Reinforcement Structures With a Thermal Conductivity-Increasing Coating in the Resin Matrix, and Electrical Conductor Structure Which is Separate From the Coating

Abstract

Electronic device comprising an at least partially electrically insulating carrier structure, which comprises a resin matrix and reinforcement structures in the resin matrix, wherein the reinforcement structures are provided at least partially with a thermal conductivity increasing coating, and an electrically conducting structure at and/or in the carrier structure, wherein at least in an interconnecting section between the carrier structure and the electrically conducting structure, the carrier structure is free from reinforcement structures provided with the coating, such that the electrically conducting structure and the coating are arranged non-contactingly relative to each other.

Claims

1. Electronic device comprising: an at least partially electrically insulating carrier structure, which comprises a resin matrix and reinforcement structures in the resin matrix, wherein the reinforcement structures are at least partially provided with a thermal conductivity increasing coating; an electrically conducting structure at and/or in the carrier structure; wherein at least in an interconnecting section between the carrier structure and the electrically conducting structure, the carrier structure is free from reinforcement structures provided with the coating, such that the electrically conducting structure and the coating are arranged non-contactingly relative to each other.

2. Device according to claim 1, wherein the reinforcement structures comprise reinforcement fibres.

3. Device according to claim 2, wherein the reinforcement fibres are cross-linked with each other, with formation of cross-linking layers, which are oriented perpendicular to a thickness direction of the device.

4. Device according to claim 2, wherein the reinforcement fibres in the resin matrix are oriented anisotropically, such that thermal conduction in the electrically insulating carrier structure is effected anisotropically.

5. Device according to claim 4, wherein a first portion of the reinforcement fibres extends along a preferred direction, and a second portion of the reinforcement fibres extends along a second preferred direction, wherein the first preferred direction and the second preferred direction are arranged angularly to each other.

6. Device according to claim 5, wherein the first portion of the reinforcement fibres has a first ratio of a coating volume to the volume of the carrier structure 404 which first ratio differs from a second ratio of a coating volume of the second portion of the reinforcement fibres to the volume of the carrier structure.

7. Device according to claim 1, wherein at least one of the following is implemented: i) the reinforcement structures comprise reinforcement grains, ii) the reinforcement structures comprise hollow bodies, iii) the reinforcement structures comprise glass or consist thereof.

8.-9. (canceled)

10. Device according to claim 1, comprising a separation structure which is arranged, for a spatial separation, between the coated reinforcement structures and the electrically conducting structure.

11. Device according to claim 1, wherein at least one of the following is implemented: the coating is optically impermeable, the coating has a thickness in a range between 300 nm and 10 m.

12. (canceled)

13. Device according to claim 1, wherein the coating is a carbon coating comprising a mixture of sp.sup.2 and sp.sup.3 hybridized carbon, wherein the portion of sp.sup.2 hybridized carbon is in a range between 30 and 65 percentage by weight, and the portion of sp.sup.3 hybridized carbon is in a range between 20 and 70 percentage by weight.

14. (canceled)

15. Device according to claim 1, wherein the reinforcement structures provided with the coating have a thermal conductivity in a range between 1 W/mK and 45 W/mK.

16. Device according to claim 1, wherein the reinforcement structures provided with the coating are jacketed with resin and the electrically conducting structure is arranged on and/or above the resin jacket, in order to thus separate the electrically conducting structure non-contactingly from the coating.

17. Device according to claim 1, wherein at least one of the following is implemented: the electrically insulating carrier structure comprises prepreg material, the carrier structure is a resinous board, the electrically conducting structure comprises copper or consists thereof, the device is formed as a printed circuit board.

18.-19. (canceled)

20. Device according to claim 1, comprising an electronic component (402), which is embedded in the carrier structure (102) and is coupled electrically conductingly with the electrically conducting structure, wherein the electronic component is selected from a group that consists of an active electronic component and a passive electric component, as one from a group that consists of a filter, a voltage converter, a semiconductor chip, a storage module, a capacitor, an ohmic resistor, an inductor, a sensor and a high-frequency component.

21.-22. (canceled)

23. Device according to claim 1, wherein the carrier structure is formed of a plurality of layers that are arranged on top of each other, and wherein the device further comprises at least one further electronically conducting structure between the layers.

