so as to wrap the cut surface of the thermistor element and fired to form a baking electrode, and this baking electrode is used as a base electrode. Proposed a method of forming a plating layer on the surface (JP-A-4-127401).

[0003]

However, in the above method, it is necessary to form the glass layer in two steps, and after cutting the extremely hard ceramic sintered sheet for the thermistor body into strips, This strip must be further cut into chips. Further, due to the change in shape of the work piece from the strip shape to the chip shape, great care must be taken in handling the work piece. For these reasons, the above method has a problem that the manufacturing process is complicated and the manufacturing cost is inevitably high.

An object of the present invention is to provide a chip type thermistor which can be easily processed into a chip body, an insulating inorganic material layer can be formed at one time, and a resistance value can be precisely adjusted, and a manufacturing method thereof. Another object of the present invention is to provide a method capable of manufacturing a chip type thermistor having a high sintered density and a high mechanical strength because a thermistor element body is produced by firing a chip-shaped green body.

[0005]

As shown in FIG. 1 and FIG. 2, a chip type thermistor 20 of the present invention includes a chip-type thermistor element body 10 and both end surfaces of the thermistor element body 10 opposite to each other. Resistance-value-adjusting surface electrodes 11 formed in pairs on the edges of the surface of the element body adjacent to the both end surfaces.
An insulating inorganic material layer 14 covering the entire surface of the thermistor element body 10 on which the surface electrodes 11 are formed, and outer envelope electrodes 16 formed on both ends of the thermistor element body 10 covering the inorganic material layer 14, Plating layers 18 and 19 formed on the surface of the envelope electrode 16. The characteristic structure is formed by coating the outer electrode 16 with a conductive paste containing a metal powder and an inorganic binder so as to cover both ends of the thermistor body 10 in an area smaller than that of the front electrode 11 and baking it. , The thickness of the inorganic layer 14 is 0.1 to 10 μm
In addition, the inorganic layer 14 has a melting point or a softening point higher than the firing temperature when the envelope electrode 16 is formed, and a part of the inorganic layer 14 in the base portion of the paste is the inorganic layer when the envelope electrode 16 is formed. It is configured so that the binder material is melted by reaction and absorbed by the outer envelope electrode 16 to disappear.

In addition to those shown in FIGS. 1 and 2, the chip type thermistor of the present invention has resistance value adjusting surface electrodes 11 on both end faces of the chip-shaped thermistor body 10 as shown in FIGS. 8 and 9. The chip-type thermistor 30 is formed in which the inclusion electrode 15 to be electrically connected is formed, and the entire surface of the thermistor element body 10 in which the surface electrode 11 and the inclusion electrode 15 are formed is covered with the insulating inorganic material layer 14.

The chip type thermistor of the present invention is shown in FIG.
As shown in FIG. 3, one surface resistance adjusting electrode 11 is formed on each edge of the chip-like thermistor element body 10 other than the opposite end surfaces of the chip-like thermistor element body 10. The chip type thermistor 40 is included.

Further, the chip type thermistor of the present invention is shown in FIG.
As shown in FIG. 9, the resistance-value-adjusting surface electrodes 11 on both surfaces of the opposing element bodies other than the opposite end surfaces of the chip-shaped thermistor element body 10 are not formed. Chip thermistor 6 in which one surface electrode 17 for locking the outer packaging electrode is formed
Including 0.

As shown in FIGS. 1 to 7, in the method of manufacturing the chip type thermistor 20, a resistance adjusting surface is formed by printing a plurality of strips of the first conductive paste on both surfaces of the thermistor element green sheet 21. The step of forming the electrode 11 and the green sheet 21 on which the surface electrode 11 is formed
1. A step of cutting the chip-shaped thermistor element body 10 into chips so that 1 is located on both edges, a step of firing the chip-shaped green body 23 to form the chip-shaped thermistor element body 10, and A step of coating the insulating inorganic layer 14 having a thickness of 0.1 to 10 μm, and the second conductive paste 25 containing the metal powder and the inorganic binder 25a at both ends of the chip-like thermistor element body 10 coated with the inorganic layer 14. Is applied so as to cover both ends of the thermistor element body 10 in an area smaller than the surface electrode 11, and the thermistor element body 10 applied with this paste 25 is fired at a temperature lower than the melting point or softening point of the inorganic layer 14. , The inorganic layer 14 of the base portion of the paste on the inorganic binder 25a of the applied paste.
Of the inorganic substance layer 14 by extinguishing a part of the inorganic material layer 14 by reaction melting to form the outer envelope electrode 16, and forming the plating layers 18 and 19 on the surface of the outer envelope electrode 16.

As shown in FIGS. 8 to 11, the manufacturing method of the chip type thermistor 30 is performed between the step of forming the chip-shaped thermistor element 10 and the step of coating the insulating inorganic substance layer 14 of the above manufacturing method. The method includes a step of applying the third conductive paste to both end surfaces of the chip thermistor element body 10 and baking the third conductive paste to form the internal electrodes 15 electrically connected to the resistance value adjusting surface electrodes 11.

