DE102007057904A1 - Sensor module and method for producing the sensor module - Google Patents

Abstract

A sensor module (1) has a sensor chip (2), which is applied to a conductor grid (4). A plastic sleeve (11) of the sensor module (1) extends only over an edge region of the sensor chip (2). As a result, the mechanical stress of the sensor chip (2) by the plastic sheath (11) is kept small.

Description

The The invention relates to a sensor module with a sensor chip, which covered by a plastic cover.

The The invention further relates to a method for producing the sensor module.

Such a sensor module is from the US 2007/0139044 A1 known. The known sensor module comprises a conductor grid on which a sensor chip is applied. The sensor chip is covered with an inner plastic sheath made of a thermosetting plastic. Further, an outer plastic sheath made of a thermoplastic material is provided which forms a plug in the region of contact ends of the conductor grid. The known sensor module is set up in particular for detecting the rotational speed of a turbocharger.

Furthermore, from the US 2004/0118227 A1 Another sensor module is known in which a sensor chip is applied to one end of a conductor grid and provided by means of thermoplastic material with a plastic sheath. The other end of the conductor grid is connected to contact pins. The joint and the pins themselves are embedded in another plastic shell. In the area facing away from the conductor grid ends of the contact pins, the further plastic shell is designed as a plug socket. In particular, a temperature-sensitive sensor, a sensor sensitive to magnetic fields, an acceleration sensor or an angular-velocity sensor are provided as the sensor chip.

One Disadvantage of the known sensor modules is that the sensor chip of the environment is shielded. This may result in prolonged Response times or the need to influence through a calibration to determine the plastic shell and to consider accordingly. Furthermore can change the nature of the Plastic cover for long-term signal changes which can cause incorrect measurements.

outgoing From this prior art, the invention is based on the object to create a sensor module with improved measuring properties. The invention is also based on the object, a method for Specify the production of the sensor module.

These Tasks are performed by a sensor module and a procedure using the Characteristics of the independent claims solved. In dependent claims are advantageous Embodiments and developments specified.

at In the sensor modules, the sensor cover leaves a sensor surface and at least partially a lateral edge region of the Sensor chips free. This is the sensor surface of the sensor chip exposed directly to the surrounding medium. temperature changes can be extended in the case of a temperature sensor without Record response times. Pressure changes or concentration of the surrounding medium are further through the plastic cover not distorted. Nevertheless, an electrical contact of the sensor chip from an immediate mechanical impact by the plastic cover will be protected. The sensor module therefore offers the advantages of an exposed sensor surface along with the benefits of reinforcing the sensor module Plastic cover.

Preferably is the sensor module provided with a conductor carrier, on which the sensor chip is attached. In this case extends the plastic cover over the contact area, in the the sensor chip with the conductor tracks of the conductor carrier connected is. This is the most sensitive contact area Protected against external influences.

at In one embodiment, the sensor chip is merely included a lateral edge region on the conductor carrier. As a result, the conductor carrier in the region of the sensor chip completely covered with the plastic cover so that the conductor carrier through the plastic cover Protected against corrosion and to the outside there are no interfaces at which it is for gap formation can come.

at In another embodiment, the conductor carrier protrudes out of the plastic shell in the area of the sensor chip. This allows the sensor chip to be supported on the entire underside become.

at Another embodiment of the sensor module is the Plastic cover inserted into a sensor socket in the sliding seat and joints between the plastic cover and the sensor socket sealed with the help of a filling compound.

Further Is it possible that the plastic cover is one in the Sensor fitting trained passage seals and the Holding sensor chip in the bushing. To this Way, the application of an additional filler, which connects the plastic cover with the sensor socket dispenses become.

The conductor carrier is preferably a conductor grid that is simple Way can be punched out of a metal sheet. In this context, a conductive grid is to be understood as meaning a self-supporting unit of conductor tracks, wherein the conductor tracks do not necessarily have to be connected to one another after completion of the production. The conductor grid may, for example, be a so-called lead frame. By using such a conductor grid, the Fes activity of the sensor module can be additionally increased. In addition, the production is facilitated, since a stable carrier is available.

Of the Sensor chip is preferably formed elongated. The sensor surface is arranged in an end region of the sensor chip, so that only the part of the sensor chip provided with the sensor surface protrudes from the plastic cover. In this case too the remaining areas of the sensor chip from the plastic cover protected.

