Patent Description:
In the context of growing product functionalities of component carriers, in particular those equipped with one or more electronic components, and increasing miniaturization as well as a rising demand of functionality of component carriers, increasingly more powerful component carriers are being employed, which have a plurality of contacts or connections, with ever smaller spacing between these contacts. Also an efficient protection against electromagnetic interference (EMI) becomes an increasing issue. At the same time, component carriers shall be mechanically robust and electrically reliable so as to be operable even under harsh conditions. Moreover, an extended functionality of component carriers is demanded by users.

Document <CIT> discloses a component carrier having the features of the pre-characterizing portion of claim <NUM>.

It is an object of the invention to provide a component carrier allowing for an efficient and reliable operation while enabling a high degree of functionality.

In order to achieve the object defined above, a method of manufacturing a component carrier, and a component carrier according to the independent claims are provided.

According to the invention, a component carrier is provided which comprises a plurality of electrically insulating layer structures and a plurality of electrically conductive layer structures, and a non-uniform magnetic foil integrated in the stack.

According to the invention, a method of manufacturing a component carrier is provided, wherein the method comprises connecting a stack of a plurality of electrically conductive layer structures and a plurality of electrically insulating layer structures, and non-uniformly integrating a (in particular connected, at least at the time of integration) magnetic foil in the stack.

In the context of the present application, the term "non-uniform magnetic foil" may particularly denote a layer, film or sheet consisting of or comprising magnetic material deviating from a purely continuous planar shape. Such a non-uniform magnetic foil may for instance be a magnetic foil having one or more interior and/or exterior recesses (such as through holes and/or blind holes) and/or being three dimensionally bent (i.e. being not fully located within one plane). A non-uniform magnetic foil may constitute one common or connected integral structure or may be composed of multiple separate no longer connected islands (which may have been separated on the basis of an initially continuous foil).

In the context of the present application, the term "integrated in the stack" may particularly denote that the non-uniform magnetic foil may be arranged partially or entirely embedded within an interior of a connected (in particular laminated) stack of component carrier material, in particular PCB (printed circuit board) material.

According to an exemplary embodiment of the invention, a magnetic foil is embedded in a stack of electrically insulating layer structures (for instance comprising a resin, optionally in combination with reinforcing particles such as fibers) and/or electrically conductive layer structures (for instance copper foils) in a way that the magnetic foil is arranged in and/or on a corresponding stack in a spatially non-uniform manner. Implementing such an embedding process has the advantageous effect that the magnetic foil is securely connected within and protected by the component carrier material, thereby providing high mechanical stability. Simultaneously and synergistically, the non-uniform shape of the magnetic foil allows tailoring the magnetic foil in accordance with a specific magnetic and/or electric function or electromagnetic radiation shielding function in the component carrier. For instance, the non-uniform magnetic foil may at least partially surround an electromagnetic radiation emitting and/or electromagnetic radiation sensitive component embedded in the component carrier to reduce or even eliminate issues concerning electromagnetic interference (EMI). It is also possible that the non-uniform magnetic foil forms part of an inductor, for instance constitutes a ferrite core cooperating with a coil integrated in a component carrier. Thus, the non-uniform magnetic foil may form part of an inductor embedded in the component carrier. The non-uniform design of the magnetic foil in the component carrier may also be adjusted under consideration of other boundary conditions, such as the need to form vertical interconnects in an interior of the component carrier protruding through the magnetic foil without forming parasitic electrically conductive paths.

In the following, further exemplary embodiments of the method and the component carrier will be explained.

In an embodiment, the non-uniform magnetic foil is a patterned magnetic foil. Such patterning can be carried out advantageously using a mechanical abrasion technique, since removing portions of a (in particular previously continuous) magnetic foil by mechanically processing the foil (for instance by milling or drilling) is compatible with substantially any material of the magnetic foil (in contrast to a patterning based on photolithography and etching, which is for instance not possible with magnetic oxide type magnetic foils or magnetic foils being provided as a polymer matrix with magnetic particles, for instance of ferrite, embedded therein). By patterning, portions of the magnetic foil may be removed in which it is desired that the magnetic foil is not present for a certain application. For instance, such portions being free of magnetic material may be advantageous where electrically conductive vertical connection elements are formed which shall not be in contact with the magnetic foil.

Additionally or alternatively, the magnetic foil may be a three-dimensionally bent foil. By three-dimensionally bending the magnetic foil for establishing a non-uniform property thereof, spatial regions and/or spatial directions in which the magnetic foil is functionally operative can be precisely adjusted. For instance, a three-dimensionally bent magnetic foil having a slanted or vertical transition section between two horizontal sections may allow providing a lateral electromagnetic radiation shielding function.

In an embodiment, the magnetic foil is configured as a single continuous magnetic foil structure. The formation of the magnetic foil as an integrally connected structure simplifies handling of the magnetic foil which can simply be treated as one piece during the manufacturing process. This property is also advantageous during the embedding (for instance laminating) process, since the connected magnetic foil does not comprise multiple separate islands which need to be handled separately or which tend to spatially migrate into unintentional regions, thereby deteriorating spatial accuracy.

More specifically, the magnetic foil may be provided as a single continuous magnetic foil structure at least at the beginning of the manufacturing process. In such an embodiment, the magnetic foil can be laminated as a sheet together with other layer structures (such as prepreg layers and copper foils), for instance all having the same sheet dimension. This is easily possible using standard PCB technology. Patterning may be accomplished after pressing such as single continuous magnetic foil together with the other layer structures. Thus, registration accuracy may be significantly increased compared to an approach in which individual small pieces of magnetic material are embedded in larger panels of prepreg and copper.

According to the invention, the magnetic foil is configured as an arrangement of multiple separate island structures in the readily manufactured component carrier. By taking this measure, also very specific and/or spatially limited magnetic tasks may be fulfilled by the magnetic foil without limiting the freedom of design of other portions of a component carrier. In particular in such an embodiment, it may be highly advantageous to first embed a continuous complete magnetic foil with other layer structures to form an interconnected stack, and to form the separate magnetic islands later, in order to obtain high registration accuracy.

