JPS58141506A - Chip type thermistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a chip-type thermistor that can be directly mounted on a printed circuit board or the like.

(1) Prior Art and Problems Chip-type capacitors are used in hybrid integrated circuits, and chip-type thermistors are also used for thermistors for temperature compensation in various circuits. For example, as shown in FIG. 1, thick film electrodes 2 are formed on both sides of a thermistor element l, and
and wiring 4 on the printed circuit board 3 are connected by solder 5 or the like, and a top view of such a chip-type thermistor is shown in FIG.

Such conventional chip-type thermistors are produced by wrapping a thermistor body plate to a predetermined thickness, cutting it to a predetermined size using a diamond cutter, etc., and attaching a thick film electrode made of a conductive material such as AgPd by dipping or scraping.・It is formed by printing or the like.

Therefore, from a manufacturing point of view, it is easy to manufacture and inexpensive because there is no need to connect lead wires or the like.

However, from the viewpoint of use and characteristics, it has the following drawbacks.

In other words, the shape of a chip-type mistor is determined by the spacing between the wiring on the printed circuit board, etc., but the resistance value of the thermistor is determined by the specific resistance and cross-sectional area of the thermistor body, and the length between the electrodes. Therefore, it is actually not easy to manufacture a thermistor with a desired resistance value. In addition, since solder acts to absorb Ag in the thick film electrode, the A, G in the thick film electrode can be absorbed into the solder for connecting to the wiring.
diffuses, increasing the resistance of the thick film electrode and the resistance between it and the thermistor body. This changes the resistance of the thermistor. In addition, since the thermistor element is a sintered body of metal oxide, it is affected by the working temperature and atmosphere during assembly, and depending on the type of atmosphere, the amount of oxygen atoms may change due to heating, resulting in a change in the resistance value of the thermistor. . Furthermore, the change over time is relatively large. This can be reduced over time by aging after assembly, but after being mounted on a printed circuit board,
It is impossible to carry out aging due to the effect it has on other electronic components, and in practice it has not been possible to reduce changes over time.

la) Object of the Invention It is an object of the present invention to provide a chip-type thermistor that is easy to manufacture and provides stable characteristics by eliminating the conventional drawbacks as described above. Examples will be described in detail below.

Embodiment of the Invention Figures 3 to 6 show examples of thermistor elements that can be used in the present invention, 1a to 1d are thermistor bodies, 28 to 2d are lead wires, and 3c and 3d are electrodes. be. The thermistor element shown in FIGS. 3 and 4 has a lead wire 2a
, 2b, the raw materials for the thermistor bodies ta, tb are slurried and made into granules, which are dried and fired, and are called bead type. Also, depending on the shape of the lead wire, the one shown in FIG. 3 is called a single-cut type, and the one shown in FIG. 4 is called a double-cut type.

The thermistor elements shown in FIGS. 5 and 6 are of a so-called bullet type, and each figure (a) is a side view and (b) is a top view. Such a bullet-type thermistor element is produced by wrapping a sintered thermistor material to a desired thickness determined based on specific resistance, applying conductive paste etc. to both sides, and firing it to achieve the resistance required for the thermistor element. The lead wires 2CI2d are cut to a size with a diamond cutter or the like, and the lead wires 2CI2d are connected to the electrodes 3c and 3d by welding or applying a conductive paste and baking.

In addition, depending on the connection shape of the lead wire, Figure 5 shows the type for cleaning, and the type for cleaning in Figure 6.
In the figure, both elbows are called kata.

Figure 7 shows an embodiment of the present invention, in which (al is a sectional view, (b) is a bottom view, and (C) is a side view. This is for the case where a thermistor element is used. In Fig. 7, 11 is the thermistor element, 12 is the lead wire, and 13 is the electrical filling material. Lead wires are connected to the electrodes on both sides of the thermistor element 11. 12 are connected by welding, baking conductive paste, etc., and the ceramic case 14 has thick film electrodes 15 formed on both sides, a hole through which the lead wire 12 is inserted at the bottom, and a hole around this hole and the thick film electrode. The thermistor element 11 is housed in the ceramic case 14, the thermistor element 11 is sealed with a glass filler 18, and the lead wire 12 is connected to the lead wire 12.
and the electrode pattern 16 (by baking a conductive paste 17).

Thermistor element 11. Lead wire, ceramic case 14
．． Glass filler18. The conductive bases 16 and 16 are made of materials having approximately the same coefficient of thermal expansion, and the ceramic case 14 is made of a glass filler 18.
It is made of a material that does not undergo crystal transformation below the melting temperature.

