Integrated circuit current transducer

Abstract

Integrated circuit current transducer (1) comprising at least one integrated circuit (IC) chip (2), a primary conductor arrangement (3) comprising at least one primary winding (6, 6a, 6b), a secondary conductor arrangement (4), and an insulating housing (5), the IC chip having a first active side (2a) and a second side (2b), at least the first active side having active portions including electrical connection terminals (11) for connection to power and signal transmission conductors and a magnetic field sensor (12) arranged at or close to the surface of the active side adjacent said at least one primary winding. The primary conductor arrangement, the secondary conductor arrangement, and a portion of the insulating housing comprise or consist of a molded interconnect substrate (MIS) formed of successive layers.

Description

[0001] P2970PC00

[0002] INTEGRATED CIRCUIT CURRENT TRANSDUCER

[0003] The present invention relates to an open-loop integrated circuit current transducer for surface mounting on a circuit board.

[0004] It is known to provide open-loop current transducers having surface mount electrical connections for mounting on a circuit board. In many applications, there is an advantage in having a very compact and low height current transducer having an integrated primary conductor within an insulative housing. Such coreless current transducers may include an integrated circuit (IC) chip having an active sensing layer thereon detecting the magnetic field induced by a current to be measured flowing in a primary conductor integrated within the current transducer, the integrated circuit chip being electrically connected to secondary contacts that supply power and allow transmission of the measurement signal to the external circuit board.

[0005] Despite the compacity of conventional IC based current transducers, there is a continuous desire to further reduce the size and increase the measurement accuracy of such transducers. There are also many applications in which operating conditions may be quite harsh, for instance sensing systems installed in vehicles, that require robust components, or that need to measure currents in high voltage environments.

[0006] In view of the foregoing, it is an object of the invention to provide an integrated circuit openloop current transducer that is accurate and very compact.

[0007] It is advantageous to provide an IC open-loop current transducer that can withstand harsh environments and high voltages.

[0008] It is advantageous to provide an IC open-loop current transducer that has a high measurement sensitivity.

[0009] It is advantageous to provide an IC open-loop current transducer adapted for surface mounting on a circuit board.

[0010] It is advantageous to provide an IC open-loop current transducer that is economical to manufacture.P2970PC00

[0011] Objects of the invention have been achieved by providing an open loop current transducer according to the independent claims.

[0012] Dependent claims set out various advantageous features of embodiments of the invention.

[0013] Disclosed herein is an integrated circuit current transducer comprising at least one integrated circuit (IC) chip, a primary conductor arrangement comprising at least one primary winding, a secondary conductor arrangement, and an insulating housing, the IC chip having a first active side and a second side, at least the first active side having active portions including electrical connection terminals for connection to power and signal transmission conductors and a magnetic field sensor arranged at or close to the surface of the active side adjacent said at least one primary winding.

[0014] The primary conductor arrangement, the secondary conductor arrangement, and a portion of the insulating housing comprise or consist of a molded interconnect substrate (MIS) formed of successive layers, each consisting of a patterned metal layer filled therebetween by a molded insulating layer, the IC chip being mounted on top of the molded interconnect substrate (MIS), bonding wires or a flip chip beads connecting connection terminals of the IC chip to IC connection pads of the secondary conductor arrangement, the insulating housing further comprising an overmold portion covering at least the IC chip and a top surface of the molded interconnect substrate.

[0015] In one aspect of the invention, the primary conductor arrangement comprises two planar spiral-shaped coils interconnected by an interconnecting bridge positioned in a layer offset from the planar spiral-shaped windings.

[0016] In an advantageous embodiment, the interconnecting bridge is connected to respective ends of the two primary conductor windings at respective centers of said windings, second ends of said two windings being interconnected to respective primary conductor terminals configured for surface mount connection to an external circuit board.

[0017] In another aspect of the invention, the primary conductor winding comprises a plurality of conductor loops offset from each other and separated from each other by an insulating layer of the molded interconnect substrate, the primary conductor loops connected together in series to form a continuous winding, the interconnection formed by conductive posts extending through said separating insulating layer.

