JPS5852641Y2 - Positive characteristic thermistor - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to an improvement of a positive temperature coefficient thermistor.

As shown in FIG. 1, a conventional positive temperature coefficient thermistor is manufactured by soldering a lead wire 4 to an electrode 2 formed on the surface of a positive temperature coefficient thermistor element 1 using a flux such as acidic flux or activated rosin.
A coating 5 is applied with a resin such as epoxy or silicone as required.

Generally, when a voltage is applied to a positive temperature coefficient thermistor element, the element generates heat depending on its resistance, and the temperature rises from room temperature to about 150° C. in a few seconds to several tens of seconds.

If this happens, the resistance of the element increases rapidly by a factor of 100 to 1000, which in turn blocks the flow of current and reaches thermal equilibrium.

Taking advantage of this characteristic, it has been used in switching elements and the like.

In this case, the positive temperature coefficient thermistor element is subjected to frequent temperature cycles from room temperature to 150°C.

As shown in Figure 1, when this temperature cycle is repeated for a long time, the PTC thermistor with the conventional structure is exposed to stress because the thermal expansion coefficients of the PTC thermistor element 1, the solder 3, and the lead wire 4 are different. may get on the solder, causing cracks in the solder near the lead wires, recrystallization of the solder, or oxidation due to moisture in the air.
This results in a decrease in solder strength and adhesive strength.

As these phenomena progress, the lead wire becomes separated while immersed in the solder, and the increased resistance at that part causes overheating and destroys the element.

Therefore, in order to improve this problem, as shown in FIG. 2, a positive temperature coefficient thermistor element is constructed by providing electrodes 2 showing ohmic contact with nickel, silver, etc. on both sides of a semiconductor porcelain 1 having a positive resistance-temperature characteristic. The electrode 2 is provided with a connection plate 6 having a support protrusion 8, and a spring terminal 7 having a hole 9 that fits with the support protrusion 8 of the connection plate 6 is provided. A positive temperature coefficient thermistor that clamps the connecting plate 6 and the element with elasticity is disclosed in Japanese Utility Model Publication No. 49-15155, but it is difficult to fix the positive temperature coefficient thermistor element approximately at the center of the connecting plate 6, and the element may be damaged due to vibrations. There were many disadvantages, such as movement, and the need to cover the positive temperature coefficient thermistor element with an insulating case after it was clamped.

The present invention eliminates the above-mentioned drawbacks, and provides a positive temperature coefficient thermistor that can stably hold a positive temperature coefficient thermistor element, can be used depending on the application, and can be manufactured at low cost.

The present invention will be described below with reference to embodiments shown in FIGS. 3, 4, and 5.

FIG. 3 is a cross-sectional view of the positive temperature coefficient thermistor of the present invention, where 11 is a semiconductor porcelain having positive resistance-temperature characteristics, 12 is an electrode, and 16 is a
is a metal cap, in which electrodes 12 are provided on two opposing sides of a disk-shaped semiconductor ceramic 11 having positive resistance-temperature characteristics, and a metal cap 16 having a protrusion 18 at the center of one surface is attached in advance to the electrodes 12. The metal cap 16 is laminated or bonded and bonded to each other, and the heat-shrinkable tube 20 is placed on the metal cap 16 except for the central part, and the metal cap 16 is heat-shrinked to form the plate-shaped semiconductor porcelain 11.
This is a PTC thermistor in which a PTC thermistor element having electrode layers 12 on both sides and a metal cap are integrally formed.

Note that the heat shrink tube 20 is mainly used to fix the PTC thermistor and the metal cap 16, and the center portion of the metal cap 16 is not covered, and the more uncovered the better.

FIG. 4 shows a cross-sectional view of the terminal fixture, where 21 is a board, 1
Reference numeral 7 denotes an elastic metal terminal having a hole 19 that fits into a protrusion 18 formed at the center of the metal cap 16 shown in FIG. 3, and the positive temperature coefficient thermistor shown in FIG. will be installed on the

In the above embodiment, the terminal 17 is shown as being fixed to the board 21, but the terminal 17 may be connected and fixed in advance to a printed circuit board on which other electronic components are mounted and a positive temperature coefficient thermistor is mounted thereon. good.

Also, the metal cap may or may not have a hole, depending on the design, and the cap is not limited to metal, but may also be made of a terminal material such as an insulating material such as resin that has conductivity on its surface. .

Therefore, the PTC thermistor of the present invention does not require an outer covering using a relatively expensive heat-resistant resin like conventional products.
In addition, the movement of air is not restricted by the outer cover, and the device has a novel configuration with good heat dissipation, quick cooling after turning off electricity, and good recovery characteristics.

As described above, in this invention, the electrodes of a PTC thermistor element are brought into contact with a conductive cap having protrusions on one surface, and the cap is integrally formed with a heat-shrinkable tube, so that the cap can be moved due to vibration etc. Since there is no heat dissipation, the heat dissipation of the positive temperature coefficient thermistor is constant, and its assembly is simple and production efficient. Furthermore, it does not require an outer jacket, and has good heat dissipation, which is industrially useful.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional positive temperature coefficient thermistor with terminals connected by soldering. Fig. 3 is a sectional view of an embodiment of the PTC thermistor of the present invention, Fig. 4 is a sectional view of a terminal fixture according to the present invention, and Fig. 5 is a cross-sectional view of an embodiment of the PTC thermistor of the present invention. FIG. 11: Semiconductor porcelain having positive resistance temperature characteristics, 12: Electrode, 16: Metal cap, 17: Metal terminal, 18: Projection, 19: Fitting hole, 20: Heat shrink tube.

Claims (1)

[Scope of utility model registration request] A positive temperature coefficient thermistor formed by integrally forming a positive temperature coefficient thermistor element having electrode layers on both sides and a conductive cap having a protrusion approximately at the center of one surface using a heat shrinkable tube.