阅读说明：本技术 一种热保护型压敏电阻 (Thermal protection type piezoresistor ) 是由 常忆 李峰 钱朝勇 夏心俊 沈十林 韩乔磊 于 2020-06-02 设计创作，主要内容包括：本发明一种热保护型压敏电阻,包括外壳、压敏电阻和该压敏电阻的引线,所述的外壳为具有绝缘性的聚苯硫醚注塑成型；所述的压敏电阻和一陶瓷片式过温保护器紧密贴合串联,设在外壳内；在所述的压敏电阻和一陶瓷片式过温保护器之间,由绝缘导热灌封胶填充至外壳内压敏电阻和陶瓷片式过温保护器两者之间的间隙内,并包覆所述压敏电阻及陶瓷片式过温保护器。本发明压敏电阻与陶瓷片式过温保护器紧密贴合,并由灌封胶填充至两者之间的间隙中,可以最大效率地将压敏电阻击穿时产生的高热量传导至陶瓷片式过温保护器,最大程度地保护了电气线路,规避安全隐患；外壳优异的机械强度、耐高温、耐化学、难燃、热稳定性和电性能,可提高产品可靠性。(The invention relates to a thermal protection type piezoresistor, which comprises a shell, a piezoresistor and a lead of the piezoresistor, wherein the shell is formed by injection molding of polyphenylene sulfide with insulativity; the piezoresistor and a ceramic plate type over-temperature protector are closely attached and connected in series and are arranged in the shell; and an insulating heat-conducting pouring sealant is filled between the piezoresistor and the ceramic chip type over-temperature protector to a gap between the piezoresistor and the ceramic chip type over-temperature protector in the shell, and coats the piezoresistor and the ceramic chip type over-temperature protector. The piezoresistor and the ceramic chip type over-temperature protector are tightly attached, and the pouring sealant is filled in the gap between the piezoresistor and the ceramic chip type over-temperature protector, so that high heat generated when the piezoresistor is broken down can be transmitted to the ceramic chip type over-temperature protector at the maximum efficiency, an electric circuit is protected to the maximum extent, and potential safety hazards are avoided; the shell has excellent mechanical strength, high temperature resistance, chemical resistance, flame retardancy, thermal stability and electrical property, and can improve the reliability of products.)

1. A thermal protection type piezoresistor comprises a shell, an over-temperature protector, a piezoresistor and a lead of the piezoresistor, wherein the piezoresistor comprises a first metal electrode layer and a second metal electrode layer which can conduct heat and electricity,

the shell is made of engineering plastics with insulativity, high temperature resistance, corrosion resistance and excellent mechanical properties through injection molding;

the over-temperature protector is a ceramic wafer type over-temperature protector;

the varistor and the ceramic chip type over-temperature protector are tightly attached and connected in series and are arranged in the shell, the varistor and the ceramic chip type over-temperature protector are filled with insulating heat-conducting pouring sealant to the shell in a gap between the varistor and the ceramic chip type over-temperature protector, and the varistor and the ceramic chip type over-temperature protector are wrapped.

2. A thermally protected varistor according to claim 1,

the ceramic chip type over-temperature protector in the shell is tightly attached to one metal electrode layer of the piezoresistor;

the lead comprises a first lead, a second lead and a third lead, one end of the first lead is electrically connected with the first metal electrode layer, and the other end of the first lead is led out; one end of the second lead is electrically connected to the second metal electrode layer, and the other end of the second lead is led out; one electrode port of the ceramic chip type over-temperature protector is connected to the second metal electrode layer, one end of the third lead is electrically connected with the other electrode port of the ceramic chip type over-temperature protector, and the other end of the third lead is led out.

3. The thermal protection type varistor according to claim 1 or 2, wherein said ceramic sheet over-temperature protector is square, and has a fusing temperature of 100 ℃ to 250 ℃, and comprises a ceramic substrate and an upper cover, wherein the upper cover forms a space on the ceramic substrate, and a bonding pad on the ceramic substrate, a low-temperature alloy wire, a fusing aid on the low-temperature alloy wire, and a first electrode port and a second electrode port on two ends of the low-temperature alloy wire are sequentially disposed in the space.