[0018] In an advantageous embodiment, the secondary conductor arrangement comprises surfaceP2970PC00

[0019] mount connection terminals arranged along an edge of the insulating housing and presenting exposed circuit board connection pads for surface mount connection to an external circuit board, and an IC die terminal extension extending from the surface mount connection terminals to an end positioned proximate the IC chip and comprising IC connection pads for interconnection to the connection terminals of the IC chip with said bond wires or flip chip connection.

[0020] In an advantageous embodiment, a material of the insulating housing portion of the molded interconnect substrate is an epoxy resin.

[0021] In an advantageous embodiment, the integrated circuit chip is mounted on a mounting surface of the molded interconnect substrate having only the IC connection pads of the secondary conductor arrangement exposed at said mounting surface.

[0022] In an advantageous embodiment, the IC chip is mounted on an insulating sheet mounted on a top surface of the molded interconnect substrate, the insulating sheet having an electrical breakdown resistance greater an electrical breakdown resistance of a material of the insulating portion of the molded interconnect substrate.

[0023] In an advantageous embodiment, the insulating sheet is made of a polyimide polymer.

[0024] Further advantageous features of the invention will be apparent from the following detailed description of embodiments of the invention and the accompanying illustrations.

[0025] Brief description of the figures

[0026] Figures 1a and 1b are perspective views of an integrated circuit (IC) current transducer according to an embodiment of the invention, an insulating housing portion being shown transparent, figure 1a viewing towards a top side and where an integrated circuit die is shown transparent, and figure 1b viewing toward a mounting side;

[0027] Figure 2 is a perspective view of an integrated circuit (IC) current transducer according to another embodiment of the invention, an insulating housing portion being shown transparent;

[0028] Figure 3 is a perspective view illustrating layers L1 to L7 of an integrated circuit (IC) current transducer during manufacturing of the IC current transducer of figure 2;

[0029] Figure 4 illustrates steps during manufacturing of an IC current transducer according to an embodiment of the invention;P2970PC00

[0030] Figure 5 illustrates further steps during manufacturing of the IC current transducer according to embodiments of the invention;

[0031] Referring to the figures, an electric current transducer 1 for mounting on an external circuit board, comprises at least one integrated circuit (IC) chip 2, a primary conductor arrangement 3, a secondary conductor arrangement 4, and an insulating housing 5.

[0032] The primary conductor arrangement comprises primary conductor terminals 7, configured on the one hand for connection to conductive traces on an external circuit board (not shown), and on the other hand to the primary conductor layer arrangement 3 formed within the insulating housing.

[0033] The IC chip 2 may be in the form of a semiconductor die having a first active side 2a and a second side 2b, at least the first active side 2a having active portions including electrical connection terminals 11 for connection to power and signal transmission conductors and a one or more magnetic field sensors 12 arranged at or close to the surface of the first side.

[0034] The magnetic field sensor may for instance comprise a first magnetic field sensing portion 12a and a second magnetic field sensing portion 12b at a certain distance from the first magnetic field sensing portion. The two magnetic field sensing portions may for instance be configured for a differential measurement of the magnetic field. In embodiments it is however possible to have a magnetic field sensor with only one magnetic field sensing portion. The magnetic field sensing portion(s) may comprise a Hall effect sensor, or a giant magnetoresistive sensor, or a tunnel magneto resistance (TMR) sensor, or other forms of magnetic field sensors such that are perse well known in the art.

[0035] It may further be noted that the transducer may comprises more than one IC chip. There may be a plurality of IC chips with magnetic field sensors in the transducer, for instance two IC chips, each provided with magnetic field sensors.

[0036] For instance in embodiments with a pair of TMR sensors, there may be two IC chips, one for each TMR sensor, mounted over the primary conductor arrangement.

[0037] The transducer may also include an IC chip without a magnetic field sensor, for instance a diode chip, for instance comprising diodes for temperature compensation and for electrostatic discharge protection (ESD). The electrical connection terminals 11 for connection to theP2970PC00

[0038] secondary conductor arrangement may be provided on any one IC chip or distributed over a plurality of IC chips.

[0039] The IC chip 2 may for instance be in the form of a CMOS die although other types of semiconductor integrated circuit dies with magnetic field sensing portions perse known in the art may be used. The semi-conductor die does not need to be further described, such semiconductor dies with magnetic field sensing portions and connection terminals being per se well known in the art.

