DE102014213588A1 - Custom sensor manufactured by Triple Molden - Google Patents

Abstract

The invention relates to a method for producing a sensor (10, 28) having a sensor circuit (35, 40) carried on a placement island (48) of a circuit carrier (44) for outputting a sensor signal (42) dependent on a physical encoder field (33) with an interface (76) for transmitting the sensor signal (42) to a higher-order signal processing device (18), comprising: - a part of the circuit carrier (44) containing the mounting island (48) and the sensor circuit (35, 40) in a first protective ground (72), in which a positive locking element (74) is formed, - enveloping at least one of the positive locking element (74) containing part of the first protective mass (72) and the interface (76) in a second protective mass (84).

Description

The invention relates to a method for producing a sensor circuit and the sensor circuit.

From the WO 2010/037 810 A1 a sensor with a sensor circuit is known, which is connected in the manufacture of the sensor on a base element called wiring carrier. In the manufacture of the sensor circuit, the wiring carrier is held in a band called holding frame and forms integrally with this a so-called leadframe.

It is an object of the invention to improve the method for testing sensors.

The object is solved by the features of the independent claims. Preferred developments are the subject of the dependent claims.

According to one aspect of the invention, a method for producing a sensor having a sensor circuit carried on a mounting pad of a circuit carrier for outputting a sensor signal dependent on a physical encoder field and having an interface for transmitting the sensor signal to a higher-level signal processing device comprises the steps of enveloping the mounting pad and the sensor circuit contained part of the circuit substrate in a first protective ground, in which a positive-locking element is formed, and wrapping at least one of the positive-locking element containing part of the first protective ground and the interface in a second protective ground.

The specified method is based on the consideration that the sensor circuit must be wrapped in a protective compound for its protection in order to protect the sensor from damage due to mechanical stresses and other influences, such as weathering. However, the protective compound must be adapted to the space in which the sensor is to be used. However, since the sensor could be damaged without the protective compound, it must be immediately prepared with the protective compound and can not simply be stored unprotected until it is covered with the protective compound. For this reason, customer-specific manufacturing of sensors in small quantities is always very expensive because they always have their own production facility to be provided.

Here, the specified method starts with the knowledge that sensors such as rotational speed sensors and inertial sensors, which measure their physical measured variable contactlessly via a physical encoder field, actually hang in the air in the area of the sensor circuit and are less dependent on the installation space at this point. The actual dependence on space is more on the side of the sensor, where the sensor is connected to its environment in which it is to be used, in a vehicle such as the vehicle chassis.

Therefore, it is proposed in the context of the specified method to divide the aforementioned protective composition into two protective compounds and to initially encase the sensor with the first protective compound in the region of the sensor circuit. In this way, the sensor circuit and the assembly island would be protected and could be stored, transported and further processed in any way. The second protective compound, which could in principle also be the same material as the first protective compound, could then be formed completely independently of time and location to the first protective compound, whereby the sensor could be mass-produced for the most part and only for a small part of the sensor a correspondingly specific production tool must be provided. In order to ensure that the two protective compounds do not detach from one another, it is proposed in the context of the specified method to connect the two protective compounds to one another in a form-fitting manner.

Therefore, by using the specified method, the manufacturing costs for a sensor can be noticeably reduced.

In a development, the stated method comprises the step of forming a part of the second protective mass as a connection element, which is suitable for being mechanically connected to a holder for holding the sensor. In the aforementioned manner, this connection element can be formed customer-specifically in terms of time and location completely independently of the remaining part of the sensor, so that its production does not have to be integrated directly into the remaining production process of the sensor.

In another development of the specified method, the circuit carrier is held during wrapping in the first protective compound at a position at which the positive-locking element is formed. In this way, the circuit carrier is mechanically stabilized during wrapping with the first protective ground, so that the first protective ground can be manufactured with high precision around the circuit carrier. The form-fitting element itself thereby fulfills not only the purpose of the two protective compounds together but it also allows to support the molding process of the first protection mass.

