CN114071871A

CN114071871A - Circuit board with ferromagnetic layer

Info

Publication number: CN114071871A
Application number: CN202110857298.8A
Authority: CN
Inventors: M·J·弗朗茨
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2020-07-29
Filing date: 2021-07-28
Publication date: 2022-02-18
Also published as: DE102020209543A1

Abstract

The present invention relates to a circuit board, and more particularly, to a multilayer circuit board. The circuit board has at least two electrically insulating layers and at least one electrically conductive layer. The circuit board has at least one induction coil formed from a conductive layer of the circuit board. According to the invention, the circuit board has at least one ferromagnetic layer, wherein the ferromagnetic layer is enclosed between at least two layers, in particular electrically insulating layers, of the circuit board. The circuit board has an electrically conductive bridge which is guided through the circuit board. The bridge comprises a conductive element, wherein a connection of the induction coil is electrically connected by means of the bridge to a conductive layer guided in a plane of the circuit board parallel to the connection. Preferably, the bridge passes through the ferromagnetic layer. The circuit board has an electrically insulating element, wherein the ferromagnetic layer is electrically insulated from the electrically conductive element of the bridge portion by means of the electrically insulating element.

Description

Circuit board with ferromagnetic layer

Technical Field

The invention relates to a circuit board, in particular to a multilayer circuit board. The circuit board has at least two electrically insulating layers and at least one electrically conductive layer. The circuit board has at least one induction coil formed from a conductive layer of the circuit board.

Background

A multilayer substrate having a first winding part of a magnetic component formed in a first metallization layer and having an electrically insulating layer is known from the document DE 102009046183 a1, wherein the multilayer substrate comprises a polymer having a ferromagnetic component and the polymer is applied to a surface of the multilayer substrate above the first winding part.

A circuit carrier is known from document US 6603080B 2, which is designed to suppress electromagnetic interference. The circuit carrier has an electrically conductive layer and an electrically insulating layer which enclose a ferrite layer between one another, wherein the ferrite layer has ferrite powder.

Disclosure of Invention

According to the invention, the circuit board has at least one ferromagnetic layer, wherein the ferromagnetic layer is enclosed between at least two layers of the circuit board, in particular between at least two electrically insulating layers of the circuit board. The circuit board has a conductive bridge which is guided through the circuit board. The bridge comprises a conductive element, wherein a connection of the induction coil is electrically connected by means of the bridge to a conductive layer guided in a plane of the circuit board parallel to the connection. Preferably, the bridge passes through the ferromagnetic layer. The circuit board has an electrically insulating element, wherein the ferromagnetic layer is electrically insulated from the electrically conductive element of the bridge portion by means of the electrically insulating element.

Advantageously, such a circuit board with ferromagnetic layers can be provided cost-effectively. That is, the bridging portion may advantageously be manufactured in an electrically insulating element which is configured in a through hole in the circuit board.

In a preferred embodiment, the coils are formed in planes different from one another and have respective coil windings formed by electrically conductive layers. The coil windings of the induction coil, which are formed in mutually different planes, are electrically connected to one another by means of at least one bridge. Advantageously, the induction coil can thus be constructed compactly inside the circuit carrier. In this way, an electronic component can be arranged on the outer surface of the circuit carrier. Further advantageously, the induction coil may thus comprise coil windings which respectively have the same winding diameter.

In a preferred embodiment, the induction coil is formed by a conductive layer of the printed circuit board, the windings of which, in contrast to the above, each extend in the same plane. Preferably, the coil can be designed as a spiral, in particular as an archimedean spiral. For this purpose, the windings of the induction coil have a winding radius which decreases radially inward from winding to winding.

In a preferred embodiment, the bridge element has an electrically conductive sleeve. The conductive sleeve may be filled with a solder, for example. The conductive sleeve is produced in the insulating element, for example in an electroplating manner.

