Component carrier and method for producing component carrier

Abstract

The invention relates to a component carrier (1) comprising a stack (2) of a plurality of layers (12) forming at least one electrically conductive layer structure (3) and at least one electrically insulating layer structure (4), said stack (2) comprising a preferably conical cavity (5) wherein the cavity (5) extends through at least two layers (12) of the plurality of layers in a direction (D) perpendicular to a plane (P) in which the layers (12) extend, said cavity (5) being delimited by side walls (6), the side wall (6) is inclined with respect to a direction (D) perpendicular to the plane (P) of the layer (12), and wherein at least one recess (7) is provided in the side wall (6) of the cavity (5), said recess (7) partially breaking the extension of the side wall and partially extending in the stack (2) along the plane extension of the stack (2).

Description

Technical Field

[0001] The present invention relates to a component carrier comprising a stack of a plurality of layers forming at least one conductive layer structure and at least one electrically insulating layer structure, the stack comprising cavities. The present invention also relates to a component carrier assembly and a method for manufacturing a component carrier. Background Art

[0002] JP2020145395A discloses a printed circuit board that achieves a large height difference between a soft or flexible substrate portion and a hard or rigid substrate portion. The rigid substrate portion is connected to the flexible substrate portion and is formed to be thicker than the flexible substrate portion. The manufacturing process of such a printed circuit board includes removing a hard laminate portion to a second barrier layer by a first processing step and then performing a second processing step of removing the hard laminate portion to a first barrier layer to expose the soft laminate portion. The first barrier layer and the second barrier layer are metal layers. The first processing step and the second processing step include laser processing.

[0003] KR20130004650A discloses a method for manufacturing a cavity for an embedded substrate. An insulating layer having reinforcing fibers is cut to form a space. Copper foil layers are laminated on an upper portion and a lower portion of the insulating layer having reinforcing fibers. A lamination molding process is performed by heating and pressing the copper foil. A resin insulating portion is formed by filling the space with resin from the insulating layer. A cavity is formed by performing a laser processing step.

[0004] KR20020009794A discloses a method for manufacturing a multilayer PCB, including forming blind vias. The method includes a step of forming a first printed circuit pattern on a copper-clad laminate by a lithography process and a step of forming a second printed circuit pattern on a substrate by a lithography process. In another step, a blind via is formed by removing resin-coated copper by irradiating a YAG laser to a predetermined portion of the substrate. In a further step, a copper portion is removed by a lithography process, and a resin portion is removed by irradiating a CO 2 laser.

[0005] With the processes of the prior art, as the laser beam energy decreases with increasing depth, only a limited depth can be achieved. In the case of deep cavities, the following disadvantages occur: high surface roughness (of the sidewalls of the cavity) and low precision in depth control and width. Depending on an application, a cavity (such as a sealed cavity completely shielded by copper-coated sidewalls) can act as a waveguide. RF signals can propagate within such a channel. Such a channel is frequency-dependent, meaning that the lower the frequency, the larger the waveguide needs to be (λ / 2). To implement such a waveguide for an RF board (e.g., operating at approximately 70 GHz), the process needs to be adjusted to form deep cavities. For this implementation purpose, the sidewall roughness of the cavity walls is crucial. Summary of the Invention

[0006] The object of the present invention is to overcome the drawbacks of the prior art and to provide a component carrier and a method for manufacturing a component carrier, by means of which a high surface quality and high precision in depth control and width can be achieved. The component carrier should be producible in a reliable and cost-effective manner.

[0007] This object is achieved by a component carrier comprising a stack of a plurality of layers forming at least one conductive layer structure and at least one electrically insulating layer structure, the stack comprising cavities, preferably conical in shape, which extend through at least two of the plurality of layers in a direction perpendicular to the plane in which the layers extend, the cavities being bounded by side walls which are inclined with respect to the direction perpendicular to the plane of the layers, the inclination angle preferably being between 0.5° and 50°, preferably between 0.5° and 30°, more preferably between 1° and 15°, wherein at least one recess is provided in the side walls of the cavities, the recess locally disrupting the extension of the side walls and extending partially in the stack along the plane of the stack.

[0008] The component carrier according to the invention is a direct result of a manufacturing method which can use a laser beam to remove material to form the cavities. Laser drilling is the preferred process for generating the cavities by focusing the laser beam on the material to be removed. One of the objects of the present invention is to form deep and wide cavities. In this case, the laser beam is moved around the circumference of the cavity to form the side walls. The present invention allows the use of a laser beam with a distinct focus, i.e. the cross-section of the beam decreases in the direction towards the intended cut. The degree of inclination of the side walls can be adjusted by the geometry of the laser beam and / or the lateral movement of the laser beam when it penetrates deeper into the stack. Additionally or alternatively, the degree of inclination of the side walls can be adjusted by the emission intensity of the laser beam and / or the pulse rate of the laser beam.

[0009] The inclination of the side walls with respect to the direction perpendicular to the plane of the layers can also have advantageous effects in several applications. One of these is more efficient RF coupling and / or decoupling in the case where the cavities are used as RF waveguides. Additionally, in the case of cooling or heating channels, the inclined shape or extension of the side walls can be advantageous, especially for optimizing the flow of the cooling or heating medium.

[0010] The recesses can originate from a release layer which has been provided in the starting stack. "Locally disrupting the extension of the side walls" means that the recesses locally interrupt the preferably smooth extension of the side walls. The recesses can be in the form of grooves or depressions (or "low spots"). The recesses can, for example, extend circumferentially in the side walls of the cavities. Two or more recesses can also be formed in the side walls of the cavities, preferably each recess extending at a different height level in the stack.

[0011] When forming a cavity, a release layer can be used to separate individual processing (material removal) steps. Then, the material of the release layer can be removed to such an extent that recesses are formed within the sidewalls of the cavity. In combination with the inclination, the recesses not only allow for a reliable manufacturing method but can also be used for other purposes, such as a mechanical fixation structure for a conductive layer that forms a lining of the cavity. Additionally, the recesses can be used to position or fix other components, including (ring-shaped) structures, electronic components, etc.

[0012] In the context of the present application, the term "component carrier" can particularly denote any support structure that is capable of accommodating one or more components thereon and / or therein to provide mechanical support and / or electrical connectivity. In other words, the component carrier can be configured as a mechanical and / or electronic carrier for components. In particular, the component carrier can be one of a printed circuit board, an organic interposer, and an IC (integrated circuit) substrate. The component carrier can also be a hybrid board that combines different types of component carriers among the above-mentioned types of component carriers.

