阅读说明：本技术 具有集成的主导体的电流传感器 (Current sensor with integrated primary conductor ) 是由 J-F·兰森 P·莫雷尔 于 2019-07-08 设计创作，主要内容包括：电流传感器包括绝缘体(10)、包括中央通道(18)和磁路间隙(22)的磁芯(6)、位于磁路间隙中的磁场检测器(8)、以及金属板引线框导体装置(4),该金属板引线框导体装置包括用于携载待测量电流的主导体(14)和用于将磁场检测器连接至外部电路的次级导体(16),该主导体包括延伸穿过磁芯的中央通道的中央部分(15)、从中央部分的相对两端延伸的侧向延伸臂(13)、以及用于连接至外部导体的连接端(17),次级导体包括多个导体,每个导体包括基本上与主导体的中央部分对准的感测单元连接片(21)和用于连接到外部电路的连接端(19),绝缘体包括围绕主导体的中央部分(15)的内部包覆模制部分(20),并形成相对于引线框导体装置定位和绝缘的磁芯引导件(32)。绝缘体还包括包覆模制在内部包覆模制部分、磁芯、磁场传感器、引线框导体装置的中央部分上的外部包覆模制部分(34)。(The current sensor comprises an insulator (10), a magnetic core (6) comprising a central passage (18) and a magnetic circuit gap (22), a magnetic field detector (8) located in the magnetic circuit gap, and a sheet metal lead frame conductor arrangement (4) comprising a primary conductor (14) for carrying a current to be measured and a secondary conductor (16) for connecting the magnetic field detector to an external circuit, the primary conductor comprising a central portion (15) extending through the central passage of the magnetic core, laterally extending arms (13) extending from opposite ends of the central portion, and connection ends (17) for connection to the external conductor, the secondary conductor comprising a plurality of conductors, each conductor comprising a sensing element connection tab (21) substantially aligned with the central portion of the primary conductor and a connection end (19) for connection to the external circuit, the insulator comprising an inner overmoulded portion (20) around the central portion (15) of the primary conductor, and forming a core guide (32) positioned and insulated relative to the lead frame conductor means. The insulator further includes an outer overmold portion (34) overmolded onto the inner overmold portion, the magnetic core, the magnetic field sensor, and the central portion of the lead frame conductor arrangement.)

1. A current sensor comprising an insulator (10), a magnetic core (6) having a central channel (18) and a magnetic circuit gap (22), a magnetic field detector (8) located in the magnetic circuit gap, and a sheet metal lead frame conductor arrangement (4), the sheet metal lead frame conductor arrangement (4) comprising a primary conductor (14) for carrying a current to be measured and a secondary conductor (16) for connecting the magnetic field detector to an external circuit, the primary conductor comprising a central portion (15) extending through the central channel of the magnetic core, laterally extending arms (13) extending from opposite ends of the central portion, and connection ends (17) for connection to an external conductor, the secondary conductor comprising a plurality of conductors each comprising a sensing element connection tab (21) substantially aligned with the central portion of the primary conductor and a connection end (19) for connection to an external circuit, the insulator comprises an inner overmolded portion (20) surrounding the central portion (15) of the main conductor, characterized in that the insulator further comprises an outer overmolded portion (34) overmolded onto the inner overmolded portion, the magnetic core, the magnetic field sensor, the central portion of the lead frame conductor arrangement, and in that the inner overmolded portion (30) comprises or consists of a thermoplastic polymer and the outer overmolded portion (34) comprises or consists of a thermosetting polymer.

2. Current sensor according to the preceding claim, wherein the thermoplastic polymer is selected from the group comprising PPS (polyphenylene sulfide), LCP (liquid crystal polymer), PA (polyamide).

3. The current sensor according to any of the preceding claims, wherein the thermosetting polymer is a semiconductor grade epoxy molding compound.

4. Current sensor according to any of the preceding claims, wherein the inner overmoulded part comprises a main part (30) overmoulded on the central part (15) of the main conductor, the main part comprising a core guide (32) comprising lateral guide edges (32b) engaging opposite sides of a limb of the core for laterally positioning the limb of the core relative to the lead frame conductor arrangement.

5. Current sensor according to the preceding claim, wherein the core guide (32) comprises a base layer (32a) arranged for positioning against a lateral branch (6b) of the core.

