CN109727833B

CN109727833B - Protection element and circuit protection device thereof

Info

Publication number: CN109727833B
Application number: CN201711041277.9A
Authority: CN
Inventors: 苏聪敏; 蔡东成; 王绍裘
Original assignee: Polytronics Technology Corp
Current assignee: Polytronics Technology Corp
Priority date: 2017-10-30
Filing date: 2017-10-30
Publication date: 2021-07-30
Anticipated expiration: 2037-10-30
Also published as: CN109727833A

Abstract

The invention provides a protection element and a circuit protection device thereof. The protection element comprises a first planar substrate, a second planar substrate, a heating element and a fuse element. The second plane substrate is attached to the lower surface of the first plane substrate to form a composite structure. The heating member includes an insulating plate and a heat generating layer formed on a surface of the insulating plate. The heating element is arranged on the first plane substrate, and the insulating plate is arranged between the first plane substrate and the heating layer. The fuse component is arranged above the heating component. When an overvoltage or an overtemperature occurs, the heating member generates heat to melt the fuse.

Description

Protection element and circuit protection device thereof

Technical Field

The present invention relates to a protection device applied to an electronic device and a circuit protection device including the same, and more particularly, to a protection device having a function of preventing overvoltage, overcurrent, or overtemperature, and a circuit protection device including the same.

Background

As a known protection element for cutting off an overcurrent, a current fuse (fuse) composed of a low melting point metal body such as lead, tin, or antimony is widely known. Then, in order to prevent overcurrent and overvoltage, a protective element including a heat generating layer and a low melting point metal layer laminated in this order on one planar substrate has been continuously developed. When overvoltage occurs, the heating body generates heat, the heat is transferred upwards from the bottom, the electrode bearing the low-melting-point metal body is heated, the low-melting-point metal body is fused, and flowing current is cut off, so that related circuits or electronic devices are protected.

In recent years, mobile devices are highly popular, and information products such as mobile phones, computers, personal mobile assistants and the like are seen everywhere, so that the dependence of people on the information products is increased. However, news about explosion of batteries of portable electronic products such as mobile phones during charging and discharging is presented from time to time. Therefore, manufacturers gradually improve the design of the over-current and over-voltage protection devices, and enhance the protection measures of the battery during charging and discharging to prevent the battery from exploding due to over-voltage or over-current during charging and discharging.

The protection method of the protection device proposed in the prior art is to connect the fuse in the protection device in series with the circuit of the battery, and to electrically connect the low melting point metal layer and the heat generating layer in the protection device to the switch (switch) and the Integrated Circuit (IC) device. Therefore, when the IC component measures the overvoltage, the switch is started to be conducted, so that the current passes through the heating layer in the protection component, the heating layer generates heat to fuse the fuse, and the circuit of the battery is in an open circuit state to achieve the overvoltage protection. It is well known to those skilled in the art that when an overcurrent occurs, a large amount of current flows through the fuse to cause the fuse to generate heat and blow, thereby achieving the overcurrent protection.

Fig. 1 is a schematic cross-sectional view of a conventional protection device, which can implement the protection mechanism. The protection device 100 includes a planar substrate 110, a heating member 120, an insulating layer 130, a low-melting-point metal layer 140, a flux 150, and a cover 170. The outer edge of the housing 170 is disposed on the surface of the planar substrate 110, and provides an inner space for accommodating the heating element 120, the insulating layer 130, the low melting point metal layer 140 and the flux 150. The heater 120 is disposed on the planar substrate 110 and electrically connected to the two heater electrodes 125. The low melting point metal layer 140 connects the electrode layers 160 on both sides and one intermediate electrode 165. An insulating layer 130 covers the heater 120 and the heater electrodes 125. The low melting point metal layer 140 is disposed above the insulating layer 130 as a fuse, and the flux 150 completely covers the low melting point metal layer 140. In this way, when the heating element 120 generates heat, the low melting point metal layer 140 can be directly melted, so that the low melting point metal layer 140 is melted and flows to the electrode layers 160 and the middle electrode 165 on both sides, and the low melting point metal layer 140 is separated into three pieces from the original whole metal after being melted, thereby cutting off the current to achieve the protection purpose. However, since the heating member 120 directly contacts the planar substrate 110, and the area of the planar substrate 110 is usually much larger than that of the heating member 120, the heat generated by the heating member 120 may not be uniformly conducted, so that the heat is concentrated on a certain region of the planar substrate 110 to cause cracks. In addition, the cross-sectional area of the connection circuit between the low melting point metal layer 140 and the external electrode is generally small, and is not suitable for application of a large current (> 70A).

