TW201917764A - Protection device and circuit protection apparatus containing the same - Google Patents

Abstract

A protection device and a circuit protection apparatus containing the same are disclosed. The protection device comprises a substrate, a fusible element and a heating element. The substrate is provided with a first electrode and a second electrode. The fusible element comprises a first metal layer and a second metal layer. The second metal layer is formed on the surface of the first metal layer and has a higher melting point than that of the first metal layer. The fusible element connects to the first electrode and the second electrode through solder. The solder has a lower melting point than that of the first metal layer. The heating element heats up to blow the fusible element in the event of over-voltage or over-temperature.

Description

Protection element and circuit protection device thereof

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

A current fuse having a low-melting-point metal body such as lead, tin, silver, antimony or copper is widely known as a protective element for cutting off an overcurrent. Thereafter, in terms of preventing overcurrent and overvoltage, the protective element is continuously developed, which comprises sequentially laminating a heat generating layer and a fusible element on a planar substrate. When an overvoltage occurs, the heat generating layer generates heat, and heat is transferred upward from the bottom, and the fuse is heated to fuse the fuse, thereby cutting off the current flowing through to protect the associated circuit or electronic device.

In recent years, mobile devices have become highly popular, and information products such as mobile phones, computers, and personal mobile assistants are everywhere, making people's dependence on information products increasing. However, from time to time, there has been news about the explosion of batteries in portable electronic products such as mobile phones during charging and discharging. Therefore, the manufacturer gradually improves the design of the aforementioned overcurrent and overvoltage protection components, and enhances the protection measures of the battery during charging and discharging to prevent the battery from exploding due to overvoltage or overcurrent during charging and discharging.

The protective element proposed by the prior art is protected by connecting the fuse in the protection element in series with the circuit of the battery, and electrically connecting the fuse and the heat generating layer in the protection element to the switch and the integrated circuit (IC) component. . In this way, when the IC component measures the overvoltage, the switch is turned on, and the current is passed through the heat generating layer in the protection component, so that the heat generating layer generates heat to blow the fuse, thereby causing the circuit of the battery to be disconnected. And to achieve overvoltage protection. Those skilled in the art can also fully understand that when an overcurrent occurs, a large amount of current flowing through the fuse will cause the fuse to heat up and fuse, thereby achieving overcurrent protection.

However, in order to prevent the subsequent reflow process from melting at a high temperature in order to prevent the fuse in the existing protective element from being used, a lead-containing (Pb) high melting point solder having a melting point of 300 ° C or higher is usually used. However, the use of Pb-containing solders will be limited by the RoHS Directive (Environmental Restriction Directive) environmental directive. Therefore, how to reflow in the case of using a fuse having a lower melting point is a problem that the protective component needs to overcome.

The present invention provides a protection element and a circuit protection device including the same, which has the function of overvoltage, overcurrent and/or overtemperature protection. The fuse of the protection element has two inner and outer metal layers of different melting points, which can resist the problem of melting of the inner metal layer caused by high temperature in the subsequent reflow process.

According to a first aspect of the invention, there is provided a protective element comprising a substrate, a fuse and a heating element. The surface of the substrate is provided with a first electrode and a second electrode. The fuse includes a first metal layer and a second metal layer, the second metal layer is disposed on a surface of the first metal layer, and a melting point of the second metal layer is higher than a melting point of the first metal layer. The fuse is connected to the first electrode and the second electrode by solder, and the melting point of the solder is lower than the melting point of the first metal layer. When an overvoltage or overtemperature occurs, the heating element heats up to melt the fuse.

In one embodiment, the melting point of the second metal layer is higher than the temperature of the subsequent reflow process.

In one embodiment, the second metal layer limits the flow of the first metal layer when the protective element is reflowed.

In one embodiment, the first metal layer comprises tin (Sn) or an alloy thereof.

In one embodiment, the second metal layer comprises silver (Ag), copper (Cu), gold (Au), nickel (Ni), or alloys thereof.

In one embodiment, the first metal layer has a thickness of 0.02 to 0.3 mm, and the second metal layer has a thickness of 0.002 to 0.01 mm.

In one embodiment, the first metal layer has a thickness of 10 to 150 times the thickness of the second metal layer.

In one embodiment, the volume of the first metal layer is greater than the volume of the second metal layer.

In one embodiment, in the protection element, the fuse member includes two fuses, and the heating element is an equivalent circuit including one heater.

According to a second aspect of the present invention, a circuit protection device comprising the aforementioned protection component is provided with a detector and a switch. The detector is used to detect the voltage drop or temperature of a circuit to be protected. A switch is connected to the detector to receive its detection signal. When the detector detects a voltage drop or the temperature exceeds a preset value, the switch is turned on, and a current flows through the heating member, so that the heating member generates heat to melt the fuse.

