CN211125220U

CN211125220U - Intrinsic safety piezoresistor

Info

Publication number: CN211125220U
Application number: CN201921447743.8U
Authority: CN
Inventors: 沈朝阳
Original assignee: Shenzhen Jinyang Electronic Co ltd
Current assignee: Shenzhen Jinyang Electronic Co ltd
Priority date: 2019-09-02
Filing date: 2019-09-02
Publication date: 2020-07-28
Anticipated expiration: 2029-09-02

Abstract

The utility model discloses an this ampere of piezo-resistor, this ampere of piezo-resistor includes: the voltage-sensitive resistor comprises a voltage-sensitive resistor, an insulating substrate welded with the voltage-sensitive resistor, a current fuse arranged on the insulating substrate, a plurality of leads respectively welded on the voltage-sensitive resistor and the insulating substrate, and a packaging layer arranged on the outer side of the voltage-sensitive resistor. The utility model provides an this ampere of piezo-resistor not only can break off the trouble pressure-sensitive rapidly when normal atmospheric temperature heavy current, also can make piezo-resistor reach the effect of this ampere of protection with less current breaking trouble pressure-sensitive when pressure-sensitive trouble high temperature moreover.

Description

Intrinsic safety piezoresistor

Technical Field

The utility model relates to a resistance field especially relates to an intrinsic safe piezo-resistor.

Background

The voltage dependent resistor is a nonlinear overvoltage protection device, and absorbs surge voltage or spike pulse in a circuit to provide overvoltage protection for a post-stage circuit. The piezoresistor can cause aging failure of the piezoresistor in the process of frequently absorbing surge voltage and spike voltage, and the secondary disaster caused thereby can cause huge economic loss.

One of the manifestations of varistor failure is deterioration. After the piezoresistor bears the harsh lightning stroke, the leakage current is continuously increased and enlarged in a long time, and when the generated heat is continuously accumulated, the temperature rise of the piezoresistor is very high, and the piezoresistor is exploded and burnt at a certain critical point.

The second performance is that the fluctuation range of the power frequency voltage is underestimated, and the varistor is burnt out due to temperature rise caused by continuous long-time work under the condition of higher power frequency voltage. Or because of considering the protection effect on the rear-stage circuit, the product with lower voltage-sensitive voltage is selected to cause the over-high relative power frequency voltage, and the voltage-sensitive temperature rise is burnt out when the working time is longer.

The third is that transient peaks of shorter duration instantaneously perforate the pressure sensitive layer.

In summary, the process of damaging the piezoresistor is accompanied by large current and high temperature, and in order to avoid secondary disasters in the process of damaging the piezoresistor, a fuse sensitive to current or a thermal fuse sensitive to temperature is generally assisted to disconnect the damaged piezoresistor in practical application occasions, so that the probability of causing the secondary disasters in the process of damaging the piezoresistor is reduced. However, the two schemes always fail to completely reduce the probability of secondary disaster in the damage process of the piezoresistor or pay higher cost price due to the process reasons of type selection and assembly of the current fuse or production, assembly and use of the temperature fuse and the like.

Therefore, the problem that the fault voltage-sensitive is disconnected not only at normal temperature and abnormal large current, but also at high temperature of the voltage-sensitive fault and with smaller current needs to be solved, so that intrinsic safety protection of the piezoresistor is realized.

SUMMERY OF THE UTILITY MODEL

The utility model provides an this ampere of piezo-resistor not only can break off the trouble rapidly when normal atmospheric temperature unusual heavy current is pressure-sensitive, also can make piezo-resistor reach the effect of this ampere of protection with less current break-off trouble pressure-sensitive when piezo-resistor trouble high temperature moreover.

In order to achieve the above object, the present invention provides an intrinsically safe varistor comprising: the voltage-sensitive resistor comprises a voltage-sensitive resistor, an insulating substrate welded with the voltage-sensitive resistor, a current fuse arranged on the insulating substrate, a plurality of leads respectively welded on the voltage-sensitive resistor and the insulating substrate, and a packaging layer arranged on the outer side of the voltage-sensitive resistor.

