EP2471083A1

EP2471083A1 - Thermal link

Info

Publication number: EP2471083A1
Application number: EP11749108A
Authority: EP
Inventors: Joachim Aurich; Ulf Zum Felde; Bernd Krüger; Laurent Mex; Wolfgang Werner
Original assignee: Vishay BCcomponents Beyschlag GmbH
Current assignee: Vishay BCcomponents Beyschlag GmbH
Priority date: 2010-07-26
Filing date: 2011-07-26
Publication date: 2012-07-04
Anticipated expiration: 2031-07-26
Also published as: JP2013535781A; KR101539641B1; BR112013001814A2; US9899171B2; CN103038849B; CN103038849A; DE102010038401B4; ES2579004T3; EP2471083B1; DE102010038401A1; BR112013001814B1; WO2012016882A1; KR20130037726A; US20130234822A1; JP5723451B2; HUE029705T2

Abstract

In order to provide a method for isolating a circuit and a thermal link, wherein the link has a very low resistance and is suitable for high currents, in particular very high short load currents, and also has a high degree of reliability, in particular under difficult conditions, such as thermal and mechanical loading which lasts for a relatively long time, for example, the invention proposes that, during the phase transition of the material of the fusible element (10) from the solid to the liquid state, the volume of the fusible element (10) increases and the pressure increases and, owing to the increase in volume and the increase in pressure, the fusible element (10) is dislodged so as to break the electrical connection.

Description

thermal fuse

description

The invention relates to a method for the separation of a circuit. The invention further relates to a thermal fuse for disconnecting a circuit during melting of a fusible conductor.

State of the art

Thermal fuses of the specified type, for example, in the automotive industry in vehicles due to the increasing use of semiconductor devices (MOSFETs, IGBTs) for switching high currents in electrical consumers increasingly important. In case of failure of the semiconductor switching element e.g. Due to a short circuit, breakdown or other malfunction, an incorrect and possibly fatal temperature increase may occur due to a faulty current flow.

This is especially true in vehicles where certain consumers, such as Radiator fan, ABS controls, radiator fan, electric power steering or electric steering o. The like. Are not connected via the ignition, but are directly connected to the battery.

Usually, such consumers are not connected via the ignition with the battery, as after use or shutdown of the vehicle any further or after-running of the consumer must be guaranteed. For example, at a certain temperature, it is necessary to continue to run the radiator fan for a while after the vehicle is operated to avoid temperature peaks and to lower the engine temperature.

Such a fuse functions as over-temperature protection, by breaking the power supply upon reaching a switching temperature caused by a malfunction, in particular short-circuiting of an electrical component and prevents another, possibly fatal temperature increase.

But even in the non-short circuit case and other circuits that are not directly connected to the battery, such a fuse is used as Overtemperature protection. If, for example, when passing through a switching element, only a slightly increased current flows into the consumer, this fault can not be detected with a conventional current fuse. The temperature then increases in the typically encapsulated consumer continues what u. U. may even lead to a fire.

Further applications of the thermal fuse can generally be the over-temperature and fire protection of high current loads, for example, to secure solar cells or high-energy battery cells, as well as additional heaters.

Thermal fuses based on spring or melt wax technology are already used in household appliances, e.g. Coffee machines, state of the art. Such fuses can not be used for high current power applications due to their low current carrying capacity.

From the prior art thermal fuses are known from US 7,068,141 B2, which trigger without mechanical forces (such as springs).

The function of these fuses is based on the wetting properties of the fusible conductor when the tripping temperature is reached. The triggering takes place by melting the conductor, which is pulled by the wetting forces on correspondingly large surfaces. In this case, the fusible conductor is surrounded with the male surfaces of a shell, leaving a gap for the outflow of the molten conductor material.

A disadvantage of these fuses, which are commonly used in consumer applications, e.g. Cell phones are used that they are not suitable for high currents, since only a small mass of the fusible conductor is available because of the tripping principle.

For the automotive sector, there are suggestions to circumvent the above restrictions.

DE 244 375 A1 describes a thermal fuse in the form of a melt resistance for use in power supplies and power circuits.