The present invention will be described in detail below. (a) Manufacture of chip-like thermistor element body with front surface electrode for resistance adjustment As shown in FIG. 3, first, a green sheet 21 (the same figure (a)) for the thermistor element body is prepared. The green sheet 21 is prepared by mixing one or more kinds of oxide powders of metals such as Mn, Fe, Co, Ni, Cu and Al, calcining and crushing the mixture, and then adding an organic binder and a solvent. It is prepared by kneading to prepare a slurry, and film-forming and drying the slurry by a doctor blade method or the like. Next, the first conductive paste containing the noble metal powder and the inorganic binder is printed and dried on both surfaces of the green sheet 21 in a strip shape to form the resistance value adjusting surface electrodes 11 in multiple rows. Examples of the noble metal powder contained in this conductive paste include Ag, Au, Pd or Pt powder, or a powder obtained by mixing these powders. The surface electrodes 11 for resistance value adjustment are formed so as to face each other on both sides of the sheet 21, and then the green sheet 21 is placed at the center of the surface electrode 11 at the position of the arrow M using a dicing saw such as a cutting machine with a diamond blade. The strip-shaped green body 22 is formed by cutting along the broken line, which is a line (see FIG. 2B).
And (c)). Further, when the surface electrode 11 is cut at a position indicated by an arrow N along a broken line in a direction orthogonal to the cutting surface,
As shown in (d), a large number of chip-shaped green bodies formed in pairs on both edges of both surfaces of the chip-like thermistor element body 10 opposite to each other except for the opposite end surfaces thereof. 23 is obtained ((c), (d) in FIG.
(A)). As shown in FIG. 4 (b), after firing the chip-shaped green body 23 at about 1000 to 1400 ° C. for about 1 to 10 hours, or before firing, barrel polishing is performed to remove the chamfer of the sintered body. It is preferable to set aside. By this firing, the resistance adjusting surface electrode 11 is firmly fixed to the chip-shaped thermistor body 10. Further, if the chamfering is performed, a cutting burr after cutting is eliminated, and furthermore, the thermistor element body is less likely to be chipped or cracked in the subsequent steps, and as a result, variations in the electrical characteristics of the thermistor are reduced. When the barrel polishing process is performed, the thickness of the resistance-adjusting surface electrode before polishing is set to a sufficient thickness so as not to be worn by the barrel polishing process.

(B) Coating of a chip-like thermistor element body with an insulating inorganic material layer The obtained thermistor element body 10 has a thickness of 0.1 to 0.15 over the entire surface thereof.
10 μm, preferably 2 to 5 μm, more preferably 2 to
A 3 μm insulating inorganic layer is coated (FIGS. 1, 2 and 4 (c)). When it is thicker than 10 μm, the inorganic layer melted at the time of forming the envelope electrode described later is not completely absorbed in the envelope electrode, and the inorganic layer remains as an insulating film at the interface between the envelope electrode and the thermistor element body, so that the thermistor element of the envelope electrode is formed. Insufficient conductivity for the body. When the thickness is less than 0.1 μm, the function of protecting the thermistor element during the plating treatment described later and after the plating treatment is poor. An example of this insulating inorganic layer 14 is a SiO ₂ film or 50% by weight.
A thin film composed of the above SiO ₂ and the balance of one or more oxides of Al ₂ O ₃ , MgO, ZrO ₂ or TiO ₂ , or SiO ₂ , B ₂ O ₃ , Na ₂ O, Pb
Examples of the thin film include glass containing O, ZnO, or BaO as a main component and one or more oxides. The inorganic layer 14 needs to have a melting point or a softening point higher than the firing temperature when forming the envelope electrode described later. For example, when an Ag paste is baked as the envelope electrode, the baking temperature is 600 to 850 ° C., and therefore, a material having a melting point or a softening point higher than this temperature is selected. The reason for this is that if the melting point or softening point is significantly lower than the paste baking temperature, the inorganic material layer will float up on the electrode surface during paste baking, or thermistor bodies will stick together or the body and firing jig will yield. Is easily reduced.

