EP1173871A1

EP1173871A1 - Semiconductor power component comprising a safety fuse

Info

Publication number: EP1173871A1
Application number: EP01919115A
Authority: EP
Inventors: Martin Haupt; Herbert Labitzke; Walter Csiscer; Klaus-Uwe Mittelstaedt; Hans-Heinrich Winkel; Holger Scholzen; Karl-Otto Heinz; Holger Haussmann; Henning Stilke; Hermann Lehnertz
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2000-02-17
Filing date: 2001-01-26
Publication date: 2002-01-23
Also published as: JP2003523704A; DE10190534D2; WO2001061718A1; DE10007209A1; AU4635301A; US6667532B2; ZA200108496B; US20020158304A1; MXPA01010499A; BR0104489A; CN1363106A

Abstract

The invention relates to a semiconductor power component (diode 18) comprising a lead (11) and a safety fuse (12) that is situated in the principal current path. Said fuse comes into action when there is thermal overstress and is especially used in the electric system of motor vehicles. The aim of the invention is to specifically switch off the endangered component when the semiconductor power components are overstressed, for preventing sequential damages, whereby switching-off is predetermined. A partial section (11b) of the lead (11) and/or the points of contact thereof in the principal current path of the semiconductor is/are designed as a safety fuse (12) which comes into action when there is a predetermined, current-dependent temperature value.

Description

Semiconductor power component with fuse

The invention relates to a semiconductor power component with a fuse in its main current path according to the preamble of the main claim.

State of the art

The electrical semiconductor power components currently used, such as diodes, Zener diodes or transistors, can alloy due to manufacturing defects, electrical overload or thermal overload on their switching path and thus lead to an electrical short circuit. In the case of rectifier arrangements on three-phase generators in motor vehicle construction, short-circuits can also occur as a result of batteries connected with polarity reversal or through a battery charger connected with polarity reversal, which leads to an impermissibly high current in the main current path of the semiconductor power components. In most cases, the short-circuit current leads to after a short time

Destruction of the semiconductor power components as well as surrounding components, for example the supply lines or covers. In extreme cases, such events can also result in overheating with consequential damage in the motor vehicle arise before the overcurrent is interrupted by the destruction of the semiconductor.

Fuses may be used to protect semiconductors. Commercial fuses, which can basically be connected electrically in series with the semiconductor power components, require a special installation space with the corresponding design effort. They also result in an electrical series resistance that generates current-dependent heat loss.

From DE 30 01 52 2 C2 it is already known to arrange a fuse element in each case in a rectifier arrangement between the connections of the plus and minus power diodes of the rectifier bridges. The fuses are formed by loop sections which are bent out of recesses in a circuit board of the rectifier arrangement and which melt in the event of an electrical overload. Due to the

Manufacturing tolerances, however, result in inadmissibly large differences in the response characteristics of such fuses, so that they are unsuitable, at least for generators with a high power density.

The present invention strives to integrate a fuse against electrical or thermal overload in semiconductor power components, which is as simple as possible to manufacture and reliable in response to a predetermined temperature limit. Advantages of the invention

The semiconductor power component according to the invention with the characterizing features of the main claim has the advantage that neither an additional component nor an additional space but only a small additional material expenditure is required by the design of the semiconductor connecting wire or its contact points as a fuse. Another advantage is that no additional resistance with additional heat loss has to be inserted in the main current path of the semiconductor power component with the fuse.

Advantageous further developments and refinements result from the other features mentioned in the subclaims. Since the thermal load on transistors is generally to be limited by controlling the current intensity through the power transistor itself, the proposed solution is expediently used for passive ones

Semiconductors, preferably used in diodes or Zener diodes. Their use is particularly suitable for passive semiconductors in a bridge rectifier of a three-phase generator for motor vehicles. There is the semiconductor power device that with its

Connection wire facing further connection consists in a conventional manner from a metal housing, fixed in a heat and flow conductive heat sink.

A particularly simple and reliable solution results from the fact that the section of the connecting wire designed as a fuse or its contact points is embedded in a current and heat insulating, temperature-resistant material. In the specific case, the rectifier power component can can be upgraded with a fuse immediately after its manufacture, by covering the contact area of the semiconductor with the connecting wire, also called head wire, with a silicone sealing compound. Alternatively, however, the upper end of the connecting wire, namely its contact area with a connecting conductor in the main current path, can be covered by a silicone sealing compound. This is particularly advantageous for subsequent protection, for example in the case of bridge rectifiers

Three-phase generators of motor vehicles. In terms of assembly technology, however, it is particularly advantageous if the middle section of the connecting wire lying between the two ends is surrounded by a sleeve, preferably made of ceramic, to form the fuse. In order to adequately secure them against shaking stress, it is advantageous if the sleeve is pushed onto the connecting wire in a clamped manner.

