阅读说明：本技术 一种无外接电极的贴片式压敏电阻及其制备方法 (Surface-mounted piezoresistor without external electrode and preparation method thereof ) 是由 王建文 于 2020-07-08 设计创作，主要内容包括：本发明公开了一种无外接电极的贴片式压敏电阻及其制备方法,首先压制坯片,通过模具在坯片的底面一侧纵向压制贯穿坯片的隔离槽,得成型坯片；将成型坯片进行排塑、烧结处理,制得陶瓷基体；采用金属喷涂或真空溅射的方式,分别在陶瓷基体的上表面形成上电极、在上电极自靠近隔离槽一侧的侧面向底面延伸形成上电极延伸面以及在隔离槽的另一侧的陶瓷基体底面形成下电极；对陶瓷基体的侧面和隔离槽进行绝缘保护,形成贴片式压敏电阻元件。本发明采用一体化设计,无需外接电极,方便贴片机加工；制得的压敏电阻元件具有一致性好、结构可靠、散热充分的特点,克服了外接电极片的压敏电阻元件存在的尺寸一致性差、保护水平低、故障率高等问题。(The invention discloses a surface-mounted piezoresistor without an external electrode and a preparation method thereof, which comprises the following steps of firstly pressing a blank sheet, and longitudinally pressing an isolation groove penetrating through the blank sheet on one side of the bottom surface of the blank sheet through a mould to obtain a formed blank sheet; performing plastic removal and sintering treatment on the formed blank sheet to obtain a ceramic matrix; respectively forming an upper electrode on the upper surface of the ceramic substrate, forming an upper electrode extension surface by extending the upper electrode from the side surface close to one side of the isolation groove to the bottom surface, and forming a lower electrode on the bottom surface of the ceramic substrate on the other side of the isolation groove by adopting a metal spraying or vacuum sputtering mode; and insulating and protecting the side surface of the ceramic substrate and the isolation groove to form the patch type voltage dependent resistor element. The invention adopts an integrated design, does not need an external electrode and is convenient for processing by a chip mounter; the prepared voltage dependent resistor element has the characteristics of good consistency, reliable structure and sufficient heat dissipation, and the problems of poor size consistency, low protection level, high failure rate and the like of the voltage dependent resistor element externally connected with the electrode plate are solved.)

1. A preparation method of a patch type piezoresistor without an external electrode is characterized by comprising the following steps:

(1) pressing a blank sheet, and longitudinally pressing an isolation groove penetrating through the blank sheet on one side of the bottom surface of the blank sheet through a die to obtain a formed blank sheet;

(2) performing plastic removal and sintering treatment on the formed blank sheet to obtain a ceramic matrix;

(3) respectively forming an upper electrode on the upper surface of the ceramic substrate, forming an upper electrode extension surface by extending the upper electrode from the side surface close to one side of the isolation groove to the bottom surface, and forming a lower electrode on the bottom surface of the ceramic substrate on the other side of the isolation groove by adopting a metal spraying or vacuum sputtering mode;

(4) and insulating and protecting the side surface of the ceramic substrate and the isolation groove to form the patch type voltage dependent resistor element.

2. The method for manufacturing a patch type varistor without external electrodes according to claim 1, wherein in step (1), the blank is rectangular; pressing the blank sheet by a powder dry pressing forming machine, and longitudinally pressing an isolation groove penetrating through the blank sheet on one side of the bottom surface of the rectangular blank sheet by a die to obtain a formed blank sheet; and performing plastic removal and sintering treatment on the formed blank sheet to obtain the ceramic matrix.

3. The method for manufacturing a patch type varistor without external electrodes according to claim 1, wherein in step (1), the green sheet is in a strip shape; pressing the blank sheet by a powder dry pressing forming machine or an isostatic pressing machine, and longitudinally pressing an isolation groove penetrating through the blank sheet on one side of the bottom surface of the strip-shaped blank sheet by a mould to obtain a formed blank sheet; performing plastic removal and sintering treatment on the formed blank sheet to obtain a ceramic matrix; the longitudinal length of the ceramic base body is matched with the size of line protection surge.

