Manufacturing holes in component carrier material

A method includes providing an electrically conductive layer structure on top of an electrically insulating layer structure, forming a window in the electrically conductive layer structure and removing material of the electrically insulating layer structure below the window by a first laser beam, and subsequently removing further material of the electrically insulating layer structure below the window by a second laser beam having a smaller size than a size of the window.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Chinese Patent Application No. 201910101368.X filed on 31 Jan. 2019, the disclosure of which is hereby incorporated herein by reference.

TECHNICAL FIELD

Embodiments of the invention relate to a component carrier and a method of manufacturing a component carrier.

Technological Background

In the context of growing product functionalities of component carriers equipped with one or more electronic components and increasing miniaturization of such components as well as a rising number of components to be mounted on the component carriers such as printed circuit boards, increasingly more powerful array-like components or packages having several components are being employed, which have a plurality of contacts or connections, with ever smaller spacing between these contacts. Removal of heat generated by such components and the component carrier itself during operation becomes an increasing issue. At the same time, component carriers shall be mechanically robust and electrically reliable so as to be operable even under harsh conditions. All these requirements go hand in hand with a continued miniaturization of component carriers and their constituents.

Moreover, it may be advantageous to efficiently contact electrically conductive layer structures and/or components embedded in a component carrier with proper quality. Formation of mechanical vias and laser vias, which may be copper filled, may be advantageous for this and other purposes.

SUMMARY

There may be a need to form a laser hole for a component carrier with high quality and efficiency.

According to an exemplary embodiment of a first aspect, a method is provided which comprises providing an electrically conductive layer structure on top of an electrically insulating layer structure, forming a window in the electrically conductive layer structure and removing material of the electrically insulating layer structure below the window by a first laser beam, and subsequently removing further material of the electrically insulating layer structure below the window by a second laser beam having a smaller size than the window.

According to an exemplary embodiment of a second aspect, a method is provided which comprises providing an electrically conductive layer structure on an electrically insulating layer structure, and forming a window in the electrically conductive layer structure and removing material of the electrically insulating layer structure below the window by a laser beam which is configured for promoting heat transfer in the electrically conductive layer structure in horizontal direction and is configured for inhibiting heat transfer in vertical direction.

According to an exemplary embodiment of a third aspect, a component carrier is provided which comprises an electrically insulating layer structure, an electrically conductive layer structure on top of the electrically insulating layer structure, a window in the electrically conductive layer structure, a recess in the electrically insulating layer structure below the window, wherein an overhang of the electrically conductive layer structure with respect to the electrically insulating layer structure at an edge of the window is smaller than or equal to 10 μm, and an electrically conductive material in at least part of the recess.

According to an exemplary embodiment of a fourth aspect, a component carrier is provided which comprises an electrically insulating layer structure, an electrically conductive layer structure on a front side of the electrically insulating layer structure having a window, another electrically conductive layer structure on a back side of the electrically insulating layer structure having another window, and a through hole extending through the electrically insulating layer structure and being at least partially filled with electrically conductive material, wherein the through hole is formed by a recess extending from the window into the electrically insulating layer structure and another recess connected to the recess and extending from the other window into the electrically insulating layer structure, wherein different portions of the recess taper with different steepness, and wherein different portions of the other recess taper with different steepness.

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 “layer structure” may particularly denote a continuous layer, a patterned layer or a plurality of non-consecutive islands within a common plane.

In the context of the present application, the term “window” may particularly denote a through hole, in particular a circular through hole, extending through an electrically conductive layer structure as a result of a laser treatment of this electrically conductive layer structure. Descriptively speaking, the energy of the laser beam may remove material of the electrically conductive layer structure in the region of the window.

In the context of the present application, the term “size” of a window and a first or a second laser beam, respectively, may particularly denote a maximum diameter of the preferably circular window and a maximum diameter of the preferably circular first or second laser beam, respectively.

In the context of the present application, the term “configuring a laser beam for promoting heat transfer in horizontal direction and inhibiting heat transfer in vertical direction” may particularly denote that at least one parameter characterizing the laser beam, in particular its energy and/or its operating point, is adjusted so that the heat of the laser energy propagates with a larger or major amount (in particular more than 50% of the laser energy, more particularly more than 80% of the laser energy) in a horizontal direction along the extension of the electrically conductive layer structure rather than vertically into material of the electrically insulating layer structure below. Thus, only a smaller or minor amount (in particular less than 50% of the laser energy, more particularly less than 20% of the laser energy) of the laser energy may propagate vertically.

In the context of the present application, the term “overhang” may particularly denote a length of the electrically conductive layer structure directly adjacent to the window over which length the respective portion of the electrically conductive layer structure hangs freely in a cantilever fashion spaced with regard to the electrically insulating layer structure and is not supported from below by material of the electrically insulating layer structure along the extension of the overhang. What concerns the above statement that overhanging material may be locally not supported, it should be said that the overhang may relate to the substantially resin free area beneath the respective electrically conductive layer structure. However, a person skilled in the art will understand that some residue resin might be present within a gap relating to the overhang. In order to quantitatively determine or measure the value of the overhang, the length of the substantially resin-free (wherein resin may refer to the electrically insulating layer structure) undercut directly under an overhanging electrically conductive layer structure may be measured (in particular even if it is not the most receding point or total relief below the overhanging electrically conductive layer structure, for example copper layer). In other words, for measuring the overhang, the undercut directly below the electrically conductive layer structure may be measured.

In the context of the present application, the term “through hole” may particularly denote a hole extending completely through an entire electrically insulating layer structure, and which may be formed in particular and preferably by laser processing. Thus, the through hole may be a laser through hole. Such a through hole may have, for example, two opposing tapering portions extending from the two opposing main surfaces of the electrically insulating layer structure. A through hole may be manufactured for instance by a combination of laser shots from the front side and the back side, i.e. from the two opposing main surfaces of, the electrically insulating layer structure. One or more laser shots may be performed from each of these sides. Formation of a through hole by laser processing from only one main surface may be possible as well. Furthermore, formation of a through hole may be carried out as well by other methods than laser processing, for instance by a plasma treatment.

According to an exemplary embodiment of the first aspect of the invention, a window in an electrically conductive layer structure is firstly opened by a first laser beam which removes only a small portion of the material of the electrically insulating layer structure under the window. This first laser treatment is followed by a second laser treatment with a second laser beam which has a smaller size than the size of the window opened by the first laser beam. It has turned out that the overhang of material of the electrically conductive layer structure relative to material of the electrically insulating layer structure beneath can be kept very small according to such an embodiment. As a result, a subsequent process of filling the manufactured laser hole with an electrically conductive material such as plated copper can be carried out highly efficiently and without the risk of forming large voids in the laser hole.

According to an exemplary embodiment of the second aspect of the invention, the configuration of the laser beam used for forming a window in an electrically conductive layer structure above an electrically conductive layer structure of component carrier material may be specifically adapted for preventing the generation of a pronounced overhang below an edge of the window. It has turned out surprisingly that by a specific configuration in particular of the energy of the laser beam, the laser energy may be predominantly used for removing material of the electrically conductive layer structure rather than spending the majority of the laser energy for burning material of the electrically insulating layer structure beneath the window.

According to an exemplary embodiment of the third aspect of the invention, a component carrier is provided which has a recess in an electrically insulating layer structure below an electrically conductive layer structure, which recess may be formed by at least two laser beams. Highly advantageously, an overhang of the electrically conductive layer structure with respect to the electrically insulating layer structure at an edge of the window is smaller than or equal to 10 μm—which can be achieved by the methods according to the first and second aspect.