According to the invention, the magnetic foil comprises a polymer matrix and magnetic particles, in particular ferrite particles, embedded in the polymer matrix. Alternatively, the magnetic foil comprises a magnetic oxide (for instance ferric oxide, magnetite, etc.) material. A magnetic foil formed on the basis of a polymer matrix and magnetic particles has the significant advantage of being freely bendable so that the non-uniformity of the embedded magnetic foil can be freely adjusted. Moreover, when processing such a polymer matrix with embedded magnetic particles, for instance in terms of patterning the corresponding magnetic foil, it is highly advantageous to use a mechanical abrasion procedure (such as milling) or laser processes, since such a material is not compatible with etching. Similar considerations apply for magnetic oxide materials.

In an embodiment, the component carrier further comprises at least one (in particular vertical) through-connection extending through at least part of the stack and the magnetic foil. In particular, the (in particular vertical) through-connection may be separated from the magnetic foil by material of the electrically insulating layer structures (such as resin, in particular epoxy resin, with reinforcing particles, in particular glass fibers, for instance prepreg or FR4). Correspondingly, the method may comprise forming at least one electrically conductive through-connection extending through at least part of the stack and the magnetic foil. Advantageously, the (preferably vertical) through-connection may be separated from the magnetic foil by material of at least one of the electrically insulating layer structures. When the magnetic foil is provided with a through hole, a vertical through-connection (such as a copper via) may be guided through this through hole to accomplish an electric coupling between electrically conductive structures or components above and below the magnetic foil without generating undesired electric paths. Thus, the presence of the embedded magnetic foil can made compatible with electric boundary conditions in the component carrier.

In an embodiment, the magnetic foil comprises at least one the group consisting of a permanent magnetic material, a soft magnetic material, and a ferrite material. A permanent magnetic material may be ferromagnetic material or ferrimagnetic material, and may for instance be provided on the basis of transition metals (with partially filled 3d shell) such as iron or nickel, or on the basis of rare earths (with partially filled 4f shell). A soft magnetic material may be a material which can be easily re-magnetized, i.e. having a small area of its hysteresis curve. In other words, soft magnetic materials are those materials that are easily magnetized and demagnetized. They may have intrinsic coercivity less than <NUM> Am-<NUM>. A ferrite may be denoted as a type of ceramic compound composed of Fe<NUM>O<NUM> combined chemically with one or more additional metallic elements. Ferrites are both electrically non-conductive and ferrimagnetic, so they can be magnetized or attracted by a magnet. Ferrites may be implemented as hard ferrites or soft ferrites, depending on an application.

In an embodiment, the magnetic material of the magnetic foil has a relative magnetic permeability, µr, of at least <NUM>, in particular at least <NUM>. Magnetic permeability may be denoted as a measure of the ability of a material to support the formation of a magnetic field within itself. Hence, it is the degree of magnetization that a material obtains in response to an applied magnetic field.

In an embodiment, the magnetic foil is sandwiched between a first portion of the stack and a second portion of the stack. By taking this measure, the magnetic foil is properly protected against influences from the environment. Moreover, by locating the magnetic foil in an interior of the stack rather that at a surface thereof, the magnetic foil can fulfil its function directly at a desired location, thereby contributing to the compactness of the component carrier as a whole.

In an embodiment, the magnetic foil is configured for shielding electromagnetic radiation from propagating within the component carrier or within the stack (for instance from a first portion of the stack to a second portion of the stack). The magnetic foil may however also be configured for shielding electromagnetic radiation from propagating between component carrier and an environment. Such a shielding may include a prevention of electromagnetic radiation from propagating from an exterior of the component carrier to an interior of the component carrier, from an interior of the component carrier to an exterior of the component carrier, and/or between different portions of the component carrier. In particular, such a shielding may be accomplished in a lateral direction of the stack (i.e. horizontally) and/or in a stacking direction of the stack (i.e. vertically). In such an embodiment, the magnetic foil may function for shielding electromagnetic radiation to thereby suppress undesired effects of electromagnetic interference (EMI), in particular in the radiofrequency (RF) regime. For instance, an embedded component of the component carrier arranged in the first portion of the stack may be a source of electromagnetic radiation to be shielded in order to prevent or at least suppress propagation of the electromagnetic radiation to the second portion of the stack (where for instance a radiation sensitive further embedded component may be located). It is also possible that electromagnetic radiation, such as radio frequency radiation, propagates into the stack and shall be prevented from reaching a radiation sensitive portion of the stack (for instance a component embedded therein).

In another embodiment, the component carrier comprises an inductor (for instance an embedded inductor), wherein the magnetic foil forms part of the inductor (in particular forms at least part of a core of the inductor). For instance, a ferromagnetic core inductor (such as an iron core inductor) may use a magnetic core made of a ferromagnetic or ferrimagnetic material such as iron or ferrite to increase the inductance. Thus, at least part of the non-uniform magnetic foil may form part of a magnetic core of an inductor, for instance for manufacturing a transformer or the like. Embedding the magnetic foil in (in particular an interior of) the stack also allows forming an embedded inductor in which the magnetic foil or part thereof forms a (for instance ferrite) core of the inductor.

In an embodiment, the magnetic foil is rendered non-uniform by removing material of the magnetic foil by mechanical abrasion (for instance by milling, drilling, grinding, etc.) or laser cutting. Several in particular bendable magnetic foils, which are highly appropriate as non-uniform magnetic foils, cannot be appropriately patterned by etching. An example is a flexible film composed of a polymer matrix with magnetic particles (for example ferrite particles) therein. However, it turned out that also such kind of foil-type magnetic materials can be patterned (for instance for forming one or more through holes and/or blind holes and/or for separating the magnetic foil into multiple separate magnetic islands) properly by a subtractive procedure which is based on a mechanical impact on the magnetic foil removing material thereof. Thus, patterning a magnetic foil by mechanically processing is a powerful tool for freely designing non-uniform magnetic foils in terms of shape adjustment, adjusting patterning properties and in terms of material selection.

