JP2009088416A - Overvoltage protection device for electronic circuit and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an overvoltage protection device for an electronic circuit with a simple manufacturing method at a low cost. <P>SOLUTION: A multilayered structure of a buffer layer 41, an internal-electrode conducting layer 42, a dielectric layer 43, and an external-electrode conducting layer 44 is formed on a ceramic substrate, with a gap 5 of an appropriate depth to intersect the ceramic substrate in a cutting process after completion of overall structure. Accordingly, two overlapped electrode layers 42, 44 are divided to two opposite portions by the transversing gap, and also divided to the internal and external electrode conducting layers 42, 44 by the dielectric layer 43. Different kind of solid or gaseous material is injected into the gap 5 by using the structure, and therefore the gap serves as a protecting element against an electrostatic discharge by using the dielectric layer 43 of the appropriate thickness, thereby resulting in utilizing all the structure as the protection elements to various kinds of electronic circuits. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an overvoltage protection device for an electronic circuit and a manufacturing method thereof, and more particularly to a device having the following structure. The inner electrode conductor layer, the dielectric layer, and the outer electrode conductor layer are sequentially formed on the substrate, so that the dielectric layer is sandwiched between the inner electrode conductor layer and the outer electrode conductor layer. . Next, a transverse gap is formed that bisects the inner electrode conductor layer, the dielectric layer, and the outer electrode conductor layer perpendicular to the ceramic substrate surface. That is, the dielectric layer has a structure in which the electrode layer is separated into two electrode layers, an inner electrode conductor layer and an outer electrode conductor layer, and a gap separates each electrode layer and the dielectric layer into two parts. The present invention relates to a protection device for an electronic circuit. Therefore, an electrostatic discharge path is formed between the outer electrode and the inner electrode in order to obtain a circuit element having the function of protecting the electronic circuit from surge voltage.

  As is well known, capacitors, resistors, and inductors are three essential passive circuit elements for electronic devices. The capacitor is formed by interposing a dielectric material between two conductive materials, has a function of storing electrical energy, and functions as an element constituting a filter, a modulator, an oscillator, or the like. Capacitors can be roughly classified into fixed capacitors, variable capacitors, and crystal capacitors according to dielectric materials. The resistor has a function of limiting current. The inductor eliminates electromagnetic interference by removing current noise. These three elements are related to each other in controlling electronic circuits in the field of electronic devices such as information communication.

  In a communication circuit, an overvoltage caused by an electrostatic discharge (Electro-Static Discharge (ESD)) may seriously damage components of an electronic device such as a substrate, and may affect a loss of the entire electronic product. is there. Generally, electronic devices use a combination of passive elements (resistors, capacitors, and inductors) to protect electronic products from surge voltage strikes caused by ESD.

  The ESD protection device includes a transient voltage suppression diode (TVSD), a multi-layer varistor (MLV), and a gap, and an ESD protection method (ESD) using these ESD protection devices. Examples of the protection means include a shield using a transient voltage suppression diode or the like, a gap discharge using a gap, and a charge / discharge function of a capacitor using various varistors.

  In order to protect the electronic device from the blow of the ESD, in the PCB (Printed-Circuit Board) arrangement, the gap discharge electrode shown in FIG. 1A is directly provided at the place where the ESD protection is required, which is to reduce the product cost. Are included at the same time as PCB manufacturing.

  In FIG. 1A, a circuit 11 in which a discharge electrode 12a having a pointed tip is formed on a PCB substrate 10 functions as an ESD protection means, and a gap 13 is formed between the discharge electrode 12a and the other grounded pointed discharge electrode 12b. Between.

  Referring to FIG. 1B together with FIG. 1A, in FIG. 1B, the vertical axis represents power due to surge voltage, and the horizontal axis represents time. When an overvoltage due to surge voltage 15 appears in circuit 11 with the energy indicated by ESD curve 16, breakdown occurs in gap 13 between electrodes 12a and 12b. Therefore, in order to protect the circuit 11, the amplitude of the overvoltage must be limited to a range that the circuit 11 can tolerate, as shown by the curve 17.

  However, when carefully investigated, the above-described protection mode is considered incomplete due to the following drawbacks.

  (1) The gap 13 formed by mechanical cutting cannot be made narrow enough to reach a distance that is sufficient to protect against ESD surge voltages.

