EP2949003A1

EP2949003A1 - Method for electrically connecting a coaxial conductor to a circuit carrier

Info

Publication number: EP2949003A1
Application number: EP14700233.1A
Authority: EP
Inventors: Alexander Lux; Markus Reinhard; Patrik Patzner
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2013-01-22
Filing date: 2014-01-07
Publication date: 2015-12-02
Also published as: US9728929B2; JP2016506059A; WO2014114479A1; US20150364892A1; JP6000476B2; DE102013200971A1

Abstract

The invention relates to a method for electrically connecting a coaxial conductor (16) to a circuit carrier (12), particularly a circuit board, wherein the circuit carrier (12) has a top side (26) and a bottom side (24), wherein conducting tracks (28, 30) are arranged at least on the top side (26) of the circuit carrier (12). The coaxial conductor (16) also comprises an inner conductor (18) and an outer conductor (22), wherein the coaxial conductor (16) is at least partially fed through a feed-through (14) provided in the circuit carrier (12) from the bottom side (24) of the circuit carrier (12). Furthermore, at least one first contact conductor (34) is used to electrically connect the outer conductor (22) to at least one first conducting track (28) of the circuit carrier (12) and at least one second contact conductor (42) is used to electrically connect the inner conductor (18) to at least one second conducting track (30) of the circuit carrier (12). The first and the second contact conductors (34, 42) each have a press-in connection at at least one of the points of contact (32) thereof with the circuit carrier (12) or with the coaxial conductor (16).

Description

Description title

Method for electrically connecting a coaxial conductor to a

Circuit board prior art

The invention is based on known methods and devices for determining composition of fuel mixtures. Thus, for example, in motor vehicles increasingly fuel mixtures are in use, which in addition to the actual mineral oil fuels can process an admixture of ethanol and / or other alcohols. For example, so-called flex-fuel vehicles are known, which can be operated with variable ethanol / gasoline mixtures. Usually, the parameters of the engine control of the motor vehicle are adapted to the composition of the fuel mixture. The determination of the ethanol-fuel mixture ratio is usually either on the basis of existing measured variables by means of software in the control unit itself, or this mixing ratio can be detected with an ethanol sensor. Such ethanol sensors can be based on numerous different measurement principles. In particular, capacitance measuring methods based on permittivity and conductivity determination are used here. As a rule, the permittivity of the fuel mixture is determined at frequencies up to approximately 1 MHz.

In order to identify other components, such as water, measurements in the GHz range are necessary because here the permittivity of alcohol, water and other polar components, such as interfering components, due to the

Orientation polarization decreases sharply with increasing frequency. A known measuring method is the measurement of an absorption, transmission or reflection of microwaves by the fuel mixture. An example of such methods operating in the GHz range is disclosed in DE 34 12 704 A1. Furthermore, a method for determining a composition of a fuel mixture is known from DE 10 2008 044 403 A1, in which a characteristic course of a specific response to a microwave irradiation over a larger frequency range for determining the properties of the fuel mixture detected and from there to the composition of the fuel mixture is closed. An advantage of the method described in DE 10 2008 044 403 A1 is, in particular, that the accuracy can be increased by using larger frequency ranges, so that, for example, alcohol-fuel mixtures, which additionally additionally contain a water content and / or additives, characterize considerably more accurately can be compared to traditional methods.

In microwave or high frequency measurement applications, usually, coaxial cable connectors and cables are used to connect a microwave conductor. In particular, in the case of such fuel sensors, sensor electronics provided at least for partial evaluation or signal conditioning may be arranged in the immediate vicinity of the measuring element, which is connected to the coaxial terminal of the measuring element for coupling the detected microwave signal. Due to the high demands on the signal quality and the

Signal transmission is known to use bonds or solder joints, which also provide a necessary thermal decoupling.

However, there is room for improvement regarding the coupling of the

Microwave signal in the sensor electronics.