DE 10 2007 014 338 A1 describes a thermal fuse in the form of a line structure, in particular in a stamped grid or a printed circuit board. te, which has a fuse and causes the separation of the electrical connection due to the surface tension.

DE 10 2008 003 659 AI relates to a fuse with a conductor bar, which serves as an electrically conductive connection in normal operation and melts in case of thermal failure when reaching a certain temperature.

For example, DE 10 2007 014 339 A1 describes a thermal fuse which has a connecting element and a separately formed actuator. The actuator mechanically disconnects the electrical connection upon reaching a particular trip temperature.

Furthermore, thermal fuses are known, which usually have a soldered leaf spring, which separates the electrical connection upon reaching a certain temperature.

The disadvantage of these fuses u. a., That the fusible link and the joints are exposed to permanent material stresses and thereby the life and reliability of the thermal fuse, especially under harsh environmental conditions with thermal cycling loads is limited.

DESCRIPTION OF THE INVENTION: Problem, Solution, Advantages

The invention has for its object to provide a thermal fuse for the separation of a circuit available, the fuse is very low and is suitable for high currents, in particular very high short-circuit currents, and a high reliability, especially under difficult conditions such. longer lasting thermal and mechanical load.

This object is achieved by a thermal fuse according to the features of claim 1.

The thermal fuse according to the invention is constructed as a fuse, which performs the separation of a circuit in the event of tripping by melting a fuse conductor. To ensure a reliable separation of a circuit, the thermal fuse has at least two electrically conductive connection parts and a fusible link, which melts when reaching a certain temperature. Furthermore, the thermosafe An encapsulation or wrapping on. In this case, the fusible conductor is so surrounded by a shell without a free space between the fuse element and shell or components of the thermal fuse is provided. As a material for the encapsulation or wrapping, for example, a molding material could be used based on epoxy resin. In principle, it is also possible to use other materials and painting. The thermal fuse furthermore has a layer structure, wherein at least one additional coating or material layer is provided between the connection parts and the encapsulation or encapsulation.

Using the thermal fuse according to the invention is a

Circuit separated when reaching a certain temperature. Before reaching the release temperature, the thermal fuse represents an electrical conductor with very high conductivity. In this case, two electrically conductive connection parts of the thermal fuse are electrically connected to one another by means of a fusible conductor. The material of the fusible conductor is designed such that the melting temperature of the fusible conductor material is in the range of the desired release temperature of the fuse. Upon reaching the melting temperature of the fusible conductor begins to melt. During the phase transition of the fusible material from the solid to the liquid state, the volume of the fusible conductor increases. Due to encapsulation of the fusible conductor in the thermal fuse, a pressure increase takes place. In this case, the thermal fuse is designed such that is provided by the encapsulation of the fusible conductor no free space between the fuse element and sheath for receiving the liquid melt conductor material. Within the fuse, the fusible conductor is completely surrounded by directly adjacent components, eg the sheath, the connection parts or a coating or other components of the thermal fuse applied to the connection parts. The fusible conductor is thus surrounded at any point by a free space. In addition, the fusible conductor is not in contact with a free space, the space having air or other gaseous substance. Thus, the pressure increase causes the fusible conductor to be displaced in such a way that the electrical connection between the connection parts is disconnected. The volume increase in the phase transition of the melt conductor material from the solid to the liquid state takes place as quickly as possible and in the form of a volume jump. Thus, due to a sudden increase in volume, a rapid increase in pressure and thus a safe release of the thermal fuse are possible.

The liquid melt conductor material flows due to the volume increase and the associated increase in pressure and due to the capillary action. The capillary is formed by a coating on the connection parts, which liquefies at a temperature in the range of the melting temperature of the melt conductor material. During the switching process, fusible link and coating mix and flow through the capillary volume due to pressure increase and capillary action. The effluent material of the fusible conductor and the coating thus accumulate at least partially in the outer region of the thermal fuse on the connection parts. The outdoor area is the area of the thermal fuse, which is not enclosed by an enclosure.

Preferably, the fusible conductor is in the thermal fuse such that it is in direct contact with the connection parts or in direct contact with a coating applied to the connection parts. The encapsulation or encapsulation may preferably have an additional varnish layer on the inside towards the fusible conductor.

