Material of over voltage protection device, over voltage protection device and manufacturing method thereof

Abstract

The present invention relates to a material of an over voltage protection device and an over voltage protection device manufactured by the material. The material comprises a non-conductive powder, a metal conductive powder, and an adhesive. The over voltage protection device comprises a first electrode, a second electrode, and a porous structure connected between the first electrode and the second electrode. The present invention also relates to a method for manufacturing the over voltage protection device. The present invention also relates to a method of adjusting the breakdown voltage of an over voltage protection device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an I-V curve of the material structure disclosed in U.S. Pat. No. 5,068,634;

FIG. 2 is a circuit diagram of a transmission line pulse (TLP) system;

FIG. 3 is an equivalent circuit diagram of the TLP system shown in FIG. 2;

FIG. 4 is a photograph of a compact structure or a structure with few pores generated by sintering a non-conductive material with a high melting point by using the conventional technology;

FIG. 5 is a photograph of a porous structure formed by sintering the material of the over voltage protection device provided by the present invention;

FIG. 6 is an I-V curve of the material and structure of the present invention;

FIG. 7 is a plan view of an over voltage protection device 70 according to an embodiment of the present invention;

FIG. 8 is a side view of the over voltage protection device 70 of FIG. 7;

FIG. 9 is an I-V curve of an embodiment of the present invention;

FIG. 10 is a plan view of an over voltage protection device 100 according to another embodiment of the present invention;

FIG. 11 is a side view of the over voltage protection device 100 of FIG. 10;

FIG. 12 is an I-V curve of another embodiment of the present invention; and

FIG. 13 is an I-V curve of still another embodiment of the present invention.

DETAILED DESCRIPTION

The present invention will be described in detail with reference to the drawings, some of which depict preferred embodiments of the present invention. The present invention is illustrated by several embodiments but not limited to the embodiments.

In an electrostatic discharge (ESD) protection circuit, an ESD current is released in a first breakdown area of a device, and the device will not be damaged in the first breakdown area. The first breakdown area has a limit, which is a characteristic of so-called secondary breakdown. When an external overstress voltage or current enters the secondary breakdown area, the device will be damaged permanently. Therefore, the current at the secondary breakdown point represents the upper limit of the capability of the ESD protection device. A transmission line pulse (TLP) system is specially designed to measure the characteristics of the secondary breakdown of the device or an integrated circuit and is a special measuring device that is capable of analyzing the physical characteristics of the device under a high voltage/current test. The TLP system employs the TLP generation principle to provide a single pulse with continuously increasing energy. The principle and the equivalent circuit diagram thereof are shown in FIGS. 2 and 3, respectively. Under the circumstance that a switch SW1 is turned on and a switch SW2 is turned off, a high-voltage generator 23 is used to provide a high voltage to a transmission line 22 via a resistor R_H. After that, the switch SW2 is turned on to make a charged transmission line 22 generate a pulse, which is then transmitted to a device under test (DUT) 21, wherein the values of the voltage and current of the DUT 21 are measured via an oscilloscope. FIG. 3 is an equivalent circuit diagram of FIG. 2. A pulse-generating source 31 with a constant pulse width t supplies energy to the DUT 21 through a load resistor R_L, and the values of the voltage and current of the DUT 21 are measured via the oscilloscope (not shown).

The I-V curves in FIGS. 6, 9, 12, and 13 of the present invention are all measured by using the TLP system shown in FIGS. 2 and 3.

The material of the over voltage protection device provided by the present invention at least includes a non-conductive powder with a particle size in the range of 1-50 μm, a metal conductive powder with a particle size in the range of 0.01-5 μm, and an adhesive. The adhesive is glass and/or polymer resin. If the adhesive is a glass powder, a firing treatment is performed at a temperature of 300-1200° C.; if the adhesive is a polymer resin, the firing treatment is performed at a temperature from a room temperature to 600° C.; and if the adhesive is a mixture of glass powder and polymer resin, the firing treatment is performed at a temperature of 300-600° C. After the aforementioned materials are mixed uniformly, a porous structure with pores of less than 10 μm is formed through the firing treatment. The pores occupy about 5%-90% of the whole volume of the porous structure. The metal conductive powders are uniformly attached to the surface of the non-conductor and distributed in spots. By using a metal conductor in the structure as a conductive medium, the current is continuously bounding by means of point discharge, so as to let the over voltage energy pass through a device having a material structure with micro-clearance discharge points.

