DE102004021862B4 - current Senor - Google Patents

Abstract

Current sensor having the following features: a first lead frame (L1) which has a first area with a current conductor; a first magnetic field sensor chip (IC1) which is arranged on the first area on a first side of the first lead frame (L1); a second lead frame (L2) having a second area with a current conductor; a second magnetic field sensor chip (IC2) which is arranged on the second region of a first side of the second lead frame; and wherein second sides of the lead frames (L1, L2), which are opposite to the first sides thereof, are arranged facing one another, in such a way that the magnetic field sensor chips (IC1, IC2) are arranged substantially opposite one another, the current sensor being designed to an electrical To measure the total current flow through the two current conductors, the two current conductors being electrically connected to one another and having the same current flow direction.

Description

The present invention relates to the field of semiconductor sensor technology, and more particularly, the present invention relates to a magnetic field sensor which is easier to manufacture than the prior art, and a method of manufacturing and a method of operating the same.

In order to measure a magnetic field of a current-carrying conductor without contact, special magnetic field sensors can be used, which are arranged in a certain position with respect to the conductor. In this case, the conductor can also be used as a leadframe and a magnetic field component can be evaluated parallel to the conductor surface (eg with a GMR or a vertical Hall probe). Furthermore, the measurement of external interference fields can remain unaffected, for which purpose the field above and below the conductor strip (that is to say the leadframe) is measured. In both places, the field has different signs, so that its amount is doubled by subtraction. Foreign fields are, however, to a good approximation homogeneous, so that they are cut out by the subtraction.

Such a problem was already in the patent application with the German file number 10315532.5 treated. 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) Seide Chips werden zugleich (d. h. simultan) auf der Leadframe-Ober- und -Unterseite befestigt, so dass beide Kleber/Lote zugleich aushärten. Wahrend des Aushärtens darf sich dabei die Lage der Chips gegenuber dem Leadframe nicht unzulässig ändern. Dadurch, dass die Chips gleichzeitig zu beiden Seiten des Leadframes befestigt werden, kann dies ein schwieriges Problem darstellen. Herkommlicherweise liegt der Chip auf dem Leadframe, so dass eine Position durch die Schwerkraft nicht verandert wird. Wenn nun allerdings der zweite Chip auf der Leadframe-Unterseite liegt, so kann es bei schlecht gewahlten Prozessparametern dazu kommen, dass sich seine Lage wahrend des Aushärtens andert. Alternativ kann man aber das Leadframe wahrend des Aushärtens auch senkrecht stellen, so dass beide Chips die Schwerkraft in derselben Richtung (parallel zur Chipebene bzw. Lötflache/Klebeflache) 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 Aushartungs- 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) Silk chips are simultaneously (ie simultaneously) attached to the leadframe top and bottom, so that both glue / solders harden at the same time. During curing, the position of the chips relative to the lead frame must 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. Traditionally, the chip is located on the leadframe, so that a position is not changed by gravity. However, if the second chip is located on the bottom side of the leadframe, the process parameters may be poorly selected, causing it to change its position during curing. Alternatively, however, it is also possible to set the leadframe vertical during curing so that both chips become gravity in the same direction (parallel to the chip plane or soldering surface / adhesive 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 cure temperatures. 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 on an upper side of a leadframe is arranged while a second semiconductor chip is disposed on an underside 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 DE 101 08 640 A1 shows a sensor arrangement for contactless current measurement with two oppositely current-carrying conductor sections and with two sensors, which are preferably arranged in a common chip parallel to the conductor plane. In an evaluation circuit, a measurement signal formed by linking the measured values of the sensors is provided. These sensors are designed so that in each case a magnetic field component, which is caused by the current to be measured, is detected in the plane defined by the conductor sections level.

The DE 100 51 160 A1 shows a sensor arrangement for contactless measurement of a current with a conductor having two parallel conductor branches for guiding the current, wherein in an intermediate space formed by the conductor branches, an integrated circuit with two sensors for detecting magnetic fields caused by partial currents is arranged. In preferred embodiments, this integrated circuit is arranged parallel or orthogonal to the conductor branches.