The fuse element in the protective element of the present invention is a metal layer composite structure of the inner and outer layers, and the metal layer of the outer layer has a higher melting point than the metal layer of the inner layer or is further higher than the temperature of the subsequent reflow process. In this way, in the subsequent reflow, even if the reflow temperature is greater than the melting point of the inner metal layer, the inner metal layer is limited or covered by the outer metal layer, and does not flow arbitrarily or cause severe deformation. Therefore, the lower melting inner metal layer can be applied to the fuse and resist the subsequent high temperature reflow process.

The above and other technical contents, features and advantages of the present invention will become more apparent from the following description.

1 shows a block diagram of a protective element 10 in accordance with an embodiment of the present invention. The protective element 10 has a substrate 11, a heating member 12, a heating electrode 13, an insulating layer 14, an intermediate electrode 15, a fuse 16, a solder 17, an electrode layer 18, lower electrodes 19a and 19b, and a cover 20. The outer edge of the outer cover 20 is disposed on the surface of the substrate 11, and an internal space is provided to accommodate the heating member 12, the fuse member 16, and the like. The substrate 11 is typically a planar insulating substrate. The heating element 12 is disposed on the substrate 11 and is electrically connected to the left and right heating electrodes 13 at both ends thereof. The fuse member 16 is electrically connected to the first electrode 18a and the second electrode 18b on both sides of the electrode layer 18, and the intermediate portion of the fuse member 16 is connected to the intermediate electrode 15 disposed on the surface of the insulating layer 14, wherein the fuse member 16 is provided at both ends It may be connected to the first electrode 18a and the second electrode 18b by the solder 17. The first electrode 18a and the second electrode 18b may be connected to the left and right lower electrodes 19a and 19b through the conduction members 22 on the side of the substrate 11. The lower electrodes 19a and 19b can serve as an interface for surface adhesion to a circuit board (not shown). The insulating layer 14 covers the heating member 12 and the heating electrode 13. The fuse 16 is disposed above the insulating layer 14 as a fuse on the circuit. The fuse member 16 includes a first metal layer 16a and a second metal layer 16b disposed on the surface of the first metal layer 16a, and has a composite structure. The fuse member 16 may be entirely or partially coated with the flux 21 on the fuse member 16 in order to prevent oxidation of the second metal layer 16b or the first metal layer 16a. The flux 21 can form an oxidation resistant layer mainly on the surface of the outermost second metal layer 16b, and can effectively prevent oxidation of the second metal layer 16b, thereby maintaining rapid melting efficiency. When an overvoltage or an overtemperature occurs, the heating member 12 generates heat and transfers heat to the fuse member 16 to melt the fuse member 16 to flow to the first electrode 18a, the second electrode 18b, and the intermediate electrode 15 on both sides, resulting in the flow. Fuse, thereby cutting off the current for protection purposes. 2 shows an equivalent circuit diagram of the protection element 10 of FIG. 1. In the present embodiment, the fuse element 16 will contain two fuses by the arrangement of the intermediate electrode 15. As described above, when an overvoltage or an overtemperature occurs, the heating member 12 generates heat to melt the fuse (fuse) 16.

The substrate 11 may have a square structure, and the material may be selected from an insulating material such as alumina, aluminum nitride, zirconia, or glass ceramic, or a printed wiring board for a glass epoxy substrate or a phenolic substrate. . The thickness of the substrate 11 is about 0.1 to 2 mm. The electrode layer 18, the heating electrode 13 and the intermediate electrode 15 may comprise silver, gold, copper, tin, nickel or other conductive metal having a thickness of about 0.005 to 1 mm, or particularly 0.01 mm, 0.05 mm, 0.1 mm, 0.3 mm, 0.5. Mm. In addition to using printed electrodes, it can also be fabricated using sheet metal for high voltage applications.