6. Current sensor according to either of the two immediately preceding claims, wherein the inner overmoulded part is constituted by the main part (30) and the core guide (32).

7. Current sensor according to any of the three immediately preceding claims, wherein the core guide (32) is provided on a side (4b) of the lead frame conductor arrangement opposite to the side (4a) against which the sensing unit (26) of the magnetic field detector (8) is mounted and connected.

8. Current sensor according to the preceding claim, wherein on the side (4a) on the lead frame conductor arrangement against which the sensing unit (26) of the magnetic field detector (8) is mounted, the leg (6b) of the magnetic core is separated from the inner overmoulded part (30) by a gap (35) which is filled with the material of the outer overmoulded part (34).

9. The current sensor of any of the preceding claims, wherein the outer overmolded portion completely encapsulates the magnetic core and the inner overmolded portion.

10. Current sensor according to any of the preceding claims, wherein the sensing unit (26) is connected to the secondary conductor (16) via a bond wire connection device (27).

11. A method of manufacturing a current sensor according to any preceding claim, comprising:

a) stamping or etching a blank of the lead frame conductor arrangement (4) in a lead frame (40) made of a sheet metal strip (41), the blank being connected to the lead frame made of a sheet metal strip by bridge attachments (42a, 42b, 42 c);

b) overmolding a central portion (15) of the primary conductor and portions of the secondary conductor to form the inner overmolded portion (30);

c) subsequently mounting a sensing unit (26) on the lead frame conductor arrangement and connecting the sensing unit to a sensing unit connection pad (21) of the secondary conductor (16),

d) subsequently mounting the core (6) on the inner overmoulded part (20) and optionally fixing the core with a dispensed amount of glue or with a clip;

e) subsequently overmolding the outer overmolded portion (34) around the magnetic core, the sensing unit and the inner overmolded portion (21);

f) optionally, subsequently plating the exposed portions of the lead frame;

g) subsequently stamping and forming the connecting ends (17, 19) of the primary and secondary conductors;

h) the sensor is then separated from the lead frame made of sheet metal strip.

12. The method of any of the preceding claims, wherein the inner overmolded portion is formed by injection molding of a thermoplastic polymer.

13. The method of any of the preceding claims, wherein the outer overmolded portion is formed by transfer molding of a thermoset polymer.

Technical Field

The invention relates to a current sensor comprising a magnetic core and a magnetic field detector in an air gap of the magnetic core for measuring a current flowing in a main conductor extending through a central channel of the magnetic core.

Background

Current sensors are used in a variety of applications for monitoring or controlling electrical devices and systems, and in many applications have significant advantages in reducing the cost of manufacturing these components and also the cost of implementing and using these components in electrical circuits.

Although some current sensors are not provided with a magnetic core for cost and/or size reasons, this generally reduces the reliability and/or sensitivity and/or accuracy and/or operating range of the sensor compared to sensors provided with a magnetic core surrounding the primary conductor. Thus, many current sensors for current sensing applications comprise a magnetic core made of a high permeability magnetic material, which surrounds a central aperture through which a main conductor carrying the current to be measured passes. However, it is difficult to provide a particularly compact current sensor with a magnetic core to minimize and/or reduce the weight of the device in which these components are installed. There are also many applications where current sensors are mounted on circuit boards, which in turn require adherence to predetermined connection package layouts or surface area or height limitations that require particularly compact arrangements. Depending on the voltage amplitude of the main conductor, this may lead to difficulties in achieving the required electrical creepage distance between the main conductor and the electrical conductor of the magnetic field detector circuit.

A PCB-mountable current sensor meeting the above-mentioned compactness, accurate measurement and economic manufacturing requirements is described in WO 2017/067849. In this sensor, the lead frame conductor means is overmolded with the housing base, and the magnetic field sensing unit is then mounted on the conductor means and connected thereto by wire bonding. The magnetic core is inserted over the main conductor and the magnetic field sensor before the housing cover is mounted over the magnetic core and the detector and clamped to the housing base. The interior of the housing may be unfilled (containing air), or may be filled with an insulating potting material. Although the magnetic core is held by the housing cover and base, small movements between the magnetic core and the housing can occur in the event of vibration or mechanical shock, creating stresses in the sensor that can cause failure or movement of the air gap relative to the magnetic field sensor, affecting sensor accuracy. Furthermore, in view of the small separation distance, especially in high current measurement applications, it may be difficult to avoid arcing tracking between the main conductor and the magnetic core or magnetic field detector. Deformation of the housing base and cover under thermal and mechanical stress can also exacerbate this problem.

