DE102004021862A1 - Current sensor has two lead frames each having a magnetic field sensor chip that are attached to the frame opposite one another - Google Patents

Abstract

A current sensor comprises two lead frame (L1,L2) parts of a current conductor each having a magnetic field sensor chip (IC1,IC2) on one side. The two opposing sides of the lead frames are back-to-back so that the chips are opposite one another. Independent claims are also included for the following: (A) a production process for the above;and (B) an operating process for the above.

Description

The The present invention relates to the field of semiconductor sensor technology and in particular, the present invention relates to a Magnetic field sensor, facing make the prior art easier.

Around a magnetic field of a current-carrying conductor contactless to be able to measure can Special magnetic field sensors are used in a given Position are arranged with respect to the conductor. It can the Head can also be used as a leadframe and a magnetic field component evaluated parallel to the conductor surface (eg with a GMR or a vertical Hall probe). Further can be the measurement of external interference fields remain unaffected, including the field above and below the conductor strip (that is the Leadframe) is measured. In both places the field has different things Sign, so that its amount doubles by subtraction. foreign fields however, are in good approximation homogeneous, so that they are cut out by the subtraction.

Such a problem has already been dealt with in the German patent application 10315532.5. In this patent application it has been suggested that two magnetic field sensor chips 502 and 504 on the same leadframe 506 can be mounted as it is in 5 is shown. The first magnetic field sensor chip 502 in this case, for example, by an adhesive layer 508 at the lead frame 506 attached while the second magnetic field sensor chip 504 through a second adhesive layer 510 at the lead frame 506 is attached. The first magnetic field sensor chip 502 is through a first bonding wire 512 with an external pin 514 while the second magnetic field sensor chip 504 by means of a second bonding wire 516 either with the external one 514 or one from the external pin 514 electrically separated and perpendicular to the plane set further pin (which is not shown here) is connected. Many application-specific details have already been given in the aforementioned patent application and are hereby incorporated by reference. In particular, reference should be made to an essential aspect, which is important in the present patent application, namely that it is possible to create a way of making electrical connections between the two chips. In the aforementioned patent application, "internal pins" were introduced. A disadvantage of the aforementioned patent application proves that the assembly technique for such a current sensor differs significantly from existing facilities and therefore cumbersome, costly, risky and time consuming.

• a) Beide Chips werden zugleich (d.h. simultan) auf der Leadframe-Ober- und -Unterseite befestigt, so dass beide Kleber/Lote zugleich aushärten. Während des Aushärtens darf sich dabei die Lage der Chips gegenüber dem Leadframe nicht unzulässig ändern. Dadurch, dass die Chips gleichzeitig zu beiden Seiten des Leadframes befestigt werden, kann dies ein schwieriges Problem darstellen. Herkömmlicherweise liegt der Chip auf dem Leadframe, so dass eine Position durch die Schwerkraft nicht verändert wird. Wenn nun allerdings der zweite Chip auf der Leadframe-Unterseite liegt, so kann es bei schlecht gewählten Prozessparametern dazu kommen, dass sich seine Lage während des Aushärtens ändert. Alternativ kann man aber das Leadframe während des Aushärtens auch senkrecht stellen, so dass beide Chips die Schwerkraft in derselben Richtung (parallel zur Chipebene bzw. Lötfläche/Klebefläche) wird. Die Chips werden solange gehalten, bis das Lot/der Kleber zu Folgeabkühlung hinlänglich zäh wird, so dass sich die Lage der Chips auch dann nicht mehr ändert, wenn sie losgelassen werden.
• b) Die Chips werden zeitlich hintereinander am Leadframe befestigt, wobei man zwei Kleber/Lote verwenden muss, die unterschiedliche Aushärtungs- bzw. Erweichungstemperaturen haben. Zuerst wird dann ein Chip mit jenem Kleber/Lot befestigt, das die höhere Verarbeitungstemperatur benötigt, danach wird der andere Chip mit einem Kleber/Lot befestigt, dessen Verarbeitungstemperatur hinreichend niedrig ist, so dass die erste Kleb/Lötstelle nicht unzulässig erweicht wird.

Furthermore, in the DE 19815906 A1 discloses a package for power semiconductors comprising a chip on a leadframe (= leadframe) with multiple leads (= conductors), wherein the chip is connected to one or more bond wires to individual ones of the leads. By attaching two chips on opposite sides of the lead points in the DE 19815906 A1 Power semiconductors again revealed the disadvantage that both the chip on the leadframe bottom and those on the leadframe top must be attached to the leadframe. Usually, hard or soft solders or adhesives are used to secure the chips to the conductors. Such chip mounting on the top and bottom of leadframes raises the problem that the process of attaching the chips must not interfere with the adhesion of the other chip to the same leadframe. There are the following options:

• a) Both chips are attached simultaneously (ie simultaneously) to the leadframe top and bottom so that both adhesives / solders cure at the same time. During curing, the position of the chips relative to the leadframe may not change inadmissibly. The fact that the chips are attached to both sides of the leadframe at the same time can be a difficult problem. Conventionally, the chip is located on the leadframe, so that a position is not changed by gravity. If, however, the second chip is located on the bottom side of the leadframe, it may happen that the situation changes during hardening in the case of poorly selected process parameters. Alternatively, however, one can also set the leadframe vertical during curing so that both chips become the force of gravity in the same direction (parallel to the chip plane or soldering surface / bonding surface). The chips are held until the solder / adhesive becomes reasonably choppy for follow-up cooling, so that the location of the chips does not change even when released.
• b) The chips are attached one after the other to the leadframe using two adhesives / solders having different curing and softening temperatures, respectively. First, a chip is attached with that glue / solder that needs the higher processing temperature, then the other chip is attached with an adhesive / solder, the processing temperature is sufficiently low, so that the first adhesive / solder joint is not unduly softened.

