Methods for manufacturing sensors for motor vehicles

Abstract

A method for manufacturing a sensor for a motor vehicle includes placing a sensor core (E5) in a recess in a mold, the sensor core comprising: a metal lead frame including a plurality of connection pins and two lateral retaining members; and an integrated circuit including at least one measuring unit and overmolded on a support region of the metal lead frame, such that the lateral retaining members and connection pins are exposed; and placing conductive terminals on each connection pin, arranging magnets in a row with the overmolded integrated circuit (E6), placing the two lateral recesses of the mold (E7) on either side of the magnets and the integrated circuit, such that the lateral recesses hold the lead frame near the lateral retaining members by ensuring translational locking in both longitudinal and lateral directions of the lead frame, while forming a space around the integrated circuit and the magnet for overmolding material, overmolding (E11) portions of the integrated circuit, the magnet, and the lead frame to allow free ends of the terminals to protrude, and removing (E12) the mold.

Description

Technical Field

[0001] This invention relates to the field of sensors for motor vehicles, and more specifically to a sensor and a method for manufacturing such a sensor. In particular, an object of this invention is to improve the accuracy of existing sensors. Background Technology

[0002] In a known manner, motor vehicles include multiple measuring sensors for measuring, for example, the rotational speed or angular position of drive shafts (such as crankshafts or camshafts).

[0003] In a known manner, these sensors operate in association with a target fixed to an axis for which parameters are measured. For example, the target may be in the form of a gear, whose teeth alter the electromagnetic field generated by a magnet mounted in the sensor. The change in magnetic field is detected by the sensor's sensitive element (called the measurement unit).

[0004] According to known manufacturing methods, the sensor is manufactured in several steps. First, an integrated circuit is overmolded onto a metal lead frame, which includes pins with epoxy resin. Then, the assembly is placed in a mold, and a magnet is positioned on the integrated circuit. The assembly is overmolded, allowing only the pins to protrude. A final overmolding is performed to seal the sensor, simultaneously forming the electrical connection socket and sensor attachment components.

[0005] In existing methods, the second overmolding causes the magnet to be positioned relative to the overmolding of the integrated circuit, and therefore relative to the measurement unit. This positioning differs from one sensor to another, implying variations in the dimensional chain over a fairly high tolerance range. Consequently, the signals generated by measurement units with the same target arrangement for a given measurement configuration differ between one sensor and another, which can lead to inaccurate measurements, in particular.

[0006] Therefore, a solution is needed that at least partially overcomes these shortcomings. Summary of the Invention

[0007] Therefore, the initial objective of the present invention is a method for manufacturing a sensor for motor vehicles, the method comprising the following steps:

[0008] - The sensor core is placed in the recess of the mold, the sensor core comprising: a metal lead frame including a plurality of connection pins and two lateral retaining members; and an integrated circuit including at least one measuring unit and overmolded on a support area of ​​the metal lead frame such that the lateral retaining members and the connection pins are exposed;

[0009] - Place conductive terminals on each connection pin;

[0010] - Place the magnets and the encapsulated integrated circuits in a row;

[0011] - Two transverse mold recesses are placed on either side of the magnet and the integrated circuit, such that the transverse recesses hold the lead frame near the transverse retaining member by ensuring translational locking in both the longitudinal and transverse directions of the lead frame, while forming a space around the integrated circuit and the magnet for covering molding material.

[0012] - Overmolding a portion of the integrated circuit, magnet, and lead frame to allow the free ends of the terminals to protrude;

[0013] - Remove the mold.

[0014] By retaining both the lateral retaining member and the magnet, the lateral notch allows the magnet to lock relative to the integrated circuit during overmolding, and therefore relative to the measurement unit. While very small gaps may exist between the mold notch and the magnet, the lateral notch specifically allows for the elimination of gaps between the lead frame and the mold in both the longitudinal and lateral directions, eliminating tolerances compared to previous solutions. Therefore, for a given measurement configuration, the signals generated by the measurement unit are very close, even identical, from one sensor to another, resulting in high measurement accuracy.

[0015] According to one aspect of the invention, the free end of each lateral retaining member includes at least one stop, preferably having two rounded corners, and a lateral notch, each lateral notch including two support protrusions. The placement of the two lateral molded notches involves contacting at least one stop of the lateral retaining member with the protrusion of the corresponding lateral notch. This generates effective translational locking of both the longitudinal and lateral aspects of the leadframe by contacting (or interfering with) the protrusion of the lateral notch with the lateral retaining member. Particularly near the two corners, the corners (or any other equivalent component with a small surface area) have the advantage that, due to their small surface area, they allow retention of the leadframe while allowing for almost complete overmolding of the integrated circuit and magnet.