Disclosure of Invention

It is an object of the present invention to provide a current sensor for mounting on a circuit board, having an integrated main conductor, a magnetic field detector and a magnetic core, which is accurate and reliable, yet very compact and robust, especially when subjected to mechanical and thermal stresses.

It would be advantageous to provide a current sensor having a high tracking resistance between the main conductor and the conductor of the magnetic field detector.

It would be advantageous to provide a current sensor having a large operating range.

It would be advantageous to provide a current sensor that is lightweight.

It would be advantageous to provide a current sensor that is easy to implement and economical to use.

The object of the invention is achieved by providing a current sensor according to claim 1 and a method of manufacturing a current sensor according to claim 11.

Disclosed herein is a current sensor comprising an insulator, a magnetic core comprising a central passage and a magnetic circuit gap, a magnetic field detector located in the magnetic circuit gap, and a sheet metal lead frame conductor arrangement comprising a primary conductor for carrying a current to be measured and a secondary conductor for connecting the magnetic field detector to an external circuit. The primary conductor includes a central portion extending through the central channel of the magnetic core, laterally extending arms extending from opposite ends of the central portion, and connection ends for connection to the outer conductor. The secondary conductor includes a plurality of conductors, each conductor including a sensing cell connection pad substantially aligned in the same plane as the central portion of the primary conductor, and a connection end for connection to an external circuit. The insulator includes an inner overmolded portion that surrounds a central portion of the primary conductor and forms a core guide that positions and insulates the core relative to the lead frame conductor arrangement.

The insulator further includes an outer overmolded portion molded over the inner overmolded portion, the magnetic core, the magnetic field sensor and the central portion of the lead frame conductor means.

Also disclosed herein is a method of manufacturing a current sensor, the method comprising:

a) stamping or etching a blank of a lead frame conductor arrangement in a lead frame made of a sheet metal strip, said blank being connected to the lead frame sheet metal strip by bridge attachments,

b) overmolding a central portion of the primary conductor and portions of the secondary conductor to form an inner overmolded portion,

c) the sensing element is then mounted on the lead frame conductor arrangement, and the sensing element is connected to the sensing connection pad of the secondary conductor,

d) the core is then mounted on the inner overmolded part, and optionally fixed with a dispensed amount of glue or with a clip,

e) subsequently overmolding an outer overmolded portion around the magnetic core, the sensing unit and the inner overmolded portion;

f) optionally, subsequently plating the exposed portions of the lead frame;

g) then stamping and forming the connecting end of the main conductor and the connecting end of the secondary conductor;

h) subsequently, the sensors are separated from the leadframe metal strip.

In an advantageous embodiment, the inner overmolded part is formed by injection molding of a thermoplastic polymer.

In an advantageous embodiment, the outer overmoulded part is formed by transfer moulding of a thermosetting polymer.

The inner overmolded portion (30) comprises or consists of a thermoplastic polymer.

In an advantageous embodiment, the thermoplastic polymer is selected from the group comprising PPS (polyphenylene sulfide), LCP (liquid crystal polymer), PA (polyamide).

The outer overmolded portion comprises or consists of a thermosetting polymer.

In an advantageous embodiment, the thermosetting polymer is a semiconductor grade epoxy molding compound.

In an advantageous embodiment, the inner overmolded portion comprises a main portion overmolded onto a central portion of the main conductor, the overmolded portion comprising core guide lateral guide edges engaging opposite sides of the limbs of the core for laterally positioning the limbs of the core relative to the guide frame conductor arrangement. The magnetic core guide may further comprise a base layer arranged for positioning against the lateral leg of the magnetic core.

In an advantageous embodiment, the inner overmolded part is constituted by said main part and said core guide.

In one embodiment, the magnetic core guide further comprises a base layer extending from the main portion and partially over the secondary conductor on a side of the guide frame conductor arrangement opposite to a side against which the sensing unit of the magnetic field detector is mounted and connected.

In an advantageous embodiment, on the side of the lead frame conductor arrangement abutting the sensing unit on which the magnetic field detector is mounted, the limb of the magnetic core is separated from the inner overmoulded part by a gap which is filled with the material of the outer overmoulded part.