In a preferred embodiment, the magnetic foil is rendered non-uniform by milling a (in particular previously continuous) foil, in particular by one of depth milling and contact milling.

In the context of the present application, the term "milling" may in particular denote a machining process of using a milling tool having one or more rotary cutters to remove material from the stack as workpiece by advancing the milling tool in a direction at an angle with the axis of the milling tool.

More specifically, the term "depth milling" may particularly denote a milling process in which the depth of the milling of the component carrier or preform thereof is controlled by controlling a milling tool in a vertical direction perpendicular to a main surface of the component carrier being manufactured. Depth milling may involve a control unit controlling depth of etching in the vertical or z-direction.

Beyond this, the term "depth milling" may particularly denote a milling process in which a mechanical contact between a bottom of a milling tool (in particular a rotary cutter) and a stop layer of the stack at which the milling procedure shall be terminated can be detected electrically, and the milling tool can be controlled in accordance with the electric detection. In such a depth milling process, the event of the (in particular electrically conductive) tip of the milling tool touching the (in particular electrically conductive) stop layer of the stack (for instance a copper foil of the stack below the magnetic foil) can be detected electrically by providing an electric circuit which is closed by the milling tool upon touching the stop layer. Thus, an electric signal indicative of the completion of the milling procedure in the vertical direction may prevent undesired excessive milling and thereby allows manufacturing a component carrier with highly accurate properties.

In an embodiment, the magnetic foil is rendered non-uniform by laser processing a (in particular previously continuous) foil, in particular by laser drilling. Thus, it is possible to pattern the magnetic foil by a laser treatment with high speed. In an embodiment, the method comprises processing the magnetic foil by arranging part of the magnetic foil on or above a release structure, forming an annular through-hole through the magnetic foil extending at least up to the release structure, and removing a portion of the magnetic foil within the annular through-hole. Such a release layer may a patterned layer structure (for instance made of a waxy material or based on Teflon) on which other component carrier material of the stack, including the magnetic foil, does not properly adhere. Cutting a circumferentially closed hole above such a release layer may therefore allow taking out a piece of the magnetic foil above the release layer to thereby complete formation of the patterned magnetic foil.

In an embodiment, the method comprises forming the annular through-hole by one of the group consisting of mechanically cutting and laser cutting. Such a process may be easily controlled and allows manufacturing structured magnetic foils with high freedom of design.

In an embodiment, the method comprises processing the magnetic foil by providing a first body and a (for instance laterally juxtaposed or laterally overlapping or even to be vertically stacked) second body comprising component carrier material (for instance each comprising at least one electrically insulating layer structure and/or at least one electrically conductive layer structure), and guiding the magnetic foil along one of the bodies, through a gap between the bodies up to the other of the bodies to thereby three-dimensionally bend the magnetic foil. The first body and the second body may for instance be separate bodies or may be portions of a common body being delimited by a gap (such as a slit). In such embodiments, the shape of the three-dimensional bending can be defined by the shape of the two cooperating component carrier bodies along which the magnetic foil can be precisely guided. At the gap between the bodies, the foil may be also arranged slanted or even vertical so that even a lateral shielding of electromagnetic radiation can be made possible.

In an embodiment, the first body and the second body are each formed with a respective one of two cooperating surface profiles. The magnetic foil may be guided along both surface profiles so as to be three-dimensionally bent. For instance, the surface profiles may be cooperating steps of the bodies. The surface profiles of the bodies may be shaped and dimensioned so that they can be connected to one another with form closure. Descriptively speaking, the surface profiles of the bodies may be formed like cooperating puzzle pieces. By providing such cooperating surface profiles, the accuracy of guiding the (in particular flexible, elastic and/or bendable) magnetic foil along a defined trajectory in an interior of the formed component carrier may be further improved. The freedom of implementing one or more additional magnetic functions in the component carrier may therefore be increased.

In an embodiment, the first body and the second body together form the stack when assembled. In particular, the first body and the second body may be adapted so as to form a plate-like structure when assembled. When taken individually, the first body in the second body may each form plate-like structures as well, or may form structures with cooperating surface profiles which constitute the plate-like structure only upon assembly.

In an embodiment, the method further comprises laminating the magnetic foil on a first portion of the stack and subsequently laminating a second portion of the stack on the first portion of the stack and on the magnetic foil. Thus, the magnetic foil may be first laminated on layer structures forming part of the stack, preferably as a continuous magnetic foil. The magnetic foil, still being exposed, may then be processed (in particular by a mechanical abrasive method such as milling or laser processes) to render it non-uniform in accordance with a desired magnetic application. Thereafter, the so obtained structure may be laminated together with further layer structures of the stack, so that the magnetic foil may be embedded in an interior of the readily formed component carrier.

In an embodiment, the method further comprises connecting the magnetic foil on at least one of the layer structures, and subsequently removing part of the material of the magnetic foil. This order of processing makes it possible to connect the magnetic foil in form of a sheet having the same size as sheets constituting the electrically conductive layer structures and electrically insulating layer structures of the stack. For instance, the sheets may have panel size (for instance <NUM> inch x <NUM> inch). When such sheets are laminated together, no alignment or registration issues occur. By only subsequently patterning the already laminated magnetic foil, even tiny magnetic structures may be formed precisely located at desired target positions on the stack. By patterning using a mechanical abrasion method substantially all types of magnetic materials may be precisely processed.

According to the invention, removing part of the material of the magnetic foil comprises separating the magnetic foil into separate islands. Thus, the magnetic foil not necessarily forms a continuous structure in the final component carrier, but can be composed of several discontinuous substructures or islands which may for instance be all located in the same plane.

In an embodiment, the method comprises providing a magnetic foil being flexibly bendable prior to integrating the magnetic foil in the stack. Such a bendable foil may be an elastically bendable foil and/or a plastically deformable foil.