In a preferred embodiment, the electrically insulating element is formed along the entire thickness extension of the circuit board. The electrically insulating element can thus be pressed as a plastic body into the circuit board, in particular into a hole or recess in the circuit board. In another embodiment, the electrically insulating element can be scraped into the indentation in the form of a paste-like resin and subsequently cured. The electrically insulating element can therefore advantageously be integrated into the circuit board process in a cost-effective manner.

In a variant of the circuit board, the electrically insulating element may pass through the circuit board along the entire thickness extension (except for the protective lacquer).

In a preferred embodiment of the circuit board, the electrically insulating element is made of a different material than the electrically insulating layer. For example, the material of the electrically insulating layer is formed of a fiber-reinforced epoxy resin. The material of the electrically insulating element is formed, for example, from a thermoplastic.

In a further advantageous embodiment, the electrically insulating element is formed from a plastic, in particular a fiber-reinforced plastic, in particular an epoxy resin. In this embodiment, the electrically insulating element may be formed from the same plastic as the electrically insulating layer.

In a preferred embodiment, the circuit board has two induction coils, which are arranged and designed to be electromagnetically operatively connected to one another. The circuit board in this embodiment has a transformer, which is advantageously integrated in the circuit board.

Preferably, the two induction coils are arranged opposite one another, so that the field lines of one of the two induction coils can pass through one of the two receiving coils. Advantageously, this allows a space-saving coupling of the two induction coils.

In a preferred embodiment, the induction coils are each formed as an inner conductive layer in the printed circuit board. Advantageously, the transformer can be integrated in the circuit board in such a space-saving manner that an outer surface of the circuit board can be equipped with electronic components, in particular SMD components (SMD ═ surface mount devices).

The invention also relates to a method of connecting a coil formed from an electrically conductive layer to a circuit board. In this method, a cut is produced in the circuit board through a ferromagnetic layer formed in the circuit board. In a further step, the recess is filled with, in particular, a fiber-reinforced plastic. Preferably, the plastic is scraped into the indentations. In a further step, electrically conductive bridges are produced in the thus produced plastic inlay which fill the gaps, said bridges being insulated with respect to the ferromagnetic layer.

Preferably, the bridge connects the terminals of the coil with the wiring plane outside the circuit board. Preferably, the terminals of the coil are connected to the coil driver or receiver by means of electrically conductive bridges. This advantageously results in a space-saving construction.

Drawings

The invention is described below with the aid of figures and other embodiments. Further advantageous embodiments result from the combination of the features described in the figures and in the dependent claims.

Fig. 1 shows an exemplary embodiment of a method for producing a printed circuit board, in which an electrically insulating bridge is formed in an opening in the printed circuit board, in which opening a layer formed ferromagnetically is embedded as an inner layer;

fig. 2 shows an embodiment of a multilayer printed circuit board, in which the transformer is embodied in the form of a layer as an internal electronic component.

Detailed Description

Fig. 1 shows an embodiment of a method for producing a circuit board 1. The printed circuit board 1 has in this embodiment two electrically

insulating layers

2 and 52 which enclose a ferromagnetic layer 3 between one another, in particular in the form of a sandwich. The layer stack shown in fig. 1, which comprises the two electrically

insulating layers

2 and 52 and the ferromagnetic layer 3 enclosed between them, can be produced in one method step 10 by lamination. The electrically insulating layer is formed, for example, by a fiber-reinforced epoxy layer, also referred to as prepreg layer. The ferromagnetic layer 3 is formed, for example, from a particle-filled plastic layer, wherein the particles are formed from ferromagnetic particles, in particular manganese ferrite particles.

Fig. 1 also shows a step 11 for producing an insulating bridging gap (Via-Durchbruch), in which a gap 4 and thus a drilled, punched or milled circuit board 1' are produced in the circuit board. In this exemplary embodiment, the recess 4 has a recess width 7 and is configured, for example, as a cylindrical bore. The gap 4 extends through the ferromagnetic layer 3 ' and the electrically insulating layers 2 ' and 52 '.

