JPS6139742B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an integrated circuit with improved protection circuitry, particularly against external surge voltages.

Generally, integrated circuits installed in environments susceptible to external surge voltages such as overvoltage require a protection circuit against external surges. For example, an external surge voltage generated by an ignition spark is applied to a hybrid thick film integrated circuit used in an automobile ignition system, etc. to its external terminal, and if the energy of the ignition spark is large, the above-mentioned Circuit elements of thick film integrated circuits may be destroyed. In order to protect circuit elements from such external surge voltages, an integrated circuit 1 is conventionally constructed as shown in FIGS.
1 is provided with a protection circuit. That is, as shown in FIG. A, a capacitor 14 having a sufficiently large capacitance is provided at the external terminal 13 for connecting the external wiring and the internal circuit 12. The protection circuit made up of the capacitor 14 can protect the circuit elements of the internal circuit 12 by absorbing the energy of external surges. Also, as shown in Figure B, capacitor 1
4 may be replaced by a Zener diode 15 having large power characteristics. However, such a protection circuit has drawbacks such as deterioration of the frequency response of the integrated circuit 11, increase in chip area, and high cost of the large capacitance capacitor 14 when a large capacitance capacitor 14 is used. Further, when the Zener diode 15 is used, the amplitude of the input signal to the integrated circuit 11 is limited, and there is a drawback that a sufficient dynamic range cannot be obtained.

As a means to solve such drawbacks, as shown in FIG. 2A (only necessary parts are shown in the plan view), a substrate (for example, ceramic) 2
A pad part 22 made of silver, palladium, etc., which is connected to an external terminal (not shown), is provided on the pad part 1, and a gap 23 is formed between the pad part 22 and a predetermined distance, that is, a gap 23.
A metal film 24 of silver, palladium, etc. is provided using the following steps. This metal film 23 is arranged so as to obtain a ground potential.
For example, it is connected to a circuit ground power line (not shown). In such a protection circuit, when an external surge voltage is applied to the pad portion 22, dielectric breakdown of air occurs at the gap 23, and the external surge is discharged to the metal film 24 at ground potential. The circuit elements connected to the pad portion 22 can be protected. Furthermore, the frequency response and amplitude characteristics of the integrated circuit 11 do not deteriorate as described above.

Incidentally, in the thick film integrated circuit as described above, the entire substrate 21 is often coated with a resin 25 such as silicone gel, as shown in FIG. 2B (cross-sectional view), for moisture resistance and the like. Such resin 25 has a much higher dielectric strength voltage than normal air. Therefore, when an external surge voltage is applied to the pad portion 22 from the external terminal 13, no dielectric breakdown occurs in the resin 25 existing at the gap 23, and the external surge is not discharged to the metal film 24 at the ground potential. There is a drawback that the protection operation becomes unstable due to the presence of certain conditions.

This invention was made in view of the above circumstances, and can reliably protect circuit elements against external surge voltages applied to external terminals.
An object of the present invention is to provide an integrated circuit with stable circuit operation and high reliability.

An embodiment of the present invention will be described below with reference to the drawings. 3A and 3B show the configuration (only necessary parts are shown) of an integrated circuit 11 according to an embodiment of the present invention, and as shown in FIG. A pad portion 22 made of, for example, silver or palladium is provided to be connected to a circuit element (not shown) constituting the circuit. A metal film 24 of silver, palladium, etc. is provided at a predetermined distance from this pad portion 22, that is, with a gap 23.
This metal film 24 is connected to, for example, a ground power line (not shown) of the integrated circuit so as to obtain a ground potential.
Then, a pad part 22 is attached to this gap 23.
An insulating film 31, such as a solder resist, having a sufficiently low dielectric strength voltage is provided so that the metal film 24 and the metal film 24 are connected to each other. Furthermore, for the entire substrate 21,
As shown in FIG. B (cross-sectional view), it is coated with a resin 25 such as silicone gel having a high dielectric strength for moisture resistance and the like.

In the integrated circuit configured in this way, the third
As shown in Figure B, when an external surge voltage is applied from the external terminal 13 connected to the pad portion 22, the insulating film 31 has a sufficiently lower dielectric strength voltage than, for example, the resin 25, so the overvoltage due to the external surge etc. dielectric breakdown occurs relatively easily. Therefore, the pad portion 22 and the metal film 24 at the ground potential are in a conductive state, and most of the external surge is caused by the pad portion 2.
2 to the metal film 24, the circuit elements can be protected from external surge voltage.