Furthermore, the piezoresistor comprises a first welding surface and a second welding surface opposite to the first welding surface, wherein a first welding point is arranged at the center of the first welding surface, and a second welding point is arranged at the center of the second welding surface.

Furthermore, a round hole is formed in the center of the insulating substrate, a layer of weldable electrode is arranged on the periphery of the round hole, and the substrate is welded with the second welding point through the electrode.

Furthermore, the current fuses are arranged on the other surface of the insulating substrate far away from the piezoresistor, and one or more current fuses are respectively unfolded by taking the second welding points as centers.

Furthermore, the insulating substrate is provided with a third welding point and a fourth welding point on the left side, the right side or the upper side and the lower side of the second welding point.

Furthermore, the lead wires include a first lead wire soldered to the first solder joint, a second lead wire soldered to the second solder joint, a third lead wire soldered to the third solder joint, and a fourth lead wire soldered to the fourth solder joint, wherein a soldering end of the lead wires is located inside the package layer, and a free end of the lead wires is exposed outside.

Furthermore, the packaging layer wraps the piezoresistor, the insulating substrate, the current fuse and the welding end of the lead wire, so that the free end of the lead wire is exposed outside.

Furthermore, the third welding point, the fourth welding point and the second welding point are connected through the current fuse.

Preferably, the current fuse is a positive temperature coefficient fuse.

Compared with the prior art, the utility model provides an this ampere of piezo-resistor not only can break off the trouble pressure-sensitive rapidly when normal atmospheric temperature unusual heavy current, also can be with less current break-off trouble pressure-sensitive when pressure-sensitive trouble high temperature moreover, realizes this ampere of protecting effect.

Drawings

Fig. 1 is a schematic side view of a varistor according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a front structure of a varistor according to an embodiment of the present invention;

fig. 3 is a schematic diagram of a back side structure of a varistor according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of the insulating substrate in FIG. 2;

fig. 5 is an exemplary application circuit diagram according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Please refer to fig. 1 and fig. 2 in combination, for an intrinsic safety varistor according to an embodiment of the present invention, the intrinsic safety varistor 10 includes: the varistor 11, the insulating substrate 13 welded with the varistor, the current fuse printed on the insulating substrate, the plurality of leads 17 welded to the varistor and the insulating substrate, and the encapsulating layer 19 provided on the outer side of the varistor.

Referring to fig. 2 and fig. 3, the varistor 11 includes a first bonding surface 111, a second bonding surface 112 opposite to the first bonding surface, a first bonding point 113 at the center of the first bonding surface, and a second bonding point 114 at the center of the second bonding surface. The center of the insulating substrate 13 is provided with a circular hole, a layer of weldable electrode is printed on the periphery of the circular hole, the insulating substrate 13 is welded with the second welding point 114 through the electrode, and the insulating substrate 13 and the second welding surface 112 are attached and welded together through a second lead 172, so that the coupling temperature of the piezoresistor 11 can be sensed. A third solder joint 131 and a fourth solder joint 132 are located on either side of the second solder joint 114. The lead 17 includes a first lead 171 bonded to the first bonding pad 113, a second lead 172 bonded to the second bonding pad 114, a third lead 173 bonded to the third bonding pad 131, and a fourth lead 174 bonded to the fourth bonding pad 132, wherein the bonding end of the lead 17 is located inside the package layer 19, and the free end is exposed. The packaging layer 19 wraps the piezoresistor 11, the insulating substrate 13, the current fuse 15 and the welding end of the lead 17, so that the free end of the lead 17 is exposed outside.