[0013] In the context of the present application, the term "stack" can particularly denote an arrangement of a plurality of planar layer structures that are mounted parallel to each other one above the other.

[0014] In the context of the present application, the term "layer structure" can particularly denote continuous layers, patterned layers, or a plurality of non-continuous islands within a common plane.

[0015] In the context of the present application, the "main surface" of a body can particularly denote one of the two largest opposite surfaces of the body. The main surfaces can be connected by circumferential sidewalls. The thickness of a body (such as a stack) can be defined by the distance between two opposite main surfaces.

[0016] In one embodiment, the 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.

[0017] In the context of the present application, the term "printed circuit board" (PCB) can particularly denote a plate-shaped component carrier formed, for example, by laminating a plurality of conductive layer structures and a plurality of electrically insulating layer structures by applying pressure and / or by supplying thermal energy. As a preferred material for PCB technology, the conductive layer structures are made of copper, while the electrically insulating layer structures can include resin and / or glass fibers, namely so-called prepregs or FR4 materials. By forming holes through the laminate, for example by laser drilling or mechanical drilling, and by partially or completely filling them with a conductive material (in particular copper), the various conductive layer structures can be connected to one another in a desired manner, thereby forming vias or any other through-hole connections. The filled holes connect the entire stack (through-hole connections extending through several layers or the entire stack), or the filled holes connect at least two conductive layers, called vias. Similarly, optical interconnections can be formed through the individual layers of the stack in order to receive an electro-optical circuit board (EOCB). In addition to one or more components that can be embedded in the printed circuit board, the printed circuit board is generally configured to accommodate one or more components on one or both opposite surfaces of the plate-shaped printed circuit board. They can be connected to the respective main surfaces by soldering. The dielectric part of the PCB can be composed of a resin with reinforcing fibers (such as glass fibers).

[0018] In the context of the present application, the term "substrate" can particularly denote a small component carrier. Relative to a PCB, a substrate can be a relatively small component carrier on which one or more components can be mounted, and the substrate can act as a connection medium between one or more chips and another PCB. For example, the substrate can have substantially the same dimensions as the components to be mounted thereon (for example, in the case of a chip-scale package (CSP)). More specifically, a substrate can be understood as a carrier for an electrical connection or electrical network and a component carrier comparable to a printed circuit board (PCB), but the substrate has a relatively high density of laterally and / or vertically arranged connections. Lateral connections are, for example, conductive paths, while vertical connections can be, for example, drilled holes. These lateral and / or vertical connections are provided within the substrate and can be used to provide electrical, thermal, and / or mechanical connections for the accommodated components (in particular IC chips) or non-accommodated components (such as bare die) to the printed circuit board or an intermediate printed circuit board. Thus, the term "substrate" also includes "IC substrate". The dielectric part of the substrate can be composed of a resin with reinforcing particles (such as reinforcing spheres, in particular glass spheres).

[0019] The substrate or the interposer can include at least one layer of or consist of at least one layer of the following materials: glass, silicon (Si), or photoimageable or dry-etchable organic materials such as epoxy-based laminate materials (such as epoxy-based laminate films) or polymer compounds (which may or may not include light- and / or heat-sensitive molecules) such as polyimide or polybenzoxazole.

[0020] In one embodiment, at least one electrically insulating layer structure comprises at least one of the group consisting of the following materials: resins or polymers, such as epoxy resins, cyanate resins, benzocyclobutene resins, bismaleimide triazine resins, polyphenylene derivatives (e.g., based on polyphenylene ether, PPE), polyimides (PI), polyamides (PA), liquid crystal polymers (LCP), polytetrafluoroethylene (PTFE), and / or combinations thereof. Reinforcing structures, such as meshes, fibers, spheres, or other kinds of filler particles, for example made of glass (multilayer glass) can also be used to form composite materials. A semi-cured resin combined with a reinforcing agent, for example a fiber impregnated with one of the above resins, is called a prepreg. These prepregs are often named according to their properties, e.g., FR4 or FR5, which describe their flame-retardant properties. Although prepregs, especially FR4, are often preferred for rigid PCBs, other materials, especially epoxy-based laminate materials (such as laminate films) or photoimageable dielectric materials can also be used. For high-frequency applications, high-frequency materials, such as polytetrafluoroethylene, liquid crystal polymers, and / or cyanate resins can be preferred. In addition to these polymers, low-temperature co-fired ceramics (LTCC) or other low, very low, or ultra-low DK materials can be applied as electrically insulating structures in component carriers.

[0021] In one embodiment, at least one conductive layer structure has at least one of the group consisting of the following materials: copper, aluminum, nickel, silver, gold, palladium, tungsten, and magnesium. Although copper is usually preferred, other materials or their coated forms, especially those coated with superconducting materials or conductive polymers, such as graphene or poly(3,4-ethylenedioxythiophene) (PEDOT) are also possible.

[0022] In one embodiment, the component carrier is a laminated component carrier. In such an embodiment, the component carrier is a composite of a multilayer structure that is stacked and joined together by applying a pressing force and / or heat.

[0023] After processing the internal layer structure of the component carrier, one or more additional electrically insulating layer structures and / or conductive layer structures (especially by lamination) can symmetrically or asymmetrically cover one major surface or the opposite two major surfaces of the processed layer structure. In other words, lamination can be continued until the desired number of layers is obtained.

[0024] After the formation of the stack of the electrically insulating layer structure and the conductive layer structure is completed, the obtained layer structure or component carrier can be surface-treated.

[0025] In particular, in terms of surface treatment, an electrically insulating solder resist can be applied to one major surface or to opposite major surfaces of the layer stack or the component carrier. For example, the solder resist can be formed over the entire major surface and subsequently patterned to expose one or more conductive surface portions that will be used to electrically couple the component carrier to electronic peripherals. Surface portions of the component carrier that remain covered by the solder resist, in particular surface portions containing copper, can be efficiently protected against oxidation or corrosion.

