TECHNICAL FIELD

The invention relates to an electronic device and to a method of manufacturing an electronic device.

TECHNOLOGICAL BACKGROUND

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. At the same time, component carriers shall be mechanically robust and electrically reliable so as to be operable even under harsh conditions. It is also desirable that component carriers are compatible with the processing of high-frequency signals.

SUMMARY

There may be a need for a simply manufacturable electronic device with multiple components and high thermal performance.

According to an exemplary embodiment, an electronic device is pro-vided which comprises a first component carrier, a second component carrier connected with the first component carrier so that a thermal decoupling gap is formed between the first component carrier and the second component carrier, a first component on and/or in the second component carrier, and a second component having a first main surface mounted in the thermal decoupling gap so that at least part of an opposing second main surface and an entire sidewall of the second component is exposed with respect to material of the first component carrier and with respect to material of the second component carrier.

According to another exemplary embodiment, a method of manufacturing an electronic device is provided, wherein the method comprises providing a first component carrier, providing a second component carrier with a first component (which may be an embedded component or a surface mounted component), connecting the second component carrier with the first component carrier so that a thermal decoupling gap is formed between the first component carrier and the second component carrier, and mounting a first main surface of a second component in the thermal decoupling gap so that at least part of an opposing second main surface and at least part of an entire sidewall of the second component is exposed with respect to material of the first component carrier and with respect to material of the second component carrier.

Overview of Embodiments

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. In other words, a component carrier may be configured as a mechanical and/or electronic carrier for 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 “component” may particularly denote an inlay-type member. Such a component may be arranged in particular in an interior of or on the first component carrier and/or the second component carrier, respectively. A component may in particular have an electronic function and may thus be a heat source in view of ohmic losses. For instance, such a component may be a semiconductor die.

In the context of the present application, the term “thermal decoupling gap” may particularly denote a cavity in an interior of the electronic device which cavity has a portion being thermally insulating. For instance, such a cavity may be not filled with solid material, but may be empty or gas filled (in particular air filled). Thus, a thermal decoupling gap may for example be an air gap. In particular, a thermal decoupling gap type cavity between first component carrier and second component carrier may be partially filled with the second component and may remain partially unfilled. In certain embodiments, the thermal decoupling gap may be embodied as or may be denoted as a thermal decoupling structure, a heat decoupling gap, a buffer gap, or an insulation gap.

According to an exemplary embodiment, an electronic device or module is provided which comprises a first component carrier (such as a substrate or a printed circuit board) and a second component carrier (such as a further substrate or a further printed circuit board) with at least one encapsulated or surface mounted first component. Between the first component carrier and the second component carrier, at least one second component is sandwiched, however with a thermal decoupling gap in between. More specifically, the at least one second component is exposed with respect to material of the second component carrier and with respect to material of the first component carrier both at one main surface (opposing a mounting surface) and at entire sidewalls of the at least one second component. By taking this measure, a reliable thermal decoupling between the at least one second component (for instance a heat source such as a processor chip) and the at least one first component (for instance a heat sensitive unit such as a memory chip) may be ensured. Highly advantageously, both thermal paths between the first and second components along a vertical direction as well as along a lateral direction may be interrupted by the thermally insulating thermal decoupling gap with the mentioned properties. This prevents undesired heating of the at least one first component by the at least one second component, or vice versa. Simulations have confirmed that an airgap has an advantageously pronounced impact on the thermal decoupling between first and second components. Thus, the components may be safely prevented from failure or damage while simultaneously maintaining a compact configuration of the electronic device.

In the following, further exemplary embodiments of the electronic device and the method will be explained.

A gist of an exemplary embodiment is the provision of a vertical and lateral thermal decoupling gap for thermal isolation of at least one first component (in particular memory chips) encapsulated in or surface mounted on a second component carrier from at least one second component (in particular a processor) arranged between two component carriers (such as a PCB or an IC substrate). By taking this measure, it is in particular possible that heat created by the second component (in particular processor heat) can be removed to a bottom side via vertical connections and/or thermally conductive plates (preferably made of copper), i.e. away from the one or more first components. In case the materials of the first component carrier and the second component carrier do not provide sufficient protection of the components (in particular semiconductor dies) against an environment (for instance protection against moisture), one or more of the components can be sealed or at least partially covered with an additional coating or barrier layer (for instance made of parylene, polytetrafluoroethylene (PTFE)) coating while maintaining the thermal decoupling gap or cavity for thermal isolation. Exemplary embodiments also provide methods and structures for additional component embedding to simultaneously solve issues in terms of vertical height or module thickness. An electrical and thermal performance improvement may be achieved as well as a reliability improvement. Exemplary embodiments are especially useful to combine a thermally isolating and thermally channelling thermal decoupling gap with a proper thermal management and with embedding of components to keep the vertical height of the electronic device small. An electronic device (for example a package-on-package, PoP, structure) according to exemplary embodiments may use a backside cavity of a top substrate or package or an additional connection body (such as a spacer frame) with integrated (for instance through) hole or opening for defining the thermal decoupling gap. Descriptively speaking, the connection body may function as an electromechanical interconnection. It is also possible to implement a layer bonding method (for instance thermo-compression bonding of copper pads with or without solder caps) to streamline the manufacturing process and keep the vertical thickness of the electronic device small.