At least one component may be surface mounted on or embedded in the component carrier. The at least one component can be selected from a group consisting of an electrically non-conductive inlay, an electrically conductive inlay (such as a metal inlay, preferably comprising copper or aluminum), a heat transfer unit (for example a heat pipe), a light guiding element (for example an optical waveguide or a light conductor connection), an electronic component, or combinations thereof. For example, the component can be an active electronic component, a passive electronic component, an electronic chip, a storage device (for instance a DRAM or another data memory), a filter, an integrated circuit, a signal processing component, a power management component, an optoelectronic interface element, a voltage converter (for example a DC/DC converter or an AC/DC converter), a cryptographic component, a transmitter and/or receiver, an electromechanical transducer, a sensor, an actuator, a microelectromechanical system (MEMS), a microprocessor, a capacitor, a resistor, an inductance, a battery, a switch, a camera, an antenna structure, a logic chip, a light guide, and an energy harvesting unit. However, other components may be embedded in the component carrier. For example, a magnetic element can be used as a component. Such a magnetic element may be a permanent magnetic element (such as a ferromagnetic element, an antiferromagnetic element or a ferrimagnetic element, for instance a ferrite coupling structure) or may be a paramagnetic element. However, the component may also be a further component carrier, for example in a board-in-board configuration. The component may be surface mounted on the component carrier and/or may be embedded in an interior thereof. Moreover, also other components may be used as component.

In an embodiment, the component carrier comprises a stack of at least one electrically insulating layer structure and at least one electrically conductive layer structure. For example, the component carrier may be a laminate of the mentioned electrically insulating layer structure(s) and electrically conductive layer structure(s), in particular formed by applying mechanical pressure, if desired supported by thermal energy. The mentioned stack may provide a plate-shaped component carrier capable of providing a large mounting surface for further components and being nevertheless very thin and compact. The term "layer structure" may particularly denote a continuous layer, a patterned layer or a plurality of non-consecutive islands within a common plane.

In an embodiment, the component carrier is configured as one of the group consisting of a printed circuit board, and a substrate (in particular an IC substrate).

In the context of the present application, the term "printed circuit board" (PCB) may particularly denote a component carrier (which may be plate-shaped (i.e. planar), three-dimensionally curved (for instance when manufactured using 3D printing) or which may have any other shape) which is formed by laminating several electrically conductive layer structures with several electrically insulating layer structures, for instance by applying pressure, if desired accompanied by the supply of thermal energy. As preferred materials for PCB technology, the electrically conductive layer structures are made of copper, whereas the electrically insulating layer structures may comprise resin and/or glass fibers, so-called prepreg or FR4 material. The various electrically conductive layer structures may be connected to one another in a desired way by forming through-holes through the laminate, for instance by laser drilling or mechanical drilling, and by filling them with electrically conductive material (in particular copper), thereby forming vias as through-hole connections. Apart from one or more components which may be embedded in a printed circuit board, a printed circuit board is usually configured for accommodating one or more components on one or both opposing surfaces of the plate-shaped printed circuit board. They may be connected to the respective main surface by soldering. A dielectric part of a PCB may be composed of resin with reinforcing fibers (such as glass fibers).

In the context of the present application, the term "substrate" may particularly denote a small component carrier having substantially the same size as a component (in particular an electronic component) to be mounted thereon. More specifically, a substrate can be understood as a carrier for electrical connections or electrical networks as well as component carrier comparable to a printed circuit board (PCB), however with a considerably higher density of laterally and/or vertically arranged connections. Lateral connections are for example conductive paths, whereas vertical connections may be for example drill holes. These lateral and/or vertical connections are arranged within the substrate and can be used to provide electrical and/or mechanical connections of housed components or unhoused components (such as bare dies), particularly of IC chips, with a printed circuit board or intermediate printed circuit board. Thus, the term "substrate" also includes "IC substrates". A dielectric part of a substrate may be composed of resin with reinforcing spheres (such as glass spheres).

In an embodiment, the at least one electrically insulating layer structure comprises at least one of the group consisting of resin (such as reinforced or non-reinforced resins, for instance epoxy resin or Bismaleimide-Triazine resin, more specifically FR-<NUM> or FR-<NUM>), cyanate ester, polyphenylene derivate, glass (in particular glass fibers, multi-layer glass, glass-like materials), prepreg material, polyimide, polyamide, liquid crystal polymer (LCP), epoxy-based Build-Up Film, polytetrafluoroethylene (Teflon), a ceramic, and a metal oxide. Reinforcing materials such as webs, fibers or spheres, for example made of glass (multilayer glass) may be used as well. Although prepreg or FR4 are usually preferred, other materials may be used as well. For high frequency applications, high-frequency materials such as polytetrafluoroethylene, liquid crystal polymer and/or cyanate ester resins may be implemented in the component carrier as electrically insulating layer structure.

In an embodiment, the at least one electrically conductive layer structure comprises at least one of the group consisting of copper, aluminum, nickel, silver, gold, palladium, and tungsten. Although copper is usually preferred, other materials or coated versions thereof are possible as well, in particular coated with supra-conductive material such as graphene.

In an embodiment, the component carrier is a laminate-type body. In such an embodiment, the component carrier is a compound of multiple layer structures which are stacked and connected together by applying a pressing force, if desired accompanied by heat.

According to an exemplary embodiment of the invention, one or more (in particular integral or connected, or separated into separate islands) magnetic layers are embedded in a component carrier in such a way that the one or more magnetic layers have a non-uniform shape or structure.

It is been found that magnetic foils (such as ferrite foils, soft magnetic foils, foils on the basis of nano-crystalline magnetic materials, etc.) have proper adhesion properties in relation to component carrier material, in particular resin sheets such as prepreg. At the same time, such magnetic foils meet even challenging reliability requirements of component carriers.

When embedding such magnetic foils in a component carrier material, it may be required to cut out certain structures and to locate a non-uniform magnetic foil at a correct position within a panel as a preform of component carriers such as printed circuit boards (PCB). This is required in order to find the correct position of the magnetic foil or parts thereof in the interior of the panel later.