According to an exemplary embodiment of the fourth aspect of the invention, a laser through hole in a thick electrically insulating layer structure may be efficiently produced with high quality and low overhang by connecting two partial recesses formed by two pairs of laser beams irradiating the component carrier pre-form from two opposing main surfaces of the thick electrically insulating layer structure. Each of the two opposing main surfaces is covered by a respective electrically conductive layer structure in which firstly a respective window may be formed by a respective first laser beam, followed by a deepening of the respective recess by a respective second laser beam. As a result of this processing, two recesses connected in an interior of the electrically insulating layer structure may be formed, each composed of two tapering portions. A respective more shallow or relatively shallower gently inclined exterior portion is followed by a respective more steep or relatively steeper interior portion on each of the two sides, wherein exterior and interior is to be understood to relate to the respective main surfaces of the electrically insulating layer structure. A correspondingly formed through hole extending through an evenly thick electrically insulating layer structure may be efficiently filled with electrically conductive material such as plated copper, to thereby establish a vertical interconnect through the electrically insulating layer structure with high electric reliability.

More generally, exemplary embodiments of the invention may use different laser beams for laser drilling with a well-controlled ratio to avoid laser reflection under the opening in the electrically conductive layer structure (in particular a copper opening). It has turned out that different independent laser shots may be efficiently generated to create the opening and the connection for better control of both aspects. As a result, a low copper overhang with a high via connection reliability may be obtained. Apart from this, a high process stability may be achieved. Highly advantageously, substantially no additional effort in terms of hardware and processing resources is required to carry out the described process.

In the following, further exemplary embodiments of the methods and the component carriers will be explained, which apply to all mentioned aspects of the invention.

In an embodiment, the second laser beam has a smaller size (in particular diameter) than a larger size (in particular diameter) of the first laser beam. It is also possible that a cross-sectional area of the first laser beam is larger than a cross-sectional area of the second laser beam. With such a design, the value of the overhang can be rendered very small. It is also possible that a cross-sectional area of the window is larger than a cross-sectional area of the second laser beam.

In an embodiment, the method comprises directing the second laser beam entirely through the window onto the electrically insulating layer structure. In particular, the second laser beam may extend over its entire width within the window. In such a configuration, no undesired reflection of the second laser beam on the exterior surface of the electrically conductive layer structure can occur.

In an embodiment, the method comprises providing a further electrically conductive layer structure at a bottom of an electrically insulating layer structure, and removing material of the electrically insulating layer structure by the first laser beam only to such an extent that the further electrically conductive layer structure is not exposed by the first laser beam. Thus, the electrically insulating layer structure may be sandwiched between the electrically conductive layer structure facing the laser beams and the further electrically conductive layer structure facing away from the laser beams. The first laser beam may be configured so that it does not extend through the entire thickness of the electrically insulating layer structure, so that the first laser beam will not expose the further electrically conductive layer structure. This has a positive impact on the overhang, which can be kept very small.

In an embodiment, the method comprises removing material of the electrically insulating layer structure by the second laser beam to such an extent that the further electrically conductive layer structure is exposed by the second laser beam. Thus, only the second laser beam will expose the further electrically conductive layer structure and will therefore extend through the entire thickness of the electrically insulating layer structure. Due to the smaller size of the second laser beam compared to the window (and preferably compared to the first laser beam), no further increase of the value of the overhang will occur as a result of the second laser beam in the described configuration.

In an embodiment, the method comprises a component embedded below at least part of the electrically insulating layer structure, wherein the further electrically conductive layer structure is a pad of the component. When exposing a pad of an embedded component (such as a semiconductor chip) only by the second laser beam and not already by the first laser beam, the sensitive component can be safely prevented from damage which might occur when coming in direct contact with the broader first laser beam.

In an embodiment, the method comprises, after the removing of the material by the second laser beam, removing other material by at least one third laser beam. For instance, the third laser beam may have a smaller size than the window. The third laser beam may be directed onto the electrically insulating layer structure from the same side as the first two laser beams. At least one further laser beam may allow precisely designing the shape of the laser hole. In order to prevent an undesired increase of the overhang, such a third or further laser beam may also have a size smaller than the window.

In an embodiment, a ratio between a size of the window and a size of the second laser beam is larger than or equal to 1.1, in particular is larger than or equal to 1.2. With this design rule, undesired increase of the over-hang by the second laser beam can be safely prevented.

In an embodiment, a difference between a size of the window and a size of the second laser beam is in a range between 3 μm and 50 μm, in particular in a range between 5 μm and 15 μm. With this design rule, undesired increase of the overhang by the second laser beam can be safely prevented as well.

In an embodiment, the method comprises generating at least one of the first laser beam and the second laser beam (preferably both) by a CO2laser. Alternatively, one or both of the laser beams may also be realized by another type of laser, for example by a UV (ultraviolet) laser. However, with exemplary embodiments of the invention it is also possible to use a CO2laser having a very high energy impact and allowing for a rapid processing of the laser holes. The reason for this is that with the described design of the two or more laser shots, in which the second and optionally all further laser shots has/have a size smaller than the window formed by the first laser shot, it becomes possible to use of a CO2laser without the above-described negative impact on the overhang. Furthermore, as will be described below in further detail, when configuring the CO2laser characteristic so that with the first laser shot heat transfer occurs substantially only in horizontal direction and thus predominantly within the electrically conductive layer structure for window formation, the high heat impact of a CO2laser is not disturbing for the characteristic of the formed laser hole. This particularly holds when the energy of the CO2laser is adjusted so that the obtained window size is sufficiently below the maximum opening size for a given aperture, as described below referring toFIG. 25.

In an embodiment, the method comprises at least partially filling at least one of a window and a recess resulting from the removal of the material of the electrically insulating layer structure with electrically conductive material, in particular by plating. For instance, it is first possible to form a seed layer (for example made of copper) by electroless deposition, followed by a galvanic deposition of additional electrically conductive material on the seed layer (in particular also copper material). As a result, a copper filled laser via can be obtained. It is possible that the seed layer has a thickness above 1 μm and/or that several cumulative seed layers are provided. For example, a thickness of a seed layer or a cumulative thickness of a plurality of seed layers may be in a range between 0.5 μm and 5 μm. When multiple seed layers are provided, they may comprise an organic (for instance polymer) layer, a palladium layer, and/or a copper layer.

In an embodiment, the method comprises directing the first laser beam directly onto the electrically conductive layer structure, in particular without protection from a base film, any other protective cover and/or without previous surface treatment of the exterior surface of the electrically conductive layer structure. Conventionally, for obtaining a smooth laser hole, the (in particular copper) surface to be treated by a laser beam needs to be prepared by a previous surface treatment. In particular, such a conventional surface treatment may involve covering the copper surface with a bond film (in particular an organic film with black oxide thereon) to suppress undesired reflection of laser energy during laser processing. Otherwise, laser reflection may be so strong that no laser hole with proper quality may be obtained. Conventionally, undesired phenomenon such as copper splash (i.e. mountains of copper formed around the window of the electrically conductive layer structure) can only be suppressed with such a surface treatment prior to laser processing. However, according to an exemplary embodiment of the invention (in particular in terms of the first aspect and the second aspect, as described above), it has turned out that the described surface treatment, in particular a coverage of the electrically conductive layer structure, may be dispensable, in particular when very thin electrically conductive layer structures are implemented. Preferably, a thickness of the copper foil forming the electrically conductive layer structure may thus be not more than 5 μm, in particular not more than 3.5 μm, more particularly not more than 3 μm.

In an embodiment, the method comprises providing another electrically conductive layer structure on a bottom of the electrically insulating layer structure, forming another window in the other electrically conductive layer structure and removing material of the electrically insulating layer structure above the further window by a third laser beam, and subsequently removing still further material of the electrically insulating layer structure above the other window by a fourth laser beam having a smaller size than the other window. Thus, in particular when a thick electrically insulating layer structure shall be provided with a laser through hole, processing of the thick electrically insulating layer structure covered on both opposing main surfaces thereof with a respective electrically conductive layer structure (such as a copper foil) by the two laser shot procedure described above at each of the two opposing main surfaces allows obtaining a smooth high quality laser hole with sufficiently small overhang. In order to achieve this, a first laser shot for opening a window in the top electrically conductive layer structure may be followed by a second laser shot having a smaller size than the formed window. Moreover, a third laser shot may be applied from the opposing main surface of the layer stack for opening another window in the bottom electrically conductive layer structure, followed by a fourth laser shot having a smaller size than the formed other window at the bottom side.