[0026] In terms of surface treatment, a surface modification can also be selectively applied to the exposed conductive surface portions of the component carrier. Such a surface modification can be a conductive covering material on an exposed conductive layer structure (such as pads, conductive traces, etc., in particular including or consisting of copper) on the surface of the component carrier. If the exposed conductive layer structure is not protected, the exposed conductive component carrier material (in particular copper) will oxidize, resulting in a lower reliability of the component carrier. Additionally, the surface modification can be formed, for example, as an interface between a surface-mounted component and the component carrier. The surface modification has the function of protecting the exposed conductive layer structure (in particular the copper circuitry), and the surface modification can be, for example, connected to one or more components by soldering. Examples of suitable materials for the surface modification are organic solderability preservatives (OSP), electroless nickel immersion gold (ENIG), electroless nickel immersion palladium immersion gold (ENIPIG), gold (in particular hard gold), chemical tin, nickel gold, nickel palladium, etc.

[0027] Preferably, the component carrier assembly is a printed circuit board (PCB) and / or a substrate (such as an IC substrate) and / or an interposer.

[0028] Preferably, the conductive layer structure is and / or includes traces, such as horizontal traces and / or vertical traces (vias), and / or a combination of (patterned) traces and / or pads and / or solder areas and / or connection lips.

[0029] According to a preferred embodiment, the cavity has an extension of at least 200 μm, preferably at least 400 μm, more preferably at least 600 μm in a direction perpendicular to the plane in which the layer extends. This can bring the following advantages: the advantage of producing large cavities in an efficient and precise manner in a direction perpendicular to the plane in which the layer extends using the described method. Additionally, the method can give the advantage of very easily adapting the depth of the cavity.

[0030] According to a preferred embodiment, the cavity has a width of at least 300 μm, preferably at least 1000 μm, more preferably at least 2000 μm in a direction parallel to the plane in which the layer extends. This can bring the following advantages, namely, generating a long cavity in a direction parallel to the plane in which the layer extends using the described method, and / or generating a cavity with a large area in the above direction. Additionally, the cavity can provide the precision required for radio frequency and / or high-frequency applications.

[0031] According to a preferred embodiment, the recess has an extension between 2 μm and 350 μm, preferably between 5 μm and 250 μm in a direction perpendicular to the plane in which the layer extends, and / or wherein the recess extends circumferentially around the cavity and / or wherein the recess is arranged at a relative height of 30% to 70%, preferably 40% to 60% of the cavity height from the bottom of the cavity, or in the area of the bottom of the cavity. This can bring the advantage of providing an anchor structure, which improves the integrity of the stack. The anchor structure can be easily and effectively manufactured using the described method, and can provide mechanical stability for the interaction with the conductive layer structure and / or the electrical insulation layer structure.

[0032] According to a preferred embodiment, the recess comprises residues of a material, preferably a material different from the material(s) forming the sidewalls of the cavity, wherein preferably the residues of the material do not contain filler materials, in particular reinforcing materials such as glass fibers. This can bring the advantage of reliable formation of the recess because the material of the recess has different chemical and / or physical properties. The method involved can dispose of a material different from the material(s) forming the sidewalls of the cavity in an easy manner and can achieve precise placement of the material.

[0033] According to a preferred embodiment, the recess is at least partially filled with a material, preferably a material different from one of the material(s) forming the sidewalls of the cavity. This can bring the advantage of imparting mechanical stability from the material forming the sidewalls of the cavity via the at least partially filled material. For example, the conductive layer structure and / or the electrical insulation layer structure can be indirectly adhered to the recess of the cavity via the filler material that at least partially fills the recess.

[0034] According to a preferred embodiment, the recess is at least partially filled with a conductive material, wherein preferably the sidewalls of the cavity are at least partially, preferably completely covered with the conductive material, preferably integrally merged with the conductive material within the recess. This can bring the advantage of guiding electromagnetic signals (such as high-frequency and / or radio signals) through the cavity (with at least one recess) with low losses.

[0035] The conductive material may comprise a metal such as copper or consist of a metal such as copper, or may comprise at least two layers of metal, the metal including copper, titanium, silver, tungsten, chromium, nickel, tin, or oxides or nitrides of the listed metals.

[0036] According to a preferred embodiment, the recess is at least partially filled with an electrically insulating material, where preferably, the electrically insulating material is the same material that also at least partially, preferably completely, covers the sidewalls of the cavity. Preferably, the electrically insulating material (partially filling the recess) does not contain epoxy resin and / or does not contain polyimide and / or does not contain the material forming at least one electrically insulating layer structure. Since the electrically insulating material has a high resistance, e.g., higher than 1000 Ohm / cm, this can bring the advantage of electrically decoupling / insulating the stack from the cavity, especially inside the cavity.

[0037] According to a preferred embodiment, one of the at least one recesses is located at the bottom end of the cavity. An easy and sufficient way to position the recess in the cavity accordingly can be achieved using the described method.

[0038] According to a preferred embodiment, the middle recess of the at least one recess is located at the sidewall of the cavity, between the bottom end and the top end of the cavity. An easy and sufficient way to position the recess in the cavity accordingly can be achieved using the described method.

[0039] According to a preferred embodiment, in a direction perpendicular to the plane in which the layer extends, the at least one recess is at least partially bounded by an electrically insulating layer structure. This fingerprint feature associated with the method can bring the advantage of creating electrical insulation on one side of the cavity.

[0040] According to a preferred embodiment, the sidewall of the cavity is divided into two sidewall portions by the middle recess. This can bring the advantage of more precisely defining the cavity (profile), because the two-step formation of the cavity involved includes another alignment step, which enables higher precision to be achieved.

[0041] According to a preferred embodiment, each of the two sidewall portions is inclined with respect to the direction perpendicular to the plane of the layer, preferably at an inclination angle between 0.5° and 30°, preferably between 1° and 15°, where preferably, the inclination angle α of the first of the two sidewall portions is different from, preferably greater than, the inclination angle β of the second of the two sidewall portions, and where preferably, the difference between the inclination angle α of the first of the two sidewall portions and the inclination angle β of the second of the two sidewall portions is between 0.5° and 10°. This fingerprint feature associated with the manufacturing method can bring the advantage of greater design flexibility in terms of the cavity shape. The related inclination of the sidewall of the cavity may have an impact on the propagation of electrochemical signals and / or the transmission of electrical signals.