In order to make this possible, the position of the magnetic foil on a carrier may be defined, and the magnetic foil may be subsequently patterned by a subtractive method until only the desired structure of the non-uniform magnetic foil remains.

For instance, a corresponding manufacturing method may involve the following procedures:.

During processing the magnetic foil in terms of the manufacturing process of an exemplary embodiment of the invention, it is possible to form one or more fiducials, alignment markers or registration markers. When needed, they can be found by X-ray drilling and can be used for the further patterning and other manufacturing processes. In case of an insufficient filling of the structures, it is possible to remove copper by etching after the second pressing or lamination process, and press or laminate the composite again. In an embodiment, in which very thin compounds shall be manufactured, it is possible to implement one or more RCC foils in combination with contact milling. For instance, it is possible to use a thicker (for instance <NUM> or more) copper foil in combination with a thinner (for instance less than <NUM>) further copper foil and in combination with an adhesive foil (for example a UV release adhesive foil). It should be emphasized that, in such an embodiment, a connected carrier layer may remain under the magnetic foil (for instance ferrite structure) after milling, which can be removed again after the second lamination or pressing procedure. Also in such a scenario, it is possible to subsequently etch copper material and repeat the pressing or lamination procedure (for instance if an upper resin layer is not sufficient for filling). Additionally or alternatively, it is also possible that copper is applied again, for instance by a deposition process (for instance chemically and/or galvanically or sputtering in any combinations).

In yet another exemplary embodiment, it is possible to implement a buried release layer or structure (for instance made of a waxy component or based on Teflon) beneath the magnetic foil. Since such a release layer is made of material having an intentionally poor adhesion with regard to the magnetic material of the magnetic foil, cutting a circumferential through hole through the magnetic foil and extending up to the release layer allows to subsequently take out a piece of the magnetic foil above the release layer, to thereby obtain a patterned non-uniform magnetic foil. Thus, in such an embodiment, it is sufficient to mill a certain circumference of the magnetic foil (for instance a ferrite structure), and to subsequently release and remove the separated piece of the magnetic foil.

Connected non-uniform magnetic foils (for instance ferrite layers) formed in this way may be used for manufacturing an inductance or a shielding for shielding disturbing electromagnetic signals between conductive traces of the component carrier (in particular interlayer as well as lateral traces).

In a nutshell, an exemplary embodiment introduces a subtractive method of processing a magnetic layer on a carrier for the manufacture of a component carrier with an embedded non-uniform magnetic foil. With such an architecture, it is possible to also form non-continuous (i.e. separate) magnetic structures in a component carrier such as a printed circuit board. Due to the described embodiment of the manufacturing method, in which the magnetic foil is first connected with the stack by laminating and is patterned later, no issues concerning positioning and registration of the various structures occur. For instance, this allows embedding one or more magnetic layers in a component carrier for shielding purposes and/or for the manufacture of embedded inductors. Corresponding component carriers may also be manufactured in a highly compact way.

<FIG> illustrate cross-sectional views of structures obtained during manufacturing a component carrier <NUM>, shown in <FIG>, according to an exemplary embodiment of the invention.

Referring to <FIG>, still separate constituents of a stack <NUM> to be formed are shown. These constituents comprise an electrically conductive layer structure <NUM> (here embodied as a copper foil), an electrically insulating layer structure <NUM> (here embodied as a resin or prepreg foil) and a magnetic foil <NUM>. In the shown embodiment, the magnetic foil <NUM> may be made of ferrite, µ-metal, or may be a foil composed of a non-magnetic polymer matrix with magnetic particles (for instance ferrite particles) therein. The latter mentioned composite foil has the advantage of being properly bendable and having appropriate properties for being integrated in a component carrier <NUM>. For instance in order to provide a proper shielding function against electromagnetic radiation in the high-frequency regime, the magnetic material of the magnetic foil <NUM> may have a relative magnetic permeability µr of for instance <NUM> to <NUM>, up to <NUM>,<NUM> or even <NUM>,<NUM> or more. The magnetic material may have soft magnetic or ferrite-like properties. All layers shown in <FIG> (see reference numerals <NUM>, <NUM>, <NUM>) may be of panel size.

In order to obtain the structure shown in <FIG>, the individual layers shown in <FIG> may be connected by lamination, i.e., by applying mechanical pressure and/or heat. Thereby, a first portion <NUM> of connected stack <NUM> composed of the electrically conductive layer structure <NUM>, the electrically insulating layer structure <NUM>, and the magnetic foil <NUM> is obtained. The magnetic foil <NUM> may be bendable in its configuration according to <FIG> prior to integrating the magnetic foil <NUM> in the stack <NUM>. The stack <NUM> may be flexible or rigid depending on the materials that have been employed and/or on the build-up end thickness. By lamination, previously at least partially uncured material of the electrically insulating layer structure <NUM> has been cured and thereby passive to be hardened, so that the first portion <NUM> of the stack <NUM> may be provided with some rigidity. In case of the lamination with a layer of liquid crystal polymer (LCP) or Polyimide, the construct or stack <NUM> is passive to remain flexible and to be used as a flexible PCB.

Referring to <FIG>, the (here still continuous) magnetic surface layer of the stack <NUM> as well as a portion of the underlying electrically insulating layer structure <NUM> undergo a depth milling treatment using a milling tool <NUM>. The milling tool <NUM> is capable of rotating, see arrow <NUM>, and can be moved along a controllable (in particular two-dimensional or three-dimensional) path (see reference numeral <NUM>) under control of a control unit such as a processor (not shown). In other words, the magnetic foil <NUM> is patterned by depth milling to thereby manufacture a non-uniform magnetic foil <NUM> by removing material of the magnetic foil <NUM> by mechanical abrasion.

