Forming solid material in recess of layer structure

based on applied fluidic medium

The invention relates to a method of manufacturing a component carri- er, and a component carrier.

In the context of growing product functionalities of component carriers equipped with one or more electronic components and increasing miniaturization of such electronic components as well as a rising number of electronic components to be mounted on the component carriers such as printed circuit boards, increasingly more powerful array-like components or packages having several electronic components are being employed, which have a plurality of contacts or connections, with ever smaller spacing between these contacts. Removal of heat generated by such electronic components and the component carrier itself during operation 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, simple manufacturabil- ity of a component carrier is desired in order to meet the challenge of an increased cost pressure by at the same time increasing reliability.

It is an object of the invention to provide a component carrier which can be manufactured in a simple and efficient procedure.

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

According to an exemplary embodiment of the invention, a method of manufacturing a component carrier is provided which comprises applying a fluidic medium selectively (i.e. not uniformly or unspecifically over an entire surface of the layer structure, but specifically spatially limited to a part of or the entire recess, optionally covering additionally a limited surrounding area of the recess) towards a recess (such as a blind hole, in particular a blind via) in a layer structure, and transferring at least part of the fluidic medium into solid material covering at least part of a surface of the recess. According to another exemplary embodiment of the invention, a component carrier is provided which comprises a layer structure having a recess, a pad delimiting at least part of the recess (in particular, the bottom of the recess may be formed by the pad), and at least one layer on the pad and completely within the recess (i.e. not extending spatially beyond the limits of the recess).

In the context of the present application, the term "component carrier" may particularly denote any support structure which is capable of

accommodating one or more components thereon and/or therein for providing mechanical support and/or electrical connectivity and/or thermal conductivity. In other words, a component carrier may be configured as a mechanical and/or electronic carrier for components, both in terms of surface mounting and embedding components. In particular, a component carrier may be one of a printed circuit board, an organic interposer, and an IC (integrated circuit) substrate. A component carrier may also be a hybrid board combining different ones of the above mentioned types of component carriers.

In the context of the present application, the term "fluidic medium" may particularly denote a material configured as a fluid comprising a liquid and/or a gas, optionally comprising solid particles.

According to an exemplary embodiment of the invention, a layer may be formed in a recess of a layer structure of a component carrier by the supply of a fluidic precursor which is transferred into a solid phase layer during or after its application to the recess. This transfer may be accomplished by evaporating the liquid and hence leaving the suspended particles in the recess. By taking this measure, capillary effects of fluids in tiny recesses may be advantageously used to cover not only a bottom surface, but also at least part of a side wall of the recess with solid material in a simple way. Such a side wall coating is highly advantageous (see also Figure 5, Figure 6 or Figure 13). By taking this measure, it is possible to form selectively definable layers specifically extending exclusively within the recess (i.e. not unspecifically outside of the recess), with low effort (in particular without cumbersome masking procedures) and high precision (for instance by ink-jetting).

More specifically, an exemplary embodiment of the invention makes it possible to fill up recesses (such as vias, which may be blind holes or through holes which can be manufactured for example by laser drilling, mechanical drilling, ablation within excimer laser, etc.) with an electrically conductive ink or another fluidic medium, for instance using an inkjet process, so that the fluidic medium - due to capillarity force - gets dragged upward and hence the wall of the recess or capillary is coated with fluid, in particular liquid. A capillary, under standard definition, may be denoted as a tube-like construction. But corresponding forces are also present when it is half open, meaning a construction composed of a bottom and only one side wall. Advantageously, the mentioned liquids may contain for example electrically conductive parti- cles. Further, it is possible to dry and/or cure the liquid, which leads to the result that the solid particles in the fluidic medium are left also on the side walls of the recess or hole and the liquid part of the fluidic system applied e.g . evaporates. It is also advantageous to form one or more diffusion barrier layers on (for instance aluminium) pads delimiting the recess, and to subse- quently apply one or more further metal layers. An example is a nickel layer (which acts as a diffusion barrier) on top of a copper layer. Highly advantageously, a diffusion barrier layer may be formed, for example by printing and by making use of the described capillary effect in a via-hole as the recess, wherein the barrier layer can be covered, in turn, with a seed layer, which may be also formed correspondingly based on a further fluidic medium (in particular through printing and the use of a capillary effect, compare for example Figure 1, Figure 2, Figure 3 and Figure 14).

Advantageously, the material filled recess may be used for various different functions, such as the formation of an electrically conductive connection and/or the formation of thermal heat removal paths.

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

In an embodiment, the solid material is formed completely within the recess. It is possible (for instance by selection of the kind of material, the amount of material, etc., of the fluidic medium) that the solid material is formed exclusively within the recess, i.e. does not extend beyond the recess. Advantageously, this is possible in embodiments of the invention without using a subtractive process (such as a lithography and an etching procedure). The solid material may coat the entire surface of the recess or only a part thereof.

In an embodiment, the fluidic medium is configured to adhere to a wall of the recess. Thus, the fluidic medium may be engineered (for instance by the addition of corresponding additives) in such a way that it has good adhesion properties to the wall.