Basically, the material and structure of the present invention are obtained by miniaturizing the mechanism of the point discharge principle and a gas discharge device, so as to possess the advantages of a low trigger voltage and a long service life. Furthermore, the material and structure of the present invention may be fabricated as a chip-type device through a conventional commercialized process.

The material of the present invention presents a porous structure after being fired into a product and the metal conductors are uniformly distributed on the surface of the non-conductor. The gaps between the metal conductors are in the range of 0.1-10 μm. The porous structure has stacked pores naturally formed when the non-conductive powders are stacked together. The structural strength, i.e., the adhesion between powders, is not generated by the sintering process, but by using a certain amount of suitable adhesive.

The non-conductor of the material of the present invention may be selected to be an oxide or carbide with a high melting point. In order to sinter the material into a compact structure or a structure with few pores, such as a zinc oxide varistor shown in FIG. 4, the non-conductor with a high melting point is required to be treated by a sintering process at a temperature of over 1200° C., and sometimes a high pressure is further needed, and even a special sintering process. In the present invention, by utilizing the non-conductor's property of being difficult for sintering, a suitable glass is selected to be used as the adhesive between the powders, so as to fabricate a porous structure.

For example, SiC with a decomposition temperature of about 2600° C. is not sintered below 1200° C., a conventional manufacturing temperature for a thick film process or a multilayer process, and particles are bonded and fixed together through an appropriate amount of suitable adhesive, so as to form a porous structure. Through selecting an adhesive with a suitable characteristic and through adjusting the dosage, the adhesive does not fully cover all the surfaces of the matrix and the metal conductor, so that an insulation coating will not formed.

Furthermore, for example, Al₂O₃ with a melting point of 2000° C. is not sintered below 1000° C., a conventional sintering temperature for a thick film process, and particles are bonded and fixed together through an appropriate amount of suitable adhesive, so as to form a porous structure. Through selecting an adhesive with a suitable characteristic and through adjusting the dosage, the adhesive does not fully cover all the surfaces of the matrix and the metal conductor, so that an insulation coating will not formed.

The non-conductive powders of the material of the present invention are high temperature glass powders, for example, glass powders containing over 90% of SiO₂. The glass powders maintain a porous structure below 1200° C., a conventional temperature for a thick film process or a multilayer process.

The metal conductive powders of the material of the present invention include Al, Au, Ni, Cu, Cr, Fe, Zn, Nb, Mo, Ru, Pb, Ir, Ti, Ag, Pd, Pt, or W, or a mixture thereof, or an alloy thereof. The metal conductive powders are uniformly attached to the surface of the porous structure to form “discharge positions,” i.e., positions for the point discharge. The discharge gap, i.e., the distance between each of the “discharge positions,” is determined by the dosage and dispersibility of the metal conductive powders in the material. Since the discharge micro-clearance formed when the material is fired at the temperature of 600-1200° C. is mostly below 10 μm, or even only 1 μm, and there is a huge number of discharge positions in a unit of area, the voltage value required by performing the discharge is greatly reduced.

During the discharge process, when the discharge energy gets close to or contacts the discharge positions on the surface of the base matrix, the discharge occurs and then it is conducted from a source to a “discharge position.” After that, the energy is discharged from the point of the “discharge position” to a next adjacent discharge position, and so forth, till the ground line at the other end is reached.

