WO2008119586A1

WO2008119586A1 - Method for the production of an electronic assembly, and electronic assembly

Info

Publication number: WO2008119586A1
Application number: PCT/EP2008/051681
Authority: WO
Inventors: Andreas Kugler; Karl-Friederich Becker; Gerhard Liebing
Original assignee: Robert Bosch Gmbh
Priority date: 2007-03-30
Filing date: 2008-02-12
Publication date: 2008-10-09
Also published as: DE102007015819A1; EP2132967A1; CN101682993A; JP5150720B2; CN101682993B; JP2010524213A

Abstract

The invention relates to a method for the production of an electronic assembly (21), comprising at least one electronic component (9), wherein, in a first step, the at least one electronic component (9) is affixed to an insulating layer (5) of a conductive film (1), wherein the active side of the electronic component (9) is positioned toward the conductive film (1). In a second step, the conductive film (1) having the at least one electronic component (9) attached thereon is laminated onto a printed circuit board carrier (13), wherein the at least one electronic component (9) is positioned toward the printed circuit board carrier (13). As a final step conductors (15) are formed by the structuring of the conductive film (1), and the at least one electronic component (9) is contacted. The invention further relates to an electronic assembly, comprising at least one electronic component (9) that is connected to a conductor structure on a printed circuit board carrier (13). The at least one electronic component (9) is embedded in the printed circuit board carrier (13), and the conductor structure (15, 27) is disposed on the surface of the printed circuit board (23).

Description

description

title

Method for producing an electronic assembly and electronic assembly

State of the art

The invention relates to a method for producing an electronic assembly, comprising at least one electronic component and an electronic assembly GE measure the preamble of claim 9.

In order to encapsulate electronic components that are used in electronic assemblies on printed circuit boards, and to increase the land use on the electronic circuit board, it is known to include the electronic components in the circuit board. As a result, a protection of the electronic components is possible. From US Pat. No. 6,512,182 it is known, for example, to mill recordings in a printed circuit board substrate into which the electronic components are inserted. After inserting the electronic components, the recordings are filled, then smoothed and overlaminated. By embedding the electronic components, a smooth surface of the electronic assembly can be achieved.

Disadvantage of this assembly is that first recordings are milled into the printed circuit board substrate, in which the electronic components are used. An exact positioning of the electronic components is difficult in this way possible.

From DE-A 10 2005 003 125, a method for producing an electrical circuit is known, wherein the circuit comprises electrical components which are mechanically interconnected by a potting compound. On at least one side of the potting compound, at least one layer of conductor tracks is provided, which electrically connects the components to one another. To produce the circuit, the components are applied to a carrier film and then encapsulated with a potting compound. Subsequently, the carrier foil is removed and on the side on which the components with the carrier foil were bound, one or more layers of traces are applied, which electrically connect the components together.

Disadvantage of this method is that the carrier film must be removed without residue in order to achieve a functional shading of the electrical circuit.

Disclosure of the invention

Advantages of the invention

The inventive method for producing an electronic assembly, comprising at least one electronic component, comprises the following steps:

(a) attaching the at least one electronic component to the insulating layer of the conductive carrier film, wherein the active side of the component points in the direction of the film,

(b) laminating the conductive carrier foil with the at least one electronic component fastened thereto onto a printed circuit board carrier, the at least one electronic component pointing in the direction of the printed circuit board carrier,

(c) forming conductor tracks by structuring the conductive carrier foil and contacting the at least one electronic component.

By fixing the at least one electronic component on the insulating layer of the conductive carrier film, the electronic components can be positioned exactly. During the subsequent lamination of the conductive carrier film with the at least one electronic component attached thereto to a printed circuit board carrier, wherein the at least one electronic component points in the direction of the printed circuit board carrier, the at least one electronic component is enclosed by the printed circuit board carrier. As a result, the device is completely encapsulated.

By structuring the conductive carrier film, the necessary conductor tracks are produced in a simple manner. A fast and cost-effective production of the electronic assembly see this is possible.

In a preferred embodiment, the at least one electronic component is enclosed by a polymer compound after being attached to the conductive carrier film. The enclosing of the at least one electronic component with the polymer compound leads to an additional protection of the component. As a result, the risk of damage is significantly reduced even with sensitive components.

The polymer composition with which the at least one electronic component is enclosed is, for example, a low-pressure molding compound, for example an epoxy low-pressure molding compound. The low-pressure molding compound is applied, for example, by a transfer molding process. In addition, placeholders can be kept free in the polymer composition, for example for thicker dielectrics. However, these can also be encapsulated as inserts during encapsulation of the at least one electronic component.