  (2) Since the width of the gap 13 cannot be reduced to a required distance, the breakdown voltage increases and the electronic circuit and device cannot be protected.

  Since these deficiencies in the prior art are obvious, improvements are strongly desired. The inventor of the present invention has been devoted to researching and improving these defects for many years, and has come up with a new overvoltage protection device for electronic circuits and a method for manufacturing the same provided in the present invention.

  An object of the present invention is to form a gap in a multilayer structure including a buffer layer, an inner electrode conductor layer, a dielectric layer, and an outer electrode conductor layer on a ceramic substrate, and fill the dielectric material or gap of the dielectric layer. By using materials having different characteristics as the material to be used, the structure composed of each of the above layers has different capacitances or inductors, thereby protecting various types of resistors, capacitors, or electronic circuits including inductors. It is to provide a protective device that can.

  Note that a dielectric material such as glass can be used for the dielectric layer. A printing process may be used for forming the dielectric layer and the gap.

  Another object is to insert a solid (preferably various piezoelectric materials having a piezo effect) into the gap or to enclose a gas (such as a rare gas) to prevent the ESD from hitting the electronic circuit. It is to provide.

  Another object of the present invention is to provide a method for manufacturing an overvoltage protection device for electronic circuits that is easy to manufacture and low cost.

  An overvoltage protection device for an electronic circuit, comprising a ceramic substrate, a buffer layer formed on the ceramic substrate, an inner electrode conductor layer formed on the buffer layer, and the inner electrode A dielectric layer formed on the conductor layer, an outer electrode conductor layer formed on the dielectric layer, and a protective layer formed on the outer electrode conductor layer, The outer electrode conductor layer, the dielectric layer, and the inner electrode conductor layer are penetrated and partially cut into the buffer layer to form a gap across the ceramic substrate. An overvoltage protection device for an electronic circuit, characterized in that the layer, the dielectric layer, and the inner electrode conductor layer are divided into two parts facing each other.

A method of manufacturing an overvoltage protection device for an electronic circuit, comprising: preparing a ceramic substrate; forming a buffer layer on the ceramic substrate; and forming an inner electrode conductor layer covering the buffer layer A step of forming a dielectric layer covering the inner electrode conductor layer, a step of forming an outer electrode conductor layer covering the dielectric layer, the outer electrode conductor layer, the dielectric layer, And forming a gap through the inner electrode conductor layer and across the ceramic substrate;
And manufacturing the overvoltage protection device for an electronic circuit, wherein the outer electrode conductor layer, the dielectric layer, and the inner electrode conductor layer are divided into two parts facing the gap. Method.

  A method of manufacturing an overvoltage protection device for an electronic circuit, comprising: preparing a ceramic substrate; forming a buffer layer on the ceramic substrate; and forming an inner electrode conductor layer covering the buffer layer A step of forming a dielectric layer covering the inner electrode conductor layer; and a plurality of electrodes spaced apart from each other along a longitudinal direction of the ceramic substrate, the outer electrode covering the dielectric layer Forming a conductor layer; and forming a gap across the ceramic substrate passing through the outer electrode conductor layer, the dielectric layer, and the inner electrode conductor layer, and An overvoltage protection for an electronic circuit, wherein the electrode conductor layer, the dielectric layer, and the inner electrode conductor layer are divided into two parts facing the gap Method of manufacturing location.

  That is, a multilayer structure comprising a buffer layer, an inner electrode conductor layer, a dielectric layer, and an outer electrode conductor layer is formed on a ceramic substrate, and after the entire structure is completed, a gap having an appropriate depth is formed in the cutting process. Is formed so as to cross the ceramic substrate, so that the two electrode layers of the inner electrode conductor layer and the outer electrode conductor layer are divided into two parts opposed to the transverse gap, and the dielectric The inner electrode conductor layer is separated from the outer electrode conductor layer by the body layer. Using this structure, a dielectric (preferably various piezoelectric materials having a piezo effect, such as quartz crystal, zinc oxide, etc.) is inserted in the gap or a gas (noble gas He, Ar, etc.) is enclosed, and a dielectric having an appropriate thickness By using layers, the entire structure functions as a protective element for ESD. Thereby, the entire structure can be used to protect against various electronic circuits.