24. Method for manufacturing an electronic device, wherein the method comprises: forming an at least partially electrically insulating carrier structure, which comprises a resin matrix and reinforcement structures in the resin matrix, wherein the reinforcement structures are provided at least partially with a thermal conductivity increasing coating; forming an electrically conducting structure at and/or in the carrier structure; wherein at least in an interconnecting section between the carrier structure and the electrically conducting structure, the carrier structure is kept free from reinforcement structures provided with the coating, such that the electrically conducting structure and the coating are arranged non-contactingly relative to each other.

25. Method according to claim 24, wherein the electrically insulating carrier structure is formed by providing the reinforcement structures WO individually with the thermal conductivity increasing coating, by cross-linking the coated reinforcement structures with each other, and by impregnating the reinforcement structures, which are coated and cross-linked with each other, with resin.

26. Method according to claim 24, wherein the electrically conducting carrier structure is formed by cross-linking the reinforcement structures with each other, by providing the cross-linked reinforcement structures jointly with the thermal conductivity increasing coating, and by impregnating the reinforcement structures, which are coated and cross-linked with each other, with resin.

27. Method according to claim 24, wherein the reinforcement structures are provided with the coating by sputtering or plasma-enhanced chemical vapour deposition.

28. Method according to claim 24, wherein a first portion of the reinforcement structures is aligned along a first extension direction, and a second portion of the reinforcement structures is aligned along a second extension direction, and wherein a distance between neighbouring reinforcement structures of the first portion is provided for differently from a distance between neighbouring reinforcement structures of the second portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In the following, exemplary embodiments of the present invention are described in detail with reference to the following figures.

[0041] FIG. 1 shows a cross-sectional view of an electronic device according to an exemplary embodiment example of the invention.

[0042] FIG. 2 shows a plan view of reinforcement fibres of an electronic device, which fibres are cross-linked with each other to a texture, according to an exemplary embodiment example of the invention.

[0043] FIG. 3 shows a phase diagram, which illustrates the contributions of sp.sup.2 hybridized carbon, spa hybridized carbon and hydrogen of a coating material for the coating of reinforcement structures in a resin matrix, according to an exemplary embodiment of the invention.

[0044] FIG. 4 shows a cross-sectional view of an electronic device according to another exemplary embodiment example of the invention.

[0045] FIG. 5 shows reinforcement fibres that are aligned along a first extension direction and reinforcement fibres that are aligned along a second extension direction that is oriented angularly thereto, with anisotropic heat conductivity properties of an electronic device according to an exemplary embodiment example of the invention.

[0046] FIG. 6 shows a plan view of a mat made from reinforcement fibres that are aligned along a first extension direction and reinforcement fibres that are aligned along a second extension direction that is oriented angularly thereto, of an electronic device according to an exemplary embodiment example of the invention, wherein a coating with heat conductivity increasing coating material has been performed only after the formation of the mat.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

[0047] Same or similar components in different figures are provided with the same reference signs.

[0048] Before example embodiments of the invention are described with reference to the figures, some general aspects of the invention shall be explained yet:

[0049] Example embodiment s are based on the idea to coat (particularly glass-) fibres, from which prepreg (FR4) can be manufactured, with a heat conducting coating (for example made from DLC). Thereby, both the heat distribution and also the heat dissipation in an electronic device can be adjusted.

[0050] According to a first aspect of the invention, an adjustment of the anisotropy of the heat conduction in an electronic device can advantageously be obtained by means of a highly thermally conductive coating. According to the invention, this can be solved by providing a print material, which has different thermal conductivity values in the x- and y-direction (i.e. in two directions that are orthogonal to the z- or thickness-direction of the print). This can be achieved by coating glass fibres, for example, with a specialized form of carbon (particularly, a hydrogenous amorphous carbon layer made of a mixture of sp.sup.2 and spa hybridized carbon atoms, alternatively or additionally nitrides, oxides, such as, for example, aluminium nitride or aluminium oxide, copper oxide, etc.). Thereby, this thermally conducting layer may be deposited on the glass fibres by means of PVD or PACVD in layer thicknesses of, for example, at maximum 10 m. Astonishingly, it was found, that different yarn densities can be obtained in the x- and y-direction by according weaving and fabrication techniques, which leads to a different heat conductivity and heat distribution in the x- and in the y-direction. This anisotropic heat conduction may be conserved with the embedding in the finished print. Heat conductivities/heat distributions of the utilized texture of more than 0.8 W/mK up to 50 W/mK are achieved by this layer. Such devices can be used as basic materials, which may be applied for products, in which heat is generated during operation and is to be dissipated and/or to be forced apart (or spread). From the manufacturing standpoint it may be simple to produce an anisotropic heat conduction by a mechanical distorting or straining of prepregs (asymmetry of the texture in the x- and y-direction).