The attachment of the at least one electronic component is preferably carried out by gluing. For this purpose, it is preferred that the conductive carrier film has an adhesive layer. The adhesive layer preferably forms the insulating layer at the same time. The conductive carrier foil is, for example, a self-adhesive conductive carrier foil. The sticking can be done by hot and pressure processes. This is also a hot glue process, for example.

The conductive carrier film used is, for example, a copper foil, also known as printed circuit board RCC material. Other suitable conductive films are, for example, LCP films or FEP films. As a metal is suitable in addition to copper, for example, aluminum.

In a preferred embodiment, before the application of the at least one electronic component to the conductive carrier foil in step (a), alignment marks are introduced into the conductive carrier foil. The Justagemarken are, for example, holes or blind holes with any cross section. These can be introduced, for example, by etching, punching or drilling in the conductive carrier film. The Justagemarken be mounted on the at least one electronic component opposite side of the conductive carrier film. The alignment marks allow the exact position of the at least one electronic component to be determined even after enclosing the at least one electronic component with the polymer mass or after laminating the conductive carrier foil to the printed circuit board carrier. This is necessary for contacting the at least one electronic component. Alternatively, suitable as alignment marks, for example, components that are equipped with the conductive film. At the locations where the devices are located, the conductive foil is preferably drilled or x-rayed to detect the devices. In addition, the Justagemarken may of course also have any other known to the expert form.

Holes are preferably introduced at the positions at which the at least one electronic component is to be electrically contacted with the conductive carrier foil. For contacting the conductive carrier foil with the at least one electronic component, the holes are metallized, for example. The introduction of the holes is done for example by laser drilling. The positions at which the holes are inserted are determined by the adjustment marks.

The metallization of the holes in order to achieve a contact of the electronic component with the conductive carrier film is carried out by methods known in the art. The metallization can be carried out, for example, by electroless metal deposition. Electroless metal deposition is a common process used in printed circuit board manufacturing. The metallization of the holes is preferably carried out with copper.

Further interconnects can be applied, for example, by applying further layers containing interconnects to the conductive carrier film structured in step (c). For this purpose, a dielectric is preferably first applied, by means of which the conductor tracks formed in step (c) are covered. At the same time this results in an isolation of the conductor tracks, so that no unwanted electrical contact with the conductor tracks of the subsequently applied layer takes place. Subsequently, further printed conductors are applied to the dielectric by methods known to the person skilled in the art. The further layers which contain conductor tracks can alternatively also be produced by applying further conductive foils to the first layer and subsequently structuring the foil to form conductor tracks.

In order to dissipate heat arising during operation of the electronic module, it is preferred that the at least one electronic component is contacted with a metal core on the side facing away from the conductive carrier film after laminating the conductive carrier film to the printed circuit board carrier in step (b) the metal core is also integrated in the printed circuit board after being laminated to the printed circuit board carrier. The electronic component then gives off heat to the metal core during operation, via which it can be discharged to the outside.

Advantage of the method according to the invention is that by enclosing the at least one electronic component with the polymer composition or by embedding the electronic component in the printed circuit board carrier a cost-effective encapsulation of passive and active electronic components is achieved. In addition, the electronic assembly is very reliable due to the complete encapsulation of sensitive components. Another advantage of the encapsulation is that this height compensation is possible when different high components are used.

Furthermore, the method according to the invention avoids risky mixing techniques in production, for example soldering, gluing and wire bonding. When using the electronic assembly in the high-frequency technology, that is, when the electronic component is a high-frequency component, reproducible high-frequency transitions are achieved by the planar output structure, which is achieved by the inventive method.

The method according to the invention also makes it possible to integrate any necessary heat sinks on power semiconductors. These can, for example, contact the electronic component on the side facing away from the conductive carrier film. Alternatively, it is also possible for these to be embedded, for example, in the polymer compound with which the at least one electronic component is enclosed.

The inventive method can continue to achieve a cost-effective wiring and encapsulation by the use of processes on many modules simultaneously.

Furthermore, the invention relates to an electronic assembly comprising at least one electronic component which is connected to a printed conductor structure on a printed circuit board, wherein the at least one electronic component is embedded in the printed circuit board and the printed conductor structure is arranged on the surface of the printed circuit board. In addition to the above-mentioned cost-effective encapsulation and thus high reliability, the expensive substrate and packaging technology, as currently used in the prior art, is replaced or reduced to a small component. In addition, it is possible in the inventive electronic assembly to concentrate a complete high-frequency circuit on a module including antennas. The electronic assembly produced according to the invention can be further processed as a standard component.