4A and 4B show another embodiment of the present invention, in which an insulating film 3 serves as a bypass for discharge of an external surge applied to the pad portion 22 in the above embodiment.
1 is replaced by a film 41 made of metal oxide or the like (hereinafter referred to as a high resistance film) having a high resistance of, for example, 100 KΩ or more. In this case as well, the effect is almost the same as in the above embodiment, but the high resistance film 41 is more likely to have a bypass effect, that is, to cause external surge discharge than the insulating film 31, so that a relatively reliable protective operation can be achieved. can be done. However, in this case, a part of the input signals necessary for circuit operation other than external surges will flow from the pad section 22 to the metal film 24 at ground potential, so that the input signals, etc. that are necessary for circuit operation other than external surges will flow from the pad section 22 to the metal film 24 at the ground potential. It is desirable to provide the high resistance film 41. Note that the other configurations and operations are the same as those in the above embodiment, so explanations will be omitted.

FIG. 5 shows still another embodiment of the present invention, in which a pad portion 22 and a metal film 2 at ground potential are shown.
Multiple gaps 23a-23c between 4a-24c
An insulating film 31 with a low dielectric strength and a high resistance film 4 are provided at each gap 23a, 23b.
1 are provided respectively, and a pad portion 22 and a metal film 2 are provided.
4a and 24b are connected. Furthermore, the pad part 2
A resin such as silicon gel, which is normally used to cover the substrate 21, is provided in the gap 23c between the metal film 24c and the metal film 24c.

In an integrated circuit having such a configuration, the pad portion 22
Since there are multiple bypasses for discharging external surges applied to the circuit, and each bypass is made of an insulating film 31 and a high-resistance film 41 made of different materials, protection can be performed more reliably against external surges over a wide range of overvoltage, etc. The effect is that Note that the other configurations and operations are the same as those in the above embodiment, so explanations will be omitted.

In addition, in the above embodiment, the metal film 2 at the ground potential
4 via the insulating film 31 or the high resistance film 41 is not limited to the pad portion 22, but may be any metal film connected to a circuit element and an external terminal. Further, the high resistance film 41 is not limited to metal oxide, and may be made of other materials such as a semiconductor.

As described in detail above, according to the present invention, the external surge voltage applied to the external terminals of the integrated circuit is reliably discharged to the metal film at ground potential provided in advance, thereby protecting the circuit elements. can be done reliably. Moreover, since capacitors and Zener diodes are not used in the protection circuit,
The frequency response, amplitude characteristics, etc. of the integrated circuit are not adversely affected, and the circuit operation can always be kept stable.

[Brief explanation of the drawing]

1A and 1B are block diagrams of a conventional integrated circuit, and FIGS. 2A and 2B are diagrams showing a protection circuit section of a conventional integrated circuit, in which figure A is a plan view, figure B is a cross-sectional view, 3A and 3B are diagrams showing a protection circuit section of an integrated circuit according to an embodiment of the present invention, in which FIG. 3A is a plan view, FIG. 3B is a sectional view, and FIGS. FIG. 5 is a diagram showing a protection circuit section of an integrated circuit according to another embodiment, where A is a plan view, B is a sectional view, and FIG. 5 is a protection circuit of an integrated circuit according to still another embodiment of the present invention. FIG. DESCRIPTION OF SYMBOLS 11... Integrated circuit, 13... External terminal, 14... Capacitor, 15... Zener diode, 21... Substrate, 22... Pad part, 23, 23a-23c... Gap, 24, 24a-24c... Metal film, 25...
Resin, 31... Insulating film, 41... High resistance film.

Claims (1)

[Claims] 1. A substrate on which a predetermined circuit is configured, a first metal film connected to external wiring as part of the circuit on this substrate, and a predetermined interval between the first metal film and the first metal film. a second metal film with a ground potential provided on the substrate; a resin provided on the substrate for protection of the circuit; and a resin provided between the first and second metal films on the substrate. and an insulating film having a dielectric strength lower than at least the resin, which connects the first and second metal films. 2. A substrate on which a predetermined circuit is configured, a first metal film connected to external wiring as part of the circuit on this substrate, and a first metal film on the substrate with a predetermined distance from the first metal film. a second metal film provided at a ground potential, a resin provided on the substrate for protection of the circuit, and a resin provided between the first and second metal films on the substrate, and An integrated circuit comprising: a high resistance film connecting two metal films.