In an embodiment, an aspect ratio of the recess (which may be for example defined as a ratio between a depth and a diameter of the recess) is at least 1.1, in particular is at least 1.5, more particularly is at least 2, even more particularly is at least 5. Especially the ratio height to diameter can be very long in contrast to standard PCB manufacturing (1 : 1) as a result of a manufacturing technology according to an exemplary embodiment of the invention. In an embodiment, applying the fluidic medium is carried out by an additive process. More precisely, the solid material (which is based on the applied fluidic medium) may be formed by an additive process, i.e. by the mere addition of material (rather than by removing material). This is an ecologically advantageous procedure and also allows for a simple and resource saving manufacturing procedure.

In an embodiment, the transferring comprises:

- a phase transition (for instance from a liquid, gaseous and/or plasma phase into a solid phase) of the fluidic medium upon contacting the layer structure (wherein this phase transition may be accomplished automatically when a (for instance laser) heated or evaporated fluidic medium reaches the cooler (i.e. non-heated) surface of the component carrier within the recess); or

- a cooling (in particular an active cooling) of the fluidic medium, in particular for changing its phase state from a fluidic state into a solid state; or

- a drying of the fluidic medium (for instance by evaporating a volatile solvent from the fluidic medium so that only a solid component remains on the surface of the recess); or

- a curing (for instance by a chemical treatment) of the fluidic medium. In an embodiment, applying the fluidic medium is carried out by filling a liquid base medium (for instance embodied as an evaporable or volatile liquid base medium, such as a solvent, which can be subsequently removed from the recess by heating or the like) with particles (in particular solid particles) therein in the recess, wherein the transferring is carried out by subsequently removing at least part of the liquid base medium out of the recess, in particular by evaporating, so that the dried particles remaining in the recess form the solid material. By taking this measure, the liquid base medium may simplify the handling during insertion of the fluidic medium into the recess. Furthermore, the liquid base medium may generate or promote a capillary effect in the recess which allows to cover also (slanted or even vertical) side walls of the recess with the solid material . A coverage can even be obtained when glass fibers extend or stick out of the side walls of a via, as it may occur for example with PCB materials such as prepreg or FR4 including reinforcing fibers. After removal of the liquid base medium, the non-removable solid material remains in the recess and covers the wall delimiting the recess.

In an embodiment, applying the fluidic medium is carried out by filling a liquidized medium (in particular a heated liquidized medium) in the recess, wherein the transferring is carried out by converting (in particular by cooling the liquidized medium) the liquidized medium into a solid state to thereby form the solid material (including no more solvents or additives, or only a little contribution of solvents and/or additives). Therefore, the phase transition of the fluidic medium from an at least partly fluidic state into a purely solid-state can be accomplished, in a very simple way, by the mere temperature difference between the fluidic medium prior to the deposition and the component carrier at the position of the recess, which may be denoted as a phase change transition.

In an embodiment, the applying can be performed by ink-jetting, screen-printing, or laser induced forward transfer.

Dispensing may be accomplished by a dispenser which may comprise a tubular member with a hollow lumen through which the fluidic medium, for instance an ink, to be dispensed or applied can be transported . At an open flange face of such a dispenser, the medium may pass out of the tubular member onto a surface portion of the component carrier, i.e. into the recess to ensure that the liquid medium is only applied partially.

A screen-printing device may comprise a screen with at least one through hole as medium supply opening through which the fluidic medium to be dispensed or applied can be transported towards the recess. Subsequently, the fluidic medium to be applied may be supplied from an upper side of the screen and may pass at one or more defined positions through the at least one through hole (which may define a pattern according to which the medium shall be applied to only selective surface portions of the component carrier, i.e. towards one or more recesses thereof). A squeegee may then move over the screen to promote passage of medium through the at least one through hole and to remove excessive medium from an upper side of the screen.

Laser induced forward transfer may involve a carrier plate on which a layer of a liquefiable medium (such as a metal) is applied . Laser radiation of a specific portion of this layer will then transfer part of the layer into a liquefied state, thereby generating the fluidic medium, which will be released from the carrier plate and may flow (for instance due to a gravitational force) towards the recess of the component carrier. When reaching the recess of the compo- nent carrier, the laser heated fluidic medium will be cooled down automatically and will be transferred back into the solid phase, thereby forming the solid material without taking any further measure.

The above described application methods are only exemplary, but not limiting. For instance, application of the fluidic medium may be accomplished also by aerosol printing, spraying, etc.

In an embodiment, the transferred solid medium forms a (curved or planar) layer. Thus, at least part of the surface of the recess may be coated with a thin film of preferably homogeneous thickness. Alternatively, it is also possible that the transferred solid medium forms a bulk structure.

In an embodiment, the transferred solid medium forms a curved layer, in particular a concavely curved layer (i.e. a curved layer having a concave shape or form) or a U-shaped layer.