4. A thermally protected varistor according to claim 3, wherein said ceramic substrate is made of alumina, aluminum nitride, zirconia and/or silicon carbide material.

5. A thermal protection varistor as claimed in claim 3, wherein said ceramic sheet overheat protector is square and is attached to a metal electrode layer of said varistor.

6. The thermal protection type varistor as claimed in claim 5, wherein said ceramic chip over-temperature protector has an electrode port welded to said second lead wire and electrically connected to said varistor at the same position as said second metal electrode layer.

7. The thermally protected varistor of claim 6, wherein said varistor is circular.

8. The thermal protection type varistor as claimed in claim 6, wherein said first, second and third leads of said varistor are directly led out in a straight line.

9. The thermal protection type varistor as claimed in claim 7, wherein said second lead wire is soldered to said second metal electrode layer of said varistor by a low temperature solder paste.

10. The thermal protection type varistor as claimed in claim 1, wherein said potting adhesive is epoxy potting adhesive, polyurethane heat-conducting potting adhesive or silicone potting adhesive.

11. The thermal protection type varistor according to claim 1, wherein said first, second and third leads are bare copper wires, tinned steel wires, tinned copper wires, silvered copper wires or nickelled copper wires.

12. The thermal protection varistor as claimed in claim 1, wherein said housing is injection molded from polyphenylene sulfide (PPS) having insulating properties.

Technical Field

The invention relates to the technical field of electrical circuits, in particular to a thermal protection type piezoresistor.

Background

The voltage-limiting protection device is a voltage-limiting protection device which is a piezoresistor with zinc oxide as a main component, is sensitive to voltage and is commonly used in various household appliances and electric circuits. However, due to aging problems occurring over time or multiple transient voltage impacts borne in the circuit, the piezoresistor generates heat and breaks down, and even fires cause potential safety hazards.

The existing thermal protection type piezoresistors also have many defects: the varistor can not break the circuit in time when the heat conduction is too slow after breakdown; the thermal protection type piezoresistor is too large in volume and cannot be applied to small integrated circuits, and the development of the market is limited. The thermal protection type piezoresistor commonly used in the market at present adopts a mechanical flicking device to break a temperature fuse so as to achieve the effect of breaking a circuit, but the structural design is more complex and the cost is higher.

Application No. 2017217621713 provides a thermally protected varistor comprising a varistor chip having a first conductive layer and a second conductive layer, a temperature fuse, and leads comprising a first lead, a second lead, and a third lead; one end of the first lead is connected to the first conductive layer, and the other end of the first lead is led out; the first end of the temperature fuse is led out as a second lead, and the second end of the temperature fuse is connected to the second conducting layer; one end of the third lead is connected to the second conductive layer, and the other end of the third lead is led out; the temperature fuse is an axial temperature fuse and is arranged close to the piezoresistor chip. When the chip of the piezoresistor is abnormal, the thermal protection type piezoresistor can more effectively and accurately transfer the heat generated by the chip of the piezoresistor to the temperature fuse, thereby shortening the time required by the temperature fuse to open the circuit; small volume, convenient installation, simple structure, easy manufacture and low cost.

Disclosure of Invention

The invention aims to manufacture a thermal protection type piezoresistor, has the characteristics of small volume, low cost, quick heat transfer and high reliability, and can be widely applied to various fields.

In order to meet the technical requirements, the invention adopts the following technical scheme:

a thermal protection type piezoresistor comprises a shell, an over-temperature protector, a piezoresistor and a lead of the piezoresistor, wherein the piezoresistor comprises a first metal electrode layer and a second metal electrode layer which can conduct heat and electricity,

the shell is made of engineering plastics with insulativity, high temperature resistance, corrosion resistance and excellent mechanical properties through injection molding;

the over-temperature protector is a ceramic wafer type over-temperature protector;

the varistor and the ceramic chip type over-temperature protector are tightly attached and connected in series and are arranged in the shell, the varistor and the ceramic chip type over-temperature protector are filled with insulating heat-conducting pouring sealant to the shell in a gap between the varistor and the ceramic chip type over-temperature protector, and the varistor and the ceramic chip type over-temperature protector are wrapped. Has compact structure and can ensure the sensitivity of heat conduction to the maximum extent.