[0040] In a preferred embodiment the magnetic field sensing portions comprise Hall effect sensors and the IC chip is a CMOS die.

[0041] The primary conductor arrangement 3 comprises one or two primary conductor windings 6, 6a, 6b depending on the variant.

[0042] In one variant, the winding may have a planar spiral shaped coil with spire portions of varying diameter, as illustrated in figures 1a and 1b. The two spiral shaped windings may be connected together in series, for instance by way of a conductive interconnecting bridge 6c interconnecting ends at the centres of the coils. The spire portions of the coils may have different shapes, for instance generally circular as illustrated in figures 1a, 1b, or rectangular or square as illustrated in figure 4, or various other polygonal or oval shapes. The second ends of the respective spiral shaped coils are connected to respective primary conductor terminals 7.

[0043] In another variant, the winding may have a plurality of stacked loops 61, 62, for instance of substantially constant diameter or similar dimensions, for instance as illustrated in figure 2. The embodiment of figure 2 shows by way of example a winding with two loops 61, 62 of similar shape and dimensions forming a winding 6 with two turns. Although the embodiment illustrated in figure 2 has two primary conductor loops, in variants there may be only one primary conductor loop, or three or more primary conductor loops. The primary conductor loops may have different shapes, for instance generally circular, or rectangular or square as illustrated, or various other polygonal or oval shapes. The two ends of the winding are connected to respective primary conductor terminals 7.

[0044] A primary current flowing in the primary conductor windings generates a magnetic field that is measured by the magnetic field sensing portion(s) 12, 12a, 12b of the IC chip 2.P2970PC00

[0045] The secondary conductor arrangement 4 interconnects the IC chip 2 to power and signal connections of an external circuit to which the current transducer is intended to be connected. The secondary conductor arrangement comprises a plurality of secondary conductors including surface mount connection terminals 8 which may be for instance arranged in a row presenting contact pads intended for surface mount solder or welding connection, as perse known in the art, to circuit traces of an external circuit board. The surface mount connection terminals 8 are thus positioned proximate an outer edge of the transducer insulating housing 5. The secondary conductors may further comprise IC die terminal extensions 13 connected at one end to the surface mount connection terminals 8 and at the other end presenting IC connection pads 14 disposed proximate the connection terminals 11 of the IC chip 2. In the illustrated embodiments of figures 1a, 1b and 2, the IC connection pads positioned proximate the IC chip 2 allowing bond wire connections between the connection terminals 11 of the IC chip 2 and the IC connection pads 14 of the secondary conductors.

[0046] According to an aspect of the invention, the primary conductor arrangement 3 and secondary conductor arrangement 4 comprise or consist of a molded interconnect substrate MIS comprising conductive tracks formed within a molded insulating substrate in a layer-by-layer manufacturing process. As best illustrated in figure 3 and figure 4, the process starts with a carrier layer L1 on which a conductive metal layer, preferably a copper layer, is deposited and patterned, for instance using a photoresist material. Further copper layers may be deposited on this copper layer with different patterns in order to provide for instance vertical interconnecting posts 60 for conductive interconnection to subsequently deposited upper conductive layers. An insulating layer is then molded between the patterned conductive layer and possibly over the conductive layer, for instance using a perse known transfer molding process (used for instance for overmolding silicon chips for packaging). A grinding step is then applied to grind the upper surface of the molded layer to expose the vias or any conductive pads for interconnection to a subsequent patterned conductive layer.

[0047] Layers L2, L3, L4, L5, L6 in figure 3 show subsequent patterned metal and insulating layers in the above-mentioned manufacturing process. An enlarged perspective view of the primary and secondary conductors and insulating layer substrate at the stage of layer L5 is shown for more clarity.

[0048] Once the fully built up primary and secondary conductors and overmolded insulating substrate formed layer-by-layer is completed, thus forming the molded interconnect substrate MIS, the IC chip 2 may be mounted thereon.P2970PC00

[0049] The IC chip may be fixed for instance by adhesive bonding onto the molded interconnect substrate MIS and subsequently interconnected to the secondary conductors 4 by bond wires as illustrated in the embodiments of figures 1a to 3, or in a flip chip arrangement as illustrated in figure 5 (step F2a of the flip chip option). Although in figure 3 layer L7 shows the IC die terminal extensions 13, these may in fact be buried beneath a top insulating layer of the molded interconnect substrate MIS presenting only the IC connection pads 14 which may be formed as conductive posts built up from ends of the IC die terminal extensions 13. Such exposed IC connection pads 14 may also be provided for a flip chip interconnection.