In an embodiment, the method comprises forming a further layer on the layer. For instance, the first layer may be a barrier layer accomplishing a barrier against an undesired diffusion of material . The optional further layer may be a seed layer being configured for serving as a proper basis for a subsequent further material deposition, for instance a copper process (such as a chemical and/or a galvanic copper process). When only one layer is applied, it is possible that this layer serves as a seed layer, for instance directly on a pad and/or on a side wall of a recess, for instance a via. Instead of a via, it is always possible to use a cavity throughout the entire context of the present application.

In an embodiment, the further layer is formed by applying a further flu- idic medium selectively (i.e. not uniformly or unspecifically over an entire surface of the component carrier, but specifically spatially limited to a part of or the entire layer in the recess, optionally covering additionally a limited surrounding area of the recess) onto the layer in the recess, and transferring at least part of the further fluidic medium into solid material, thereby forming the further layer covering at least part of the layer. Thus, manufacture of the further layer may be carried out correspondingly to the above-described manufacture of the first layer - in particular making use again of the described capillary effect.

In an embodiment, the method comprises forming a bulk material on the layer or (if present) on the further layer, in particular by a galvanic process. Alternatively, the bulk material may also be formed otherwise, for instance by a chemical process. The bulk material may be metallic copper. This allows to implement standard processes of PCB (printed circuit board) technology for a manufacturing method according to an exemplary embodi- ment of the invention.

In an embodiment, a bottom of the recess is delimited by electrically conductive material and a sidewall of the recess is delimited by electrically insulating material. Filling the recess with further electrically conductive material will then allow to electrically connect the electrically conductive material with an electronic periphery.

In an embodiment, the electrically conductive material may be a pad of a component (such as a chip pad) or part of a patterned electrically conductive layer structure (for instance an interior patterned copper foil). For instance, the electrically conductive material may be a buried chip pad . Due to the possibility of applying a barrier layer, it is also possible to contact non-copper pads. In another embodiment, the electrically conductive material is a buried metal layer, such as a patterned copper foil . Such an embedded wiring structure may be also electrically contacted with the described process. In an embodiment, the solid material forms a preconditioning layer preconditioning at least part of a wall delimiting the recess. In other words, the material of the preconditioning layer may preconditioning the recess so that it becomes appropriate for a subsequent process (for instance a galvanic process).

In an embodiment, the solid material provides for an electrically conductive connection. Thus, the described process may allow to establish any desired electric wiring structure.

In an embodiment, the solid material forms a sealing layer which pro- vides for a waterproof sealing . Undesired leakage of fluids such as water may therefore be prevented, so that the reliability of the manufactured component carrier may be improved .

In an embodiment, the solid material forms a barrier layer keeping material of the layer structure separated from material above or below the barrier layer. Undesired migration or diffusion of material may therefore be disabled, which also improves reliability of the manufactured component carrier.

In an embodiment, the solid material forms a seed layer (for instance a thin copper layer, or a layer made of palladium) configured for promoting deposition of material thereon, in particular by plating . Such a seed layer may serve as a basis for a subsequent galvanic deposition (which is not possible on each and every surface) or a chemical deposition (i.e. non-galvanically).

In an embodiment, the before mentioned layer is made of the same material as the pad. It is however also possible that the layer is made of a different material than the pad.

In an embodiment, the pad is a non-copper pad . In particular the provision of a barrier layer renders also electronic components with non-copper pads electrically contactable by the process according to an exemplary embodiment of the invention. Correspondingly, the barrier layer may be a non- copper layer.

In particular when the component pad is made of aluminum, a chemistry as used in a standard PCB chemical/galvanic copper process (at least cleaning the via) may attack the component's aluminum pad and hence deteriorate or destroy the component and/or the connection to the component. In order to overcome such and other issues, an exemplary embodiment of the invention implements a barrier layer to prevent such a determination or damage of the component or its connection.

In an embodiment, the recess is a vertical through connection, in particular a via. Such a via may be formed by laser drilling or by mechanically drilling .

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 conduc- tive 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 shaped as a plate. This contributes to the compact design, wherein the component carrier nevertheless provides a large basis for mounting components thereon. Furthermore, in particular a naked die as example for an embedded electronic component, can be conveniently embedded, thanks to its small thickness, into a thin plate such as a printed circuit board .

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 (for instance a PCB like structure) 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-4 or FR-5), 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.

One advantage of an exemplary embodiment of the invention is that the adhesion especially to polyimide and LCP is enhanced due to the possibility to specially engineer the fluidic medium that it matches the surface properties of the recess material (for example polyimide).

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.

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), 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 microelectrome- chanical system (MEMS), a microprocessor, a capacitor, a resistor, an inductance, a battery, a switch, a camera, an antenna, a logic chip, 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 core) 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 mount- ed on the component carrier and/or may be embedded in an interior thereof. Moreover, also other components, in particular those which generate and emit electromagnetic radiation and/or are sensitive with regard to electromagnetic radiation propagating from an environment, may be used as component.

In an embodiment, the component carrier is a laminate-type component carrier. 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.

The aspects defined above and further aspects of the invention are ap- parent from the examples of embodiment to be described hereinafter and are explained with reference to these examples of embodiment.

