Method and apparatus for increasing skin depth and reducing eddy currents in hybrid magnetic cores and composite metals using electroless plating technology

Abstract

The present invention relates to a closed hybrid magnetic material and a method for fabricating the same, which includes at least one magnetic material having at least one inner porous insulating layer, at least one of the voids being closed and filled with an environmental material, and the closed voids are formed by an electroless plating process.

Description

[Technical Field]

[0001] The present disclosure relates to a method and apparatus for increasing skin depth and reducing eddy currents in hybrid magnetic cores and composite metals using electroless plating techniques. [Background technology]

[0002] Power supply designers strive for smaller, lower cost, and lighter power supplies, and are often constrained by the requirements of the magnetic devices within the system. The introduction of hybrid magnetic materials led to the concept of imperfect insulation layers. Imperfect insulation layers allow magnetic layers to penetrate and connect, resulting in a small, low-cost, high-resistivity metal core suitable for many high-frequency applications. This is because the metal core provides a significant increase in directional resistivity compared to bulk magnetic materials.

[0003] However, the introduction of hybrid magnetic materials also brought new challenges, primarily with regard to the insulating layer. Despite breaking through the performance barriers of traditional low-cost materials, hybrid magnetic materials themselves have inherent limitations. The problem with insulating materials that allow surrounding layers to connect is that they are far from perfect insulators. Because the physical and cost advantages of hybrid insulating layers stem from their imperfections, increasing the insulating strength of imperfect insulating layers without sacrificing those advantages is a complex problem.

[0004] However, having a stronger insulating layer enables higher efficiency, smaller size, and higher frequency operation, further pushing the performance limits of hybrid magnetic materials and improving their performance. For example, in boost and buck converters, it is widely known that increasing the switching frequency reduces switching efficiency and increases switching losses. These inefficiencies are primarily due to the generation of eddy currents. However, having a stronger insulating layer suppresses the generation of eddy currents, allowing higher switching frequencies to be used within the components. As higher switching frequencies become available, components incorporating hybrid magnetic materials can be efficiently and directly connected to a variety of power sources, including lithium-ion batteries.

[0005] Therefore, in applications where currents (not just eddy currents, but any currents) flowing perpendicular to the layers in a composite are to be further suppressed, while maintaining low resistivity for currents flowing parallel to the layers, it may be beneficial to further increase the dielectric strength of the imperfectly insulated layers. Summary of the Invention

[0006] This application presents a method for fabricating a pinched void hybrid insulation layer with enhanced dielectric strength and the resulting device. As used herein, a "hybrid magnetic material" refers to a material having a pinched void, which is an insulating layer containing voids. These through-holes are typically filled with a non-insulating material that interconnects the layers through the insulating layer. The method described herein increases the dielectric strength of a pinched void hybrid insulation layer without relying on relatively expensive insulating polymers or epoxy films, or coatings applied at temperatures, pressures, or process conditions that are incompatible with epoxy plastics for semiconductor packaging, semiconductor wafers, or printed circuit boards. Thus, the device of the present invention is a hybrid magnetic material having at least one pinched void hybrid insulation layer. This hybrid magnetic material can be molded into various components, some of which may include wiring or traces. The improved dielectric strength increases the insulating layer's ability to reduce eddy current formation, thereby improving the overall composite skin depth of the component in which the hybrid magnetic material is incorporated.

[0007] The method includes depositing a hybrid insulating layer on a layer of a magnetic component. Following the formation of the hybrid insulating layer, a subsequent magnetic layer is formed on the previously deposited hybrid insulating layer by electroless plating (controlled autocatalytic deposition). Electroless plating is performed at least until the thickness of the new metal layer begins to close the voids in the hybrid insulating layer. Electroless plating may continue to produce the component layer, or electroplating or other means may be used to finish the subsequent component metal layer.

[0008] The resulting device is a hybrid magnetic material with a closed-gap insulating layer that can be formed into a component or component part. Unlike conventional hybrid insulating layers, where an electroplated magnetic material is subsequently deposited, some voids are filled, but not all of them are completely filled with electroless-plated metal. These voids may contain air, liquid, and oxides of the surrounding metal, and in most cases contain some aspect of the electroless plating or pre-electroless plating environment. The resistivity of the closed voids is much higher than that of nickel-iron or other magnetic metals, which differs from standard electroplating where the voids are filled with metal. The result is an improved resistivity for the insulating layer of the hybrid magnetic material, improving its function as an insulator. Experimental data suggests that the increase in resistivity when subsequent layers are formed electrolessly, as in the present invention, is at least two orders of magnitude higher than hybrid layers formed by electroplating after CCVD SiO2 deposition.

