Magnetic material filled printed circuit boards and printed circuit board stators

Abstract

The dielectric substrate may support conductive traces forming a winding of at least one pole of a planar armature of an axial flux machine. At least a portion of the dielectric substrate adapted to be positioned within an annular active region of the axial flux machine may include a soft magnetic material. Such a planar armature may be manufactured, for example, by forming conductive traces on a dielectric substrate and filling gaps between the conductive traces with at least one epoxy material in which the soft magnetic material is embedded.

Description

Background Art

[0001] Several patents, such as US Pat. Nos. 7,109,625 ("the '625 patent") and 10,170,953 ("the '953 patent"), which are incorporated herein by reference in their entireties, describe permanent magnet axial flux electric machines and generators featuring a planar printed circuit board stator assembly between rotors. Summary of the invention

[0002] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features, nor is it intended to limit the scope of the claims included herein.

[0003] According to an example embodiment, a planar armature of an axial flux machine includes a dielectric substrate including at least a first portion adapted to be positioned within an annular active region of the axial flux machine, wherein at least the first portion includes a soft magnetic material; and further including conductive traces supported by the dielectric substrate, the conductive traces forming a winding of at least one pole of the planar armature.

[0004] According to another example embodiment, a printed circuit board includes a dielectric substrate and a conductive trace supported by the dielectric substrate, wherein at least a first portion of the dielectric substrate includes a soft magnetic material.

[0005] According to yet another example embodiment, a method for forming a planar armature of an axial flux machine includes forming conductive traces on a dielectric substrate, the conductive traces forming windings for at least one pole of the planar armature, and filling interstitial gaps between the conductive traces with at least one epoxy material having a soft magnetic material embedded therein. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The objects, aspects, features and advantages of the embodiments disclosed herein will become more apparent from the following detailed description, the appended claims and the accompanying drawings, in which the same reference numerals identify similar or identical elements. Reference numerals introduced in the specification in association with the drawings may be repeated in one or more subsequent drawings without further explanation in the specification to provide context for other features, and not every element is labeled in every drawing. The drawings are not necessarily drawn to scale, but rather emphasize the illustration of the embodiments, principles and concepts. The drawings are not intended to limit the scope of the claims included herein.

[0007] Figure 1 An exploded view of the internal components of an example axial flux machine having a planar stator is shown;

[0008] Figure 2 Shown include Figure 1 a cross-sectional view of an axial flux machine showing the components shown;

[0009] Figure 3 It is shown that the axial flux machine, such as Figure 1 and 2 An example planar stator employed in an axial flux machine is shown;

[0010] Figure 4 A schematic diagram showing the material arrangement in a composite structure of a conventional printed circuit board;

[0011] Figure 5 Shows Figure 4 A schematic diagram of how several copies of the composite structure shown may be repeated in a stack-up of a conventional composite printed circuit board;

[0012] Figure 6 Composite structures (e.g., for use in a planar stator) are shown in which magnetic composite materials are disposed in gaps between copper features;

[0013] Figure 7 Shows Figure 6 how the composite structure of the embodiment of the present invention is implemented as a repeating unit to construct an actual composite printed circuit board according to some embodiments of the present invention; and

[0014] Figure 8 is a cross-sectional view of a sample from a planar stator with six conductive layers, showing the deposition of magnetic composite material in the gaps between radial traces. DETAILED DESCRIPTION

[0015] Unlike conventionally constructed machines, where the armature is typically wound using wire around a core of soft magnetic material, the windings in a printed circuit board stator (such as described in the '625 patent and the '953 patent, incorporated by reference above) are supported by a non-magnetic composite material. This composite material is typically composed of fiberglass cloth, epoxy resin, and copper for the winding and thermal structure. Therefore, this type of machine is often described as an "air core" machine.