In an embodiment, the method comprises connecting a first blind hole formed by the first laser beam and the second laser beam in a top side region of the electrically insulating layer structure with a second blind hole formed by the third laser beam and by the fourth laser beam in a bottom side region of the electrically insulating layer structure. Thus, the described four laser shots may combine two blind-hole type recesses extending from the two opposing main surfaces of the layer stack to obtain a through hole extending through the entire thick electrically insulating layer structure. The through hole may be filled with conductive material to establish an electric vertical through connection.

In an embodiment, the first laser beam is configured to introduce more of its energy horizontally into the electrically conductive layer structure than vertically into the electrically insulating layer structure. Preferably, the first laser beam is configured to introduce substantially its entire energy horizontally when opening the window in the electrically conductive layer structure. By taking this measure, the majority of the energy of the first laser shot may be used for opening the window in the electrically conductive layer structure, while only a smaller amount of the laser energy will propagate into the electrically insulating layer structure for burning resin material here.

In an embodiment, the first laser beam and the second laser beam are independent from one another. Thus, the properties (such as energy, the working point, etc.) of the two laser beams may be adjusted separately and therefore in accordance with the respective tasks. In particular, the energy of the two laser beams may be adjusted separately to specifically operate the first laser beam at an instable processing point according toFIG. 25.

In an embodiment, the method comprises promoting heat transfer in horizontal direction and inhibiting heat transfer in the vertical direction by defocusing the laser beam or by operating the laser beam at an instable processing point (see reference numeral222inFIG. 25). At the instable processing point, the window size formed by the laser beam is intentionally adjusted smaller than a maximum obtainable window size by down-regulating or reducing its laser energy to such a degree that the laser energy propagates substantially horizontally rather than vertically. More particularly, the laser beam may be operated at a working point at which the laser energy-window diameter curve (seeFIG. 25) has not reached a plateau (in particular is below a 90% level). In other words, the method may comprise promoting heat transfer in horizontal direction and inhibiting heat transfer in the vertical direction by destabilizing the laser beam. By intentionally defocusing and/or destabilizing the first laser beam, i.e. operating the first laser beam at an energy level outside of the range for forming the widest possible laser hole in the electrically insulating layer structure, it has turned out surprisingly that the heat impact in vertical direction (i.e. into the electrically insulating layer structure) by the first laser shot can be efficiently suppressed, while the laser energy of the first laser beam will be injected to a high percentage into the portion of the electrically conductive layer structure in which the window is to be formed.

In an embodiment, the method comprises promoting heat transfer in the horizontal direction and inhibiting heat transfer in the vertical direction by correspondingly adjusting the energy level of the laser beam impacting the electrically conductive layer structure and the electrically insulating layer structure. In other words, a highly appropriate design parameter for increasing heat transfer horizontally and simultaneously decreasing heat transfer vertically is the adjustment of the energy of the first laser beam, as will be described below in further detail referring toFIG. 24andFIG. 25.

In a preferred embodiment, the method comprises adjusting an energy of the laser beam so that a size of the window is obtained which is smaller than or equal to 90% of a maximum opening size for a given aperture, in particular which is in a range between 60% and 90%, more particularly between 70% and 85%, of a maximum opening size for a given aperture. Descriptively speaking, the first laser beam may be intentionally operated at an instable processing point rather than at a stable processing point so that the window size in the electrically conductive layer structure is significantly smaller than a maximum window size obtained by a sufficiently high energy of the first laser beam. In contrast to operating the first laser beam at an energy at which a window size/laser energy curve has reached or has substantially reached a plateau value, the first laser beam may be driven at a significantly lower energy. As a result, the obtained window size in the electrically conductive layer structure is significantly smaller than the maximum achievable window size. Although, at first glance, this appears to be sub-optimal, it has been surprisingly found that intentionally operating the laser a relatively low energy results in an efficient material removal of the electrically conductive layer structure in horizontal direction by the laser energy, while only a minor part of the laser energy will go into the vertical direction and therefore into the electrically insulating layer structure. Surprisingly, this has a highly positive impact on the overhang which can therefore be efficiently reduced.

In an embodiment, a first portion of the recess directly beneath the electrically conductive layer structure tapers less steep than a second portion of the recess beneath the first portion. Correspondingly, a first slope of a first portion of the recess directly beneath the electrically conductive layer structure may be lower than a second slope of a second portion of the recess beneath the first portion. Thus, the first portion of the recess formed by the first laser shot may be more shallow or relatively shallower than the steeper second portion of the recess formed by the second laser shot with the beam size smaller than the window size.

In an embodiment, the recess has a kink between the first portion and the second portion. Such a kink or geometrical discontinuity between the first laser shot formed first portion and the second laser shot formed second portion of the recess may correspond to a convex section of the side wall of the electrically insulating layer structure delimiting the recess. Descriptively speaking, the mentioned kink is a fingerprint of the process in which a window in the electrically conductive layer structure is first opened by a first laser shot followed by a second laser shot having a size smaller than the window size. The kink is formed by the combination of the impact of the first laser beam and of the second laser beam on the electrically insulating layer structure. While the first laser beam substantially defines the geometry of the first portion, the second laser beam fully extending through the electrically insulating layer structure and being partially reflected at a further electrically conductive layer structure below the electrically insulating layer structure defines the geometry of the second portion and thereby forms the mentioned kink.

In an embodiment, the kink is located inside of the window. More precisely, in a viewing direction from an exterior of the recess into an interior of the recess through the window corresponding to a propagation direction of the laser beams, the kink is visible, for instance as a circumferential annular discontinuity.

In an embodiment, an angle between a vertical direction and a side wall delimiting the recess in the first portion is below 90°, in particular is in a range between 20° and 70°. Correspondingly, an angle between a vertical direction and a side wall delimiting the recess in the second portion may be in a range between 0° and 30°, in particular between 5° and 20°. The exact value of these angles is defined by process parameters such as the width of the two laser beams, the energy of laser beams, etc.

In an embodiment, the angle between the vertical direction and a side wall delimiting the recess in the first portion is larger than the angle between the vertical direction and a side wall delimiting the recess in the second portion. A corresponding recess geometry has turned out to be advantageous for a subsequent plating procedure during which the recess may be substantially entirely filled with electrically conductive material such as copper. Thus, the described procedure not only allows manufacturing a smooth laser hole, but also promotes a void-poor or even void-free filling of the laser hole with copper or another appropriate electrically conductive material.

In an embodiment, a side wall delimiting the recess in the second portion tapers downwardly towards a vertical axis. Descriptively speaking, each of the first portion of the second portion may have substantially a frustoconical shape with different opening angles.

In an embodiment, the window has a size of not more than 70 μm, in particular not more than 50 μm. Thus, the described manufacturing process is particularly appropriate for manufacturing small vias. In case of a 50 μm wide copper opening on a 40 μm thick dielectric, a large overhang may induce inclusion during via filling as the copper opening gets closed first before filling the entire via due to the large volume created by the overhang. When being able to process with low overhang level as a result of the above-described open window processing method according to an exemplary embodiment of the invention, applications with small vias become possible. In addition, using two independent laser beams allows a better control of the connection diameter, for instance at 40 μm which is highly beneficial for registration.