In yet another development, the specified method comprises the step of enveloping the placement island and the sensor circuit in a mechanical decoupling compound before the sensor circuit carried on the sensor circuit is enveloped in the first protective compound. The mechanical decoupling mass keeps the sensor circuit and in particular a sensor present in the sensor circuit free from mechanical stresses that could distort the dependent of the physical encoder field sensor signal and thus the measurement of the above-mentioned physical quantity.

In an additional development of the specified method, the placement island is held by a web on a support element when enveloping in the mechanical decoupling compound, wherein the web is at least partially removed before enveloping the placement island and the sensor circuit in the first protective compound. This process can be described as partial free punching, in the context of which the sensor circuit with the first protective compound can be completely enveloped so that no marginal gaps or other unnecessary openings remain, through which moisture or other weathering-supporting substances could penetrate to the sensor circuit. On the other hand, due to the further connection to the support element with other sensors, the sensor can be held together thereon and transported in a particularly efficient manner and further processed. The final separation of the sensor can then finally take place after wrapping in the second protective compound.

In a particularly favorable manner, the interface can be selected as a location different from the placement island, because the interface must be kept free in any case until it is connected to a data cable for transmitting the sensor signal.

Conveniently, in a further development, the specified method may include the step of forming an alignment element on the first protection ground, on which the first protection ground can be aligned in a predetermined direction for enveloping the second protection ground. This alignment element ensures that the sensor can continue to be produced with high precision with small tolerances after being enveloped in the first protective compound and, if appropriate, subsequently transported to another production facility when it is being wrapped with the second protective compound.

In a particularly favorable development of the specified method, a sealing element is arranged between the first protective compound and the second protective compound, which avoids the penetration of moisture in a gap between the first protective compound and the second protective compound, which could possibly arise due to the positive connection.

According to another aspect of the invention, a sensor is manufactured by one of the specified methods.

The indicated sensor may be a wheel speed sensor or an inertial sensor for a vehicle.

In accordance with another aspect of the invention, a vehicle includes a specified sensor.

The above-described characteristics, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which will be described in connection with the drawings, wherein:

1 a schematic view of a vehicle with a vehicle dynamics control,

2 a schematic representation of a speed sensor in the vehicle of 1 .

3 a schematic representation of a read head of the speed sensor of 2 in an intermediate production state,

4 a sectional view of an alternative read head of the speed sensor of 2 in a plan view, and

5 a sectional view of the read head of 5 show in a side view.

In the figures, the same technical elements are provided with the same reference numerals and described only once.

It will open 1 Reference is made to a schematic view of a vehicle 2 with a known vehicle dynamics control shows. Details of this driving dynamics control, for example, the DE 10 2011 080 789 A1 be removed.

The vehicle 2 includes a chassis 4 and four wheels 6 , Every bike 6 Can be fixed on the chassis 4 fixed brake 8th opposite the chassis 4 be slowed down to a movement of the vehicle 2 to slow down on a road, not shown.

It may happen in a manner known to those skilled in the art that the wheels 6 of the vehicle 2 lose their grip and get the vehicle 2 even moved away from a given example by a steering wheel not shown steering trajectory by understeer or oversteer. This is avoided by known control circuits such as ABS (antilock braking system) and ESP (electronic stability program).

In the present embodiment, the vehicle 2 for speed sensors 10 at the wheels 6 on that a turn number 12 the wheels 6 to capture. Further, the vehicle points 2 an inertial sensor 14 on, the driving dynamics data 16 of the vehicle 2 from which, for example, a pitch rate, a roll rate, a yaw rate, a lateral acceleration, a longitudinal acceleration and / or a vertical acceleration can be output in a manner known to a person skilled in the art.

