CN113192713B

CN113192713B - Thermal protection piezoresistor

Info

Publication number: CN113192713B
Application number: CN202110460567.7A
Authority: CN
Inventors: 叶林龙; 黄绍芬; 杨柳; 蔡德惠; 李洁
Original assignee: Guangxi New Future Information Industry Co ltd
Current assignee: Guangxi New Future Information Industry Co ltd
Priority date: 2021-04-27
Filing date: 2021-04-27
Publication date: 2023-05-23
Anticipated expiration: 2041-04-27
Also published as: CN113192713A

Abstract

The invention discloses a thermal protection piezoresistor, which comprises a piezoresistor chip, a first metal conductor, a second metal conductor and a thermal fusing conductor, wherein the components are encapsulated by epoxy resin, and the thermal protection piezoresistor is characterized in that: the front of the piezoresistor chip is adhered with an insulating block with a groove, the groove faces the piezoresistor chip, the thermal fusing conductor is welded on the piezoresistor chip, the welding point is positioned in the groove, the thermal fusing conductor is bent and extends to the upper surface of the insulating block to be welded with the first metal conductor, and the back of the piezoresistor chip is welded with the second metal conductor. When the piezoresistor is impacted by high current and the temperature of the piezoresistor ceramic chip reaches a threshold value, the thermal fusing conductor melts to disconnect the loop, so that the piezoresistor is prevented from firing due to high temperature, and other electronic elements in the loop are protected from damage.

Description

Thermal protection piezoresistor

Technical Field

The invention relates to a thermal protection piezoresistor, and belongs to the field of electronic components.

Background

The varistor is an electronic component capable of suppressing transient overvoltage and discharging surge current. When surge current or overvoltage occurs in the loop, the piezoresistor is converted into an operating state, but the temperature of the piezoresistor body is increased. The epoxy resin material used for the surface encapsulation of the piezoresistor is a temperature-resistant, insulating and moistureproof material, but the epoxy resin material still has the possibility of igniting and burning at high temperature, and other peripheral electronic elements are ignited, so that larger loss is caused. Thus, a varistor with a thermal protection function has been developed.

The thermal protection piezoresistor in the current market is generally designed by adopting the principle that a thermal fuse is fused at high temperature to disconnect an element, but the fusing success rate is different, and the production process is complicated, so that the thermal protection piezoresistor is not beneficial to automatic and large-scale production.

Disclosure of Invention

The invention aims to solve the technical problem of providing a thermal protection piezoresistor, which solves the defects of unstable fusing success rate and complex production process of the traditional piezoresistor.

In order to solve the problems, the following technical scheme is adopted: the utility model provides a thermal protection piezo-resistor, includes the piezo-resistor chip, first metal conductor and second metal conductor, thermal fuse conductor, the positive bonding of piezo-resistor chip has the insulating piece of taking the recess, and the recess is towards the piezo-resistor chip, and thermal fuse conductor welds on the piezo-resistor chip, and the welding point is located the recess, and thermal fuse conductor extends to the insulating piece upper surface through bending, and with first metal conductor welding together, piezo-resistor chip reverse side welding has the second metal conductor.

The insulating block is made of high-temperature resistant insulating materials such as ceramic or high polymer materials.

And the thermal fusing conductor adopts a soldering wire with the melting point not exceeding the thermal safety threshold of the piezoresistor.

The thermal fusing conductor adopts a soldering wire with a fusing agent in the interior and a melting temperature of 180 ℃,

and the welding points of the piezoresistor chip and the thermal fuse conductor, the welding points of the thermal fuse conductor and the insulating block and the gaps of the insulating block are filled and covered by insulating hot melt adhesive, and the melting point of the insulating hot melt adhesive is lower than that of the thermal fuse conductor.

The melting point of the insulating hot melt adhesive is 20-30 ℃ lower than that of the thermal fusing conductor.

The thermal fusing conductor on the upper surface of the insulating block is welded with a third metal conductor.

When the varistor is in normal operation, the element body temperature does not reach the fusing temperature of the element, and the varistor is in a high-resistance state; when surge current occurs, the piezoresistor is conducted to start to drain the surge current, the element body starts to heat, when the temperature reaches the fusing temperature of the element, the soldering wire near the welding point is melted, and the liquid soldering wire alloy liquid automatically gathers to the welding point on the piezoresistor chip under the action of surface tension, so that the connection between the first metal conductor and the element body is disconnected to form an open circuit, the piezoresistor is disconnected from a circuit, the temperature is prevented from continuously rising, and no fire accident is ensured.