In a preferred embodiment, the conductor track structure is formed in a plurality of layers. As a result, an increased land use on an electronic circuit board is possible. Due to the additional layers, the electronic module can be equipped and contacted with components in the smallest possible space. In order to be able to dissipate good heat, which arises during operation of the electronic module, it is preferred that in the circuit board, a metal core is contained, which is connected to the at least one electronic component metallically.

In addition to the at least one electronic component, it is also possible for the electronic assembly to contain one or more mechanical components.

Electronic components which are used in the method according to the invention or in the electronic module designed according to the invention are all electronic components known to the person skilled in the art, such as are used in printed circuit board technology and microelectronics. As mechanical components, all components come into consideration, as they are used in printed circuit board technology.

Brief description of the drawings

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

Show it

Figure 1 to 8 several steps of the production of a device according to the invention.

Embodiments of the invention

FIG. 1 shows a conductive carrier foil 1 comprising a conductive layer 3 and an insulating layer 5. The insulating layer 5 is preferably an adhesive layer or a thermoplastic, to which electronic components can be applied. On the side of the conductive carrier film 1, on which the conductive layer 3 is located, adjustment marks 7 are introduced. The alignment marks 7 can be introduced into the conductive carrier film 1, for example by etching, punching, drilling, for example laser drilling. Furthermore, it is possible that the alignment marks are also components connected to the conductive carrier film 1, which are bored free or detected by X-ray microscopy. Any other, known to the expert form for Justagemarken is possible.

The conductive layer 3 is preferably a metal layer. Particularly preferred as the metal is copper. In a second step 5 electronic components 9 are applied to the insulating layer. This is shown in FIG. In addition to electronic components 9, it is also possible for mechanical components to be applied to the insulating layer 5 of the conductive carrier film 1. The electronic components 9 or mechanical components which are applied to the insulating layer 5 of the conductive carrier film 1 are conventional components, as used in printed circuit board construction. These are, for example, chips, processors, high-frequency components, SMD components, antenna modules, heat sinks, MEMS or MOEMS.

The application of the electronic components 9 or mechanical components is preferably carried out by adhering to the insulating layer 5. Here, the electronic components 9 are placed on the insulating layer 5 of the conductive substrate 1, as the electronic components 9 may be later in the electrical circuit should. It can be applied to individual or all electronic components 9 heat sink to ensure increased heat dissipation during operation of the electronic components 9. The optionally providable heat sinks are hereby placed on the side of the electronic components 9, which faces away from the conductive carrier film 1.

In order to achieve encapsulation of sensitive electronic components 9, it is possible to surround them with a polymer compound 11. This is shown in FIG. The polymer composition 11 is, for example, an epoxy low pressure molding compound. For example, placeholders for thicker dielectrics, which are used, for example, for antennas or heat sinks, may be overmolded in the polymer compound 11, if necessary. The wrapping with the polymer compound 11 takes place for example by means of a transfer molding process. The placeholders can be formed for example as depressions or trays. In addition to the transfer molding process, however, any other method known to those skilled in the art can be used with which the electronic components 9 can be encased with the polymer compound 11. In addition, the jacket with the polymer compound 11 has the advantage that a height compensation for components 9 with different thickness is possible. This is advantageous for the subsequent lamination process. Components can also be pre-encapsulated on peelable film and mounted on the carrier film 1 after removing the film.

After the application of the electronic components 9 on the conductive substrate film 1 or, if the electronic components 9 are to be enclosed by the polymer composition, after enclosing the electronic components 9 with the polymer composition 11, the conductive film 1 is cut to PCB blank. After cutting, the conductive foil 1 with the electronic components 9 mounted thereon and, if appropriate, further mechanical components, which are not shown here, are laminated onto a printed circuit board carrier 13. This is shown in FIG. In the embodiment variant shown here, the conductive film 1 with the electronic components 9 has been laminated onto the printed circuit board carrier 13 without the electronic components 9 being enclosed by the polymer compound 11. According to the invention, however, the embodiment shown in FIG. 3, in which the electronic components 9 are enclosed by the polymer compound 11, is also laminated onto the printed circuit board carrier 13. The lamination is carried out according to methods known in the art. According to the invention, the printed circuit board carrier 13 is laminated onto the conductive film 1 in such a way that the electronic components 9 or the electronic components 9 surrounded by the polymer compound 11 are enclosed by the printed circuit board carrier 13. For this purpose, the printed circuit board carrier 13 is laminated on the side on the conductive film 1, on which the electronic components 9 are mounted.

