JPH0531280B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electrostatic absorber for protecting semiconductor devices such as ICs (integrated circuits) from electrostatic discharge.

BACKGROUND OF THE INVENTION In recent years, as electronic devices have become more multi-functional, computerization has been promoted in the fields of home appliances, information and communications equipment, industrial equipment, and the like. Although the ICs and LSIs (Large-Scale Integrated Circuits) used in this computerization have excellent functions, they are extremely sensitive to abnormally high voltages such as static electricity, which can cause electronic equipment to malfunction or be destroyed. There are many cases where this happens.
On the other hand, in many cases, such as semiconductor devices used in calculators and IC cards, it is impossible to avoid electrostatic discharge from the human body, and countermeasures against electrostatic discharge are extremely important.

Conventionally, this type of static electricity absorber has had a structure as shown in FIGS. 5a and 5b. In FIG. 5, 1 is a chip-shaped IC, which here corresponds to an element to be protected from static electricity. Reference numeral 2 denotes a substrate made of alumina or resin, and all the various functional parts are provided on this substrate 2. 3 and 4 are the above substrate 2
A signal line formed by printed wiring on the surface of the circuit, one end of which is connected to the above IC1,
The other end is connected to a signal input/output terminal (not shown). Further, one of the signal lines 3 and 4 is on the ground side, and here the signal line 4 is on the ground side. Reference numeral 5 denotes a chip-shaped varistor made of ceramic whose main raw material is zinc oxide or strontium titanate. Opposite electrodes 6 and 7 are formed on the front and back sides of this varistor 5. Here, in order to facilitate the electrical connection of the varistor 5, a portion of the electrodes 6 and 7 extends through the side surface of the varistor 5 to the opposite surface. 8 and 9 are barista 5
This is a bonding wire for connecting between the signal lines 3 and 4, and a gold wire or the like with a diameter of 20 to 30 μm is used. The varistor 5 is connected to the signal lines 3 and 4 by the bonding wires 8 and 9, respectively.
The varistor 5 is now connected between the signal lines 3 and 4. 10 is an adhesive for fixing the varistor 5 to the surface of the substrate 2.

The operation of the conventional static electricity absorber configured as described above will be explained below.

First, in most cases, static electricity accumulated in the human body is discharged to the input/output terminals of IC1 through the fingertips of the hands. Therefore, abnormally high voltage due to static electricity that has entered from the input/output terminal appears between the signal lines 3 and 4, and if the varistor 5 is not present, that high voltage will be applied to IC1 as it is, and IC1 will be destroyed in an instant. Become. However, since the varistor 5 is connected between the signal lines 3 and 4 as shown in FIG. 5, the static electricity is absorbed by the varistor 5 and the IC 1 is protected.

Problems to be Solved by the Invention However, with such a conventional configuration, there was a problem in that the characteristics of the varistor 5 could not be fully exhibited and the IC 1 could not be protected. That is, although the bonding wires 8 and 9 have extremely short lengths, they have a small inductance, so that a large voltage drop occurs in the bonding wires 8 and 9 due to static electricity having a high frequency component. For this reason, the voltage applied to IC1 is applied in addition to the limited voltage of varistor 5, and this voltage drop is applied, and the voltage actually applied to IC1 may be several times the limited voltage of varistor 5.

The present invention aims to solve these problems, and aims to provide a static electricity absorber in which the voltage applied to the semiconductor element is only the voltage limited by the varistor 5.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a method in which signal lines connected to a semiconductor element are formed by printed wiring, and opposite sides are connected between the signal lines formed by the printed wiring. Varistor 5 with electrodes
The electrodes on at least one side of the signal line form an electric path of the signal line.

Effects With the above configuration of the present invention, the limited voltage of the varistor seen from the signal input/output terminal side becomes the limited voltage of the varistor plus the voltage drop due to the inductance component, as in the conventional case, but from the semiconductor element side. As you can see, only the voltage is limited by the varistor, and a static electricity absorber with excellent protection properties can be obtained.