In an embodiment, a thickness of the electrically insulating layer structure is at least 100 μm, in particular at least 150 μm, more particularly at least 200 μm. Such an embodiment may be particularly advantageous in terms of the fourth aspect of the invention. Forming a laser hole in a thick electrically insulating layer structure has been conventionally problematic. However, with the architecture according to an exemplary embodiment of the invention involving a window opened by a first laser beam in combination with a second laser beam being narrower than the window and propagating only through a central portion of the window, and when applying this procedure to each of two opposing main surfaces of an electrically insulating layer structure each being covered with a respective electrically conductive layer structure, a smooth laser hole with small overhang on both sides may be obtained which can be properly filled with electrically conductive material such as copper, for example by plating. Thus, forming laser through holes with high quality even in a thick dielectric body becomes possible.

In an embodiment, the component carrier comprises another electrically conductive layer structure on a bottom of the electrically insulating layer structure, a further window in the other electrically conductive layer structure, and another recess in the electrically insulating layer structure above the further window, wherein the electrically conductive material fills at least part of the other recess as well. Both electrically conductive layer structures may be metallic layers such as copper foils. The electrically insulating layer structure may comprise resin (for instance epoxy resin) and may optionally include reinforcing particles (such as glass spheres or glass fibers). More specifically, the electrically insulating layer structure may be made of prepreg material.

In an embodiment, different portions of the recess beneath the electrically conductive layer structure taper with different steepness, wherein different portions of the other recess above the other electrically conductive layer structure taper with different steepness as well. Such a geometry may be obtained by the described combination of the first laser shot opening a window in an electrically conductive layer structure followed by a second laser shot with smaller size and propagating completely through the window.

In an embodiment, an overhang of the other electrically conductive layer structure with respect to the electrically insulating layer structure at an edge of the other window is smaller than or equal to 10 μm. As can be taken for instance fromFIG. 10, the value of the overhang may be reliably below 10 μm when forming a laser hole as described above. A maximum of a distribution of the overhang value for multiple holes may even be in the range of about 5 μm.

In an embodiment, the thickness of the electrically conductive layer structure is less than 5 μm, in particular less than 3.5 μm, more particularly less than or equal to 3 μm. Thus, extremely thin copper foils may be used according to exemplary embodiments as electrically conductive layer structures, in particular on the top side. More specifically, thin copper foils (in particular with a thickness of not more than 5 μm) may be used and may be directly (i.e. without surface treatment or surface coverage by a reflection suppressing material such as black oxide) used as a basis for the described two-shot laser process. Drilling such thin copper foils requires a well-controlled laser process to avoid high copper overhang which cannot be etched away to avoid exposing the laminate. Processing with low copper overhang on thin foils is highly challenging especially when there is no surface treatment. Indeed, the required high energy to open the copper will get easily transferred to the resin below the thin foil and generate then the undercut. However, when reducing the energy, a high copper splash will be found around the via that cannot be etched away. However, by using the above-described concept of a first laser shot opening a window in an electrically conductive layer structure and a subsequent second narrower laser shot allows avoiding the above defects.

When a laser through hole is formed according to an exemplary embodiment in a thick electrically insulating layer structure of for instance more than 100 μm, two connected recesses may constitute the through hole and may be laser threaded in two opposing main surfaces of the sandwich structure of the electrically insulating layer structure covered by two electrically conductive layer structures. In such an embodiment, a first portion of the upper recess directly underneath the electrically conductive layer structure may taper less steeply than a second portion of the upper recess underneath the first portion. In particular, a first kink or convex discontinuity may be formed (for example as an annular structure) between the first portion and the second portion. Correspondingly, a third portion of the other or lower recess directly above the other electrically conductive layer structure may taper less steeply than a fourth portion of the other or lower recess above the third portion. In particular, a second kink or convex discontinuity may be formed (for example as a further annular structure) between the third portion and the fourth portion. Such a geometry is shown, for example, inFIG. 15.

As mentioned above, at least one component may be embedded in the component carrier, in particular directly below the further electrically conductive layer structure which may for example be a pad of the component. More generally, at least one component which may be embedded in and/or surface mounted on the component carrier can be selected from a group consisting of an electrically non-conductive inlay, an electrically conductive inlay (such as a metal inlay, preferably comprising copper or aluminum), a heat transfer unit (for example a heat pipe), a light guiding element (for example an optical waveguide or a light conductor connection), an electronic component, or combinations thereof. For example, the component can be an active electronic component, a passive electronic component, an electronic chip, a storage device (for instance a DRAM or another data memory), a filter, an integrated circuit, a signal processing component, a power management component, an optoelectronic interface element, a 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, a light guide, and an energy harvesting unit. However, other components may be embedded in the component carrier. For example, a magnetic element can be used as a component. Such a magnetic element may be a permanent magnetic element (such as a ferromagnetic element, an antiferromagnetic element, a multiferroic element or a ferrimagnetic element, for instance a ferrite base structure) 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. One or more components may be surface mounted on the component carrier and/or may be embedded in an interior thereof. Moreover, also other than the mentioned components may be used as component.

In an embodiment, the component carrier comprises a stack of at least one electrically insulating layer structure and at least one electrically conductive layer structure. For example, the component carrier may be a laminate of the mentioned electrically insulating layer structure(s) and electrically conductive layer structure(s), in particular formed by applying mechanical pressure 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 component carrier is shaped as a plate. This contributes to the compact design, wherein the component carrier nevertheless provides a large basis for mounting components thereon. Furthermore, in particular a naked die as example for an embedded electronic component, can be conveniently embedded, thanks to its small thickness, into a thin plate such as a printed circuit board.

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

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

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

The substrate or interposer may consist of at least a layer of glass, silicon (Si) or a photo-imageable or dry-etchable organic material like epoxy-based Build-Up films or polymer compounds like Polyimide, Polybenzoxazole, or Benzocyclobutene.

In an embodiment, dielectric material of the at least one electrically insulating layer structure 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, 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. Teflon® is a registered mark of The Chemours Company FC LLC of Wilmington, Del., U.S.A. 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 for substrates 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, electrically conductive material of the electrically conductive layer structure and/or at least one further electrically conductive layer structure comprises at least one of the group consisting of copper, aluminum, nickel, silver, gold, palladium, and tungsten. Although copper is usually preferred, other materials or coated versions thereof are possible as well, in particular coated with supra-conductive material such as graphene.

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

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

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

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

According to an exemplary embodiment of the invention, a window may be opened by a laser shot in an electrically conductive layer structure above an electrically insulating layer structure to obtain a very low value of the undesired phenomenon of overhang, in particular for correspondingly opening the window for obtaining an overhang of 10 μm or less.

In existing component carriers using an ultra-thin copper foil as electrically conductive layer structure and prepreg as electrically insulating layer structure, the copper overhang can exceed 14 μm under normal laser process, which is a big challenge for inclusion after via filling. Thus, it would be highly desirable to decrease copper overhang.

According to an exemplary embodiment of the invention, the copper overhang performance may be significantly improved and may be reduced up to or even below 10 μm. The overhang is a result of two phenomena under a traditional laser method with the same laser beam size used for two subsequent laser shots. A first phenomenon is the overheat by the first shot happening when the laser beam gets in contact with the panel surface to open the copper foil. In addition to the drilled surface, the laser beam energy profile creates an affected zone where the heat goes through the ultra-thin copper and removes resin below creating then the overhang. The other part of the overhang comes from the additional shot's reflection. Indeed, under same beam size of the first shot, the diameter of the laser beam is bigger than the opening and the part of the laser beam reflection will go to the via wall inducing then a larger overhang.

In order to overcome such shortcomings, an exemplary embodiment of the invention creates a first laser shot using a bigger beam size, which will create a large window in the electrically conductive layer structure for a subsequent smaller second laser beam. The latter may have a size smaller than the size of the window and can clean the bottom via and get reflected completely out of the via without significantly burning the via wall. Then, the copper overhang only results from the first laser shot, thus can be controlled below 10 μm.