Furthermore, the disclosure US 5783463 A a semiconductor element, in which again a first semiconductor chip is mounted on an upper side of a leadframe is arranged while a second semiconductor chip is disposed on a bottom of the leadframe. With such an arrangement, the aforementioned problem of fixing the two chips on the two sides of the leadframe arises again, which again makes the production process of such a semiconductor element more difficult.

The The object of the present invention is to provide a current sensor, a method for manufacturing a current sensor and a method for To operate a current sensor, wherein the current sensor across from make the prior art easier.

These The object is achieved by a current sensor according to claim 1, a method for producing a current sensor according to claim 13 and a method for operating a current sensor according to claim 16.

The present invention provides a current sensor device having the following features:
a first lead frame having a first region with a current conductor;
a first magnetic field sensor disposed on the first region on a first side of the first lead frame;
a second lead frame having a second region with a current conductor;
a second magnetic field sensor disposed on the second region of a first side of the second lead frame; and
wherein second sides of the lead frames facing the first sides thereof are arranged facing each other, such that the magnetic field sensors are arranged substantially opposite to each other.

Further, the present invention provides a method of manufacturing a current sensor, comprising the steps of:
Providing first and second leadframes, the first leadframe having a first region with a current conductor and the second leadframe having a second region with a current conductor;
Arranging a first magnetic field sensor on the first region on a first side of the first lead frame;
Arranging a second magnetic field sensor on the second region on a first side of the second lead frame; and
Arranging second sides of the lead frames opposed to the first sides thereof such that the second sides are aligned facing each other and the magnetic field sensors are arranged substantially opposite to each other to make the current sensor.

Further, the present invention provides a method of operating a current sensor, wherein the current sensor comprises a first lead frame having a first region with a current conductor, a first magnetic field sensor chip disposed on the first region on a first side of the lead frame, a second lead frame comprising a second region having a current conductor, a second magnetic field sensor chip disposed on the second region of a first side of the second lead frame, and second faces of the lead frames facing the first sides thereof facing each other, in that the magnetic field sensor chips are arranged substantially opposite one another, the method for operating the current sensor having the following steps:
Applying a current to the first lead frame or the second lead frame; and
Detecting a signal of the first magnetic field sensor chip or the second magnetic field sensor chip.

Of the The present invention is based on the finding that first the first magnetic field sensor mounted on a first side of the first lead frame is then the second magnetic field sensor in a conventional manner on the first Side of the second lead frame is mounted and then both lead frames with the back, i.e. second sides, which are opposite to the first sides, fixed to each other become. This means in particular that the ladder frames in one Position are brought where the sides on which the magnetic field sensors are not are mounted, facing each other. For a protection of the first and be able to provide second magnetic field sensor, the two can be Magnetic field sensors prior to aligning the second sides of the lead frames for example, by an encapsulation in a potting compound to secure. Alternatively, this fixing can be done by, for example Stick with a conductive or insulating adhesive or realized by further potting become.

In operation, current is then sent through the two lead frames, the current generating tangential fields on the surface of both magnetic field sensors. The magnetic field sensors can then be interconnected via internal or external pins, for example, so that they subtract external fields and add fields generated by the current flow through one or both leadframes. The essential finding of the present invention is therefore that a total signal, which results from a proportion of signals of the first magnetic field sensor and a proportion of signals of the second magnetic field sensor, regardless of the distribution of the current to the first or second lead frame is.

preferred embodiments The present invention will be described below with reference to the accompanying Drawings closer explained.

It demonstrate:

1A a representation of a magnetic field, as it forms in a current flow through a lead frame;

1B a representation of two juxtaposed lead frame with appropriately arranged magnetic field sensors;

2 an intermediate step of an embodiment of the method according to the invention for producing a current sensor;

3 a first embodiment of a current sensor according to the invention;

4 a further embodiment of a current sensor according to the invention; and

5 a representation of a conventional current sensor.

In the following description of the preferred embodiments of the present invention are for those in the various Drawings shown and similar acting elements same or similar Reference numeral used, with a repeated description of this Elements is omitted.

With the help of 1A and 1B it should be proved at this point that a signal output by the current sensor is independent of the distribution of a current on the first or second lead frame. This statement is an essential aspect that decisively influences the practical embodiment of the present invention. Since the two lead frames are very low impedance, contact resistance between the two lead frames can not be neglected. They cause the total current not to divide equally (ie 50% of the total current in the first lead frame and 50% of the total current in the second lead frame) on the first and second lead frames. Further, since the contact resistance may have a different temperature response than the resistance of the lead frame material, the current split also changes over temperature, so that a serious problem could arise for the accuracy of these current sensors.

In the following, therefore, it is shown that the current distribution due to the symmetry of the magnetic field leads to no impairment of the accuracy. The magnetic field of a lead frame L1, whose cross section in 1A is shown, the following symmetry condition suffices: B _y (-x ', y') = - B _y (X ', y') for all x 'and y'. The current flows from the in 1A out of the drawing plane. Note that the coordinate system x 'and y' is at the center of the in 1A shown conductor L1 is arranged.

