SENSOR AND MANUFACTURING METHOD

Abstract

A method for manufacturing a sensor for an automotive vehicle, the sensor includes an integrated circuit and a magnetic element. The method includes the steps of arranging the integrated circuit in a housing of a support zone of a leadframe formed in a metal base plate; the leadframe including branches constituting electrical tracks, electrically connecting the integrated circuit to the branches, placing the magnetic element against the support zone in line with the integrated circuit and at a predetermined fixed distance from the integrated circuit so as to form a space between the magnetic element and the integrated circuit, overmolding the assembly formed by the support zone, the integrated circuit and the magnetic element with a polyepoxide material so as to obtain an internal overmolding, overmolding the internal overmolding with a thermoplastic material so as to obtain the sensor.

Claims

1. A method for manufacturing a sensor for an automotive vehicle, said sensor comprising an integrated circuit and a magnetic element, said method comprising: arranging the integrated circuit in a housing of a support zone of a leadframe formed in a metal base plate; said leadframe comprising branches constituting electrical tracks; electrically connecting the integrated circuit to said branches; placing the magnetic element against the support zone in line with the integrated circuit and at a predetermined fixed distance from said integrated circuit so as to form a space between the magnetic element and the integrated circuit; overmolding the assembly formed by the support zone, the integrated circuit and the magnetic element with a polyepoxide material so as to obtain an internal overmolding; and overmolding the internal overmolding with a thermoplastic material so as to obtain the sensor.

2. The method as claimed in claim 1, comprising, prior to the step of overmolding with polyepoxide material, a step of placing an assembly of passive electronic components, referred to as “passive” assembly, comprising at least one passive electronic component, on a zone referred to as “passive” zone of the leadframe, which zone is different than the support zone, the step of overmolding with polyepoxide material further comprising the overmolding of said passive assembly so as to form a passive entity, distinct from the internal overmolding, and which are connected to said internal overmolding by the branches of the leadframe.

3. The method as claimed in claim 1, comprising, during the step of overmolding with polyepoxide material, the overmolding of a middle zone of the leadframe, neighboring the support zone, so as to form a positioning member designed to receive the internal overmolding.

4. The method as claimed in claim 2, comprising, between the step of overmolding with polyepoxide material and the step of overmolding with thermoplastic material, at least one step of bending of the leadframe.

5. The method as claimed in claim 4, wherein the bending comprises folding the internal overmolding over against the positioning member.

6. The method as claimed in claim 5, the leadframe comprising two lateral branches and the internal overmolding comprising two lateral slots which are each designed to receive and hold one of said lateral branches, the method comprises, during the folding of the internal overmolding over against the positioning member, a step of clipping the lateral branches into the slots.

7. The method as claimed in claim 4, wherein, when the sensor comprises a passive entity, the overmolding of said passive entity comprises a portion of which the shape complements a portion of the internal overmolding, and the bending comprises the folding of the internal overmolding over onto the passive entity.

8. The method as claimed in claim 1, comprising, between the step of overmolding with polyepoxide material and the step of overmolding with thermoplastic material, a step of cutting the leadframe in order to release it from the base plate.

9. A sensor for an automotive vehicle, said sensor comprising an electronic module and an external overmolding, produced using a thermoplastic material and encapsulating said electronic module, said electronic module comprising: a metal leadframe comprising a plurality of conducting branches and a support zone comprising a housing; and an internal overmolding, produced using a polyepoxide material and comprising an integrated circuit, placed in said housing, and a magnetic element placed against said support zone and in line with the integrated circuit at a predetermined fixed distance from said integrated circuit so as to form a space between the magnetic element and the integrated circuit.

10. An automotive vehicle comprising a sensor as claimed in claim 9.

11. The method as claimed in claim 5, wherein the bending (E8) comprises folding the internal overmolding over against the positioning member.