[0050] The IC chip may also be mounted on an insulating sheet mounted on a top surface of the molded interconnect substrate, the insulating sheet having an electrical breakdown resistance greater an electrical breakdown resistance of a material of the insulating portion of the molded interconnect substrate. In an advantageous embodiment, the insulating sheet is made of a polyimide polymer.

[0051] After assembly of the IC chip 2 on the molded interconnect substrate MIS, a subsequent overmolding 5b may be effected, here also for instance by a transfer molding process perse known, in order to embed the IC chip in the insulating housing 5. It may be noted that the overmold 5b may extend beyond edges of the molded interconnect substrate and may comprise additional features (not shown) that may depend on the configuration of an external circuit board or circuit components to which the transducer is mounted and coupled.

[0052] Figures 4 and 5 also illustrate steps S1 to S12 (Fig. 4) and P1 to P2c, F2a, P3 to P5 (Fig. 5) of various embodiments of a manufacturing process of the molded interconnect substrate MIS and subsequent final transducer. In preferred embodiments, a plurality of transducers are formed with a common carrier and combined molded interconnect substrate MIS, overmolded with the remaining insulating housing and subsequently cut into individual transducers.

[0053] Compared to conventional technologies in which the primary and secondary conductor arrangements may be formed by printed circuit board (PCB) manufacturing technology or using stamped and formed lead frames the molded interconnect substrate allows to produce thicker conductor layers than in for instance PCB technology while ensuring accurate cross-sectional dimensions of the conductors due to the intermediate grinding steps that equalize the thicknesses of the conducting and insulating layers after each depositing and molding step. Moreover, the progressive molding and metallization steps allows to have a very compact primary and secondary conductor arrangements in a 3-dimensional volume that allow to optimize the position and intensity of the magnetic field generated by the primaryP2970PC00

[0054] conductor relative to the magnetic field sensors on the integrated circuit chip as well as ensure good insulation between the primary and secondary conductor arrangements in a very compact form.P2970PC00

[0055] List of references

[0056] electric current transducer 1

[0057] integrated circuit chip 2

[0058] first side (active side) 2a

[0059] magnetic field sensing portion 12 first magnetic field sensing portion 12a second magnetic field sensing portion 12b connection terminals 11

[0060] second side 2b

[0061] molded interconnect substrate MIS

[0062] primary conductor arrangement 3

[0063] primary conductor loop(s) 6

[0064] first primary conductor loop 6a second primary conductor loop 6b connection end terminals interconnecting bridge 6c

[0065] primary conductor terminals 7 secondary conductor arrangement 4

[0066] surface mount connection terminals 8 Circuit board connection side

[0067] IC die terminal extension 13

[0068] IC connection pad 14 secondary conductor bond wires 9 insulating housing 5

[0069] MIS portion 5a

[0070] Die overmold portion 5b

Claims

P2970PC00Claims1. Integrated circuit current transducer (1) comprising at least one integrated circuit (IC) chip (2), a primary conductor arrangement (3) comprising at least one primary winding (6, 6a, 6b), a secondary conductor arrangement (4), and an insulating housing (5), the IC chip having a first active side (2a) and a second side (2b), at least the first active side having active portions including electrical connection terminals (11) for connection to power and signal transmission conductors and a magnetic field sensor (12) arranged at or close to the surface of the active side adjacent said at least one primary winding, characterized in that the primary conductor arrangement, the secondary conductor arrangement, and a portion of the insulating housing comprise or consist of a molded interconnect substrate (MIS) formed of successive layers, each consisting of a patterned metal layer filled therebetween by a molded insulating layer (5a), the IC chip being mounted on top of the molded interconnect substrate (MIS), bonding wires or a flip chip beads connecting connection terminals (11) of the IC chip to IC connection pads (14) of the secondary conductor arrangement, the insulating housing further comprising an overmold portion (5b) covering at least the IC chip and a top surface of the molded interconnect substrate, wherein the primary conductor arrangement comprises two planar spiral-shaped coils interconnected by an interconnecting bridge (6c) positioned in a layer offset from the planar spiral-shaped windings.