In general, for this purpose, in the case of components 9 whose component thickness is greater than 0.1 mm, first a glass-fiber reinforced and pre-drilled at the points of the components 9 cured printed circuit board material is placed on the film. Then a prepreg and, if appropriate, another cured printed circuit board material is applied. This stack is then pressed in a lamination process. The cured circuit board material is usually a glass fiber reinforced epoxy resin. However, it is also possible to use any other suitable material known to the person skilled in the art. As prepreg, an epoxy resin is also generally used. However, this is not completely cured. By applying pressure and an elevated temperature, the prepreg hardens completely, whereby this connects with the cured printed circuit board material. The composite of prepreg and cured printed circuit board material forms the printed circuit board carrier 13.

After laminating the conductive foil 1 with the electronic components 9 or with the electronic components 9 possibly enclosed by the polymer mass 11 on the printed circuit board carrier 9, holes 17 in the carrier foil 1, comprising the conductive layer 3 and 3, are formed at the connection points of the electronic components 9 the insulating layer 5, introduced. The correct positioning of the holes 17 can be determined by the initially introduced adjustment marks 7. This makes it possible to produce the holes 17 precisely at the positions where the electrical connections of the electronic components 9 are located. Usually, simultaneously with the introduction of the holes 17 for contacting the electronic components 9 with the conductive layer 3 or directly thereafter cooling channels 31, as shown in Figures 7 and 8, drilled in the printed circuit board carrier 13. For this purpose, for example, a laser drilling method is used. If the soldering 17 are also produced by a laser drilling method, a second laser is preferably used for the cooling channels 31. But it can also be drilled holes 17 and cooling channels 31 with the same laser.

By metallization, the electronic components 9 are electrically contacted with the conductive layer 3. This is shown in FIG. For metallization, metal 19 is deposited in the holes 17 by methods known to those skilled in the art, for example by electroless metal deposition. This metal connects the terminals of the electronic components 9 to the printed conductor structure 15. An electronic contact was made. Usually, the metal 19 used for metallization is copper. For the metallization, a starting metallization of palladium is generally first deposited without current. This is followed by a galvanic copper deposition. The metal 19 may take the form of a sleeve or fill the holes 17 completely.

After the introduction of the holes 17 for the contacting of the electronic components 9 in the conductive film 1 and the metallization of the holes 17, the conductive layer 3, as shown in Figure 5, structured. The structuring is carried out by any known to the expert method. Suitable methods are, for example, etching methods, photoresist methods, laser drilling methods or laser ablation methods.

By structuring the conductive layer necessary for the circuit board trace structures 15 are generated.

By embedding the electronic components 9 in the printed circuit board carrier 13, a flat surface is achieved. As a result, a simple processing of the surface is possible lent.

Of course, however, it is also possible first to work out the interconnect structure 15 from the conductive film 1 and subsequently to introduce the holes into the conductive film 1 and to metallize.

FIG. 7 shows an electronic module 21. The electronic assembly comprises two printed circuit boards 23 which are constructed as shown in FIG. On the interconnect structure 15, a dielectric 25 is applied to a further interconnect structure 27th applied. As a dielectric 25 are, for example, epoxy resins or FR4 materials that are known from printed circuit board technology. The application of the dielectric 25 takes place with the usual methods known to the person skilled in the art. For example, it is possible to apply the dielectric 25 by doctoring, brushing, printing, laminating, curtain casting, film coating, spray coating or similar methods.

On the dielectric 25, a further printed conductor structure 27 is applied. For this purpose, it is possible initially to apply a conductive layer over the entire surface, which is subsequently structured.

It is also preferably possible to apply a further conductive film 1 to the first interconnect structure 15 and to pattern the interconnect structure 27 from the conductive layer of the second conductive film. This is then preferably carried out by the same method as the structuring of the conductive layer 3 to the interconnect structure 15. After the formation of the interconnect structure 27 holes 29 can be introduced into the dielectric 25 through which a contacting of the interconnect structure 27 with the interconnect structure 15 by means of metallization.

For producing a plurality of conductive layers patterned into printed conductors, it is particularly preferred to first laminate the dielectric 25 and then a conductive film. After laminating the dielectric 25 and the conductive foil, first holes are made which are then metallized to electrically connect the conductive foil to underlying layers. Subsequently, a further printed conductor structure 27 is worked out of the conductive foil.