B1

y-Komponente am Ort des ersten Magnetfeldsensors (das heißt am ersten Chip IC1 am ersten Leiterrahmen L1),

B2

y-Komponente am Ort des zweiten Magnetfeldsensors (das heißt am zweiten Chip IC2 am zweiten Leiterrahmen L2),

I₀

Gesamtstrom durch beide Leiterrahmen L1 und L2,

k·I₀

Strom durch den Leiterrahmen 1,

(1–k)·I₀

Strom durch den Leiterrahmen L2,

d

Chipdicke,

t

Leiterrahmendicke des ersten Leiterrahmens L1 und des zweiten Leiterrahmens L2, und

g

Normalabstand der beiden Leiterrahmen L1 und L2 (das heißt, ihrer zugewandten Innenfläche).

For a more detailed description of the operation of a current sensor according to the invention, as in the schematic diagram of 1B the following notation is used in the following:

B1

y component at the location of the first magnetic field sensor (that is, at the first chip IC1 on the first lead frame L1),

B2

y component at the location of the second magnetic field sensor (that is, at the second chip IC2 at the second lead frame L2),

I ₀

Total current through both lead frames L1 and L2,

k · I ₀

Current through the lead frame 1,

(1-k) · I ₀

Current through the lead frame L2,

d

Chip thickness,

t

Conductor frame thickness of the first lead frame L1 and the second lead frame L2, and

G

Normal distance of the two lead frames L1 and L2 (that is, their facing inner surface).

The first magnetic field B1 that can be measured by the first magnetic field sensor chip IC1 can be described by the following expression: B1 = k · I 0 B y (-T / 2 -d, y) + (1-k) · I 0 · B y (-T / 2-g -t -d, y).

The magnetic field B2 that can be measured at the second magnetic field sensor chip IC2 can be described by the following expression: B2 = k · I 0 · B y (t2 / + g + t + d, y) + (1 - k) · I 0 · B y (t / 2 + d, y).

In the above notation, the expression B _{y designates} that field that is due to 1 ampere current flow.

With the symmetry condition mentioned above it is easy to show that the difference between B2 and B1 is _: B2 - B1 = I 0 · B y (t / 2 + d, y) + I 0 · B y (t / 2 + g + t + d, y).

The aforementioned difference relation shows that B2 - B1 is a function I ₀ , but not k. Thus, the difference of the fields at the location is at the magnetic field sensor chips IC1 and IC2 regardless of the current distribution on the two lead frames L1 and L2. The distribution of the total current I ₀ on the conductors L1 and L2 therefore does not affect the signal B2 - B1. B2 - B1 thus measures the sum of the total current through the lead frames L1 and L2. The exact geometry of the conductor cross-section of the first lead frame L1 and the second lead frame L2 is not essential. The first lead frame L1 may even have a different cross section than the second lead frame L2. In order to provide an optimal measuring characteristic of the current sensor, however, the conductor cross-section should have an even function with respect to the in 1A represented x'-coordinate, so that the first lead frame L1 and the second lead frame L2 should thus be axially symmetric with respect to its center plane as the axis of symmetry, so that the above symmetry condition applies.