  Also, after the electrode layer is formed, a plurality of spaced apart electrodes are obtained in the longitudinal direction of the substrate. Thereafter, a transverse gap is formed by a cutting process, and the plurality of spaced apart electrodes are opposed to the gap. Therefore, a matrix structure including a plurality of spaced apart electrodes arranged in the horizontal and vertical directions in a plane including the electrode layer is formed, thereby forming a protection device row for ESD.

  The distance between the inner and outer electrodes is determined by the thickness of the dielectric formed by the printing process. In order to avoid an inappropriate breakdown voltage due to an inappropriate gap distance, the difference between the upper electrode layer and the lower electrode layer can be controlled to be as small as possible.

The notable features of the present invention are as follows.
1. The gap width can be easily adjusted in the range of 10 to 30 μm by cutting with a diamond blade or laser trimming.
2. The gap width can be easily controlled in the range of 5 to 25 μm by the vertical multilayer structure throughout the printing process.
3. The extremely small gap width effectively lowers the breakdown voltage, thereby improving ESD protection for low voltage devices using a simple protection structure.

  As shown in FIGS. 2A to 2F, the method for manufacturing an overvoltage protection device for an electronic circuit according to the present invention includes the following steps.

1. A glass layer 22 is formed on the ceramic substrate 21. Here, the glass layer 22 is positioned at the center of the ceramic substrate 21 so that the edge of the glass layer does not contact the edge of the ceramic substrate. (See Figure 2A)
2. An inner electrode conductor layer 23 is formed so as to cover the glass layer 22, and one side of the inner electrode conductor layer 23 is connected to one side of the ceramic substrate 21, while the opposite side partially covers the upper surface of the glass layer 22. Cover. (See Figure 2B)
3. A dielectric layer 24, which is located just above the glass layer 22 and has the same size as the area of the glass layer 22 covering the inner electrode conductor layer 23, is formed, and one side of the dielectric layer 24 is one side of the glass layer 22. Connect with. (See Figure 2C)
4). An outer electrode conductor layer 25 covering the dielectric layer 24 is formed, and one side of the outer electrode conductor layer 25 is connected to the ceramic substrate 21 on the side opposite to the connection portion between the inner electrode conductor layer 23 and the ceramic substrate 21. While connected, the opposite side of the outer electrode conductor layer partially covers the top surface of the dielectric layer 24. (See Figure 2D)
5). A protective glass layer 26 is formed to cover the outer electrode conductor layer 25, and one side of the protective glass layer 26 is in contact with the dielectric layer 24. (See Figure 2E)
6). Finally, by a cutting process using a diamond blade or a laser trimming process, the ceramic substrate is cut out on the portion where the inner electrode conductor layer 23, the dielectric layer 24, and the outer electrode conductor layer 25 overlap. The transverse gap 3 penetrates the protective glass layer 26, the outer electrode conductor layer 25, the dielectric layer 24, and the inner electrode conductor layer 23, so that the five layers are opposed to each other with the gap therebetween. (See Figure 2F)
By using this structure, the thickness of the dielectric layer 24 inserted between the inner and outer electrode conductor layers functions as a discharge gap, so that the entire structure becomes an ESD protection device. Further, the inner electrode conductor layer 23 and the outer electrode conductor layer 25 face the first front electrode layer 231 and the second rear electrode layer 252 respectively facing the first rear electrode layer 232 by the transverse gap 3. Divided into a second front electrode layer 251. Thereafter, the gap between the first front electrode layer 231 and the first rear electrode layer 232 is filled by filling the gap with a piezoelectric material or a gas having a different property (for example, an inert gas such as He). ESD protection devices with different trigger voltages between the two front electrode layers 251 and the second rear electrode layer 252 are obtained.

  Referring to FIGS. 3 to 5, a method of manufacturing an overvoltage protection device for an electronic circuit according to another embodiment of the present invention includes the following steps.

  1. A ceramic substrate 4 is prepared.

  2. The buffer layer 41 is formed in the shape of a rectangular parallelepiped on the central portion of the ceramic substrate 4 so that the long side extends in the same direction as that of the ceramic substrate 4.