2. The transducer of claim 1 wherein the interconnecting bridge (6c) is connected to respective ends of the two primary conductor windings at respective centers of said windings, second ends of said two windings being interconnected to respective primary conductor terminals (7) configured for surface mount connection to an external circuit board.

3. The transducer of any preceding claim wherein a material of the insulating housing portion (5a) of the molded interconnect substrate is an epoxy resin.

4. The transducer of any preceding claim wherein the integrated circuit chip is mounted on a mounting surface of the molded interconnect substrate (MIS) having only the IC connection pads (14) of the secondary conductor arrangement exposed at said mounting surface.

5. The transducer of any preceding claim wherein the IC chip is mounted on an insulating sheet mounted on a top surface of the molded interconnect substrate, the insulating sheet having an electrical breakdown resistance greater an electrical breakdown resistance of a material of the insulating portion of the molded interconnect substrate.

6. The transducer of the preceding claim wherein the insulating sheet is made of aP2970PC00polyimide polymer.

7. The transducer of any preceding claim wherein the secondary conductor arrangement (4) comprises surface mount connection terminals (8) arranged along an edge of the insulating housing and presenting exposed circuit board connection pads for surface mount connection to an external circuit board, and an IC die terminal extension (13) extending from the surface mount connection terminals to an end positioned proximate the IC chip and comprising IC connection pads (14) for interconnection to the connection terminals (11) of the IC chip with said bond wires or flip chip connection.

8. Integrated circuit current transducer (1) comprising at least one integrated circuit (IC) chip (2), a primary conductor arrangement (3) comprising at least one primary winding (6, 6a, 6b), a secondary conductor arrangement (4), and an insulating housing (5), the IC chip having a first active side (2a) and a second side (2b), at least the first active side having active portions including electrical connection terminals (11) for connection to power and signal transmission conductors and a magnetic field sensor (12) arranged at or close to the surface of the active side adjacent said at least one primary winding, characterized in that the primary conductor arrangement, the secondary conductor arrangement, and a portion of the insulating housing comprise or consist of a molded interconnect substrate (MIS) formed of successive layers, each consisting of a patterned metal layer filled therebetween by a molded insulating layer (5a), the IC chip being mounted on top of the molded interconnect substrate (MIS), bonding wires or a flip chip beads connecting connection terminals (11) of the IC chip to IC connection pads (14) of the secondary conductor arrangement, the insulating housing further comprising an overmold portion (5b) covering at least the IC chip and a top surface of the molded interconnect substrate, wherein the at least one primary conductor winding comprises a plurality of conductor loops (61, 62) offset from each other and separated by an insulating layer of the molded interconnect substrate (MIS), the primary conductor loops connected together in series to form a continuous winding, the interconnection formed by conductive posts (60) extending through said separating insulating layer.

9. The transducer of the preceding claim wherein a material of the insulating housing portion (5a) of the molded interconnect substrate is an epoxy resin.

10. The transducer of any preceding claim 8-9 wherein the integrated circuit chip is mounted on a mounting surface of the molded interconnect substrate (MIS) having only the IC connection pads (14) of the secondary conductor arrangement exposed at said mounting surface.P2970PC0011. The transducer of any preceding claim 8-10 wherein the IC chip is mounted on an insulating sheet mounted on a top surface of the molded interconnect substrate, the insulating sheet having an electrical breakdown resistance greater an electrical breakdown resistance of a material of the insulating portion of the molded interconnect substrate.

12. The transducer of the preceding claim wherein the insulating sheet is made of a polyimide polymer.

13. The transducer of any preceding claim 8-12 wherein the secondary conductor arrangement (4) comprises surface mount connection terminals (8) arranged along an edge of the insulating housing and presenting exposed circuit board connection pads for surface mount connection to an external circuit board, and an IC die terminal extension (13) extending from the surface mount connection terminals to an end positioned proximate the IC chip and comprising IC connection pads (14) for interconnection to the connection terminals (11) of the IC chip with said bond wires or flip chip connection.

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