[0051] According to a second aspect of the invention, coated fibres that are impermeable for light can be applied. Prints can be formed from electrically isolating carrier materials, on which at least one copper layer may be deposited. These carrier materials may often be formed from transparent mats of glass fibres, which may be impregnated in epoxy resin (FR4, FR refers to flame resistant), for example with layer thicknesses of at least 35 m. The increasing miniaturization of electronics and of chip technology has led to the power consumption of electronic components having become smaller. At present, operational amplifiers having input currents in the range of Femtoamperes are available, and values significantly below this may be typical in integrated circuits. Beside the requirements for very high isolation resistances, recently also the set of problems of the photo effect (photoelectric effect: By the impinging of a photon, an electron is released) may be posed. This set of problems may appear above all for laid open chips and visually accessible components. Especially, in the embedding of components in printed circuit boards, the relatively good light transmission (or transparancy) of FR4 may become a big problem: The glass fibres (of the FR4 materials) may function like optical waveguides and thus may guide the photons, which therefore may lead to disturbances at the signal level. According to an embodiment example of the invention, this problem can be solved by coating the fibres with a material that is impermeable for light (for example amorphous carbon). By forming such layers, the transparency of the FR4 material may be lowered and thus also the conduction of the photons in the glass fibres may be prevented or strongly suppressed. Astonishingly, also an improved heat dissipation and heat distribution in the FR4 material can thereby be achieved as a side effect.

[0052] According to a third aspect of the invention, balls (or spheres) and hollow balls, which are made of glass and have a heat dissipating coating, can be applied. This may lead to a simple manufacturing method and (when using hollow bodies as the reinforcement structures) to a light-weight circuit board.

[0053] In particular and according to an example embodiment of the invention, a material for circuit boards, a print material or a substrate material can be provided, which may be formed of a resin component and a reinforcement component. The reinforcement components may be provided with a coating, which may be a hydrogenous amorphous carbon layer consisting of a mixture of sp.sup.2 and sp.sup.3 hybridized carbon atoms. The heat conduction/heat distribution of the applied texture can lie above 0.8 W/mK and below 50 W/mK. The heat conductivity in the x- and the y-direction may be unequal from one another (anisotropic heat distribution). For example, the difference of heat conductivity x:y may be larger than 1.1:1, preferably larger than 1.5:1, further preferably larger than 2:1. The proportion of sp.sup.2 hybridized carbon atoms can amount to 30 to 65 percent per weight and the proportion of sp.sup.3 hybridized carbon atoms can amount to 20 to 70 percent by weight. In particular, the proportion of sp.sup.2 hybridized carbon atoms can amount 40 to 60 percent by weight, and the proportion of sp.sup.3 hybridized carbon atoms can amount 25 to 40 percent by weight. The coating can be impermeable for light, whereby electromagnetic radiation may not pass (may not transmit). For example, the impermeability for light can be higher than for window glass by at least a factor of ten.

[0054] FIG. 1 shows a cross-sectional view of an electronic device 100 that is formed as a printed circuit board, according to an exemplary embodiment of the invention.

[0055] The electronic device 100 shown in FIG. 1 has a plate-shapedly formed, electrically isolating carrier structure 102, which comprises a resin matrix 104 formed from epoxy resin, and reinforcing structures 106 formed as glass fibres, which are embedded in the resin matrix 104. The reinforcement structures 106 may be jacketed with a thermally highly conductive coating 108 made of DLC (Diamond Like Carbon).

[0056] Conductor pathways made from copper may be formed on both opposite main surfaces of the carrier structure 102 as an electrically conductive structure 110.