  3. It has the same length as the ceramic substrate 4 and has a U-shaped inner electrode conductor layer 42 as viewed from the short side of the ceramic substrate, covers the buffer layer 41, and extends in the longitudinal direction of the ceramic substrate. Both ends form steel pieces 421 and 422 that are thicker than the central part, respectively, which are positioned at both ends so as to straddle the buffer layer 41, are connected to the upper surface of the ceramic substrate 4, and extend in the short direction of the ceramic substrate. In other words, the flat surface 423 protruding outward is formed, and the inner electrode conductor layer 42 has a cross-like shape.

  4). A dielectric layer 43 is formed so as to cover the inner electrode conductor layer 42.

5). An outer electrode conductor layer 44 is formed so as to cover the dielectric layer 43. The outer electrode conductor layer 44 is made of a conductive material containing Pd or Pt, and partially covers the inner electrode conductor layer 42. A plurality of spaced apart electrodes are provided along the longitudinal direction of the ceramic substrate, and the top portions of the spaced apart electrodes are formed on both sides of the ceramic substrate in the short direction, and the dielectric layer 43, the inner electrode conductor layer 42, and the buffer layer 41 are positioned on both sides. As a result, the electrode pieces separated from each other are connected to 4A and 4B of the ceramic substrate 4, respectively. (See Figure 3)
6). Thereafter, a protective layer is formed so as to cover the electrode conductor layer 44.

  7. Finally, a transverse gap along the center of the structure that penetrates the outer electrode conductor layer 44, the dielectric layer 43, and the inner electrode conductor layer 42 by a cutting process using a diamond blade or a laser trimming process. 5 is formed, and the outer electrode conductor layer 44, the dielectric layer 43, and the inner electrode conductor layer 42 are opposed to the gap by partially cutting into the buffer layer 41 (hereinafter referred to as a first portion and a first portion). (Referred to as the second part). In particular, the outer electrode conductor layer 44 is symmetrically divided into electrodes 441, 442, 443, and 444 spaced apart from each other in the first portion and electrodes 44a, 44b, 44c, and 44d spaced apart from each other in the second portion.

  Using this structure obtained by the above-described process, the thickness of the dielectric layer 43 placed between the outer electrode conductor layer 44 and the inner electrode conductor layer 42 is controlled to be as thin as possible. Therefore, it can be made. Furthermore, by using different dielectric materials and filling the transverse gap 5 with solid or gas, the entire structure has different inductor and capacitance values, thereby different types of resistors, capacitors, or A complete ESD protection device can be obtained that protects the electronic circuit including the inductor.

  A protective device formed by a plurality of spaced apart electrodes arranged in a matrix can provide a plurality of pins for connection to a plurality of circuits when used on a circuit board. On the other hand, the steel pieces 421 and 422 formed at both ends of the inner electrode conductor layer 42 are used as ground terminals. By adopting the above method, the dielectric layer 42 that affects the characteristics of the resistance and the capacitance is controlled well, so that the conventional problems in which different protection circuits are individually connected to different circuits are corrected. By filling the gap 5 with a material to avoid a drop in breakdown voltage, the result is improved surge protection (ESD protection) and the stability of the protected electronic circuit.

  By using the steps for manufacturing the protective device described above, the electronic circuit is reliably protected from the surge voltage strike.

  Referring to FIG. 6, according to yet another embodiment of the present invention, a buffer layer 61, an inner electrode conductor layer 62, a dielectric layer 63, an outer electrode conductor layer 64, a protective layer 65, a first insulating layer. 66 and a second insulating layer 67 are continuously formed on the substrate. Depending on the cutting process, a transverse gap 68 divides each layer described above into two facing parts. By filling the gaps 68 with various gases and piezoelectric sensitive materials by the air discharge technique, a structure on the substrate having ESD protection can be obtained. At the same time, the inner electrode conductor layer 71, the outer electrode conductor layer 72, the dielectric layer 73, the protective layer 74, the first insulating layer 75, and the second insulating layer 76 are placed on the opposite surface of the substrate by the pressure film printing process. Formed, thereby obtaining a structure similar to the previous one and functioning as ESD protection. Thereafter, two electrodes 81 and 82 are provided outside the structure by an electroplating process, and an electrical connection is made between the upper and lower structures, further forming an overvoltage protection device for double-sided electronic circuits. The

  Specifically, as shown in FIG. 6, the ESD protection device includes a buffer layer 61 formed on the substrate, and an inner electrode conductor layer 62 that covers the buffer layer 61. The inner electrode conductor layer 62 is in contact with the substrate on one end side and the other end side across the buffer layer 61. The inner electrode conductor layer 62 has a thick film portion formed thicker than the other portions on one end side.