The patterning of the magnetic material can be also done simply by drilling the stack <NUM> with through holes instead of depth milling, or in combination with depth drilling. This process is not shown in the figures but it can be easily understood from the considerations of <FIG> and is not be displayed in the figures. The drilled holes in the stack <NUM> are afterwards filled in with epoxy resin, and there will be a situation similar to <FIG>. After this process, the stack <NUM> may be drilled again exactly on the cleared spaces on the magnetic material with a smaller driller diameter (see reference numeral <NUM>). Such through-holes can be plated with a galvanic copper processes. Such a process may be called via-in-via.

The described patterning procedure may be carried out in a way to maintain an integral connected magnetic foil <NUM> having through holes in an interior thereof and at a lateral edge thereof. It is however alternatively also possible to remove part of the material of the magnetic foil <NUM> by depth milling to thereby separate the magnetic foil <NUM> into multiple separate islands. In both alternatives, there are no issues in terms of registration accuracy, since the magnetic foil <NUM> has been connected as a complete layer with the layer structures <NUM>, <NUM> and has only been rendered non-uniform by patterning later.

Advantageously, the patterning of the magnetic foil <NUM> by depth milling may also allow simultaneously forming one or more alignment markers (see reference numeral <NUM> in <FIG>) of magnetic material of the magnetic foil <NUM>. The definition of the patterned portions of the magnetic foil <NUM> for a magnetic task and the definition of such alignment markers <NUM> in a common mechanical abrasion process has the specific advantage of further increasing the positional accuracy of the manufactured component carrier <NUM> and its constituents relative to one another.

In another embodiment, a pre-perforated magnetic foil <NUM> may be laminated on layer structures <NUM>, <NUM>, which may already comprise a registration marker.

Referring to <FIG>, a structure is shown which is obtained after completion of the depth milling procedure. The depth milling procedure may remove magnetic material from the magnetic foil <NUM> specifically in sections where magnetic material is not desired for the functionality of the component carrier <NUM>.

Referring to <FIG>, the first portion <NUM> of the stack <NUM> as shown in <FIG> and further constituents of a second portion <NUM> of the stack <NUM> are shown. These further constituents comprise a further electrically conductive layer structure <NUM> (here embodied as a copper foil), and a further electrically insulating layer structure <NUM> (here embodied as a resin or prepreg foil).

Referring to <FIG>, the mentioned constituents of the second stack <NUM> are laminated on the first portion of the stack <NUM> with the magnetic foil <NUM> in between. More specifically, this lamination procedure is carried out so that the further electrically insulating layer structure <NUM> is connected with the patterned magnetic foil <NUM> as well as with exposed portions of electrically insulating layer structure <NUM> of the first portion <NUM>. Lamination may be accomplished by applying mechanical pressure and/or heat. By lamination, previously at least partially uncured material of the further electrically insulating layer structure <NUM> is cured.

As a result of this manufacturing process, the plate-shaped lamination-type component carrier <NUM> (which is here embodied as a printed circuit board, PCB) as shown in <FIG> is obtained. The component carrier <NUM> comprises the stack <NUM> composed of the plurality of electrically insulating layer structures <NUM> and the plurality of electrically conductive layer structures <NUM> as well as of the patterned and thus non-uniform magnetic foil <NUM> integrated in the stack <NUM>. Due to the two lamination procedures, the magnetic foil <NUM> is securely sandwiched between the lower first portion <NUM> of the stack <NUM> and the upper second portion <NUM> of the stack <NUM>.

Depending on the processing of the magnetic foil <NUM>, the component carrier <NUM> may have an integrated magnetic function, for instance an electromagnetic radiation shielding function, an inductor function, a magnetic core function, etc..

As indicated schematically by reference numeral <NUM> in <FIG>, it is possible to form one or more through holes extending between two opposing main surfaces of the component carrier <NUM> (and/or to form one or more blind holes extending from one of the two opposing main surfaces of the component carrier <NUM>). Such through holes (and/or blind holes) may extend through the patterned magnetic foil <NUM> so as to be electrically decoupled therefrom. By laterally spacing the holes <NUM> with regard to the magnetic foil <NUM>, a reliable electric decoupling may be ensured so that the electric contacting between the individual layers is not deteriorated by the presence of the magnetic foil <NUM>. It is then possible to at least partially fill such through holes and/or blind holes with electrically conductive material (for instance by copper material which may be deposited by plating, electroless deposition, galvanically, etc.) to provide vertical through-connections (see reference numeral <NUM> in <FIG>) for interconnecting electrically conductive layer structures <NUM>, embedded components (see reference numeral <NUM> in <FIG>), etc., of the component carrier <NUM>. The mentioned holes <NUM> can be formed by drilling (for instance mechanical drilling, laser drilling, etc.).

<FIG> illustrates a plan view of a component carrier <NUM> according to an exemplary embodiment of the invention. In the component carrier <NUM> according to <FIG>, a non-uniform magnetic foil <NUM> is shown which is composed of five separate islands, i.e. one central electromagnetic radiation shielding structure <NUM> having several holes <NUM>, and four alignment markers <NUM> of magnetic material formed in corner regions of component carrier <NUM> and simultaneously formed from the same magnetic foil <NUM> as the central electromagnetic radiation shielding structure <NUM>.

Referring to <FIG>, an RCC foil <NUM> (resin coated copper) is arranged beneath a magnetic foil <NUM>. The RCC foil <NUM> is composed of an electrically conductive layer structure <NUM> (here embodied as a copper foil) which is already covered on a main surface thereof with a resin layer as electrically insulating layer structure <NUM>. The resin layer is still uncured, and will be cured later during lamination.

In order to obtain the structure shown in <FIG>, the constituents of the stack <NUM> shown in <FIG> are interconnected by lamination, i.e. the application of pressure and/or heat, thereby curing further electrically insulating layer structure <NUM>. As a result, the integral first portion <NUM> of the layer stack <NUM> shown in <FIG> is obtained.