4. The method for preparing the patch type varistor without the external electrode according to claim 2 or 3, wherein the metal spraying is silver paste spraying; the vacuum sputtering adopts vacuum copper sputtering.

5. The method for preparing a patch type varistor without external electrode according to claim 1, wherein the method comprisesIn the step (1), the ceramic powder with the gradient of 200V/mm is adopted to press a blank sheet, and the forming density of the blank sheet is 3.3g/cm³The plastic removing temperature is 380 ℃, the plastic removing time is 3 hours, and the ceramic matrix is prepared by sintering at 1200 ℃ for 2.5 hours.

6. A surface-mounted piezoresistor without an external electrode is characterized by comprising a ceramic substrate, wherein one side of the bottom surface of the ceramic substrate is longitudinally provided with an isolation groove which penetrates through the ceramic substrate; the upper surface of the ceramic substrate is fixedly provided with an upper electrode, and the upper electrode extends from the side surface close to one side of the isolation groove to the bottom surface to form an upper electrode extending surface; the other side of the isolation groove is provided with a lower electrode fixedly arranged on the bottom surface of the ceramic substrate.

7. The patch type varistor without external electrode according to claim 6, wherein said isolation trench has a cross-section of a semi-circular shape, a rectangular shape, a trapezoidal shape or a triangular shape.

8. The patch type varistor without external electrode according to claim 6, wherein said ceramic substrate has an arc, rectangular or triangular cross-section at a side thereof adjacent to said isolation trench.

9. The patch type varistor without external electrode according to claim 6, wherein said isolation trench has a trench width ranging from 1.5mm to 10mm, and a trench height greater than 0.5 mm.

10. The patch type varistor without external electrode according to claim 6, wherein the distance between the two sides of the isolation trench on the bottom surface of the ceramic substrate and the upper electrode extension surface and the lower electrode is greater than 0.5 mm.

Technical Field

The invention relates to the technical field of electronic ceramics, in particular to a patch type piezoresistor without an external electrode and a preparation method thereof.

Background

In recent years, the technology of processing the patches is widely applied to processing electronic circuit boards because of its high efficiency and reliability. However, although the varistor serving as the overvoltage front-end protection also has a multilayer patch element entering into commercial use, the conventional multilayer patch varistor can only be applied to an environment with a small surge capacity, and a pin element is still generally used for a surge larger than 600A. The board insertion efficiency of the pin element is then low. After 2016, some manufacturers adopt an external electrode plate method to process the piezoresistor into a patch element, but have many problems: (1) the reliability of the element after being welded for many times is poor; (2) due to the fact that the metal electrode plates are connected externally, consistency of the appearance size of the element is poor; (3) the bare metal electrode makes the component have to consider the insulation distance with the adjacent component when designing on the board, affects the plug-in density of the circuit board, and further causes difficulty for miniaturization design; (4) the superposition of the contact resistance and the inductance inductive reactance of the externally connected metal electrode plate can increase the residual voltage of the piezoresistor so as to reduce the protection level of the piezoresistor.

Disclosure of Invention

The invention solves the technical problem of providing a chip type varistor without an external electrode and a preparation method thereof, which adopt an integrated design, do not need the external electrode and facilitate the processing of a chip mounter; the prepared piezoresistor element has the characteristics of good consistency, reliable structure and sufficient heat dissipation.