The material and structure of the over voltage protection device of the present invention are shown in FIG. 5, wherein the gray portions are the non-conductor and the glass, the white portions are metal conductors, and the black portions are holes. The material and structure of the present invention follows the I-V curve shown in FIG. 6, wherein Vt in FIG. 6 represents a trigger voltage, and Vc represents a clamping voltage.

The breakdown voltage of the over voltage protection device of the present invention is adjusted through the following methods:

1. Adjust the porosity (i.e., the percentage of the volume of the pore in the whole volume of the porous structure), i.e., adjust the dosage, particle size, and shape of the non-conductive powders.

2. Adjust the dosage or particle size of the metal conductive powders, so as to control and change the distance between the metal conductive powders uniformly attached to the surface of the non-conductor.

3. The contacting situation and extent of the powders are determined by the particle size and shape of the powders, and the area of the powders covered by the adhesive (glass and/or polymer resin), and particularly, for the glass material, it is determined by the glass transition temperature, the high temperature fluidity, and the dosage, and as for the polymer material, it is relevant to the fluidity and dosage.

FIGS. 7 and 8 are a plan view and a side view of an over voltage protection device 70 according to an embodiment of the present invention. In this embodiment, 10 wt % of Ag powders, 50 wt % of Al₂O₃ powders, and 10 wt % of glass powders are compounded with 30 wt % of ethyl cellulose resin solution by using a 3-roll mill, so as to form a paste 75 for printing.

Firstly, a first electrode 72 and a second electrode 73 are formed on an Al₂O₃ substrate 71, and then, a paste 75 is applied on a part of the first electrode 72 and the second electrode 73 close to gap 74. After the firing treatment at 850° C., the material 75 of the present invention is attached to the Al₂O₃ substrate 71, the first electrode 72, and the second electrode 73. The first electrode 72 is connected to the circuit of a system, and the second electrode 73 is connected to a ground line, so that the device 70 is connected with the system (not shown) in parallel. When an abnormal energy enters the system, it is conducted to the material 75 via the first electrode 72, and then, discharged through micro-gaps within the material 75. Then, the over voltage energy is transmitted to the second electrode 73 and then to the ground line. The I-V curve in this embodiment is shown in FIG. 9.

FIGS. 10 and 11 are a plan view and a side view of an over voltage protection device 100 according to another embodiment of the present invention. In this embodiment, ingredients of a paste 104 are the same as that of the paste 75 in the first embodiment. Firstly, a first electrode 102 is formed on an Al₂O₃ substrate 101. Then, the paste 104 of the present invention is printed on the first electrode 102, wherein a part of the paste 104 is printed on the first electrode 102, and the rest is printed on the Al₂O₃ substrate 101. Finally, a second electrode 103 is formed, wherein a part of the second electrode 103 is attached to the paste 104 and the rest is attached to the Al₂O₃ substrate 101. After the firing treatment at 850° C., the material 104 of the present invention is attached to the Al₂O₃ substrate 101 and the first electrode 102, and the second electrode 103 is attached to the material 104 and the Al₂O₃ substrate 101. The first electrode 102 is connected to a system (not shown), and the second electrode 103 is connected to the ground line, so that the device 100 is connected to the system in parallel. When an abnormal energy enters the system, it is conducted to the material 104 via the first electrode 102, and discharged through micro-gaps within the material 104. Then, the over voltage energy is transmitted to the second electrode 103 and then to the ground line. The I-V curve in this embodiment is shown in FIG. 12.

In another embodiment of the present invention, 15 wt % of Pt powders, 45 wt % of Al₂O₃ powders, and 15 wt % of glass powders are mixed with 25 wt % of ethyl cellulose resin solution by using a 3-roll mill, so as to form a paste for printing, and then, a structure that is the same as that in the second embodiment is fabricated. The I-V curve in this embodiment is shown in FIG. 13.

The features and technical contents of the present invention have been disclosed above and those skilled in the art may make variations or modifications according to the disclosure and teachings of the present invention without departing from the spirit of the present invention. Therefore, the scope of the present invention to be protected should cover not only the aforementioned embodiments, but also the variations and modifications.