In the manufacturing process of the chip-type thermistor having the above-described configuration, first, as explained with reference to FIG. 5, the lead wire 12 is connected to the electrode 13 of the thermistor body 11,
thick film electrodes 15 and electrode patterns 16 on both sides and bottom of the
is formed, and the lead wire 12 is connected to the ceramic case 1.
4, and bond the lead wire 12 and the electrode pattern 16 with conductive paste 17. This conductive paste 17 is made of metal powder such as Ag, Au, Pd, lead #
It is a mixture of glass powder that has a coefficient of thermal expansion almost equal to that of the ceramic case 14, an organic substance that has an appropriate viscosity at room temperature and has an adhesive effect when dried, and a diluent such as thinner. The lead wire 12 is bonded to the electrode pattern 16, and the organic matter is evaporated by high temperature heating, and the metal powders are bonded together by melting the glass powder, thereby connecting the lead wire 12 and the electrode pattern 16.

The above-mentioned high-temperature heating utilizes the heating during melt filling of the glass filler 18, and the thermistor body 11 is housed in the ceramic case 14, and the lead wire 12 is bonded to the electrode pattern 16 with a conductive paste 17. After that, the glass filler powder is filled into the ceramic case 14 and heated and melted using an electric furnace or the like.

The conductive paste 17 is baked by the heating.

After the thermistor body 11 is sealed in a ceramic case 14 with a glass filler 18, it is aged, and after resistance value measurement and selection, the lead wire 12 is cut so that the protruding length thereof is the minimum required length. Ru.

As the chip-type thermistor described above, a single-cut bead-type thermistor element as shown in FIG. 3 can also be used.

FIG. 8 shows another embodiment of the present invention, in which a double bead-type thermistor element as shown in FIG. 4 or a pellet-type thermistor element as shown in FIG. 6 is used. (a) is a schematic longitudinal sectional view, (b)
) is a cross-sectional view, and (C) is a side view of the ceramic case. In FIG. 8, 21 is the thermistor body, 22 is a lead wire, 23 is an electrode, 24 is a ceramic case, 25 is a thick film electrode, 26 is a groove for inserting a lead wire, 27 is a conductive paste, and 28 is a It is a glass filling material. The difference from the above embodiment is that a groove 26 is formed in the side surface of the ceramic case 24 depending on the shape of the lead wire connected to the thermistor body, so that the thermistor body can be housed in the ceramic case 24 from above. This is the point where the lead @22 is placed in the groove 26.
The thick film electrode 25 and the lead wire 22 are connected (7) by inserting and adhering them with a conductive paste 27, and baking the conductive base 27 by heating when the glass filler row is melted. It is something.

As described in detail, according to the present invention, the thermistor body is housed in a ceramic case and sealed with a glass filler, so even if heated in any atmosphere, the temperature will not exceed the aging temperature. If so, the temperature measurement characteristics will not be affected, and even if the thick film electrode and the wiring of the printed circuit board are connected by solder, even if Ag oozes out from the thick film electrode, it will not work as a thermistor. There will be no change in resistance value at all. It can be mounted on a printed circuit board in the same way as chip-type electrical components, and its characteristics are not affected by various conditions during assembly. Further, the change over time is extremely small, and it can be operated stably for a long time as a temperature compensating element, for example. This change over time is 0.5% at 300 C.
I was able to do it in less than an hour.

Furthermore, when thermal shock was applied by alternately immersing the material in 200C and 25C oil baths for a transfer time of 0.5 seconds, the coefficients of thermal expansion were almost the same, so (8) cracks were not generated. There was no change in characteristics for 100 cycles of repetition. It was less than s%. Therefore, it can be incorporated as a temperature compensating element into circuits that require high stability.

[Brief explanation of the drawing]

FIGS. 1 and 2 are sectional views and top views for explaining a conventional chip-type thermistor, and FIGS. 3 to 6 show an example of the thermistor element that can be used in an embodiment of the present invention.
, Figures 3 and 4 are cross-sectional views, Figures 5 (a) and 6 (al are side views, Figures 5 (b) and 6 (b) are top views, Figures 7 and 8 are The figures show different embodiments of the present invention, and FIGS. 7(a) and 8(a) are longitudinal sectional views, FIG. 7(bl is a bottom view, FIG. 7(C) is a side view, Figure 8 (
bl is a cross-sectional view, and FIG. 8(C) is a side view of the ceramic case. 1a-1d, 11, 21 are thermistor bodies, 2
a to 2d 112 , 22 is a lead wire, 3c, 3d,
13+23 is the electrode, 14.24 is the ceramic case, 1
5.25 is a thick film electrode, 16 is an electrode pattern, 17, 2
7 is a conductive paste, and 18 and 28 are glass fillers. Figure 5 Figure 6 (a) Figure 7 Figure 8

Claims (1)

[Claims] A thermistor element body having lead wires having substantially equal coefficients of thermal expansion, having a chip-shaped external shape, having a thick film electrode formed on the outer surface, a recess for accommodating the thermistor element body, and leading out the lead wire from the recess. a ceramic case having a thermal expansion coefficient substantially equal to that of the thermistor body;
Insert the lead wire into the hole of the ceramic case.
C. A chip-type thermistor, characterized in that the four parts contain the thermistor element, a glass filler seals the thermistor element, and the lead wire is connected to the thick film electrode.