Descriptively speaking, while two laser shots are dependent from one another and have a similar laser beam size in a conventional laser drilling procedure, exemplary embodiments of the invention implement two independent laser shots with different beam size. An embodiment of such a method may use a bigger mask for the first laser shot to obtain a desired opening diameter of the window, and then using a smaller mask for the second laser shot to clean the hole. Highly advantageously, an exemplary embodiment implements a large window formation process using a laser beam for opening the window in the electrically conductive layer structure (such as a metallic layer, more specifically a copper foil), followed by a narrower subsequent other laser beam propagating only through a sub-portion of the window. As a result of this process, a unique via shape can be obtained.

Using two (or more) independent laser shots for opening a window in an electrically conductive layer structure and for forming a laser hole in an underneath electrically insulating layer structure provides more flexibility for the via design. In particular, it may be possible to reach 50 μm vias with the described method while a general laser capability for laser drilling is presently at 65 μm. Thus, exemplary embodiments of the invention enable the formation of highly reliable vias and reduce the risk for undesired phenomena such as inclusion, cracks and wedge.

An exemplary embodiment of the invention makes also a better control of the connection diameter possible. Indeed, as the second laser shot is independent from the first laser shot, it can be designed for different connection diameter possibilities. Moreover, a better registration accuracy may be achieved than with conventional procedures: As the connection diameter can be well controlled, the registration to the inner layers gets improved. Also, as the overhang is smaller, the pad breakout risk is smaller.

Exemplary embodiments of the invention may be implemented with all kinds of component carrier technologies, including printed circuit board (PCB) applications, IC substrate applications, component carrier applications with one or more embedded components, etc. In particular, such component carriers may be formed with ultra-thin copper foils, thin or thick dielectric layers, RCC (resin coated copper) materials, small via size, etc.

According to an exemplary embodiment of the invention, only one dielectric layer is processed by the two laser shots. In other words, the electrically insulating layer structure may be a continuous structure and may be made subject of a laser processing with the two or more laser shots, as described above. In such a procedure, it is possible to open the copper layer (or more generally an electrically conductive layer) by the first laser beam itself, and the first laser beam may also partially go through the insulating layer.

When carrying out a method according to an exemplary embodiment of the invention, a via shape may be obtained which may be characterized by a specific ratio between the copper opening and the connection diameter. Moreover, a possible shift between the opening and connection centers may be formed. Beyond this, such as manufacturing method may result in a very low copper overhang of 10 μm or less.

With the pure laser processing architecture for window opening and via formation according to an exemplary embodiment of the invention, it may be advantageously possible to make the formation of photo lines dispensable. Another advantage is that the described two shot laser processing method with smaller second shot allows for direct drilling without previous surface treatment (such as formation of a bond film with black oxide for suppressing undesired reflection of laser energy). Apart from the described two laser shots, it is possible to carry out at least one further laser shot to design a desired shape of the laser hole.

FIG. 1toFIG. 4illustrate cross-sectional views of structures obtained during carrying out a method of manufacturing a component carrier130with a laser via, shown inFIG. 4, by a double laser shot according to an exemplary embodiment of the invention.

Referring toFIG. 1, a layer stack is shown which is composed of an electrically conductive layer structure100on top of an electrically insulating layer structure102being arranged, in turn, on a further electrically conductive layer structure110at a bottom of the electrically insulating layer structure102. The electrically conductive layer structures100,110may be copper foils. A thickness, d, of the electrically conductive layer structure100may be for example as small as 3.5 μm. The electrically insulating layer structure102may for example comprise resin (in particular epoxy resin), optionally filled with reinforcing particles (such as glass fiber or glass spheres). For instance, the electrically insulating layer structure102may be a prepreg layer.

Referring toFIG. 2, a through-hole type window104is laser drilled in the electrically conductive layer structure100by a first laser beam106. The first laser beam106may be generated by a high-power and high wavelength CO2laser source allowing fast laser drilling and having properties which may be adjusted by a control unit180(such as a processor). During this first laser shot by the first laser beam106, a significant portion of the laser energy is spent for removing metallic material of the electrically conductive layer structure100for forming the window104. Simultaneously, only a small part of the material of the electrically insulating layer structure102below the window104is removed by the first laser beam106. However, the first laser beam106removes material of the electrically insulating layer structure102only to such an extent that the further electrically conductive layer structure110is not exposed by the first laser beam106. In other words, the first laser beam106, in particular its energy impact on the layer stack, is adjusted under control of the control unit180so that it does not extend vertically through the entire electrically insulating layer structure102.

As a result of this processing of the shown layer stack by the first laser beam106, an overhang170in form of a void or narrow gap between electrically conductive layer structure100and electrically insulating layer structure102at the edge199of the window104is generated. The overhang170has a substantially triangular shape in the cross-sectional view ofFIG. 2. The overhang170of the electrically conductive layer structure100with respect to the electrically insulating layer structure102at the circumferential edge199of the window104is smaller than or equal to 10 μm. In particular by correspondingly adjusting the energy of the first laser beam106to be sufficiently low (compareFIG. 25described below), this overhang170may be kept very small, for instance will not exceed 10 μm.

Advantageously, the first laser beam106may be directed directly onto the electrically conductive layer structure100without protection by a base film or the like and/or without previous surface treatment of the upper main surface of the electrically conductive layer structure100. When keeping the energy of the first laser beam106sufficiently small as described below, the energy impact of the laser energy will be substantially horizontal according toFIG. 2and will mainly contribute to the formation of the window104in the electrically conductive layer structure100rather than extending substantially downward and cutting through the entire vertical extension of the electrically insulating layer structure102. In other words, the first laser beam106may be configured and may be adjusted by the control unit180to introduce much more of its energy horizontally into the electrically conductive layer structure100than vertically into the electrically insulating layer structure102. Thus, the first laser beam106is configured to introduce its energy substantially horizontally when opening the window104in the electrically conductive layer structure100. During formation of the window104, the laser energy diffuses substantially only horizontally, not vertically with the configuration according toFIG. 2. With the described laser processing, formation of window104with low overhang170may be achieved even without surface treatment or surface coverage of the electrically conductive layer structure102to suppress reflection of laser energy at an upper surface thereof. As shown inFIG. 2, the diameter or size of the first laser beam106reaching the surface of the electrically conductive layer structure100is denoted as B, whereas the diameter or size of the window104is denoted as L.

Referring toFIG. 3, after having completed laser treatment of the shown layer stack by the first laser beam106, the obtained structure according toFIG. 2may be made subject to further laser processing by an independent second laser beam108which can be adjusted by the control unit180as well. Preferably, also the second laser beam108is generated by a CO2laser source. The second laser beam108may remove further material of the electrically insulating layer structure102below the window104. As shown inFIG. 3, the second laser beam108has a smaller diameter or size D than the size L of the window104formed by the first laser beam106. For instance, the window104has a size L of 50 μm. The second laser beam108has a smaller size D than the larger size B of the first laser beam106. Preferably, a difference between the size L of the window104and the size D of the second laser beam108is in a range between 5 μm and 15 μm. Moreover, as can be taken fromFIG. 3as well, the second laser beam108propagates over its entire width or size D through and within the window104and will therefore not interact with the exterior main surface of the electrically conductive layer structure100. In other words, the second laser beam108is directed entirely through the window104onto the electrically insulating layer structure102. The second laser beam108is furthermore controlled by the control unit180to remove material of the electrically insulating layer structure102to such an extent that the further electrically conductive layer structure110is exposed by the second laser beam108. In other words, the second laser beam108extends through the entire vertical thickness of the electrically insulating layer structure102. The upper main surface of the further electrically conductive layer structure110serves as a stop layer for the second laser beam108, i.e. is not removed by the second laser beam108. Thus, in contrast to the first laser beam106, the second laser beam108propagates up to the bottom of the resin layer and therefore exposes the further electrically conductive layer structure110to render it accessible for an electric contact to be formed. Therefore, the narrower second laser beam108cleans the laser hole and enables an electric connection of the embedded copper of the further electrically conductive layer structure110.