[0016] The inventors have recognized and appreciated that such planar printed circuit board stators can be significantly improved by introducing one or more soft magnetic materials into the stator substrate. Several examples of planar circuit board stators enhanced with such soft magnetic materials are described herein, as well as several example techniques for producing such stators.

[0017] Figure 1 and Figure 2 An exploded view and a cross-sectional view, respectively, of a planar stator axial flux machine 100 of the type disclosed in the '625 patent and the '953 patent are shown. As shown in these figures, a planar stator 102 may be placed in the gap of a magnetic circuit established by components of a rotor. Figure 3 1 shows a top view of an example planar stator 102 that may be employed in the machine 100. Figure 1As best shown, the rotor may include magnets 104a, 104b and support structures 106a, 106b that together form a pair of rotor assemblies 108a, 108b that may be attached to a rotor shaft 110. Figure 2 As shown, the outer edge 112 of the planar stator 102 can be fixedly secured to the housing 114 (e.g., by being retained between corresponding portions 114a, 114b of the housing 114), while the rotor shaft 110 (to which the rotor assemblies 108a, 108b are attached) can be rotatable relative to the housing 114 (e.g., via bearings 116).

[0018] like Figure 3 As shown, the planar stator 102 may include radial traces 302. The portion of the planar stator 102 having such radial features, i.e., an annular region extending between a radial distance r1 (measured from a center point 304 of the planar stator 102, which coincides with the axis of rotation of the rotor of the machine 100) and a radial distance r2 (also measured from the center point 304), is located within the "active" region of the machine 100, i.e., it is primarily responsible for the generation of torque in the machine 100. The inner and outer radii of the magnets 104 attached to the rotor of the machine 100 are typically located at or near the radial distance r1 (measured from the axis of rotation of the stator) and the radial distance r2 (also measured from the axis of rotation of the stator), respectively, thereby generating an axially oriented magnetic flux within the annular active region. The remaining features, such as the inner and outer end turns 306 radially adjacent to the annular active region of the planar stator 102 (which may be on different layers of the planar stator 102 ) may exist only to connect the radial traces 302 in series and parallel combinations and deliver the associated currents and voltages to the terminals 308 of the planar stator 102 .

[0019] In motor mode, the current density of the synchronous rotation about the rotation axis of the rotor can be controlled by the controller 118 (eg Figure 1 The electric current density (as shown) is applied to the planar stator 102. This current density interacts with the magnetic flux in the gap from the rotor assemblies 108a, 108b to cause a torque of electromagnetic origin. The controller 118 can be operated so that the energy conversion achieved by the structure is bidirectional, that is, the motor can absorb energy from the mechanical terminals and deliver it to the electrical terminals, or it can deliver energy to the mechanical terminals. Under proper control, this type of machine can simulate a variety of mechanical loads, including friction components, rotational inertia, etc.

[0020] Figure 4 A schematic diagram of the arrangement of materials in a composite structure 400 of a conventional printed circuit board having relatively high profile traces is shown. Such a structure may be used, for example, to form a conventional planar stator for an axial flux machine, such as Figure 1-3 A planar stator 102 of an axial flux machine 100 is shown. Figure 4The stackup shown focuses on the interface between two copper clad material layers 402a, 402b (e.g., preformed glass-epoxy, copper sheets) and opposing copper features 404 etched on the two copper clad layers. In some embodiments, for example, each layer 402 can be formed by etching a corresponding copper clad laminate (CCL) sheet, such as FR-4 CCL, to form the copper features 404. As shown, each layer 402 can include a dielectric core layer 406 (e.g., fiberglass cloth) to which the etched copper sheet (including the copper features 404) is adhered (e.g., by epoxy). Although Figure 4 Not shown, but understood, the opposite side of the dielectric core layer 406 shown may also have a copper sheet adhered thereto (perhaps etched to form additional copper features 404). This type of etched CCL sheet may be used, for example, to form the following bonding Figure 5 and 7 The copper features 404 may correspond to radial traces 302 within the "active region" of the planar stator 102 extending between a first radius r1 and a second radius r2, for example. Figure 3 shown.