Around protect the sensor chip from environmental influences the outside of the sensor chip can be surface-passivated be. This can be done in particular by a passivation layer a layer ceiling of a few microns to a few hundred microns, preferably be done below one millimeter. For the passivation layer come in particular materials on the Base of oxides, nitrides, carbides or polymers such as silicones, Parylene and polyimides, or precious metals in question.

The Production of the sensor module is preferably carried out using a Transfer molding process in which the sensor chip in a mold introduced and filled the mold with a plastic compound becomes. Before filling the molding material in the mold an inside of the mold is covered with a release film, the detachment of the cured plastic mass facilitated by the mold. As a result, the content of release agents be reduced in the plastic mass, resulting in a plastic mass leads with increased adhesive strength.

Further Features and advantages of the invention will become apparent from the following Description, in the embodiments of the invention based the accompanying drawings are explained. It demonstrate:

1 a longitudinal section through a sensor module, with a captured in an edge region of a plastic shell sensor chip;

2 a view of the sensor module 1 ;

3 a longitudinal section through another sensor module, with a captured in an edge region of a plastic shell sensor chip;

4 a view of the sensor module 3 ;

5 a view of a sensor chip;

6 a longitudinal section through a sensor module with the sensor chip 5 ;

7 a longitudinal section through the introduced into an external sensor socket sensor module 1 ;

8th a perspective view of a sensor module, wherein the sensor chip is held by a seal of a passage of a sensor socket and

9 a perspective view of another cut sensor module, wherein the sensor chip is held by the seal of a passage of a sensor socket.

1 shows a longitudinal section through a sensor module 1 that has a sensor chip 2 with a sensor surface 3 features. At the sensor chip 2 it is, for example, a pressure sensor whose pressure-sensitive membrane as a sensor surface 3 serves. The sensor chip 2 is on a ladder grid 4 applied and with the help of bonding wires 5 with the ladder grid 4 connected. On the ladder grid 4 Furthermore, there are also capacitors 6 and 7 , In a bond area 8th of the sensor module 1 are the bonding wires 5 from an inner plastic shell 9 envelops. Furthermore, it is a border area 10 of the sensor chip 2 as well as the inner plastic cover 9 and the capacitors 6 and 7 from an outer plastic shell 11 enveloped, extending to a contact end 12 of the ladder grid 4 extends. The sensor chip 2 thus protrudes at one end of the plastic shell 11 from the plastic case 11 out. On the outer plastic shell 11 are pimples 13 educated. To the contact ends 12 of the ladder grid 4 towards the outer plastic shell 11 also a rejuvenation 14 on.

2 shows a plan view of the sensor module 1 out 1 , Based 2 it becomes clear that the ladder grid 4 over three tracks 15 . 16 and 17 has, of which the middle trace 16 is intended for occupancy with mass. The conductor track 16 also points in the area of the sensor chip 1 a support surface 18 on top of which the sensor chip 2 can be applied. In this case, the outer plastic cover extends 11 over a rear edge surface 20 as well as partly over lateral edge surfaces 21 and 22 , A front edge surface 23 stays against from the plastic shell 11 unaffected. The plastic cover 11 Therefore, extends only over part of the lateral edge region of the sensor chip 2 and leaves another part of the lateral edge region of the sensor chip 2 free.

3 shows a longitudinal section through another sensor module 24 that has a ladder grid 25 has that in the area of the sensor chip 2 from the plastic case 11 protrudes.

Based 4 is apparent that the conductor grid 25 in the area of the sensor chip 2 over a holding section 26 has, with the middle trace 16 connected, which is intended for the assignment with mass. The holding section 26 also has a central recess 27 on, so the sensor chip 2 with its circumference on the ladder grid 25 rests. Through the recess 27 can an intake manifold of a suction device to the sensor chip 2 and the sensor chip 2 using the suction device on the ladder grid 25 be fixed before the bonding wires 5 for establishing a connection between the sensor chip 2 and the ladder grid 25 be applied.