• 1. Verwendung eines einzelnen Grundleiterrahmens, wie beispielsweise dem in 2 dargestellte Leiterrahmen L12. Die beiden Magnetfeldsensorchips IC1 und IC2 werden nebeneinander am gleichen Leadframe (d.h. Leiterrahmen) L12 platziert. Zwischen den ICs befinden sich Ausstanzungen 202, die für eine Verbindung beider Magnetfeldsensorchips (das heißt ICs) als interne Pins, beispielsweise wie die Pins 204 oder als externe Pins 206 oder als optionale externe Pins 208 benutzt werden können. An der Außenseite zumindest eines der beiden Magnetfeldsensorchips IC1 und IC2 befinden sich die Pins zur Stromversorgung beider Magnetfeldsensoren sowie zur Dateneingabe oder Datenausgabe. Als Dateneingabe für einen Magnetfeldsensor wäre in diesem Zusammenhang ein Eingangspin zum Kalibrieren des Sensors denkbar, die Datenausgabe kann die Ausgabe eines Messwerts umfassen. Die Stromflussrichtung in der in 2 dargestellten Applikation ist vertikal in beiden Teilen L1 und L2 des Leadframes gleich gerichtet. Zuerst werden die Magnetfeldsensorchips IC1 und IC2 am Leiterrahmen L12 mit herkömmlichen Verfahren (beispielsweise durch Kleben oder Löten) befestigt. Dieses Befestigen kann dabei auf der gleichen Seite des Leiterrahmens L12 erfolgen, wodurch sich die herkömmlichen Herstellungsverfahren einsetzen lassen. Dabei kann je nach Bedarf eine leitende Verbindung oder eine elektrische Isolation zwischen den Magnetfeldsensorchips IC1 und IC2 und dem Leiterrahmen L12, das heißt, den Primärstromleiter, geschaffen werden. Danach werden beispielsweise die Verbindungen der Magnetfelssensorchips untereinander sowie zur Außenwelt durch herkömmliche Bondverfahren hergestellt. Hieran anschließend gibt es die folgenden beiden Möglichkeiten: a) Der Leiterrahmen L12 wird an der in 2 dargestellten gestrichelten Linie 210 gefaltet, so dass die Leiterrahmenteile links und rechts von der gestrichelten Linie 210 mit der Rückseite zueinander stehen. Dies bedeutet beispielweise, dass die in 2 dargestellte Anordnung derart gefaltet wird, dass die beiden äußeren Enden 212 des Gesamtleiterrahmens L12 nach hinten geklappt werden, wodurch sich die Magnetfeldsensorchips IC1 und IC2 auf den Außenseiten des Gesamtleiterrahmens L12 befinden. Dazu ist es notwendig, den Gesamtleiterrahmen L12 zumindest teilweise aus einem gesamten Leiterrahmenband (beispielsweise einem Endlosband) herauszustanzen. Dieses Endlosband lässt sich insbesondere aus produktionstechnischen Gründen vorteilhaft verwendet, da in einem solchen Band eine Montage der Magnetfeldsensorchips kostengünstig und einfach herstellbar ist. Danach kann die Anordnung des zusammengeklappten Leiterrahmens L12 vergossen werden, um ein Schutzgehäuse um die beiden Magnetfeldsensoren IC1 und IC2 bereitzustellen. Dieser Fertigungsschritt ist wohl aber sehr kompliziert und unhandlich. Daher wird in der Praxis meist die nachfolgend näher beschriebene Alternative bevorzugt. b) Die beiden Magnetfeldsensorchips IC1 und IC2 werden einzeln vergossen, um ein Schutzgehäuse um diese Magnetfeldsensorchips bereitzustellen. In diesem Fall werden die beiden Verbindungspins zwischen den beiden Magnetfeldsensorchips IC1 und IC2 teilweise freistehend – das heißt, unvergossen – belassen. Danach erst werden die beiden Magnetfeldsensorchips IC1 und IC2 teilweise oder zur Gänze freigestanzt und die Faltung entlang der gestrichelten Linie 210 vorgenommen. Alternativ zur Faltung kann auch eine Trennung erfolgen: Danach werden die beiden Teile mit dem ersten Leiterrahmen L1 und dem zweiten Leiterrahmen L2 mit dem Rücken zueinander gebracht und verbunden, was beispielsweise durch ein Löten, Kleben oder Schweißen möglich ist. Dabei gibt es die Möglichkeit, dass beide Leiterrahmen-Rücken ganzflächig leitfähig miteinander (beispielsweise elektrisch leitfähig durch eine Haftschicht 302) verbunden werden, wie es in 3 dargestellt ist. Die Magentfeldsensorchips IC1 und IC2 mit den jeweiligen (Magnetfeld-) Elementarsensoren IC1' und IC2' können dann durch eine Haftschicht 304 (= die attach) auf den ersten Leiterrahmen L1 oder zweiten Leiterrahmen L2 befestigt werden, wie es in 3 dargestellt ist. Alternativ können auch die beiden Leiterrahmen-Rücken nicht ganzflächig verbunden werden, wie es beispielsweise durch die Haftschicht 302 in 4 dargestellt ist. In diesem Fall lässt sich auch als Verbindungsschicht eine Haftschicht mit einem isolierenden oder nicht-isolierenden Material verwenden. Alternativ ist auch denkbar, dass die beiden Magnetfeldsensorchips auf den Leiterrahmen mit einer Vergussmasse einzeln umspritzt werden, so dass diese Magnetfeldsensorchips und ein erster Bereich der Leiter L1 oder L2, auf dem die Magnetfeldsensorchips jeweils angeordnet sind von der Vergussmasse umschlossen werden. Beispielsweise kann dann die Vergussmasse bei Zusammenklappen auch die Rückseite beider Leiterrahmen L1 und L2 bedecken, so dass diese nur noch an ihren Pins miteinander verbunden sind. Ebenso ist es denkbar, dass die beiden Leiterrahmenteile L1 und L2 vollständig voneinander isoliert bleiben und damit die Summe der in dem Leiterrahmen L1 und dem Leiterrahmen L2 fließenden Ströme gemessen werden kann, ohne dass diese dabei galvanisch in Verbindung stehen.
• 2. Verwendung zweiter getrennter Leiterrahmen: Diese Möglichkeit entspricht der in Punkt 1b aufgezeigten Möglichkeit bei Trennung der beiden Leiterrahmenteile L1 und L2. Insbesondere können dazu zwei (End-los-) Leiterrahmenbänder verwendet werden, wobei auf das erste Band nur Magnetfeldsensorchips vom Typ des ersten Magnetfeldsensorchips IC1 aufgebracht und auf das zweite Band nur Magnetfeldsensorchips vom Typ des zweiten Magnetfeldsensorchips IC2 aufgebracht werden. Danach gibt es wieder die folgenden Möglichkeiten, dass a) beide Magnetfeldsensorchips IC1 und IC2 getrennt voneinander noch in ihrem Leiterrahmenband vergossen und anschließend mit dem Rücken zueinander montiert werden, oder b) einer der beiden Magnetfeldsensoren aus seinem Leiterrahmenband herausgestanzt und mit dem Rücken zum anderen Magnetfeldsensor montiert und danach erst vergossen wird. Um die beiden Leiterrahmen L1 und L2 in Deckung zu bringen, werden vorteilhafterweise Zentrierbohrungen wie die in 2 dargestellten Bohrungen 214 verwendet. Alternativ lassen sich auch ähnliche Zentriermarken verwenden. Ebenfalls vorstellbar sind Knipsverbindungen, das heißt Einrastverbindungen, bei denen z. B. die Magnetfeldsensoren IC1 und IC2 oder eine erste Vergussmasse 216, die den ersten Magnetfeldsensor IC1 und einen ersten Bereich des ersten Leiterrahmens L1, auf dem der erste Magnetfeldsensorchip IC1 angeordnet ist, umschließt und eine zweite Vergussmasse 218, die den zweiten Magnetfeldsensor IC2 und einen ersten Bereich, auch dem der zweite Magnetfeldsensorchip IC2 angeordnet ist, umschließt, aufeinander „aufgeknipst" werden. Diese „Knipsverbindung" kann beispielsweise als mechanisch einfach herzustellende Plastik-Einrast-Verbindung ausgeführt sein.