Claims

1. A material of an over voltage protection device, comprising: a non-conductive powder;a metal conductive power; andan adhesive.

2. The material of an over voltage protection device as claimed in claim 1, wherein the non-conductive powder has a particle size between 1 μm and 50 μm.

3. The material of an over voltage protection device as claimed in claim 1, wherein the metal conductive powder has a particle size between 0.01 μm and 5 μm.

4. The material of an over voltage protection device as claimed in claim 1, wherein the adhesive comprises a glass powder.

5. The material of an over voltage protection device as claimed in claim 1, wherein the adhesive comprises a polymer resin solution.

6. The material of an over voltage protection device as claimed in claim 1, wherein the adhesive comprises a glass powder and a polymer resin solution.

7. The material of an over voltage protection device as claimed in claim 1, wherein the non-conductor is a carbide with a high melting point.

8. The material of an over voltage protection device as claimed in claim 7, wherein the carbide with a high melting point is SiC.

9. The material of an over voltage protection device as claimed in claim 1, wherein the non-conductive powder is an oxide with a high melting point.

10. The material of an over voltage protection device as claimed in claim 9, wherein the oxide with a high melting point is Al2O3.

11. The material of an over voltage protection device as claimed in claim 1, wherein the non-conductive powder is a high-temperature glass powder.

12. The material of an over voltage protection device as claimed in claim 11, wherein the high-temperature glass powder is a glass powder containing more than 90% SiO2.

13. The material of an over voltage protection device as claimed in claim 1, wherein the metal conductive powder is selected from a group consisting of Al, Au, Ni, Cu, Cr, Fe, Zn, Nb, Mo, Ru, Pb, Ir, Ti, Ag, Pd, Pt, or W, a mixture thereof, or an alloy thereof.

14. A method of manufacturing an over voltage protection device, comprising: uniformly mixing a non-conductive powder, a metal conductive powder, and an adhesive into a paste in a predetermined proportion;printing the paste on a substrate; andperforming a firing treatment on the substrate to produce the over voltage protection device.

15. The method as claimed in claim 14, wherein the step of printing the paste on the substrate comprises: forming a first electrode and a second electrode on the substrate; andprinting the paste on the substrate, wherein the paste partially overlaps the first electrode and the second electrode.

16. The method as claimed in claim 14, wherein the step of printing the paste on the substrate comprises: forming a first electrode on the substrate;printing the paste on the substrate, wherein the paste partially overlaps the first electrode; andforming a second electrode on the substrate, wherein the second electrode partially overlaps the paste.

17. The method as claimed in claim 14, wherein if the adhesive is a glass powder, the firing treatment thereof is performed at a temperature of 300-1200° C.

18. The method as claimed in claim 14, wherein if the adhesive is a polymer resin solution, the firing treatment thereof is performed at a room temperature to 600° C.

19. The method as claimed in claim 14, wherein if the adhesive is a glass powder or a polymer resin solution, the firing treatment thereof is performed at a temperature of 300-600° C.

20. An over voltage protection device, comprising: a first electrode;a second electrode; anda porous structure, connected between the first electrode and the second electrode, wherein the porous structure is produced by performing a firing treatment on the material of the over voltage protection device as claimed in any one of claims 1-13.

21. The over voltage protection device as claimed in claim 20, wherein the pore of the porous structure is below 10 μm.

22. The over voltage protection device as claimed in claim 20, wherein pores of the porous structure occupy 5%-90% of the volume of the porous structure.

23. The over voltage protection device as claimed in claim 20, further comprising a substrate, wherein the first electrode and the second electrode are both attached to the substrate and spaced by a gap and the porous structure is deposited on a part of the first electrode and a part of the second electrode and in the gap.

24. The over voltage protection device as claimed in claim 20, further comprising a substrate, wherein the first electrode is deposited on the substrate, the porous structure is deposited on the substrate and the first electrode, and the second electrode is deposited on the substrate and the porous structure.