Except for this requirement, the inorganic layer 14 is not particularly limited as long as it has resistance to plating and has a property of reacting with an inorganic binder contained in a conductive paste described later and melting. Or may be amorphous. However, the glass is crystalline and the inorganic layer 1
When 4 is crystallized glass, the bending strength of the thermistor is increased, which is preferable. The thermistor body is coated with an inorganic layer by a physical vapor deposition method (PVD method) such as a vacuum vapor deposition method, a sputtering method, an ion plating method, or a chemical vapor deposition method (C).
VD method). Among these, the sputtering method is preferable because it is suitable for mass production. In this sputtering apparatus, as shown in FIG. 5, a barrel 28 having a raking protrusion on the inner surface of the barrel is placed between a pair of horizontally arranged rollers spaced from each other, and the barrel 28 is placed at the center of the barrel. A target 29 made of an insulating inorganic material is provided independently of the barrel 28. In order to coat the inorganic material layer with this device, a large number of chip-like thermistor bodies are housed inside the barrel 28, and then a pair of rotating rollers 26 and 2 are used.
The barrel 28 is rotated slowly by rotating 7. In this state, a high voltage is applied to the target 29 to knock out particles made of an inorganic material. As a result, an insulating inorganic material layer is formed on the entire surface of the thermistor element in the barrel.
As the target 29, for example, quartz glass is used if the inorganic layer is a SiO ₂ film, and SiO ₂ , Al ₂ O ₃ , Mg is used.
O, ZrO ₂ , TiO ₂ , B ₂ O ₃ , Na ₂ O, PbO, Z
If it is a composite oxide film of nO, BaO or the like, these are formed into a disk shape by powder metallurgy, or they are melted and cooled to form a disk-shaped composite glass.

(C) Formation of outer electrode As shown in FIG. 4 (d), a second conductive paste containing metal powder and an inorganic binder on both end surfaces of the thermistor element body 10 coated with the insulating inorganic material layer 14. 25 is applied so as to cover both ends of the thermistor element body 10 in an area smaller than the resistance value adjusting surface electrode 11 and dried. If the surface electrode 11 is covered with an area larger than that of the surface electrode 11, the outer envelope electrode 16 to be described later becomes the surface electrode 1.
There is a risk of contacting the thermistor body 10 beyond 1,
This is because the function of the surface electrode 11 is impaired. This coating is preferably performed by a dipping method in which both ends of the thermistor element body are dipped in the second conductive paste. The metal powder contained in the conductive paste 25 may be a noble metal powder of Ag, Au, Pd or Pt, or a powder obtained by mixing these. An example of the inorganic binder contained in the conductive paste is Si
O _2, a major component _{B 2 O 3, Na 2 O} , PbO, and ZnO or any one or more oxides of BaO, borosilicate glass, zinc borate glass, borate cadmium glass Glass fine particles such as lead zinc silicate based glass can be used.

As shown in FIG. 6, an inorganic binder 25a is uniformly dispersed in the applied conductive paste 25. The inorganic binder 25a is an inorganic material that comes into contact with the paste 25 when the conductive paste is baked. It is necessary to have a property of reacting with the layer 14 and melting the inorganic layer 14 as shown in FIG. 7. As shown in FIGS. 4 (e) and 7, the conductive paste 25 forms an outer envelope electrode 16 by baking, and the outer envelope electrode 16 is formed by the inorganic material layer 1 at the time of baking.
When part of 4 disappears, the thermistor body 10
Electrically connect to.

(D) Formation of plating layer A plating layer is formed on the surface of the envelope electrode 16 by electrolytic barrel plating. It is preferable that this plating layer has a double structure by forming a Ni plating layer 18 as shown in FIG. 4F and then forming an Sn plating layer 19 as shown in FIG. 4G. The Ni plating layer 18 improves solder heat resistance and prevents electrode erosion of the outer envelope electrode by solder, and
The plating layer 19 improves solder adhesion. 1 and 2
As shown in (1), the chip type thermistor 20 having the terminal electrode 12 including the outer envelope electrode 16 and the plating layers 18 and 19 is obtained.

(E) Fabrication of chip-type thermistor with resistance adjusting surface electrode and internal electrode The step of forming the chip-like thermistor body 10 shown in FIG. 10 (b) corresponding to FIG. 4 (b), and FIG. Between the step of covering the insulating inorganic material layer 14 shown in FIG. 10D corresponding to FIG. 10C, the third conductivity is provided on both end surfaces of the chip thermistor body 10 as shown in FIG. 10C. The surface electrode 11 for adjusting the resistance value is obtained by applying and drying the paste and then firing it.
The inclusion electrode 15 electrically connected to is formed. By interposing the inner electrode 15 between the thermistor body 10 and the outer electrode 16, the electrode area in contact with the thermistor body becomes constant, and the variation in the electrical characteristics of the thermistor is reduced.