[0016] According to another aspect of the invention, the magnet is placed in a recess in the mold such that the magnet abuts against the recess along the longitudinal axis of the mold. This placement allows the magnet to be pre-centered in the mold before positioning the transverse mold recess.

[0017] Advantageously, the method further includes the step of placing a pin that allows the magnet to be vertically translated and locked in the mold.

[0018] More advantageously, the method further includes the step of placing a pin that allows the magnet to be longitudinally translated and locked in the mold.

[0019] According to one aspect of the invention, the method further includes the steps of placing an integrated circuit on a metal lead frame and overmolding the integrated circuit and a portion of the lead frame to expose a lateral holding member and allow the ends of the connection pins to protrude, and then placing a magnet on the overmolded portion of the integrated circuit.

[0020] According to one aspect of the invention, the method includes the step of electrically connecting an integrated circuit to a connection pin.

[0021] According to one aspect of the invention, the method includes the step of final overmolding of an integrated circuit, a magnet, and a portion of a lead frame to form a connector socket around the end of a connection pin.

[0022] The present invention also relates to a mold for manufacturing a sensor using the above-described method, the sensor comprising a metal lead frame including a plurality of connecting pins and two lateral retaining members, each lateral retaining member including a free retaining end including at least one stop, preferably two corners, the mold including two lateral recesses, each lateral recess including an inner support surface having a preferably V-shaped cross-section, the inner support surface being designed to hold the lead frame near at least one stop at the free end of the lateral retaining member of the lead frame by ensuring longitudinal and lateral translational locking of the lead frame when the mold is closed onto the lead frame placed on the mold.

[0023] The present invention also relates to a motor vehicle that includes a sensor obtained using the method described above. Attached Figure Description

[0024] Other features and advantages of the invention will become more apparent from the following description. This description is purely illustrative and should be read with reference to the accompanying drawings, in which:

[0025] Figure 1 This is a perspective view of the lead frame according to an embodiment of the sensor of the present invention;

[0026] Figure 2 It is equipped with integrated circuit encapsulation molding, Figure 1 A three-dimensional view of the lead frame;

[0027] Figure 3 It is positioned on the recess of the mold. Figure 2 A 3D view of the components;

[0028] Figure 4 yes Figure 3 A 3D view of the components, in which the magnet has been positioned on the integrated circuit overlay.

[0029] Figure 5 yes Figure 4 A 3D view of the components, in which the left and right transverse recesses of the mold have been positioned;

[0030] Figure 6 This is a perspective view of the left transverse recess of the mold, with particular emphasis on the support protrusion of the retaining member used to hold the lead frame;

[0031] Figure 7 yes Figure 6 A 3D view of the components, in which the upper support of the mold has been positioned;

[0032] Figure 8 yes Figure 7 A 3D view of the components, in which the vertical pins and the tilted pins have been positioned;

[0033] Figure 9 yes Figure 8 A 3D view of the components, showing that the left and right clamps have been placed for locking the pins;

[0034] Figure 10 It is a three-dimensional view of the intermediate component obtained after molding in a mold;

[0035] Figure 11 This is a perspective view of an embodiment of the sensor obtained after final overmolding according to the present invention;

[0036] Figure 12 An embodiment of the method according to the present invention is illustrated schematically. Detailed Implementation

[0037] The sensor obtained using the method according to the invention is intended for installation in a motor vehicle. The sensor can be of any type. For example, the sensor can be a position or speed sensor for a drive shaft such as a crankshaft, camshaft, or any other suitable shaft.

[0038] Figures 1 to 11 Embodiments of the sensor 1 according to the invention are shown in different steps of the manufacturing method, and Figure 12 An embodiment of the method according to the present invention is shown.

[0039] First, such as Figure 1 As shown, in step E1, the metal lead frame 10 is mounted on the support (not shown for clarity).

[0040] The lead frame 10 is in the form of a metal component that includes a support region 11 from which a plurality of connection pins 12 extend along a longitudinal axis X for electrically connecting the measurement unit 15-1 of the integrated circuit 15 to an external computer (not shown) in a manner known per se. In this example, the lead frame 10 includes three connection pins 12.

[0041] The support area 11 of the lead frame 10 includes two lateral retaining members 13, which are integrally formed with the support area 11 and extend along the lateral axis Y perpendicular to the longitudinal axis X.

