JPH04127601U - Chip type positive temperature coefficient thermistor - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the thermal response of a chip-type positive temperature coefficient thermistor and to improve its adaptability to high-density packaging. [Structure] The thermistor element 1 is formed into an upwardly tapered shape in which the surface area of the upper main surface 1a is smaller than the surface area of the lower main surface 1b, thereby reducing its volume and surface area.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention relates to a chip type positive temperature coefficient thermistor. The present invention also relates to a chip-type positive temperature coefficient thermistor that can be mounted at high density.

0002

[Conventional technology]

As a conventional chip type positive temperature coefficient thermistor, for example, a chip as shown in Fig. 9 is used. There is a positive temperature coefficient thermistor. This chip type positive temperature coefficient thermistor 50 is a thin rectangular A pair of electrodes 70, 70 are provided at both ends of a thermistor element body 60 having positive body shape characteristics. It has an arranged structure. The pair of electrodes 70 and 70 each have a thermium Main surface electrodes 70a, 70a formed on the main surface, side surfaces, and end surfaces of the star body 60, and the side surfaces It is composed of electrodes 70b, 70b and an end electrode 70c, and the back side is also the same as in FIG. It has the same structure.

0003 Such a chip-type positive temperature coefficient thermistor 50 has a large positive temperature coefficient of resistance. When the Curie temperature is exceeded, the resistance value increases rapidly, reducing the amount of current passing through it. It is widely used for various purposes such as circuit overheat protection and overcurrent protection. However, in recent years, in order to improve reliability, products with better thermal response than before have been developed. chip-type positive temperature coefficient thermistors are now required, and the equipment is becoming smaller and smaller. With the trend toward new types, the requirements for chip-type positive temperature coefficient thermistors that can be applied to high-density surface-mount circuits have increased. demand is increasing.

0004

[Problem that the idea aims to solve]

However, in the conventional chip type positive temperature coefficient thermistor 50, the thermistor element Since the volume and surface area of the body 60 are large, the chip type positive temperature coefficient thermistor has a large heat capacity. As the temperature increases, the amount of heat dissipated from the surface also increases, ensuring sufficient thermal response. There is a problem that it is not possible to do so and has low reliability.

[0005] Furthermore, in the conventional chip type positive temperature coefficient thermistor 50, as shown in FIG. For example, the chip type positive temperature coefficient thermistor 50 is disposed on the substrate 81, and the electrode 70 When connecting by soldering to the land 82, the side electrode is connected from the upper main surface electrode 70a. Solder 83 adheres to the pole 70b and end electrode 70c, and a large amount of molten solder 83 accumulates in the soldering area. As a result, based on the chip type positive temperature coefficient thermistor 50, When mounting on the board 81 with high density, the melt adhering to the upper main surface electrode 70a etc. The solder 83 flows toward the adjacent chip type positive temperature coefficient thermistor 50, shortening the circuit. There is a problem in that high-density packaging is hindered because of the interconnection.

[0006] This invention solves the above problems and is said to have excellent thermal response. Our aim is to provide chip-type positive temperature coefficient thermistors suitable for high-density packaging. Ru.

[0007]

[Means to solve the problem]

In order to achieve the above purpose, the chip-type positive temperature coefficient thermistor of this invention In a chip-type positive temperature coefficient thermistor that has a pair of electrodes on both ends of a star element, , the thermistor element is placed in a top-bottom configuration in which the surface area of the upper principal surface is smaller than the surface area of the lower principal surface. It is characterized by being formed in the shape of a ball.

[0008]

[Effect]

The chip-type positive temperature coefficient thermistor of this invention has a thermistor body that tapers upward. Because the upper side is narrowed, the upper side is not completely closed like the conventional one. The volume and surface area of the thermistor element is smaller than that of a non-concave thermistor element, making it suitable for chip-type positive CharacteristicsAs the heat capacity of the thermistor as a whole decreases, the amount of heat dissipated decreases, causing heat loss. Improves responsiveness. In addition, the chip type positive temperature coefficient thermistor of this invention has a tapered top. , and at least one of the end faces or sides is not vertical but somewhat Because it has a slope of This prevents molten solder from flowing into electronic components and lines, allowing for high-density surface mounting. It becomes possible to do this.

[0009]

【Example】

Hereinafter, an embodiment of this invention will be described based on the drawings. Figure 1 shows one implementation of this idea. 2 is a perspective view showing a chip-type positive temperature coefficient thermistor according to an example, and FIGS. 2 and 3 are They are a sectional view and a plan view. As shown in these figures, this chip type positive temperature coefficient thermistor In star A, the thermistor body 1 having positive characteristics is as shown in FIGS. 1 and 2. , the top tapers, the cross-sectional shape is trapezoidal (so-called trapezoidal shape), and The area of the surface (upper main surface) 1a is smaller than the area of the lower surface (lower main surface) 1b. . Electrodes 2, 2 are formed on both ends of the thermistor body 1. The electrodes 2, 2 extend from the end surface 1c having an inclination (θ) to the upper surface 1a side and the lower surface 1b side. It goes around to Note that these electrodes 2, 2 are ohmic electrodes, although not particularly shown. An upper layer electrode (not shown) with excellent solderability is placed on top of a lower layer electrode (not shown) with excellent solderability. ). The dimensions of each part of the chip type positive temperature coefficient thermistor A are, for example, W=1.5. mm, L=3.0mm, L'=2.0mm, T=0.6mm, G=1.0mm, θ=50° It consists of:

0010 The chip type positive temperature coefficient thermistor A configured in this way has the thermistor body 1 on top. It is formed in a tapered shape, and the upper part is narrower than the conventional model. The volume and surface area are smaller than the thermistor element 50 (FIG. 9) whose sides are not narrowed. Therefore, the heat capacity of the PTC thermistor A as a whole becomes smaller, and the amount of heat dissipated becomes smaller. decreases and improves thermal responsiveness.