In a method step 12, the recess 4 is filled with a plastic material 5 by means of a scraper 6. The plastic material 5 in this embodiment completely fills the gap 4. After curing of the plastic material 5, for example by means of a radical crosslinker or by means of UV radiation, the circuit board 1 filled with the plastic material 5 in step 12 can be provided with a further recess 9 in step 13. For this purpose, a recess 9 is produced in the plastic inlay 5 produced in step 12. The plastic inlay 5 forms in this embodiment the previously described electrically insulating element.

The recess 9 produced in step 13, which is configured in the present exemplary embodiment as a cylindrical bore, has a diameter 8. The diameter 8 of the recess 9 produced in the plastic inlay 5 is configured to be smaller than the diameter 7 of the plastic inlay 5. In this way, an electrically insulating sleeve remains in the circuit board 1 '″ (in particular in the case of a recess 9 provided centrally in the plastic inlay 5), which sleeve insulates the recess 9 from the ferromagnetic layer 3'.

In a method step 14, the recess 9 in the plastic inlay 5 produced in step 13 can then be metallized, so that an electrically conductive bridge is produced which electrically connects two mutually opposite outer sides of the circuit board 1 to one another. In step 14, the circuit board 1 "" is provided with two electrically

conductive layers

15 and 16, which are connected to the electrically insulating

layer

2 or 52, respectively, in particular by lamination. The

conductive layers

15 and 16 extend on opposite sides of the circuit board 1'. In this exemplary embodiment, the bridging gap 9 is applied, in particular, by means of electroplating, with a conductive layer which forms the conductive sleeve 17. The

conductive layers

15 and 16 are electrically connected to each other in the gap by means of a conductive sleeve 17. The conductive sleeve 17 is electrically insulated from the ferromagnetic layer 3 'by the plastic inlay 5'.

In this exemplary embodiment, the recess 9 is filled with a solder 18, in particular a solder which enables a reflow process, in particular for improving the electrical conductivity.

The electrically conductive bridging gap produced in step 14 can advantageously be integrated in standard circuit board manufacturing processes. Such standard processes include, for example, laminating electrically conductive and electrically insulating layers on one another, drilling the layers thus laminated and electroplating the gaps for producing electrically conductive bridging gaps in the circuit board.

Fig. 2 shows an exemplary embodiment of a printed circuit board 20, which is designed as a multilayer printed circuit board. An internal transformer is formed in the multilayer printed circuit board 20, the printed circuit board 20 having at least one or, as shown in the exemplary embodiment, two ferromagnetic layers 24 and 26 for the electromagnetic coupling of the primary and secondary coils, by means of which the magnetic field of the coupling coil can be intensified.

The printed circuit board 20 comprises in this exemplary embodiment two partial printed

circuit boards

21 and 22 which are connected to one another by means of an electrically insulating layer 54, in particular a prepreg layer, for example a fiber-reinforced epoxy layer, and which enclose the electrically insulating layer 54 between one another.

The

sub-circuit boards

21 and 22 are produced, for example, by the method shown in fig. 1 and each have two electrically conductive bridging gaps. The

partial circuit boards

21 and 22 each have an internal ferromagnetic layer 24 or 26, respectively, which is enclosed between electrically insulating layers (in particular in the form of a sandwich) and is electrically insulated from the electrically conductive bridging gap. The daughter circuit board 21 in this exemplary embodiment has a bridge recess 28 and a bridge recess 27, which are arranged at a distance from one another. Of the electrically insulating layers of the

sub-circuit boards

21 and 22, a layer 23 of the sub-circuit board 21 and a layer 25 of the sub-circuit board 22 are exemplarily indicated. The bridging gap 28 is insulated from the ferromagnetic layer 24 by means of an electrically insulating plastic inlay 37, and the bridging gap 27 is insulated from the ferromagnetic layer 24 by means of an electrically insulating inlay 38. In this exemplary embodiment, the bridging gap 28 comprises an electrically conductive metal flange 51, which is produced in particular in an electroplating manner, which adjoins and is electrically connected to the coil winding 34 formed from an electrically conductive layer, in particular a conductor track.