Disclosure of the invention

Accordingly, a method and a device are proposed which can be used for electrically connecting a coaxial conductor to a circuit carrier, in particular a printed circuit board. The method according to the invention initially provides that the circuit carrier has an upper side and a lower side, wherein, preferably for implementation and provision of sensor electronics, conductor tracks are arranged at least on the upper side of the circuit carrier. The coaxial conductor further comprises an inner conductor and an outer conductor, which is known to be separated by an electrically insulating dielectric, such as an epoxy resin, for example, the inner conductor and the dielectric jacketed. Furthermore, it is provided according to the invention that the coaxial conductor from the underside of the circuit carrier ago at least partially by a in the

Circuit board provided implementation is passed. The passage can be formed for example by a corresponding hole through the circuit carrier, wherein the implementation preferably has a larger inner diameter than the Au ßendurchmesser the coaxial conductor. Furthermore, it is inventively provided that at least one first contact conductor is used for electrically connecting the Au ßenleiters with at least one first conductor of the circuit substrate, and that at least a second contact conductor for electrically connecting the inner conductor is used with at least one second conductor of the circuit substrate. A contact conductor is generally understood to mean an electrical conductor, which is preferably made of metal and may have a predetermined profiled shape. Essentially, the contact conductor serves to provide an electrically conductive connection between at least the first conductor track with the outer conductor and at least one second conductor track with the inner conductor of the coaxial conductor. For this purpose, it is further provided that the first and the second contact conductor at at least one of its contact points, the circuit carrier or the coaxial conductor out, a

Press-in connection has. The press-in connection according to the invention is hereby preferably produced by press-fit contacts. According to the invention, this advantageously creates a possibility of providing a connection with only little mechanical outlay and in a simple manner, which provides the

Requirements for signal quality in signal transmission as well as the stability and reliability of the junction. The use of a press-in connection also provides the advantage that due to the fact that this is a solder-free electrical connection, the generation, or the formation of unwanted solder bridges during manufacture, as well as age-related occurrence of so-called cold solder joints at a later use of the circuit substrate and the coaxial conductor can be avoided in an advantageous manner. The contact conductors are for this purpose preferably made of copper or a copper alloy, such as so-called Beryliumkupfer. Other alloys with comparable properties are also conceivable.

In an inventive press-fitting of the contact conductors, in particular provided in holes for this purpose in the circuit carrier, which are lined for example by a metallic and in particular electrically conductive sleeve, is characterized by a slight deformation of the pressed-in contact conductor in the bore created a gas-tight electrical connection, which is characterized in a particularly advantageous manner by a high reliability and longevity. Furthermore, the contact conductors are preferably configured geometrically such that they have a freedom of movement necessary for thermal decoupling. Due to the different materials of the circuit carrier and the coaxial conductor occurs when changing the temperature to also different dimensions of the circuit substrate and the coaxial conductor. The contact conductor is further preferably adapted to the different coefficients of expansion of the

compensate for different material properties of the circuit substrate and the coaxial conductor. In particular, it is advantageous in this case that to compensate for the different coefficients of thermal expansion of circuit carrier and coaxial conductor by the geometry of the contact conductor damage, in particular in the region of the contact points between the contact conductor and each of the coaxial conductor and the circuit carrier, by temperature changes and thus an increase in Contact resistance over the lifetime across advantageously avoided.

Furthermore, it can be provided in the method according to the invention that the first and / or the second contact conductor has an annular conductor section. In particular, this also contributes to the compensation of different coefficients of thermal expansion with regard to the advantage described above in that a stiffness is created in the contact conductor itself which withstands any lateral shear forces or tensile forces which may occur.

According to a further embodiment of the method, it can be further provided when the first contact conductor contacts the outer conductor almost completely. In this case, it may be advantageous, for example, for the first contact conductor to have an annular conductor section in order to be able to compensate circumferentially for the currents or potentials transmitted, in particular via a plurality of contact points, to a first conductor track of the circuit substrate, which can preferably be connected to the potential equalization with a ground conductor, as large as possible and can be initiated with a low contact resistance. In addition, creates an optionally provided annular

Conductor portion in the first contact conductor has the advantage of a large-area contact, which can also be realized by a plurality of contact strips. Farther For example, the number of contact points of the first contact conductor with the circuit carrier, in particular with a first conductor track of the circuit carrier, can come into contact with the number of the outer conductor or the inner conductor

Distinguish contact strips.

The second contact conductor may also have an annular conductor section for increasing the rigidity and shape stability.

Furthermore, according to a further embodiment of the method, it may be advantageous if the first and / or the second contact conductor has a C-shaped section in the region of the contact with the outer conductor or the inner conductor and the outer conductor and / or the inner conductor for contacting a spring force applied. The idea underlying the invention, a compound of the contact conductor by means of a press-in, is here on the side toward the coaxial conductor out and further developed such that the bent to a C-shape contacting a smaller opening diameter than the Au ßendurchmesser of Au ßenleiters form. According to this embodiment, when plugging the first contact conductor onto the outer conductor of the coaxial conductor, the plurality of contact strips bent in a C-shape are displaced outward by the difference of the two aforementioned diameters, thereby further exerting a spring force on the outer conductor. The same applies accordingly for possibly provided C-shaped contacting portions of the second contact conductor, which also contact a preferably for Au ßenleiter axially elongated inner conductor by uncovering the same also circumferentially.