As can be taken fromFIG. 3, the second laser beam108may be reflected partially at the exposed upper main surface of the further electrically conductive layer structure110, see reflected beam portion195. However, due to the described geometric conditions (in particular the fact that the second laser beam108has a size smaller than the window104), the second laser beam108will not further increase the size of the overhang170. In other words, the size of the overhang170is substantially defined by the first laser beam106only (however also only to a moderate extent), but will advantageously not be further increased by the second laser beam108. The overhang170of the electrically conductive layer structure100with respect to the electrically insulating layer structure102at the edge199of the window104is thus still smaller than or equal to 10 μm after completing formation of the laser hole by the second laser beam108.

Next, the geometry of the laser hole or recess132formed by the two-laser shot procedures described above will be described in further detail. A first portion142of the recess132directly beneath the electrically conductive layer structure100has been formed predominantly by the first laser beam106and tapers less steeply than a second portion144of the recess132beneath the first portion142. The second portion144has been formed predominantly by the second laser beam108. Hence, a first slope of the first portion142is lower than a second slope of the second portion144. As a result, a (circumferential or annular) kink146is formed as a geometrical discontinuity at an interface between the first portion142and the second portion144. The kink146forms an edge and defines a convex portion of the remaining electrically insulating layer structure102. Since the size D of the second laser beam108has been smaller than the size L of the window104, the kink146is located laterally inside of the window104and is visible from above as a circle.

An angle α between a vertical direction197and a side wall delimiting the recess132in the first portion142(for instance a first frustoconical portion) is for instance in a range between 20° and 70°, depending on the exact control of the two-shot laser process by control unit180. An angle β between a vertical direction197and a side wall delimiting the recess132in the second portion144(for instance a second frustoconical portion which may or may not be coaxial with the first frustoconical portion) may be in the range between 5° and 20°, depending on the exact control of the two-shot laser process by control unit180. The angle α is thus larger than the angle β. However, the entire side wall delimiting the recess132in the first portion142and in the second portion144tapers downwardly towards a vertical axis.

Referring toFIG. 4, the recess132or laser hole created by the removed material of the electrically insulating layer structure102and by the removed material of the electrically conductive layer structure100is filled partly or completely with electrically conductive material138such as copper. For this purpose, a seed layer of the electrically conductive material138(such as copper) may first be formed on the surface of the structure shown inFIG. 3, for example by electroless deposition. Thereafter, further electrically conductive material138may be plated onto the seed layer, for instance by galvanic deposition. As a result, the plate shaped PCB (printed circuit board) type component carrier130according to an exemplary embodiment of the invention as shown inFIG. 4can be obtained. The electrically conductive material138provides an electric contact for the buried further electrically conductive layer structure110which can thereby be electrically connected to an exterior surface of the component carrier130.

FIG. 5andFIG. 6illustrate cross-sectional views of structures obtained during carrying out a conventional method of manufacturing a component carrier by a combination of a photo process and a laser process.

Referring toFIG. 5, a prepreg layer102′ is covered on its bottom by a lower copper layer110′ and is covered on its top by an upper copper layer100′. The upper copper layer100′ has been patterned by a photolithographic process to thereby form a window104′ in the upper copper layer100′.

Referring toFIG. 6, a laser beam106′ is generated which extends through the window104′ and removes material of the prepreg layer102′ until the laser beam106′ reaches the lower copper layer110′. Thereby, a recess132′ is formed in the prepreg layer102′. However, forming the window104′ by a photo process in accordance with the described conventional process is time-consuming, difficult, cumbersome and limits the degree of miniaturization.

FIG. 7andFIG. 8illustrate cross-sectional views of structures obtained during carrying out a conventional method of manufacturing a component carrier by a combination of two laser processes.

Referring toFIG. 7, the upper copper layer100′ is covered by a protection layer101′ suppressing undesired reflection of laser light. The window104′ in the upper copper layer100′ is formed by a first laser beam106′. Simultaneously, material of the prepreg layer102′ is removed by the first laser beam106′ to thereby form a blind hole type recess132′. During this process, an overhang170′ is formed between the prepreg layer102′ and the upper copper layer100′.

Referring toFIG. 8, a second laser beam108′ is generated with a size larger than the window104′. The second laser beam108′ removes further material of the prepreg layer102′ and exposes a part of an upper main surface of the lower copper layer110′. A significant amount of the second laser beam108′ is reflected at the exposed surface of the lower copper layer110′ due to the significant width of the second laser beam108′. The reflected second laser beam108′, indicated with reference numeral108″ propagates towards the overhang170′ generated by the first laser beam106′ and significantly increases the overhang size, see reference numeral170″.

Thus, with the conventional procedure described referring toFIG. 7andFIG. 8, both laser beams106′,108′ significantly contribute to the dimension of the overhang170″. Thus, the quality of the recess132′ is poor due to the large overhang170″.

FIG. 9illustrates a cross-sectional view of a copper filled laser via manufactured according to an exemplary embodiment of the invention.FIG. 9shows that the obtained overhang is acceptably small.FIG. 9shows a trapezoid shape with through hole (and no base copper on bottom).

FIG. 10illustrates a histogram198showing a distribution of the size of the overhang170of laser holes manufactured according to an exemplary embodiment of the invention. Along an abscissa184, a value of the size of the overhang170is plotted in micrometer. Along an ordinate186, a number of laser holes having the respective value of the size of the overhang170is plotted. A fitting curve188shows that an average value of the overhang170is around 5 μm. No significant amount of laser holes as an overhang170above 10 μm.

FIG. 11illustrates a cross-sectional view of a laser via manufactured according to an exemplary embodiment of the invention. The quality of the shown laser via is fully acceptable.

FIG. 12toFIG. 15illustrate cross-sectional views of structures obtained during carrying out a method of manufacturing a component carrier130, shown inFIG. 15, by four laser beam shot two-sided processing according to an exemplary embodiment of the invention.

Referring toFIG. 12, an electrically insulating layer structure102with a pronounced thickness S is shown. For instance, the thickness S is 200 μm or more. Conventionally, it is a challenge to manufacture a smooth and high-quality copper plated laser through hole extending through such a thick electrically insulating layer structure102, which may be for instance made of resin or FR4. As can be taken fromFIG. 12, a first laser beam106is directed on the electrically conductive layer structure100on a top surface of the electrically insulating layer structure102to form window104in the electrically conductive layer structure100and to form a shallow first blind hole122in the electrically insulating layer structure102. An undesired overhang170may be sufficiently small by an appropriate energy control of the first laser beam106, as described above.

Referring toFIG. 13, the first blind hole122is extended in a downward direction deeper into the electrically insulating layer structure102by directing a second laser beam108having a size smaller than the width of the window104directly onto an exposed surface of the electrically insulating layer structure102. Due to the described geometry, recess132is increased from a first depth corresponding to first portion142up to a second depth corresponding to the second portion144. The portions142,144are geometrically separated by kink146.

Referring toFIG. 14, another window120is formed in another electrically conductive layer structure110covering the bottom main surface of the electrically insulating layer structure102by a third laser beam116. The third laser beam116removes material of the electrically insulating layer structure102above the further window120. Thereby, a shallow second blind hole124is formed in a lower portion of the electrically insulating layer structure102. An undesired overhang170between the electrically insulating layer structure102and the further electrically conductive layer structure110nearby the further window120may be sufficiently small by an appropriate energy control of the third laser beam116, which may be adjusted correspondingly to the energy control of the first laser beam106.

Referring toFIG. 15, the second blind hole124is extended in an upward direction deeper into the electrically insulating layer structure102by directing a fourth laser beam118having a size smaller than the width of the further window120directly onto an exposed surface of the electrically insulating layer structure102from below. Due to the described geometry, the portion of the recess132in the lower region ofFIG. 14andFIG. 15is further increased from a third depth corresponding to third portion160up to a fourth depth corresponding to a fourth portion162. The portions160,162are geometrically separated by a further kink164.