Figure 1 to Figure 4 illustrate cross-sectional views of structures obtained during carrying out a method of manufacturing a component carrier according to an exemplary embodiment of the invention.

Figure 5 and Figure 6 are cross-sectional views of structures illustrating a phenomenon occurring during carrying out a method of manufacturing a component carrier according to an exemplary embodiment of the invention.

Figure 7 to Figure 10 show cross-sections of component carriers according to exemplary embodiments of the invention.

Figure 11 and Figure 12 show flowcharts illustrating procedures carried out during executing a method of manufacturing a component carrier according to an exemplary embodiment of the invention.

Figure 13 is an image of a manufactured structure according to an exemplary embodiment of the invention.

Figure 14 is a cross-sectional view of a component carrier according to an exemplary embodiment of the invention.

The illustrations in the drawings are schematic. In different drawings, similar or identical elements are provided with the same reference signs.

Before, referring to the drawings, exemplary embodiments will be described in further detail, some basic considerations will be summarized based on which exemplary embodiments of the invention have been developed .

Exemplary embodiments of the invention provide a possibility of forming a via fill with an inkjet process. Furthermore, it is possible to manufacture a seed layer in a recess forming the basis of a subsequent plating procedure or the like.

One gist of an exemplary embodiment of the invention is to provide an opportunity to efficiently electrically connect an embedded electronic

component, even if the latter does not have a conventionally required copper end surface on one or more pads thereof. As the described process discloses, a seed layer may be applied on a recess exposing such a pad which coats also the side walls of the recess (which may be a laser via or a cavity) and prepares such a layer structure or component carrier for a possible further plating process.

An exemplary embodiment of the invention is based on the idea that a liquid medium, due to capillarity force, gets dragged upward in a capillary and hence does not remain only on the bottom, but in contrast to this also the side wall of the capillary is coated with the liquid (due to the so-called capillary effect). The fluidic medium (such as an ink) itself may contain particles or agents in liquid or suspension form. In a second procedure, it is for example possible to dry or cure the liquid (for instance by evaporating the solvent), which leads to the results that the particles which may for instance be contained in the ink are left on the side walls of the recess or hole, and hence the recess or hole may be coated with these particles. These particles may then form a layer which, for example, can act as a seed layer for a subsequent process (for example the formation of galvanic copper) or, in the case they are electrically conductive, as an already made electrical connection .

An exemplary embodiment of the invention therefore addresses on one side electroless copper deposition, which is a process which is complex, costly and hard to control (in this process, it is possible that palladium acts as a seed layer for chemical copper deposition, wherein this process is needed for example to put copper into laser vias). On the other side, an exemplary embodiment of the invention may address a different problem which arises in the technology of embedding electronic components. In terms of such an application, many electronic components have a non-copper surface finish on its pad(s), which may make it difficult to be connected in a standard

component carrier (in particular printed circuit board) copper process (for example, many electronic components have an aluminum surface finish, so that a standard process for copper deposition would be ineffective and, under undesired circumstances, might deteriorate or even damage the component itself. For such a scenario, the above described technique can be used to electrically connect such a component.

It should be mentioned that in different embodiments, the same or different inks can be applied . In the case of different inks, different functions for different layers can be realized (for instance a first liquid may form a barrier layer (for instance comprising or consisting of Ni, NiV, Pt, Pd, Co, etc.) which can be dried and/or cured, and subsequently a desired further electrically conductive layer (for instance comprising or consisting of Cu, Ag, Au, Pt) can be applied.

Figure 1 to Figure 4 illustrate cross-sectional views of structures obtained during carrying out a method of manufacturing a component carrier 100 according to an exemplary embodiment of the invention. In this

embodiment, a via fill procedure with an inkjet architecture is used for thin layer deposition for galvanic copper plating .

Referring to Figure 1, a fluidic medium 102 is applied selectively, i.e. only, towards a recess 104 in a layer structure 106. This is indicated

schematically by a drop in Figure 1. Thus, the application of the fluidic medium 102 is carried out by an ecologically advantageous additive process in which a cumbersome masking procedure is dispensable. As can be taken from a detail 177 in Figure 1, the fluidic medium 102 which is filled in the recess 104, is composed of an evaporable liquid base medium 110 as solvent with solid electrically conductive particles 112 therein. For example, the fluidic medium 102 may be applied into the recess 104 by ink-jetting so that, in this

embodiment, the fluidic medium 102 may be also denoted as an ink.

The layer structure 106 comprises an electrically insulating layer structure 128, for instance made of prepreg . Furthermore, the layer structure 106 comprises an electrically conductive layer structure 126 on its surface, for instance a copper foil . The layer structure 106 may be embodied as a laminated stack of the mentioned (and optionally further) layer structures 126, 128. Furthermore, an electronic component 130, for example a semiconductor chip, is embedded within the electrically insulating layer structure 128. An electrical- ly conductive pad 124 of the electronic component 130 is exposed by the recess 104, which can be formed by laser drilling of the layer structure 106. Due to the manufacturing procedure described in the following in further detail, it is possible - but not necessary - that the pad 124 is made of copper, for instance it may be made of aluminum or tin. As a consequence of the shown formation of the recess 104, a bottom of the recess 104 is delimited by the electrically conductive material in form of the pad 124, whereas a sidewall of the recess 104 is delimited by the electrically insulating layer structure 128 and the electrically conductive layer structure 126.