Referring to <FIG>, the first portion <NUM> of the layer stack <NUM> is patterned by contact milling, wherein electrically conductive layer structure <NUM> serves as a stop layer of the milling procedure. As can be taken from <FIG>, an electric circuit <NUM> is provided which allows an electric current flow only when a tip of electrically conductive milling tool <NUM> contacts electrically conductive layer structure <NUM>, which can be detected by an electric detection unit <NUM> (such as an amperemeter or a capacitance bridge). In the event of signal detection, the milling procedure may either be terminated, or the milling tool <NUM> may be raised to prevent milling of electrically conductive layer structure <NUM>. Thereby, it can be precisely ensured that the electrically conductive layer structure <NUM> is not damaged by the milling of the magnetic foil <NUM> (and optionally of the underlying electrically insulating layer structure <NUM>). Thus, a highly advantageous depth control may be obtained by the milling procedure according to <FIG>. As a consequence, the readily manufactured component carrier <NUM> has precisely defined properties and has a high mechanical and electrical reliability.

<FIG> shows a structure obtained when the milling procedure is completed and the magnetic foil <NUM> is patterned in accordance with a desired magnetic application, so that non-uniformity of the magnetic foil <NUM> has been established.

Referring to <FIG>, the first portion <NUM> of the stack <NUM> as shown in <FIG> and a constituent of the second portion <NUM> of the stack <NUM> are shown. This constituent comprises a further RCC (resin coated copper) foil <NUM> composed of a further electrically conductive layer structure <NUM> (here embodied as a copper foil), and a further electrically insulating layer structure <NUM> (here embodied as a still uncured resin layer).

Referring to <FIG>, the mentioned constituent of the second stack <NUM> is laminated on the first portion of the stack <NUM> with the magnetic foil <NUM> on an exposed surface thereof. More specifically, this lamination procedure is carried out so that the further electrically insulating layer structure <NUM> is connected with the patterned magnetic foil <NUM> as well as with exposed portions of electrically insulating layer structure <NUM> of the first portion <NUM>. Lamination may be accomplished by applying mechanical pressure and/or heat. By lamination, the previously at least partially uncured material of the further electrically insulating layer structure <NUM> has been cured.

Referring to <FIG>, the magnetic foil <NUM> is arranged above several portions of a release structure <NUM> which are sandwiched between electrically conductive layer structure <NUM> (for instance a copper foil) and electrically insulating layer structure <NUM> (for instance a resin foil or a prepreg foil) on a bottom side and the magnetic foil <NUM> on a top side. For instance, the release structure <NUM> may be a patterned layer with non-adhesive properties with regard to the material of the constituents with reference numerals <NUM>, <NUM>. Such a release structure <NUM> may for instance be a waxy component (which may be based on calcium stearate) or Teflon based material which can be applied in the form of a paste, for instance by screen printing. The release structure <NUM> may have the property to be non-adhesive with regard to both magnetic foil <NUM> and component carrier materials, in particular copper, epoxy resin, reinforcing glass fibers, etc. The order between structures <NUM> and <NUM> may be changed before the lamination process. In this case the release structure <NUM> (for instance a layer) can be applied on the copper foil (more generally electrically conductive layer structure <NUM>) and the stopping layer for the laser process (see laser cutting tool <NUM>) will be the electrically conductive layer structure <NUM>.

Referring to <FIG>, the constituents described referring to <FIG> may be interconnected by laminating, i.e. the application of pressure and/or heat. As a result, first portion <NUM> of the stack <NUM> is obtained.

Referring to <FIG>, annular through-holes may be formed extending through the magnetic foil <NUM> and extending up to the release structure <NUM> by a laser cutting tool <NUM>. Each through-hole surrounds, in a top view, a corresponding island of the release structure <NUM>. As indicated by reference numeral <NUM>, the laser cutting tool <NUM> may be movable so as to cut out pieces of the magnetic foil <NUM> above the respective portions of the release structure <NUM>. As an alternative to laser cutting, the annular through-holes may also be formed by mechanically cutting, etc..

The structure shown in <FIG> may be obtained by removing the cut out portions of the magnetic foil <NUM> within the annular through-holes and above the release structures <NUM>. Due to the non-adhesive property of the material of the release structures <NUM>, these magnetic portions of pieces may be simply taken out. The procedure of releasing cut-off parts may be supported by ultrasound vibration. If desired or required, remaining material of the release structures <NUM> may then be removed, for instance by stripping. By this procedure, non-uniform magnetic foil <NUM> is obtained.

Since the structure obtained according to <FIG> substantially corresponds to the structure obtained according to <FIG>, further processing according to <FIG> may be accomplished as described above referring to <FIG>, and further processing according to <FIG> may be accomplished as described above referring to <FIG>. The component carrier <NUM> according to <FIG> may additionally undergo a copper structuring and interconnection processing as known by those skilled in the art of printed circuit boards.

<FIG> illustrates a cross-sectional view of a portion of a component carrier <NUM> according to an exemplary embodiment of the invention. The component carrier <NUM> according to <FIG> further comprises vertical through-connections <NUM> extending through the stack <NUM> and the magnetic foil <NUM>. The vertical through-connections <NUM> are separated from the magnetic foil <NUM> laterally by material of the electrically insulating layer structures <NUM>. In the shown embodiment, the vertical through-connections <NUM> are laser copper vias. They are formed by firstly cutting holes in the stack <NUM> between adjacent islands or portions of the magnetic foil <NUM> by laser processing, and by subsequently filling copper material in the formed holes (for instance by plating, electroless deposition, a galvanic process, etc.).

Referring to <FIG>, a first body <NUM> and a second body <NUM> are provided and are arranged side by side, both comprising component carrier material. In the shown embodiment, each of the first body <NUM> and the second body <NUM> comprises an electrically conductive layer structure <NUM> (such as a copper foil, wherein a component <NUM> may be embedded there as well, see <FIG>) embedded in dielectric material of electrically insulating layer structures <NUM> (such as prepreg or FR4). In addition or alternatively to the embedded electrically conductive layer structures <NUM>, it is also possible to embed a component (such as an electromagnetic radiation generating component or an electromagnetic radiation sensitive component) in the respective first body <NUM> and/or second <NUM>. The first body <NUM> and the second body <NUM> are laterally spaced by a gap <NUM>. The shown arrangement of the first body <NUM> and the second body <NUM> is made in preparation of a subsequent placement of a magnetic foil <NUM> between an upper main surface <NUM> of the first body <NUM>, the gap <NUM> and a lower main surface <NUM> of the second body <NUM>. For instance, the first body <NUM> and the second body <NUM> may be formed by cutting a core in two pieces or by forming a slit-shaped recess as the gap <NUM> in an integral core (or other base body).