Disclosure of Invention

The invention provides a protection element and a circuit protection device comprising the same, which have the functions of overvoltage, overcurrent and/or overtemperature protection and are suitable for the application of large current (such as rated current of 60A-300A). The heating piece in the protection element has uniform heat conduction characteristic through modular design, and can bear high power without damage. In addition, the protective element of the invention can fuse the fuse link therein by using lower power.

According to a first aspect of the present invention, there is provided a protection element comprising a first planar substrate, a second planar substrate, a heating member and a fuse. The second plane substrate is attached to the lower surface of the first plane substrate to form a composite structure. The heating member includes an insulating plate and a heat generating layer formed on a surface of the insulating plate. The heating element is arranged on the first plane substrate, and the insulating plate is arranged between the first plane substrate and the heating layer. The fuse component is arranged above the heating component. When an overvoltage or an overtemperature occurs, the heating member generates heat to melt the fuse.

In one embodiment, the insulating plate has an area that can uniformly conduct heat generated by the heat generating layer without cracking.

In one embodiment, the area of the insulating plate is 1 to 2 times of the area of the heat generating layer.

In one embodiment, the protection device further includes two external electrodes connected to two ends of the fuse, and a cross-sectional area of the external electrodes along a current direction is larger than a cross-sectional area of the fuse.

In one embodiment, the external electrode is provided with a groove for accommodating an end portion of the fuse.

In one embodiment, the protection device further comprises an intermediate electrode connected to a lower surface of the fuse.

In one embodiment, the surface of the insulating plate is provided with two heating electrodes connected to two ends of the heating layer.

In one embodiment, one of the two heating electrodes is electrically connected to the intermediate electrode.

In one embodiment, when the first planar substrate is cracked due to overheating, the crack does not extend to the second planar substrate.

According to a second aspect of the present invention, a circuit protection device is provided, which comprises the protection device, and a detector and a switch are collocated. The detector is used for detecting the voltage drop or temperature of a circuit to be protected. The switch is connected with the detector to receive the detection signal. When the detector detects a voltage drop or a temperature exceeding a preset value, the switch is turned on, so that current flows through the heating element, and the heating element heats to melt the fuse element.

The protective element of the invention can be used for the product application of high current (such as 60A-300A rated current) because the sectional area of the external electrode connected with the fuse link is larger. The heating layer of the heating element in the protection element is particularly borne by the insulating plate, and can uniformly absorb and conduct heat generated by the heating layer to avoid cracking, so that the bearable power of the heating element is improved. In addition, the protection element of the invention uses the design of the composite substrate, and can improve the reliability of the substrate.

Drawings

Fig. 1 shows a schematic cross-sectional structure of a conventional protection device.

Fig. 2 is a schematic perspective view of a protection device according to an embodiment of the invention.

Fig. 3 is a schematic perspective exploded view of a protection device according to an embodiment of the invention.

FIG. 4 is a schematic cross-sectional view of FIG. 2 taken along line 1-1.

Fig. 5 is a schematic perspective view of a part of a protection device according to an embodiment of the invention.

Fig. 6 is a circuit diagram of a circuit protection device according to an embodiment of the invention.

Wherein the reference numerals are as follows:

20: a protective element;

21: a first planar substrate;

22: an insulating plate;

23: a heating member;

24: a fuse;

25: a second planar substrate;

26: an electrode pattern;

27: an electrode layer;

28: heating the electrode;

29: an insulating layer;

30: an intermediate electrode;

31: a housing;

32: an external electrode;

33: an external electrode;

34: an external electrode;

35: a heat generating layer;

40: aligning holes;

50: a circuit protection device;

51: a detector;

52: a switch;

100: a protective element;

110: a planar substrate;

120: a heating member;

125: a heating element electrode;

130: an insulating layer;

140: a low melting point metal layer;

150: soldering flux;

160: an electrode layer;

165: an intermediate electrode;

170: a housing;

311: extending the column;

321: a groove;

331: a groove;

341: and (6) extending the column.