Embodiments provide a method and an electronic device to thermally isolate a first component (for instance a memory chip) on the top of the electronic device from another second component (for example a processor or heat source) on the bottom side of the first component, and to ensure heat removal along lateral and vertical heat removal paths for avoiding undesired overheating of said components. Additionally, the electronic device is capable of reducing a height in vertical direction by optionally embedding of at least one further component (for instance a power management integrated circuit, one more passive components, etc.) in the first component carrier. In particular, a thermal decoupling gap may be formed vertically and laterally of the second component arranged between the first component carrier and the second component carrier for thermal isolation of the first component (such as a memory). Height of the electronic device may be very small while maintaining also a small footprint of the electronic device in a horizontal plane, to keep the space small which is consumed by the electronic device on a mounting base (such as a PCB mainboard). By a chip-last manufacturing process connecting chip type components (for instance processor, memory) as late as possible during the manufacturing process, high yield at low effort may be achieved.

In an embodiment, the first main surface of the second component is mounted on the first component carrier. When mounted on the first component carrier which is to be mounted, in turn, on a mounting base such as a motherboard PCB, the mechanical connection of the second component may simultaneously also establish a vertically short electrical connection with the first component carrier.

In an embodiment, the first component carrier comprises a connected, in particular laminated, stack comprising at least one electrically conductive layer structure and/or at least one electrically insulating layer structure. In the context of the present application, the term “layer structure” may particularly denote a continuous layer, a patterned layer or a plurality of non-consecutive islands within a common plane. The configuration of the first component carrier as a laminated stack may provide a stable bottom portion of the electronic device as well as providing proper electric connections with low effort and high compactness in vertical direction. Providing the first component carrier as a laminated stack may also allow embedding components therein with small space consumption for further increasing the thickness of the electronic device.

In an embodiment, the first component is embedded in a mold compound on the second component carrier. By encapsulating the first component by molding, the second component carrier may be manufactured with low effort. In particular, a set of first components may be mounted on top of a second set of components to form a single three-dimensional package. Said first and said second components may be at least partially separated by a cavity, i.e. a thermal decoupling gap.

In an embodiment, the second component carrier comprises a connected (in particular laminated) stack comprising at least one electrically conductive layer structure and/or at least one electrically insulating layer structure, wherein the first component is embedded in the stack or is surface mounted on the stack. Thus, the second component carrier may alternatively be provided as a laminated package, for instance a PCB.

In an embodiment, the entire second main surface of the component is exposed with respect to material of the first component carrier and with respect to material of the second component carrier. This may ensure a particularly pronounced thermal decoupling between first component(s) and second component(s).

In an embodiment, at least one of the first component and the second component is a semiconductor chip. Semiconductor chips or dies are particularly thin in a vertical direction and may therefore contribute to the contact design of the electronic device in vertical direction. However, the first and second components may also be other components, such as passive components (for instance manufactured in ceramic technology).

In an embodiment, the first component is a memory chip for storing data. Multiple such memory chips may be arranged side-by-side and/or vertically stacked. Memory chips may be sensitive to overheating, but can be reliably protected against excessive heating from heat generated by a processor type second component by said thermal decoupling gap and/or by an appropriate channelling of heat generated by the second component away from the top side first component(s) and towards a bottom side first component carrier. However, in another embodiment, the first component may be one or more image sensors or any other kind of sensor (for instance a gas sensor) which can be exposed to an environment.

In an embodiment, the second component is a processor chip. Such a processor chip may be a significant heat source during operation of the electronic device. However, such heat may be efficiently removed from the electronic device to a bottom side by one or more redistribution layers and electrically conductive layer structures of the first component carrier. Excessive propagation of such heat upwardly to the one or more first components of the second component carrier may be prevented by the described thermal decoupling gap configuration.