Based on the recorded speeds 12 and vehicle dynamics data 16 can be a regulator 18 in a manner known to those skilled determine whether the vehicle 2 slips on the road or even deviates from the above-mentioned predetermined trajectory and correspond with a known controller output signal 20 to react to that. The regulator output signal 20 can then be from a control device 22 to be used by means of actuating signals 24 Actuators, like the brakes 8th to drive, which respond to the slippage and the deviation from the given trajectory in a conventional manner.

The regulator 18 For example, in a known motor control of the vehicle 2 be integrated. Also, the controller can 18 and the actuator 22 formed as a common control device and optionally be integrated in the aforementioned engine control.

Based on the in 1 shown wheel speed sensor 10 the present invention is to be illustrated in more detail, even if the present invention can be implemented on any sensors, such as magnetic field sensors, acceleration sensors, rotation rate sensors, structure-borne sound sensors or temperature sensors.

It will open 2 Reference is made, which is a schematic view of one of the speed sensors 10 in the vehicle dynamics control of 1 shows.

The speed sensor 10 is in the present embodiment designed as an active speed sensor, which rotatably on the wheel 6 fixed donor element in the form of an encoder disc 26 and one fixed to the chassis 4 fixed sensor circuit, the below for the sake of simplicity read head 28 is called.

The encoder disk 26 consists in the present embodiment of juxtaposed magnetic north poles 30 and magnetic south poles 32 , which together form a physical field in the form of a transmitter magnetic field 33 excite. This transmitter magnetic field is in 3 for the sake of clarity with two dashed line lines indicated. Turns on the wheel 6 attached encoder disk 26 with this in one direction 34 , the encoder magnetic field rotates with it.

The reading head 28 In the present embodiment, a sensor, also called sensor, in the form of a magnetorstrictive element 35 , The magnetorstrictive element 35 changes depending on the angular position of the encoder wheel 26 Encoder magnetic field excited its electrical resistance. For detecting the speed 12 gets to the magnetoresisitv element 35 a probe signal 39 created, depending on the angular position of the encoder wheel 26 and thus of the electrical resistance magnetoresisitv element 35 is changed. Based on this change in the probe signal 39 evaluates a signal evaluation circuit 40 the speed 12 and outputs them in a data signal 42 to the controller 18 out. This signal evaluation circuit 40 can also be part of the reading head 28 be.

For this purpose and for further background information on active wheel speed sensors, the relevant prior art, such as the DE 101 46 949 A1 directed.

It will open 3 Reference is made, which is a schematic representation of the read head 28 for the speed sensor 10 in a not yet finished state of manufacture shows.

The reading head 28 is production state of the present embodiment in a so-called lead frame 44 executed circuit carrier held. From this leadframe 44 is in 3 only a part shown. The leadframe 44 can particularly preferably be designed as an endless belt, to which the in 3 Part shown of the leadframe 44 adjoining each other and / or one above the other. An example of this is in 4 shown.

The in 3 shown part of the leadframe 44 includes a support frame 46 , a wiring carrier in the form of a Bestückinsel 48 on which the reading head 28 held and interconnected, two tiebars 50 called webs and two contact terminals 52 , In doing so, the Tiebars hold 50 the contact connections 52 directly and the placement island 48 on the frame 46 , In the leadframe 44 are the holding frame 46 , the placement island 48 , the Tiebars 50 and the contact connections 52 formed as a one-piece stamped part or punching frame, in which the aforementioned elements are formed by punching from an electrically conductive sheet metal.

On the placement island 48 is in the context of the present embodiment, the sensor in the form of magnetoresisitven element 35 and the signal evaluation circuit 40 applied and contacted electrically, for example by soldering or gluing. The magnetoresistive element 35 and the signal evaluation circuit 40 are also via a bonding wire 54 connected to each other so that about the placement island 48 and the bonding wire 54 between the magnetoresistive element 35 and the signal evaluation circuit 40 the probe signal 39 can be transferred.