[0042] According to a preferred embodiment, one of the two sidewall portions is offset relative to the other of the two sidewall portions in a direction parallel to the plane of the layer. This can have the advantage of enlarging the surface area of the contour of the cavity, and thus this can enhance the integrity of the material in direct contact with the cavity, such as an electrically insulating layer structure or a conductive layer structure, since the higher surface area increases the (overall) adhesion. In another embodiment, the degree of offset of the opposing sidewalls (left sidewall and right sidewall) is different (due to two alignments).

[0043] According to a preferred embodiment, at least two of the plurality of layers are interrupted by a recess orifice, and an annular element is provided in the recess orifice, the annular element defining a cavity with its opening. The annular element can impart higher mechanical stability to the cavity. In addition, the annular element can enable the formation of the recess orifice in an exact manner using the described method.

[0044] According to a preferred embodiment, the material of the annular element is different from the material of the plurality of layers and / or has a homogeneous structure (such as the same material, no filler, etc.). This can have the advantage of having an additional material for fine-tuning the properties of the cavity, in particular the properties of its sidewalls, such as stiffness or dielectric constant.

[0045] This object is also achieved by a component carrier assembly comprising a component carrier according to the invention or an embodiment thereof and at least one electronic component mounted to the component carrier, wherein preferably the electronic component is at least partially embedded in the component carrier, preferably in or adjacent to the cavity, and wherein preferably the electronic component is a transducer for emitting and / or receiving radiation passing through the cavity. This can have the following advantages: the related method is feasible for generating large, deep and / or wide cavities. Thus, components with a large volume can be reliably fully hosted, preferably embedded in the cavity.

[0046] The at least one component can be selected from the group consisting of: a non-conductive inlay, a conductive inlay (such as a metal inlay, preferably comprising copper or aluminum), a heat transfer unit (such as a heat pipe), an optical guiding element (such as an optical waveguide or an optical conductor connection), an electronic component or a combination thereof. The inlay can be, for example, a metal block with or without an insulating material coating (IMS-inlay), which can be embedded or surface-mounted for the purpose of facilitating heat dissipation. Suitable materials are defined according to the thermal conductivity of the material, which should be at least 2 W / mK. Such materials are often based on but not limited to metals, metal oxides and / or ceramics, such as for example copper, aluminum oxide (Al 2 O 3) or aluminum nitride (AlN). To increase the heat exchange capacity, other geometries with an increased surface area are also often used. In addition, the component can be an active electronic component (having at least one pn junction implemented), a passive electronic component, such as a resistor, inductor or capacitor, an electronic chip, a storage device (e.g., DRAM or another data memory), a filter, an integrated circuit (such as a field programmable gate array (FPGA), programmable array logic (PAL), generic array logic (GAL) and complex programmable logic device (CPLD)), a signal processing component, a power management component (such as a field effect transistor (FET), metal oxide semiconductor field effect transistor (MOSFET), complementary metal oxide semiconductor (CMOS), junction field effect transistor (JFET) or insulated-gate field effect transistor (IGFET), all based on semiconductor materials, such as silicon carbide (SiC), gallium arsenide (GaAs), gallium nitride (GaN), gallium oxide (Ga 2 O 3 )), indium gallium arsenide (InGaAs) and / or any other suitable inorganic compound), an optoelectronic interface element, a light-emitting diode, an optocoupler, a voltage converter (e.g., a DC / DC converter or an AC / DC converter), a cryptographic component, a transmitter and / or a receiver, an electromechanical transducer, a sensor, an actuator, a microelectromechanical system (MEMS), a microprocessor, a capacitor, a resistor, an inductor, a battery, a switch, a camera, an antenna, a logic chip and an energy harvesting unit. However, other components can also be embedded in the component carrier. For example, a magnetic element can be used as a component. Such a magnetic element can be a permanent magnetic element (such as a ferromagnetic element, an antiferromagnetic element, a multiferroic element or a ferrimagnetic element, e.g., a ferrite core) or can be a paramagnetic element. However, the component can also be an IC substrate, an interposer or another component carrier, for example, in a board-in-board configuration. The component can be surface-mounted on the component carrier and / or can be embedded inside the component carrier. In addition, other components, especially components that generate and emit electromagnetic radiation and / or are sensitive to electromagnetic radiation propagating from the environment, can also be used as components.

[0047] Preferably, the electronic component is and / or includes a chip and / or an integrated circuit (IC). The electronic component can be an active device, but can also be a passive device, such as a capacitor, an inductor or a resistor or a combination thereof.

[0048] This object is also achieved by a method for manufacturing a component carrier, the method comprising the following steps:

[0049] (a) Providing a stack of a plurality of layers forming at least one conductive layer structure and at least one electrically insulating layer structure, the stack further comprising at least one release layer extending at least partially within the stack, and

[0050] (b) A cavity is formed within the stack by removing material, preferably the material of at least two of the plurality of layers or locally replacing the plugging material of the layers in the plurality of layers, along a direction transverse to, preferably perpendicular to, the plane in which the layer extends, until the release layer is released, such that the cavity is bounded by sidewalls that are inclined with respect to a direction perpendicular to the plane of the layer.

[0051] (c) At least a portion of the release layer is removed such that at least one recess is formed in the sidewall of the cavity, and the recess locally disrupts the sidewall extension.

[0052] In a preferred embodiment, at least a portion of the (one or more original) release layer remains in the manufactured component carrier (i.e., in the final product), although preferably the major portion of the release layer has been removed during the manufacturing process.

[0053] In one embodiment, the release layer can be formed of a composite material having hydrophobic properties and optionally hydrophilic properties. When subjected to heat treatment and / or UV / Vis radiation exposure, the material of the release layer can change its properties. It can be formed of a mixture of at least a release agent based on metal soap, an adhesive, and a solvent, wherein the metal of the metal soap can include Al, Mg, Ca, Na, and / or Zn.

[0054] The properties of the release layer can be such that it can be removed, for example, by a solvent such as water and / or an organic material during fluid handling. Additionally or alternatively, it can be removed during a plasma treatment process.

[0055] According to a preferred embodiment, step (b) is performed by laser cutting along the profile of the resulting sidewall.

[0056] According to a preferred embodiment, step (b) includes the following sub-steps:

[0057] (b1) The material of the first portion of the stack is removed to a first depth, wherein preferably the first depth is defined by an intermediate release layer, and

[0058] (b2) After step (b1), the material of the second portion of the stack is removed to a second depth, wherein preferably the second depth is defined by another release layer, preferably a bottom release layer. This can have the advantage of more precisely defining the cavity (profile) because the two-step formation of the cavity involved includes another alignment step, which enables higher precision to be achieved.