The sub-circuit board 21 has a spiral-shaped primary coil formed from an electrically conductive layer, which primary coil has two

primary coil windings

34 and 35. The primary coil winding 34 here forms an outer winding which surrounds an inner winding 35. The electrical connections 36 of the inner primary coil winding 35 are guided by means of the electrically conductive webs 27 to the side of the sub-circuit board 21 opposite the primary coil. The side of the sub-circuit board 21 opposite to the primary coil forms a mounting side, which is equipped with electronic components, in this embodiment with the drive module 31. The drive module 31 is designed in this exemplary embodiment as an SMD component and has two

electrical output connections

32 and 33. The daughter circuit board 21 has two

conductive layers

29 and 30, which are connected to

contacts

32 or 33, respectively. The conductive layer 29, which forms the conductor tracks on the mounting side of the printed circuit board 21, is connected to the connections 36 of the primary coil by means of the bridging gaps 27. The outer primary coil winding 34 is connected by means of the webs 28 to the conductive layer 30 on the mounting side and thus to a further electrical output terminal 33 of the driver 31. The driver 31 can thus energize the primary coil on the opposite side of the sub-circuit board 21 to generate an electromagnetic alternating field.

The sub circuit board 22 is formed corresponding to the sub circuit board 21 and has a secondary coil formed of a conductive layer of the sub circuit board 22. The secondary coil is opposed to the primary coil of the sub-circuit board 21. The secondary coil comprises two coil windings, an outer coil winding 48 and an inner coil winding 49 surrounded by said outer coil winding. The electrical connections 50 of the internal coil winding 49 are connected to the conductor tracks 44 on the side of the printed circuit board 22 opposite the secondary coil by means of electrically conductive bridging gaps 39. The outer secondary winding 48 is connected by means of the electrically conductive bridge 40 to a conductor track 45, which is connected to the printed circuit board 22 on the mounting side of the printed circuit board 22.

In this exemplary embodiment, the printed circuit board 22 has a receiver 41 on the mounting side, which has two input terminals 42 and 43, which are each connected to the secondary winding on the input side by means of electrically

conductive bridging connections

39 and 40. The input connection 42 of the receiver 41 is connected to the conductive layer 44 and thus to the connection 50 of the inner secondary winding by means of the bridge 39. The other input connection 43 of the receiver 41 is electrically connected to an external secondary winding 48 by means of the conductor tracks 45 and therefore also by means of the bridge 40.

The bridge connection 40 is insulated from the ferromagnetic layer 26 by an electrically insulating plastic inlay 46, and the inlay 39 is insulated from the ferromagnetic layer 26 by an electrically insulating plastic inlay 47.

In this exemplary embodiment, the primary coil and the secondary coil are each designed as a spiral coil, in particular as an archimedean spiral coil. In a further embodiment, the coils of the transformer can also be designed as coils, which each form at least two coil windings having the same winding diameter, wherein directly successive coil windings of the same coil are connected to one another by means of an electrically conductive bridge. In this embodiment, the electrically insulating layer extends between the individual coil windings, which are each designed as an electrically conductive layer, in particular as a printed conductor. The coil can be constructed in this way as a multilayer coil in a multilayer circuit board.

In this exemplary embodiment, the primary and secondary windings of the transformer, which are formed internally in the printed circuit board 20, connect the electrically insulating layers 54 to one another. The primary coil and the secondary coil are each designed in this exemplary embodiment for coupling to one another by means of an electromagnetic field 53. The electromagnetic field 53 extends in this embodiment in an electrically insulating layer 54, wherein the field lines of the coupling field extend transversely or with at least one transverse component with respect to the flat extension of the circuit board 20 and thus also through the ferromagnetic layers 24 and 26. The electromagnetic field 53 can thus be enhanced by means of the ferromagnetic layers 24 and 26.