[0021] like Figure 4 As shown, in order to bond the corresponding layers 402a, 402b together, achieve a flat composite structure 400, and provide a dielectric between the opposing copper features 404, several layers of "prepreg" 408 can be inserted between the etched copper surfaces. "Prepreg" is a fiberglass cloth impregnated with epoxy resin. As shown, epoxy 410 from prepreg 408 can flow out from the high profile contact area into the gaps between active area traces. Sufficient prepreg can be used so that the gaps can be filled when the composite structure 400 is compressed and bonded together.

[0022] Figure 5 Shows Figure 4 A schematic diagram of how several copies of the composite structure 400 may be included in the stack-up of a typical composite printed board structure 500 , which in this example has twelve layers of conductive material including, for example, copper features 404 , is shown.

[0023] Simply put, in Figure 1 and 2 In a machine of the type shown, the rotor supports the magnetic circuit in a rotating frame having a gap. A planar stator 102 is located in the gap, and the windings on the planar stator 102 are associated with the magnetic flux from the rotor. In a stationary state, the solution of the magnetic flux in the gap is essentially independent of the presence of the planar stator 102, because the materials used in the stator construction (e.g. Figure 4 and 5The dielectric core layer 406, prepreg 408 and epoxy resin 410 shown have a magnetic permeability that is essentially the same as free space or "air". More traditionally constructed machines integrate the windings with soft magnetic materials, which are typically made from laminations of special steels. This material participates in the magnetic circuit. However, when a soft magnetic structure is integrated with a stator in a permanent magnet brushless machine, for example, the steel is subject to a significantly time-varying magnetic flux, which tends to drive various loss mechanisms in the soft magnetic material. This is one of the reasons why the material used in such machines is typically made from laminated stampings that reduce losses associated with eddy currents in the magnetic material. The incorporation of soft magnetic materials in a typical steel lamination construction brings many disadvantages, including processing costs, winding limitations (fill factor), electrical and acoustic noise, electrical insulation requirements, moving masses, and thermal issues.

[0024] The advantage is that utilization of the core can reduce or, in some cases, eliminate the need for economically sensitive rare earth hard magnetic materials. Additionally, independent of the hard magnetic material, incorporation of the core can improve certain aspects of performance in trade-offs with other aspects. For illustrative purposes, consider a lossless machine that transforms electrical variables to a rotating frame—an ideal rectified machine. In this case, the machine is characterized by a single constant that relates torque to current (K t ) and voltage or back EMF vs. speed (K v ). In appropriate units and quantities, these constants are equal. If the constant is made larger, less current will provide a given torque, and a lower speed will result in a given terminal voltage.

[0025] The back EMF of the machine and the constant relating the machine current to the torque can be derived from the magnetic flux associated with the number of turns. In particular, as a consequence of Maxwell's equations for the magneto-quasistatic case, the number of turns associated with the magnetic flux λ produces the voltage

[0026]

[0027] Furthermore, if the magnetic flux associated with the stationary geometry of the number of turns (in the stator) is changed by orienting the rotor at an angle θ relative to the stator, then the above equation becomes

[0028]

[0029] In permanent magnet motors, There are two components to consider. Contribution One source of the magnetic flux λ1 originates from the magnets fixed in the rotor (θ is the angle of the rotor) and the state of the associated magnetic circuit. This is the most important term in air core machines. Contribution The other component of λ2 involves the change in magnetic flux related to the number of turns itself. For this component, λ2 = L(θ), it can be considered as an inductance related to the angle.

[0030] At fixed speed and steady-state conditions, The importance of is that it provides a relationship between speed and voltage which determines the performance characteristics of the motor. This can be analyzed on a case-by-case basis, for example, the voltage of a winding is the The accumulation of contributions.

