JPH043444Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The invention is aimed at eliminating sparks in micro motors,
This invention relates to a porcelain varistor for use in noise prevention, etc.

[Prior Art] A commutator is connected to a ring-shaped varistor coaxially arranged on the shaft of a micromotor by soldering terminals connected to the commutator to electrodes of the varistor. There is. During this soldering, if the heat of the soldering iron is suddenly applied to the varistor, the varistor will crack due to thermal stress, so generally the varistor is preheated to reduce the temperature difference between the varistor and the soldering iron. It was made smaller and suppressed the occurrence of cracks.

[Problems to be solved by the invention] However, preheating inevitably complicates the soldering process, and preheating also causes deterioration of resin parts other than the varistor. In order to prevent this deterioration, if the preheating temperature is kept between 80℃ and 150℃,
It becomes impossible to suppress the difference between the preheating temperature and the soldering temperature of 250°C to 340°C to 150°C or less, which is effective for preventing cracks.

Therefore, an object of the present invention is to provide a porcelain varistor with good heat resistance that can be soldered without preheating.

[Means for Solving the Problems] The present invention for achieving the above object includes a first electrode layer, a buffer intermediate layer, and a second electrode layer provided in this order on the main surface of a varistor ceramic body. , the second electrode layer is made of a material with good solder adhesion and is electrically connected to the first electrode layer.

[Function] The second electrode layer of the above invention is used as a soldering part for connecting a varistor. This second
Even if a soldering iron or the like comes into contact with the electrode layer of the varistor and heats it, the buffering intermediate layer is provided, so that no large thermal stress is applied to the varistor porcelain body.

[First Embodiment] Next, a ring-shaped varistor according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

First, a ring-shaped varistor porcelain body 1 containing strontium titanate as a main component was produced. The outer diameter of this porcelain body 1 is 10.7 mm, the inner diameter is 6.8 mm, and the thickness is
It is 0.90mm.

Next, silver electrode paste was printed on one main surface of the porcelain body 1 in the pattern shown in FIG. 1A, dried, and then baked at 650°C for 30 minutes. Electrode layers 2, 3, and 4 were formed.

Next, a glass paste consisting of PbO-B2O3-SiO2 is applied to the first electrode layer 2, as shown in FIG. 1B.
3 and 4, and after drying, a baking process was performed at 650° C. for 30 minutes to form a buffering intermediate layer 5 made of a glass layer. In this intermediate layer 5, holes 6 for exposing the first electrode layers 2, 3, 4 were provided at a ratio of two holes for each electrode layer 2, 3, 4.

Next, a silver paste is printed on the intermediate layer 5 in the same pattern as the first electrode layers 2, 3, and 4 as shown in FIG. treated to form three second electrode layers 7,
8 and 9 were formed. The second electrode layers 7, 8, 9 on the intermediate layer 5 consisting of a glass layer are electrically connected to the first electrode layers 2, 3, 4 via holes 6 in the intermediate layer 5.

The thickness of the first and second electrode layers 2 to 4 and 7 to 9 is 6 μm, respectively, and the thickness of the intermediate layer 5 is
It is 25μm.

When this ring-shaped varistor is used in a micromotor or the like, the connecting member 10 is connected to the second electrode layers 7 to 9 by solder 11, as shown by broken lines in FIG.

In order to evaluate the completed ring-shaped varistor,
Apply flux-containing eutectic solder on the second electrode layer 7 with a soldering iron at 280°C, and after forming a solder adhesion layer with a soldering iron contact time of 2 to 3 seconds, use a magnifying glass to The occurrence of cracks in porcelain body 1 was reduced to 50
The following samples were investigated. However, it was not possible to confirm the crack. In other words, the incidence of cracks was zero. Next, set the temperature of the soldering iron to 310℃.
A similar test was conducted with the temperature changed to 340°C, but the crack occurrence rate was still zero. For comparison, a ring-shaped varistor was prepared in which the intermediate layer 5 made of a glass layer was omitted and the first and second electrode layers 2 to 4 and 7 to 9 were provided, and a similar test was conducted.
At a soldering iron temperature of 280°C, the crack occurrence rate was zero, but at 310°C it was 2%, and at 340°C it was 10%.

From the above, it is clear that the intermediate layer 5 contributes to preventing the occurrence of cracks. This crack can be suppressed by the fact that the thermal conductor is restricted by the intermediate layer 5, and that the porcelain body has a single linear expansion coefficient of 13.0.
This is related to the fact that the linear expansion coefficient of the intermediate layer 5 made of a glass layer is 8.1 x 10-6/°C, which is much smaller than that of 8.1 x 10-6/°C. That is, the intermediate layer 5 is sufficiently thicker than the first and second electrode layers 2 to 4 and 7 to 9, with a thickness of 25 μm, and is a non-metallic glass layer, so that rapid heating of the porcelain body 1 is prevented. do.
Further, since the intermediate layer 5 has a small coefficient of thermal expansion, this thermal expansion does not apply large stress to the ceramic body 1.