Embodiment FIG. 1 shows an embodiment of the static electricity absorber of the present invention, in which FIG. 1A is a plan view and FIG. In FIG. 1, reference numeral 11 is a semiconductor element such as an IC, which is usually chip-shaped, and here corresponds to an element to be protected from static electricity. 12 is a substrate;
Signal lines 13 and 14 correspond to the conventional substrate 2 and signal lines 3 and 4, respectively. Here, the signal line 13 is cut in the middle, and a terminal portion 14a extending from a part of the signal line 14 to the back surface of the varistor 15 is constructed using a printed wiring method, which is different from the conventional method. This is a different point. Further, the varistor 15 is a chip-shaped one made of ceramic whose main material is zinc oxide or the like, as in the prior art, and electrodes 16 and 17 are provided on the front and back surfaces of the varistor 15 to face each other. Wires 20 and 18 are electrically connected from both ends of the signal line 13 to the electrode 16 on the surface of the varistor 15 by bonding, respectively.
is the electrode 17 on the back surface of the varistor 15 and the terminal portion 1
4a is solder or conductive adhesive.

Next, the operation of the static electricity absorber configured as above will be explained. Now, if static electricity enters between the signal lines 13 and 14, wire 18 → electrode 16 → varistor 15 → electrode 17 → solder or adhesive 20 →
An electrostatic current flows through the route of the terminal portion 14a.
At this time, a voltage drop occurs in the wire 18 due to inductance, similar to the conventional example. however,
The voltage applied to the semiconductor element 11 is only the voltage on the surface of the electrode 16 of the varistor 15 through the wire 19, and the voltage drop across the wire 18 is not applied at all. In addition, for signal input/output, a part of the signal line 13 is cut off, but a part of the electrode 16, that is, between the bonding wires 18 and 19 on the electrode 16 serves as the electrode of the signal line. There is no problem with that.

Next, a second embodiment of the present invention will be described with reference to FIGS. 2a and 2b. The difference from the first embodiment is that the varistor 15 is connected to the signal line 14 without providing the terminal portion 14a. 21
is the cut portion of the signal line 14. The function of the static electricity absorber constructed in this way is similar to that shown in FIG. 1, but it also has the effect of reducing the voltage drop at the terminal portion 14a shown in FIG.

Next, a third embodiment of the present invention will be described with reference to FIGS. 3a and 3b. The difference from the second embodiment shown in FIG.
The point is that both electrodes 16 and 17 of No. 5 are both used as an electric path of a signal line. The function of the static electricity absorber constructed in this way is similar to that shown in FIG.
This has the effect of further improving the reduction in the voltage drop at point a.

Furthermore, a fourth embodiment of the present invention will be described with reference to FIG. The varistor 22 in this fourth embodiment has a structure similar to that of the conventional example shown in FIG. It is what was done. In FIG. 4, 23 is an electrode on the front side of the varistor 22 in a bridge shape between the cut portions of the signal line 13, and 24 is an electrode on the back side that is similarly connected in a bridge shape between the cut portions of the signal line 14. Connected with conductive adhesive. 25 and 2
6 is each connection part. In this fourth embodiment, as in FIG. 3, the electrodes 23 and 24 on the front and back surfaces of the varistor 22 serve as electrical paths for the signal lines 13 and 14,
It exhibits similar effects.

Effects of the Invention As described above, according to the present invention, at least one electrode of a varistor having electrodes facing each other on the front and back sides forms an electric path of a signal line, so that static electricity is not applied to a semiconductor element when absorbing static electricity. The voltage is not affected by the inductance of the connecting wire and is limited only by the varistor voltage, resulting in an excellent static electricity suppression effect.

[Brief explanation of the drawing]

Fig. 1a is a plan view showing an embodiment of the static electricity absorber according to the present invention, Fig. 1b is a sectional view taken along the E-Ro line in Fig. 2a, Fig. 3a, and Fig. 4a. are plan views showing the second to fourth embodiments of the present invention, and FIGS. 2b, 3b, and 4b are plan views of FIGS. 2a, 3a, and 4a, respectively. -2 line, Hohe line,
5A is a plan view showing a conventional static electricity absorber, and FIG. 5B is a sectional view taken along the line line in FIG. 5A. 11... Semiconductor element, 13, 14... Signal line, 15, 22... Varistor, 16, 17, 2
3, 24...electrode.

Claims (1)

[Claims] 1 A signal line connected to a semiconductor element is formed by printed wiring, and an electrode on at least one side of a varistor having electrodes facing each other on the front and back sides connected between the signal lines formed by the printed wiring connects the electric path of the signal line. A static electricity absorber characterized by being configured to form a static electricity absorber.