Specifically, as shown in FIG. 11A, the inclusion electrode 15 is formed by using a holding plate 31 made of an elastic material, in which a large number of holding holes 31a for holding the thermistor body 10 are formed. To use. A loading plate 32 having an introduction hole 32a corresponding to the holding hole 31a is superposed on the holding plate 31, and a negative pressure is applied to the lower side of the plate 31 by a vacuum pump or the like to put the thermistor element body 10 into each holding hole 31a (Fig. 11 (b)). The introduction hole 32a is formed in a wide mouth so that the end surface of the thermistor element body 10 is the upper surface. After releasing the negative pressure state, each pin 33a is inserted from the upper side of the plate 31 into each holding hole 31a by a certain length by using the pushing tool 33 having the pushing pins 33a corresponding to the number of holes. The body 10 is projected from the lower surface of the plate 31. In this state, the holding plate 31 is turned upside down and screen-printed on the end surface of the thermistor element body 10 which has a uniform height as shown in FIG. Figure 11
In (c), 34 is a screen, 36 is a squeegee,
37 is a conductive paste. After the inclusion electrode 15 is formed, FIG. 1 corresponding to the process of FIGS.
As shown in FIGS. 8 and 9, through the steps of 0 (d) to 10 (h), the inner electrode 15, the outer electrode 16, the plating layer 1
The chip type thermistor 30 having the terminal electrode 12 composed of 8 and 19 is obtained.

(F) Preparation of Chip Type Thermistor with Surface Electrode for Resistance Value Adjustment of Another Embodiment (No. 1) As shown in FIG. 12B, the above-mentioned first conductive paste is formed on the upper surface of the green sheet 21. After the resistance-adjusting surface electrode 11 is formed by printing and drying in a strip shape, the first conductive paste is printed and dried in a strip shape on the lower surface of the sheet corresponding to the intermediate position of the surface electrodes 11 on the upper surface of the sheet to adjust the resistance value. The front surface electrode 11 is formed. After forming the surface electrodes 11 on both sides of the sheet, the green sheet 21 is cut along the broken line which is the center line of these surface electrodes 11 at the position of the arrow M, and as shown in FIG. If the surface electrode 1 is cut along a broken line in a direction orthogonal to the cut surface at a location.
As shown in FIG. 12 (d), one is formed on each of the opposite edges of both surfaces of the chip-like thermistor element body 10 other than the opposite end surfaces of the chip-like thermistor element body 10 that face each other. A large number of chip-shaped green bodies 23 are obtained. By processing the chip-shaped green body 23 in the same manner as in the method shown in FIG. 4, the chip-type thermistor 4 shown in FIG.
0 is obtained. 13, the same reference numerals as those in FIG. 2 indicate the same components.

(G) Preparation of Chip Type Thermistor with Surface Electrode for Resistance Value Adjustment of Another Form (Part 2) As shown in FIGS. 14 and 15, in this method, the above-mentioned first conductive material is formed on both surfaces of the green sheet 21. The conductive paste is printed and dried in the shape of a rectangular spot to form a large number of resistance value adjusting surface electrodes 11. These surface electrodes 11 are formed at opposite positions on both sides of the sheet. After forming the surface electrode, the green sheet 21 is cut along the broken line which is the center line of the surface electrode 11 at the position of the arrow M using a dicing saw, and at the position of the arrow N where the surface electrode 11 is not formed. It is cut along a broken line in a direction orthogonal to the cut surface, whereby a chip-shaped green body 23 in which surface electrodes do not appear on both side surfaces is obtained. The chip-shaped green body 23 is treated in the same manner as the method shown in FIG. Since the surface electrodes do not appear on both side surfaces, there is less risk of polishing the resistance value adjusting surface electrode during the barrel polishing process, and there is an advantage that variations in the resistance value of the thermistor are further reduced.

(H) Preparation of Chip Type Thermistor with Surface Electrode for Resistance Value Adjustment of Another Embodiment (Part 3) As shown in FIGS. 17 and 18, in this method, the above-mentioned first conductive material is formed on the upper surface of the green sheet 21. After forming a large number of resistance value adjusting surface electrodes 11 by printing and drying the conductive paste in a cross-shaped spot shape, a first conductive paste is formed on the lower surface of the sheet corresponding to the intermediate position of the plurality of surface electrodes 11 on the upper surface of the sheet. Is printed and dried in the shape of a cross in the same manner as the upper surface to form a large number of resistance value adjusting surface electrodes 11. After forming the surface electrodes 11 on both sides of the sheet, the chip-shaped green body 23 is obtained in the same manner as in (g) above. By processing the chip-shaped green body 23 in the same manner as in the method shown in FIG. 4, the chip-type thermistor 50 shown in FIG. 16 is obtained. 16, the same reference numerals as those in FIG. 2 indicate the same components. Since the surface electrode does not appear on both sides and the surface electrode 11 has a convex shape, the risk of polishing the resistance adjusting surface electrode during barrel polishing is reduced, and the variation in the resistance value of the thermistor is further reduced. . Furthermore, due to the convex shape, when a current is applied to the thermistor element, the electric current concentrates on the tip of the convex part, making it difficult for the thermistor element surface to flow, and the reliability when left in a high temperature environment is reduced. improves.