[0042] In step E2, an integrated circuit 15, including a measurement unit 15-1, is placed on the support region 11, and then in step E3, the integrated circuit is electrically connected to the connection pin 12, for example, by means of metal wires soldered between each connection pin 12 and the three connection terminals of the integrated circuit.

[0043] In step E4, the integrated circuit and support region 11 are then encapsulated with epoxy resin, except for the two lateral retaining members 13, which remain visible. Figure 2 The first overmolded component 20 protects the integrated circuit 15, and in particular the measuring unit 15-1.

[0044] In step E5, the assembly formed by the lead frame 10 and the first overmolded part 20 is placed in the mold 30 ( Figure 3 The metal terminal 12-1, forming an extension of the connecting pin 12, is positioned on the lower recess 31 of the sensor 1. This allows for subsequent electrical connection of the sensor 1 to the outside, as described below. The terminals 12-1 are not soldered at this stage to avoid damage during the overmolding process in step E11 described below.

[0045] In step E6 ( Figure 4 In this embodiment, the magnet 40 is positioned on the first overmolded part 20. In this example, the magnet 40 is parallelepiped in shape, but it should be noted that in another embodiment, the magnet 40 may be in a different shape, such as a cylinder.

[0046] Then, in step E7, the left lateral notch 32 and the right lateral notch 33 of the mold 30 are positioned on the lower notch 31 to hold the magnet in its left side, its right side and its rear ( Figure 5 The left lateral notch 32 and the right lateral notch 33 contact the lateral retaining member 13 to ensure that the lead frame 10 is locked in translation along the lateral axis Y and contacts the rear of the magnet 40 via the two mold stops 32C to ensure that the magnet is locked in translation backward along the longitudinal axis X.

[0047] More specifically, first refer to Figure 1 Each lateral retaining member 13 protrudes from the support region 11 along the lateral axis Y and includes a central portion 13A, which defines two stops at its free end in the form of two rounded corners 13-1. Each lateral retaining member 13 also includes two lugs 13-2.

[0048] refer to Figure 6 The left transverse recess 32 includes two prismatic protrusions 32A, each having a triangular cross-section formed vertically on the inner wall 32B of the left transverse recess 32. The right transverse recess 33 has the same symmetrical structure.

[0049] The placement of the two transverse mold recesses 32, 33 involves contacting the two protrusions 32A of each transverse mold recess 32, 33 with the two corners 13-1 of the corresponding transverse retaining member 13 and with the mold stop 32C to effectively hold and translate the lead frame 10 longitudinally and laterally by contacting (or interfering with) the two protrusions 32A of the transverse recesses 32, 33 with the transverse retaining member 13 near the two corners 13-1. The function of the inner wall 32B and the mold stop 32C is to correctly position (pre-center) the magnet 40 relative to the integrated circuit. For this purpose, the inner wall 32B and the mold stop 32C are formed on each transverse recess of the transverse recesses 32, 33 to achieve better relative positioning by eliminating the necessary functional gaps compared to the case where relative positioning is achieved by means of several movable parts in the mold 30.

[0050] Then, in step E8, the upper recess 34 of the mold 30 is placed above the lower recess 31, the left transverse recess 32, and the right transverse recess 33 to cover the magnet and close the mold 30. Figure 7 The upper notch 34 includes a first hole 34A and a second hole 34B.

[0051] Then, in step E9, the vertical pin 51 and the tilting pin 52 are inserted into the first hole 34A and the second hole 34B of the upper recess 34, respectively, so as to translate the locking magnet forward along the vertical axis Z and the longitudinal axis X, respectively. Figure 8 ).

[0052] Then, in step E10, the left clamp 54 and the right clamp 55 are mounted on the upper recess 34 of the mold 30 to hold the vertical pin 51 and the tilted pin 52 for molding. Figure 9 ).

[0053] Then, in step E11, epoxy resin is used to encapsulate portions of the integrated circuit, magnet, and lead frame to allow the ends of the connection pins 12 to protrude. The encapsulated parts of the magnet 40 and integrated circuit are then fixed within the intermediate encapsulated part 61. Figure 10 As shown in the diagram, in order to precisely lock them relative to each other, thereby achieving high measurement efficiency of sensor 1. The corners 13-1 are still visible because they are covered by the two protrusions 32A of the notches 32, 33 of mold 30.