As indicated by the drop in Figure 1, Figure 1 illustrates a first part of the procedure of forming a barrier layer 114 by deposition. This procedure will be completed by transferring the fluidic medium 102 applied by ink jetting into a layer of solid material 108 covering the entire recess 104, as shown in Figure 2.

Referring to Figure 2, the fluidic medium 102 has been transferred into the solid material 108 covering the entire, but not more than the entire surface of the recess 104 by drying or curing the fluidic medium 102.

Consequently, the liquid base medium 110 will evaporate, so that only the dried electrically conductive particles 112, such as electrically conductive nickel particles, will remain and will coat the entire surface of the recess 104. Thus, the solid material 108 provides for an electrically conductive connection of the electronic component 130 and its pad 124 with regard to an electronic periphery. Due to the capillary effect, the solid material 108 will also cover the side walls of the recess 104. It should be mentioned that, alternatively, it is also possible that only a part of the surface of the recess 104 is covered by the solid material 108. The solid material 108 forms a diffusion barrier layer 114 preventing diffusion of material of the pad 124 through the barrier layer 114 as well as diffusion in opposite direction. In particular, the diffusion barrier layer 114 prevents migration of copper towards the embedded component 130. As shown in Fig 2, the diffusion barrier layer 114 is formed as a curved layer, more specifically as a concavely curved (or U-shaped) layer.

However, Figure 2 shows as well a subsequent procedure of a

deposition of a further layer, i.e. a seed layer 116, on the barrier layer 114. Formation of this seed layer 116, which may be made of copper, is advantageous when galvanic copper formation (compare Figure 4) is desired in the coated recess 104.

In the shown embodiment, the seed layer 116 is formed by applying a further fluidic medium 118 selectively onto the barrier layer 114 in the recess 104, for instance by a further ink jet deposition procedure, as indicated schematically by a drop in Figure 2.

Thus, Figure 2 illustrates a first part of the procedure of forming seed layer 116 by deposition. This procedure will be completed by transferring the further fluidic medium 118 applied by ink jetting into a further layer of solid material 120 covering the entire barrier layer 114, as shown in Figure 3.

Referring to Figure 3, the further fluidic medium 118 has been transferred into the further solid material 120 covering the entire, but not more than the entire surface of the barrier layer 114 by drying or curing the further fluidic medium 118. Consequently, the liquid base medium of the further fluidic medium 118 will evaporate, so that only dried electrically conductive particles, such as electrically conductive copper particles, will remain and will coat the entire surface of the barrier layer 114. Thus, the further solid material 120 contributes to the electrically conductive connection of the electronic component 130 and its pad 124 with regard to the electronic periphery. Due to the capillary effect, the further solid material 120 will also cover the slanted side walls of the barrier layer 114. It should be mentioned that, alternatively, it is also possible that only a part of the surface of the barrier layer 114 and hence of the recess 104 is covered by the further solid material 120. The transferred further solid material 120 forms the seed layer 116 enabling galvanic copper deposition thereon with high efficiency.

Referring to Figure 4, a bulk material 122, here embodied as galvanic copper, is deposited galvanically directly on the seed layer 116 as well as on the electrically conductive layer structure 126 (made of copper). As a result of the described manufacturing method, component carrier 100 according to an exemplary embodiment of the invention is obtained having the features as described above and being shown in Figure 4. The component carrier 100 is here embodied as a printed circuit board (PCB)

Advantageously, the described manufacturing procedure uses copper ink (as further fluidic medium 118) instead of electroless copper as a basis for the formation of the thin seed layer 116 for subsequent galvanic copper plating . This manufacturing architecture, in particular in addition to the formation of the barrier layer 114, makes it possible to contact also non- copper surfaces (such as aluminum pads 124 on IC type electronic component 130). Deposition of barrier layer 114 safely prevents the migration of copper to the embedded component 130. The described additive process allows to reduce the ecological footprint of the manufactured component carrier 100. This technology allows a wider range of integrated circuits as electronic component 130 to be embedded, since there is no limitation to specific pad materials (in particular copper finished pads). The illustrated manufacturing architecture also reduces costs and effort, since the now dispensable

electroless copper deposition is an expensive process (involving sophisticated materials such as palladium). Using ink-jet according to an exemplary embodiment of the invention, i.e. an additive process, may save material costs as well, since direct thin copper deposition is obtained locally where needed. Furthermore, the manufacturing procedure offers a wider choice of

components to be embeddable, thereby overcoming conventional limits of copper finish for the contact pads 124.