On the basis of the scheme, the ceramic chip type over-temperature protector in the shell is tightly attached to one metal electrode layer of the piezoresistor;

the lead comprises a first lead, a second lead and a third lead, one end of the first lead is electrically connected with the first metal electrode layer, and the other end of the first lead is led out; one end of the second lead is electrically connected to the second metal electrode layer, and the other end of the second lead is led out; one electrode port of the ceramic chip type over-temperature protector is connected to the second metal electrode layer, one end of the third lead is electrically connected with the other electrode port of the ceramic chip type over-temperature protector, and the other end of the third lead is led out.

Furthermore, one end of the first lead is electrically connected with the first metal electrode layer, and the other end of the first lead is led out; and one end of the second lead is electrically connected with the electrode port II of the ceramic chip type over-temperature protector, and the other end of the second lead is led out.

The ceramic chip type over-temperature protector is square, the fusing temperature of the ceramic chip type over-temperature protector is between 100 ℃ and 250 ℃, the ceramic chip type over-temperature protector comprises a ceramic substrate and an upper cover, the upper cover covers a space formed on the ceramic substrate, and a bonding pad, a low-temperature alloy wire, an auxiliary fusing agent on the low-temperature alloy wire, and a first electrode port and a second electrode port at two ends of the low-temperature alloy wire are sequentially arranged in the space.

Further, the ceramic substrate is made of alumina, aluminum nitride, zirconia and/or silicon carbide materials.

The electrical connections involved in the present invention include, but are not limited to, conventional solder connections.

Preferably, the ceramic chip type over-temperature protector is square and clings to a metal electrode layer of the piezoresistor.

Preferably, one electrode port of the ceramic chip type over-temperature protector is welded with the second lead wire, and is electrically connected to the same position of the second metal electrode layer of the piezoresistor.

Preferably, the second lead and the ceramic chip type over-temperature protector are welded with each other and are electrically connected to the same position of the second metal electrode layer of the piezoresistor.

Preferably, the piezoresistor is circular.

Furthermore, the first lead, the second lead and the third lead are directly led out in a straight line.

Preferably, the second lead and the second metal electrode layer of the piezoresistor are welded by adopting low-temperature solder paste.

On the basis of the scheme, the pouring sealant is epoxy pouring sealant, polyurethane heat conduction pouring sealant or organic silicon pouring sealant, and when the thermal protection type voltage dependent resistor is in a breakdown condition, the surface of the product can be prevented from being cracked.

On the basis of the scheme, the first lead, the second lead and the third lead can be bare copper wires, tinned steel wires, tinned copper wires, silvered copper wires or nickelled copper wires.

On the basis of the scheme, the shell is obtained by injection molding of polyphenylene sulfide (PPS) with insulativity.

The invention has the beneficial effects that:

1. according to the thermal protection type piezoresistor, the piezoresistor is tightly attached to the ceramic chip type over-temperature protector, and the pouring sealant is filled in the gap between the piezoresistor and the ceramic chip type over-temperature protector, so that high heat generated when the piezoresistor is broken down can be efficiently conducted to the ceramic chip type over-temperature protector, an electric circuit is protected to the greatest extent, and potential safety hazards are avoided;

2. the housing of the thermal protection type piezoresistor has the characteristics of high mechanical strength, high temperature resistance, chemical resistance, flame retardancy, good thermal stability and excellent electrical property, can improve the reliability of the thermal protection type piezoresistor, and reduces the possibility of appearance cracking and burning of the product;

3. the thermal protection type piezoresistor has the advantages of simple structure, small volume, convenient installation in multi-field electrical circuits, simple manufacturing process, convenient batch production and low cost.