12. The method as claimed in claim 1, comprising, between the step of overmolding with polyepoxide material and the step of overmolding with thermoplastic material, at least one step of bending of the leadframe.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Further features and advantages of aspects of the invention will become more clearly apparent from reading the following description. This description is purely illustrative and must be read with reference to the accompanying drawings, in which:

[0040] FIG. 1 is a perspective view of one embodiment of a sensor according to an aspect of the invention,

[0041] FIG. 2 is a perspective view of the electronic module of the sensor of FIG. 1,

[0042] FIG. 3 is a perspective view of the leadframe of the sensor of FIG. 1,

[0043] FIG. 4 is a side view of the leadframe of FIG. 3,

[0044] FIG. 5 is a perspective view of the integrated circuit of the sensor of FIG. 1,

[0045] FIG. 6 is a perspective view of the magnet of the sensor of FIG. 1,

[0046] FIG. 7 is a partial perspective view of the sensor, from above, illustrating the leadframe of FIG. 3 over which the internal overmolding, the positioning member and the passive entity are overmolded,

[0047] FIG. 8 is a perspective view of the sensor of FIG. 7, from beneath,

[0048] FIG. 9 illustrates one embodiment of the method of manufacture according to an aspect of the invention,

[0049] FIG. 10 is a perspective view of a base plate in which two leadframes are formed,

[0050] FIG. 11 is a partial perspective view of the support zone of one of the leadframes of the base plate of FIG. 10, the housing of which receives an integrated circuit,

[0051] FIG. 12 illustrates the base plate of FIG. 10 on which two magnetic elements are placed,

[0052] FIG. 13 illustrates the base plate of FIG. 12, after the formation of the internal overmolding, of the positioning member and of the passive entity,

[0053] FIG. 14 illustrates the base plate of FIG. 13 in which the two internal overmoldings have been folded over onto the positioning member and the passive entity to form two electronic modules.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] The sensor according to an aspect of the invention is intended to be mounted in a vehicle, notably an automotive vehicle, in line with an element capable of causing the magnetic field to vary, for example such as a target of a drive shaft of said vehicle. The sensor may for example be a position sensor for determining the angular position of a shaft, for example a crankshaft or a camshaft, or a speed sensor for determining the rotational speed of a shaft, notably a crankshaft or a camshaft. Since the measurement and application functions of this type of sensor are known per se and do not form the subject-matter of an aspect of the invention, they will not be detailed further here. In particular, it will be noted that an aspect of the invention could be applied to any type of sensor for measuring magnetic-field variations, comprising a measurement cell comprising an integrated circuit and a magnetic element that needs to be positioned in line with said integrated circuit, notably such as a Hall-effect measurement cell.

[0055] Sensor 1

[0056] FIG. 1 depicts one embodiment of the sensor 1 according to an aspect of the invention. The sensor 1 comprises an external overmolding 1-1 and an electronic module 1-2 (FIG. 2).

[0057] External Overmolding 1-1

[0058] The external overmolding 1-1 is a one-piece element made of a thermoplastic material, such as, for example, made of polyphenylene sulfide, or PPS. The external overmolding 1-1 comprises a fixing plate 1-11 for fixing the sensor 1 in the vehicle (not depicted), for example on a rod, via an orifice 1-12. The external overmolding 1-1 also comprises a connection member 1-13 for connection to a connector of the vehicle so as to connect the sensor 1 to a computer of the vehicle, for example via a communication network of CAN bus type, or some other network known to those skilled in the art. The external overmolding 1-1 finally comprises a housing 1-14 in which the electronic module 1-2 is mounted.

[0059] Electronic Module 1-2

[0060] With reference to FIG. 2, the electronic module 1-2 comprises a leadframe 10 and an overmolding which is referred to as “internal” overmolding 20 comprising an integrated circuit 210 (FIGS. 5 and 11) and a magnetic element 220 (FIGS. 6 and 12). Advantageously, the electronic module 1-2 further comprises, in this preferred embodiment, although nonlimitingly, a positioning member 30 and a passive entity 40.

[0061] Leadframe 10

[0062] With reference to FIGS. 2 and 3, the connection grating 10, known in the art as a “leadframe” takes the form of an electrically conducting metal component comprising branches 10-1 defining electrical tracks so that the integrated circuit 210 can be electrically connected to a computer of the vehicle via a communication network of said vehicle. In other words, the leadframe 10 is an electrical connection element for connecting the sensor 1 to a connection cable connected to the computer of the vehicle.