The invention is realized by the following technical scheme:

a preparation method of a patch type piezoresistor without an external electrode comprises the following steps:

(1) pressing a blank sheet, and longitudinally pressing an isolation groove penetrating through the blank sheet on one side of the bottom surface of the blank sheet through a die to obtain a formed blank sheet;

(2) performing plastic removal and sintering treatment on the formed blank sheet to obtain a ceramic matrix;

(3) respectively forming an upper electrode on the upper surface of the ceramic substrate, forming an upper electrode extension surface by extending the upper electrode from the side surface close to one side of the isolation groove to the bottom surface, and forming a lower electrode on the bottom surface of the ceramic substrate on the other side of the isolation groove by adopting a metal spraying or vacuum sputtering mode;

(4) and insulating and protecting the side surface of the ceramic substrate and the isolation groove to form the patch type voltage dependent resistor element.

Further, the blank sheet in the step (1) is rectangular; pressing the blank sheet by a powder dry pressing forming machine, and longitudinally pressing an isolation groove penetrating through the blank sheet on one side of the bottom surface of the rectangular blank sheet by a die to obtain a formed blank sheet; and performing plastic removal and sintering treatment on the formed blank sheet to obtain the ceramic matrix.

Further, the blank sheet in the step (1) is in a strip shape; pressing the blank sheet by a powder dry pressing forming machine or an isostatic pressing machine, and longitudinally pressing an isolation groove penetrating through the blank sheet on one side of the bottom surface of the strip-shaped blank sheet by a mould to obtain a formed blank sheet; performing plastic removal and sintering treatment on the formed blank sheet to obtain a ceramic matrix; the longitudinal length of the ceramic base body is matched with the size of line protection surge.

Further, silver paste spraying is adopted for metal spraying; the vacuum sputtering adopts vacuum copper sputtering.

Further, in the step (1), the ceramic powder with the gradient of 200V/mm is adopted to press the blank sheet, and the forming density of the blank sheet is 3.3g/cm³The plastic removing temperature is 380 ℃, the plastic removing time is 3 hours, and the ceramic matrix is prepared by sintering at 1200 ℃ for 2.5 hours.

The invention also provides a surface-mounted piezoresistor without an external electrode, which comprises a ceramic matrix, wherein one side of the bottom surface of the ceramic matrix is longitudinally provided with an isolation groove penetrating through the ceramic matrix; the upper surface of the ceramic substrate is fixedly provided with an upper electrode, and the upper electrode extends from the side surface close to one side of the isolation groove to the bottom surface to form an upper electrode extending surface; the other side of the isolation groove is provided with a lower electrode fixedly arranged on the bottom surface of the ceramic substrate.

Furthermore, the cross section of the isolation groove is semicircular, rectangular, trapezoidal or triangular.

Furthermore, the cross section of the side surface of the ceramic substrate close to one side of the isolation groove is arc-shaped, rectangular or triangular.

Furthermore, the width range of the isolation groove is 1.5 mm-10 mm, and the height of the isolation groove is more than 0.5 mm.

Furthermore, the distance between two sides of the isolation groove on the bottom surface of the ceramic substrate and the upper electrode extension surface and the distance between two sides of the isolation groove and the lower electrode are respectively larger than 0.5 mm.

Compared with the prior art, the invention has the following beneficial technical effects:

the invention discloses a chip type piezoresistor without an external electrode and a preparation method thereof, which adopt an integrated design, do not need the external electrode and facilitate the processing of a chip mounter; longitudinally pressing an isolation groove penetrating through the blank sheet on one side of the bottom surface of the pressed blank sheet through a die to obtain a formed blank sheet; after the formed blank sheet is sintered into a ceramic matrix at high temperature, an upper electrode is respectively formed on the upper surface of the ceramic matrix, a lower electrode is formed on one side of the bottom surface of the ceramic matrix, which is far away from the isolation groove, and the upper electrode extends from the side surface of the ceramic matrix, which is close to the isolation groove, to the bottom surface to form an upper electrode extending surface in a metal spraying or vacuum sputtering mode; and then, insulating the side surface of the ceramic substrate and the isolation groove to obtain the surface mount type voltage dependent resistor element, wherein the prepared surface mount type voltage dependent resistor element has the characteristics of good consistency, reliable structure and sufficient heat dissipation, and can be widely applied to lightning protection and surge protection in electric power and electronic circuits.