A sophisticated and targeted switch-off of responsive to a pre-determinable temperature limit

Overcurrents can be realized by a solution in which the middle section of the connecting wire is designed as a fuse with a two-stage response characteristic. The middle section of the connecting wire is expediently reduced in cross-section by plastic deformation to form a first resistance element and connected in parallel to a second resistance element, the melting temperature of which is lower than that of the connection wire. A solution that is particularly simple to manufacture provides that the central section of the connecting wire is deformed in a semicircular shape and that the second resistance element is inserted in the semicircular shape formed thereby. In a particularly expedient manner, the second resistance element consists of tin, which in a solder bath is washed into the semicircular space. A precise metering of the material accumulation and material distribution can advantageously be achieved in that the second resistance element is a solder pill made of tin of a predetermined size, which is soldered into the shape of the middle section. Alternatively, depending on the required response of the fuse, the second resistance element can also be a zinc disk, which is soldered into the shape of the central section by means of a solder bath. A round wire made of copper is expediently used for the connecting wire.

In each of these cases, the predetermined melting temperatures of the two resistance elements ensure that when the semiconductor power component is overloaded, the second resistance element made of tin or zinc melts, causing the current in the remaining first resistance element to increase so much that this resistance element also immediately thereafter melts and interrupts the main current path. In order to avoid an increase in the electrical resistance of the fuse compared to the original connecting wire, the shape and material selection of the two resistance elements of the

The fuse ensures that it has an overall electrical resistance that is no greater than that of an undeformed connecting wire of corresponding length.

drawings

Further details of the invention are explained in more detail in the exemplary embodiments described below with reference to the associated drawing. Show it: 1 shows the circuit diagram of a semiconductor power component with a fuse integrated according to the invention, FIG. 2 shows the circuit diagram of a three-phase generator with a bridge rectifier, FIG. 3 shows the structural design of a bridge rectifier from FIG. 2 for motor vehicles in a top view, FIG Figure 3, Figure 5 as a second embodiment, a partial cross section through a rectifier according to Figure 3, Figure 6, a third embodiment with a partial section through a

Rectifier according to FIG. 3, FIG. 7 the equivalent circuit diagram for a two-stage fuse as a fourth exemplary embodiment, FIG. 8 the enlarged representation of the two-stage fuse and FIG. 9 a further partial cross section through a rectifier according to FIG. 3 with the two-stage fuse according to FIG. 8.

Description of the embodiments

FIG. 1 shows the circuit diagram of a semiconductor power component 10, in the connecting wire 11 of which a fuse 12 is integrated. In the event of a thermal overload, the fuse 12 is intended to reliably interrupt the main current path when a predetermined current-dependent temperature limit value is reached. Passive semiconductors, such as diodes and zener diodes, are particularly at risk here, the current strength of which in the main current path cannot be limited via a control path of the power component. The use of such semiconductor devices is particularly critical.

Power components in motor vehicles, since in addition to the destruction of the semiconductor element itself, surrounding components can also be destroyed, and in extreme cases further thermal damage can occur. FIG. 2 therefore shows the circuit diagram of a motor vehicle three-phase generator 14 with an attached bridge rectifier 15, the rectifier bridges 16 of which each have a plus diode 17 and a minus diode 18 in series therewith. The generator windings 19 connected in a star are connected at one end to one of the three rectifier bridges 16. The positive diodes 17 are connected to a positive terminal 20 on the cathode side and the negative diodes 18 are connected to a ground terminal 21 on the anode side. Both connections 20 and 21 are connected to the accumulator battery 22 via the electrical system of a motor vehicle. The plus and minus diodes 17, 18 each form a semiconductor power component in the form of a zener diode. In a manner known per se, it consists of an electrically conductive metal housing with an encapsulated semiconductor chip inside. One connection is formed in a head wire contacted with the chip and the other connection is formed by the electrically conductive metal housing, which is pressed into a heat sink. The head wire represents the connecting wire 11 from FIG. 1, which is supplemented by the fuse 12.

Various embodiments of the bridge rectifier 15 are shown in FIGS. 3 to 6 and 9. FIG. 3 shows the top view of the bridge rectifier 15, it being recognizable in connection with FIG. 4 that the plus diodes 17 are pressed into a plus heat sink 25 and the minus diodes 18 are pressed into a minus heat sink 26. In a circuit board 27 made of plastic, connecting conductors 28 are embedded, which connect the plus diodes 17 on the anode side to the cathode-side connection of the minus diodes 18 and with one winding end of the three-phase generator 14 to form a rectifier bridge 16. The connecting conductors 28 are each in their connection areas bent into a loop 29, which protrude radially laterally from windows 30 of the circuit board 27 or on the outside thereof. In the loops 29, the connecting wires 11 of the diodes 17, 18 or the ends of the generator winding 19 are contacted by squeezing, welding or soldering. The minus heat sink 26 is isolated by an insulating part 31 from the plus heat sink 25 arranged above it.