[0054] Then, in step E12, mold 30 is removed to obtain intermediate element 60. Figure 10Then terminal 12-1 can be soldered to connection pin 12 to complete the electrical connection and allow sensor 1 to transmit the signal it measures to the vehicle's electronic control unit.

[0055] In step E13 ( Figure 11 In the process, the final overmolded part 70 of the intermediate element 60 is performed in another mold (not shown) to form the sensor 1, and in particular the connector socket 71 around the terminal 12-1 to electrically connect the sensor 1 to the vehicle, and to form the fixing member 72, for example in the form of a ring, to mount the sensor 1 in the vehicle.

Claims

1. A method for manufacturing a sensor (1) for a motor vehicle, the method comprising the steps of: - The sensor core is placed (E5) in the recess (31) of the mold (30), the sensor core comprising: a metal lead frame (10) including a plurality of connection pins (12) and two lateral retaining members (13); and an integrated circuit (15) including at least one measuring unit (15-1) and being overmolded in the first overmolding on the support area (11) of the metal lead frame (10) such that the lateral retaining members (13) and the connection pins (12) are exposed; and conductive terminals (12-1) are placed on each connection pin; - The magnet (40) is placed in a row with the integrated circuit (15) which is overmolded on the first overmolding in the previous step (E6), wherein the magnet (40) is above the integrated circuit (15); - One of the two transverse recesses (32, 33) of the mold (30) is placed (E7) on one side of the magnet (40) and the integrated circuit (15), and the other transverse recess is placed (E7) on the other side of the magnet (40) and the integrated circuit (15), such that by ensuring translational locking of the lead frame (10) in both longitudinal and transverse directions, the transverse recesses (32, 33) hold the lead frame (10) near the transverse retaining member (13), while forming a space around the integrated circuit (15) and the magnet (40) for covering the molding material; - The overmolded integrated circuit (15), the magnet (40) and part of the lead frame (10) are overmolded (E11), the magnet (40) and the overmolded integrated circuit (15) are then fixed in an intermediate overmolded part (61) so as to precisely lock them relative to each other for the measurement efficiency of the sensor (1) and allow the free end of the terminal (12-1) to protrude; - Remove (E12) the mold (30).

2. The method according to claim 1, wherein, Each lateral retaining member (13) has at least one stop (13-1) at its free end, and each of the lateral recesses (32, 33) includes two support protrusions (32A). The placement of the two lateral recesses (32, 33) includes bringing at least one stop (13-1) of the lateral retaining member (13) into contact with the protrusion (32A) of the corresponding lateral recess (32, 33).

3. The method according to claim 1 or 2, wherein, The magnet (40) is placed in the recess (31) such that the magnet (40) abuts against each transverse recess (32, 33) along the longitudinal axis near the mold stop (32C).

4. The method according to claim 1 or 2, further comprising the step of placing a pin (51) that allows the magnet (40) to be vertically and translatably locked in the mold (30).

5. The method according to claim 1 or 2, further comprising the step of placing a pin (52) that allows the magnet (40) to be longitudinally translated and locked in the mold (30).

6. The method according to claim 1 or 2, further comprising the steps of placing the integrated circuit (15) on the metal lead frame (10), electrically connecting the integrated circuit (15) to the connection pin (12), and overmolding the integrated circuit (15) and a portion of the lead frame (10) to expose the lateral retaining member (13) and allow the end of the connection pin (12) to protrude, and then placing the magnet (40) on the overmolded portion of the integrated circuit (15).

7. The method according to claim 1 or 2, the method comprising the step (70) of final overmolding the intermediate overmolding (61) of the integrated circuit (15), the magnet (40) and a portion of the lead frame (10) to form a connector socket (71) around the end of the terminal (12-1).

8. A mold (30) for manufacturing a sensor (1) using the method of any one of claims 1 to 7, the sensor (1) comprising a metal lead frame (10) including a plurality of connection pins (12) and two lateral retaining members (13), each lateral retaining member (13) including a free retaining end in the form of a protruding rectangular portion including two corners, the mold (30) including two lateral notches (32, 33), each lateral notch (32, 33) including an inner surface designed to retain the lead frame (10) near the free end of the lateral retaining member (13) of the lead frame (10) by ensuring that the longitudinal and lateral translation of the lead frame (10) is locked when the mold (30) is closed onto the lead frame (10).

9. The mold (30) according to claim 8, wherein, Each lateral notch (32, 33) includes at least one stop element (32C) for each lateral retaining member (13).

10. A motor vehicle comprising a sensor (1) obtained using the method of any one of claims 1 to 7.

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