The placement island 48 is in the present embodiment directly with one of the two contact terminals 52 connected while the other of the two contact terminals 52 from the assembly island 48 galvanically isolated and with the signal evaluation circuit 40 over another bonding wire 54 connected is. In this way, via the two contact terminals 56 the data signal 42 from the signal evaluation circuit 40 be issued.

The support frame 46 has in the context of the present embodiment, two parallel transport stiffeners 58 on that over connecting bridges 60 connected to each other. On the transport strip 58 are transport holes 62 formed, in which engage a not further illustrated transport tool and the leadframe 44 can move. Further, on the transport strip 58 an index hole 64 formed, by means of which the position of the leadframe 44 determined during transport and can thus be regulated.

After the intermediate state of the read head according to the 3 is reached, the reading head becomes 28 enclosed.

The Einhausen should be based on the 4 and 5 be explained, the one to 3 alternative speed sensor 10 show, but in the same way as the principle in 2 explained.

In the reading head 28 of the 4 and 5 are back on a Bestückinsel 48 a magnetoresistive element 35 and a signal evaluation circuit 40 connected. Accordingly, the magnetic-positive element 35 the probe signal 39 applied and data signal 42 generated. The circuit may include additional circuit components 66 , such as protection capacitors or other sensors can be expanded in any way. Corresponding further circuit components 66 can also be outside the placement island 48 be interconnected.

After for the reading head 28 of the 4 and 5 one of the 3 corresponding intermediate state of production is reached, the circuit on the Bestückinsel 48 and optionally outside the placement island 48 wired electrical circuit components in a mechanical decoupling material 68 be wrapped up. For an optimal hold of the mechanical decoupling material 68 at the lead frame 44 to guarantee are at the leadframe 44 so-called anchor holes 70 formed by the mechanical decoupling material 68 be penetrated and so a positive connection with the leadframe 44 received. For the mechanical decoupling material, a thermoset material such as an epoxy resin is preferably selected. In any case, the mechanical decoupling material should 68 Have properties that only a slight mechanical stress on the individual encased electrical components 35 . 40 . 66 exercise.

After that, the reading head becomes 28 from his frame 46 partially punched. This is the reading head 28 at the Tiebars 50 from the frame 46 cut out, leaving it only at the contact terminals 52 on the frame 46 is held.

In this state, the read head 28 now in a first protective compound 72 shrouded, taking on the mechanical decoupling material 68 previously possibly a shielding plate 73 to increase the electromagnetic compatibility, called EMC, can be placed. This is the leadframe 44 on the frame 46 as well as at a clamping point 74 held, taking to the nip 74 can attack a corresponding tool. In this way, not only the stability when wrapping in the first protective compound 72 ensured the leadframe 44 and thus the reading head 28 are also aligned with high precision, resulting in the speed sensor 10 with very low tolerances. The first protective compound can also be used a thermoset. Alternatively, special thermoplastics, such as LCP (liquid crystalline polymers) or PPS (polyphenylene sulfide) can be used. When selecting a material as the second protective composition, the focus should be on criteria such as a low coefficient of thermal expansion, good chemical resistance, high mechanical strength and / or high density.

The reading head 28 in the state thus prepared is hereinafter referred to as a pre-molded part. This can now be done in a particularly favorable manner be stored or transported for further processing, because the first protective mass 72 provides a sufficiently high tightness with which the components 35 . 40 . 66 the sensor circuit are optimally protected.

For further processing of the preform this can now from the holding frame 46 to be isolated. That means that now also the contact connections 52 from the support frame 46 for example, can be separated by punching out. The first protection mass 72 protruding portions of the contact terminals 52 can now be used as an interface 76 for connecting a data cable 78 used with the data signal 42 to the controller 18 can be transferred. Alternatively, the leadframe could 44 Of course, also be designed as a plug on which the data cable 78 force and / or positive connection is connected. Will the data cable 78 with the interface 76 connected, known connection techniques, such as welding, soldering, gluing, crimping, splicing, ultrasonic welding or combinations thereof may be used. Particularly preferred is a variant in which the data cable at a cable manufacturer already with a wire end ferrule 80 was provided and this now by means of resistance welding with the leadframe 44 is welded. Conveniently, the contact terminals 52 while clamping elements 82 have, with which the wire end ferrules 80 can be added in addition frictionally.