Advantageously, in the multilayer printed circuit board 20, all components of the transformer, in particular the primary and secondary coils, and also the ferromagnetic layers 24 and 26, which act to reinforce the magnetic field, are formed as internal layers in the multilayer printed circuit board 20.

Claims

1. Circuit board (1, 20), in particular a multilayer circuit board, having at least two electrically insulating layers (2, 52, 54) and at least one electrically conductive layer (15, 16, 34, 48), wherein the circuit board (1, 20) comprises at least one induction coil (34, 48) which is formed by the electrically conductive layer of the circuit board (1, 20),

characterized in that the circuit board (1, 20) has at least one ferromagnetic layer (3, 24, 26), wherein the ferromagnetic layer (3, 24, 26) is designed as an inner layer and is enclosed between at least two layers (2, 52) of the circuit board (1, 20), in particular between at least two electrically insulating layers of the circuit board, and an electrically conductive bridge (17, 5) is guided through the circuit board (1, 20), wherein the bridge comprises an electrically conductive element (17, 18, 27, 28, 39, 40), wherein a connection (36, 50) of the induction coil (34, 48) is electrically connected by means of the bridge (17, 18, 27, 28, 39, 40) to an electrically conductive layer (15, 16) guided in a plane of the circuit board (1, 20) parallel to the connection, wherein the bridge (17, 26), 18. 27, 28, 39, 40) passes through the ferromagnetic layer (3, 24, 26), and the circuit board (1, 20) has an electrically insulating element (5, 37, 38, 46, 47), wherein the ferromagnetic layer (3, 24, 26) is electrically insulated from the electrically conductive element (17, 27, 28, 39, 40) of the bridge by means of the electrically insulating element.

2. Circuit board (1, 20) according to claim 1, characterized in that the induction coil (34, 48) has coil windings (34, 35, 48, 49) which are in mutually different planes and which are each formed by an electrically conductive layer, and the coil windings of the induction coil which are formed in mutually different planes are electrically connected to one another by means of at least one bridge (27, 28, 29, 40).

3. A circuit board (1, 20) according to claim 1 or 2, characterized in that the induction coil (34, 48) is formed by a conductive layer of the circuit board, the windings (34, 35, 48, 49) of the induction coil extending in the same plane, respectively.

4. Circuit board (1, 20) according to one of the preceding claims, characterized in that the bridging parts (17, 18) have electrically conductive sleeves (17).

5. Circuit board (1, 20) according to any one of the preceding claims, characterized in that the electrically insulating element (5, 37, 38, 46, 47) is constituted along the entire thickness extension of the circuit board (1, 20).

6. Circuit board (1, 20) according to any of the preceding claims, characterized in that the material of the electrically insulating element (5, 37, 38, 46, 47) is different from the material of the electrically insulating layer (2, 52, 23, 25).

7. Circuit board (1, 20) according to one of the preceding claims, characterized in that the electrically insulating element (5, 37, 38, 46, 47) is formed from a plastic, in particular a fiber-reinforced plastic, in particular an epoxy resin.

8. Circuit board (1, 20) according to one of the preceding claims, characterized in that the circuit board (1, 20) has a transformer with two induction coils (34, 48) which are arranged and constructed to be electromagnetically operatively connected to each other.

9. The circuit board according to claim 8, wherein the induction coils (34, 48) are each formed as an inner conductive layer in the circuit board (1, 20).

10. Method for connecting a coil formed from electrically conductive layers to a circuit board, wherein an induction coil (34, 48) produces a recess (4) in the circuit board (1, 20), which recess passes through a ferromagnetic layer (3, 24, 26) formed in the circuit board (1, 20), and the recess (4) is filled with a plastic (5), in particular fiber-reinforced plastic, and in the produced plastic inlay (5) a conductive bridge (17, 18) is produced, which bridge is insulated with respect to the ferromagnetic layer (5) and connects a connection of the induction coil (36, 50) to an external wiring plane of the circuit board (1, 20).