The material of the intermediate layer 5 is PbO-ZnO with a linear expansion coefficient of 6.8.
When the same test as in the first example was carried out using -B2O3-SiO2 glass, the same effects were obtained. In addition, the intermediate layer 5 is made of PbO− with a linear expansion coefficient of 5.5.
When the same test as in the first example was conducted using CaO-B2O3-SiO2 glass, the same effects were obtained.

[Second Embodiment] Next, a ring-shaped varistor according to a second embodiment shown in FIGS. 3 and 4 will be described. However, the third
4, and also in FIGS. 5 to 16 showing the third to eighth embodiments, parts that are substantially the same as those in FIGS. 1 to 2 are denoted by the same reference numerals. The explanation will be omitted.

The ring-shaped varistor shown in FIGS. 3 and 4 has an insulating layer 12 covering holes 6 for electrically connecting first electrode layers 2 to 4 and second electrode layers 7 to 9. There is. Therefore, solder is prevented from flowing into the holes 6, and the occurrence of cracks in the ceramic body 1 is further suppressed.

[Third Example] In FIGS. 5A to 5C and FIG. 6 showing the third example, the first electrode layers 2 to 4 and the second electrode layer 7
The connection method with ~9 has been changed. That is, the fifth
After forming the first electrode layers 2 to 4 as shown in FIG. A, the intermediate layer 5 is formed as shown in FIG. 5B so as to expose both ends thereof. Next, Figure 5C
The second electrode layers 7 to 9 are formed in the same pattern as the first electrode layers 2 to 4 as shown in FIG. This results in
The first electrode layers 2-4 and the second electrode layers 7-9 are connected to each other at both ends.

[Fourth Example] In the fourth example shown in FIGS. 7 and 8, an insulating layer 13 is provided between the second electrode layers 7 to 9 in the third example. The inflow of solder is prevented.

[Fifth Example] In the fifth example shown in FIGS. 9A to 9C and FIG. 10, only one end of the first electrode layers 2 to 4 is exposed from the intermediate layer 5, and this is It is connected to the second electrode layers 7-9.

[Sixth Example] In the sixth example shown in FIGS. 11 and 12, the first electrode layers 2 to 4 and the second electrode layers 7 to 4 are formed in the same manner as in the fifth example. An insulating layer 14 for preventing solder flow is provided on the connection portion with 9.

[Seventh Example] In the seventh example shown in FIGS. 13A to 13C and FIG. 14, the intermediate layer 5 is formed so as to expose both ends of the first electrode layers 2 to 4. . Moreover, this intermediate layer 5 is also formed between the first electrode layers 2 to 4. The second electrode layers 7 to 9 are the first electrode layer 2
-4 are formed in the same pattern, and both ends are connected to the first electrode layers 2-4.

[Eighth Example] In the eighth example shown in FIGS. 15A to 15C and FIG. 16, the first electrode layers 2 to 4 and the intermediate layer 5 are
The structure is the same as that of the embodiment. The difference from the third embodiment is that the second electrode layers 7 to 9 are provided with narrow portions 15 for preventing solder flow. This narrow portion 15 is connected to the second electrode layers 7 to 9.
are provided near both ends of the second
When a connecting member is soldered to the center of the second electrode layers 7 to 9, the solder flowing between the second electrode layers 7 to 9 is blocked by the narrow portion 15.

[Modifications] The present invention is not limited to the above-described embodiments, but can be modified as follows, for example.

(1) The glass layer of the intermediate layer 5 is made of PbO, B2O3, SiO2,
The glass layer preferably contains two or more selected from ZnO, BaO, CaO, and Na20.

(2) Instead of a glass layer, an epoxy resin layer, a phenol resin layer, a silicone resin layer, or the like can be provided as the intermediate layer 5. Further, depending on the case, the intermediate layer 5 may be a conductive layer.

[Effects of the Invention] As described above, according to the present invention, a porcelain varistor with good heat resistance characteristics can be provided.

[Brief explanation of drawings]

Figures 1A, B, and C are plan views showing the varistor of the first embodiment in the order of the manufacturing process, Figure 2 is a cross-sectional view taken along the - line in Figure 1C, and Figure 3 is the varistor of the second embodiment. FIG. 4 is a cross-sectional view taken along the line -- in FIG. 3, FIG. 7 is a plan view showing the varistor of the fourth embodiment, FIG. 8 is a sectional view taken along the line - of FIG. 7, and FIGS. 9A, B, and C are the varistors of the fifth embodiment. A plan view showing the order of the manufacturing process, Figure 10 is Figure 9C
11 is a plan view showing the varistor of the sixth embodiment, FIG. 12 is a sectional view taken along the - line of FIG. 11, and FIGS. 14 is a plan view showing the varistor in the order of manufacturing steps, FIG. 14 is a cross-sectional view taken along the - line in FIG. Figure 15C-
FIG. 1... Ballista porcelain body, 2, 3, 4... 1st
5... middle layer, 7, 8, 9... second electrode layer.

Claims (1)

[Scope of utility model registration request] A first electrode layer, a buffer intermediate layer, and a second electrode layer are sequentially provided on the main surface of the varistor ceramic body, and the second electrode layer is made of a material with good solder adhesion. A porcelain varistor, characterized in that it is electrically connected to the first electrode layer.