(I) Preparation of Chip Type Thermistor with Surface Electrode for Resistance Value Adjustment of Another Form (Part 4) As shown in FIGS. 20 and 21, in this method, the above-mentioned first conductive material is formed on the upper surface of the green sheet 21. After forming a large number of surface electrodes 41 by printing and drying the conductive paste in a strip shape,
From the positions of the plurality of surface electrodes 41 on the upper surface of the sheet, the surface electrode 4
The first conductive paste is printed on the lower surface of the sheet in the shape of a strip in the same manner as the upper surface by shifting in the width direction of 1 to dry a large number of surface electrodes 4
1 is formed. The surface electrodes 41 on both sides of the sheet are formed so as to slightly overlap each other. After forming the surface electrodes 41 on both sides of the sheet, the green sheet 21 is formed along the broken line which is the center line of the portion where the surface electrodes overlap at the location of arrow M.
Is further cut along the broken line at a position indicated by an arrow N in a direction orthogonal to the cut surface, whereby both surfaces of the green body other than the opposite end surfaces of the chip-shaped green body 23 other than the opposite end surfaces thereof facing each other are cut. The resistance adjusting surface electrode 11 is provided on one end edge, and the outer envelope electrode locking surface electrode 17 is provided on the other end edge.
Are formed one by one. The pair of front surface electrodes 11 are formed on the edges of the surface of the green body adjacent to the opposite end surfaces of the green body. The pair of surface electrodes 17 are also formed in the same manner. The surface electrode 17 is formed in an area covered by the outer electrode 16. By processing the chip-shaped green body 23 in the same manner as in the method shown in FIG. 4, the chip-type thermistor 60 shown in FIG. 19 is obtained. 19, the same reference numerals as those in FIG. 2 indicate the same components. In the thermistor 60, the outer envelope electrode 16 is locked to the surface electrode 17 fixed to the thermistor body 10, so that the adhesive strength of the outer envelope electrode is increased.

[0023]

The resistance value of the chip type thermistor having the pair of resistance value adjusting surface electrodes 11 is mainly determined by the distance between the both terminal electrodes 12 or the resistance value adjusting surface electrode 11 electrically connected thereto. Since the areas of the surface electrodes 11 in contact with the thermistor element body 10 are printed with high precision and small variation, the variation in resistance value of the thermistor can also be reduced. In the present invention, the process of cutting the sintered sheet into chips into the chip body is performed in the state of the green sheet, so that the chip body can be easily and accurately processed.

As shown in FIG. 6, the second conductive paste 25
When the thermistor body 10 coated with is baked at a temperature lower than the melting point or the softening point of the inorganic layer 14, the envelope electrode 16 is formed as shown in FIG. That is, during this firing, the inorganic binder 25a uniformly dispersed in the paste 25 reacts with a part of the inorganic material layer 14 in the base portion of the paste to melt it. The fluidized inorganic material of the layer 14 penetrates into the pores in the outer envelope electrode 16 formed when the metal is sintered. Since the thickness of the inorganic layer 14 is set to 0.1 to 10 μm,
A part of the inorganic layer 14 is completely absorbed in the pores during the firing process and disappears from the end of the thermistor body. As a result, the envelope electrode 16 and the thermistor body 10 are separated from each other by the inorganic layer 14
Are directly adhered to each other through the disappeared portion of each of them and are electrically connected to each other. When the inclusion electrode 15 is interposed between the thermistor element body 10 and the inorganic layer 14 as shown in FIG. 9, the inclusion electrode 16 and the inclusion electrode 15 are electrically connected to each other. Since the inner electrode 15 is formed so as to maintain conductivity with the thermistor body 10, the outer electrode 16 and the thermistor body 10 are also electrically connected to each other in this case. On the other hand, in the portion of the inorganic layer 14 to which the second conductive paste 25 is not applied, even if the paste is baked, the melting point or softening point of the inorganic layer is higher than the firing temperature, so that the thermistor body 10 does not change at all. Remains on the surface of and retains its insulation protection function.

[0025]

As described above, in the prior art, a sintered sheet was cut and processed into chips, but in the present invention, the processing into chips is done in the state of a green sheet, so that it is easy to do. Moreover, it can be performed with high accuracy. In addition, since the insulating inorganic material layer is formed on the entire surface of the chip-like thermistor body at one time, the formation of the inorganic material layer is simplified, and moreover, the uniform inorganic material layer having a uniform thickness is formed on all six sides of the body. You can Further, since the resistance value adjusting surface electrode can be formed with high accuracy by printing, which is a simple thin film forming method, the resistance value of the thermistor can be adjusted precisely. For these reasons, it is possible to reduce the formation cost of the surface electrode for adjusting the resistance value and the formation cost of the inorganic layer.

In particular, according to the manufacturing method of the present invention, since the chip-shaped green body is fired to form a thermistor element body, the sintered density is high, and if the chip-shaped barrel body is subjected to barrel polishing, the corner of the chip body is cracked. It has the feature that chip-type thermistors with high mechanical strength can be manufactured without chipping. The chip-type thermistor manufactured by this method has the thermistor element body covered with an insulating inorganic material layer except for the portion where the electrodes contact, and the thermistor element body is protected by this inorganic material layer, so even if it is plated. There is no change in characteristics due to erosion of the plating solution on the body or adhesion of the plating. By forming the plating layer on the surface of the baking electrode layer, excellent effects can be obtained in solder heat resistance and solder adhesion. Further, the chip-type thermistor provided with the internal electrode has an advantage that the variation of the resistance value is further smaller and the material of the external electrode can be widely selected.