Following this, the pre-molded part can now be placed in a second protective compound 84 at least partially shrouded. In order to support an optionally re-positioning of the pre-molded part, for example after singulation in a separate tool, can be on the leadframe 44 and / or on the first protective compound 72 suitable alignment elements 86 in the form of mechanical characteristics, such as recesses, webs, edges are formed. In this way, an exact alignment of the pre-molded part in the tool when wrapping with the second protective compound 84 and thus to ensure the above-mentioned low tolerance. In this case, the pre-molded part in the tool when wrapping with the second protective compound 84 be positioned floating with special support pins. Alternatively, the support pins can also be formed retractable. That is, after an initial wrapping of the preform with the second protective mass 84 (After a hardening of these) the support pins are withdrawn, possibly not from the second protection mass 84 to close recorded positions.

When wrapping the preform with the second protective compound 84 penetrates these also in the area of the terminal point 74 one at which the leadframe 44 when wrapping with the first protective compound 72 was held. In this way, a positive connection between the two protective compounds 72 . 84 so that the nip 74 how a form-fitting element acts. anchor holes 70 in the lead frame 44 can stop the second protective compound 72 continue to improve on the pre-molded part.

In a particularly favorable manner, only in this step, when wrapping in the second protective compound 84 a connection element 86 with the second protective compound 84 shaped with which the reading head 28 on the chassis 4 of the vehicle 2 can be attached as a holder. The connection element 86 includes a retaining flange 88 that is attached to the chassis 4 can be created and a mounting hole 90 about which the reading head 28 can be screwed for example by means of a screw on the chassis. In order to increase the mechanical strength of this connection, a sleeve can be inserted into the mounting hole 92 be used.

As material for the second protective compound 84 For example, an elastic thermoplastic can be selected.

To improve the adhesion of the decoupling compound 68 , the first protective compound 72 and the second protection mass 84 to each other and to the leadframe 44 The unit may be subjected to surface cleaning and activation just prior to the particular wrapping operation. For this, but not exclusively, OpenAir or vacuum plasmas can be used. Particularly advantageous is a hydrogen plasma pre-purification, followed by a nitrogen-argon-plasma activation.

Because the reading heads 28 after wrapping in the first protective compound 72 still partially on the support frame 46 via the contact connections 52 These can be kept in a particularly efficient manner before wrapping with the second protective compound 84 programmed together and adjusted if necessary. Alternatively, this would of course be possible even after separation.

To the mechanical strength of the reading head 28 can improve the leadframe 44 for example, an angled area 94 include the leadframe 44 stiffened. This angled area 94 can be achieved by bending part of the leadframe into an L-contour or a U-shape in section.

To the tightness between the two protective compounds 72 . 84 can increase, at least one sealing element, for example in the form of a sealing ring 96 be arranged, which has a gap 98 between the two protective measures 72 . 84 seals. This sealing ring 96 damps In addition, in a particularly favorable manner, even vibrations.

A sensor produced in the context of the method described above can be produced independently of its sensor-specific differences, such as measuring principle, sensing direction, wiring, in any desired manner through the design of the leadframe and different components. As electronic components can standard ICs with the leadframe 44 even after wrapping with the mechanical decoupling compound 68 get connected. For example, series-proven ICs can continue to be used.

As more electronic components 66 For example, a protective circuit can be installed. She can, as in 4 and 5 to be seen in the component subunit. The final preform can be finished identically in its outer dimensions, so that a central production of the pre-press is possible, which then worldwide to the various works for custom wrapping with the second protective compound 84 can be distributed.