Alternatively or additionally, it may further be provided that the first and / or the second contact conductor for electrical connection to the first conductor track and / or the second conductor track is soldered onto correspondingly provided contacting surfaces and / or welded. In this case, a laser soldering or, alternatively, a reflow soldering or a piston soldering can preferably be used as the soldering process. As a welding process, in particular a laser welding has been found to be advantageous, but can also be done by a Spaltschwei rung or Stufenschwei rung. In the case of a press-in connection at the contact points of the first and the second contact conductor with the respective first and second conductor track on the circuit carrier it may be further provided in the proposed method, that the first and / or the second contact conductor is connected in accordance with the ßenleiter Au or the inner conductor by a solder joint or welded joint. For this purpose, use of the aforementioned soldering and welding methods is also conceivable.

According to a further embodiment of the method proposed according to the invention, it can further be provided that the first contact conductor is arranged on the underside of the circuit carrier. Here is a contact of the first

Contact conductor with the Au ßenleiter readily possible and a corresponding contacting of the contact conductor with the first conductor of the circuit substrate due to the lining of the holes in the circuit substrate with electrically conductive eyelets, which usually also provide a through-connection of the circuit substrate from the top to the bottom guaranteed. In this case, an unintended short circuit development between the first contact conductor and the second contact conductor is also advantageously avoided.

Alternatively or additionally, it may be further provided that the first

Trace and the second trace on opposite sides of the

Circuit carrier are arranged. In this case, the first interconnect of the circuit carrier to be connected to the first contact conductor is preferably arranged on the same side, as described above, for example, the underside of the circuit carrier. This is particularly advantageous if the outer conductor of the coaxial conductor is to be connected to the ground via the first contact conductor, preferably via the first conductor for equipotential bonding. For further shielding, it is likewise conceivable here that the first printed conductor in the form of a large-area copper coating is formed on the underside of the circuit carrier.

Furthermore, it can also be provided in the method proposed according to the invention that the first and / or the second contact conductor a

Plastic extrusion has. In the case of an arrangement of the first and the second contact conductor on the upper side of the circuit carrier, an unintentional contact formation between the first contact conductor and the second contact conductor can likewise be avoided by the plastic extrusion coating. In the proposed method, for example, the following

Process steps may be provided. For example, it may initially be provided that the coaxial conductor is joined into the leadthrough of the circuit carrier and then the first or the second contact conductor is contacted with the outer conductor or the inner conductor and the circuit carrier by the first or the second contact conductor from the upper side of the circuit carrier, for example, preferably in the provided bore is pressed. Subsequently, it can further be provided that the respective other contact conductor is arranged with the outer conductor or the inner conductor and the circuit carrier, preferably in the same way. Furthermore, a sensor device according to the invention is proposed for detecting at least one property of a medium, in particular for detecting a composition of a fuel mixture, which according to the invention comprises at least one sensor and at least one circuit carrier electrically connected to the sensor. In this case, the circuit carrier preferably has an upper side and a lower side, conductor tracks being arranged at least on the upper side of the circuit carrier. According to the invention, the sensor further comprises a coaxial conductor comprising an inner conductor and an outer conductor. In particular, it is further provided that the coaxial conductor is guided at least partially from the underside of the circuit carrier through a passage provided in the circuit carrier. Furthermore, it is provided that the Au ßenleiter is connected to at least one first conductor of the circuit substrate by means of at least one first contact conductor and that the inner conductor is connected by means of at least one second contact conductor with at least one second conductor of the circuit substrate. Furthermore, it is preferably provided that the first and the second contact conductor each have a press-in connection at at least one of its contact points to the circuit carrier or to the coaxial conductor. The inventively proposed device in this case has in particular the same advantages as the method according to the invention described above.

Brief description of the drawings

Embodiments of the invention are illustrated in the figures and are explained in more detail in the following description.

Show it: a schematic sectional view of a portion of the preferred embodiment of the sensor device according to a first

Method step, in particular after the joining of the circuit substrate with the coaxial conductor, a schematic sectional view of a portion of the preferred embodiment of the sensor device according to another

Method step, in particular after contacting the first contact conductor with the outer conductor and the circuit carrier, a schematic sectional view of a preferred embodiment of the sensor device according to the invention after a further step, in particular after contacting the second contact conductor with the inner conductor and the circuit carrier,

Fig. 2 is a schematic sectional view of another embodiment of the sensor device according to the invention, and a schematic side view of another possible

Embodiment of the sensor device according to the invention.