Detailed Description

In order to make the aforementioned and other technical matters, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Fig. 2 is a perspective view of a protection device 20 according to a first embodiment of the present invention, fig. 3 is an exploded perspective view of the protection device 20, and fig. 4 is a cross-sectional view of the protection device 20 of fig. 2 along the section line 1-1. Fig. 5 is a schematic perspective view of the protective element 20 with the cover 31 removed. The protection element 20 mainly comprises a heating member 23 and a fuse 24, wherein when an overvoltage or an overtemperature occurs, the heating member 23 generates heat to melt the fuse 24, thereby providing overvoltage or overtemperature protection. The first planar substrate 21 of the protection device 20 is provided with an electrode pattern 26, an electrode layer 27, a heating member 23, a fuse 24, and an upper cover 31 in this order. The heating element 23 is disposed on the first planar substrate 21, is a heating module using the insulating plate 22 as a substrate, and includes an insulating plate 22 and a heat generating layer 35 formed on the surface of the insulating plate 22, wherein the insulating plate 22 is disposed between the first planar substrate 21 and the heat generating layer 35. The two heating electrodes 28 can be formed on the surface of the insulating plate 22 by printing, and the heat generating layer 35 can be formed on the heating electrodes 28 by printing. Both ends of the heat generating layer 35 are connected to the elongated extensions of the two heating electrodes 28, respectively, to form a conductive path. The fusing member 24 is disposed above the heating member 23, and both ends thereof are connected to the

external electrodes

32 and 33 to form a conductive path. In this embodiment, an intermediate electrode 30 is connected to the lower center of the fuse 24, and one end of the intermediate electrode 30 is connected to the corresponding lower heating electrode 28, so that the fuse 24 forms an electric circuit including two fuses (fuses). The fuse element 24 may be covered with rosin or other soft metal or flux. An insulating layer 29 is provided between the heat generating layer 35 and the intermediate electrode 30 as a separator. The electrode pattern 26 is disposed on the first planar substrate 21 for connecting the

external electrodes

32, 33 and 34. The electrode layer 27 connects the heating member 23 and the electrode pattern 26. In one embodiment, a second planar substrate 25 with a thickness equal to or greater than the first planar substrate 21 is disposed below the first planar substrate to form a substrate assembly. That is, the second planar substrate 25 is attached to the lower surface of the first planar substrate 21 to form a composite structure, thereby improving structural strength. When the local heat is high, since the heat is concentrated on the first planar substrate 21 adjacent to the heating member 23, even if the first planar substrate 21 has a crack, the crack does not extend to the second planar substrate 25. Therefore, the cracking can be limited to the first planar substrate 21, and the second planar substrate 25 can be prevented from cracking. If the second planar substrate 25 is thicker, the structural strength is better, and the normal operation of the protection device 20 can be maintained even if the first planar substrate 21 is damaged. In one embodiment, extending posts 311 are disposed at the four corners of the housing 31 and can be inserted into corresponding holes of the first planar substrate 21 and the second planar substrate 25 to combine with each other, so as to form a hollow chamber with the first planar substrate 21 for accommodating the fuse 24 and the heating element 23. The first planar substrate 21, the second planar substrate 25, the electrode pattern 26, the electrode layer 27, the insulating plate 22, the heater electrode 28, and the intermediate electrode 30 may provide alignment holes (e.g., the alignment hole 40 in the heater electrode 28), thereby improving assembly efficiency and accuracy. In one embodiment, the extension column 341 is disposed below the external electrode 34 for being inserted into the corresponding holes of the first planar substrate 21 and the second planar substrate 25 for connection and fixation.