Drawings

FIG. 1 is a schematic diagram of the present invention;

fig. 2 is a schematic view of an embodiment of the present invention with a third metal conductor.

Reference numerals illustrate: the voltage-dependent resistor chip 1, a first metal conductor 2, a second metal conductor 3, a thermal fuse conductor 4, an insulating block 5, a groove 6 and a third metal conductor 7.

Detailed Description

The invention is further described below with reference to examples.

As shown in fig. 1, a thermal protection varistor comprises a varistor chip 1, a first metal conductor 2, a second metal conductor 3 and a thermal fusing conductor 4, wherein any one surface of the varistor chip 1 is a front surface, an insulating block 5 with a groove 6 is bonded on the front surface, the groove 6 faces the varistor chip 1, the thermal fusing conductor 4 is welded on the varistor chip 1, the welding point is positioned in the groove 6, the thermal fusing conductor 4 extends to the surface of the insulating block 5 through bending and is welded with the first metal conductor 2, the other surface of the varistor chip 1 is a reverse surface, and the reverse surface is welded with the second metal conductor 3. The insulating block 5 is made of high-temperature resistant insulating materials such as ceramic or high polymer materials. The thermal fusing conductor 4 is a soldering wire with a melting point not exceeding the thermal safety threshold of the piezoresistor. The thermal fusing conductor 4 adopts a soldering wire with a fusing agent in the melting temperature of 180 ℃, all welding spots on the front surface of the piezoresistor chip 1 are filled and covered by insulating thermal fusing adhesive, and the melting point of the insulating thermal fusing adhesive is 20-30 ℃ lower than that of the thermal fusing conductor 4. After the above steps are completed, the varistor chip 1, the first metal conductor 2, the second metal conductor 3 and the thermal-fusing conductor 4 are encapsulated by using epoxy resin, and the curing temperature of the epoxy resin is 140 ℃.

As shown in fig. 2, the thermal fuse conductor 4 on the upper surface of the insulating block 5 is also soldered with a third metal conductor 7 as a signal line. The third metal conductor 7 is connected with alarm equipment such as sound, light, electricity and the like, so that the piezoresistor can give out an alarm after failure.

The application method of the invention comprises the following steps: when the access circuit works normally, the piezoresistor is in a high-resistance state, the temperature on the piezoresistor is low, and the fusing mechanism of the element cannot be triggered. When the temperature of the varistor is raised under the condition of continuous abnormal overvoltage or other abnormal conditions, the insulating hot melt adhesive is melted into a liquid state in a first step, and when the temperature is continuously raised, the thermal fuse conductor 4 is melted into a liquid state and is gathered near a welding point on the front surface of the varistor chip 1 under the action of surface tension, and the liquid insulating hot melt adhesive is filled into the position of the original thermal fuse conductor 4, so that the connection between the first metal conductor 2 and the varistor chip 1 is disconnected, and the further temperature rise of the element is prevented, thereby achieving the purpose of preventing the ignition.

Claims

1. The utility model provides a thermal protection piezo-resistor, includes the piezo-resistor chip, first metal conductor and second metal conductor, thermal fuse conductor, and above-mentioned part is enveloped with epoxy, its characterized in that: the front surface of the piezoresistor chip is adhered with an insulating block with a groove, the groove faces the piezoresistor chip, a thermal fusing conductor is welded on the piezoresistor chip, the welding point is positioned in the groove, the thermal fusing conductor is bent and extends to the upper surface of the insulating block to be welded with a first metal conductor, and the back surface of the piezoresistor chip is welded with a second metal conductor; the thermal fusing conductor adopts a soldering wire containing fluxing agent and having a melting temperature of 180 ℃; the welding point of the piezoresistor chip and the thermal fuse conductor, the welding point of the thermal fuse conductor and the insulating block and the gap of the insulating block are filled and covered by insulating hot melt adhesive, and the melting point of the insulating hot melt adhesive is lower than that of the thermal fuse conductor; the melting point of the insulating hot melt adhesive is 20-30 ℃ lower than that of the thermal fusing conductor; the thermal fusing conductor on the upper surface of the insulating block is welded with a third metal conductor.

2. A thermal protection varistor as claimed in claim 1, wherein: the insulating block is made of high-temperature-resistant ceramic or high-molecular material.

3. A thermal protection varistor as claimed in claim 2, wherein: and the thermal fusing conductor adopts a soldering wire with the melting point not exceeding the thermal safety threshold of the piezoresistor.