Embodiments of the invention

FIGS. 1 a to 1 c show schematic sectional views of a preferred embodiment of the sensor device 10 in various stages of the preferred embodiment of the method according to the invention.

1 a shows a circuit carrier 12, with a lead-through 14 into which a coaxial conductor 16 is joined. The coaxial conductor 16 in this case has an inner conductor 18 and a separate by a dielectric 20 of the inner conductor 18 Au ßenleiter 22 in a known manner. As the illustration can still be seen, the inner conductor 18 of the coaxial conductor 16 has an end portion which protrudes from the dielectric 20 at the end face.

In this case, the coaxial conductor 16 is joined according to a first method step for mounting the coaxial conductor 16 and the circuit carrier 12 in such a way that the coaxial conductor 16 preferably protrudes into the feedthrough 14 from an underside 24 of the circuit carrier 12 and / or protrudes in sections. Opposite the underside 24 of the circuit substrate 12, this has an upper side 26, on which a first conductor track 28 and a second conductor track 30 are arranged. Furthermore, it can be seen in detail from FIG. 1a that the circuit carrier has 12 contact points 32, which are partially electrically connected to either the first conductor track 28 or the second conductor track 30. Furthermore, it is also possible to provide contact points 32 which are in contact with neither the first printed conductor 28 nor the second printed conductor 30.

Furthermore, in the illustration of FIG. 1 b, the embodiment of the sensor device 10 shown above is represented after a further method step, according to which a first contact conductor 34 with the contact points 32 of the circuit carrier 12 provided for this purpose and connected to the first conductor track 28

Outer conductor 22 of the coaxial conductor 16 has been contacted. For this purpose, the first contact conductor 34 is preferably inserted from the upper side 26 of the circuit carrier 12 here into the corresponding contact points 32 provided for this purpose, preferably producing a press-fit connection. The contact points 32 are preferred for this purpose as

Through contact 36 formed in the form of an electrically conductive contact sleeve.

At the same time, the first contact conductor 34 with a C-shaped section 38 of the first contact conductor 34 encloses the outer conductor 22 of the coaxial conductor 16. The first

Contact conductor 34 is for this purpose preferably designed such that the shaped C-shaped sections 38 form an opening, which preferably have a slightly smaller diameter than the outer diameter of the coaxial conductor 16, in particular of the outer conductor 22. Consequently, the C-shaped portions 38 of the first contact conductor 34 are slightly widened when it is plugged onto the outer conductor 22 of this and then exert a spring force for secure contact with the outer conductor 22. Furthermore, it can be seen in detail from the representation of FIG. 1 b that the first contact conductor 34 has an annular conductor section 40, which gives the first contact conductor 34 a higher rigidity and stability. The illustration of FIG. 1 c shows the preferred embodiment of the sensor device 10 according to the invention after a further method step, according to which a second contact conductor 42 for contacting the inner conductor 18 of the coaxial conductor 16 with the second conductor track 30 is introduced into the contact point 32 provided for this purpose. The introduction of the second contact conductor 42 into the contact points 32 of the circuit carrier 12 provided for this purpose preferably likewise takes place here, producing a press-fit connection. The second contact conductor has according to

Representation of FIG. 1 c also has an annular conductor portion 40, and preferably has a profile shaped in this way, which prevents unintentional contacting of the first contact conductor 34 with the second contact conductor 42. For this purpose, for example, a plastic injection, not shown, of the first

Contact conductor 34 and / or the second contact conductor 42 may be provided, which prevents the unwanted generation of a short circuit between the first contact conductor 34 and the second contact conductor 42.

According to the illustrated preferred embodiment, the second contact conductor 42 for contacting the inner conductor 18 of the coaxial conductor 16 also has a

Press-in connection on. In the illustration of FIG. 2, a further embodiment of the sensor device 10 according to the invention is shown, according to which it can further be provided that the first contact conductor 34 and the second contact conductor 42, for example, only at each second contact point 32 of the circuit substrate 12 to form a

Press-in connection is held and attached to the respective other contact points 32 via a correspondingly provided contacting surface 44 to form a solder joint or a welded joint.

