JPS61110999A - Electrostatic 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 Field of the Invention The present invention relates to an electrostatic absorber for protecting semiconductor devices such as ICs 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 IC1LSI and the like used for this computerization have excellent functions, they are extremely sensitive to abnormally high voltages such as static electricity, which often causes malfunction or destruction of electronic equipment. However, in many cases, such as semiconductor elements used in calculators, IC cards, etc., 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 is shown in Figures 3(a) and (b).
) The configuration was as shown in . The figure (&) is a plan view thereof, and the figure (1)) is a sectional view from a to a. Figure 3(a)
, mountain), 1 is usually a chip-shaped XG, which here corresponds to an element to be protected against static electricity. Reference numeral 2 denotes a substrate made of alumina or resin, on which all various functional parts are assembled.

3.4 is a signal line in the form of a printed wiring made of copper, silver, palladium, etc. on the surface of the board 2. In Fig. 3(a), the left side is connected to IO1, and the right side is connected to the signal input/output terminal. It is connected. One of the signal lines is on the ground side, and here the signal line 4 is on the ground side. 6 is a chip-shaped static electricity absorption element, such as a varistor whose main raw material is zinc oxide or strontium titanate, a tantalum or aluminum electrolytic capacitor, or an Avalan 7E diode made of silicon. The varistor 5 has electrodes at both ends. 6
a and 6b are printed wiring boards outside the portion where the varistor 6 is connected to the signal line 3.4.

7a and 7b are solders used for connection, and connections are usually made by dipping into a solder bath, reflow, etc.

The operation of the static electricity absorber constructed as above will be explained below.

First, in most cases, static electricity accumulated in the human body is discharged to the input/output terminals of an IC through the fingertips of the hands. Therefore, an abnormal voltage due to static electricity entering from the signal input/output terminal appears between the signal lines 3 and 4, and if the varistor 5 were not present, that high voltage would be directly applied to the IC 1, and the IC 1 would be destroyed in an instant. However, since the varistor 5 is connected between the signal lines 3 and 4 as shown in FIG. 3, the abnormal voltage caused by electrostatic discharge can be absorbed by the varistor 5, and the IC 1 is protected. However, in such a conventional configuration, the IC1
The problem was that it could not be protected.

In other words, since the frequency component of the abnormal voltage in electrostatic discharge is extremely high, the voltage that is suppressed by the varistor 6 is only the voltage that passes through the printed wiring in the part where the varistor 6 is connected, and the unconnected part in FIG. 6N, 6b
The effect of suppressing abnormal voltage passing through the area is low. In particular, the wider the printed wiring width of the signal lines 3 and 4, the more this adverse effect appears.

Therefore, the voltage applied to IC1 was higher than the voltage truly suppressed by varistor 5, and the protection effect for IC1 was not sufficient, and IC1 was often destroyed.

SUMMARY OF THE INVENTION The present invention solves these problems, and aims to provide a static electricity absorber that lowers the voltage applied to an IC to the voltage limit level of the static electricity absorbing element and has excellent protection characteristics.

Means for Solving the Problem In order to solve this problem, in the present invention, the width of the printed wiring in the part where the varistor is connected is narrower than in other parts, so that all the abnormal voltage is transmitted to the part where the electrostatic absorption element is connected. The configuration is such that all light passes through.

Effect: With this configuration, abnormal voltage due to electrostatic discharge entering from the signal line always passes through the connection portion of the electrostatic absorption element before proceeding to the IC. The voltage after passing through is only the so-called limiting voltage of the static electricity absorbing element, resulting in a static electricity absorber with excellent protection characteristics.

Actual case FIG. 1 shows a static electricity absorber according to an embodiment of the present invention.

In FIG. 1, 14 is a semiconductor such as a chip-shaped IC (
(hereinafter referred to as an IC), which here corresponds to an element to be protected against static electricity, and 8 is a board made of aluminum or resin, and various functional parts are incorporated into this board 8. 9,1
On the surface of the substrate 8 of the oven, there is a signal line in the form of a printed wiring made of copper, silver, palladium, etc., and one side is connected to the above-mentioned IC 14.
The other end is connected to the signal input/output terminal. This signal line 10 is used as a ground side.

Reference numeral 11 designates a chip-shaped static electricity absorption element, which can be a varistor whose main material is zinc oxide or strontium titanate, a tantalum or aluminum electrolytic capacitor, or an avalanche diode made of silicon or the like. Wiring constriction 1 is made thinner than the entire width of the printed wiring at the point where the static electricity absorbing element 11 is connected to the signal lines 9, 1o.
2 is provided.

Next, the operation of one embodiment of the static electricity absorber formed as described above will be described below.

If an abnormal voltage due to electrostatic discharge enters between the signal lines 9 and 10, the path to the IC14 must always pass through the connection point of the electrostatic absorption element 11, and it must be directly connected to the IC1.
There is no path leading to 4. Therefore, the voltage that passes through the static electricity absorption element 11 and is applied to lG14
Only 1 control voltage is required, and excellent protection characteristics can be obtained.9
Further, the current capacity of the wiring constriction portion 12 is almost the same as that of other portions. This is because solder and the like when connecting the static electricity absorbing element 11 are formed on the constricted portion 12 of the wiring, which increases the thickness.

A second embodiment of the present invention will be described below.

FIG. 2 shows a second embodiment of the invention.

The difference from the first embodiment described above is that the shape of the wiring constriction 12 is a slit-like constriction 13. All other symbols are the same as in the first embodiment.

Well, the action of the static electricity absorber constructed in this way is the first.
However, in addition to this, the second actual case has the feature that the soldering area of the electrostatic absorption element 11 is wide.

In addition, 1. In the second embodiment, the signal lines 9 and 1
Although the wiring constriction 12 or 13 is provided on both sides of Q, if the signal line 1o is a common ground plane, the signal line 9
A similar effect can be obtained by providing only the wiring constriction portion 12 or 13.

Effects of the Invention As described above, according to the present invention, by making the width of the printed wiring in the part where the static electricity absorption element is connected narrower and constricted than in other parts, abnormal voltage caused by electrostatic discharge can be restricted by the static electricity absorption element. This has the effect of providing excellent protection characteristics such as suppressing the voltage and applying only a safe low voltage to the IC.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a static electricity absorber according to an embodiment of the present invention, FIG. 2 is a plan view of the second embodiment, and FIGS. 3 a and 3 b are plan views showing the configuration of a conventional static electricity absorber. FIG. 8・°・・・°board, 9,1o・・・signal line,
11...Static electricity absorption element, 12.13...-
Wiring constriction, 14...IC.

Claims (1)

[Claims] A static electricity absorption device characterized in that a signal line of a semiconductor device is formed by printed wiring, and a portion of at least one of the printed wirings to which a static electricity absorption element is connected is formed narrower than the other portion. vessel.