In an embodiment, the second component carrier comprises a recess at a side facing the first component carrier for at least partially accommodating the second component and delimiting the thermal decoupling gap. Such a recess may allow accommodating the second component therein, while maintaining a thermally insulating thermal decoupling gap. Closing (in particular hermetically closing) of such a recess may be accomplished by the first component carrier closing the recess from a bottom side. A correspondingly formed cavity may serve simultaneously for accommodating the second component and for providing the thermal decoupling gap.

In an embodiment, the electronic device comprises a connection body connected between the first component carrier and the second component carrier and having an opening (in particular a through hole, alternatively a blind hole, or a hole to an outside) at least partially accommodating the second component and delimiting or supplementing the thermal decoupling gap. For instance, such a connection body may be manufactured in PCB or substrate technology, i.e. may be a laminate with a central hole. This may allow precisely defining the thermal decoupling gap while simultaneously enabling manufacture of the connection body with low effort. For instance, the connection body may be ring-shaped or annularly shaped.

In an embodiment, the connection body comprises at least one vertical through connection filled with an electrically conductive material and electrically coupling the first component with the second component. Such a vertical through connection may be a copper filled via, in particular formed by laser drilling or mechanically drilling and filled with electrically conductive material by plating. With such one or more vertical through connections, an electric connection between first component carrier, second component carrier and the components may be accomplished without excessive heat flow from the second component to the first component during operation.

In an embodiment, the electronic device comprises a coating (such as a thin film) at least partially coating an exposed surface of the second component. For instance, the coating may comprise a thermally highly conductive coating (such as copper) and/or a protective coating (for instance an anticorrosive coating such as a hydrophobic coating, a migration inhibiting coating, a chemical-resistive or gas-resistive coating, a high breakdown voltage protection coating, an electrostatic discharge (ESD) coating, etc.). For example, an anticorrosive coating may avoid corrosion and chip contamination, for instance in case of an open cavity. By coating the second component with an anticorrosive material, undesired contamination of the second component with moisture may be reliably prevented. The former may promote heat removal from the second component to avoid overheating thereof. Coating the second component with a thermally highly conductive material such as copper may thus allow efficiently removing heat from the second component preferably predominantly via the first component carrier on the bottom side. This may prevent undesired overheating of the second component with low effort.

In an embodiment, at least part of sidewalls of the connection body, which sidewalls delimit the thermal decoupling gap, comprise a coating. Such a coating may be provided additionally or alternatively to a coating of the second component. Coating the sidewalls of the connection body (instead of or in addition to coating the second component itself) may increase the freedom of design of a circuit designer. The coating of the sidewalls of the connection body may be functionalized in a corresponding way as described above for the coating of the second component, i.e. may be in particular a thermally highly conductive coating and/or an anticorrosive coating. For instance, the sidewalls can be a continuous metal ring which aids to improve the thermal performance.

Preferably, an additional metallization may cover sidewall and top of the processor package for a lateral and a sidewall-based heat spreading or heat removal.

In an embodiment, the electronic device comprises at least one third component embedded in the first component carrier. Embedding such at least one further third component in the first component carrier rather than surface mounting at least one additional third component on the first component carrier may contribute to the compact vertical design of the electronic device. Moreover, this may promote a performance improvement, an improvement in terms of power delivery (for instance de-coupling caps), and/or a reliability improvement.

In an embodiment, the third component comprises at least one of the group consisting of a passive component and a power supply controller. For instance, such a passive component may be a capacitor, an inductance, a resistor, an integrated passive device (IPD) or an antenna. A power supply controller may for instance regulate a voltage supply in accordance with requirements of one or more semiconductor dies of the electronic device. It is also possible that the third component is an active component.

In an embodiment, the electronic device comprises one or more fourth components embedded in the above-described connection body. For instance, the fourth component may comprise a passive component, such as a capacitor. With such embodiments, it is possible to efficiently use also otherwise unused regions of the connection body for embedding one or more additional components, to thereby further decrease the space consumption of the device.

In an embodiment, the second component carrier comprises a plurality of first components embedded in and/or surface mounted on the second component carrier. At least part of said first components may be arranged side-by-side, to thereby promote a compact vertical construction of the electronic device. Additionally or alternatively, some of the third components may be stacked (preferably directly stacked), so as to obtain high functionality with limited space consumption.