[0031] because is a function of θ and is therefore periodic, so it has a Fourier series. In some cases, The term can be well approximated as the first term of the series. In this case, the terminal voltage of a machine with n poles and mechanically rotating at frequency ω can be expressed as:

[0032] v(t)≈K sin(nωt+θ0)ω

[0033] In this equation, ω is the mechanical rotation frequency, n is the number of poles of the machine, nω is the electrical frequency, t is time, θ0 is the angular displacement, and Ksin(nωt+θ0) is the approximation on the winding The first term of the Fourier series of . Commutation of the machine effectively eliminates the sinusoidal dependence and exposes K—the contribution of the hard magnetic material, the state of the associated magnetic flux, and the theta-dependent inductance term—as a factor that can cause the machine to produce more voltage per unit speed, and more torque per ampere. Adding soft magnetic core material to an air core machine can increase the contribution component, thus usually increasing the K of the machine.

[0034] One possible approach to introducing soft magnetic core material into an air core machine is to replace the fiberglass substrate supporting the conductive traces (e.g., the dielectric core layer of a conventional CCL sheet) with a soft magnetic material. This material can be non-conductive and relatively hard, such as a ceramic insulator, such as soft ferrite. Since the material will be exposed to time-varying magnetic fields during machine operation, low-loss magnetic properties are desirable. In order to produce a circuit board structure having a ceramic insulator or the like as a supporting substrate, a flat conductive layer (e.g., a copper layer) can be disposed on either or both surfaces of a planar sheet of ceramic insulator material to produce a structure similar to a CCL sheet, and this conductive sheet can then be etched, for example using standard printed circuit board (PCB) processes, to form patterns of windings and / or other conductive traces for the poles of the armature.

[0035] The properties of the material families that meet these criteria, such as processing difficulty, can be mitigated toward embodiments that reduce the number of layers required to form a planar winding structure. The winding structure disclosed in the '953 patent, incorporated by reference above, can be implemented with as few as two conductive layers. Using a soft magnetic material as a substrate to support the windings of a planar stator may also have advantages in terms of permissible thermal conditions.

[0036] Another possible method of introducing soft magnetic core material into an air core machine is to integrate the core material with a printed circuit board as part of the manufacturing process. The advantage of this embodiment is that the technology and winding procedures of planar stators designed for printed circuit board processes are retained, as well as the inherent precision and scalability associated with such processes. In some such embodiments, one or more powdered soft magnetic materials can be combined with one or more carrier materials (e.g., low viscosity epoxy resin products) used as "fillers" in printed circuit boards to form a magnetic composite. This magnetic composite can thus form a soft magnetic core, thereby producing a planar armature with a dielectric substrate that supports conductive traces and also has integrated soft magnetic material in (at least) the required locations.

[0037] Figure 6 An example composite structure 600 is shown (e.g., for use in planar stator 102) in which a dielectric substrate (including dielectric core layer 406, magnetic composite material 602, and prepreg 408) supports conductive traces (i.e., copper features 404), and in which magnetic composite material 602 is disposed on copper features 404 (e.g., corresponding to Figure 3 The composite structure 600 may be formed with the radial traces 302 shown in FIG. Figure 4 4. The composite structure 400 shown is compared to the one shown in which the prepreg 408 and the associated epoxy 410 are disposed in the gaps between the copper features 404. Since these gaps are filled by the magnetic composite material 602 in the composite structure 600, the need for the prepreg 408 to fill these spaces may be reduced. Therefore, in some embodiments, the prepreg 408 may be used only to meet the dielectric requirements of the planar stator 102, i.e., electrical insulation between axially close copper features 404. In some embodiments, for example, only a single layer of prepreg 408 may be disposed between two etched copper clad material layers 402a, 402b. Figure 7 Shows Figure 6 A schematic diagram of how several copies of composite structure 600 are shown may be included in a stack-up of a novel composite printed board structure 700 having twelve layers of conductive material, such as magnetic composite material 602 including copper features 404 and integrated soft magnetic material, such as copper composite material 602, in the gaps between the copper features 404 in this example.