Figure 5 and Figure 6 are cross-sectional views of structures illustrating the capillary effect occurring during carrying out a method of manufacturing a component carrier 100 according to an exemplary

embodiment of the invention. The shown capillary effect allows to coat significant areas of side walls of a hollow structure by a liquid. Figure 2 and Figure 3 have shown how this effect can be used to fully coat recesses 104 in a component carrier 100 with a continuous layer (see reference numerals 114, 116) extending over bottom wall and sidewall of recess 104.

Figure 5 hence shows more generally what happens to a liquid when a tube/capillary is put into it liquid. Figure 6 shows again quite generally the scenario of an exemplary embodiment of the invention, i.e. a liquid in a hole.

Figure 7 to Figure 10 show cross-sections of component carriers 100 according to exemplary embodiments of the invention.

Referring to Figure 7, a component carrier 100 according to an exemplary embodiment of the invention is shown in which the layer structure 106 is a multilayer structure with an alternating sequence of electrically insulating layer structures 128 (which may be prepreg layers) and electrically conductive layer structures 126 (which may be patterned copper foils) forming a laminated PCB stack. According to Figure 7, the laser drilled (or alternatively mechanically drilled) recess 104 exposes a buried portion of one of the electrically conductive layer structures 126 to be electrically connected . A seed layer 116 (in this embodiment without the prior formation of a barrier layer 114, which is dispensable according to Figure 7 due to the lack of an electronic component 130 with a non-copper pad 124 in this embodiment) is directly formed on the interior surface of the recess 104 by a procedure similar to that as described above referring to Figure 2 and Figure 3. The seed layer 116 may be made of copper. Although not shown in Figure 7, it is possible to

galvanically fill the remaining portion of the recess 104 with copper directly on the seed layer 116. Thus the component carrier 100 shown in Figure 7 can be obtained by applying a liquid precursor (as further fluidic medium 118), drying or curing the latter and (not illustrated in Figure 7) subsequently depositing copper on the seed layer 116 (galvanically or, in other embodiments, chemically).

Referring to Figure 8, the component carrier 100 shown there is similar to the structure shown in Figure 3 with the differences that multiple recesses 104 have been coated and that a barrier layer 114 is omitted according to Figure 8, so that the seed layer 116 is deposited directly on the non-copper pad 124. Although the component carrier 100 shown in Figure 3 can have a pronounced reliability due to the presence of barrier layer 114, the component carrier 100 shown in Figure 8 is very simple in manufacture and may provide a quality sufficient for certain applications. The electronic component 100 shown in Figure 8 can be obtained by applying a liquid as fluidic medium 118, drying or curing the latter and (not illustrated in Figure 8) subsequently depositing copper on the seed layer 116 (galvanically or, in other embodiments, chemically).

Referring to Figure 9, the component carrier 100 shown there is similar to the embodiment of Figure 8 with the exception that the seed layer 116 is formed by printing rather than by ink jetting and only covers a bottom wall of the recess 104. More specifically, the seed layer 116 can be printed only on the pad 124. Thus, the electronic component 100 shown in Figure 9 can be obtained by printing a precursor of the seed layer 116, drying or curing the latter and (not illustrated in Figure 9) subsequently depositing copper on the seed layer 116 (galvanically or, in other embodiments, chemically).

Referring to Figure 10, the component carrier 100 shown there is similar to the embodiments of Figure 8 to Figure 9 with the exception that a bulk material 122 of copper has been formed to completely fill the recess 104 by printing .

Still referring to Figure 5 to Figure 10, Figure 5 shows the behavior of a capillary tube 500 which is immersed into a liquid 502. Figure 6 shows a similar case, wherein in this case the bottom of the capillary tube 500 is closed by a base 504 and the liquid 502 is filled into it. Figure 7 to Figure 10 show a corresponding PCB situation where the capillary tube 500 is represented by a laser via or recess 104. Similar as shown in Figure 1 and Figure 2, a fluidic medium 102 (or 118) composed of a liquid base medium 110 containing particles 112 is filled in and, according to physical laws, the fluidic medium 102 (or 118) coats the bottom as well as the side walls. The physical law which governs height h (see Figure 5 and Figure 6) is: h = (2o coscp)/(pgr), wherein σ is the surface tension, φ is the contact angle, p is the density of the fluidic medium, g is the gravity constant and r is the radius of the tube 500 or the recess 104. Figure 5 and Figure 6 furthermore show a force equilibrium between a gravitational force G and a counter force F.

In other words, for a given liquid and surface (i.e. the hole walls and the bottom), the height h up to which the liquid is dragged up is purely governed by the (adjustable by material selection) density p of the liquid and the radius r of the capillary tube 500. It should be noted that especially for small holes or recesses 104 (for instance smaller than 1 mm, in particular smaller than 500 prn, more particularly smaller than 100 prn, etc.) the height h to which the liquid will go up increases, which makes it especially favorable and easy to fill long and small holes or recesses 104.

It is very difficult in standard PCB processes to plate long and narrow vias. There are standard design rules in place which allow a ratio of hole diameter to length which is not greater than 1 : 1. With the described

embodiment of the invention, such restrictions are not present as the height of the liquid which equals to the length of the hole can be tuned . Thus,

significantly larger aspects ratio of for instance 1.5 or more can be obtained by exemplary embodiments of the invention.