For the production of the arrangement described above, the following mounting options are also conceivable:

• 1. Use of a single base ladder frame, such as in 2 illustrated lead frame L12. The two magnetic field sensor chips IC1 and IC2 are placed side by side on the same leadframe L12. There are cutouts between the ICs 202 which is for connecting both magnetic field sensor chips (ie, ICs) as internal pins, such as the pins 204 or as external pins 206 or as optional external pins 208 can be used. On the outside of at least one of the two magnetic field sensor chips IC1 and IC2 are the pins for the power supply of both magnetic field sensors and for data input or data output. In this context, an input pin for calibrating the sensor would be conceivable as data input for a magnetic field sensor, the data output may include the output of a measured value. The current flow direction in the in 2 The application shown is directed vertically vertically in both parts L1 and L2 of the leadframe. First, the magnetic field sensor chips IC1 and IC2 are attached to the lead frame L12 by conventional methods (for example, by gluing or soldering). This fastening can take place on the same side of the lead frame L12, whereby the conventional manufacturing methods can be used. In this case, as required, a conductive connection or an electrical insulation between the magnetic field sensor chips IC1 and IC2 and the lead frame L12, that is, the primary current conductor, are created. Thereafter, for example, the connections of the magnetic field sensor chips to each other and to the outside world are produced by conventional bonding methods. Following this, there are the following two possibilities: a) The lead frame L12 is connected to the in 2 shown dashed line 210 folded, leaving the ladder frame parts to the left and right of the dashed line 210 stand with the back to each other. This means, for example, that the in 2 shown arrangement is folded such that the two outer ends 212 of the Gesamtleiterrahmens L12 are folded backwards, whereby the magnetic field sensor chips IC1 and IC2 are on the outer sides of the Gesamtleiterrahmens L12. For this purpose, it is necessary to punch out the overall conductor frame L12 at least partially from an entire leadframe strip (for example, an endless strip). This endless belt can be advantageously used, in particular for reasons of production technology, since in such a belt assembly of the magnetic field sensor chips is inexpensive and easy to produce. Thereafter, the arrangement of the collapsed lead frame L12 may be potted to provide a protective package around the two magnetic field sensors IC1 and IC2. This production step is probably very complicated and unwieldy. Therefore, in practice usually the alternative described in more detail below is preferred. b) The two magnetic field sensor chips IC1 and IC2 are individually cast to provide a protective housing around these magnetic field sensor chips. In this case, the two connection pins between the two magnetic field sensor chips IC1 and IC2 partially free-standing - that is, non-pouring - left. Only then are the two magnetic field sensor IC1 and IC2 partially or completely punched free and the folding along the dashed line 210 performed. As an alternative to folding, a separation can also take place. Thereafter, the two parts are brought to the first lead frame L1 and the second lead frame L2 with their backs to each other and connected, which is possible for example by soldering, gluing or welding. There is the possibility that both leadframe backs over the entire surface conductive each other (for example, electrically conductive by an adhesive layer 302 ), as it is in 3 is shown. The magenta field sensor chips IC1 and IC2 with the respective (magnetic field) elementary sensors IC1 'and IC2' can then pass through an adhesive layer 304 (= the attach) are attached to the first lead frame L1 or second lead frame L2, as shown in 3 is shown. Alternatively, the two leadframe backs can not be connected over the entire surface, as for example by the adhesive layer 302 in 4 is shown. In this case, an adhesive layer having an insulating or non-insulating material can also be used as the bonding layer. Alternatively, too it is conceivable that the two magnetic field sensor chips are individually encapsulated on the lead frame with a potting compound, so that these magnetic field sensor chips and a first region of the conductors L1 or L2, on which the magnetic field sensor chips are respectively arranged, are enclosed by the potting compound. For example, then the potting compound when folding cover the back of both lead frames L1 and L2, so that they are connected to each other only at their pins. It is also conceivable that the two lead frame parts L1 and L2 remain completely isolated from one another and thus the sum of the currents flowing in the lead frame L1 and the lead frame L2 can be measured without them being electrically connected.
• 2. Use of second separate leadframe: This possibility corresponds to the possibility shown in point 1b when the two leadframe parts L1 and L2 are separated. In particular, two (end-los-) lead frame bands can be used, wherein applied to the first band only magnetic field sensor chips of the type of the first magnetic field sensor chip IC1 and applied to the second band only magnetic field sensor chips of the type of the second magnetic field sensor chip IC2. Thereafter, there are again the following possibilities: a) both magnetic field sensor chips IC1 and IC2 are cast separately in their lead frame strip and then mounted with their backs to each other, or b) one of the two magnetic field sensors punched out of its lead frame tape and with his back to the other magnetic field sensor mounted and then shed first. In order to bring the two lead frames L1 and L2 in line, are advantageously centering holes as in 2 shown holes 214 used. Alternatively, similar centering marks can be used. Also conceivable Knipsverbindungen, that is snap-in connections, in which z. B. the magnetic field sensors IC1 and IC2 or a first potting compound 216 comprising the first magnetic field sensor IC1 and a first region of the first lead frame L1 on which the first magnetic field sensor chip IC1 is disposed, and a second potting compound 218 , which encloses the second magnetic field sensor IC2 and a first region, to which the second magnetic field sensor chip IC2 is arranged, are "snapped on one another." This "snap connection" can be embodied, for example, as a plastic snap-in connection which is easy to produce mechanically.

A particular advantage of this arrangement is that with low requirements for susceptibility, for example, only in 3 or 4 shown left part, consisting of the first magnetic field sensor IC1 and the first lead frame L1 used and leaves the internal pins depending on the circuit open or short circuit. For this purpose, the internal pins can also be implemented as external pins which can be operated open (= open) or short-circuited (= short) by the customer in the case of low EMC requirements (EMC = Electromagnetic Compatibility) and in the case of high EMC Requirements can be combined with the second magnetic field sensor (IC2 on the opposite side of the first lead frame L1.