Furthermore, it is preferred that the thermal fuse can have a flux similar to that used, for example, for soldering. The use of a suitable flux promotes the activation of the surface during the triggering process of the fuse and, when the melting temperature is reached, the mixing of the fusible conductor and the coating as well as the outflow of the material through the capillary. When selecting the flux, it is important to use a long-term stable flux, which ensures activation even after prolonged elevated temperature influence under operating conditions of typically 100-200 ° C. Even with the use of a flux, no free spaces are provided adjacent to the fusible conductor and / or flux. Preferably, the fusible conductor is located between the two electrically conductive connection parts. Thus, the Schmelzeiter is arranged in a gap between the connecting parts. In this case, the fusible conductor can be in direct contact with the connection parts or in direct contact with a coating provided on the connection parts. This has the advantage that during the tripping process when reaching a certain temperature, the separation of the circuit is performed by interrupting the electrical connection between the two connection parts.

Furthermore, it is preferred that the coating forming the capillary is formed by a galvanization of the two connecting parts. The material of this coating is preferably tin, indium, bismuth, silver or an alloy consisting of tin, indium, bismuth or silver. Such a coating promotes absorption of the fusible conductor upon reaching the melting temperature. In this case, the material layer between the connection parts and the encapsulation or cladding should preferably have a thickness of between 1 .mu.m and 50 .mu.m, more preferably between 5 .mu.m and 20 .mu.m.

In order to ensure a good aging stability of the thermal fuse, the coating of the connecting parts is preferably designed such that between the connecting parts and the encapsulation or coating, the coating, for example, the tin layer, a Unterickelung, wherein the Unterickelung of a pure nickel layer or of a nickel may consist of alloy. This nickel plating is thus an additional layer between the connecting parts and the coating, for example the tin layer. Thus, the nickel plating is in direct contact with the terminal part and the coating, eg the interest layer. In this case, the nickel plating serves as a barrier layer and forms a diffusion barrier between the connecting parts made of copper, for example, and the coating. Such a diffusion barrier prevents the formation of intermetallic phases. Thus, it is also ensured that, even after aging, there is still a sufficiently thick coating between the connection parts and the encapsulation or encapsulation, eg, a sufficiently thick tin layer for accommodating the fusible conductor and for triggering the fuse. The nickel layer, or nickel-containing Alloy may preferably have a thickness between 1 μιη and 50 μιη, more preferably between 5 μιη and 15 μιη.

Preferably, the fusible conductor consists of a conductive, low-melting metal, or a low-melting metal aufwei- send alloy whose composition is determined by the desired release temperature. Preferably, conventional solder alloys, e.g. Tin-silver solders, SnAgCu solders, lead solders or other solder alloys. The following table shows examples of possible compositions of the solder alloy as a function of the desired triggering temperature of the thermal fuse:

The alloy compositions listed in the table are only examples of solder alloys. Other alloy compositions could also be used.

Furthermore, an advantageous embodiment of the invention provides that the connection parts have the form of caps. It is preferred that the caps have a circular or circular-like cross-section and inside at least partially have a cavity. Similarly, it is further preferred that the connecting parts have the shape of a cuboid or a cuboid-like shape. The connecting parts form the basic body of the thermal fuse. This has the advantage that the thermal fuse can be configured as a surface-mountable component (SMD component) in the form of a flat fuse.

Other or further geometric configurations of the thermal fuse according to the invention are also possible.

It is also preferable for the electrically conductive connecting parts to accommodate at least one non-conductive body. In principle, each of the two connection parts could each accommodate one or more non-conductive bodies. In this case, the non-conductive body or bodies have e.g. the shape of the caps, so that they fill the inner, free space of the caps after assembly. In doing so, the one or more non-conductive bodies hold the electrically conductive connection parts, e.g. Caps in position. Furthermore, this has the advantage that the fusible conductor can be positioned and held by the insulating body in a suitable position between the electrically conductive connection parts. Furthermore, the one or more non-conductive bodies could have the shape of a cuboid or a cuboid-like shape, with the non-conductive body or bodies serving to support or hold the electrically conductive connection parts.