[0059] According to a preferred embodiment, sub-steps (b1) and (b2) are performed by laser cutting, wherein the geometry of the laser beam for sub-step (b1) is different from the geometry of the laser beam for sub-step (b1), wherein preferably, the focus of the laser beam is adjusted between sub-steps (b1) and (b2), preferably automatically, and wherein preferably, the laser beam is focused on the top layer of the stack for sub-step (b1) and on a first depth for sub-step (b2). This can have the advantage of adjusting the tilt angles α and β of the sidewalls of the cavity to desired values. The geometry of the cavity may have an impact on the transmission of electrical signals and / or the propagation of electromagnetic waves and can be easily adjusted according to actual needs.

[0060] The object of the present invention is to form a deep cavity for use as a signal transmission channel, such as a waveguide. The waveguide can be regarded as a sealed cavity completely shielded by copper-coated sidewalls. RF signals can propagate within such a channel. Such a channel is frequency-dependent, meaning that the lower the frequency, the larger the waveguide needs to be (λ / 2). In order to implement such a waveguide for an RF board operating at frequencies greater than 60 GHz and preferably below 200 GHz, the conventional 2.5D® process needs to be adjusted to form a deep cavity. For this implementation purpose, the sidewall roughness of the cavity walls is crucial. The proposed process flow allows the fabrication of waveguides with appropriate depth and sidewall roughness. The potential use of such a cavity can be extended, for example, if filled with a cooling medium to be used as a thermal cooling channel.

[0061] The object of the present invention is to form a deep cavity. With the prior art process, only a limited depth can be achieved as the energy of the laser beam decreases with increasing depth. Therefore, a split process route including a plurality of release layers is proposed, wherein the first cavity is cut with a laser until the first release layer. Thereafter, the incision (cap) will be removed. Then the layer below the cap will be used as a new registration / focus layer. The tool in the laser programming can be focused on the new height level to reduce the loss of the laser beam. With this new focus of the laser beam, the second stage can perform smooth laser cutting. The second laser cutting can be distinguished, for example, by the recess in the final product from the initial laser cutting.

[0062] The prior art cavity forming is done with lasers, including 2.5D technology. For deep cavities, mechanical routing can be used, but it has the following disadvantages: high surface roughness, low depth control, and low width accuracy.

[0063] During drilling, the energy of the laser beam decreases with the cavity depth. By the proposed method, it is possible to increase the energy-induced production of the laser beam (re-adjusting the laser beam focus after the initial laser drilling step). In addition, by dividing the drilling process into at least two steps (more than two are possible), it is allowed to control the hole diameter at different heights, for example, reducing the access diameter from the second drilling step.

[0064] With an optimized energy balance (reduced occupied area), it is possible to form deep laser accesses with different diameters and the ability to drill the most important holes.

[0065] The drilled holes must be reliably used as waveguides, which requires ensuring the complete removal of the material from the drilled holes, and the drilled holes will be removed as a complete structure.

[0066] According to a preferred embodiment, step (c) is carried out by at least partially removing the material of the release layer with a solvent. This can produce recesses that are at least partially filled with an electrically insulating material. Since the electrically insulating material has a high resistance, for example, higher than 1000 Ohm / cm, this can bring the advantage of electrically decoupling / insulating the stack from the cavity, especially inside the cavity.

[0067] For a better understanding of the present invention, the present invention will be explained in more detail with the aid of the following drawings. Brief Description of the Drawings

[0068] The following is shown in a highly simplified schematic diagram:

[0069] Figure 1 is an embodiment of a component carrier;

[0070] Figure 2 is another embodiment of a component carrier having an offset between sidewall portions;

[0071] Figures 3 to 6 is an embodiment of a method for manufacturing a component carrier;

[0072] Figure 7 is an embodiment of a component carrier during the manufacturing process;

[0073] Figure 8 is another embodiment of a component carrier having a conductive material in the recess and on the sidewalls of the cavity;

[0074] Figure 9 is another embodiment of a component carrier. Detailed Description of the Invention

[0075] As an introduction, it should be noted that in the embodiments described in different ways, the same parts or method steps are indicated by the same reference signs or the same component names; at the same time, the disclosure contained in the entire description can be similarly applied to the same parts with the same reference signs or the same component names. In addition, the positional indications selected in the description, such as at the top, bottom, lateral, etc., refer to the drawings directly shown and described; and if the position changes, the positional indication will be similarly applied to the new position.

[0076] The embodiments show possible variants; however, in this regard, it should be noted that the present invention is not limited to the specifically shown variants; on the contrary, various combinations of the various variants are possible, and due to the technical information provided by the present invention, the possibility of such variants is within the skills of those skilled in the art.

[0077] The scope of protection is determined by the claims. However, the description and the drawings will be used to interpret the claims. Each feature or combination of features from the different embodiments shown and described can itself constitute an independent solution according to the present invention. The fundamental purpose of the independent solution according to the present invention can be gathered from the description.

[0078] Any indication of a range of values in this specification should be understood to include any and all sub-ranges thereof; for example, an indication of 1 to 10 should be understood to include all sub-ranges starting from the lower boundary 1 to the upper boundary 10; that is, all sub-ranges start with a lower boundary of 1 or greater and stop at an upper boundary of 10 or less, such as 1 to 1.7 or 3.2 to 8.1 or 5.5 to 10.

[0079] For the sake of orderliness, one last point should also be noted: For better understanding, some of the facts shown in the figures are not shown to scale and / or are enlarged and / or reduced in size.

[0080] Figure 1 and Figure 2 An embodiment of a component carrier 1 is shown, which component carrier 1 comprises a stack 2 of a plurality of layers 12 forming at least one conductive layer structure 3 and at least one electrically insulating layer structure 4. The stack 2 comprises a cavity 5 which is preferably conical, wherein the cavity 5 extends through at least two of the plurality of layers 12 in a direction D perpendicular to the plane P in which the layers 12 extend. The cavity 5 is bounded by side walls 6 which are inclined with respect to the direction D perpendicular to the plane P of the layers 12. The corresponding angle of inclination can be between 0.5° and 50°, preferably between 0.5° and 30°, more preferably between 1° and 15°. Additionally and / or alternatively, at least a part of the side walls 6 can be perpendicular to the plane P (i.e., without inclination).