[0063] With reference to FIGS. 3 and 4, the leadframe 10 comprises several distinct zones: a support zone 10A, a middle zone 10B, a zone referred to as a “passive” zone 10C and a connection zone 10D.

[0064] The support zone 10A is intended to receive the internal overmolding 20. The support zone 10A comprises an indentation defining a housing 10-2 designed to receive the integrated circuit 210 so that the magnetic element 220 can be placed against the support zone 10A, at the planar zone peripheral to the housing 10-2 without being in contact with the integrated circuit 210. In other words, the support zone 10A is designed to receive the magnetic element 220 in line with the integrated circuit while maintaining a space between said magnetic element 220 and said integrated circuit 210. This in particular allows the overmolding material to completely fill the hollow internal space of the magnetic element 220, as will be described hereinafter, thus avoiding vents in this zone.

[0065] The middle zone 10B is comprised between the support zone 10A and the passive zone 10C and is intended to receive the positioning member 30.

[0066] The passive zone 10C is comprised between the middle zone 10B and the passive connection zone 10D and is intended to receive the passive entity 40.

[0067] The connection zone 10D in this example comprises three connecting leads constituting free ends of the branches 10-1 so as to electrically connect the electronic module 1-2 to a computer of the vehicle.

[0068] In the embodiment described, the leadframe 10 comprises two lateral branches 10-11 (FIG. 3) designed to be received by clip-fastening, namely by fixing or insetting, in two slots 201 (FIG. 6) in the internal overmolding 20 so as to hold said internal overmolding 20 firmly on the leadframe 10.

[0069] Internal Overmolding 20

[0070] The internal overmolding 20 is produced at the support zone 10A so as to encapsulate said support zone 10A, the integrated circuit placed in the housing 10-2 and the magnetic element 220. With reference to FIG. 7, the internal overmolding 20 is preferably made of a polyepoxide material. The internal overmolding 20 notably comprises two slots 201 positioned one on each side and designed to receive the lateral branches 10-11 of the leadframe 10 when said leadframe 10 is being bent, as will be described hereinafter.

[0071] As a preference, still with reference to FIG. 7, the internal overmolding 20 comprises a rib 202 on its rear face and a lug 203 on its top face so as to hold the internal overmolding 20 fixedly in the mold during the external overmolding with the thermoplastic material, as will be described hereinafter.

[0072] Integrated Circuit 210

[0073] The integrated circuit 210 and the magnetic element 220 constitute the measurement cell of the sensor 1. As a preference, this measurement cell is a Hall-effect measurement cell, particularly in the case of a position or speed sensor 1.

[0074] The integrated circuit 210 takes the form of a flat plate of rectangular shape, overmolded with a polyepoxide material. This overmolding of the integrated circuit 210 is performed for example by the manufacturer of said integrated circuit 210, which may be different than the manufacturer of the sensor 1.

[0075] The integrated circuit 210 is electrically connected to the branches 10-1 of the leadframe 10, via connecting wires (not depicted), so as to allow the integrated circuit 210 to send to the computer the values of the measurements taken by said integrated circuit 210.

[0076] Magnetic Element 220

[0077] With reference to FIG. 6, the magnetic element 220 takes the form of a hollow cylindrical magnet of circular cross section. As indicated previously, the magnetic element 220 is designed to be placed against the support zone 10A in line with the integrated circuit 210 at a predetermined fixed distance from said integrated circuit 210 so as to form a space between the magnetic element 220 and the integrated circuit 210.

[0078] Positioning Member 30

[0079] The positioning member 30 is configured to conform to the internal overmolding 20 so as to hold same in a precise and fixed position during the steps of bending of the leadframe 10, as will be described hereinafter. The positioning member 30 is preferably obtained by overmolding the middle zone 10B with polyepoxide or with thermoplastic material.