In particular, the positions where the

external electrodes

32 and 33 are connected to the fuse 24 are provided with

corresponding recesses

321 and 331 to accurately couple the fuse 24. In the present embodiment, the cross-sectional area of the

external electrodes

32 and 33 connecting the fuse 24 is larger than the cross-sectional area of the fuse 24 in the current direction. The plurality of members thus provide a large cross-sectional area for the passage of current, and are therefore suitable for high current applications, such as 60A to 300A rated current protection device applications. In this embodiment, the heating member 23 is formed by forming the heat generating layer 35 on the basis of the insulating plate 22. The insulating plate 22 is preferably made of a ceramic material, and the area of the insulating plate 22 covers and is slightly larger than the area of the heat generating layer 35, and is about 1-2 times. The insulation board 22 has a proper area size to conduct heat generated by the heat generating layer 35 uniformly and rapidly, so as to avoid cracks caused by excessive concentration of heat in a certain area due to nonuniform heat conduction when the area is too large, and thus the heating element 23 can bear higher power without damage. In addition, the heat generating layer 35 does not directly contact the first flat substrate 21, so that the probability of cracking of the first flat substrate 21 can be reduced. For the fuse element 24, the power required for fusing is reduced because the modular heating element 23 is less susceptible to heat dissipation, requiring only about 1/2 watts from a commercially available product.

In one embodiment, the first planar substrate 21 and the second planar substrate 25 may be insulating planar substrates of square plates, and the material may be selected from, for example, alumina, aluminum nitride, zirconia, or heat-resistant glass plate. The electrode pattern 26, the electrode layer 27, the heater electrode 28, and the intermediate electrode 30 may comprise silver, gold, copper, tin, nickel, or other conductive metal, and have a thickness of about 0.005 to 1mm, or more specifically 0.01mm, 0.05mm, 0.1mm, 0.3mm, and 0.5 mm. Except for making by printingIn addition to the electrodes, metal sheets may also be used for high voltage applications. The fuse 24 may be made of a low melting point metal or alloy thereof, such as Sn-Pb-Ag, Sn-Sb, Sn-Zn, Zn-Al, Sn-Ag-Cu, Sn-Bi-Ag, and Sn-Bi-Ag-Cu, and preferably made of a lead-free material, which can further reduce the resistance value and is suitable for high current applications. The length and width of the fuse 24 can be adjusted depending on the amount of current that needs to be passed. The fuse 24 has a thickness of 0.005mm to 1mm, preferably 0.01mm to 0.5mm, and most preferably 0.02mm to 0.2mm, or more particularly 0.05mm, 0.1mm, 0.3 mm. The material of the heat generating layer 35 may include ruthenium oxide (RuO)₂) And additives such as silver (Ag), palladium (Pd), and platinum (Pt). The insulating layer 29 for isolating the heating element 23 from the fuse element 24 may be made of glass (glass), epoxy resin (epoxy), alumina, silicone, or glaze.

The

external electrodes

32, 33 and 34 of the above embodiments are metal sheets extending in parallel, and may include holes therein for connecting an external power source or a circuit to be protected by using a connector such as a screw. In practice, the protection device of the present invention can also be designed as a surface-mount type protection device, and is electrically connected to the lower bonding pad by the conductive surface or the conductive via on the side surface, so as to be used for surface-mounting to the circuit board.

An equivalent circuit diagram of the protection element 20 of the present invention may be shown as a circuit of a dashed box in fig. 6. The external electrode 32 serves as a terminal a1 to which a device to be protected (e.g., a secondary battery or a motor) is connected, and the external electrode 33 is connected to a terminal B1 of, for example, a charger or the like. The external connection electrode 34 is connected to the heating member 23, and the other end of the heating member 23 is connected to the intermediate electrode 30. The fuse 24 forms a circuit including 2 fuses (fuses) connected in series, and the heating member 23 forms a heater (shown by a resistance symbol) according to the circuit design of the protection member 20. In one embodiment, the external electrode 34 is electrically connected to a switch 52, and the switch 52 may be a Field Effect Transistor (FET), for example. The gate (gate) of the switch 52, such as a FET, is connected to the detector 51, and is connected to the other terminal a2 of the circuit to be protected and the other terminal B2 of the charger. The detector 51 may be an IC device, and has the function of detecting voltage drop or temperature. When there is no over-voltage or over-temperature, the switch 52 is open and current passes through the fuse 24, but no current flows through the heating element 23. If an overcurrent occurs, the fuse 24 will be blown to provide overcurrent protection. When the detector 51 detects that the voltage exceeds a predetermined value (overvoltage) or the temperature exceeds a predetermined value (overtemperature), the switch 52 is switched to the conducting state, and the current flows from the source (source) to the drain (drain) of the switch 52 and flows through the heating element 23. The heating element 23 heats to fuse the fuse 24, thereby providing protection against over-voltage or over-temperature. In summary, B1 to a1, B2 to a2 form 2 power lines provided to the circuit to be protected, and the combination of the protection device 20, the detector 51 and the switch 52 connects the two power lines to form the circuit protection device 50. When the detector 51 detects a voltage drop or a temperature exceeding a predetermined value, the heating element 23 is activated to melt the fuse element 24.