[0081] In an example, the conductive layer structure 3 may include copper, nickel, or tin. Additionally and / or alternatively, the conductive layer structure 3 may include palladium, silver, gold, tungsten, chromium, or a combination thereof. In another example, the conductive layer structure 3 may include carbon (such as graphene) or a conductive polymer (such as poly(3,4-ethylenedioxythiophene) (PEDOT)). The electrically insulating layer structure 4 may include an organic polymer, such as an epoxy resin, a cyanate resin, a benzocyclobutene resin. Additionally and / or alternatively, the electrically insulating layer structure 4 may include an inorganic material, such as glass in the form of spheres, fibers, or plate-like structures, or ceramics in the form of spheres, fibers, or plate-like structures. Furthermore, the component carrier 1 may include a printed circuit board (PCB), an (IC) substrate, or an interposer.

[0082] In Figure 1 and Figure 2 the embodiment of, at least one of the two recesses 7 (at different height levels) is provided in the sidewall 6 of the cavity 5. The recess 7 locally disrupts the extension of the sidewall and extends partially within the stack 2 along the plane extension of the stack 2.

[0083] Preferably, the cavity 5 has an extension of at least 200 μm, preferably at least 400 μm, more preferably at least 600 μm in a direction D perpendicular to the plane P in which the layer 12 extends. Alternatively, the extension of the cavity 5 in the direction D perpendicular to the plane P may be in the range from 50 μm to 200 μm. Further preferably, the cavity 5 has a width of at least 300 μm, preferably at least 1500 μm, more preferably at least 2000 μm in a direction parallel to the plane P in which the layer 12 extends. Alternatively, the extension of the cavity 5 in the direction parallel to the plane P may be in the range from 70 μm to 300 μm.

[0084] The recess 7 may have an extension between 2 μm and 350 μm, preferably between 5 μm and 250 μm, in a direction D perpendicular to the plane P in which the layer 12 extends. The recess 7 may circumferentially surround the cavity 5. Preferably, the recess 7 is arranged at a level at a distance from the bottom of the cavity of 30% to 70%, preferably 40% to 60% of the height of the cavity 5. In Figure 1 and Figure 2 the embodiment of, the recess is arranged at the middle height of the cavity 5. Another recess 7 is arranged in the bottom region of the cavity 5. In an example, at least a part of at least one recess 7 may have a concave shape. Alternatively, at least another part of at least one recess 7 may have a convex shape. The shape of the recess 7 may have an impact on the mechanical stability of the recess, and thus it may be possible to form a cavity extending perpendicular to the plane by more than 300 µm, especially 400 µm.

[0085] In the following, and before discussing further embodiments of the component carrier, a method for manufacturing a component carrier 1 will be described with the aid of Figures 3 to 6 The method comprises at least the following steps:

[0086] (a) Providing a stack 2 of a plurality of layers 12 forming at least one conductive layer structure 3 and at least one electrically insulating layer structure 4, the stack 2 further comprising at least one release layer 9 extending at least partially within the stack 2, and

[0087] (b) Forming a cavity 5 within the stack 2 by removing material, preferably removing the material of at least two of the plurality of layers 12 (see the embodiment of Figures 3 to 6 ) or locally replacing the plugging material 13 of the layers of the plurality of layers 12 (see the embodiment of Figure 7 ) along a direction D transverse to, preferably perpendicular to, the plane P in which the layers 12 extend, until the release layer 9, such that the cavity 5 is bounded by sidewalls 6 which are inclined with respect to the direction D perpendicular to the plane P of the layers 12,

[0088] (c) Removing at least a part of the release layer 9 such that at least one recess 7 is formed in the sidewalls 6 of the cavity 5, the recess 7 locally disrupting the sidewall extension.

[0089] As can be seen from Figure 1 and Figure 2 , the release layer(s) 9 is depicted as an entire layer (i.e., extending over most or even the entire component carrier 1). However, in an alternative preferred embodiment, the release layer(s) 9 extends only locally in the region where the cavity will be produced (see Figures 3 to 6 ).

[0090] Step (b), i.e., forming the cavity, can be carried out by means of at least one laser, such as a CO 2 laser or a UV laser or a UV-CO 2 laser. For example, a red laser or a green (UV) laser (e.g., having a wavelength of 532 nm and / or 515 nm and, for example, a power of 2 - 20 watts) can be used.

[0091] Preferably, step (b) is carried out by laser cutting 10 along the contour of the resulting sidewalls 6. As indicated in Figure 3 , a focused laser beam 11 is used to carry out a circumferential cut which defines the sidewalls 6 of the resulting cavity 5.

[0092] In the particular embodiment shown in Figures 3 to 6 , step (b) comprises the following sub-steps:

[0093] (b1) Remove the material of the first part of stack 2 to a first depth. The first depth can be defined by an intermediate (first) release layer 9 embedded in stack 2 (the release layer 9 can be located, for example, on top of the electrical insulation layer structure or on top of the conductive layer structure).

[0094] (b2) After step (b1): Remove the material of the second part of stack 2 to a second depth. The second depth can be defined by another (second) release layer 9 embedded in stack 2 (again, the other release layer 9 can be located, for example, on top of the electrical insulation layer structure or on top of the conductive layer structure). The other release layer 9 can form the bottom release layer defining the total depth of cavity 5.

[0095] In a preferred embodiment, if the conductive layer is located below the release layer 9, the laser stops its operation during step (b) because the laser beam may be reflected and the laser tool recognizes the reflection.

[0096] Sub-steps (b1) and (b2) can be carried out by laser cutting 10, where the geometry of the laser beam 11 for sub-step (b1) is different from the geometry of the laser beam 11 for sub-step (b2). Preferably, the focus of the laser beam 11 is adjusted between sub-step (b1) and sub-step (b2), preferably automatically. The laser beam 11 can be focused on the top layer of stack 2 for sub-step (b1) and on the first depth for sub-step (b2). The first depth corresponds to the height of the intermediate (first) release layer 9.

[0097] Step (c), i.e., the formation of recess 7, can be carried out by at least partially removing the material of the release layer 9 with a solvent.

[0098] Another embodiment of component carrier 1 is characterized in that the recess 7 comprises residues of the material (of the release layer 9), preferably the material is different from the material(s) forming the sidewalls 6 of cavity 5, where preferably the residues of the material do not contain filler material.