[0057] As can be seen in FIG. 1, in a respective interconnection section between the carrier structure 102 and the respective electrically conductive structure 110, the carrier structure 102 is free from reinforcement structures 106 that are provided with the coating 108. Furthermore, the reinforcement structures 106 that are provided with the coating 108 may be jacketed with resin and the electrically conductive structure 110 may be provided on the resin jacket, in order to also thereby separate the electrically conducting structure 110 from the coating 108 free of contact (or non-contactingly). Accordingly, the electrically conductive structure 110 and the coating 108 may be non-contacting to one another, i.e. without straight or direct physical contact to each other, localized or positioned at the electronic device 100. An undesired release of the electrically conductive structure 110 from the coating 108, which would adhere to the electrically conductive structure 110 only poorly, may thereby be avoided.

[0058] The reinforcing structures 106, which may be wave-like (or undulating) in the shown embodiment example, may be cross-linked with one another with the formation of a respective roving, such that cross-linking layers or cross-linking planes may be formed, which may be oriented perpendicular to a thickness direction 116 of the board-like device 100. The reinforcement structures 106 may be aligned anisotropically in the resin matrix 104, such that heat conduction in the electrically isolating carrier structure 106 may be effected anisotropically. Stated more precisely, a first portion 112 of the reinforcement fibres 106 may extend along a first preferred direction (a horizontal direction according to FIG. 1), whereas a second portion 114 of the reinforcement fibres 106 may extend along a second preferred direction (perpendicular to the paper plane according to FIG. 1).

[0059] The coating 108 made of DLC may be impermeable for electromagnetic radiation in the visible range, i.e. for optical light. For this purpose, the coating 108 may have a sufficiently high thickness of, for example, 1 m. A coating 108 of such thickness also may lead to an efficient thermal dissipation of heat, which may be incurred in the operation of the electronic device 100 due to the propagating electronic signals, etc. The reinforcement structures 106 provided with the coating 108 may have jointly on average a thermal conductivity of, for example, about 10 W/mK.

[0060] Since the coating 108 may be in contact only with the material of the reinforcement structures 106 and the resin material of the resin matrix 104, but not with the copper material of the electrically conductive structure 110, a delamination of the copper from the electronic device 100 may be avoided, because a direct contact of the copper with the DLC material, which may be incompatible therewith, may be made impossible. Due to the alignment of the first portion 112 and the second portion 114 of the reinforcement structures 106, which may be completely jacketed with the coating 108, along mutually orthogonal directions, also preferred directions for the dissipation of thermal energy in the horizontal direction according to FIG. 1 and in a direction perpendicular to the paper plane according to FIG. 1 may be specified (or predetermined), such that heat dissipation properties, which may depend on the direction and may be precisely definable, can be adjusted. By selecting a sufficiently thick coating 108, optically intransparent properties of the coated reinforcement structures 106 can be achieved, such that an undesired coupling-in of parasitically generated photons in the glass fibre reinforcement structures 106, that otherwise may act factually as light guides, may be avoided, which otherwise could disturb the electrical quality of the electronic device 100.

[0061] FIG. 2 shows a plan view of reinforcement structures 106 (in the form of fibres), which are cross-linked with each other as a texture (or webbing), of an electronic device 100 according to an exemplary embodiment example of the invention. According to FIG. 2, the reinforcement structures 106 may form a mechanically robust mat with good stability and heat dissipation properties.

[0062] FIG. 3 shows a phase diagram 300, which shows the contributions of sp.sup.2 hybridized carbon, sp.sup.3 hybridized carbon and hydrogen of a coating material for the coating of reinforcement structures 106 in a resin matrix 104, according to an exemplary embodiment example of the invention.

[0063] According to the phase diagram 300, the coating 108 may be a hydrogenous (or hydrogen-containing) (H) amorphous carbon coating comprising a mixture of sp.sup.2 and sp.sup.3 hybridized carbon. Preferably, the proportion of sp.sup.2 hybridized carbon may be in a range between 40 and 60 percentage by weight of the coating 108, the proportion of sp.sup.3 hybridized carbon may be in a range between 25 and 40 percentage by weight of the coating 108, and the proportion of hydrogen may be above 10% (but preferably not above 40%). If sputtering/PVD is employed for the manufacture of the coating 108, the proportion of sp.sup.2 hybridized carbon may be high. In contrast, if PECVD is employed for the manufacture of the coating, a higher proportion of hydrogen may be obtained. A high thermal conductivity of the coating 108 can be achieved using a high proportion of sp.sup.2 and sp.sup.3 hybridized carbon. A mechanically stable coating 108 having a relatively high layer thickness may be manufacturable with a high proportion of hydrogen. The mechanical and thermal properties of the coating 108 can be adjusted precisely by the selection of the manufacturing method (for example, also the adjustment of the precise process parameters or, if applicable, combinations of the two mentioned manufacturing methods). A composition, which may be particularly advantageous in this respect, is represented in FIG. 3 as an area, which is referenced with the reference numeral 302.