The DE 100 11 974 A1 discloses a construction and connection technology of a current sensor of the microsystem technology, wherein the current conductors, which have a cross-sectional reduction according to the allowable current carrying capacity at the measuring point and a minimum possible distance from each other, are manufactured in conjunction with a circumferential frame, the conductors are then provided with a plastic sheath , wherein the plastic sheath serves as insulation and conductor fixing at the same time, and then the frame is separated.

The publication "A module for all current ranges" by H. Lemme, published in: Elektronik, 18, 1999, pages 71 ff., Shows a magnetoresistive current sensor that is sensitive only to differential fields, but not to homogeneous fields. For this purpose, these magnetoresistive resistors are arranged on an insulator over a primary conductor, connected in accordance with and connected to an evaluation.

The DE 26 30 958 B2 shows an error compensation method for measuring devices for detecting analog electrical or in such reshaped sizes, in particular measuring devices that convert analog quantities into digital values and the measured values are calculated by a computer, preferably by a microcomputer. In this case, the meter computers are assigned memory in the correction values and values of correction curves of the reference variables and all of the components whose properties affect the measurement result and species-specific and individual temperature coefficients and values of temperature history curves, species or individual aging rates, the reference quantities and components are stored that these Correction values are respectively measured under the influence of the measuring device's own analog-to-digital converter so that its errors include that the measuring devices register the elapsed time since use of a measuring device by means of time base devices and that all these stored correction values are taken into account in the calculation of the final measured values.

The DE 23 28 587 A1 shows an arrangement for measuring electrical AC magnitudes by means of an electronic measuring device, wherein the measured alternating current variables are galvanically isolated from the electronic components of the measuring device. For galvanic separation while current comparators are used.

The object of the present invention is to provide a current sensor, a method for producing a current sensor and a method for operating a current sensor, wherein the current sensor can be produced more easily than the prior art.

This object is achieved by a current sensor according to claim 1, a method for manufacturing a current sensor according to claim 12 and a method for operating a current sensor according to claim 14.

The present invention is based on the finding that first the first magnetic field sensor is mounted on a first side of the first lead frame, then the second magnetic field sensor is conventionally mounted on the first side of the second lead frame and then both lead frames with the back, ie second sides which are opposite to the first sides, fixed to each other. This means in particular that the lead frames are brought into a position in which the sides on which the magnetic field sensors are not mounted face each other. In order to be able to provide protection of the first and second magnetic field sensors, the two magnetic field sensors can also be secured against each other, for example by encapsulation in a potting compound, before restoring the second sides of the lead frames. Alternatively, this fixing, for example, by gluing with a conductive or insulating adhesive or realized by further potting.

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 realization 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, is independent of the distribution of the current to the first or second lead frame.

Preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. Show it:

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 inventive method 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, the same or similar reference numerals are used for the elements shown and similar in the various drawings, and a repeated description of these elements will be 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 leadframes are very low impedance, contact resistances between both leadframes can not be neglected. They result in the total current not being uniformly divided (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 split 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 satisfies the following symmetry condition: 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 (t 2 / + 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 = _I0 * _By (t / 2 + d, y) + _I0 * _By (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 of the two magnetic field sensor chips IC1 and IC2 is independent 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 be shown x 'coordinate, so that the first lead frame L1 and the second lead frame L2 should therefore be axisymmetric 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 kostengunstig 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 naher beschriebene Alternative bevorzugt.
• b) Die beiden Magnetfeldsensorchips IC1 und IC2 werden einzeln vergossen, um ein Schutzgehause 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 Rucken zueinander gebracht und verbunden, was beispielsweise durch ein Löten, Kleben oder Schweißen möglich ist. Dabei gibt es die Moglichkeit, dass beide Leiterrahmen-Rücken ganzflächig leitfahig 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 konnen auch die beiden Leiterrahmen-Rücken nicht ganzflachig 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 Ruckseite 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 Strome gemessen werden kann, ohne dass diese dabei galvanisch in Verbindung stehen.
• 2. Verwendung zweiter getrennter Leiterrahmen: Diese Möglichkeit entspricht der in Punkt 1b aufgezeigten Moglichkeit bei Trennung der beiden Leiterrahmenteile L1 und L2. Insbesondere konnen 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 ladder frame L12 is attached 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 can be inexpensively and easily produced. 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 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. Alternatively, the folding can also be a separation: then the two parts with the first lead frame L1 and the second lead frame L2 brought back and connected to each other with the jerk, which is possible for example by soldering, gluing or welding. There is the possibility that both leadframe backs over the entire surface conductive together (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 lead frame backs can not be connected flat, 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, it is also 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 separating the two leadframe parts L1 and L2. 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 "clipped" onto one another. This "Knipsverbindung" can be performed, for example, as a mechanically simple to produce plastic snap-in connection.