In an advantageous embodiment, the outer overmoulding part completely encapsulates the magnetic core and the inner overmoulding part.

In an advantageous embodiment, the sensing unit is connected to the secondary conductor via a bond wire connection.

In one embodiment, the sensing unit is mounted on the leadframe conductor arrangement on a lower side of the leadframe conductor arrangement facing the mounting surface of the current sensor. In a further embodiment, the sensing unit is mounted on the lead frame conductor arrangement on an upper side of the lead frame conductor arrangement facing away from the mounting surface of the current sensor.

Drawings

Other objects and advantageous features of the invention will become apparent from the claims, the detailed description and the accompanying drawings, in which:

fig. 1a and 1b are perspective views of a current sensor according to an embodiment of the present invention.

Fig. 1c and 1d are partially cut-away perspective views of a current sensor according to a first embodiment of the present invention.

FIGS. 2a and 2b are exploded perspective views of the core and lead frame conductor arrangement of the current sensor of FIGS. 1 c-1 d, viewed from opposite sides;

FIGS. 3a and 3b are plan cross-sectional views of the core and lead frame conductor arrangement of the current sensor of FIGS. 1 c-1 d, viewed from opposite sides;

FIG. 3c is a side view of the core and lead frame conductor arrangement of the current sensor of FIGS. 1 c-1 d;

fig. 4a to 4d show in perspective views the manufacturing steps of a current sensor according to an embodiment of the invention;

FIG. 4e is a top view of the lead frame and current sensor of FIG. 4a showing the outer overmolded portion in cross section;

FIGS. 5a and 5b are plan views showing the manufacturing steps according to FIGS. 4b and 4c, respectively;

FIG. 6a is a perspective view of a current sensor according to a second embodiment of the present invention showing the outer overmolded portion in partial cutaway;

FIG. 6b is a cross-sectional view taken along line 6b-6b of FIG. 6 a;

FIG. 6a is a cross-sectional view taken along line 6c-6c of FIG. 6b with an upper portion of the outer overmolded portion removed;

fig. 7a and 7b are exploded perspective views of the core and lead frame conductor arrangement of the current sensor of fig. 6 a-6 c.

Detailed Description

Referring to the drawings, there is shown a current sensor according to an embodiment of the present invention, which comprises an insulator 10, a magnetic core 6 comprising a central passage 18 and a magnetic circuit gap 22, a magnetic field detector 8 located in the magnetic circuit gap 22, and a conductor arrangement 4 made of a lead frame. The lead frame conductor arrangement 4 comprises a main conductor 14 for carrying the current to be measured and a conductor 16 for connection to the magnetic field detector 8. The current sensor of the present invention is particularly suitable for open loop current measurement.

The main conductor 14 comprises a central portion 15, laterally extending arms 13 extending from opposite ends of the central portion 15, and connection terminals 17 at the free ends of the extending arms for connection to an external conductor through which the current to be measured flows. In particular, the external conductor may be connected to a circuit board (not shown) provided with conductive contacts for connection with the connection terminals 17. The conductive contacts may for example be in the form of conductive contact strips for surface mount connection of the connection terminals 17. The central portion 15 of the primary conductor 14 extends through the central passage 18 of the magnetic core.

The core is substantially U-shaped and is formed by an end branch 6a and lateral branches 6b, 6c extending from the end branch 6a to a free end 24, and a magnetic path gap 22 is formed between the lateral branches 6b, 6c near the free end 24.

The magnetic core 6 acts as a flux concentrator for the magnetic field detector 8 located in the magnetic circuit gap 22. The magnetic flux generated by the current flowing in the main conductor is concentrated through the magnetic path gap 22. The magnetic core is made of a magnetic material having a high magnetic permeability, and examples of such magnetic materials are FeSi or NiFe alloy, MnZn or other ferrite, nanocrystalline material, and amorphous material. The magnetic core according to embodiments of the present invention increases the signal level and provides good immunity against external magnetic fields compared to current sensors without a magnetic core, e.g. in which the magnetic field detector is located near the primary conductor without a flux concentrator.

In an advantageous embodiment, the free end 24 of the lateral branch is provided with a chamfer 25 on the outer side of the lateral branch, which reduces the amount of magnetic material required and reduces the fringe field.