[0038] As mentioned above, Figure 3A top view of a typical planar stator 102 including traces forming stator windings is shown. The active region of the planar stator 102, i.e., the region where the rotor axial magnetic flux is applied, is described by a ring between radii r1 and r2. As shown, the active region of the planar stator 102 can include radial traces 302. In some embodiments, the magnetic composite material 602 described herein can be placed only within the active region, such as in the gaps between the radial traces 302. In other embodiments, the magnetic composite material 602 can be placed in other regions of the planar stator 102 in addition or alternatively.

[0039] Powdered soft magnetic materials are widely used to make components such as chokes, inductors, and transformers. Examples of products formed using such powdered soft magnetic materials include Kool Mu (aluminum silicon iron powder), MPP (molybdenum permalloy), Kool MμMAX, Kool Mu_Hf, Edge, High Flux, XFlux, and 75 Series, all available from Magnetics, headquartered in Pittsburgh, Pennsylvania. In these traditional applications, the powder is usually sintered or bonded to form a core, or has an embedded wire, or is in a form that a wire can be wound around it. This type of powdered soft magnetic material is available from a variety of sources. Examples include 40337 iron powder, 00170 iron powder, and 10214 iron powder, available from Alfa Aesar (part of Thermo Fisher Scientific) in Tewksbury, Massachusetts.

[0040] Eddy current losses in components comprising such powdered soft magnetic materials can be controlled by particle size, since the interfaces between the conductive particles can be made sparse, i.e., such that the particles tend not to form a larger conductive network. Magnetic losses also decrease with particle size relative to a bulk sample of the same material, since the collection of particles approximates individual domains with fewer domain-domain interactions. As the material particle size becomes very small (nanoscale, e.g., between 1 and 100 nanometers), new effects may become apparent. These effects are generally beneficial from a magnetic perspective, but can present challenges from a processing, mixing, and reactivity perspective with materials used for integration in a printed circuit board environment.

[0041] In some embodiments, in order to introduce powdered soft magnetic materials, such as those mentioned above, into a printed circuit board stator, a step can be used in which one or more such soft magnetic powders are mixed with one or more low viscosity epoxy resin products compatible with printed circuit board materials and processes to form a magnetic composite material 602, as described above. In some embodiments, a soft magnetic powder having an optimal magnetic particle size for a given application can be selected and / or such soft magnetic powder can be screened to control the size of the magnetic particles used. In some embodiments, for example, a magnetic powder having an average magnetic particle size (e.g., diameter) of 1 micron (μm), or 2 μm, or 5 μm, or 10 μm, or 20 μm, or 50 μm, or 100 μm can be used. In addition, in some embodiments, such magnetic powders can be screened additionally or alternatively so that the maximum size (e.g., diameter) of the magnetic particles they contain is less than 100 μm, or less than 50 μm, or less than 20 μm, or less than 10 μm, or less than 5 μm, or less than 2 μm, or less than 1 μm. As described above, eddy current losses in these materials can be controlled by controlling the size of the soft magnetic particles so that the interfaces between the individual particles are sufficiently sparse. In addition, by keeping the magnetic particles sufficiently small and / or sparse, the magnetic composite material 602 can be made non-conductive as a whole, even though the individual magnetic particles themselves may be conductive in some embodiments. Therefore, the magnetic composite material 602 can be used as an insulator between the individual conductive traces 302, 404 of the planar stator 102.