In the sensor module 1 and the sensor module 24 is the sensor surface 3 each centered on the sensor chip 2 arranged. In 5 is another elongated sensor chip 28 shown in which the sensor surface 3 at a sensor end 29 of the sensor chip 28 located. In the longitudinal direction of the sensor chip 2 close to the sensor end 29 Sensor circuit regions 30 to 33 which is up to a contact area 34 at a contact end 35 of the sensor chip 2 extend.

The sensor chip 28 For example, as in 6 shown for a sensor module 36 be used, in which only the contact area 34 and an adjacent circuit area 33 from the plastic shell 11 be covered. Compared to those in the 1 to 4 represented sensor modules 1 and 24 is at the in 6 illustrated sensor module 36 the sensor surface 3 better against the plastic shell 11 caused voltages due to the sensor surface 3 by the large distance to the plastic cover 11 from the plastic shell 11 is mechanically decoupled. If also the circuit areas 31 and 32 with the plastic cover 11 be covered, resulting in longer creepage distances for the medium to be detected, since the medium to be detected along the interface between the sensor chip 28 and the plastic sheath must travel a long distance, until it reaches the bond wires 5 arrives.

Another advantage of in 6 shown sensor module 36 is that a coating that covers the sensor area 3 protects against external influences on the sensor surface 3 can be applied without the contacts in the contact area 34 must be protected by special measures.

In this respect, the production of the sensor chip 28 opposite the sensor chip 2 simplified.

The sensor modules 1 . 24 and 36 can also be in an outer sensor mount 37 be introduced, which in longitudinal section in 7 is shown. The sensor version 37 has in particular a recording 38 in, for example, in the 6 illustrated sensor module 1 in the sliding seat can be introduced. The rejuvenation takes effect 14 the plastic cover 11 in an execution 39 one, the one in the sensor socket 37 trained plug room 40 with a sensor room 41 combines. On the outside of the sensor socket 37 For example, a thread 42 be formed with the sensor 37 can be screwed into a holder. It also runs around a front opening 43 of the sensor space 41 a sealing ring 44 around, with the sensor socket 37 can be applied tightly against the wall of a container or a pipe.

It should be noted that the sensor opening 43 can also be formed in the radial direction.

The sensor modules 1 . 24 and 36 are made by placing on the punched ladder grid 4 and 25 the sensor chips 2 or 28 be applied. The sensor chips 2 or 28 For example, using an adhesive on the wire grids 4 and 25 be attached. Subsequently, an electrical connection between the sensor chips 2 or 28 and the wire grids 4 or 25 using the bonding wires 5 produced. Subsequently, the ladder grid 4 or 25 introduced into a mold and the inner plastic shell 9 that the bond area 8th covering, trained. In a further method step can then in another mold, the plastic sleeve 11 getting produced. The plastic sleeves 9 and 11 are preferably formed in a transfer molding process in which the molding compound is brought into a flowable state in an advance cylinder and then pressed into the molding tool. The shrinkage of the molding material in the mold preferably takes place with a pressure below 10 bar. In a Nachpressvorgang can then be pressed out of the mold in a pressure range between 50 and 100 bar residual air.

After the formation of the plastic shell 11 then can the sensor module 1 . 24 or 36 in a sensor socket of the type of sensor socket 37 be introduced and fixed there. For example, the space between the plastic shell 11 and the sensor socket 37 with the help of another Materials, preferably by means of a so-called underfillers filled by capillary forces in the space between the plastic shell 11 and the sensor version 37 is pulled.

For the molding process, the so-called seal film technology (= SFT) can be used. In this case, a highly flexible release film is sucked on the inside of the mold, which seals the mold and the sticking of the mold to the plastic shell 9 or 11 prevented. As a material for the release film, for example Teflon can be used. Such a release film is also used in the area in which the mold on the sensor chip 2 or 28 is present to compensate for tolerances and damage to the sensor chip 2 or 28 to prevent. In this respect, the release film acts as a cushion. In addition, the use of such a release film also allows in the manufacture of the plastic shell 9 or 11 Plastic mass used to reduce the proportion of release agents that the detachment process of the plastic shell 9 or 11 from the mold. These ingredients are waxy components of the plastic composition, the proportion of which can be kept less than 0.5 percent by weight in the present case. Such plastic compositions with a low proportion of release agents also adhere much better to the sensor chip 2 or 28 , so the risk of lifting the plastic cover of sensor chip 2 or 28 can be reduced.