The fuse member 16 is a composite structure composed of an inner layer and an outer layer, and may have a rectangular strip shape or a strip shape. The first metal layer 16a as an inner layer is a low melting point metal layer, and is outside the first metal layer 16a. The second metal layer 16b is a high melting point metal layer, that is, the second metal layer 16b has a higher melting point than the first metal layer 16a. The second metal layer 16b may be formed on the surface of the first metal layer 16a by plating, vapor deposition, lamination, rolling, or the like. The first metal layer 16a preferably contains a metal containing Sn as a main component or an alloy thereof, such as Sn, Sn-Ag, Sn-Sb, Sn-Zn, Sn-Ag-Cu, Pb-Sn-Ag, Sn-Zn- Cu, Sn-Bi-Ag, and Sn-Bi-Ag-Cu, wherein a Pb-free material is preferably selected to comply with the RoHS directive, but the invention is not limited to the use of a Pb-free material. The second metal layer contains, for example, Ag, Cu, Au, Ni, Zn, or a metal or alloy thereof as a main component. In one embodiment, the melting point of the second metal layer 16b is higher than the melting point of the first metal layer 16a, and the melting point of the second metal layer 16b is also higher than the reflow temperature. As a result, the second metal layer 16b as the outer layer restricts the flow of the first metal layer 16a stacked or covered therein, so even if the reflow temperature exceeds the melting temperature of the first metal layer 16a, the fuse 16 does not As for the fuse. The surface of the second metal layer 16b may further form an oxidation resistant layer containing, for example, Sn, such that in the case where the second metal layer 16b is, for example, a Cu layer, oxidation of the Cu layer is prevented, thereby preventing the fuse from being blown. The time required increases due to oxidation of the Cu layer. If the second metal layer 16b uses the Ag layer, it has the advantage of being less susceptible to oxidation, but the price is relatively high. The material of the heating member 12 may include additives such as ruthenium oxide (RuO ₂ ) and silver (Ag), palladium (Pd), and platinum (Pt). As the material of the insulating layer 14 which is isolated between the heating member 12 and the fuse member 16, a glass, an epoxy, an alumina or a silicone or a glaze may be used.

In one embodiment, the fuse member 16 has a thickness of about 0.05 mm to 0.4 mm, wherein the first metal layer 16a has a thickness of about 0.02 to 0.3 mm, and the second metal layer 16b (single layer) has a thickness of about 0.002 to 0.01 mm. Specifically, the thickness of the first metal layer 16a is greater than the thickness of the second metal layer 16b (single layer), for example, 10 times to 150 times, or 20 times, 50 times, 100 times. However, if the thickness ratio is more than 150 times, that is, the first metal layer 16a is relatively thick, the second metal layer 16b is relatively thin, and the too thin second metal layer 16b has a molten first metal layer 16a during reflow. After eroding, it is impossible to maintain its shape. Preferably, the volume of the first metal layer 16a in the fuse member 16 is larger than the volume of the second metal layer 16b. When an abnormal condition such as an overvoltage or an overcurrent occurs, the first metal layer 16a has a large volume to effectively etch the second metal layer 16b, and the fuse 17 is accelerated in a short time. In summary, the ratio of the thickness and the volume of the first metal layer 16a and the second metal layer 16b have appropriate values, and the values are too large or too small to be suitable. The second metal layer 16b which is too thin or too small may be at risk of being etched by the molten first metal layer 16a during reflow, and the second metal layer 16b which is too thick or too large may delay the fusing of the fuse 16. time.

3, 4 and 5 show the different embodiment configurations of the fuse member 16. As shown in FIG. 3, a second metal layer 16b is provided on the upper surface and the lower surface of the first metal layer 16a. As shown in FIG. 4, the second metal layer 16b covers the periphery of the first metal layer 16a except for the opposite end faces of the fuse member 16. As shown in FIG. 5, the first metal layer 16a includes both end faces which are all covered by the second metal layer 16b. The better the coating, the stronger the ability to resist melt deformation. When the protective element 10 is subjected to a subsequent reflow process, the temperature exceeds the melting point of the first metal layer 16a of the lower melting point, but because the first metal layer 16a is sandwiched or covered by the second metal layer 16b, the second The metal layer 16b restricts the flow of the first metal layer 16a, so that the entire fuse member 16 does not melt and flow to become an open circuit.

Table 1 shows the test results of the surface temperature and the fusing current of Examples E1 and E2 of the protective element of the present invention and Comparative Examples C1 and C2. The surface temperature is measured by placing a thermocouple on the surface of the fuse member 16. The first metal layer 16a is made of Sn or Pb95.5-Sn2-Ag2.5 and has melting points of 232 ° C and 308 ° C, respectively. In the embodiment E1 and the embodiment E2, the second metal layer 16b is disposed on the upper and lower surfaces of the first metal layer 16a, as shown in FIG. The second metal layer 16b is made of an Ag layer. The total thickness of the fuse member 16 of the embodiment E1 and the embodiment E2 is 0.09 mm, and the fuse member 16 of the comparative example C1 and the comparative example C2 has only the first metal layer 16a and no second metal layer 16b, and the thickness thereof is 0.08 mm. . That is, the thickness of the first metal layer 16a in all of the examples and the comparative examples was 0.08 mm, and the comparative examples C1 and C2 additionally included the upper and lower second metal layers 16b each having a thickness of 0.005 mm. In the case of the embodiment E1 and the comparative example C1 in which the first metal layer 16a is of the same material, since the electric resistance of the embodiment E1 having the second metal layer 16b is low, in the test of the energization of 20A and 30A, the embodiment E1 The surface temperature of the fuse 16 was reduced by about 20 to 40 ^o C compared to the comparative example C1, and the fusing current was about 2 A to 4 A higher than that of the comparative example C1. Similarly, with respect to Example E2 and Comparative Example C2, Example E2 having the second metal layer 16b coated had a lower resistance value, and in the test of energization 20A and 30A, the surface of the fuse member 16 of Example E2. The temperature was reduced by about 15~30 ^o C compared to the comparative example C2, and the fusing current was about 2A~3A higher than the comparative example C2.