The cross section shown in Figure 4 by the

Rectifier according to FIG. 3 shows a plus diode 17 and a minus diode 18, in which the contact area 32 of the semiconductor encapsulated in the metal housing 33 is covered with a silicone potting compound 34 with the lower end of the connecting wire 11. This potting compound 34 is a temperature-resistant, non-combustible, electrical and thermal insulation of the contact area 32, which is thus designed as a fuse element that melts away at a predetermined response value of the current and thus interrupts the main current path of the diode 17, 18. If the contact area 32 heats up gradually, however, the heat is dissipated to the heat sink 25, 26 via the casting compound 34. This results in an approximately constant diode temperature in the permissible operation of the bridge rectifier 15. At a

Short circuit or a corresponding trigger event, however, the heat generated in the contact area 32 cannot be sufficiently dissipated by the casting compound 34, so that the contact area 32 burns out and the current path is opened. Thus, everyone is inflated to one

Cases of overheating of endangered components of the bridge rectifier 15 lying in the region of the diodes can be reliably prevented. FIG. 5 shows, in a second exemplary embodiment of the invention, a cross section through the part with the positive diode 17 of the bridge rectifier 15 according to the section AA ′ from FIG. 3, the same parts being provided with the same reference numbers. There forms a squeeze and

Welded connection 36 at the upper end of the connecting conductor 11 with a loop 29 of the connecting conductor 28 in the circuit board 27, a contact area 36a in the main current path 13 of a rectifier bridge 16, which is embedded in a sealing compound 34a made of silicone. Here, too, the thermal insulation of the contact region 36a forms it as a fuse, which melts when a predetermined, maximum permissible current is exceeded and thus interrupts the main current path of the semiconductor power component. In normal operation, however, the temperature of the contact area 36 increases only slightly due to the sealing compound 34a and the contact resistances there, so that this remains uncritical due to the selection of the suitable sealing compound and its dosage. In the event of an electrical overload, however, the potting compound 34a causes an accumulation of heat, which causes the contact area 36a to melt away.

In a third exemplary embodiment, FIG. 6 shows a cross section through the part with the minus diode 18 of the bridge rectifier 15 according to AA ^λ from FIG. 3, the same parts also being provided with the same reference numbers here. In this solution, a section 11a of the connecting wire 11 is designed as a fuse, in that this middle section lying between the two ends is surrounded by a thermally insulating sleeve 37. A ceramic or a plastic made of thermosetting material can be used as the temperature-resistant material. The sleeve 37 can be loosely on the The connecting wire 11 must be pushed on, so that in the event of a trip, if the maximum permissible current is exceeded, this section 11a of the connecting wire can melt away and thus interrupt the main current path of the plus diode. To avoid damage to the connecting wire

Shaking stresses, however, the bore 38 of the sleeve 37 is formed narrower in the upper region, so that it is pushed there clampingly on the connecting wire.

In a fourth exemplary embodiment, provision is made for the central section 11b of a semiconductor power component 10 used as a plus or minus diode to be designed as a fuse 12 with a two-stage response characteristic.

FIG. 7 shows the equivalent circuit diagram for this, the middle section 11b of the connecting wire 11 being designed to form a first resistance element 40, to which a second resistance element 41 with a lower melting temperature is connected in parallel. The shape and material selection of the two resistance elements 40, 41 of the fuse 12 achieve an overall electrical resistance which is not greater than that of a straight connecting wire of corresponding length. This results in the semiconductor power component 10 through the

Integration of the two-stage fuse 12 no increase in resistance and thus no increase in power loss.

Such a connecting wire 11 of a two-stage fuse 12 can be seen in FIG. 8 in a greatly enlarged illustration. The central section 11b of the connecting wire 11 is reduced in cross section here by plastic deformation to the first resistance element 40 and is bent in a semicircular shape. In the so formed semicircular shape 42, the second resistance element 41 is used. The second resistance element 41 here consists of a zinc disk, which is soldered into the formation 42 of the central section 11b on the connecting wire 11 in a solder bath.

As an alternative to this, it is also possible to design the shape of the connecting wire 11 such that a sufficient amount of tin accumulates in a solder bath instead of the zinc disk, which then forms the second resistance element 41 after cooling. Finally, it is also possible to solder a metered amount of tin into the shape 42 in the form of a solder pill of a predetermined size. In all cases, a wire made of copper is provided for the connecting wire 11. However, the use of a connecting wire 11 with a copper surface is also conceivable.