In an embodiment, the first component carrier comprises at least one pillar (such as at least one copper pillar) at an exposed main surface for establishing and electric connection of the electronic device with a mounting board. Highly advantageously, such a pillar may involve a significantly lower contribution to the vertical thickness of the electronic device than a bulky solder bump. Although a solder bump may be used in other embodiments, accomplishing an electric connection by a pillar (in particular a copper pillar) may be a preferred option for obtaining a compact configuration.

In an embodiment, the first component carrier comprises a redistribution layer on an exposed main surface. Additionally or alternatively, the first component carrier may comprise a further redistribution layer at a main surface facing the second component. Such redistribution layers may fulfil two functions. Firstly, such one or more redistribution layers may redistribute an electric connection structure and may therefore serve for a fan out of signals. In other words, a redistribution layer may be an electrically conductive transfer structure transferring between the smaller dimensions of the chip world and the larger dimensions of the PCB world. Secondly, such one or more redistribution layers may also contribute to heat removal away from the second component (which may be the most significant heat source in an embodiment of the electronic device) and predominantly away from the one or more first components, and may therefore contribute to a bottom side channelling of heat.

In an embodiment, the second component carrier comprises a redistribution layer at a main surface facing the first component carrier. A further redistribution layer on a bottom side of the second component carrier may ensure a proper electric coupling between the first component carrier and the second component carrier, optionally through a connection body.

In an embodiment, at least one of the one or more redistribution layers of the first component carrier may have a volume percentage of copper of at least 1 volume percent, in particular at least 10 volume percent, more particularly at least 50 volume percent. Descriptively speaking, the higher the copper content of the one or more redistribution layers of the first component carrier, the larger the heat removal capability of the respective redistribution layer, since copper has an extraordinarily high capability of conducting heat. With the mentioned significant copper contributions, heat removal from the second component out of the electronic device may be strongly promoted, while simultaneously reducing the risk of overheating of the one or more first components due along a thermal path in an upward direction. In order to obtain said advantageous effects, it may also be advantageous when the first component carrier comprises at least one redistribution layer having an effective thermal conductivity in a horizontal plane in a range from 5 W/mK to 20 W/mK, in particular in a range from 10 W/mK to 15 W/mK. The mentioned values of the thermal conductivity may relate to a homogenized or an averaged thermal conductivity, i.e. an effective thermal conductivity provided by the conductive and non-conductive material. Additionally or alternatively, the first component carrier may comprise at least one redistribution layer having an effective thermal conductivity in a vertical direction in a range from 2 W/mK to 10 W/mK, in particular in a range from 3 W/mK to 8 W/mK. For the avoidance of doubt, the thermal conductivity numbers are just for illustrative purposes. Actual numbers according to embodiments of this invention can also be higher or lower. For example, the thermal conductivity of the redistribution layers may be dominated by copper having a significantly higher value of the thermal conductivity as compared to dielectric laminate materials such as epoxy resin or polyimide. Descriptively speaking, thermal conductivity may be larger in the horizontal plane of the first component carrier as compared to its thickness direction, since a significant portion of the copper material of the redistribution layer may be provided in form of planar patterned copper foils having in many cases a higher amount of copper material as compared to vertical through connections of copper, such as copper filled laser vias.

In an embodiment, the first component carrier comprises a heat removal structure between the first main surface of the second component and an exposed main surface of the first component carrier for removing heat from the second component through the exposed main surface of the first component carrier. Heat can be efficiently removed out of an interior of the electronic device through a well-controlled path in a downward direction, i.e. from the second component towards the first component carrier rather than propagating predominantly upwardly to the first component(s). Descriptively speaking, the thermal decoupling gap may face the second component carrier rather than the first component carrier for this purpose. In particular, the heat removal structure may be formed by at least one electrically unconnected vertical through connection of the first component carrier, filled with a thermally conductive material (such as copper). By such one or more additional thermal vias without electrical function in the bottom processor board an improved heat removal performance may be achieved.

In an embodiment, the method comprises mounting the first main surface of the second component on the first component carrier directly or immediately before connecting the first component carrier with the second component carrier. Thus, a manufacture of the electronic device may be based on a chip-last principle, in particular what concerns the in many cases highly expensive second component.

For instance, the method may comprise coating the second component with a coating after mounting the second component on the first component carrier. For example, coating the second component may be accomplished by sputtering, physical vapor deposition (PVD), chemical vapor deposition (CVD), or any other appropriate deposition process.

In an embodiment, the method comprises connecting the first component carrier and the second component carrier, optionally with a connection body in between, by thermo-compressing. Thermo-compression bonding may correspond to a bonding of two metallic structures which may be brought into atomic contact, in particular by applying force and heat simultaneously. A diffusion which occurs in terms of thermo-compression bonding is promoted by an atomic contact between the surfaces due to an atomic motion. An atomic interaction may stick the interface together. Thermo-compression bonding may be provided by a nonconductive film provided between the two connection surfaces. Correspondingly, the method may comprise connecting the first component carrier and the second component by thermo-compressing.