[0027]

EXAMPLES The present invention will now be described based on examples in order to show specific embodiments of the present invention. The examples described below do not limit the technical scope of the present invention. Example 1 A chip type thermistor was manufactured by the method shown in FIGS. First, commercially available manganese oxide and nickel oxide were used as starting materials, and these were used as MnO ₂ : Ni.
Each was weighed so that the metal atomic ratio was converted to O so that the metal atomic ratio became a predetermined ratio. The weighed materials were uniformly mixed with a ball mill for 16 hours and then dehydrated and dried. This mixture is then brought to 900 ° C.
It was calcined for 2 hours, and the calcined product was pulverized again with a ball mill and dehydrated and dried. To the pulverized product, 6% by weight of polyvinyl butyral, 30% by weight of ethanol and 30% by weight of butanol were added and uniformly mixed to prepare a slurry. Using this slurry, a doctor blade method was used to produce a green sheet having a thickness of 0.8 mm.
It was punched out to a size of 70 mm wide. Then, a silver / palladium alloy paste was screen-printed in a strip shape on both sides of this sheet. At this time, the strip-shaped silver pastes on both sides of the green sheet were printed so as to come to intermediate positions with the sheet sandwiched and dried to obtain resistance value adjusting surface electrodes in multiple rows having a thickness of about 20 μm.

Subsequently, the green sheet 21 is cut along the broken line which is the center line of the front surface electrode 11 at a position of an arrow M shown in FIG. 12 by using a dicing saw having a diamond blade having a thickness of 0.10 mm and has a strip shape. Green body 22
Was formed and further cut along the broken line at a position indicated by an arrow N in a direction orthogonal to the cut surface to obtain a chip-shaped green body 23. The chip-shaped green body 23 was fired at about 1200 ° C. for about 4 hours to obtain a chip-shaped thermistor element body which was a sintered body, and then barrel-polished to cut the sintered body. Barrel-polished thermistor body is about 2.0mm long,
The width was about 1.25 mm and the thickness was about 0.75 mm. An insulating inorganic material layer made of a SiO ₂ film having a thickness of 2 μm was formed on the entire surface of this thermistor element using the sputtering apparatus shown in FIG.

A silver paste was applied to the surfaces of both ends of the thermistor body covered with the SiO ₂ film by a dipping method so as to cover both ends of the thermistor body in an area smaller than the surface electrode for resistance value adjustment. The silver paste is composed of Ag powder, glass particles made of SiO ₂ , TiO ₂ , B ₂ O ₃ , Na ₂ O and K ₂ O, and an organic vehicle. After drying the thermistor body coated with the silver paste under atmospheric pressure, the temperature is raised to 820 ° C. at a rate of 30 ° C./minute, and then 1
Hold for 0 minutes, cool to room temperature at a rate of 30 ° C / minute, and
An outer envelope electrode composed of g was obtained. Next, a Ni plating layer having a thickness of 2 to 3 μm is formed on the surface of the envelope electrode by electrolytic barrel plating, and subsequently a Sn plating layer having a thickness of 1 to 2 μm is formed.
The chip type thermistor shown in FIG. 13 was obtained.

<Comparative Example 1> The thickness obtained in Example 1 was 0.
A green sheet of 8 mm, 70 mm in width and 70 mm in width is fired at about 1200 ° C. for about 4 hours to have a thickness of about 0.75 m.
m, vertical length of about 50 mm, and width of about 50 mm were obtained. Example 1 was applied to both sides of this sintered sheet in the same manner as in Example 1.
The same Ag paste as the above was screen-printed in a band shape and dried to form resistance value adjusting surface electrodes in multiple rows having a thickness of about 20 μm. A glass paste containing a raw material glass powder having SiO2, ZnO and BaO as main components and having a glass transition point of about 650 ° C and a crystallization temperature of about 750 ° C was prepared.
The glass components were uniformly mixed in the paste. This glass paste was printed on both surfaces of the sintered sheet on which the surface electrode for adjusting the resistance value was formed and dried. Sinter the dried sheet of glass paste from room temperature to 850 at a rate of about 30 ° C / min.
The temperature was raised to 0 ° C., held there for about 10 minutes, and then lowered to room temperature at a rate of about 30 ° C./min to form a glass layer having a thickness of about 30 μm on the surface of the sheet.