Similarly, it is further preferred that the one or more non-conductive body regardless of the geometric configuration of ceramic, z. B. Al ₂ 0 ₃ exist. In principle, the non-conductive bodies could also consist of another insulating material, eg glass, plastic or another organic material.

It is also preferable that the fusible conductor has the shape of a ring. The diameter of such a ring could, but need not necessarily, be selected according to the diameter of the caps. The use of an annular fusible conductor has the advantage that it can be held in a more simple manner between the two electrically conductive caps by the non-conductive body, eg ceramic body. Similarly, the ring could run around the non-conductive body from the outside. Furthermore, the fusible conductor could be in the form of one or more longitudinal strips be carried out with a certain projection between two parallelepiped connection parts. The fusible conductor is thus arranged at least partially between the cuboid or cap-shaped electrical connection parts. Furthermore, the fusible conductor can additionally be arranged at least in regions on the quasi-shaped or cap-shaped connecting parts.

Furthermore, an advantageous embodiment of the invention to provide the thermal fuse with suitable electrical connections by a wire or an electrical conductor in a wire-like shape, preferably in the middle, is connected to the two connection parts. Thus, it is possible to use the thermal fuse in conventional devices or savings without having to make structural changes to the electrical load or the device. Furthermore, the electrical connections can be designed in the form of an SMD (Surface Mounted Device) construction. Such an SMD component is used in electronics as surface-mountable component or component for surface mounting. Furthermore, connection forms for other types of mounting, e.g. Through-hole mounting (through hole technology), conceivable.

In order to ensure high mechanical protection, high mechanical stability and protection against oxidation of the thermal fuse, it is preferable to protect the thermal fuse by encapsulation or wrapping. The encapsulation or coating can be additionally combined with another protective coating to improve these properties.

Brief description of the drawings

The invention will now be described by way of example with reference to the accompanying drawings by way of particularly preferred embodiments.

In a purely schematic representation:

1 is a schematic representation of the thermal fuse (100) according to the invention,

2 is a schematic representation of the thermal fuse (200) according to the invention,

3 is a schematic representation of the switching principle of the thermal fuse according to the invention (100, 200, 300) before triggering, 4 shows a schematic representation of the switching principle of the thermal fuse (100, 200, 300) according to the invention when the melting temperature is reached,

5 is a schematic representation of the switching principle of the thermal fuse (100, 200, 300) after the tripping operation,

Fig. 6 is a schematic representation of the thermal fuse (300) according to the invention, and

Fig. 7 is a further schematic representation of the thermal fuse (300) according to the invention.

Preferred embodiment of the invention

Figure 1 shows a schematic representation of a thermal fuse 100 according to the invention. The thermal fuse 100 according to the invention consists of two caps 11 and 12 with centrally connected wire 14 and 15, a ceramic body 13 and a fusible conductor 10. To ensure a very good electrical conductivity, the two caps 11, 12 made of copper. Alternatively, the caps 11, 12 may be made of another material of low resistivity. The caps 11, 12 and the wires 14, 15 are coated with a coating (23), preferably an Sn layer. The coating could also comprise another material, for example indium, bismuth, silver, or an alloy consisting of tin, indium, bismuth or silver. Between the two caps 11, 12, a fusible conductor 10 is arranged, which is held by a ceramic body 13. The fusible conductor 10 has the shape of a ring and consists of a tin-silver alloy (eg Sn97 Ag3 with a melting point of 217 ° C). The alloy could also have a different composition with a lower or higher melting point, depending on the required fuse release temperature. On the fusible conductor 10 is a long-term stable flux 16, which serves during the triggering operation of the fuse to activate the surface and to reduce the surface tension. The encapsulation or encasing of the fuse, consisting here of a UV-curable varnish 17 and an epoxy resin-based molding material 18, serves to increase the mechanical stability of the fuse. In addition, the encapsulation or sheath 17, 18 provides mechanical and oxidation protection. The wrapping ment 18 encloses the thermal fuse only in certain areas. In particular, the sheath 18 surrounds the thermal fuse in the region in which the fusible conductor 10 is arranged. The ends of the caps 11, 12, in particular in the region of the connection points, for example for the wires 14, 15 are not enclosed by the sheath 18.