A person skilled in the art will understand that on one side it is favorable that the liquid coats the bottom or base 504 (in a component carrier related example, a pad 124 of an electronic component 130) and the side walls, but when only the bottom is coated and thereby the (for example aluminum) pad 124 of the electronic component 130 is protected against aggressive liquids such as permanganate, it is not necessary that also the side walls are coated . In this case, an additional chemical copper process can be carried out, to provide the seed layer 116 as a basis for a subsequent galvanic copper process. A reason behind this is the possible utilization of a laser induced forward transfer process, which employs a different approach (i.e. liquidizing a previously solid material on a carrier by laser heating and re-solidifying the liquefied material upon contacting it with the cooler layer structure in the recess by an automatically occurring cooling), and it cannot be expected that the printed - in this case copper - material is coating the walls (for the laser induced forward transfer process, a phase change like material is used, meaning that when the printed copper droplet hits the surface, it freezes out immediately, meaning it gets from liquid to solid phase and hence loses the flow properties). Another possibility is that the material fills out the entire via completely.

One exemplary process flow for the recess filling procedure of an embodiment of the invention is illustrated in Figure 11 and Figure 12 :

Figure 11 and Figure 12 show flowcharts 1100, 1200 illustrating procedures carried out during executing a method of manufacturing a component carrier 100 according to an exemplary embodiment of the invention.

Referring to Figure 11, a recess formation and preconditioning

procedure can be carried out, as illustrated in a block 1102. This may involve the preparation of the recess 104 or hole, and an optional cleaning of the hole or recess 104. Possible cleaning methods are plasma cleaning, wet chemistry cleaning, etc. Also an optional preconditioning of the hole or recess 104 can be carried out. For the cleaning, also a wet chemistry-based processing can be used . Other processes like plasma cleaning can also be implemented . Other cleaning methods, for instance rinse with water containing cleaning agent, solvent containing surface treatment agent, etc., are also possible.

As illustrated in a block 1104, it is then possible to fill the hole or recess 104 with liquid (see reference numeral 102 and Figure 1) containing for example particles, agents, etc. Filling of the hole or recess 104 can be achieved using, for example, inkjet, dispensing, dip coating, micro-spotting, curtain coating, spray coating, all types of print and dispensing methods. Also a laser induced forward transfer process may be implemented . More generally, any method may be employed which allows to print, dispense, etc. locally an ink as an embodiment of the fluidic medium 102.

As illustrated in a block 1106, the applied liquid (i.e. the fluidic medium 102) may be dried and/or cured. Drying methods, which may be implemented according to exemplary embodiments of the invention, are treatments in an oven, by infrared, by laser radiation, by ultraviolet radiation, by radio frequency radiation, by a plasma, etc. Generally, all methods may be carried out which allow the solvent of the ink (i.e. the liquid base medium 110 of the fluidic medium 102) to be evaporated .

As illustrated in a block 1108, curing the material can be carried out as an optional procedure. Curing mechanisms which can be implemented according to an exemplary embodiment of the invention are treatments in an oven, by infrared, by laser radiation, by ultraviolet radiation, by

radiofrequency radiation, by chemical interaction (for instance using a corresponding agent), by a plasma, etc. More generally, all methods may be implemented for curing which alter the structural and physical performance of the material.

Referring to Figure 12, it is optionally possible to carry out a further drying and/or curing procedure of the ink (compare block 1202). As illustrated in a block 1204, printing of a second ink (such as further fluidic medium 118) containing a different material can be carried out (compare Figure 2).

Thereafter, a galvanic process may be carried out (compare block 1206 and Figure 4). Figure 13 is an image of a manufactured structure according to an exemplary embodiment of the invention captured by X-section analysis and showing a trench structure processed as described above referring to Figure 11.

Figure 13 shows a layer which was manufactured with a method according to an exemplary embodiment of the invention. The ink layer was originally a low viscosity fluid with silver nanoparticles. Subsequently, the liquid was dried and the particles form the layer.

After the described process, the particles or agents which were contained in the fluidic medium such as an ink will coat the side walls of the recess or hole. Figure 13 shows a dried ink containing in this case silver nanoparticles after the solvent is evaporated (in this case, the recess is not embodied as a hole but as a trench, wherein the result will be substantially the same as the underlying physics is the same).

After the procedure according to Figure 11 resulting in the structure shown in Figure 13, a following procedure can be carried out as described in Figure 12 (being optional and interchangeable depending on the required hole characteristic).

The above described process is only one embodiment of the invention, and is in some cases a favorable process how to electrically connect two layers of a printed circuit board (PCB) in vertical or z-direction. In addition this, such a process may allow connecting embedded components which do not have copper surface finished pads in vertical or z-direction (for example by laser vias).

For exemplary embodiments of the invention, different kinds of fluidic medium (such as ink) may be implemented. Basically, the applied fluidic medium (such as an ink) can have functions as:

A) acting as a seed layer for a subsequent (for instance electrogalvanic copper) process.