Table 1

The solder 17 for soldering the fuse member 16 to the electrode layer 18 in the above embodiment E1 and the comparative example C1 is selected from Sn-Cu0.7, and its melting point 227 ^o C is lower than the melting point 232 ^o C of the first metal layer 16a. In Example E2 and Comparative Example C2, Pb-Sn2-Ag2.5 having a melting point of 268 ^o C lower than the melting point 308 ^o C of the first metal layer 16a was selected. In addition, the solder 17 may select Sn-Ag3-Cu0.7 (melting point 217 ^o C), Sn-Ag0.3-Cu0.7 (melting point 217 ^o C) or Sn-Bi-Ag (melting point 262 ^o C) depending on the melting point requirement. . In particular, the melting point of the solder 17 is lower than the melting point of the first metal layer 16a of the inner layer. The lower melting point solder 17 has a number of commercially available products to choose from, and the lower reflow temperature can be used to weld the fuse member 16. When the protective element 10 is subsequently soldered to the circuit board, even if the process temperature may be higher than the melting point of the solder 17, the 11 solder 17 disposed between the fuse 16 and the substrate is not subjected to mechanical external force, so the solder 17 does not have Flow or severe deformation.

In summary, the fuse member 16 is composed of the first metal layer 16a of the inner layer and the second metal layer 16b of the outer layer, so that it has a higher fuse than the conventional fuse member composed of a single metal layer of a lower melting point. Current and lower surface temperature. Further, the melting point of the solder 17 in combination with the fuse member 16 and the electrode layer 18 is lower than the melting point of the first metal layer 16a, and the lower melting point solder 17 has many commercially available products to be selected, and a lower temperature can be used. Reflow process.

The equivalent circuit diagram of the protection element 10 of the present invention can also be shown in the circuit of the dashed box in FIG. The first electrode 18a is connected to an end point A1 of a device to be protected (for example, a secondary battery or a motor), and the second electrode 18b is connected to an end point B1 such as a charger or the like. The intermediate electrode 15 is connected to one heating electrode 13, and the other heating electrode 13 is connected to the switch 62. According to the circuit design of the protection element 10, the fuse 16 is formed with a circuit comprising two fuses connected in series, and the heating element 12 forms a heater (shown by a resistance symbol). In one embodiment, the switch 62 can be, for example, a field effect transistor (FET). A switch 62, such as a gate of the FET, is coupled to the detector 61 and is coupled to the other terminal A2 of the circuit to be protected, and to the other end B2 of the charger. The detector 61 can be an IC component and has a function of detecting a voltage drop or a temperature. When there is no overvoltage or overtemperature, the switch 62 is open and current is passed through the fuse 16, but no current flows through the heater 12. If an overcurrent occurs at this time, the fuse 16 is blown to provide overcurrent protection. When the detector 61 detects that the voltage exceeds a predetermined value (overvoltage) or the temperature exceeds a predetermined value (over temperature), the switch 62 is switched to the on state, and the current is sourced from the source of the switch 62 to the 汲Drain and flow through the heating element 12. The heating element 12 generates heat to fuse the fuse member 16, thereby providing protection against overvoltage or overtemperature. In summary, B1 to A1, B2 to A2 form two power lines provided to the circuit to be protected, and a combination of the protection element 10, the detector 61 and the switch 62 connects the two power lines to form a circuit protection device 60. . When the detector 61 detects that the voltage drop or temperature of the circuit to be protected exceeds a preset value, the activation heating member 12 blows the fuse member 16.

The equivalent circuit of the protective element of the foregoing embodiment includes two fuses and one heater. However, it is also possible to fabricate circuit forms comprising, for example, two fuses and two heaters, or one fuse and one heater, using other different structural circuit designs, while still being covered by the innovative technology of the present invention. In still another embodiment, the fuse member electrically connects the two pads to form a conductive path, and the heating member connects the other two pads to form another conductive path, so that the current flowing through the heating member can be independently controlled to blow the fuse.