[0099] In another embodiment, the recess 7 is at least partially filled with a material, preferably the material is different from one of the material(s) forming the sidewalls 6 of cavity 5.

[0100] In Figure 8 a highly preferred embodiment as shown in, the recess 7 is at least partially filled with a conductive material 8, where preferably the sidewalls 6 are at least partially, preferably completely, covered with the conductive material 8. As already mentioned at the beginning, a cavity shielded by a conductive material (such as a copper-coated sidewall) can be used as a waveguide for RF applications. The recess 7 can be used as a mechanical and / or electrical connection to this shield.

[0101] Alternatively, the recess 7 may be at least partially filled with an electrically insulating material, preferably the same material that also at least partially, preferably completely, covers the sidewalls 6 of the cavity 5. Such an embodiment may be useful if, for example, the cavity 5 is used to direct a cooling medium to a location within or near the stack 2.

[0102] As Figures 1 to 6 shown, one of the recesses in at least one recess 7 may be located at the bottom end of the cavity 5. The intermediate recess of at least one recess 7 may be located at the sidewall 6 of the cavity 5, between the bottom end and the top end of the cavity 5.

[0103] The sidewall 6 of the cavity 5 may be divided into two sidewall portions 6a, 6b by the intermediate recess 7. In Figure 1 and Figure 2 it is indicated that the two sidewall portions 6a, 6b are each inclined with respect to the direction D perpendicular to the plane P of the layer 12, preferably with the inclination angles α, β between 0.5° and 50°, preferably between 0.5° and 30°, more preferably between 1° and 15°.

[0104] The inclination angle α of the first of the two sidewall portions 6a, 6b may be different from the inclination angle β of the second of the two sidewall portions 6a, 6b, preferably greater than the inclination angle β. As already mentioned above, such a geometric configuration can be achieved by using different geometries (different foci) of the laser beam 11 during the laser cutting 10 through the sub-steps (b1) and (b2). The difference between the inclination angle α of the first of the two sidewall portions 6a, 6b and the inclination angle β of the second of the two sidewall portions 6a, 6b is between 0.5° and 10°.

[0105] The different inclination angles are a direct result of dividing the process into sub-steps (b1) and (b2). Such a process may include a plurality of release layers, where the first cavity portion will be cut with a laser beam until the first release layer. After that, the incision (cap) will be removed. Then, the release layer under the removed cap will be used as a new registration / focusing layer. The tool in the laser programming can be focused at a new height level to reduce laser beam loss. With this new focus of the laser beam, the second stage can be a smoother laser cutting. The first laser cutting and the second laser cutting can be distinguished, for example, by the intermediate recess 7 in the final product.

[0106] Figure 2An embodiment is shown, according to which one of two sidewall portions 6a, 6b, namely 6b, is offset relative to the other 6a of the two sidewall portions 6a, 6b in a direction parallel to the plane P of the layer 12. The recesses 7 in the intermediate region and the bottom region can still be seen. As already mentioned previously, the offset provided in the first (e.g., left) sidewall can be different from the offset provided in the second (e.g., right) sidewall opposite the first sidewall.

[0107] At least one recess 7 in a direction D perpendicular to the plane P in which the layer 12 extends can be at least partially bounded by the electrically insulating layer structure 4.

[0108] Figure 7 Another embodiment of the component carrier is shown. Here, at least two of the plurality of layers 12 are interrupted by recess openings 15, and an annular element 14 is provided in the recess openings 15, and the annular element 14 defines a cavity 5 through its opening. The material of the annular element 14 can be different from the material of the plurality of layers 12 and / or can have a homogeneous structure. Such an embodiment can be achieved if the encapsulating material 13 locally replaces the layers in the plurality of layers 12. A cut is made in the encapsulating material 13 (see Figure 7 ), and the central portion of the encapsulating material 13 is removed. Then, the remaining portion of the encapsulating material 13, namely the annular element 14, forms the sidewall 6 of the cavity 5.

[0109] Alternatively, the annular element 14 can include a heterogeneous structure that includes filler materials, such as inorganic particles (glass, ceramic, carbon, pigment).

[0110] Of course, the present invention also relates to a component carrier assembly that includes a component carrier 1 according to one of the preceding claims and at least one electronic component mounted to the component carrier 1. The electronic component can be at least partially embedded within the component carrier 1, preferably within the cavity 5 or adjacent to the cavity 5. The electronic component can be, for example, an (RF) transducer for transmitting and / or receiving (e.g., RF) radiation through the cavity 5.

[0111] As can be seen, for example, from Figure 8 and Figure 9 in the final product, a part of the original release layer 9 can still be present in the manufactured component carrier, for example, between the electrically insulating layer structure 4 and the conductive layer structure 3. The term "original release layer" is understood to be a release layer that is provided within the initial stack but has been partially removed through the process. List of reference numerals

[0112] 1 Component carrier

[0113] 2 Stack

[0114] 3 Conductive layer structure

[0115] 4 Electrical insulation layer structure

[0116] 5 Cavity

[0117] 6 Side wall

[0118] 6a First side wall portion

[0119] 6b Second side wall portion

[0120] 7 Recess

[0121] 8 Conductive material

[0122] 9 Release layer

[0123] 10 Laser cutting

[0124] 11 Laser beam

[0125] 12 Layer

[0126] 13 Sealing material

[0127] 14 Annular element

[0128] 15 Recess orifice

[0129] α Inclination angle of the first side wall portion 6a

[0130] β Inclination angle of the second side wall portion 6b

[0131] D Direction perpendicular to the plane P in which the layer 12 extends

[0132] P Plane in which the layer 12 extends

Claims

1. A component carrier (1) comprising a stack (2) of a plurality of layers (12) forming at least one electrically conductive layer structure (3) and at least one electrically insulating layer structure (4), the stack (2) comprising a preferably conical cavity (5), wherein the cavity (5) extends through at least two of the plurality of layers (12) in a direction (D) perpendicular to a plane (P) in which the layers (12) extend, the cavity (5) being delimited by side walls (6), the side walls (6) being inclined at an angle of inclination relative to the direction (D) perpendicular to the plane (P) of the layers (12), the angle of inclination preferably being between 0.5° and 50°, preferably between 0.5° and 30°, more preferably between 1° and 15°, wherein at least one recess (7) is arranged in the side walls (6) of the cavity (5), the recess (7) locally disrupting the side wall extension and extending in the stack (2) partially along the planar extension of the stack (2).