B) acting as a barrier layer with regard to a surrounding to avoid for example diffusion into surrounding material (especially advantageous in the combination copper ink on aluminum pads, since in this case the copper may diffuse into the aluminum which may deteriorate or damage the component functionality. C) preconditioning the recess or hole in a sense of modifying the surface characteristic of the recess or hole, for example by changing the contact angle of a further fluidic medium (such as a second ink) which is deposited after the first fluidic medium (such as a first ink).

D) acting as an electrically conductive layer to form an electric connection

E) sealing off the surrounding material and protecting it from water intake. In this case, the material may act again as a barrier layer, but to a harsh environment, especially when the PCB comes into contact to water, biological fluids such as blood, etc., which may diffuse into the build-up

Functions A)-D) can be implemented by carrying out a second print. Functions B)-C) may involve a deposition of a second material.

Fluidic media, in particular inks, which may be used according to exemplary embodiments of the invention are metal loaded inks (for example silver, copper, gold, palladium, electrically conducting polymers). Preferably, the fluidic medium or ink may have favorable surface energy to the

surrounding material which has to be coated . In generally, it is advantageous that the fluidic medium properties ensure that h (see formula above) is sufficiently high or even maximized for properly fulfilling its function.

In the following, further details concerning inks as fluidic media, specifically for the case of copper, will be described. As mentioned above, it is advantageous for some inks to involve a reducing agent. For example, copper inks may be implemented as a precursor, for example copper oxide inks (which are electrically insulating) which need to be reduced to become electrically conductive. In one embodiment, this can be accomplished by implementing a second ink (in this case, the ink may contain a reducing agent which reduces the copper oxide to copper and hence an electrical conductivity is achieved). In other embodiments, it is possible that an implemented fluidic medium or ink requires a (for instance hydrogen) plasma treatment which again reduces the copper oxide to copper. Other implementable copper inks may have the reducing agent already incorporated . They may need for example a light pulse to start the reduction of copper oxide to copper.

What concerns fluidic medium application techniques, a special selective deposition is favorable (for instance inkjet, screen print, etc.) Hole or recess formation can be carried out mechanically or by laser processing . Hole or recess cleaning, etc., can be carried out before further processing. Optionally, surface roughening of the recess or hole can be carried out. Especially recesses with small diameter and long or deep recesses can be filled reliable.

By exemplary embodiments of the invention, it is possible to electrically connect two layers or other structures of a PCB. In this context, exemplary embodiments of the invention may advantageously provide for example a seed layer formed on the basis of the applied fluidic medium. In terms of

component embedding, exemplary embodiments of the invention make it possible to electrically contact also electronic components which do not have a conventionally required copper surface finish of the connected pads. Problems arising from this fact are that conventionally no reliable copper deposition to electrically connect component to the artwork is possible. Furthermore, migration of for example copper into aluminum surface finish of a component can occur, etc. In order to overcome such shortcomings, exemplary

embodiments of the invention deposit a first ink, for example a nickel ink, which has a barrier function. In a second procedure, an ink (for instance comprising copper) is deposited which can act as a seed layer for a galvanic copper process or provides already sufficient electric conductivity to act as electrical connection itself. The described process - capillary filling and subsequent drying and/or curing may stay the same for both fluidic media or inks. In a method according to an exemplary embodiment of the invention, electronic components with different pad finishes on the same component can be connected as only those pads can be addressed (by special selected deposition of the material, etc.) which do not have the right surface finish.

A skilled person will further understand that a process according to an exemplary embodiment of the invention is robust, as changes in, for instance, contact angle, hole diameter or even the presence of glass fibers at a sidewall of a hole, etc., will influence the process only to a minor extent, as it can be reasonably assumed that such changes are comparable small.

Concluding, an exemplary embodiment of the invention applies a seed layer and/or a barrier layer via capillary filling of a for example laser via. Local deposition of barrier layer and/or electrically conductive layer on one or more electronic components already embedded in a component carrier such as a PCB is highly advantageously.

In particular, connection of one or more electronic components with non-copper surfaces or a mix of different surfaces on the same electronic component with different aspect ratios can be effectively filled.

Thus, it is no longer necessary with exemplary embodiments of the invention that a component to be embedded must have a copper finish surface. Thus, the provision of a copper finish may become dispensable. The fact that the used capillary forces are particularly high at low dimensions allows to further miniaturize component carriers.

Figure 14 is a cross-sectional view of a component carrier 100 according to an exemplary embodiment of the invention. The embodiment according to Figure 14 is similar to the embodiment shown in Figure 3 with the exception that both barrier layer 114 and seed layer 116 do not extend completely over the entire extension of the recess 104 according to Figure 14, i.e. end vertically at the bottom side of the electrically conductive layer structure 126 which has uncovered exposed side walls.

It should be noted that the term "comprising" does not exclude other elements or steps and the "a" or "an" does not exclude a plurality. Also ele- ments described in association with different embodiments may be combined .

It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.

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.