It should also be noted that the sensor chip 28 also directly in the sensor socket 37 can be attached. This is based on the 8th and 9 explained in more detail.

8th shows a perspective view of a sensor module 45 with a partially cut-open sensor socket 46 which is a central implementation 47 having. In the implementation 47 is a seal 48 introduced by the implementation 47 passed sensor chip 28 holds. The sensor chip 28 For example, in the seal 48 be poured.

At the in 8th illustrated sensor module 45 covers the seal 48 lateral edge surfaces 49 and 50 only partially off. A front edge surface 51 and a rear edge surface 52 stay untouched. In this respect, it is possible even after the completion of the sensor module 45 the sensor chip 28 to contact.

In 9 is another sensor module 53 shown in which a sensor socket 54 one the sensor room 41 the sensor socket 37 out 7 corresponding sensor space 55 with a sensor opening provided for the entry of the medium to be detected 56 having. In the sensor module 53 leads the implementation 47 to the sensor room 55 , In the implementation 47 becomes the sensor chip 28 from the seal 48 held.

It should be noted that the seal 48 preferably tapered starting from the pressure side to the connection side, whereby the seal 48 self-sealing effect. In the in the 8th and 9 Illustrated embodiments is the seal 48 for example, conical, wherein the base of the seal is aligned to the pressure side.

In the formation of plastic sleeves 9 and 11 as well as the seal 48 Care must be taken that the plastic used preferably has a comparable coefficient of thermal expansion as the sensor chip 2 or 28 and the ladder grid 4 or the bonding wires 5 , Preferably, for the plastic sleeves 9 and 10 as well as the seal 48 Epoxy-based plastics are used because the parameters such as glass transition temperature T _G , modulus of elasticity and thermal expansion coefficient can be varied by the composition or adjusted via the potting parameters. The functional reliability of the sensor modules described here is also largely compensated by the release of the sensor chip 2 or 28 at. In this way, the shrinkage of the epoxy-based plastic sheaths results 9 and 11 as well as the seal 48 not to a mechanical load on the sensor surface 3 which could distort the measurement signal.

The one of the plastic covers 9 and 11 isolated area of the sensor chips 2 or 28 can be surface-passivated by an additional coating. The coating may comprise on the basis of oxides, nitrides or carbides or else on the basis of polyimide or other polymers, for example polymers deposited from the gaseous phase, in particular so-called parylenes. Precious metals can also be used for coating and surface passivation of the sensor chip 2 come into question.

The surface passivation can also be done using silicone. A combination of different protective layers can also be used. Furthermore, the protective layer can only be applied to the sensor chip 2 or 28 or on the plastic cover 11 or the seal 48 extend. In particular, the coating can also be applied to the edges of the sensor chip 2 extend.

With the sensor chips 2 and 28 they can be sensor chips in which the evaluation circuit is integrated. In addition, but also sensor chips can be used, which only a sensor surface 3 and have no evaluation circuit.

Furthermore, in the sensor chip 2 or 28 next to the sensor surface 3 further be formed on thermodynamic or fluid mechanical parameters of a medium to be detected sensitive areas. For example, in addition to a pressure sensor, a temperature sensor in the sensor chip 2 or 28 be integrated. The sensor elements that are sensitive to thermodynamic or fluid mechanical variables can be on the same side or on opposite sides of the sensor chip 2 or 28 be arranged.

Instead of the ladder grid 4 and 25 It is also possible to use other conductor carriers, for example rigid or flexible printed circuit boards or foils.

Finally, in the plastic shell 11 Additional recesses may also be provided which serve, for example, for the final calibration or trimming of the sensor modules described here. After completion of the final calibration or trimming these recesses can be sealed with a potting.

The sensor measurements 37 . 46 and 54 are preferably made of a metallic material, but may also be made of a plastic.

In a modified embodiment of the sensor modules 1 . 24 and 36 The plastic cover extends only on one side of the conductor grid 4 but preferably over that side of the conductor grid 4 , on which the contacts between the sensor chip 2 and the ladder grid 4 are located.

Instead of the provided on the top with contact points sensor chip 2 It is also possible to use so-called ball grid array sensor chips or so-called flip chips. In this case, on the bonding wires 5 and the plastic shell 9 be waived.