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.

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 depending on the current range different thickness and width conductors can be used. 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 also be physically separate from each other, such that the electrical connections between the first and second ICs Magnetic field sensor chip IC1 and the second magnetic field sensor chip IC2 should still be prepared by a combination 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 lead frame 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).

An essential advantage of the arrangement is that the first magnetic field sensor chip IC1 and the second magnetic field sensor chip IC2 are delivered in parallel, that is, they usually come from the same front-end production lot, or the same Montagelos. Ideally, they originate from the same wafer and are arranged directly next to each other on this wafer. Therefore, their pairing tolerance is optimal in terms of magnetic sensitivity and temperature response, as well as optimal in terms of internal resistance, aging behavior, magnetic field sensitivity, temperature response of these parameters, etc.

Another advantage to mention is that when connecting both ICs to internal pins, they are bonded before the final test is run. Therefore, when calibrating on the occasion of the final test, one can take into account the influence of the bonding wires and the internal pins (eg contact resistance) and thus obtain more precisely 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 is u. U. a problem when z. B. a very high current would need to generate sufficient fields for testing purposes. It is therefore an advantage to be able to test the sensors prior to folding in conventional homogeneous fields - the same direction on both sensors - because these are easier to produce with high field strength.

Further, the mounting (that is, the joining of the first magnetic field sensor chip IC1 and the second magnetic field sensor chip IC2 by gluing, soldering or notching) is performed immediately after the process of applying the package, that is, the potting and before the final test of the semiconductor manufacturer. Due to the small 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 carry out the final test at several temperatures due to the short time required in testing without heavy magnetic core and the system with respect to its temperature coefficient, in particular its offset error and its sensitivity to calibrate. This calibration can be carried out by first measuring the current sensor in a first ambient temperature, then changing the first ambient temperature to obtain a second ambient temperature, then detecting the signal of the first or second magnetic field sensor chip, the detection then being carried out the first or second magnetic field sensor chip has the second ambient temperature. Here, an evaluation device in the first magnetic field sensor chip IC1 can be brought into a first calibration state and a further evaluation device in the second magnetic field sensor chip IC2 in a second calibration state, which differs from the first calibration state and thus manufacturing tolerances of the magnetic field sensor chips or the evaluation in the Magnetic field sensor chips compensates. Such calibration also increases the accuracy and reliability of the current sensor, as 100 percent of the parts can be tested over the entire temperature range. A customer thus receives a fully calibrated component of maximum accuracy and does not have to worry about conductor geometry and calibration over temperature.

In addition to the two magnetic field sensor chips IC1 and IC2, the following extension is also conceivable. So far, it has been 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, it is recommended Vorverstarkung or impedance conversion or other signal pre-processing 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 the 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 switching means to perform a switching 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 reliable 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, because only one field is measured on a conductor surface. However, the current flow can still be detected in a makeshift manner. By means of 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 functions.

In summary, the core of the invention relates to a current sensor which measures the total electrical current flow through one or more conductor parts, the current having the same current flow direction in the case of a plurality of electrically interconnected conductor parts, by two magnetic field sensors, the magnetic field components parallel to the conductor surface on top of the top ladder and on the underside of the bottom ladder, forming the difference and using it to evaluate the sum of the currents through all ladder parts. The difference to the aforementioned patent application is that the magnetic field sensors need not be applied on both sides of the same conductor of a leadframe. Instead, they are mounted on the top of leadframes in a conventional manner. The lead frames can then serve as conductors 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, its housing is preferably provided with devices which uniquely define its position with respect to the conductor associated therewith. It should also be noted that the two magnetic field sensor chips IC1 and IC2 are assigned to each other and can preferably originate from the same wafer and / or the same assembly and furthermore can be matched or calibrated in a final test. Furthermore, the first magnetic field sensor chip IC1 and the second magnetic field sensor chip IC2 can be configured identically, so that the system becomes redundant.