The lead frame conductor means 4 is stamped or etched and made from a single piece of sheet metal, whereby the central portion 15 of the main conductor and the main portion of the magnetic field detector conductor 16 are substantially aligned and extend in the same main plane and have substantially the same thickness corresponding to the thickness of the sheet metal forming the conductor means. The connection end 17 of the main conductor 14 and the connection end 19 of the magnetic field detector conductor 16 may be bent out of the main plane to provide terminals for connection to an external circuit, in particular for connection to contact pads of an external circuit board.

The magnetic field detector conductor 16 comprises a plurality of conductors each comprising a connection end 19 for connection to an external circuit and a sensing element connection tab 21 in the main plane of the lead frame for connection to the magnetic field detector 8. The magnetic field detector conductor includes at least one pair of power supply terminals (e.g., one for power supply voltage Vc and the other for ground GND) and at least one signal output terminal Vout. The magnetic field detector conductor may further comprise a reference terminal Vref, a ground terminal and optionally a supplementary signal output terminal (e.g. for the over-current detection signal OCD).

The connection pads 21 may be provided in different shapes, surface areas and locations in order to optimally connect to the sensing unit 26. The magnetic field detector 8 comprises a sensing unit 26 and connection means, for example in the form of bond wires 27. In the embodiment shown, the connection piece 21 is connected to the magnetic field detector by a bonding wire connection 27. However, other interconnection means known per se in the art may be provided between the sensing unit 26 and the connection piece 21 of the lead frame conductor arrangement 4. For example, the interconnection means may comprise a so-called "flip chip" connection arrangement between the semiconductor substrate and the metal contact pads, so that, for example, solder balls interconnect the connection areas on the sensing elements 26 with the connection pads 21 of the lead frame conductor means 4.

In a preferred embodiment, the sensing unit 26 may be in the form of a hall sensor, per se well known in the art of current sensors, formed in a semiconductor substrate (e.g., a silicon substrate). However, other sensing unit technologies, such as fluxgate type magnetic field detectors or giant magnetoresistance type magnetic field sensors, may also be employed in the present invention. A hall sensor formed in a substantially planar semiconductor substrate is advantageous in view of its low cost, compactness and robustness.

The sensing unit 26 may also be an arrangement of more than one semiconductor chip, for example a high-sensitivity hall chip provided adjacent to the signal processing chip.

The magnetic field detector conductor 16 and the main conductor central portion 15 are advantageously in the same plane (main plane) or substantially the same plane and are held together by an inner overmolded portion 20 of the insulator 10.

In the embodiment shown in fig. 2a to 3c, the inner overmoulded part 20 of the insulator 10 is overmoulded on some parts of the secondary conductor of the lead frame conductor arrangement 4, while the connecting piece 21 of the magnetic field detector conductor 16 is exposed. The inner overmolded portion 20 and the lead frame conductor means 4 present a substantially planar mounting surface with respect to the connecting tabs 21 of the magnetic field detector conductors 16.

In one embodiment, as shown for example in fig. 2a to 3c, the sensing unit 26 is mounted on the bottom side of the leadframe device, facing the mounting plane of the conductor connection ends 17, 19.

The inner overmold portion 20 is overmolded around the central portion 15 of the primary conductor 14. The inner overmolded portion 20 provides a dielectric insulation layer between the magnetic core and the main conductor and optionally also provides a positioning guide between the main conductor and the central passage of the magnetic core, also ensuring correct positioning of the sensing unit 26 in the magnetic circuit gap 22.

The lead frame conductor arrangement 4 and magnetic core 6 with the internal overmold portion 20 of the present invention provides a particularly compact arrangement, yet allows for good separation and insulation of the primary conductor relative to the magnetic field detector conductor 16. The central portion 15 of the main conductor can be provided with a large unreduced cross-section within a compact connection package layout (i.e. the surface area occupied by the current sensor when positioned on an external circuit board) and at the same time have a good insulation separation distance with respect to the sensing unit of the magnetic field detector.

The inner over-mold portion 20 may advantageously include a core guide 32, the core guide 32 including lateral guide edges 32b, the lateral guide edges 32b flanking opposite sides of the core 6 to laterally position the core relative to the lead frame arrangement 4 and the sensing unit 26.

The inner overmolded portion 20 includes a main portion 30 overmolded onto the central portion 15 of the main conductor 14.