The proposed method is characterized by the fact that the entire process chain for the production of a sensor has low tolerances and that a high tightness between leadframe 44 and the protective masses 72 . 84 is given (the essential seal is made by the first protective compound 72 ). In addition, the thermal expansion coefficient with respect to the decoupling and protective mass 68 . 72 to the material of the leadframe 44 be dimensioned so that only slight length expansion differences occur during temperature changes. A significantly longer service life is to be expected.

On the investment side, the advantage of this concept is that no additional handling is required. Only another tool for wrapping in the second protective compound 84 could be necessary. In a tool for wrapping with the second protective compound 84 Equipment with retractable fixing pins may be required.

If the sensor is designed in Carrier Design, an additional leadframe, a carrier molding machine, and an IC-in-Carrier mounting station are required.

By producing a pre-molded part identical to the outer contour (without the use of a carrier), cost savings can be expected in drawing set production, qualification, mold flow simulation, process optimization, logistics, tool manufacturing and BOM.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2010/037810 A1 [0002]
• DE 102011080789 A1 [0027]
• DE 10146949 A1 [0038]

Claims (10)

Method for producing a sensor ( 10 . 28 ) with one on a Bestückinsel ( 48 ) of a circuit carrier ( 44 ) carried sensor circuit ( 35 . 40 ) for outputting one of a physical encoder field ( 33 ) dependent sensor signal ( 42 ) and with an interface ( 76 ) for sending the sensor signal ( 42 ) to a higher-level signal processing device ( 18 ), comprising: enveloping a placement island ( 48 ) and the sensor circuit ( 35 . 40 ) contained part of the circuit carrier ( 44 ) in a first protective composition ( 72 ), in which a form-locking element ( 74 ), wrapping at least one of the interlocking elements ( 74 ) containing part of the first protective mass ( 72 ) and the interface ( 76 ) in a second protective composition ( 84 ). Method according to claim 1, comprising: forming a part of the second protective composition ( 84 ) as a connection element ( 86 ), which is suitable with a holder ( 6 ) for holding the sensor ( 10 . 28 ) to be mechanically connected. Method according to claim 1 or 2, wherein the circuit carrier ( 44 ) during wrapping in the first protective composition ( 72 ) is held at a position at which the positive-locking element ( 74 ) is formed. Method according to one of the preceding claims, comprising: - wrapping the placement island ( 48 ) and the sensor circuit ( 35 . 40 ) in a mechanical decoupling mass ( 68 ), before the on the application island ( 48 ) worn sensor circuit ( 35 . 40 ) in the first protective compound ( 72 ) is wrapped. The method of claim 4, wherein the placement island ( 48 ) when enveloping in the mechanical decoupling mass ( 68 ) over a bridge ( 50 ) on a support element ( 46 ) and the bridge ( 50 ) before wrapping the placement island ( 48 ) and the sensor circuit ( 35 . 40 ) in the first protective compound ( 72 ) is at least partially removed. Method according to claim 5, wherein the circuit carrier ( 44 ) on one of the assembly island ( 48 ) different place ( 76 ) during wrapping of the application island ( 48 ) and the sensor circuit ( 35 . 40 ) in the first protective compound ( 72 ) with the support element ( 46 ) remains connected. The method of claim 6, wherein the of the Bestückinsel ( 48 ) different place the interface ( 76 ). Method according to one of the preceding claims, comprising: - forming an alignment element ( 86 ) on the first protective compound ( 72 ) and / or on the circuit carrier ( 44 ) at which the sensor ( 10 . 28 ) for wrapping with the second protective compound ( 84 ) can be aligned in a predetermined direction. Method according to one of the preceding claims, comprising: arranging a sealing element ( 96 ) between the first protection mass ( 72 ) and the second protective compound ( 84 ). Sensor ( 10 . 28 ) produced by a method according to any one of the preceding claims.

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