[0080] The positioning member 30 comprises a receiving face (visible in FIG. 7) for receiving the internal overmolding 20 following the bending of the leadframe 10, as will be explained hereinafter. As a preference, the surface of the internal overmolding 20 and the surface of the passive entity 40 (receiving face) which come into contact with one another during the bending complement one another so as to immobilize the internal overmolding 20 on the positioning member 30 with a view to the overmolding of the whole, as will be described hereinafter. This advantageously makes it possible to reduce the clearances and tolerances associated with the bending and thus to improve the quality of the measurements taken by the sensor 1.

[0081] As a preference, with reference to FIG. 8, the positioning member 30 comprises, on the face opposite the receiving face for receiving the internal overmolding 20, a pin 31 so as to hold the passive entity 40 fixedly in the mold during the external overmolding with the thermoplastic material, as will be described hereinafter.

[0082] Passive Entity 40

[0083] The passive entity 40 is obtained by overmolding, preferably with polyepoxide, at least one passive component placed on the passive zone 10C of the leadframe 10. This or these passive component(s) may for example be one or more resistors and/or one or more capacitors so as to limit the electromagnetic interference generated by the integrated circuit 210 and the magnetic element 220 when the sensor 1 is in operation.

[0084] Method of Manufacture

[0085] One embodiment of the method for manufacturing the sensor 1 according to an aspect of the invention will now be described with reference notably to FIG. 9 et seq.

[0086] First of all, in a step E1, with reference to FIG. 10, a perforated base plate 11 is manufactured from a conducting metal plate, for example made of copper, so as to form two leadframes 10 comprising the branches 10-1 for creating two sensors 1 according to an aspect of the invention.

[0087] These leadframes 10 are connected to a surround 12 that allows the base plate 11 to be held in place during the manufacture of the sensor 1, as will be described hereinafter. It goes without saying that the base plate 11 could also comprise more than two leadframes 10 so as to manufacture more than two sensors 1, or else a single leadframe 10 so as to manufacture just one sensor 1. In what follows, the manufacturing method will be described for the manufacture of a sensor 1 from a leadframe 10 formed in the base plate 11 illustrated in FIG. 10.

[0088] In a step E2, with reference to FIG. 11, the integrated circuit 210 is then placed in the housing 10-2 of the support zone 10A and said integrated circuit 210 is electrically connected to the branches 10-1 of the leadframe 10 using electrical connection wires in a step E3.

[0089] As illustrated in FIG. 12, the magnetic element 220 is next placed, preferably by bonding it using an adhesive material (of liquid adhesive or any other suitable material type) against the support zone 10A of the leadframe 10 in line with the integrated circuit 210 at a predetermined fixed distance from said integrated circuit in a step E4 so as to form a space between the magnetic element 220 and the integrated circuit 210.

[0090] In a step E5, a set of passive electronic components, referred to as a “passive” assembly, comprising at least one passive electronic component, for example a resistor or a capacitor, is next placed on the passive zone 10C of each leadframe 10.

[0091] An overmolding step E6, preferably using a polyepoxide material, follows next, preferably in a single step, so as to form three distinct overmolded assemblies connected by the branches 10-1 of the leadframe 10 (FIG. 13):

[0092] the internal overmolding 20 comprising the support zone 10A, the integrated circuit 210 and the magnetic element 220 of each sensor 1 being manufactured,

[0093] the middle zone 10B, so as to form the positioning member 30 of each leadframe 10, and

[0094] the passive assembly, so as to form the passive entity 40 of each leadframe 10.

[0095] In a step E7, those portions of the base plate 11 that secure the surround 12 to the support zone 10A and to the middle zone 10B are cut and then, in a step E8, each leadframe 10 is bent by folding the internal overmolding 20 over against the positioning member 30, these features having complementary shapes so as to press them firmly against one another. At the end of the bending, the slots 201 of the internal overmolding 20 become fixed to the lateral branches 10-11 of each leadframe 10, and the internal overmolding 20 comes to bear against the passive entity 40 (FIG. 14).

[0096] Those portions of the base plate 11 which secure the surround 12 to the passive zone 10C and to the connecting zone 10D are then cut in a step E9, so as to obtain the electronic module 1-2.

[0097] Finally, in a step E10, the electronic module 1-2 is overmolded with a thermoplastic material in order to obtain the sensor 1.