In an embodiment, the first component carrier and/or the second 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 and/or 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.

In an embodiment, the first component carrier and/or the second 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. A plate-shaped component carrier also ensures short electric connection paths, and therefore suppresses signal distortion during transport.

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

In the context of the present application, the term “printed circuit board” (PCB) may particularly denote a plate-shaped component carrier which is formed by laminating several electrically conductive layer structures with several electrically insulating layer structures, for instance by applying pressure and/or 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, which may for example have 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, land side caps (LSC) and/or die side caps (DSC), 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 particles (such as reinforcing spheres, in particular glass spheres).

The substrate or interposer may comprise or consist of at least a layer of glass, silicon (Si) or a photo-imageable or dry-etchable organic material like epoxy-based build-up material (such as epoxy-based build-up film) or polymer compounds like polyimide, polybenzoxazole, or benzocyclobutene. This may refer to a core and/or to one or more build-up layers.

In an embodiment, any of the above mentioned electrically insulating layer structures 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), cyanate ester, polyphenylene derivate, glass (in particular glass fibers or spheres, multi-layer glass, glass-like materials), prepreg material (such as FR-4 or FR-5), 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 particularly FR4 are usually preferred for rigid PCBs, other materials in particular epoxy-based build-up film or photo-imageable dielectrics may be used as well. For high frequency applications, high-frequency materials such as polytetrafluoroethylene, liquid crystal polymer and/or cyanate ester resins, low temperature cofired ceramics (LTCC) or other low, very low or ultra-low DK-materials may be implemented in the component carrier as electrically insulating layer structure.

In an embodiment, any of the above mentioned electrically conductive layer structures 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, any of the above mentioned electronic components may be 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 optical element (for instance a lens) 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 light emitting diode, a photocoupler, 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, 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, a multiferroic element or a ferrimagnetic element, for instance a ferrite core) or may be a paramagnetic element. However, the component may also be a substrate, an interposer or 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, 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 first component carrier and/or the second 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 and/or heat.

After processing interior layer structures of the first component carrier and/or the second component carrier, it is possible to cover (in particular by lamination) one or both opposing main surfaces of the processed layer structures symmetrically or asymmetrically with one or more further electrically insulating layer structures and/or electrically conductive layer structures. In other words, a build-up may be continued until a desired number of layers is obtained.

After having completed formation of a stack of electrically insulating layer structures and electrically conductive layer structures, it is possible to proceed with a surface treatment of the obtained layers structures or component carrier.

In particular, an electrically insulating solder resist may be applied to one or both opposing main surfaces of the layer stack or component carrier in terms of surface treatment. For instance, it is possible to form such as solder resist on an entire main surface and to subsequently pattern the layer of solder resist so as to expose one or more electrically conductive surface portions which shall be used for electrically coupling the component carrier to an electronic periphery. The surface portions of the component carrier remaining covered with solder resist may be efficiently protected against oxidation or corrosion, in particular surface portions containing copper.

It is also possible to apply a surface finish selectively to exposed electrically conductive surface portions of the component carrier in terms of surface treatment. Such a surface finish may be an electrically conductive cover material on exposed electrically conductive layer structures (such as pads, conductive tracks, etc., in particular comprising or consisting of copper) on a surface of a component carrier. If such exposed electrically conductive layer structures are left unprotected, then the exposed electrically conductive component carrier material (in particular copper) might oxidize, making the component carrier less reliable. A surface finish may then be formed for instance as an interface between a surface mounted component and the component carrier. The surface finish has the function to protect the exposed electrically conductive layer structures (in particular copper circuitry) and enable a joining process with one or more components, for instance by soldering. Examples for appropriate materials for a surface finish are OSP (Organic Solderability Preservative), Electroless Nickel Immersion Gold (ENIG), gold (in particular Hard Gold), chemical tin, nickel-gold, nickel-palladium, etc. Examples for appropriate materials for a surface finish in particular for IC substrates are Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG), Electroless Nickel Immersion Palladium Immersion Gold (ENIPIG) and plated tin. Further examples for appropriate materials for a surface finish in particular for printed circuit boards are nickel-free surface finishes, for instance Electroless Palladium Autocatalytic Gold (EPAG) and Immersion Silber Immersion Gold (ISIG).