Referring to fig. 4, fig. 4 is a schematic view of the insulating substrate 13 in fig. 2, the current fuses 15 are printed on the other side of the insulating substrate 13 away from the piezoresistors 11, the number of the current fuses 15 is one or more, and the current fuses 15 are respectively spread by taking the second solder joints 114 as centers. The third pad 131, the fourth pad 132 and the second pad 114 are connected by the current fuse 15.

The current fuse 15 is a positive temperature coefficient fuse having a higher positive temperature coefficient, the coefficient is between 200 and 600PPM, and in an embodiment, the use of 200PPM and 600PPM is respectively realized.

The voltage-sensitive voltage of the intrinsic safety piezoresistor provided by the utility model can be selected according to actual parameters, so that the current fuse of the piezoresistor can not be abnormally disconnected when enduring normal impact performance; the intrinsic safety piezoresistor is connected into a circuit, and the intrinsic safety piezoresistor works normally in the normal protection process; when an abnormal large current impacts, one of the conditions is to fuse the current fuse due to the large current; the second situation is that the leakage current of the piezoresistor increases slowly, and as time goes on, when the leakage current flows through the piezoresistor, the generated heat is larger than the heat dissipated outwards by the body, the temperature of the piezoresistor rises, and meanwhile, the flowing current also increases continuously. The resistance value of the current fuse has a larger positive temperature coefficient, for example, the current fuse can bear 20A of conducting current at 25 ℃; the conductive current of 16A can be borne at 80 ℃, and the conductive current of 12A can be borne at 120 ℃; the conducting current of only 5A can be borne at 200 ℃. Thus, when the varistor is at the very end of the detonation, the smaller current quickly opens the current fuse. Referring to fig. 5, the intrinsically safe voltage dependent resistor of the present invention is applied to the application circuit of fig. 1, 2, 3, 4, and breaks the current fuse, and then completely breaks the voltage-sensitive power supply source of the fault, thereby achieving faster and safer intrinsically safe protection effect.

It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. Not all embodiments are exhaustive. All obvious changes or modifications which belong to the technical scheme of the utility model are still within the protection scope of the utility model.

Claims

1. An intrinsically safe varistor, comprising: the voltage-sensitive resistor type power supply comprises a voltage-sensitive resistor, an insulating substrate welded with the voltage-sensitive resistor, a current fuse positioned on the insulating substrate, a plurality of leads respectively welded on the voltage-sensitive resistor and the insulating substrate, and a packaging layer arranged on the outer side of the voltage-sensitive resistor; the piezoresistor comprises a first welding surface and a second welding surface opposite to the first welding surface, wherein a first welding spot is arranged at the center of the first welding surface, and a second welding spot is arranged at the center of the second welding surface; and the insulating substrate is provided with a third welding spot and a fourth welding spot on the left side and the right side or the upper side and the lower side of the second welding spot respectively.

2. An intrinsically safe varistor as claimed in claim 1, wherein the insulating substrate is provided with a circular hole in the centre, and a layer of solderable electrode is provided around the circular hole, the substrate being soldered to the second solder joint via the electrode.

3. The intrinsically safe varistor of claim 1, wherein the current fuses are disposed on the other side of the insulating substrate from the varistor, the current fuses being one or more in number and respectively spread out around the second solder joint.

4. The intrinsically safe varistor of claim 1, wherein the leads comprise a first lead bonded to a first solder joint, a second lead bonded to a second solder joint, a third lead bonded to a third solder joint, and a fourth lead bonded to a fourth solder joint, wherein the bonding ends of the leads are located inside the encapsulation layer and the free ends are exposed.

5. The intrinsically safe varistor of claim 1 or 4, wherein the encapsulation layer encapsulates the varistor, the insulating substrate, the current fuse and the bonding ends of the leads, leaving the free ends of the leads exposed.

6. The intrinsically safe varistor of claim 1, wherein the third and fourth solder joints are connected to the second solder joint by the current fuse.

7. The intrinsically safe varistor of claim 6, wherein the current fuse is a positive temperature coefficient fuse.