According to the surface-mounted zinc oxide piezoresistor provided by the invention, the isolation groove penetrating through the ceramic substrate is longitudinally formed on the bottom surface of the ceramic substrate, and the isolation problem of the electrodes on the same side is solved through a special structural design. In order to prevent the surface breakdown of the same-side electrode, an isolation groove penetrating through the ceramic substrate is designed on one side of the ceramic substrate; an upper electrode on the upper surface of the ceramic substrate extends to an upper electrode extending surface from the side surface close to the isolation groove, and a layer of metal film is processed on one side of the bottom surface of the ceramic substrate far away from the isolation groove to serve as a lower electrode; at this time, the upper electrode extending surface and the lower electrode form two mounting welding electrodes of the chip component. The setting of isolation tank has pulled open the creepage distance of last electrode extension face and bottom electrode, prevents the short circuit between the electrode, has solved the isolation problem of homonymy electrode, has also overcome external electrode slice and has processed the size uniformity that piezo-resistor becomes patch element and poor, the protection level is low, the fault rate scheduling problem that exists.

Drawings

FIG. 1 is a schematic structural diagram of a rectangular patch type varistor without external electrodes according to the present invention;

fig. 2 is a schematic structural diagram of the strip-shaped patch type varistor without external electrodes.

Wherein, 1 is a basal body, 2 is an upper electrode, 3 is an upper electrode extension surface, 4 is a lower electrode, and 5 is an isolation groove.

Detailed Description

The present invention will now be described in further detail with reference to the attached drawings, which are illustrative, but not limiting, of the present invention.

Referring to fig. 1 and 2, a method for manufacturing a patch type varistor without an external electrode includes the following steps:

(1) pressing a blank sheet, and longitudinally pressing an isolation groove 5 penetrating through the blank sheet on one side of the bottom surface of the blank sheet through a die to obtain a formed blank sheet;

(2) performing plastic removal and sintering treatment on the formed blank sheet to obtain a ceramic matrix 1;

(3) forming an upper electrode 2 on the upper surface of the ceramic substrate 1, forming an upper electrode extension surface 3 by extending the upper electrode 2 from the side surface close to one side of the isolation groove 5 to the bottom surface, and forming a lower electrode 4 on the bottom surface of the ceramic substrate 1 on the other side of the isolation groove 5 by adopting a metal spraying or vacuum sputtering mode;

(4) and insulating and protecting the side surface of the ceramic substrate 1 and the isolation groove 5 to form the patch type voltage dependent resistor element.

The invention provides a preparation method of a patch type varistor without an external electrode, which comprises the steps of longitudinally pressing an isolation groove 5 penetrating through a blank sheet on one side of the bottom surface of the pressed blank sheet through a mould to obtain a formed blank sheet, sintering the formed blank sheet at high temperature to form a ceramic substrate 1, forming an electrode in a vacuum sputtering or metal spraying mode, and performing insulation treatment on the part except the electrode to obtain a patch type varistor element; after the pressed blank sheet is pressed, a strip-shaped boss is designed on a die, and an isolation groove 5 penetrating through the blank sheet is longitudinally pressed on the bottom surface of the pressed blank sheet by the die; the creepage distance between the upper electrode 2 and the lower electrode 4 is pulled open by the isolation groove 5, short circuit between the electrodes is prevented, the isolation problem of the electrodes on the same side is solved, and the problems of poor size consistency, low protection level, high failure rate and the like existing in the process of processing the piezoresistor into a patch element by an external electrode plate are also solved.