Next, this was cut into strips having a width of about 1.25 mm using the same diamond blade as in Example 1, and the glass paste was applied to the cut surfaces on both sides of this strip by the same method as described above. By printing and baking, a glass layer having the same structure was formed, and four surfaces of the strip-shaped body were covered with the glass layer. Subsequently, the strip-shaped body was finely cut into chips each having a length of about 2.0 mm in a direction perpendicular to the cut surface obtained by the above cutting. The same Ag paste as in Example 1 was applied to the cut surface and the glass layer around the cut surface in the same manner as in Example 1 and fired to form an envelope electrode. Further, in the same manner as in Example 1, the thickness of the envelope electrode surface was obtained. Two
~ 3μm Ni plating layer is formed, followed by a thickness of 1-2μ
An Sn plating layer of m was formed to obtain a chip type thermistor.

<Comparison Test and Results> 100 chip thermistors of each of Example 1 and Comparative Example 1 were sampled, and the dispersion of zero load resistance value at 25 ° C. and the deviation from the target resistance value were measured. Furthermore, for each chip type thermistor, the bending strength test of the following contents,
A temperature cycle test and a limit deflection test were performed. The results are shown in Table 1. The number n in parentheses is the number of samples tested. Bending strength test (n = 50) Place both ends of a sample chip thermistor in the lengthwise direction on two tables arranged at an interval of 1.2 mm. 2
A load was applied to the middle position between the two tables at a pressing speed of 20 mm / min, and the load at which the sample broke was measured. Temperature cycle test (n = 100) Solder paste (SPT55-2062, Senju Metal) with sample type thermistor on alumina substrate 0.635mm thick
Reflow soldering at a temperature of 230 ° C. Using the vapor phase temperature impact tester, the soldered sample was maintained at -25 ° C for 30 minutes, heated from there and maintained at room temperature for 3 minutes, and further heated at 85 ° C for 30 minutes. . After that, 500 cycles of a cycle test in which the maintaining time was made the same and the temperature was decreased in the opposite direction were performed, and the number of broken samples was counted. Limit deflection test (n = 20) A chip type thermistor as a sample was mounted on a glass epoxy substrate having a thickness of 1.6 mm and a width of 40 mm by reflow soldering in the same manner as above. The soldered substrate was placed on a support base having a span of 90 mm. Using a strength tester, a load was applied to the center of the span of the substrate at a pushing speed of 10 mm / min, and the limit amount of deflection when the resistance value decreased by 10% or more was measured.

[0033]

[Table 1]

As is clear from Table 1, the chip-type thermistor of Example 1 was found to adjust its resistance value to a desired value with a small variation as compared with the chip-type thermistor of Comparative Example 1. did. Further, in comparison with Comparative Example 1 in which the sintered sheet is cut into chips, Example 1 in which the chips are fired has a higher bending strength and a limit deflection amount, and it has been found that good results can be obtained even in the temperature cycle test. .

[Brief description of drawings]

FIG. 1 is a fragmentary perspective view of a chip type thermistor with a surface electrode for resistance value adjustment of the present invention.

FIG. 2 is a central longitudinal sectional view of FIG.

FIG. 3 is a perspective view of the green sheet and the green body in the steps from the thermistor element green sheet to the chip-shaped green body.

FIG. 4 is a perspective view of a chip body from the chip-shaped green body to a chip-type thermistor.

FIG. 5 is a schematic perspective view of a sputtering apparatus for forming an insulating inorganic material layer on the surface of the thermistor body.

FIG. 6 is an enlarged cross-sectional view of a main part of the thermistor element body in which a conductive paste is applied.

FIG. 7 is an enlarged cross-sectional view of an essential part in a state where the conductive paste is baked.

FIG. 8 is a fragmentary perspective view of a chip type thermistor having a resistance adjusting surface electrode and an internal electrode according to the present invention.

9 is a central vertical cross-sectional view of FIG.

FIG. 10 is a perspective view of a chip body from the chip-shaped green body to a chip-type thermistor.

FIG. 11 is a cross-sectional view of a holding plate of the thermistor element body showing a situation in which a silver paste for an internal electrode is applied to the end surface of the thermistor element body.

FIG. 12 is a perspective view of a green sheet and a green body in a process from a green sheet for a thermistor element body of a chip type thermistor with another surface electrode for resistance value adjustment to a chip-shaped green body according to the present invention.

FIG. 13 is a central vertical sectional view of the chip type thermistor.

FIG. 14 is a perspective view in which a resistance-adjusting surface electrode is formed on a thermistor element green sheet of another chip-type thermistor with a resistance-adjusting surface electrode of the present invention.

15 is a perspective view of a chip-shaped green body obtained by dicing the green sheet shown in FIG.

FIG. 16 is a central longitudinal sectional view of another chip-type thermistor with a surface electrode for resistance value adjustment of the present invention.

FIG. 17 is a perspective view in which a resistance adjusting surface electrode is formed on the thermistor element green sheet.

FIG. 18 is a perspective view of a chip-shaped green body obtained by dicing the green sheet of FIG.