LIST OF REFERENCE NUMBERS

B _y

Magnetic field by 1 ampere current flow comes about

x '

x-coordinate

y '

y coordinate

L1

first ladder frame

L2

second ladder frame

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

Current through the first lead frame L1

(1-k) · I ₀

Current through the second lead frame L2

d

chip thickness

t

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

G

Normal distance between the two lead frames L1 and L2 (that is, 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 whole 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

Casting 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 attaching 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 chip 502 with an external connection pin 514

514

external connection pin

516

second bonding wire for contacting the second magnetic field sensor chip 504 with the external pin 514

Claims (14)

Current sensor with the following features: a first lead frame (L1) having a first region with a current conductor; a first magnetic field sensor chip (IC1) disposed on the first area on a first side of the first lead frame (L1); 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; and wherein second sides of the lead frames (L1, L2) facing the first sides thereof are disposed facing each other, such that the magnetic field sensor chips (IC1, IC2) are disposed substantially opposite to each other, wherein the current sensor is configured to measure a total electrical current flow through the two current conductors, wherein the two current conductors are electrically connected to each other and have the same current flow direction. 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, wherein the first magnetic field sensor chip (IC1) and the second magnetic field sensor chip (IC2) are interconnected by a connecting element, wherein the connecting element is a mechanical snap-in connection. Current sensor according to one of claims 1 to 3, wherein the first lead frame (L1) has an axis symmetry with respect to a first axis of symmetry and wherein the second lead frame (L2) has an axis symmetry with respect to 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). A current sensor according to claim 6, wherein the first magnetic field sensor chip (IC1) is adapted to output a first signal and wherein the second magnetic field sensor chip (IC2) is adapted to output a second signal, the evaluation means being configured to be composed of the first and second second signal to form a difference. Current sensor according to claim 7, wherein the evaluation device is further configured to convert the first signal, the second signal or the difference between the first signal and the second signal into a processed signal. Current sensor according to one of claims 6 to 8, further comprising a second evaluation device, which is arranged in the second magnetic field sensor chip (IC2) and can be coupled to the evaluation device, wherein the second evaluation device is adapted to the difference between the first signal and 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 to the further evaluation device, wherein the switching device is designed to couple the evaluation device with the further evaluation device in response to a first switching signal and not in response to a second switching signal, the evaluation device to couple another evaluation device. Current sensor according to one of claims 8 or 9, wherein the evaluation device is in a first calibration state 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 the following steps: Providing a first lead frame (L1) and a second lead frame (L2), the first lead frame (L1) having a first conductor in a first region, and the second lead frame (L2) having a second conductor in a second region; Arranging a first magnetic field sensor chip (IC1) on the first area on a first side of the first lead frame (L1); Arranging a second magnetic field sensor chip (IC2) on the second area on a first side of a second lead frame (L2); and Arranging second sides of the lead frames (L1, L2) facing the first sides thereof such that the second sides are aligned facing each other and the magnetic field sensor chips (IC1, IC2) are arranged substantially opposite to each other to make the current sensor; wherein the current sensor is configured to measure a total electrical current flow through the first and second current conductors, wherein the first and second current conductors are electrically connected together and have the same current flow direction. The method of claim 12, wherein the steps of arranging are performed at a first ambient temperature and the first magnetic field sensor chip (IC1) is configured to provide a first signal and the second magnetic field sensor chip (IC2) is configured to provide a second signal the method further comprising the steps of: Changing the first ambient temperature to obtain a second ambient temperature; Detecting the first or second signal, wherein the sensing is performed when the first or second magnetic field sensor chip has the second ambient temperature. 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 one another, wherein the current sensor is configured to measure a total electric current flow through the two current conductors, the two current conductors being electrically connected to each other and having the same current flow direction, wherein the method of operating the current sensor comprises the steps of: Applying a current to the first lead frame (L1) and the second lead frame (L2); and Detecting a signal of the first magnetic field sensor chip (IC1) and the second magnetic field sensor chip (IC2).

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