  Furthermore, a dielectric layer 63 is formed in a partial region on the inner electrode conductor layer 62 from the other end portion to the center portion of the inner electrode conductor layer 62. An outer electrode conductor layer 64 is formed so as to cover the dielectric layer 63. The outer electrode conductor layer 64 has a proximal end portion that is located on the other end side of the inner electrode conductor layer 62 and is in contact with the substrate, and the distal end portion is one end side of the inner electrode conductor layer 62. Is growing.

  On one end side of the inner electrode conductor layer 62, a first insulating layer 66 is formed in a region between the inner electrode conductor layer 62 and the tip of the outer electrode conductor layer 64. On the other hand, on the other end side of the inner electrode conductor layer 62, a second insulating layer 67 is formed in a region between the inner electrode conductor layer 62 and the base end portion of the outer electrode conductor layer 64. The first insulating layer 66 and the second insulating layer 67 prevent the inner electrode conductor layer 62 and the outer electrode conductor layer 64 from being in electrical contact, and fix the positions of the respective layers.

  In the center portion, a gap 68 is formed through the inner electrode conductor layer 62, the dielectric layer 63, and the outer electrode conductor layer 64 by a cutting process, and a solid (piezo effect) provided in the gap 68 is formed. And a protective layer 65 is provided on the surface so as to enclose these solids and gases.

  On the other hand, the back side also has an inner electrode conductor layer 71, an outer electrode conductor layer 72, and a dielectric layer 73 sandwiched between them, and a protective layer 74 is formed on the outermost surface. The inner electrode conductor layer 71 has a pressure film portion that is formed thicker than the other portions at one end portion and protrudes outward, and the other end portion extends along the substrate. On the other hand, the outer electrode conductor layer 72 has a base end portion that is located on the other end side of the inner electrode conductor layer 71 and comes into contact with the substrate. Extends to one end. On one end side of the inner electrode conductor layer 71, a first insulating layer 75 is formed in a region between the inner electrode conductor layer 71 and the distal end portion of the outer electrode conductor layer 72. On the other hand, on the other end side of the inner electrode conductor layer 71, a second insulating layer 76 is formed in a region between the inner electrode conductor layer 71 and the base end portion of the outer electrode conductor layer 72.

  Thus, the outer electrode conductor layer, the inner electrode conductor layer, and the protective layer may be formed on both surfaces of the ceramic substrate.

  In the embodiment shown in FIG. 6, the upper part of the substrate can act as an ESD protection device, while the lower part can act as an RC or EMI circuit, and therefore has two functional structures, eg, ESD. A multifunction device having a protection function and an RC circuit or a multifunction device having an ESD protection function and an EMI (Electromagnetic interference) circuit is realized.

  Since the resistors and capacitors arranged in a three-dimensional matrix as the whole structure serve as a multipurpose protection device applicable to all electronic circuits, the cost of circuit development is reduced. It meets the requirements of being lightweight, thin, short and compact, and is particularly suitable for high-frequency or high-performance electronic circuits.

  By using multiple dielectric and electrode building blocks together with gaps filled with certain materials, a variety of capacitors and resistors can be achieved to meet different requirements for overvoltage protection simply by changing the material that fills the gap. You can make structures that contain.

Schematic showing the structure of a conventional gap discharge device Discharge voltage suppression curve according to the prior art Plan and side views of the description of the production method according to the invention Plan and side views of the description of the production method according to the invention Plan and side views of the description of the production method according to the invention Plan and side views of the description of the production method according to the invention Plan and side views of the description of the production method according to the invention Plan and side views of the description of the production method according to the invention 3D exploded view of the production method according to the second embodiment of the present invention 3D assembly drawing of the second embodiment of the present invention Sectional view of the second embodiment of the present invention Sectional view of the third embodiment of the present invention