Figure 2 shows a schematic representation of a thermal fuse 200 according to the invention. The thermal fuse 200 consists essentially of the components of the thermal fuse 100 described in Figure 1. An essential difference from the structure described in Figure 1 shows that the thermal fuse 200 in Figure 2 no Flux application on the fuse element 10 has.

Figures 3 to 5 show schematic representations of the switching principle of the thermal fuse 100, 200, 300 according to the invention before reaching the melting temperature, upon reaching the melting temperature and after reaching the melting temperature.

FIG. 3 shows the state before triggering the thermal fuse 100, 200, 300 or before reaching the melting temperature. Before reaching the melting temperature, the fusible conductor 10 is in a fixed state in the gap 24 between the connection parts 11, 12 with the coating 23 and the encapsulation or enclosure 18. For the tripping operation of the thermal fuse 100, 200, 300, in particular the pressure gradient by one hand Volume increase and volume jump in the transition from the solid to the liquid phase and the capillary action of importance.

FIG. 4 shows the state of the thermal fuse 100, 200, 300 when the melting temperature is reached. Upon reaching the melting temperature of the fusible conductor 10 begins to melt. When the fusible conductor melts, the coating 23 'also melts in the region of the encapsulation or encapsulation, as a result of which the fusible conductor 10 and the coating 23' at least partially mix. The displacement into and through the capillary is significantly caused by the increase in pressure at the phase transition of the fuse element 10 from solid to liquid and the associated volume jump. FIGS. 4 to 5 show the emigration of the fusible conductor 10 during melting and after triggering. For better illustration, FIG. 22 of the fusible conductor during emigration. It can be seen that the fusible conductor 10 completely emanates from the gap 24.

FIG. 5 shows the switching state of the thermal fuse 100, 200, 300 after the tripping operation and the complete emigration of the melt luster 10 out of the gap 24. After the tripping process has been completed, the coating 23 "mixed with the fusible conductor solidifies and settles on the connecting parts After completion of the tripping operation and the outflow of the fusible conductor 10, the flow of current through the thermal fuse 100, 200, 300 through the gap at the gap between the two conductive connection parts 11, 12 or basic bodies 19 interrupted.

FIGS. 6 and 7 show schematic illustrations of a thermal fuse 300 according to the invention. The thermal fuse 300 according to the invention is designed as a flat fuse for surface mounting (SMD construction). The thermal fuse 300 according to the invention consists of two spaced-apart basic bodies 19 (connection parts), which are applied to a non-conductive body 13, for example a ceramic body. To ensure a very good electrical conductivity, the two main body 19 (connecting parts) made of copper or other material with low resistivity. The two base bodies 19 (connection parts) are coated with a coating 23, preferably as a tin layer. The coating could also comprise another material, eg indium, bismuth, silver or an alloy consisting of tin, indium, bismuth or silver. Furthermore, the thermal fuse 300 has a fusible conductor 10 between the two base bodies 19 (connection parts) and in the area around the intermediate space (gap (24)) between the two base bodies 19 (connection parts). As shown in FIG. 8, the thermal fuse 300 has two fuse elements 10. The fuse could also have one or more than two fuse element 10. On the fusible conductor 10 is a long-term stable flux 16, which serves during the triggering operation of the fuse to activate the surface and to reduce the surface tension. Between encapsulation or wrapping 18 of the fuse and the flux is an additional coating layer 17. The encapsulation or sheath 18 can only be applied on top of the thermal fuse. The encapsulation or coating 18 and the additional paint layer 17 serve to increase the stability of the fuse and the oxidation protection. The lacquer layer 17 is in direct contact with the flux 16 without releasing a gap. The thermal fuse 300 could also be configured such that it has no flux 16 on the fusible conductor 10. In this case, the lacquer layer 17, or in the absence of an additional lacquer layer 17, the encapsulation 18 would be in direct contact with the fusible conductor 10 without the release of a gap.