It is also possible to execute the second magnetic field sensor chip IC2 without the second lead frame L1. Then, the current to be measured flows only in the first lead frame L1. The second magnetic field sensor chip IC2 can be snapped or glued after casting onto the first magnetic field sensor chip IC1. In this case, then the thicknesses of the lead frame L1 or L2 and the potting compounds 216 and 218 ideally, to be dimensioned so that the normal distance from the surface of the first lead frame L1 to the magnetic field sensor chip in the embodiment of the first magnetic field sensor chip IC1 is the same as that of the second magnetic field sensor chip IC2 to the surface of the first lead frame L1. But that's not necessary. Alternatively, of course, the first magnetic field sensor chip IC1 can be performed without the first lead frame L1. Then, the current to be measured flows only in the second lead frame L2. As a third alternative, a third conductor may be used for conducting the current to be measured, so that the first magnetic field sensor chip IC1 and the second magnetic field sensor chip IC2 have a conventional lead frame, but this is not used to conduct a current flow to be measured. Thus, a conductor between both magnetic field sensor chips IC1 and IC2 is sufficient.

The third alternative is particularly favorable because of their modularity, since different thicknesses and widths can be used depending on the current range. The magnetic field sensor chips IC1 and IC2 actually measure only the current density in the conductor; By changing the conductor cross-sectional area, the total current can be scaled while the current density remains the same. From the semiconductor manufacturer is then a doublet of magnetic field sensor chips (that is, the magnetic field sensor chips IC1 and IC2) shipped. This can be made on a single leadframe band, in which case the electrical connections between the magnetic field sensor chips IC1 and IC2, that is, the internal pins, are already configured to function. Alternatively, however, the magnetic field sensor chips IC1 and IC2 may be physically separate from each other so that the electrical connections between the first magnetic field sensor chip IC1 and the second magnet field sensor chip IC2 should still be made by a connection of associated pins. In both cases, however, the doublet is related and was calibrated as a unit by the semiconductor manufacturer.

To the internal pins, such as those in 2 by the reference numerals 204 It should be noted that these constitute an internal electrical connection between the first magnetic field sensor chip IC1 and the second magnetic field sensor chip IC2 and do not provide an electrical connection to the outside. However, you may be accessible from the outside. Then the arrangement is convolution, so the internal pins are inherently connected. However, if the two leadframe parts L1 and L2 are initially disconnected from each other, the internal pins can either be interconnected (eg, by soldering or welding) by the semiconductor manufacturer, or they can be individually accessed by the customer, depending on the application to the associated pins interconnects in order to achieve high EMC strength, or not to connect the second magnetic field sensor chip IC2 to the first magnetic field sensor chip IC1 by deliberately leaving open or short-circuiting various internal pins. It is also conceivable that the semiconductor manufacturer first connects the internal pins with each other and then again electrically insulated to the outside (for example, by applying insulating varnish or re-casting the composite).

One An essential advantage of the arrangement is that the first magnetic field sensor chip IC1 and the second magnetic field sensor chip IC2 delivered in parallel be, that is, they usually come from the same front-end production lot, or else the same assembly lot. Ideally, they come from the same wafer and are placed on this side by side. Therefore their mating tolerance is optimal in terms of magnetic sensitivity and temperature response, as well as optimal with respect to an internal resistance, an aging behavior, a magnetic field sensitivity, a temperature gradient this parameter, etc.

Further is yet another advantage to mention: if the connection of both ICs are made with internal pins, so these are bonded before the Final test performed becomes. Therefore, one can influence the calibration during the final test the bonding wires and internal pins (e.g., contact resistances) and receives thus more exactly balanced parts.

There is another important advantage:
The elementary sensors are sensitive to magnetic fields parallel to the chip plane. Before folding or back-to-back mounting, they react to a tangential magnetic field of the same sign. After folding, the direction of the second sensor is reversed, so that it responds with different signs to the applied magnetic field. So you can test the arrangement after folding only by a differential magnetic field - as it is generated by an intermediate conductor - test. This may be a problem, for example, if you need a very high current to generate sufficient fields for testing purposes. Therefore, it is an advantage to be able to test the sensors before folding in common homogeneous fields - the same direction on both sensors - because these are easier to produce with high field strength.

Furthermore, the assembly takes place (that is, the joining together of the first magnetic field sensor chip IC1 and the second magnetic field sensor chip IC2, by gluing, soldering or notching) immediately after the process of applying the housing, the is called, the casting and before the final test of the semiconductor manufacturer. By the small one thermal mass of the arrangement with respect to conventional current sensors (in particular by the lack of a heavy magnetic core), it is possible to Final test at several temperatures due to the short time required in testing without a heavy magnetic core and the system in terms of his Temperature response, in particular its offset error and its sensitivity, to calibrate. This calibration can be done thereby, that the current sensor first in a first ambient temperature is measured, then the first ambient temperature is changed, to get a second ambient temperature then the signal of the first or second magnetic field sensor chips is detected, wherein the Capture then executed is when the first or second magnetic field sensor chip the second Ambient temperature has. Here by can also be an evaluation in the first magnetic field sensor chip IC1 in a first calibration state and another evaluation device in the second magnetic field sensor chip IC2 in a second calibration state, different from the first Calibration state differs and thus manufacturing technology Tolerances of the magnetic field sensor chips or the evaluation in compensates for the magnetic field sensor chips. By such a calibration elevated Furthermore, the accuracy and reliability of the current sensor, because 100 percent of the parts tested throughout the temperature range can be. A customer receives Thus, a finished calibrated component of maximum accuracy and does not need to think about it with regard to conductor geometry and calibration over temperature.