Finally It should be noted that features and properties that are in Described in connection with a particular embodiment have been, even with another embodiment can be combined except when this is out For reasons of compatibility is excluded.

After all It should be noted that in the claims and in the description the singular includes the plural, unless otherwise stated in the context. In particular, if the indefinite article is used is both the singular as well as the plural meant.

1

sensor module

2

sensor chip

3

sensor surface

4

lead frame

5

bonding wire

6

capacitor

7

capacitor

8th

Bond area

9

Plastic sheath

10

border area

11

Plastic sheath

12

Contact end

13

burl

14

rejuvenation

15

conductor path

16

conductor path

17

conductor path

18

bearing surface

19

border area

20

rear edge surface

21

lateral edge surface

22

lateral edge surface

23

front edge surface

24

sensor module

25

lead frame

26

holding area

27

recess

28

sensor chip

29

sensor end

30

circuit area

31

circuit area

32

circuit area

33

circuit area

34

contact area

35

Contact end

36

sensor module

37

sensor version

38

admission

39

execution

40

plug compartment

41

sensor chamber

42

thread

43

sensor opening

44

seal

45

sensor module

46

sensor version

47

execution

48

seal

49

lateral edge surface

50

lateral edge surface

51

front edge surface

52

rear edge surface

53

sensor module

54

sensor version

55

sensor chamber

56

sensor opening

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 2007/0139044 A1 [0003]
• US 2004/0118227 A1 [0004]

Claims (14)

Sensor module with a sensor chip ( 2 . 28 ) covered by a plastic cover ( 9 . 11 . 48 ), characterized in that the plastic cover ( 9 . 11 . 48 ) a sensor surface ( 3 ) and at least partially a lateral edge region ( 20 - 23 . 49 - 52 ) of the sensor chip ( 2 . 28 ) leaves free. Sensor module according to claim 1, characterized in that the sensor chip ( 2 . 28 ) with in the sensor module ( 1 . 24 . 36 . 45 . 53 ) formed tracks ( 15 . 16 . 17 ) connected is. Sensor module according to claim 2, characterized in that a connection region between the sensor chip ( 2 . 28 ) and printed conductors ( 15 . 16 . 17 ) from the plastic cover ( 9 . 11 ) is covered. Sensor module according to one of claims 1 to 3, characterized in that the sensor chip ( 2 . 28 ) with a lateral edge surface ( 20 ) extends over at least one conductor track. Sensor module according to one of claims 1 to 4, characterized in that one along the sensor chip ( 2 ) running track ( 16 ) from the plastic cover ( 11 ) stands out. Sensor module according to one of claims 1 to 5, characterized in that the plastic cover ( 11 . 48 ) in a sensor socket ( 37 . 46 . 54 ) is introduced. Sensor module according to claim 6, characterized in that the plastic cover ( 11 . 48 ) sealing a bushing ( 39 . 47 ) serves. Sensor module according to one of claims 2 to 7, characterized in that the conductor tracks ( 15 . 16 . 17 ) from a ladder grid ( 4 ) are formed. Sensor module according to one of claims 1 to 8, characterized in that the sensor chip ( 2 ) is elongated and the sensor surface ( 3 ) in an end region ( 29 ) of the sensor chip ( 28 ) is arranged. Sensor module according to one of claims 1 to 9, characterized in that the sensor chip ( 2 ) is provided with a surface passivating layer. Sensor module according to one of claims 1 to 10, characterized in that the sensor chip ( 2 ) is a pressure sensor. Method for producing a sensor module, in which a sensor chip ( 2 . 28 ) with a plastic cover ( 11 . 48 ) is covered, characterized in that by the shape of the plastic cover ( 11 . 48 ) a sensor surface ( 3 ) and at least partially a lateral edge region ( 20 - 23 . 49 - 52 ) of the sensor chip ( 2 . 28 ) is left free. Method according to claim 12, characterized in that the sensor chip ( 2 ) with the plastic cover ( 11 ) and the plastic cover ( 11 ) with the sensor chip ( 2 ) into a recording ( 38 ) of a sensor socket ( 37 ) is introduced. A method according to claim 12, characterized in that the elongate sensor chip ( 2 ) in an implementation ( 47 ) of a sensor socket ( 46 . 54 ) is arranged and the plastic cover a seal ( 48 ) of the implementation ( 47 ).