[0011] Figure 4 shows the chip type characteristic of the above example when the ambient temperature (atmosphere temperature) is changed. It is a diagram showing the state of temperature change of the thermistor A, and the elapsed time on the horizontal axis is 0 seconds. This indicates that the ambient temperature has increased since then. From FIG. 4, the positive characteristics of the above example Thermistor A (its temperature) quickly follows changes in ambient temperature, and is It can be seen that the thermal response is significantly improved compared to the characteristic thermistor.

0012 Moreover, FIG. 5 shows the surface mounting of the chip-type positive temperature coefficient thermistor of the above embodiment on a circuit board. Indicates the state of the case. The chip type positive temperature coefficient thermistor A of this example has an upper It has a round shape, and the end surface 1c is not vertical but has an inclination (θ). Therefore, the electrode 2 has a large ability to hold molten solder. Therefore, as shown in Figure 5, The melted solder 3 is applied from the land 5 on the substrate 4 to the adjacent chip type positive temperature coefficient thermistor B. This makes it possible to reliably prevent short circuits caused by flowing toward the opposite direction. Surface mounting can be performed.

[0013] In the above embodiment, the thermistor element 1 having a trapezoidal cross-sectional shape is used. When electrodes are formed from the end surface 1c having an inclination of , to the upper surface 1a and the lower surface 1b However, the shape of the thermistor body 1 and the shape of the electrode 2 are the same as in the above embodiment. Thermistor elements of various shapes, such as but not limited to those shown in FIGS. 6 to 8, can be used. Chip-type positive temperature coefficient thermistors C, D, and E in which electrodes 2 are formed on both ends using a body 1. All of these are included within the scope of this invention. In other words, the chip type positive The characteristic thermistor C has an upper bottom end face 1c that is vertical but a side face 1d that is inclined. A ball-shaped thermistor element 1 is used, and no electrode is formed on the vertical end surface 1c. , electrodes 2 are formed on the upper and lower surfaces 1a, 1b and the side surface 1d. Also, the chip in Figure 7 The double-type positive temperature coefficient thermistor D has an upper end face 1c and a side face 1d both having an inclination. A thermistor body 1 having a hollow shape is used, and its end face 1c, side face 1d, and bottom face 1b are An electrode 2 is formed on the surface. Furthermore, the chip type positive temperature coefficient thermistor E in FIG. A thermistor body 1 having a concave curved shape and tapering at the top is used, and its end Electrodes 2 are formed on the surface 1c and the lower surface 1b.

[0014] The chip-type positive temperature coefficient thermistors C, D, and E shown in FIGS. 6 to 8 are also described above. The same effect as the positive temperature coefficient thermistor A of the embodiment can be obtained.

[0015]

[Effect of the idea]

As mentioned above, the chip-type positive temperature coefficient thermistor of this invention has a thermistor body on top. Since it is formed in a convergent shape, the thermistor is only as narrow as the upper part. The volume and surface area of the element body are small, and the heat capacity of the positive temperature coefficient thermistor as a whole is small. As the temperature decreases, the amount of heat dissipated decreases and the thermal response improves.

[0016] In addition, the chip-type positive temperature coefficient thermistor of this invention has a shape that tapers upward. Therefore, at least one of the end face or side face is not vertical but has a certain degree of inclination. Therefore, the electrode has a large ability to hold molten solder, making it difficult for molten solder to flow out. , effectively prevents molten solder from flowing into adjacent electronic components, lines, etc. High-density packaging is possible.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a chip type positive temperature coefficient thermistor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of the chip type positive temperature coefficient thermistor of FIG. 1;

FIG. 3 is a plan view showing a chip type positive temperature coefficient thermistor according to an embodiment of the invention.

FIG. 4 is a diagram showing the thermal response of a chip type positive temperature coefficient thermistor according to an embodiment of the present invention.

FIG. 5 is a sectional view showing a state in which a chip type positive temperature coefficient thermistor according to an embodiment of the invention is mounted on a substrate.

FIG. 6 is a perspective view showing a chip type positive temperature coefficient thermistor according to an embodiment of the invention.

FIG. 7 is a perspective view showing a chip type positive temperature coefficient thermistor according to an embodiment of the invention.

FIG. 8 is a perspective view showing a chip type positive temperature coefficient thermistor according to an embodiment of the invention.

FIG. 9 is a perspective view showing a conventional chip type positive temperature coefficient thermistor.

FIG. 10 is a cross-sectional view showing a state in which a conventional chip type positive temperature coefficient thermistor is mounted on a substrate.

[Explanation of symbols]

A Chip type positive temperature coefficient thermistor 1 Thermistor element 1a Upper surface of thermistor element (upper main surface) 1b Lower surface of thermistor element (lower main surface) 2 electrodes

Claims (1)

[Scope of utility model registration request] 1. A chip-type positive temperature coefficient thermistor in which a pair of electrodes are provided on both ends of a thermistor element, in which the thermistor element is formed into an upper tapered part in which the surface area of the upper main surface is smaller than the surface area of the lower main surface. A chip type positive temperature coefficient thermistor characterized by being formed in the shape of.