[0042] An example of a low viscosity epoxy product that can be mixed with such magnetic powder to form a magnetic composite material 602 is EMP110 Photoimageable Soldermask available from Electa Polymers Ltd. of Kent, England. Such magnetic composite material 602 can then be dispensed by standard processes into volumes in a printed circuit board (e.g., gaps between copper features 404) that would otherwise be filled with other materials (e.g., layers of prepreg 408 and / or epoxy 410) during manufacturing. The result of this method is a composite printed circuit board structure, e.g., Figure 7 The composite printed circuit board structure 700 shown includes a low-loss magnetic material, such as a magnetic composite material 602 .

[0043] In some embodiments, to make a trace, such as Figure 3 A planar composite stator of one or more powdered soft magnetic materials is integrated in the gaps between the radial traces 302 shown, and one of the copper-clad repeating units of the processing assembly, such as Figure 6There are two main steps that can be taken when placing one of the layers 402 shown. The first such step can be to place soft magnetic material, such as magnetic composite material 602, in the desired location and to place non-magnetic filler material in the location where magnetic material is not needed. An example of a non-magnetic filler material suitable for this purpose is the EMP110 Photoimageable Soldermask described above. In the construction of a planar armature, it may be desirable to confine the soft magnetic material, such as magnetic composite material 602, to the active region of the stator ( Figure 3 between r1 and r2 in the embodiment of the present invention), where interaction with the rotor is important. A second such step may be to level the layer 402 so that the layer 402 can be "stacked" with uniform results. Arrangements of the techniques described for these steps may have similar results.

[0044] In some embodiments, a separate CCL sheet, such as an FR-4 CCL board, may be etched with a desired winding pattern, as is done for a conventional planar stator, such as the type described in the '625 and '953 patents incorporated by reference above. A mixture of one or more epoxy resins and one or more powdered soft magnetic materials, such as the magnetic composite material 602 described above, may then be screened or placed over the active area of ​​the etched CCL sheet through a computer-controlled dispenser, such as in forming a Figure 3 302 of the planar stator 102 shown. In some embodiments, the magnetic composite material 602 can be excluded from areas where it is undesirable, such as outside the active areas of the planar stator 102, by depositing and partially curing a non-magnetic filler material in these areas before depositing the magnetic composite material 602 on the etched CCL sheet. The uncured material can then be mechanically leveled, such as by a scraper. Due to these processes, some material may be located on the copper traces and may extend beyond the level of the top of the traces.

[0045] In other embodiments, a separate CCL sheet, such as an FR-4 CCL board, may first be etched with an initial pattern to leave pores at desired locations for subsequently introduced magnetic materials. A mixture of one or more epoxy resins and one or more powdered soft magnetic materials, such as the magnetic composite material 602 described above, may then be screened, computer dispensed, or batch dispensed onto the initially etched CCL sheet and leveled, for example, by a scraper. Due to these processes, some material may be located on the copper portion of the CCL sheet that will form the traces of the planar stator 102. Subsequent etching of the remaining pattern may produce gaps and pores required for the stator circuit traces, which are not desired to be filled with magnetic materials. Such pores may then be filled with, for example, non-magnetic filling materials of the type described above. In some embodiments, the order of these etching and filling steps may be interchanged.

[0046] After the above steps, it may be necessary to remove excess non-magnetic filler material to allow assembly of a uniform sequence of layers 402. Since the copper traces of the planar stator 102 can be accurately described by the Gerber code used to prepare a CCL sheet with a trace pattern, in some embodiments, the same code can be translated into a control sequence for a laser that can flatten the magnetic composite material 602 and level the surface. A suitable laser for this process can effectively remove epoxy materials such as the magnetic composite material 602 or the non-magnetic filler material described above, but may be blocked by the copper traces underneath. Such lasers are used in standard PCB manufacturing to connect the inner layers of a printed circuit board. In other embodiments, the magnetic composite material 602 and / or the non-magnetic filler material can alternatively enter a cured state where the layers can be economically and effectively mechanically leveled to remove excess material.