2. The component carrier according to claim 1, wherein: The cavity (5) has an extension of at least 200 µm, preferably at least 400 µm, more preferably at least 600 µm in a direction (D) perpendicular to the plane (P) in which the layer (12) extends.

3. The component carrier according to claim 1 , wherein: The cavity (5) has a width in a direction parallel to the plane (P) in which the layer (12) extends of at least 300 µm, preferably at least 1500 µm, more preferably at least 2000 µm.

4. The component carrier according to claim 1, wherein: The recess (7) has an extension in a direction (D) perpendicular to the plane (P) in which the layer (12) extends of between 2 μm and 350 μm, preferably between 5 μm and 250 μm, and / or wherein, The recess (7) extends circumferentially around the cavity (5), and / or the recess (7) is arranged at a level at a distance from the bottom of the cavity of 30% to 70%, preferably 40% to 60% of the height of the cavity (5), or is arranged in the area of ​​the bottom of the cavity (5).

5. The component carrier according to claim 1, wherein: The recess (7) comprises a remnant of a material, preferably a material different from the material forming the side wall (6) of the cavity (5), wherein preferably the remnant of material is free of filler material.

6. The component carrier according to claim 1, wherein: The recess (7) is at least partially filled with a material, preferably a material different from one of the materials forming the side walls (6) of the cavity (5).

7. The component carrier according to claim 1, wherein: The recess (7) is at least partially filled with an electrically conductive material (8), wherein preferably the side wall (6) of the cavity (5) is at least partially, preferably completely, covered by the electrically conductive material (8).

8. The component carrier according to claim 1, wherein: The recess (7) is at least partially filled with an electrically insulating material, wherein preferably the electrically insulating material is the same material which also at least partially, preferably completely, covers the side walls (6) of the cavity (5).

9. The component carrier according to claim 1, wherein: One of the at least one recess (7) is located at the bottom end of the cavity (5).

10. The component carrier according to claim 1, wherein: The middle recess of the at least one recess (7) is located at the side wall (6) of the cavity (5), between the bottom end of the cavity (5) and the top end of the cavity (5).

11. The component carrier according to claim 1, wherein: The at least one recess (7) is at least partially delimited by the electrically insulating layer structure (4) in a direction (D) perpendicular to the plane (P) in which the layer (12) extends.

12. The component carrier according to claim 1, wherein: The side wall (6) of the cavity (5) is divided into two side wall parts (6a, 6b) by the middle recess (7).

13. The component carrier according to claim 1, wherein: The two side wall portions (6a, 6b) are each inclined at an inclination angle relative to a direction (D) perpendicular to a plane (P) of the layer (12), preferably the inclination angle (α, β) is between 0.5° and 50°, preferably between 0.5° and 30°, more preferably between 1° and 15°, wherein preferably, the inclination angle (α) of the first side wall portion (6a) of the two side wall portions (6a, 6b) is different from, preferably greater than, the inclination angle (β) of the second side wall portion (6b) of the two side wall portions (6a, 6b), wherein preferably, the difference between the inclination angle (α) of the first side wall portion (6a) of the two side wall portions (6a, 6b) and the inclination angle (β) of the second side wall portion (6b) of the two side wall portions (6a, 6b) is between 0.5° and 10°.

14. The component carrier according to claim 12 or 13, wherein: One of the two side wall portions (6a, 6b) is offset relative to the other of the two side wall portions (6a, 6b) in a direction parallel to the plane (P) of the layer (12).

15. The component carrier according to one of the preceding claims, wherein At least two of the plurality of layers (12) are interrupted by a recessed aperture (15), and an annular element (14) is arranged in the recessed aperture (15), the annular element (14) defining the cavity (5) through its opening.

16. The component carrier according to claim 15, wherein: The material of the annular element (14) is different from the material of the plurality of layers (12) and / or has a homogenous structure.

17. A component carrier assembly, comprising a component carrier (1) according to one of the preceding claims and at least one electronic component mounted to the component carrier (1), wherein preferably, the electronic component is at least partially embedded in the component carrier, preferably embedded in or adjacent to the cavity (5), wherein preferably, the electronic component is a transducer for emitting and / or receiving radiation passing through the cavity (5).

18. A method for producing a component carrier (1), preferably according to one of the preceding claims, comprising the following steps: (a) providing a stack (2) of a plurality of layers (12) forming at least one electrically conductive layer structure (3) and at least one electrically insulating layer structure (4), the stack (2) further comprising at least one release layer (9) extending at least partially within the stack (2), and (b) forming a cavity (5) in the stack (2) by removing material, preferably material of at least two of the plurality of layers (12) or blocking material (13) partially replacing a layer of the plurality of layers (12), in a direction transverse to, preferably perpendicular to, the plane (P) in which the layer (12) extends, until the layer (9) is released, so that the cavity (5) is delimited by side walls (6) which are inclined with respect to a direction (D) perpendicular to the plane (P) of the layer (12), (c) removing at least a portion of the release layer (9) so that at least one recess (7) is formed in the side wall (6) of the cavity (5), the recess (7) locally disrupting the side wall extension.

19. The method according to claim 18, wherein: Step (b) is performed by laser cutting (10) along the contour of the resulting side wall (6).

20. The method according to claim 18 or 19, wherein: Step (b) comprises the following sub-steps: (b1) removing material of a first portion of the stack (2) to a first depth, wherein preferably the first depth is defined by an intermediate release layer (9), and (b2) After step (b1 ), removing material of a second portion of the stack (2) to a second depth, wherein preferably the second depth is defined by a further release layer (9), preferably a bottom release layer.

21. The method according to claim 20, wherein: Sub-steps (b1) and (b2) are performed by laser cutting (10), wherein the geometry of the laser beam (11) used for sub-step (b1) is different from the geometry of the laser beam (11) used for sub-step (b2), wherein preferably the focus of the laser beam (11) is adjusted between sub-steps (b1) and (b2), preferably automatically, wherein preferably the laser beam (11) is focused on the top layer of the stack (2) for sub-step (b1) and on the first depth for sub-step (b2).

22. The method according to any one of claims 18 to 21, wherein: Step (c) is performed by at least partially removing the material of the release layer (9) with a solvent.

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