According to a further embodiment of the sensor device 10 according to the invention, it can be provided as shown in FIG. 3 that the first contact conductor 34 is arranged on the underside 24 of the circuit carrier 12 and, for example via a via 36 with the first conductor 28 on the top 26 of

Circuit carrier 12 is connected. However, it is also conceivable that the first conductor track 28 can likewise be arranged on the underside 24 of the circuit carrier 12. Furthermore, the illustration of FIG. 3 can be seen that the first

Contact conductor 34 as well as the second contact conductor 42 each have a plurality of

Contact strip 46 has, which can be formed for example by the introduction of slots 48 and each after plugging on the

Inner conductor 18 or the outer conductor 22 of the coaxial conductor 16, this act in the same manner as the C-shaped portions 38 of the preferred embodiment described above with a spring force.

Claims

Claims 1. Method for electrically connecting a coaxial conductor (16) to a

Circuit carrier (12), in particular a printed circuit board, wherein the circuit carrier (12) has a top (26) and a bottom (24), wherein at least on the top (26) of the circuit carrier (12) conductor tracks (28, 30) are arranged, wherein the coaxial conductor (16) comprises an inner conductor (18) and an outer conductor (22), the coaxial conductor (16) extending from the underside (24) of the

Circuit carrier (12) forth at least partially through a provided in the circuit substrate (12) passage (14) is passed,

characterized,

in that at least one first contact conductor (34) is used for the electrical connection of the outer conductor (22) with at least one first printed conductor (28) of the circuit carrier (12) and that at least one second contact conductor (42) is used for the electrical connection of the inner conductor (18) at least one second conductor track (30) of the circuit carrier (12) is used, wherein the first and the second contact conductor (34, 42) in each case at least one of its contact points (32) to the circuit carrier (12) or to the coaxial conductor (16) out Press-in connection has.

2. The method according to the preceding claim, wherein the first and / or the second contact conductor (34, 42) has an annular conductor portion (40).

3. The method according to any one of the preceding claims, wherein the first contact conductor (34) contacts the outer conductor (22) approximately fully.

4. The method according to any one of the preceding claims, wherein the first and / or the second contact conductor (34, 42) in the region of contacting with according to the outer conductor (22) or the inner conductor (18) has a C-shaped portion (38) and act on the outer conductor (22) and / or the inner conductor (18) for contacting with a spring force.

5. The method according to any one of the preceding claims, wherein the first and / or the second contact conductor (34, 42) for electrically connecting to the first conductor track (28). and / or the second conductor track (30) are soldered on and / or welded onto correspondingly provided contacting surfaces (44).

6. The method according to any one of the preceding claims, wherein the first and / or the second contact conductor (34, 42) with corresponding to the outer conductor (22) or inner conductor (18) are connected by a solder joint or welded joint.

7. The method according to any one of the preceding claims, wherein the first contact conductor (34) on the underside (24) of the circuit carrier (12) is arranged.

8. The method according to any one of the preceding claims, wherein the first conductor track (28) and the second conductor track (30) on opposite sides of

Circuit carrier (12) are arranged.

9. The method according to any one of the preceding claims, wherein the first and / or the second contact conductor (34, 42) comprises a plastic extrusion.

10. The method according to any one of the preceding claims, wherein the method

the following steps:

- Add the coaxial conductor (16) in the bushing (14),

- Contacting the first or second contact conductor (34; 42) with the respective

Outer conductor (22) or the inner conductor (18) and the circuit carrier (12),

- Contacting the other of the other contact conductor (42; 34) each with the Au ßenleiter (22) or the inner conductor (18) and the circuit carrier (12).

1 1. Sensor device (10) for detecting at least one property of a medium, in particular for detecting a composition of a fuel mixture comprising at least one sensor and at least one electrically connected to the sensor circuit carrier (12), wherein the circuit carrier (12) has a top (26) and a Bottom (24), wherein at least on the top

(26) of the circuit carrier (12) conductor tracks (28, 30) are arranged, wherein the sensor further comprises at least one coaxial conductor (16) having an inner conductor (18) and an outer conductor (22), wherein the coaxial conductor (16) of the underside (24) of the circuit carrier (12) forth at least partially by a in

Circuit board (12) provided passage (14) is guided, characterized in that the outer conductor (22) is connected to at least one first conductor track (28) of the

Circuit carrier (12) by means of at least one first contact conductor (34) is connected and that the inner conductor (18) by means of at least one second contact conductor (42) with at least one second conductor track (30) of the circuit substrate (12) is connected, wherein the first and the second contact conductor (34, 42) in each case at at least one of its contact points (32) to the circuit carrier (12) or to the coaxial conductor (16) through a press-in connection.