The protective element of the present invention utilizes a low melting point metal layer (first metal layer) and a high melting point metal layer (second metal layer) to form a composite structure fuse, and a low melting point metal can be used as the fuse body, but still sufficient for subsequent The problem of preventing the fuse from being melted in the high temperature process. In addition, the fuse design of the present invention can reduce the temperature of the surface of the protection component by 20-40% because of better heat dissipation efficiency, and can improve the fuse current of the fuse. The present invention can use a low melting point metal layer as the main component of the fuse member, so that a Pb-free material can be used. Although the present invention does not exclude the use of a Pb material as a fuse, it is preferred to select a Pb-free material to comply with today's environmental regulations.

The technical contents and technical features of the present invention have been disclosed as above, and those skilled in the art can still make various substitutions and modifications without departing from the spirit and scope of the invention. Therefore, the scope of the present invention should be construed as being limited by the scope of the appended claims

10‧‧‧Protection components

11‧‧‧Substrate

12‧‧‧heating parts

13‧‧‧heating electrode

14‧‧‧Insulation

15‧‧‧Intermediate electrode

16‧‧‧Fuse parts

16a‧‧‧First metal layer

16b‧‧‧Second metal layer

17‧‧‧ solder

18‧‧‧Electrical layer

18a‧‧‧first electrode

18b‧‧‧second electrode

19a‧‧‧ lower electrode

19b‧‧‧ lower electrode

20‧‧‧ Cover

21‧‧‧ Flux

22‧‧‧Connecting parts

60‧‧‧Circuit protection device

61‧‧‧Detector

62‧‧‧ switch

1 is a schematic view showing the structure of a protective element according to an embodiment of the present invention. Figure 2 shows an equivalent circuit diagram of the protection element of Figure 1. Figures 3 through 5 show various embodiments of fuses of the protective element of the present invention. FIG. 6 is a circuit diagram showing a circuit protection device according to an embodiment of the present invention.

Claims (14)

A protection element comprising: a substrate having a first electrode and a second electrode on a surface; a fuse member comprising a first metal layer and a second metal layer, wherein the second metal layer is disposed on the first metal layer a surface of the second metal layer having a melting point higher than a melting point of the first metal layer; a heating member that generates heat to melt the fuse when an overvoltage or an overtemperature occurs; wherein the fuse is connected to the solder by solder The first electrode and the second electrode have a melting point lower than a melting point of the first metal layer. A protective element according to claim 1, wherein the melting point of the second metal layer is higher than the temperature of the subsequent reflow process. The protective element of claim 2, wherein the second metal layer limits the flow of the first metal layer during reflow. The protective element of claim 1, wherein the first metal layer comprises tin or an alloy thereof. A protective element according to claim 1, wherein the second metal layer comprises silver, copper, gold, nickel or an alloy thereof. The protective element according to claim 1, wherein the first metal layer has a thickness of 0.02 to 0.3 mm, and the second metal layer has a thickness of 0.002 to 0.01 mm. The protective element according to claim 1, wherein the first metal layer has a thickness of 10 to 150 times the thickness of the second metal layer. The protective element of claim 1, wherein the volume of the first metal layer is greater than the volume of the second metal layer. A protective element according to claim 1, wherein the fuse member comprises two fuses, and the heating member is an equivalent circuit including one heater. A circuit protection device comprising: a protection component comprising: a substrate having a first electrode and a second electrode on a surface; a fuse member comprising a first metal layer and a second metal layer, the second metal layer Provided on the surface of the first metal layer, the melting point of the second metal layer is higher than the melting point of the first metal layer; and a heating element; a detector for detecting a voltage drop or temperature of the circuit to be protected; a switch connected to the detector for receiving the detection signal; wherein the fuse is connected to the first electrode and the second electrode by solder, the melting point of the solder being lower than the melting point of the first metal layer; wherein the detecting When the voltage drop is detected or the temperature exceeds a preset value, the switch is turned on, and a current flows through the heating member, so that the heating member generates heat to melt the fuse. The circuit protection device of claim 10, wherein the melting point of the second metal layer is higher than the temperature of the subsequent reflow process. The circuit protection device of claim 10, wherein the first metal layer comprises tin or an alloy thereof. The circuit protection device of claim 10, wherein the second metal layer comprises silver, copper, gold, nickel or alloys thereof. The circuit protection device of claim 10, wherein the second metal layer limits the flow of the first metal layer during reflow.