reference numeral

100 thermal fuse

200 thermal fuse

300 thermal fuse

10 fusible link

11, 12 connecting parts / caps

13 electrically non-conductive body

14, 15 wire

16 fluxes

17 Paint cover / paint coating

18 serving / encapsulation

19 basic body

22 flow direction

23 coating / tin layer

23 'coating (melted)

23 "coating (solidifies tin layer with fused solder material)

24 gap

Claims

claims

1. thermal fuse (100, 200, 300), which performs the separation of a circuit during melting of a fusible conductor (10), wherein the thermal fuse at least two electrically conductive connection parts (11, 12) and a fusible conductor (10), characterized characterized in that the thermal fuse comprises an encapsulation or sheath (18), wherein the thermal fuse or its layer structure at least one coating (23) between the connecting parts (11, 12) and the encapsulation or sheath (18) up, wherein the thermal fuse is enclosed at least partially by the encapsulation or sheath (18), wherein the fusible conductor (10) is encapsulated within the thermal fuse.

2. Thermal fuse according to claim 1, characterized in that the fusible conductor (10) in direct contact with the connecting parts (11, 12) and the encapsulation or sheath (18).

3. Thermal fuse according to at least one of the preceding claims, characterized in that the encapsulation or sheath (18) has a lacquer layer on the inside to the fusible conductor (10).

4. thermal fuse according to at least one of the preceding claims, characterized in that the thermal fuse comprises a flux (16).

5. thermal fuse according to at least one of the preceding claims, characterized in that the fusible conductor (10) between the two connection parts (11, 12).

6. Thermal fuse according to at least one of the preceding

Claims, characterized in that the coating (23) between the connecting parts (11, 12) and the encapsulation or sheath (18) tin, indium has bismuth or a tin alloy, indium alloy or bismuth alloy.

7. thermal fuse according to at least one of the preceding claims, characterized in that the coating (23) between the

Connecting parts (11, 12) and the encapsulation or sheath (18) has a thickness between 1 μιη and 50 μιη, preferably between 5 μιη and 20 μιη having.

A thermal fuse according to at least one of claims 5 to 11, characterized in that the coating (23) between the terminal parts (11, 12) and the encapsulation or cladding (18) has an under nickelation, the nickel oxide being a nickel layer or a nickel consisting of alloy.

9. thermal fuse according to claim 8, characterized in that the lower nickel has a thickness between 1 μιη and 50 μιη, preferably between 5 μιη and 15 μιη having.

10. Thermal fuse according to at least one of the preceding claims, characterized in that the fusible conductor (10) consists of a low-melting metal, a low-melting metal alloy or a lead solder.

11. Thermal fuse according to at least one of the preceding claims, characterized in that the fusible conductor (10) consists of a

Tin silver alloy exists.

12. Thermal fuse according to at least one of the preceding claims, characterized in that the connection parts (11, 12) have the shape of caps.

13. Thermal fuse according to at least one of claims 1 to 11, characterized in that the connection parts (11, 12) have the shape of a cuboid or a parallelepiped shape.

14. Thermal fuse according to at least one of the preceding

Claims, characterized in that the thermal fuse has at least one electrically non-conductive body (13), said at least one electrically non-conductive body (13) for holding the connecting parts (11, 12).

15. Thermal fuse according to claim 14, characterized in that the at least one electrically non-conductive body (13) made of ceramic, glass, plastic or of another organic material.

16. Thermal fuse according to at least one of the preceding

Claims, characterized in that the fusible conductor (10) has the shape of a ring.

17. Thermal fuse according to at least one of the preceding claims, characterized in that at the connection parts (11, 12) in each case an electrical conductor (14, 15) is connected.

18. Thermal fuse according to at least claim 17, characterized in that the electrical conductor (14, 15) has the shape of a wire or a wire-like shape.

19. Thermal fuse according to at least one of the preceding claims, characterized in that the thermal fuse has a paint cover or a Lackumhüllung.

20. Use of a thermal fuse according to at least one of the preceding claims as a fuse for securing solar cells, high energy battery cells, additional heaters, electrical consumers especially in vehicles, as well as to protect against overheating and fire protection.