[0047] The techniques disclosed herein can also be applied to make a planar printed circuit board armature that is thinner than an equivalent stator made using conventional techniques. This result can be achieved, for example, by filling the gaps with epoxy rather than epoxy loaded with magnetic material. Similar steps can be used in this embodiment to flatten the surface and remove excess material. A reduced number of pre-impregnated cloth layers, such as the prepreg 408 described above, can then be used in the stack.

[0048] Features and advantages of integrated soft magnetic core materials

[0049] Integrating the core material into the motor has many advantages, some of which have been noted previously. In particular, the construction herein can be automated in the construction of the PCB, as opposed to methods that require discrete magnetic cores to be placed in slots and / or holes in the PCB. The magnetic material can be effectively fixed in the PCB matrix.

[0050] In motor applications, the presence of core material can allow substitution of lower grade magnets and / or use of less magnetic material relative to a similar air core design. Trade-offs in moving mass, harmonics, and other motor parameters may also be involved. The presence of core material can allow more efficient use of armature reaction, such as in field weakening applications.

[0051] The disadvantage of this technology is that, unlike air core machines, there is a magnetic attraction between the stator and the rotor under stationary conditions. In the center of the gap, the magnetic material filled stator may be in an unstable equilibrium point. This may require, for example, a stator geometry that is inherently stiffer relative to the air core design.

[0052] There are many market opportunities for electric motors and generators that work well with inexpensive magnets or require very high torque density.

[0053] The benefits of incorporating magnetic materials described herein may apply to other kinds of electromagnetic devices and circuit elements. For example, inductors, transformers, inductive sensors, and energy harvesting devices with PCB trace windings may benefit from embedded core materials.

[0054] The technique of filling the gaps with soft magnetic material can also be used to manufacture printed circuit boards (including planar armatures) with high-profile copper features and reduced overall thickness. This has been put into practice. In a typical sample, a stator with a thickness of 0.0920 inches with a traditional layup and structure was remanufactured using this process to a thickness of 0.0695 inches. Reduced stator thickness can bring a variety of closely related machine performance trade-offs and benefits, including reduced magnet usage, higher efficiency, improved performance, loss reduction, and / or increased thermal performance.

[0055] Figure 8 is a cross-sectional view of a sample from a planar stator having six conductive layers, showing the deposition of magnetic composite material 602. The magnetic composite material 602 used to fill the gaps between the radial traces 302 is formed using a powder soft magnetic screened to a maximum size of 25 μm and then mixed with a low viscosity epoxy resin product, as described above. The area including the magnetic particles and the epoxy resin matrix in which these particles are fixed is obvious. In this prototype, the thickness of the prepreg 408 was not reduced to the extent that it could have been. If this were done, the relative content of the magnetic composite material 602 between the radial traces 302 would be significantly increased.

[0056] Having thus described several aspects of at least one embodiment, it will be appreciated that various changes, modifications and improvements will readily occur to those skilled in the art. These changes, modifications and improvements are intended to be a part of the present invention and are intended to be within the spirit and scope of the present invention. Therefore, the foregoing description and accompanying drawings are intended only as examples.

[0057] The various aspects of the present invention can be used alone, in combination or in various arrangements not specifically discussed in the foregoing embodiments, and therefore are not limited in the present application to the details and arrangements of the components shown in the foregoing description or drawings. For example, the aspects described in one embodiment can be combined with the aspects described in other embodiments in any manner.

[0058] In addition, the disclosed aspects may be embodied as methods, examples of which have been provided. The actions performed as part of the method may be ordered in any suitable manner. Thus, embodiments may be constructed in which the actions are performed in a different order than shown, which may include performing some actions simultaneously, even though the actions are shown as being sequential in the illustrative embodiments.

[0059] The use of ordinal terms such as "first", "second", "third", etc. in the claims to modify claim elements does not itself imply any priority, precedence or order of one claim element relative to another claim element or the temporal order of the actions of performing the method, but is merely used as a mark to distinguish one claimed element with a particular name from another element with the same name (but using an ordinal term) to distinguish the claim elements.