Drawings

FIG. 1 is a schematic structural diagram of an embodiment of the invention;

FIG. 2 is a schematic top view of a thermally protected varistor subassembly;

FIG. 3 is a schematic diagram of a thermally protected varistor subassembly without a second lead;

FIG. 4 is a schematic diagram of a ceramic wafer type over-temperature protector assembly;

FIG. 5 is a schematic view of an upper cover of the ceramic plate type over-temperature protector;

description of reference numerals:

1-a housing;

2-ceramic chip type over-temperature protector;

21-ceramic substrate;

22-bonding pad;

23-low temperature alloy wire;

24. 24' -electrode ports one, two;

25-fluxing agent;

26-upper cover;

3-piezoresistor;

31. 32-second, metal electrode layer of piezoresistor;

41. 42, 43-first, second, third leads;

and 5, soldering the tin contact at low temperature.

Detailed Description

The invention is further described with reference to the following examples and the accompanying drawings. It should be noted that the examples herein are merely illustrative of the present invention and do not represent specific limitations of the present invention.

As shown in fig. 1 and 2, a thermal protection type varistor is provided, which comprises a polyphenylene sulfide (PPS) injection molded housing 1 with insulation property, and is formed based on a conventional varistor 3, wherein the varistor has a first metal electrode layer 31 (not shown) and a second metal electrode layer 32 on two surfaces, and three leads, namely a first lead 41, a second lead 42 and a third lead 43, respectively, wherein one end of the first lead 41 is welded on the first metal electrode layer 31 of the varistor 3, and the other end is led out as a pin;

the right flank of the second metal electrode layer 32 of the varistor 3 is hugged closely at the back of the ceramic chip type over-temperature protector 2, as shown in fig. 2 and 3, the ceramic chip type over-temperature protector 2 comprises from bottom to top in sequence: ceramic substrate 21, bonding pad 22 (which may be disposed below ceramic substrate 21), low-temperature alloy wire 23, and fuse aid 25; the outline shape of an upper cover 26 is the same as or corresponding to that of the ceramic substrate 21, the upper cover is covered above the ceramic substrate 21, a certain space is formed between the upper cover and the ceramic substrate 21, and the welding pad 22, the low-temperature alloy wire 23 and the fusing assistant agent 25 are all arranged in the space; the second electrode port 24' of the ceramic chip type over-temperature protector 2 is welded with one end of the second lead 42 and is welded to the second metal electrode layer 32 of the piezoresistor 3; the first electrode port 24 of the ceramic sheet type over-temperature protector 2 is directly led out to the lower side surface of the piezoresistor 3 through the third lead 43 to be used as a pin.

As shown in fig. 3, a thermal protection varistor is provided, which is based on a conventional varistor 3 having a first metal electrode layer 31 and a second metal electrode layer 32 on both surfaces thereof. The two leads are respectively a first lead 41 and a third lead 43, wherein one end of the first lead 41 is welded on the first metal electrode layer of the piezoresistor 3, and the other end of the lead is led out to be used as a pin; the back of the ceramic chip type over-temperature protector 2 is tightly attached to the right side surface of the second metal electrode layer 32 of the piezoresistor 3, as shown in fig. 3 and 4, the first end 24' of the ceramic chip type over-temperature protector 2 and the second metal electrode layer 32 of the piezoresistor 3 are welded together through the low-temperature welding point 5, and the second end 24 of the ceramic chip type over-temperature protector 2 is taken as a third lead 43 and is directly led out to the lower side surface of the piezoresistor 3 to be taken as a pin.

The piezoresistor 3 and the ceramic chip type over-temperature protector 2 are arranged in the shell 1, and the potting adhesive coats the piezoresistor 3 and the ceramic chip type over-temperature protector 2 and is filled in a gap between the piezoresistor 3 and the ceramic chip type over-temperature protector 2. The first lead 41, the second lead 42, and the third lead 43 sequentially pass through the potting compound and the package 1 to extend to the outside.

In this embodiment, the potting adhesive is an epoxy potting adhesive, a polyurethane heat-conducting potting adhesive or an organic silicon potting adhesive, and can prevent the surface of the product from cracking under the breakdown condition of the thermal protection type varistor.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.