Explanation of symbols

10 PCB board,
11 circuit,
12a, 12b Discharge electrodes with sharp tips,
13 gap,
15 surge voltage,
16 Electrostatic discharge curve,
17 Curve limited to tolerance,
4,21 Ceramic substrate,
22 glass layers,
23, 62, 71 Inner electrode conductor layers,
24 dielectric layer,
25, 64, 72 outer electrode conductor layers,
26 protective glass layer,
3, 5, 68 transverse gap,
41, 61 Buffer layer,
42 inner electrode conductor layer,
421, 422 billets,
423 a flat surface protruding outside the electrode layer;
43, 63, 73 dielectric layers,
44 outer electrode conductor layer,
441, 442, 443, 444 Single electrode,
4A Upper side of the ceramic substrate,
4B The lower side of the ceramic substrate,
44a, 44b, 44c, 44d Single electrode,
65, 74 protective layer,
66, 75 first insulating layer,
67, 76 second insulating layer,
81, 82 External electrodes.

Claims (10)

An overvoltage protection device for electronic circuits,
A ceramic substrate;
A buffer layer formed on the ceramic substrate;
An inner electrode conductor layer formed on the buffer layer;
A dielectric layer formed on the inner electrode conductor layer;
An outer electrode conductor layer formed on the dielectric layer;
A protective layer formed on the outer electrode conductor layer;
Including
The outer electrode by passing through the outer electrode conductor layer, the dielectric layer, and the inner electrode conductor layer, partially cutting into the buffer layer and forming a gap across the ceramic substrate; An overvoltage protection device for an electronic circuit, wherein the conductor layer, the dielectric layer, and the inner electrode conductor layer are divided into two portions facing each other.   The overvoltage protection device for an electronic circuit according to claim 1, wherein the dielectric layer is a glass layer.   The overvoltage protection device for an electronic circuit according to claim 1, wherein the dielectric layer is made of a dielectric material.   The inner electrode conductor layer is formed with a plurality of spaced apart electrodes along the longitudinal direction of the ceramic substrate, and the electrodes are divided into two opposing portions by gaps extending in the longitudinal direction. The overvoltage protection device for an electronic circuit according to claim 1, wherein the overvoltage protection device is an electronic circuit.   The overvoltage protection device for an electronic circuit according to claim 1, wherein the inner electrode conductor layer has a steel piece for grounding at an end thereof.   The overvoltage protection device for an electronic circuit according to claim 1, wherein the inner electrode conductor layer has a U-shape.   2. The overvoltage protection device for an electronic circuit according to claim 1, wherein the outer electrode conductor layer, the inner electrode conductor layer, and the protective layer are formed on both surfaces of the ceramic substrate.   The buffer layer, the outer electrode conductor layer, the inner electrode conductor layer, and the protective layer have properties of a capacitor or an inductor, and function as an RC circuit or an EMI circuit together with their dielectric characteristics. The overvoltage protection device for an electronic circuit according to claim 1. A method of manufacturing an overvoltage protection device for an electronic circuit,
Preparing a ceramic substrate;
Forming a buffer layer on the ceramic substrate;
Forming an inner electrode conductor layer covering the buffer layer;
Forming a dielectric layer covering the inner electrode conductor layer;
Forming an outer electrode conductor layer covering the dielectric layer;
Forming a gap across the ceramic substrate passing through the outer electrode conductor layer, the dielectric layer, and the inner electrode conductor layer;
Including
A method of manufacturing an overvoltage protection device for an electronic circuit, wherein the outer electrode conductor layer, the dielectric layer, and the inner electrode conductor layer are divided into two portions facing the gap. A method of manufacturing an overvoltage protection device for an electronic circuit,
Preparing a ceramic substrate;
Forming a buffer layer on the ceramic substrate;
Forming an inner electrode conductor layer covering the buffer layer;
Forming a dielectric layer covering the inner electrode conductor layer;
A plurality of spaced apart electrodes along the longitudinal direction of the ceramic substrate;
Forming an outer electrode conductor layer covering the dielectric layer;
Forming a gap across the ceramic substrate passing through the outer electrode conductor layer, the dielectric layer, and the inner electrode conductor layer;
Including
A method of manufacturing an overvoltage protection device for an electronic circuit, wherein the outer electrode conductor layer, the dielectric layer, and the inner electrode conductor layer are divided into two portions facing the gap.