For the two magnetic field sensor chips IC1 and IC2 is still the following extension conceivable. Previously, it was assumed that the second magnetic field sensor IC2 has only one elementary sensor IC2 'for detecting the magnetic field component that is tangent to the chip surface. This is appropriately connected to the elementary sensor IC1 'in the first magnetic field sensor chip IC1, so that a difference between a first signal of the elementary sensor IC1' in the first magnetic field sensor chip IC1 and a second signal of an elementary sensor IC2 'in the second magnetic field sensor chip IC2 can be formed. Since the conductor pieces - that is, the internal pins - but for dimensions of an integrated circuit to be described as too long, we recommend a pre-amplification or impedance conversion or other signal preprocessing of the sensor signals of the second magnetic field sensor chip IC2 (or the first magnetic field sensor chip IC1). This is easily possible, since the second magnetic field sensor chip IC2 should have a minimum size from the point of view of assembly technology in order to be manageable. Since the elementary sensor IC2 'is usually much smaller than this minimum size, would remain valuable silicon or semiconductor surface unused. Also, the second magnetic field sensor chip IC2 is subjected to a wafer test. However, since testing the elementary sensor IC2 'takes less time than further stepping to the next magnetic field sensor, it is also attractive for reasons of test time to pack more intelligence on the second magnetic field sensor chip IC2. So in practice, it costs little, even the second magnetic field sensor chip IC2 analog to the first magnetic field sensor chip IC1 with electronics, that is, to be provided with an integrated circuit. If one thinks this thought to the end, one comes to the conclusion that it is advisable to design the first magnetic field sensor chip IC1 and the second magnetic field sensor chip IC2 identically. Each of the two magnetic field sensor chips thus receives a signal from the corresponding partner chip and processes this either separately or together with its own signal to the output signal. This processing may include, for example, a difference formation and / or a gain of the respective signals. This achieves a redundancy that can be advantageously used in safety-relevant systems. In addition, it is possible, for example by a switching device, to perform a switchover between a signal evaluation based on a single magnetic field sensor chip or a signal evaluation on the basis of signals of the two magnetic field sensor chips. The switching device for coupling an evaluation device of the first magnetic field sensor chip with a further evaluation device of the second magnetic field sensor chip can be designed to couple the evaluation device to the further evaluation device in response to a first switching signal and not to couple the evaluation device to the further evaluation device in response to a second switching signal , Such an idea is interesting, since usually this doubling of the magnetic field sensor chips costs less than twice the chip area and less than twice the test time of a single chip, and thus this technical additional service does not represent a significant economic cost. However, a weak point in the insertion of such redundant structures is to be seen in the connection technology of both magnetic field sensor IC1 and IC2, although this connection technique of the two magnetic field sensors can be made more reliable and robust by a possible doubling of each connection. Another advantage is also to mention that the arrangement still works in principle, if one of the magnetic field sensor chips fails and thereby creates an open connection to the partner chip. In this way, although the sensitivity drops to about half, since only one field is measured on a conductor surface. However, the current flow can still be detected in a makeshift manner. By usual plausibility comparisons of the output signals of both magnetic field sensor chips, one can then easily determine whether possibly one of the two magnetic field sensor chips no longer works.

In summary It should be noted that the gist of the invention is a current sensor relates to the total electric flow through one or more Conductor pieces measures, with the electricity in case of multiple electric interconnected conductor parts the same direction of current flow by having two magnetic field sensors parallel to the conductor surface Magnetic field components on top of the top conductor part and measure on the underside of the lowest ladder part, the difference form and used to evaluate the sum of the currents through all ladder parts. The difference to the aforementioned Patent application is that the magnetic field sensors are not on both sides of one and the same ladder of a ladder frame need to be applied. Instead, they are on top fastened by ladder frame in a conventional manner. The ladder frames can then serve as a leader at the same time. If a leadframe (for example the first magnetic field sensor chip IC1 and / or the second magnetic field sensor chip IC2) does not serve as a conductor, so its housing is preferably with devices provided that its location regarding clearly define the manager assigned to him. Furthermore is Note that the two magnetic field sensor chips IC1 and IC2 to each other are assigned and preferably from the same wafer and / or the same Montagelos can come and further tuned or calibrated in a final test can be. Furthermore you can the first magnetic field sensor chip IC1 and the second magnetic field sensor chip IC2 be configured identically, so that the system becomes redundant.

B _y

Magnetfeldtast due to 1 ampere current flow

x '

x-coordinate

y '

y coordinate

L1

first leadframe

L2

second leadframe

IC1

first Magnetic field sensor chip

IC2

second Magnetic field sensor chip

B1

y component at the location of the first elementary sensor

B2

y component at the location of the second elementary sensor

I ₀

total current through both conductors

k · I ₀

electricity through the first lead frame L1

(1-k) · I ₀

electricity through the second lead frame L2

d

chip thickness

t

Leadframe thickness the first lead frame L1 and the

second Lead frame L2

G

normal distance the two lead frames L1 and L2 (the

is called, the Distance of the facing inner surface

202

outs

204

internal pins

206

external pins

208

optional external pins

210

dashed Line (folding line)

212

outside of the overall ladder frame L12

L12

Total leadframe

214

centering

216

first Potting compound for forming the first

housing structure for the Magnetic field sensor chip IC1

218

Sealing compound for forming a second housing structure around

the second magnetic field sensor chip IC2

302

adhesive layer (conductive or insulating)

IC1 '

