JPS61202402A - Surge absorber - 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] Industrial Application Field The present invention is used to protect semiconductor devices such as ICs (integrated circuits) from abnormally high voltages with low energy such as electrostatic discharge and pulse voltages when impacting piezoelectric elements. The present invention relates to a surge absorber.

Conventional technology In recent years, home appliances have become more and more multi-functional.

Computerization is being promoted in the fields of information communication equipment and industrial equipment. ICs and LSIs (
Although large-scale integrated circuits (large-scale integrated circuits) have excellent functionality, they are extremely sensitive to pulse-like abnormal voltages such as static electricity, which often leads to malfunction or destruction of electronic equipment. Therefore, from the viewpoint of ensuring and improving the reliability of electronic equipment, measures against surge voltages of these semiconductor elements are extremely important.

Conventionally, this type of surge absorber has had a configuration as shown in FIG. In FIG. 6, numeral 1 denotes a plate-shaped varistor, which is generally made of ceramics whose main raw material is zinc oxide or strontium titanate. Reference numerals 2 and 3 denote electrodes formed at opposing positions on the front and back sides of the varistor 1 by baking silver paste or the like. 4 and 6 are lead wires connected to the electrodes 2 and 3 by soldering, etc.; 6 and 7 are the electrodes 2
These are the soldered parts of ゜3 and lead wires 4 and 6, respectively.

Regarding the conventional surge absorber configured as above,
The operation will be explained below.

The surge absorber shown in FIG. 6 is normally connected between signal lines and power supply lines where surge voltages enter or occur, and is used to suppress absorption of surge voltages due to its non-ohmic characteristics. The main characteristic of these surge absorbers is the varistor voltage (voltage at which current suddenly begins to flow), which is proportional to the thickness of the varistor 1 sandwiched between electrodes 2 and 3, and is also proportional to the surge resistance (the surge that can flow through it). The magnitude of the current) is from electrode 2 to
It has the characteristic that it is similarly proportional to the facing area of 3.

Problems to be Solved by the Invention The conventional surge absorber as described above has several problems due to its structure. First, it is necessary to change the thickness of the varistor depending on the applied circuit voltage.
It is complicated, and in order to obtain ultra-low voltage, the thickness of the varistor must be made extremely thin, and sufficient mechanical strength cannot be obtained. Furthermore, as a surge absorber, it has a large capacitance, making it unsuitable for high-frequency circuits.

The present invention aims to solve these problems,
The purpose is to provide a surge absorber with low capacitance that does not require changing the thickness of the varistor element from ultra-low to high voltage.

Means for Solving the Problems In order to solve the above problems, the present invention forms a plurality of divided electrodes on the surface of the varistor, and each electrode is used as an electric terminal.

Effect of the Invention With the above-described configuration, the present invention allows any varistor voltage to be obtained simply by controlling the distance between the divided electrodes, regardless of the element thickness of the varistor, and the surge resistance also depends on the length of the opposing electrodes on the varistor. By controlling it, it is possible to achieve any desired surge resistance, and since the surface of the varistor is used to express the varistor characteristics,
The effect is that the capacitance can also be made extremely small.

It has characteristics.

Embodiment FIG. 1 shows an embodiment of the surge absorber of the present invention, in which FIG. 1A is a plan view and FIG. 1A is a front view. In Figure 1,
8 is a plate-shaped varistor whose main material is zinc oxide, etc.; 9.
Reference numeral 10 denotes each electrode dividedly formed on one side of the varistor 80. Generally, the electrodes 9 and 10 are formed by screen printing a silver paste and then baking at 500 to 800°C, but other methods such as vapor deposition or plating of aluminum, nickel, chromium, gold, etc. may also be used. And t
is the electrode spacing between electrodes 9 and 10, and l is the electrode spacing between electrodes 9 and 10.
, 10 of the counter electrode length. The electrical terminals of the surge absorber formed in this way become electrodes 9 and 10, respectively.
It is used by being connected to external wiring by soldering or wire bonding.

Next, the operation of the surge absorber configured as above will be explained. First, the varistor voltage is determined by the electrode spacing distance t regardless of the thickness of the varistor 8, and the relationship is proportional to the thickness of the varistor in the conventional example. For example, when the electrode spacing distance t is 0.2U, a varistor voltage of about 15V is obtained; The characteristic is that 75V can be obtained at ofl.