Specifically, a blank sheet is pressed by a powder dry pressing forming machine or an isostatic pressing machine, and the blank sheet can be rectangular or strip-shaped; when the ceramic powder is dry-pressed and molded by the powder dry-pressing molding machine, the ceramic powder can be molded at one time, the external dimension of the element is accurate, and the consistency is good. Fig. 1 is a schematic structural diagram of a rectangular patch varistor without external electrodes according to the present invention. Fig. 2 is a schematic structural diagram of the strip-shaped patch varistor without external electrodes according to the present invention. When the strip-shaped blank sheet is pressed by a powder dry pressing forming machine or an isostatic pressing machine, the blank sheet can be cut into required sizes according to parameter requirements; because the surge passing capability of the piezoresistor element is in direct proportion to the electrode area of the piezoresistor element, the sectional area passing the surge can be controlled by controlling the cutting width, so that one set of die can adapt to different surge requirements. Therefore, after the ceramic base body is manufactured, the longitudinal length of the ceramic base body 1 is cut out by a cutting machine according to the size of the line protection surge, and the longitudinal length of the ceramic base body 1 is matched with the size of the line protection surge. The invention discloses a method for controlling electrical performance parameters of a patch type piezoresistor, which comprises the following steps: the voltage-dependent voltage is controlled by the thickness of the ceramic matrix 1 and the gradient of the ceramic powder together; the current capacity of the element is controlled by adjusting the areas of the upper and lower electrodes 2 and 4 and the upper and lower end surfaces of the ceramic substrate 1.

In the step (4), the side surface of the ceramic substrate 1 and the isolation groove 5 are subjected to insulation protection, an insulation coating is sprayed on three side surfaces of the ceramic substrate 1 except the side surface on which the upper electrode 2 is formed and the isolation groove 5, and the surface-mount varistor element is subjected to insulation treatment; the insulating coating can be glass glaze, insulating paint, three-proofing paint, and can also be thermal-shaping insulating materials such as phenolic aldehyde, epoxy and the like.

Further, the blank sheet in the step (1) is rectangular; pressing the blank sheet by a powder dry pressing forming machine, and longitudinally pressing an isolation groove 5 penetrating through the blank sheet on one side of the bottom surface of the rectangular blank sheet by a die to obtain a formed blank sheet; and performing plastic removal and sintering treatment on the formed blank sheet to obtain the ceramic matrix 1.

Further, the blank sheet in the step (1) is in a strip shape; pressing the blank sheet by a powder dry pressing forming machine or an isostatic pressing machine, and longitudinally pressing an isolation groove 5 penetrating through the blank sheet on one side of the bottom surface of the strip-shaped blank sheet by a mould to obtain a formed blank sheet; performing plastic removal and sintering treatment on the formed blank sheet to obtain a ceramic matrix 1; specifically, fig. 2 is a schematic structural diagram of the strip-shaped patch varistor without external electrodes according to the present invention. The longitudinal length of the ceramic base body 1 is matched with the size of line protection surge. The ceramic base body 1 can be cut into a desired size according to parameters, and the surge passing capacity of the piezoresistor element is in direct proportion to the electrode area of the piezoresistor element, so that the sectional area of the piezoresistor element passing the surge can be controlled by controlling the cutting width, and a set of die can adapt to different surge requirements.

Further, silver paste spraying is adopted for metal spraying; the vacuum sputtering adopts vacuum copper sputtering. Specifically, the thickness of the metal film during vacuum copper sputtering is more than 5 μm.

Further, in the step (1), the ceramic powder with the gradient of 200V/mm is adopted to press the blank sheet, and the forming density of the blank sheet is 3.3g/cm³The plastic discharging temperature is 380 ℃, the plastic discharging time is 3 hours, and the ceramic matrix 1 is prepared by sintering at 1200 ℃ for 2.5 hours.

Specifically, the voltage-dependent voltage V1mA of the chip-type varistor element of the invention is adjusted by the porcelain gradient C and the thickness d of the porcelain. When the ceramic powder with the gradient of 200V/mm is used for manufacturing the ceramic chip, the thickness d of the ceramic chip is V1 mA/C; when the thickness d is required, the gradient C of the porcelain powder can be adjusted to obtain the expected voltage-dependent voltage V1mA, wherein V1mA is d x V1 mA.