FIG. 19 is a central longitudinal cross-sectional view of still another chip type thermistor with a surface electrode for resistance value adjustment of the present invention.

FIG. 20 is a perspective view in which a surface electrode is formed on the thermistor element green sheet.

21 is a perspective view of a chip-shaped green body obtained by dicing the green sheet shown in FIG.

[Explanation of symbols]

 10 Chip Thermistor Element 11 Surface Electrode for Resistance Value Adjustment 12 Terminal Electrode 14 Insulating Inorganic Material Layer 15 Internal Electrode 16 External Electrode 17 External Electrode Locking Surface Electrode 18 Ni Plating Layer 19 Sn Plating Layer 20, 30, 40, 50 , 60 Chip type thermistor 21 Green sheet for thermistor body 22 Strip green body 23 Chip green body 25 Conductive paste 25a Inorganic binder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinori Fujimoto, 2270 Yokoze, Chichibu-gun, Saitama Prefecture, Yokose, Sanritsu Materials Co., Ltd. Sanryo Materials Co., Ltd. Ceramics Laboratory

Claims (7)

[Claims] 1. A chip-like thermistor element body (10), a resistance value adjusting surface electrode (11) formed on the end surface of the element body other than opposite end surfaces of the thermistor element body (10), An insulating inorganic material layer (14) covering the entire surface of the thermistor element body (10) on which the surface electrode (11) is formed, and formed on both ends of the thermistor element body (10) covered with the inorganic material layer (14) Outer envelope electrode (1
6) and the plating layer (1
8, 19) is a chip-type thermistor, wherein the outer electrode (16) is a conductive paste containing a metal powder and an inorganic binder in a smaller area than the surface electrode (11) the thermistor body (10). ) Is formed by coating and baking so that both ends of the inorganic substance layer (14) have a thickness of 0.1 to 10 μm,
It has a melting point or a softening point higher than the firing temperature when forming the envelope electrode (16), and a part of the inorganic layer (14) of the base portion of the paste is formed at the time of forming the envelope electrode (16). A chip type thermistor, characterized in that the chip type thermistor is configured to react with an inorganic binder to be melted and absorbed by the outer envelope electrode (16) to disappear. 2. An internal electrode electrically connected to a resistance adjusting surface electrode (11) on both end faces of a chip-like thermistor element body (10).
(15) is formed, and the entire surface of the thermistor element body (10) on which the surface electrode (11) and the inclusion electrode (15) are formed is an insulating inorganic material layer.
The chip type thermistor according to claim 1, which is covered with (14). 3. A pair of resistance-value-adjusting surface electrodes (11), which are adjacent to both end surfaces of the opposing element bodies other than the opposite end surfaces of the chip-like thermistor element body (10). The chip type thermistor according to claim 1 or 2, which is formed separately. 4. The resistance-adjusting surface electrode (11) is provided on each of different edges of the chip-like thermistor element body (10) adjacent to the opposite end surfaces of the element body except the opposite end surfaces thereof. The chip type thermistor according to claim 1, wherein the chip thermistor is formed one by one. 5. A different edge adjacent to both end surfaces of the chip-like thermistor element body (10) on which the resistance value adjusting surface electrodes (11) are not formed on both surfaces of the element body opposite to each other except the opposite end surfaces. 5. The chip type thermistor according to claim 4, wherein each of the surface electrodes (17) for locking the outer package electrode is formed on the outer surface of the outer electrode (16). 6. A step of forming a resistance value adjusting surface electrode (11) by printing a plurality of strip-shaped or spot-shaped first conductive pastes on both surfaces of a thermistor element green sheet (21); A step of cutting the green sheet (21) on which the electrodes (11) are formed into chips so that the surface electrodes (11) are located at both edges, and the chip-shaped green body (23) is baked to form chips. A step of forming the thermistor element body (10);
A step of coating an insulating inorganic layer (14) having a thickness of 10 μm, and a chip-like thermistor element body (1) coated with the inorganic layer (14)
The second conductive paste (25) containing the metal powder and the inorganic binder (25a) is wrapped around the both ends of the thermistor body (10) in an area smaller than that of the surface electrode (11). And a step of applying the paste (25) to the thermistor element body (10) is baked at a temperature lower than the melting point or softening point of the inorganic layer (14),
A part of the inorganic material layer (14) disappears by reacting and melting a part of the inorganic material layer (14) of the underlying portion of the paste in the inorganic binder (25a) of the applied paste, and the external electrode (16) ) And a step of forming the plating layers (18, 19) on the surface of the envelope electrode (16). 7. The third conductive material is provided on both end surfaces of the chip-like thermistor element body (10) between the step of forming the chip-like thermistor element body (10) and the step of coating the insulating inorganic material layer (14). Surface electrode for resistance adjustment by applying paste and baking
The method for manufacturing a chip type thermistor according to claim 6, further comprising the step of forming an internal electrode (15) electrically connected to (11).