[0060] In addition, the words and terms used herein are for descriptive purposes and should not be considered limiting. "Including," "comprising," or "having," "containing," "involving," and variations thereof used herein are intended to encompass the items listed thereafter and their equivalents as well as additional items.

Claims

1. A planar armature of an axial flux machine, the planar armature comprising: a first layer comprising a first dielectric substrate; a second layer comprising a second dielectric substrate; as well as A third layer is provided between the first layer and the second layer, wherein the third layer comprises: a first electrically conductive track forming at least a first part of a winding of at least a first pole of the planar armature, a first quantity of a magnetic composite material disposed in gaps between first conductive traces within at least a first region of the third layer, wherein the magnetic composite material comprises particles of a soft magnetic material embedded within a first dielectric material, and wherein the first region is within an active region of an axial flux machine, and A second amount of a second dielectric material is disposed in at least a second region of the third layer, wherein the second dielectric material is free of soft magnetic material and the second region is positioned outside of the active region.

2. The planar armature of claim 1, wherein the soft magnetic material comprises powdered soft magnetic material.

3. The planar armature of claim 2, wherein the first dielectric material comprises epoxy.

4. The planar armature of claim 1, wherein the particles have a maximum diameter of 50 microns or less.

5. The planar armature of claim 1, wherein at least a portion of the magnetic composite material is disposed within an etched region of the copper clad laminate.

6. The planar armature of claim 1, wherein: The first conductive trace comprises a radial conductive trace within the active area, and The magnetic composite material is disposed in gaps between the radial conductive traces.

7. The planar armature of claim 3, wherein the second dielectric material comprises epoxy.

8. The planar armature of claim 1, wherein the second dielectric material comprises epoxy.

9. The planar armature of claim 1, wherein: The first dielectric substrate and the first conductive trace are components of a first etched copper clad laminate; the second dielectric substrate being a component of a second etched copper clad laminate, wherein the second etched copper clad laminate comprises a second conductive trace forming at least a second portion of a winding of a first pole of the planar armature; and The second conductive trace is disposed on a fourth layer of the planar armature, the fourth layer being disposed between the second layer and the third layer.

10. The planar armature of claim 9, further comprising: A fifth layer of prepreg is included, the fifth layer being disposed between the third layer and the fourth layer.

11. The planar armature of claim 10, further comprising: a third amount of magnetic composite material disposed in gaps between second conductive traces within at least a third region of the fourth layer, wherein the third region is positioned within an active region of the axial flux machine, and A fourth amount of a second dielectric material is disposed in at least a fourth region of the fourth layer, wherein the fourth region is located outside of the active region.

12. The planar armature of claim 11, wherein: A first conductive trace is disposed on a first side of a first etched copper clad laminate; and A third conductive trace is disposed on a second side of the first etched copper clad laminate opposite the first side, wherein the third conductive trace is disposed on a sixth layer of the planar armature and forms at least a third portion of a winding of a first pole of the planar armature.

13. The planar armature of claim 12, further comprising: a fifth amount of magnetic composite material disposed in gaps between third conductive traces within at least a fifth region of the sixth layer, wherein the fifth region is positioned within an active region of the axial flux machine, and A sixth amount of a second dielectric material is disposed in at least a sixth region of the sixth layer, wherein the sixth region is positioned outside of the active area.

14. The planar armature of claim 9, further comprising: a third amount of magnetic composite material disposed in gaps between second conductive traces within at least a third region of the fourth layer, wherein the third region is positioned within an active region of the axial flux machine, and A fourth amount of a second dielectric material is disposed in at least a fourth region of the fourth layer, wherein the fourth region is located outside of the active region.

15. The planar armature of claim 1, wherein: The first dielectric substrate and the first conductive trace are components of a first etched copper clad laminate; and The second dielectric substrate includes a prepreg.

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