By this procedure, the first blind hole122formed by the first laser beam106and the second laser beam108in a top side region of the electrically insulating layer structure102is connected with the second blind hole124formed by the third laser beam116and by the fourth laser beam118in a bottom side of the electrically insulating layer structure102, to thereby finally form a common laser through hole through the entire thick electrically insulating layer structure102.

Subsequently, electrically conductive material138may be filled in the upper part of the recess132and in the lower part of the recess132. The electrically conductive material138forms a connected structure and extends through the entire through hole156.

As shown, different portions of the recess132beneath the electrically conductive layer structure100taper with different steepness. Correspondingly, different portions of the other recess132above the other electrically conductive layer structure100also taper with different steepness. Due to the described process, the overhang170at the window104and at the other window120is smaller than or equal to 10 μm.

FIG. 16andFIG. 17illustrate cross-sectional views of structures obtained during carrying out a method of manufacturing a component carrier according to an exemplary embodiment of the invention.

Referring toFIG. 16, a procedure similar to that described above referring toFIG. 12is illustrated again. Referring toFIG. 17, a procedure similar to that described above referring toFIG. 13is illustrated again.

With the procedure described referring toFIG. 12toFIG. 17, laser through holes on thick cores188(seeFIG. 16andFIG. 17) can be formed with small overhang170.

For an electrically insulating layer structure102(such as a core, in particular made of fully cured dielectric material) with a thickness of 200 μm or higher, forming a laser through hole would require a high-power machine to achieve stable opening and middle diameters. Indeed, processing with low power will not allow a consistent middle diameter even with high number of shots as most of the laser energy will be diffused through the through holes instead of removing the resin on the wall.

Producing with high power has also its limitation as it tends to create larger and instable overhang and therefore the resin opening capability gets lower as the standard deviation gets higher.

In order to produce laser through holes with high quality with a stable process on standard low power machines, an exemplary embodiment of the invention uses the open window concept described above to separate the processing of the opening and the middle diameter. Indeed, the first laser shots on both sides (front and back) of the electrically insulating layer structure102(compare reference numerals106,116inFIG. 12andFIG. 14) may be used to open the respective window104,120and focuses on the window opening where the overhang170is low and stable. Then the following laser shots (compare reference numerals108,118inFIG. 13andFIG. 15) may focus only on the middle diameter by using high power shots. Indeed, by being able to process with smaller laser beam size during the subsequent laser shots (compare reference numerals108,118inFIG. 13andFIG. 15), it is possible to amplify the energy density which renders it possible to process with high peak power. The latter highly advantageous measure would not be possible if the copper material of the respective electrically conductive layer structure100,110was not opened in advance. If used on copper with pre-opened laser windows104,120, this kind of beam characteristics may open even very small vias (for instance having a size of 40 μm) with low copper overhang170.

FIG. 18andFIG. 19illustrate cross-sectional views of laser vias manufactured according to an exemplary embodiment of the invention corresponding toFIG. 12toFIG. 17.

FIG. 20andFIG. 21illustrate cross-sectional views of structures obtained during carrying out a method of manufacturing a component carrier130with embedded component112according to an exemplary embodiment of the invention.

Referring toFIG. 20, an embedded component112(such as a semiconductor chip) with a pad114is shown being embedded below an electrically insulating layer structure102, as described above. When exposing the pad114by laser drilling for forming an exterior electrically conductive contact for contacting the component112with an exterior of the component carrier130to be manufactured, the pad114corresponds to the further electrically conductive layer structure110of the previously described embodiments.FIG. 20illustrates how a window104is opened in the electrically conductive layer structure100and the shallow recess132is formed in the electrically insulating layer structure102by the first laser beam106(as described in detail inFIG. 2). The recess132however does not yet extend up to the pad114which therefore remains embedded after the first laser shot.

Referring toFIG. 21, two further procedures are shown which are carried out one after the other. Firstly, after having obtained the structure shown inFIG. 20, the second laser beam108with smaller size compared to the size of the window104is directed directly towards the dielectric material of the electrically insulating layer structure102until an upper main surface of the pad114of the component112is exposed by the second laser shot. Thereafter, the so obtained recess132is filled with electrically conductive material138, for instance by copper plating.

The procedure described referring toFIG. 20andFIG. 21shows that an even sensitive component112can be gently exposed for electric contact purposes by configuring the first laser beam106only for window opening and a slight material removal in an upper region of the electrically insulating layer structure102. The actual contact with the pad114is then established by the cleaning narrower second laser beam108.

Hence,FIG. 20andFIG. 21show a process of electrically connecting the component112using a CO2laser to drill the thin dielectric material in form of the electrically insulating layer structure102.

Using a CO2laser for direct laser drilling is generally avoided to connect components112. Indeed, when opening the copper material of the electrically conductive layer structure100, the high generated heat can easily reach the component112and damage the thin copper pad114(which may typically have a thickness in the range between 3 μm and 6 μm) of the one or more components112. Therefore, conformal mask, large window and other laser sources are conventionally used in component carrier related applications with embedded components112.

However, when applying the open window processing architecture according toFIG. 20andFIG. 21according to an exemplary embodiment of the invention, it has turned out to be easy to create the copper connections as the first unstable (compareFIG. 25) shot with the first laser beam106used for opening the window104in the electrically conductive layer structure100will not reach the one or more sensitive components112beneath (compareFIG. 20). Only the narrower second laser beam108will then accomplish the actual electric contacting task by exposing the pads114.

FIG. 22andFIG. 23illustrate cross-sectional views of laser vias manufactured according to exemplary embodiments of the invention.

Referring toFIG. 22, the result of a direct laser drilling process without previous surface treatment of an upper main surface of the electrically conductive layer structure100is shown. Neither surface treatment nor the attachment of a protective bond film, black oxide, etc. for suppressing reflection of laser radiation is necessary with the described procedure.

Referring toFIG. 23, a laser via with a window size of approximately 50 μm, an overhang170of not more than 10 μm and a dielectric dimension of about 40 μm is shown. Thus, the two-laser shot procedure as described above is particularly suitable for small vias size.

Next, some considerations will be described as a basis for the subsequent description of an embodiment according to the second aspect of the invention to which alsoFIG. 24in combination withFIG. 25refers.

Processing with a laser provides high throughput as it allows processing with wider beams and higher energy level to remove the maximum possible material (of a conductive layer or an insulator). However, a CO2laser is characterized by an excessive heat generation that gets worst knowing that the conductive layer reflects in many cases more than 80% of the provided CO2laser energy requiring then processing at high energy level to allow that the copper melts and is removed.

The high energy level and the excessive heat generation removes and burns a high amount of the dielectric material impacting then the via quality in terms of copper overhang and poor roughness on the via wall, while it also prevents controlling the processing depth. Indeed, for thin dielectric material (for instance with a thickness in the range from 15 μm to 35 μm), the first shot with a CO2laser beam needed for a stable, predictable, reliable and reproducible opening of a window in a copper layer, may already reach the bottom of the electrically insulating layer structure and therefore creates even more overhang due to laser reflection phenomena, damages to components beneath in case of embedding, and/or induces bottle holes in case of laser through holes.

As opening the copper with high energy is one of the main root causes for the above and other defects, it may be considered to process with low energy. However, producing with lower energy level may also induce smaller connection diameters, a need for more shots as the following shots will have the same energy level.

To overcome such and other limitation, an exemplary embodiment of the invention opens the copper, or more generally the electrically conductive layer structure, differently. For example, when using a large window process that involves the procedure of removing copper using an etching process and then the remaining dielectric by laser treatment, the defects above do not exist. Nevertheless, a large window process is a time-consuming and expensive solution as it requires an additional photo process.