Finally, in FIG. 9 a section of a bridge rectifier according to A-A * from FIG. 3 shows a minus diode 18 with a fuse 12 according to FIG. 8 in its connecting wire 11.

By reducing the cross-section of the connecting wire 11 in its middle, small section 11b, its electrical resistance per unit length can be adjusted, to be greater than that of the undeformed connecting wire 11.

However, its melting temperature is higher than that of the second resistance element 41. If the current in the main current path of the minus diode 18 is inadmissibly high, the second resistance element 41 thus melts due to the lower melting temperature. Then the total current from the first

Resistor element 40 is taken over, then immediately melts the section 11b of the lead wire 11 and turns off the current of the minus diode 18. In the example, the zinc disk of the first resistance element 41 soldered in by a solder bath has one Melting temperature of about 420 ° C and a specific resistance of about 0.0625 Ωmm ^ / m. When using tin as the second resistance element, the melting temperature is about 232 ° C .; the specific resistance is approximately 0.1150 Ωmm ^ / m. The connecting conductor 11 from

Round copper wire has a melting temperature of about 1083 ° C and a specific resistance of 0.0179 Ωmm ^ / m.

When using the integrated fuse in all six semiconductor power components one

Rectifier bridge of three-phase generators for motor vehicles results in a further advantage that the Zener diodes are selectively switched off in the event of overcurrent, so that a further supply of the motor vehicle electrical system is possible - albeit with limited power and voltage quality. The motor vehicle is thus not only protected against consequential damage, but is also temporarily ready to drive in order to be able to go to a workshop.

Claims

Expectations

1. Semiconductor power component (10) with a connecting wire (11) in its main current path (13) and with a lying in the main current path, responsive to thermal overload fuse (12), preferably for use in the electrical system of motor vehicles, characterized in that a Section (11a; 11b) of the connecting wire (11) and / or its contact points (32; 36) in the main current path (13) is designed as a fuse (12) which responds to a predetermined, current-dependent temperature value.

2. Semiconductor power component according to claim 1, characterized in that it is a passive semiconductor, preferably a diode or zener diode (17, 18).

3. Semiconductor power component, characterized in that the passive semiconductors (17, 18) are used in a bridge rectifier (15) of a three-phase generator (14) for motor vehicles.

4. Semiconductor power component according to one of claims 1 to 3, characterized in that it with its connection wire (11) facing further connection consists in a conventional manner from a metal housing (33) which in a heat sink (25, 26) is attached to flow and heat conduction.

5. Semiconductor power component according to one of the preceding claims, characterized in that the section (11a; 11b) of the connecting wire (11) and / or its contact points (32, 36) formed as a fuse (12) in a current and heat insulating, temperature-resistant material (34) is embedded.

6. A semiconductor power component according to claim 5, characterized in that the contact point (32) of the semiconductor element (35) with the connecting wire (11) is covered by a sealing compound (34), preferably made of silicone.

7. A semiconductor power component according to claim 5, characterized in that the contact point (36) of the

Connection conductor (11) with a connecting conductor (28) in the main current path (13) is covered by a casting compound (34a), preferably made of silicone.

8. A semiconductor power component according to claim 5, characterized in that the intermediate portion (11a) of the connecting wire (11) lying between the two ends is surrounded by a sleeve (37), preferably made of ceramic.

9. A semiconductor power component according to claim 8, characterized in that the sleeve (37) is pushed onto the connecting wire (11) in a clamping manner.

10. Semiconductor power component according to one of claims 1 to 4, characterized in that the central section

(11b) of the connecting wire (11) is designed as a fuse (12) with a two-stage response characteristic.

11. A semiconductor power component according to claim 10, characterized in that the central portion (11b) through plastic deformation into a first resistance element

(40) reduced in cross section and connected in parallel to a second resistance element (41), the melting temperature of which is lower than that of the connecting wire (11).

12. Semiconductor power component according to claim 10 or 11, characterized in that the shape and material selection of the two resistance elements (40, 41), the fuse (12) has an overall electrical resistance which is not greater than that of a connecting wire (11) appropriate length.

13. A semiconductor power component according to claim 12, characterized in that the central section (11b) is deformed in a semicircular shape and that in the formation (42) thereby formed, the second resistance element

(41) is arranged.

14. The semiconductor power component as claimed in claim 13, characterized in that the second resistance element (41) is a zinc disk which is soldered into the formation (42) of the central section (11b) by means of a solder bath.

15. A semiconductor power component according to claim 13, characterized in that the second resistance element (41) consists of tin.

16. A semiconductor power component according to claim 15, characterized in that the tin of the second

Resistance element (41) is soldered into the shape (42) of the central section (11b) as a predetermined size solder pill.

17. Semiconductor power component according to one of the preceding claims, characterized in that the connecting wire (11) is a round wire made of copper.