Moreover, the varistor characteristics exhibit highly nonlinear characteristics even in the low current region due to the relationship between the counter electrode areas. Further, the surge resistance is proportional to the length l of the opposing electrode, and by doubling j, the surge resistance can be doubled without changing the varistor voltage. Furthermore, the capacitance is also extremely small due to the area of the opposite electrode. In this way, according to the present invention, even if the substrate thickness of the varistor is constant, by controlling the electrode spacing distance, it is possible to easily handle from ultra-low voltage (several volts) to high voltage, and it also has a low capacitance. It is possible to provide a surge absorber.

Next, FIG. 2(a) shows a second embodiment of the present invention.

(middle)). The difference from the first embodiment is that a groove is provided on the varistor surface between electrodes 9 and 1o at right angles to the direction in which the electrodes face each other. 11 is the groove described above. The action of the surge absorber formed in this way is similar to that shown in Figure 1, but since the distance between the electrodes has become longer in fact, a higher varistor voltage can be obtained even if the distance in the plan view is the same, making it suitable for high voltage applications. This has the effect of enabling miniaturization in terms of shape and size.

Next, regarding the third embodiment of the present invention, FIG. 3(a),
This will be explained along with (b). The difference from the embodiment shown in Fig. 1 above is that the electrodes extend from part of each electrode to part of the opposite side through the side of the varistor so that the surge absorber can be face-bonded onto the printed circuit board. It is a point. 1
2.13 is an electrode formed extending from the above-mentioned plane to the side surface to the back surface.

The function of the surge absorber formed in this manner is similar to that shown in FIG. 1, but it also has the additional effect of allowing face bonding.

Next, regarding the fourth embodiment of the present invention, FIG. 4 (4),
This will be explained together with Φ). The difference from the embodiment shown in Fig. 1 above is as follows.
The point is that an insulating coating is applied to the electrode facing part between the electrodes and the surface of the varistor. 14 is the above-mentioned insulating coating, which is usually made of glass baked at 400 to 850°C or resin cured at 100 to 300°C. By applying the coating in this manner, the weather resistance is increased and the electrical characteristics as a surge absorber are stabilized.

Effects of the Invention As described above, according to the present invention, by forming a plurality of divided electrodes on one plane of the varistor and obtaining varistor characteristics between the electrodes, the varistor voltage can be changed from an ultra-low voltage while keeping the element dimensions of the varistor constant. A surge absorber that can handle up to high voltages and has low capacitance can be provided.

Furthermore, by providing a groove on the varistor between the divided electrodes, a higher varistor voltage can be obtained with the same dimensions.

Furthermore, by extending a portion of each electrode to the side and back surfaces of the varistor, face bonding is possible.

Further, by applying an insulating coating between the divided electrodes, more stable electrical characteristics can be obtained.

In addition, in the embodiment of the present invention, two divided electrodes were used, but three
It goes without saying that the same effect can be obtained even in the case of a plurality of electrodes having an arbitrary number of electrodes and an arbitrary interval between the electrodes.

In the example, the opposing electrodes have a linear shape, but as long as the spacing is constant, it may be a sliding shape, a zigzag shape, or a square shape. In this case, the distance between the opposing electrodes becomes longer and the surge resistance is improved. It has the additional effect of being larger than the example.

Furthermore, in the example, split electrodes were formed only on one surface;
It can also be formed on the back side, and parallel application on the front and back sides is also possible.

[Brief explanation of the drawing]

FIG. 1(a) is a side view showing a one-piece surge absorber according to the present invention. 8...Varistor, 9.10...Divided electrode, 11...Groove, 14...Insulating coating. Name of agent: Patent attorney Toshio Nakao and 1 other person8-
- Hawasugu (bJ Muse: 18 #f 4 Figure 5 Figure

Claims (4)

[Claims] (1) A plate-shaped varistor has a plurality of divided electrodes on one plane, and the inter-electrode varistor voltage is set by the distance between the divided electrodes, and the surge resistance is set by the opposing length of the divided electrodes. A surge absorber characterized by: (2) The surge absorber according to claim (1), characterized in that a groove is provided on the varistor surface between the divided electrodes at right angles to the direction in which the divided electrodes face each other. (3) The surge absorber according to claim (1), wherein a portion of the divided electrode is formed to extend over a side surface of the varistor and a portion of the opposite surface. (4) The surge absorber according to claim (1), characterized in that an insulating coating is applied to the electrode facing portion between the divided electrodes and the surface of the varistor.