[0064] FIG. 4 shows a cross-sectional view of an electronic device 100 according to another exemplary embodiment example of the invention.

[0065] In contrast to the electronic device 100 shown in FIG. 1, in the electronic device 100 according to FIG. 4, a plurality of separation structures 400 (here formed as separation layers) which may be formed from resin, are conceived, which may be arranged as spacers (or distance pieces) for a spatial separation between the coated reinforcement structures 106 and the electrically conducting structure 110.

[0066] According to FIG. 4, the reinforcement structures 106 may be formed as ball-shaped reinforcement grains, which can be realized selectively as massive bodies (if, for example, a particularly high mechanical stability is desired) or as hollow bodies (if, for example, a particularly low weight is desired).

[0067] In the electronic device 100, stated more precisely in the carrier structure 102 thereof, an electronic component 402 (for example a semiconductor storage) may be embedded, which may comprise an upper side and a lower side electrically conducting pad 404. The pads 404 may be coupled electrically conductingly with the electrically conductive structure 110 by means of a vertical via 408. In order to suppress (or prevent) a direct contact between the pads 404 made for example from copper or the vias 408 formed, for example, from copper and the jacketing 108 of the reinforcement structures 106, the vias 408 and the pads 404 may be surrounded on the side and/or circumferentially by an electrically conducting spacer structure 410.

[0068] FIG. 5 shows reinforcement structures 106, which are aligned along a first extension direction 500, and reinforcement structures 106, which are aligned along a second extension direction 502 that is oriented angularly thereto (see the acute angle ), having anisotropic heat conductivity properties of an electronic device 100 according to an exemplary embodiment example of the invention.

[0069] The first portion 112 of the reinforcement fibres 106 may have a ratio of a coating volume to the taken volume of the carrier structure 102, which may be smaller than a ratio of the coating volume to the taken volume of the carrier structure of the second portion 114 of the reinforcement fibres 106. The spatial density of the reinforcement fibres 106 of the first portion 112 may be lower than the spatial density of the reinforcement fibres 106 of the second portion 114. Thus, also the pro rata (or partial) coating volume of the second portion 114 in relation to the total carrier structure 102 may also be larger than in the case of the first portion 112. According to FIG. 5, the heat conduction may thus be effected anisotropically, i.e. with a higher efficiency along the second extension direction 502 in comparison to the first extension direction 500.

[0070] FIG. 6 shows a mat 600 of reinforcement structures 106, which are aligned along a first extension direction 500, and reinforcement structures 106, which are aligned along a second extension direction 502 that is oriented angularly thereto, of an electronic device 100 according to an exemplary embodiment example of the invention, wherein a coating 108 having a heat conductivity increasing coating material is produced only after the formation of the mat 600. Due to this manufacturing method, the reinforcement structures that intersect (or cross) each other may be mechanically connected with each other by the coating 108. The mat 600 can then be impregnated in resin, which can be hardened subsequently. The produced composite can then be compressed with other components (for example with copper layers), if needed, and can be re-treated if applicable (for example, structured). If a thickness d of the coating 108 amounts to between 750 nm and 10 m, both an advantageous intransparency of the coating 108 for electromagnetic radiation in a broad wavelength range from infrared via the visible to the ultraviolet range may be achievable, and a good adhesion of the coating 108 to the reinforcement structures 106 may be achievable.

[0071] Supplementary, it is to be noted that comprising or having does not exclude other elements or steps, and that a or an does not exclude a plurality. It is further to be noted that features or steps, which have been described with reference to one of the embodiment examples above, can be applied also in combination with other features or steps of other embodiment examples described above. Reference numerals in the claims are not to be considered as limitations.