In a first embodiment, as shown in fig. 2a to 3c, the inner overmolded portion 20 comprises a secondary portion 31, the secondary portion 31 extending from the primary portion 30 and being partially overmolded on a portion of the sensing unit connection pad 21 of the secondary conductor 16. The core guide 32 is substantially molded on the side 4a of the lead frame conductor arrangement 4 opposite to the side 4b on which the sensing unit 26 of the magnetic field detector is mounted.

In the illustrated embodiment of fig. 2a to 3c, the core guide 32 comprises a base wall or layer 32a on the upper side 4b of the lead frame conductor arrangement, which presents a surface 32a against which the inner side 44 of the upper leg 6c of the core is positioned. The base layer 32a provides an insulating layer that defines the distance between the magnetic core and the primary and secondary conductors 14, 16. As best seen in fig. 3c, on the opposite side of the base layer 32a, the opposite lateral leg 6b of the magnetic core 6 is spaced from the lead frame conductor means 4 and the inner over-mold portion 20 by a gap 35. The sensing unit 26 and the bondwire connection 27 are located in the magnetic circuit gap 22 between the free ends of the lateral branches 6b, 6c, which gap is filled with the material of the outer overmoulded part 34.

In a second embodiment, as shown in fig. 6a to 7b, the inner overmoulded portion 20 does not extend over a portion of the connection piece 21 of the sensing unit of the secondary conductor 16, but is spaced apart from it by a gap which is filled with the outer overmoulded portion 34. An advantage of this configuration is to ensure a long electrical creepage distance between the primary conductor 14 and the secondary conductor 16. In the interface between the inner and outer overmold portions 20, 34, particularly where two different materials are used, the chemical bond between the materials of the inner and outer overmold portions may be incomplete or such that the internal creepage current can damage the insulation barrier. In this embodiment, the inner overmolded portion surrounds the primary conductor only and has no interface with the secondary conductor 16, and the outer overmolded portion 34 surrounds the secondary conductor 16 without interfacing with the inner overmolded portion along the secondary conductor. Thus, there is no interface between the inner and outer overmolded portions along portions of the secondary conductor 16, thereby avoiding creepage along the interface between the overmolded portions.

The inner over-mold portion 20 is used to assemble the magnetic core 6 to the lead frame conductor arrangement 4, providing structural rigidity, positioning and insulation between the lead frame conductor arrangement 4 and the magnetic core 6, as well as between the primary and secondary conductors.

In a preferred embodiment, the inner over-mold portion 20 is formed of a thermoplastic polymer that is preferably injection molded onto the lead frame conductor means 4 while the lead frame conductor means 4 is still formed as a blank and attached to the lead frame 40 during the manufacturing process. In view of the rapidity of the injection molding process, including the rate of hardening of the thermoplastic material after injection, and the ease of passing the lead frame through the injection mold in an economical manner, the process is highly advantageous for mass production. The overmolding of the inner overmolded portion 20 (e.g., as opposed to applying tape) can be automated very well before the magnetic field detector 8 is mounted and interconnected to the secondary conductor, and provides an insulating layer completely surrounding the main leads in the vicinity of the magnetic field detector chip and other conductive portions of the secondary side.

In one variation, the inner overmolded portion 20 may alternatively be formed using a transfer molding process utilizing a thermoset plastic (e.g., an epoxy molding compound).

The lead frame 40 is formed from a sheet metal strip 41, which sheet metal strip 41 is stamped in a stamping die to blank out portions of the metal strip to form a blank shape of the lead frame conductor means and its attachments attached to the metal strip during the stamping and forming process, and such stamping process is known per se in the art; for relatively low throughput, the etching process may be more economical.

The magnetic core 6 and the sensing unit 26 are assembled to the lead frame conductor arrangement while the lead frame conductor arrangement is still attached to the lead frame 40. The lead frame 40 may thus be formed by injection molding, transfer molding or compression molding a mold to form the inner overmold portion 20. In one embodiment, the inner overmolded portion may advantageously be made of a thermoplastic material.

In one variation, the inner overmolded portion may also be made of a thermoset material in a transfer molding process.

As best shown in fig. 2b, in the first embodiment, the inner overmolded portion 20 includes an opening 33 in the base layer 32 a. The opening 33 is located opposite the sensing unit 26 mounted on the opposite side 4a of the lead frame conductor arrangement 4. The openings 33 may serve to avoid overflow of material on the surface portions of the leadframe conductor arrangement 4 where the sensing cells 26 are located and abut during the molding process.

