CN113192713A

CN113192713A - Thermal protection piezoresistor

Info

Publication number: CN113192713A
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: 2021-07-30
Anticipated expiration: 2041-04-27
Also published as: CN113192713B

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 parts are encapsulated by epoxy resin, and the thermal protection piezoresistor is characterized in that: the front side of the piezoresistor chip is bonded with an insulating block with a groove, the groove faces the piezoresistor chip, the thermal fuse conductor is welded on the piezoresistor chip, the welding point is located in the groove, the thermal fuse conductor extends to the upper surface of the insulating block through bending and is welded with the first metal conductor, and the back side of the piezoresistor chip is welded with the second metal conductor. When the piezoresistor is impacted by heavy current and the temperature of the piezoresistor ceramic chip is raised to reach a threshold value, the thermal fuse conductor is melted to disconnect the loop, so that the piezoresistor is prevented from being ignited due to high temperature, and other electronic elements in the loop are protected from being damaged.

Description

Thermal protection piezoresistor

Technical Field

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

Background

A varistor is an electronic component that suppresses transient overvoltage and discharges surge current. When a surge current or an overvoltage occurs in the circuit, the varistor will switch to the operating state, but at the same time the temperature of the varistor body will increase. Although the epoxy resin material used for surface encapsulation of the piezoresistor is a temperature-resistant, insulating and moisture-proof material, the epoxy resin material still has the possibility of igniting and burning at high temperature, and igniting other peripheral electronic components, thereby causing larger loss. Therefore, a varistor with a thermal protection function has been produced.

Thermal protection piezoresistors in the market at present are generally designed by adopting the principle that a thermal fuse is fused at high temperature to break an element, but the fusing success rate is different, and the procedures in production are complicated, so that the automatic and large-scale production is not facilitated.

Disclosure of Invention

The invention aims to solve the technical problem of providing a thermal protection voltage dependent resistor, and solves the defects of unstable fusing success rate and complex production process of the conventional voltage dependent resistor.

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 metallic conductor and second metallic conductor, the hot-melt conductor, the positive insulating block that has the recess that bonds of piezo-resistor chip, the recess is towards the piezo-resistor chip, and the hot-melt conductor welding is on the piezo-resistor chip, and the welding point is located the recess, and the hot-melt conductor extends to the insulating block upper surface through bending, and is in the same place with the welding of first metallic conductor, and the welding of piezo-resistor chip reverse side has the second metallic conductor.

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

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

The thermal fusing conductor adopts a soldering wire which contains a fluxing agent and has a melting temperature of 180 ℃,

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

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

And a third metal conductor is welded on the thermal fuse conductor on the upper surface of the insulating block.

When the voltage-sensitive resistor works normally, the temperature of the element body cannot reach the fusing temperature of the element, and the voltage-sensitive resistor is in a high-resistance state; when surge current flows, the piezoresistor is conducted to dredge the surge current, the element body begins to heat up, when the temperature reaches the fusing temperature of the element, a soldering wire near a welding point is melted, and liquid welding wire alloy liquid is automatically collected to the welding point on the piezoresistor chip under the action of surface tension, so that the first metal conductor is disconnected with the element body to form an open circuit, the piezoresistor is disconnected from a circuit, the temperature is prevented from continuously rising, and the firing accident is avoided.

Drawings

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

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

The reference numbers illustrate: the chip comprises a piezoresistor 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 present invention will be further described with reference to the following examples.

As shown in fig. 1, a thermal protection piezoresistor, including piezoresistor chip 1, first metal conductor 2 and second metal conductor 3, thermal link conductor 4, arbitrary one side of piezoresistor chip 1 is the front, and positive adhesive tape groove 6's collets 5, and recess 6 are towards piezoresistor chip 1, and thermal link conductor 4 welds on piezoresistor chip 1, and the welding point is located recess 6, and thermal link conductor 4 extends to collets 5 surfaces through bending, and together with first metal conductor 2 welding, 1 another side of piezoresistor chip is the reverse side, and the reverse side welding has second metal conductor 3. The insulating block 5 is made of high-temperature-resistant insulating materials such as ceramics or high polymer materials. The thermal fusing conductor 4 adopts a soldering welding wire with the melting point not exceeding the thermal safety threshold of the piezoresistor. The thermal fuse conductor 4 is a soldering wire containing a fluxing agent and having a melting temperature of 180 ℃, all welding points on the front surface of the piezoresistor chip 1, gaps between the thermal fuse conductor 4 and the insulating blocks 5 are filled and covered with insulating hot melt adhesive, and the melting point of the insulating hot melt adhesive is 20-30 ℃ lower than that of the thermal fuse 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 fuse conductor 4 are encapsulated with an 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 further soldered with a third metal conductor 7 as a signal line. The third metal conductor 7 is connected with sound, light, electricity and other alarm devices, so that the piezoresistor can give out a warning after failure.

The use method of the invention comprises the following steps: when the access circuit normally works, the voltage dependent resistor is in a high-resistance state, the temperature on the voltage dependent resistor is low, and a fusing mechanism of an element cannot be triggered. When the varistor leads to temperature rise under continuous abnormal overvoltage or other abnormal conditions, the insulating hot melt adhesive is firstly further melted into liquid, when the temperature continues to rise, the thermal fuse conductor 4 is melted into liquid and is gathered near a welding point on the front surface of the varistor chip 1 under the action of surface tension, 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, the further temperature rise of the element is prevented, and the purpose of preventing fire is achieved.

Claims

1. A thermally protected varistor comprising a varistor chip, first and second metal conductors, and a thermally fused conductor, said components being encapsulated with an epoxy resin, characterized in that: the front side of the piezoresistor chip is bonded with an insulating block with a groove, the groove faces the piezoresistor chip, the thermal fuse conductor is welded on the piezoresistor chip, the welding point is located in the groove, the thermal fuse conductor extends to the upper surface of the insulating block through bending and is welded with the first metal conductor, and the back side of the piezoresistor chip is welded with the second metal conductor.

2. A thermally protected varistor according to claim 1, wherein: the insulating block is made of high-temperature-resistant insulating materials such as ceramics or high polymer materials.

3. A thermally protected varistor according to claim 2, wherein: the thermal fusing conductor adopts a soldering welding wire with a melting point not exceeding the thermal safety threshold of the piezoresistor.

4. A thermally protected varistor according to claim 3, wherein: the thermal fusing conductor adopts a soldering wire which contains a fluxing agent and has a melting temperature of 180 ℃.

5. A thermally protected varistor according to claim 4, wherein: the welding points of the piezoresistor chip and the thermal fusing conductor, the welding points of the thermal fusing conductor and the insulating block and the gaps of the insulating block are filled and covered with insulating hot melt adhesive, and the melting point of the insulating hot melt adhesive is lower than that of the thermal fusing conductor.

6. A thermally protected varistor according to claim 5, wherein: the melting point of the insulating hot melt adhesive is 20-30 ℃ lower than that of the thermal fuse conductor.

7. A thermally protected varistor according to claim 6, wherein: and a third metal conductor is welded on the thermal fuse conductor on the upper surface of the insulating block.