Referring to <FIG>, the flexible or bendable magnetic foil <NUM> is three-dimensionally bent to thereby guide the magnetic foil <NUM> from the upper main surface <NUM> of the first body <NUM> through the gap <NUM> up to the lower main surface <NUM> of the second body <NUM> to thereby three-dimensionally bend the magnetic foil <NUM>. As a result, a central portion <NUM> of the magnetic foil <NUM> is slanted in the gap <NUM> with regard to the main surfaces <NUM>, <NUM>. The magnetic foil <NUM> may either be a continuous foil or may be already pre-patterned or pre-structured.

Referring to <FIG>, further electrically insulating layer structures <NUM> of uncured material (for instance resin or prepreg) may be placed on top and below the structure shown in <FIG>. Subsequently, all mentioned constituents can be interconnected by lamination, i.e. the application of pressure and/or heat. As a result, the cavity or gap <NUM> is filled with cured resin. Thereby, the three dimensionally bent flexible magnetic foil <NUM> is secured in place in the three-dimensionally bent configuration. As a result, the component carrier <NUM> according to <FIG> is obtained.

In this embodiment, the three-dimensionally bent (and optionally patterned) magnetic foil <NUM> is configured for shielding electromagnetic radiation from propagating from first portion <NUM> of the stack <NUM> to second portion <NUM> of the stack <NUM>, or vice versa. As indicated by reference numeral <NUM>, the central portion <NUM> of magnetic foil <NUM> provides for a lateral shielding of electromagnetic radiation <NUM>, <NUM> which may propagate from the first body <NUM> (for instance from its electrically conductive layer structure <NUM> and/or a component <NUM> embedded therein) to the second body <NUM> (for instance to its electrically conductive layer structure <NUM> and/or a component <NUM> embedded therein), and/or vice versa.

Referring to <FIG>, the first body <NUM> and the second body <NUM> are vertically spaced and are each formed with a respective one of two cooperating surface profiles <NUM>, <NUM> which are here embodied as steps. Similar to the embodiment according to <FIG>, also in the present embodiment the first body <NUM> and the second body <NUM> together form the stack <NUM> when assembled and interconnected.

Referring to <FIG>, the magnetic foil <NUM> is guided along both surface profiles <NUM>, <NUM> of the bodies <NUM>, <NUM> so as to be three-dimensionally bent and thereby rendered non-uniform. A central portion <NUM> of the magnetic foil <NUM> is guided along an empty volume <NUM> (corresponding to gap <NUM>) which remains between the assembled bodies <NUM>, <NUM>.

Referring to <FIG>, the constituents according to <FIG> are then connected by laminating, i.e. the application of pressure and/or heat. Thereby, previously uncured material of the electrically insulating layer structures <NUM> becomes cured, and resin also flows into the empty volume <NUM> to fill up the latter. As described above referring to <FIG>, also the component carrier <NUM> according to <FIG> provides a lateral shielding function, thereby improving the EMI performance of the component carrier <NUM>.

<FIG> illustrates a cross-sectional view of a component carrier <NUM> according to an exemplary embodiment of the invention. The component carrier <NUM> according to <FIG> comprises multiple embedded components <NUM>. For instance, the components <NUM> may be electronic chips for high-frequency applications, and may for instance be configured as signal processing component, voltage converter, microprocessor, logic chip, etc. These and other types of components <NUM> may generate electromagnetic radiation <NUM>, <NUM>. If such electromagnetic radiation <NUM>, <NUM> propagates to other components <NUM> being sensitive with regard to such electromagnetic radiation <NUM>, <NUM>, this may disturb the operation as well as decrease the performance of such components <NUM>. In order to prevent such undesired effects, two patterned and hence non-uniform magnetic foils <NUM> are embedded as horizontal layers in stack <NUM> to provide for an interlayer shielding, see reference numeral <NUM>.

<FIG> illustrate different views of a component carrier <NUM> according to an exemplary embodiment of the invention. The application described referring to <FIG> relates to a ferrite bead on PCB balun and chokes. A ferrite bead or ferrite choke is a passive electric component that suppresses high frequency noise in electronic circuits.

Referring to <FIG>, a top view of a patterned non-uniform magnetic foil <NUM> is shown having a through hole through which electrically conductive layer structures <NUM> in the form of copper vias are guided and are connected to copper traces. <FIG> shows a corresponding three-dimensional view. <FIG> shows a cross-sectional view schematically illustrating the described coupling.

<FIG> shows a corresponding device with a plug <NUM> connected to a cable <NUM> which is wound and guided through a connector <NUM> (which may for instance be connected to a printer). However, many other applications of the concept illustrated schematically referring to <FIG> are possible as well.

Implementation of the invention is not limited to the preferred embodiments shown in the figures and described above. Instead, a multiplicity of variants are possible which use the solutions shown and the principle according to the invention even in the case of fundamentally different embodiments.

Claim 1:
A component carrier (<NUM>), wherein the component carrier (<NUM>) comprises:
a stack (<NUM>) comprising a plurality of electrically insulating layer structures (<NUM>) and a plurality of electrically conductive layer structures (<NUM>); and
a non-uniform magnetic foil (<NUM>) integrated in the stack (<NUM>),
wherein the non-uniform magnetic foil (<NUM>) is configured as an arrangement of multiple separate island structures;
characterized in that
the non-uniform magnetic foil (<NUM>) comprises a polymer matrix and magnetic particles embedded in the polymer matrix.