In the manufacturing process, with the lead frame conductor arrangement 4 connected to the lead frame 40, after connecting the sensing unit 26 to the secondary conductor 16 and mounting the magnetic core 6 on the inner overmoulded part, the above assembly is fed into a transfer moulding mould having a mould cavity substantially corresponding to the housing of the outer overmoulded part 34, and a thermosetting polymer is injected into the mould cavity to fill the cavity to form the outer overmoulded part. Compared to thermoplastic polymers, thermosetting polymers can generally have a much lower viscosity, thereby advantageously filling the space between the bond wires 27 around the sensing unit 26 and between the conductors 14, 16 of the conductor lead arrangement and also into the space between the magnetic core 6 and the respective conductor, with relatively low hydrodynamic forces. Thus, the thermoset polymer forms an excellent insulating barrier between the lead frame conductor arrangement, in particular between the primary and secondary conductors, and between the primary and magnetic cores and the sensing unit in a compact and robust arrangement. In particular, the thermoset outer overmold portion 34 provides a particularly strong and stable securement of the magnetic core 6 to the lead frame conductor arrangement 4. Furthermore, the formation of the inner overmold, the connection of the sensing unit to the lead frame, the molding of the magnetic core on the lead frame arrangement, and the subsequent overmolding of the outer overmold portion may advantageously be performed while the lead frame conductor arrangement is formed as a blank that is still attached to the lead frame, to facilitate precise assembly of the components and efficiency of the production process.

As best seen in fig. 4a and 5a, the lead frame conductor arrangement is of planar shape, with the primary and secondary conductors in the plane of the metal strip 41. After forming the outer overmolded portion 34, the primary and secondary conductors 14, 16 may be separated from the sheet metal strip 41 (fig. 4b and 4c) and bent into their final shape (fig. 4d) before separating the current sensor 2 from the lead frame metal strip 41.

As shown in fig. 4a, the leadframe conductor arrangement is connected to the leadframe 40 via a plurality of bridge attachments 42a, 42b, 42c, including a primary conductor bridge attachment 42a, a secondary conductor bridge attachment 42b, and a sensor support attachment 42 c. Further, the leadframe conductor arrangement is connected to the leadframe via conductor end attachments 43a, 43b (i.e. primary conductor end attachment 43a and secondary conductor end attachment 43 b). In a subsequent step, as shown in fig. 4b, the primary and secondary conductors are cut out of the leadframe strip 41 by means of various associated cutting dies 45, as best shown in fig. 5a and 5 b.

During the stamping and subsequent forming and assembly steps described above, the various bridge attachments 42a, 42b between the secondary conductor and the leadframe strip 41 and between the primary conductor and the leadframe strip 41 serve to stabilize and provide secure positioning of the leadframe conductor arrangement.

The primary and secondary conductors can then be bent into their final shape, as shown in fig. 4d, in order to be connected to an external circuit board with the sensor remaining connected to the leadframe strip 41. In a subsequent step, the sensors may be cut from the leadframe strip 41 by detaching the sensor support attachments 42 c.

Thus, a particularly robust, well-insulated and compact sensor with a lead frame conductor arrangement may be provided in an efficient, accurate and economical manufacturing process.

List of reference signs used

Current sensor 2

Lead frame conductor arrangement 4

Main conductor 14

Laterally extending arm 13

Center portion 15

(Circuit Board) connecting terminal 17

Secondary (magnetic field detector) conductor 16

(Circuit Board) connecting terminal 19

Sensing unit connecting sheet 21

Magnetic core 6

Central passage 18

Magnetic circuit gap 22

End branch 6a

Lateral branches 6b, 6c

Free end 24

Magnetic field detector 8

Sensing unit 26

Connection device (bonding wire) 27

Insulator 10

Inner cover molding part 20

The main section 30

Minor part 31

Magnetic core guide 32

Base 32a

Opening 33

Side guide 32b

Outer overmolded portion 34

Lead frame 40

Sheet metal strip 41

Bridge attachment 42

Main conductor bridge attachment 42a

Secondary conductor bridge attachment 42b

Sensor support attachment 42c

Conductor end attachment 43

Main conductor terminal 43a

Secondary conductor end 43b

Stamping (blanking) die 45

External circuit board

Contact plate