In order to remove heat from the electronic components 9, it is possible to introduce cooling channels 31 into the printed circuit board carrier 13 on the side of the electronic components 9 facing away from the printed conductor structures 15, 27. The cooling channels 31 can be connected to a metal core 33. Heat is removed from the electronic components 9 via the metal core 33 and the cooling channels 31. The bonding of the cooling channels 31 to the metal core 33 is generally carried out via a back-side metallization or alternative connections, in which the inner walls of the cooling channels 31 are provided with a metal layer. But it is also possible to completely fill the cooling channels 31 with a metal.

Furthermore, it is also possible to provide cooling elements between the metal core 33 and the electronic components 9. It is also possible to design the metal core 33 such that it directly contacts the electronic components 9. The connection of the printed circuit boards 23 preferably also takes place by means of a laminating process, as is customary in printed circuit board production processes.

With a bore 35, which passes through both circuit boards 23, the conductor track structure 15 of a circuit board 23 can be connected to the conductor track structure 27 of the second circuit board 23. The electrical contact is made, for example, by a metallization of the wall of the bore 35. By means of a bore 37 which terminates on the metal core 33, the conductor track structure 15, 27 can be electrically contacted with the metal core 33. As a result, for example, a ground contact can be realized. Also in the bore 37, the electrical contact is preferably carried out by means of a metallization. The metallization of the bores 35, 37 is produced, for example, by electroless or galvanic metal deposition. Alternatively, it is also possible, for example, to guide a wire through the holes 35, 37.

The embodiment shown in FIG. 8 differs from the embodiment shown in FIG. 7 in that, in the case of a printed circuit board, the electronic components 9 are not encased in the polymer compound 11 and in the case of the second printed circuit board 23 used for the electronic assembly 21 Components 9 are enclosed with the polymer mass 11.

In addition to the embodiments illustrated in FIGS. 7 and 8, in which in each case two printed conductor structures 15, 27 are arranged one above the other, it is also possible that more than two printed conductor structures are provided on one side. It is also possible for a different number of printed conductor structures 25, 27 to be formed on the upper side and the lower side of the electronic module 21.

Claims

claims

A method of manufacturing an electronic assembly (21) comprising a circuit board (23) having at least one electronic component (9), comprising the steps of:

(a) fixing the at least one electronic component (9) on an insulating layer (5) of a conductive film (1), the active side of the electronic component (9) pointing in the direction of the conductive film (1),

(b) laminating the conductive foil (1) with the at least one electronic component (9) attached thereto onto a printed circuit board carrier (13), the at least one electronic component (9) pointing in the direction of the printed circuit board carrier (13),

(c) forming a conductor track structure (13) by patterning the conductive foil (1) and contacting the at least one electronic component (9).

2. The method according to claim 1, characterized in that the at least one electronic component (9) after fixing on the conductive foil (1) by a polymer mass (11) is enclosed.

3. The method according to claim 1 or 2, characterized in that the conductive film (1) has an adhesive layer, wherein the adhesive layer at the same time the insulating

Layer (5) forms.

4. The method according to any one of claims 1 to 3, characterized in that prior to the application of the at least one electronic component (9) on the conductive fo He (1) in step (a) alignment marks (7) in the conductive film (1 ) are introduced.

5. The method according to any one of claims 1 to 4, characterized in that in the conductive film (1) at the positions at which the at least one electronic component (9) is to be electrically contacted with the conductive film (1) holes ( 17) are introduced.

6. The method according to claim 5, characterized in that the holes (17) for contacting the conductive foil (1) with the at least one electronic component (9) are metallized.

7. The method according to any one of claims 1 to 6, characterized in that on the structured in step (c) conductive film (1) further layers, the conductor track structure (27) are applied.

8. The method according to any one of claims 1 to 7, characterized in that the at least one electronic component (9) before the lamination in step (b) on the side facing away from the conductive film (1) side with a metal core (33) is contacted, so that the metal core (33) after the lamination to the printed circuit board carrier (13) is also integrated in the printed circuit board (23).

9. Electronic assembly, comprising at least one electronic component (9) which is connected to a printed conductor structure (15, 27) on a printed circuit board (23), characterized in that the at least one electronic component (9) in a printed circuit board carrier (13) is embedded and the conductor track structure (15, 27) on the surface of the printed circuit board (23) is arranged.

10. Electronic assembly according to claim 9, characterized in that the conductor track structure (15, 27) is formed in a plurality of layers.

11. Electronic assembly according to claim 9 or 10, characterized in that in the circuit board (23) a metal core (33) is included, which is connected to the at least one electronic component (9) metallically.