Elementary magnetic field sensor 1

IC2 '

Elementary magnetic field sensor 2

304

adhesive layer for fixing the magnetic field sensors IC1

and IC2 (= the attach)

502

first Magnetic field sensor chip

504

second Magnetic field sensor chip

506

leadframe

508

first Adhesive layer between the first

Magnetic field sensor chip 502 and the ladder frame 506

510

second Adhesive layer between the second

Magnetic field sensor chip 504 and the ladder frame 506

512

bonding wire for contacting the first

Magnetic field sensor chips 502 with an external one

connector pin 514

514

external connector pin

516

second Bonding wire for contacting the second

Magnetic field sensor chips 504 with the external pin 514

Claims (16)

Current sensor with the following features: one first lead frame (L1) having a first region with a current conductor having; a first magnetic field sensor chip (IC1) mounted on the first area on a first side of the first lead frame (L1) is arranged; a second lead frame (L2) having a second region having a current conductor; a second Magnetic field sensor chip (IC2) located on the second area of a first Side of the second lead frame is arranged; and where second Side of the lead frames (L1, L2), the first sides of the same opposed, are arranged facing each other, such that the magnetic field sensor chips (IC1, IC2) are arranged substantially opposite one another. Current sensor according to Claim 1, in which the first leadframe (L1) is connected to the second leadframe (L2) by an adhesive layer ( 302 ) connected is. Current sensor according to claim 1 or 2, in the first magnetic field sensor chip (IC1) and the second Magnetic field sensor chip (IC2) by a connecting element with each other are connected, wherein the connecting element is a mechanical latching connection is. Current sensor according to a the claims 1 to 3, in which the first lead frame (L1) has an axis symmetry in terms of a first axis of symmetry and wherein the second lead frame (L2) an axis symmetry with respect having a second axis of symmetry. Current sensor according to one of claims 1 to 4, which has a first housing structure ( 216 ), in which the first region of the first lead frame (L1) and the first magnetic field sensor chip (IC1) is arranged and which has a second housing structure ( 218 ), in which the second magnetic field sensor chip (IC2) and the second region of the second leadframe (L2) are arranged. Current sensor according to one of claims 1 to 5, further comprising an evaluation device, which is connected to the first magnetic field sensor chip (IC1) and the second magnetic field sensor chip (IC2). Current sensor according to claim 6, in which the first magnetic field sensor chip (IC1) is formed, to output a first signal and wherein the second magnetic field sensor chip (IC2) is adapted to output a second signal, wherein the Evaluation device is designed to from the first and second Signal to form a difference. Current sensor according to claim 7, wherein the evaluation device is further formed to the first Signal, the second signal or the difference between the first Convert signal and the second signal into a processed signal. Current sensor according to a the claims 6 to 8, which further comprises a second evaluation device, the is arranged in the second magnetic field sensor chip (IC2) and with the evaluation device can be coupled, wherein the second evaluation device is formed to the difference from the first signal and the to consider the second signal, to determine an output signal of the current sensor. Current sensor according to claim 9, further comprising a switching device for coupling the evaluation device having the further evaluation device, wherein the switching device is configured to, in response to a first switching signal To couple evaluation with the other evaluation and in response to a second switching signal, the evaluation device not to be coupled with the further evaluation device. Current sensor according to a the claims 9 or 10, in which the further evaluation of the evaluation equivalent. Current sensor according to a the claims 8 to 10, in which the evaluation device in a first calibration state is and the further evaluation device is in a second calibration state, which differs from the first calibration state. Method for producing a current sensor with following steps: Providing a first lead frame (L1) and a second lead frame (L2), wherein the first lead frame (L1) has a current conductor in a first region, and the second lead frame (L2) in a second region a current conductor having; Arranging a first magnetic field sensor chip (IC1) the first area on a first side of the first lead frame (L1); Arranging a second magnetic field sensor chip (IC2) the second area on a first side of a second leadframe (L2); and Arranging second sides of the lead frames (L1, L2), which oppose the first pages of the same, such that the second sides are facing each other and the magnetic field sensor chips (IC1, IC2) are arranged substantially opposite one another, to make the current sensor. Method according to claim 13, wherein the steps of placing in a first ambient temperature accomplished and the first magnetic field sensor chip (IC1) is formed, to provide a first signal, and the second magnetic field sensor chip (IC2) is designed to provide a second signal, the method further comprising the steps of: Changing the first ambient temperature to a second ambient temperature receive; Detecting the first or second signal, wherein the detecting then executed is when the first or second magnetic field sensor chip the second Ambient temperature has. Method according to one the claims 13 or 14, wherein the first magnetic field sensor chip (IC1) an evaluation device with a first functionality and the second magnetic field sensor chip (IC2) has another Having evaluation device with a second functionality, the method of manufacturing further comprising the steps of: Testing the first functionality the evaluation device; and Testing the second functionality of the others Evaluation. A method of operating a current sensor, wherein the current sensor comprises a first lead frame (L1) having a first region with a current conductor, a first magnetic field sensor chip (IC1) disposed on the first region on a first side of the lead frame, a second lead frame (L2) having a second region with a current conductor, a second magnetic field sensor chip (IC2) disposed on the second region of a first side of the second lead frame (L2), and wherein second sides of the lead frames (L1, L2), which are opposite to the first sides thereof, arranged facing each other, such that the magnetic field sensor chips (IC1, IC2) are arranged substantially opposite each other, the method for operating the current sensor comprising the steps of: applying the first lead frame (L1) or the second Lead frame (L2) with a current; and detecting a signal of the first magnetic field sensor chip (IC1) or the second magnetic field sensor Chips (IC2).