According to an exemplary embodiment of the invention, an open window laser drilling procedure may be implemented which may comprise opening the copper window in the electrically conductive layer structure by a special laser processing treatment (corresponding toFIG. 2) and then remove the remaining dielectric of the electrically insulating layer structure by one or more additional independent laser beams having a smaller size than the window (corresponding toFIG. 3). In this way, it has turned out to be possible to overcome the registration issue that might induce partially opened vias. Furthermore, this may also allow to avoid or at least strongly suppress a reflection of the laser beam on the via wall creating larger overhangs.

FIG. 24illustrates a diagram200showing a dependency between the energy (plotted along an abscissa202) of a laser beam106and an opening diameter (plotted along an ordinate204) or size of a window104in an operation mode with a stable processing point210. The mentioned dependency is indicated by a curve208.

The curve208of the diagram200shows that, when the energy increases, the size or opening diameter of the window104increases as well. In a low energy region, the curve208increases with a significant slope. From a certain energy onwards, the described dependency is no longer valid: In contrast to this, the curve208approaches at higher energy levels a plateau or asymptote indicated as target opening206inFIG. 24. In this region, a further increase of the laser energy does not result in a significant further increase of the opening diameter. Descriptively speaking, the additional energy in this regime will then result in a significant burning of resin material of the electrically insulating layer structure102.

During copper opening (more generally during opening a window104in an electrically conductive layer structure100,110by a laser beam106), the laser energy is high and when processing in the stable zone around stable processing point210(maximum copper opening for a given aperture or mask), the heat tends to dissipate in the via depths to remove more resin and reach the bottom or on the via wall to remove and burn more resin and then create more overhang170as the copper opening does not get larger.

It can therefore be concluded fromFIG. 24that the mere increase of the laser energy does not allow obtaining the desired result of a reduced overhang170.

FIG. 25illustrates a further diagram220showing a dependency between the energy (again plotted along abscissa202) of laser beam106and the opening diameter (plotted again along ordinate204) or size of window104in an operation mode according to an exemplary embodiment of the invention with an instable processing point222. Descriptively speaking, an exemplary embodiment of the invention does not intend to adjust the energy of the laser beam106so as to operate the laser at the stable processing point210as close as possible at the maximum opening for the given aperture or mask. In contrast to this, an exemplary embodiment of the invention operates the laser and correspondingly adjust the laser energy so as to operate the first laser beam106at the instable processing point222.

By opening window104by the first laser beam106adjusted at the instable processing point222, it is highly advantageously possible to promote a horizontal heat dissipation by giving more room to open the window104in the copper material of the electrically conductive layer structure100,110rather than drilling a deeper via.

In the instable processing point222above, the provided laser beam energy may be mostly used and focused on opening the window104in the electrically conductive layer structure100,110and creating larger via while only a portion of the dielectric material of the electrically insulating layer structure102will be removed. In this case, the overhang170may be advantageously lower. In the presence of one or more embedded components112, the latter will not be harmed and there will be no risk for bottle holes in case of laser through holes.

In view of the foregoing, a preferred embodiment of the invention forms the window104in the electrically conductive layer structure100and removes material of the electrically insulating layer structure102below the window104by the laser beam106being configured for promoting heat transfer in the electrically conductive layer structure100in horizontal direction and inhibiting heat transfer in vertical direction (which would only remove more material of the electrically insulating layer structure102). More specifically, the method may comprise promoting heat transfer in horizontal direction and inhibiting heat transfer in the vertical direction by correspondingly adjusting the energy impact of the laser beam106on the electrically conductive layer structure100and the electrically insulating layer structure102in accordance with instable processing point222.

In a particularly preferred embodiment and again referring toFIG. 25, the method comprises adjusting the energy of the laser beam106so that the size L of the window104(compare target window diameter224) is obtained which is smaller than or equal to 90% of a maximum opening size A for a given aperture. The size L of the window104corresponds to the instable processing point222, whereas the maximum open size A substantially corresponds to a stable processing point210shown inFIG. 24. In particular, the mentioned ratio may be in a range between 60% and 90%, and most preferred between 70% and 85% of a maximum opening size A for a given aperture. In such a scenario, a particularly small overhang170may be obtained.

FIG. 26toFIG. 28illustrate cross-sectional views of structures obtained during carrying out a method of manufacturing a component carrier130with a laser via, using as an alternative to the embodiment ofFIG. 12toFIG. 15, a three-laser shot two-sided processing according to an exemplary embodiment of the invention. This procedure is in particular appropriate for a thin electrically insulating layer structure102(in particular core), as indicated with thickness “s” inFIG. 26being smaller than thickness “S” ofFIG. 12. For instance, thickness s may be smaller than 100 μm, for instance in a range between 30 μm and 70 μm.

Referring toFIG. 26, first laser beam106is directed on the electrically conductive layer structure100on a top surface of the electrically insulating layer structure102to form window104in the electrically conductive layer structure100and to form a shallow first blind hole122in the electrically insulating layer structure102. An undesired overhang170may be sufficiently small by an appropriate energy control of the first laser beam106, as described above.

Referring toFIG. 27, the first blind hole122is extended in a downward direction deeper into the electrically insulating layer structure102by directing a second laser beam108having a size smaller than the width of the window104directly onto an exposed surface of the electrically insulating layer structure102. Due to the described geometry, the depth of recess132is increased.

Referring toFIG. 28, another window120is formed in the other electrically conductive layer structure110covering the bottom main surface of the electrically insulating layer structure102by third laser beam116. The third laser beam116removes material of the electrically insulating layer structure102above the further window120, so that the first blind hole122formed by the first laser beam106and the second laser beam108in a top side region of the electrically insulating layer structure102is connected with second blind hole124formed by the third laser beam116in a bottom side of the electrically insulating layer structure102. Thereby, a common laser through hole extending through the entire electrically insulating layer structure102is formed with three laser shots (in contrast to four laser shots in the embodiment according toFIG. 12toFIG. 15). As can be taken from a detail215inFIG. 28, the described procedure may result in a slanted sidewall in the narrowest region of the laser through hole. The described procedure is very simple and quick, since three laser shots are enough for producing a laser through hole.

The laser through hole according toFIG. 28also shows a lateral offset, see position of the second blind hole124compared to first blind hole122. This results from the fact that, after the first and the second laser shots, the preform of the component carrier130(i.e. the processed panel) can be flipped (i.e. turned by 180°), before the third laser shot is carried out. This introduces a spatial inaccuracy in the lateral direction which results in the described offset.

Subsequently but not shown for the present embodiment, electrically conductive material138may be filled in the upper part of the recess132and in the lower part of the recess132so as to form a connected electrically conductive structure which extends through the entire through hole156.

FIG. 29shows the result of a further optional procedure following the procedure according toFIG. 26toFIG. 28but being executed prior to filling electrically conductive material138in the laser through hole. This procedure allows obtaining a more symmetric sidewall in a central portion of the through hole according to an exemplary embodiment of the invention. In this embodiment, the through hole shown inFIG. 28is extended by directing a fourth laser beam118having a size smaller than the width of the further window120directly onto an exposed surface of the electrically insulating layer structure102adjacent to the narrowest portion of the through hole. As can be taken from a detail217, the previously slanted sidewalls in the innermost portion (see detail215inFIG. 28) may be rendered more vertical or even fully vertical. Thus, the optional but advantageous fourth laser shot may render the through hole more symmetric in the bottleneck region. This reduces the stress area and allows a better and more reliable wire connection.

Summarizing, the embodiment ofFIG. 26toFIG. 29connects first blind hole122formed by the first laser beam106and the second laser beam108in a top side region of the electrically insulating layer structure102with second blind hole124formed in a bottom side region of the electrically insulating layer structure102by the third laser beam116only. Thereby, through hole156is formed which extends through the entire electrically insulating layer structure102. Thereafter, a narrowest portion of the through hole156can be rendered more vertical by fourth laser beam118having a smaller size than the other window120.

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