The equivalent circuit of the protection device of the previous embodiment includes 2 fuses and 1 heater. However, other different circuit designs can be used to form a circuit including, for example, 2 fuses and 2 heaters, or 1 fuse and 1 heater, and still be covered by the inventive technique of the present invention. In another embodiment, the fuse element can be electrically connected to 2 external electrodes or pads to form one conductive path, and the heating element can be connected to another 2 external electrodes or pads to form another conductive path, so that the current flowing through the heating element can be independently controlled to fuse the fuse element.

In summary, in the heating element of the protection element of the present invention, the insulating plate can uniformly conduct the heat generated by the heating layer without cracking, so that the heating element can bear high power without damage. In addition, the composite structure design of the second planar substrate and the first planar substrate can optimize the structural strength, and in case of crack generation due to overheating of the first planar substrate, the crack extends to the bonding interface of the first planar substrate and the second planar substrate at most and does not extend to the second planar substrate. Therefore, the second planar substrate can still maintain its integrity, so that the protection device can maintain normal operation. The fuse in the protection element and the external electrode connected with the fuse provide larger sectional area for current to pass through, and the protection element is suitable for application of large current (such as 60A-300A). In addition, the modularized heating element can concentrate heat and is not easy to dissipate, so that the fusing power required by the fusing element can be reduced.

While the technical content and the technical features of the invention have been disclosed, those skilled in the art can make various substitutions and modifications without departing from the concept of the invention based on the teaching and the disclosure of the invention. Therefore, the protection scope of the present invention should not be limited to the embodiments disclosed, but should include various alternatives and modifications without departing from the invention, which are encompassed by the claims.

Claims

1. A protective element, comprising:

a first planar substrate;

the second planar substrate is attached to the lower surface of the first planar substrate to form a composite structure;

the heating element comprises an insulating plate and a heating layer formed on the surface of the insulating plate, the heating element is arranged on the first plane substrate, the insulating plate is arranged between the first plane substrate and the heating layer and does not cover the heating layer, the insulating plate is made of ceramic materials, and the area of the insulating plate is 1-2 times that of the heating layer; and

a fuse element disposed above the heating element;

the protection element also comprises two external electrodes connected with two ends of the fuse element, and the sectional area of the external electrodes is larger than that of the fuse element along the current direction; and

the external electrode is provided with a groove to accommodate the end part of the fuse element and increase the contact area between the fuse element and the external electrode;

wherein the heating member generates heat to melt the fuse when an overvoltage or an overtemperature occurs.

2. The protective member according to claim 1, wherein the insulating plate has an area sized to uniformly conduct heat generated from the heat generating layer without cracking.

3. The protective element according to claim 1, further comprising an intermediate electrode connected to a lower surface of the fuse.

4. The protective member according to claim 3, wherein the insulating plate is provided at its surface with two heating electrodes connected to both ends of the heat generating layer.

5. The protective element according to claim 4, wherein one of the two heating electrodes is electrically connected to the intermediate electrode.

6. The protective element according to claim 1, wherein when the first planar substrate cracks due to overheating, the cracks do not extend to the second planar substrate.

7. A circuit protection device, comprising:

a protection device, comprising:

a first planar substrate including a first surface;

a fuse element disposed above the heating element;

a detector for detecting the voltage drop or temperature of a circuit to be protected; and

a switch connected to the detector for receiving the detection signal;

when the detector detects a voltage drop or a temperature exceeding a preset value, the switch is turned on, so that current flows through the heating element, and the heating element heats to melt the fuse element.

8. The circuit protection device of claim 7 wherein the insulating plate has an area sized to uniformly conduct heat generated by the heat generating layer without cracking.