[0009] The device obtained in the present invention is called a blocked hybrid magnetic material because it blocks the voids in the incomplete insulating layer. The blocked hybrid material can have stronger inherent conductivity, skin effect, BH curve, B_SAT, and strong inherent directional impedance compared to conventional hybrid materials (i.e., hybrid materials that proceed directly from insulating layer formation to electroplating). [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of a particle hybrid insulating layer on a magnetic material. [Figure 2] FIG. 2 is a cross-sectional view of metal deposited by electroless plating on a particle insulating layer. [Figure 3] FIG. 3 is a cross-sectional view of a closed interparticle void. [Figure 4] FIG. 4 is a cross-sectional view of unblocked interparticle voids. [Figure 5]FIG. 5 is a cross-sectional view of a partially blocked interparticle void. [Figure 6] FIG. 6 is a cross-sectional view of a closed non-interparticle void space. [Figure 7] FIG. 7 is a cross-sectional view of an electroplated metal layer on a particle hybrid insulating layer that previously underwent electroless plating. [Figure 8] FIG. 8 is a flow chart illustrating cross-sectional views of steps in an additive part manufacturing process incorporating the method of the present invention. [Figure 9] FIG. 9 is a flow chart illustrating cross-sectional views of steps in an additive component manufacturing process for a structure combining a conventional hybrid material insulation layer and a closed hybrid insulation layer. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention involves forming magnetic components using hybrid magnetic materials, in which a hybrid insulating layer is pinched using an electroless insulation process to form a pinched gap hybrid magnetic material. The method of the present invention is particularly useful for achieving high-frequency magnetic components by providing a robust, low-cost insulating layer that can reduce eddy currents and increase the effective skin depth of the component. The method is also useful for fabricating high-frequency cores by suppressing eddy current generation, thereby reducing energy losses within the core. Furthermore, the method can achieve insulation resistivity that is more than twice that of conventional hybrid materials, enabling the realization of magnetic cores with higher performance and smaller size.

[0012] It is worth briefly discussing the physical properties of common hybrid materials. Hybrid materials have an incomplete insulating layer. This insulating layer can be produced by several methods, but the two most economically feasible methods are chemical combustion vapor deposition (CCVD) and inkjet printing. In CCVD, the insulating layer contains particles with randomly located voids between these particles, although the voids can be controlled to some extent by controlling the thickness of the insulating layer. In inkjet printing, the insulating layer is generally a solid insulating sheet with intentionally located voids. In both methods of producing an incomplete insulating layer, voids exist that penetrate the insulating layer, and these voids are filled when subsequent non-insulating layers are formed. Such hybrid materials have a much higher vertical resistivity than typical bulk materials.

[0013] This increase in resistivity in the perpendicular direction increases the specific eddy current loss per unit volume of the hybrid magnetic material (P ec,sp ) is significantly reduced, where ρ core is the resistivity of the stack.

[0014] JPEG2026502579000002.jpg19156

[0015] As can be seen from equation (1), the specific eddy current power loss is exponentially related to the lamination thickness and inversely proportional to the resistivity. To maintain that normal resistivity at a useful level throughout the component.

[0016] The advantage of the electroless method of forming a blocked incomplete insulating layer is that electroless plating can be directly followed by electroplating, or subsequent insulating layers can be formed as needed, allowing the layer to maintain the dense laminate structure of conventional hybrid materials.

[0017] Electroless plating is a technique that connects layers together through an insulating layer, while removing some voids (voids that penetrate the layers). It does not increase the thickness of the layers.

[0018] However, the closed voids increase the strength of the insulating layer by forming high-resistance voids. This can be achieved by forming an electroless plating layer on the hybrid insulating layer. This is because electroplating directly from the insulating layer does not form metal on the insulating layer, whereas electroless plating allows metal to be deposited on the insulating layer. Given the random nature and shape of the voids in the particle hybrid layer, some voids will be closed while others will remain. In a hybrid insulating layer formed by printing, the voids may be printed in a way that at least some of the voids are closed.

[0019] After the electroless process has filled or presumed to fill at least some of the voids, subsequent layers can be completed using electroplating or other forms of plating, if desired. Thus, a combination of high resistance electroless plating and less expensive but lower resistance electroplating to deposit metal on the hybrid insulator can be used to achieve a desirable balance of economy and performance.

[0020] A preferred insulating material with hybrid materials is CCDV SiO2 due to its well-studied nature, non-toxic and relatively inert properties, and low cost. Any oxide or form thereof that is produced can be used to form a more resistive layer in a magnetic material with some degree of success.

[0021] When the hybrid insulating layer is particulate-based, the void closure occurs randomly. FIG. 1 shows a magnetic material layer 101 having a hybrid insulating layer 102 on its upper surface. The magnetic material layer 101 can be a nickel-iron alloy or any metal or magnetic material that can be used for the same purpose as nickel-iron. In the exemplary embodiment shown in FIG. 1, the magnetic layer is nickel-iron, the hybrid insulating layer 102 is SiO2, and the SiO2 is randomly distributed. (This random distribution occurs because the SiO2 falls like snow as a result of the combustion reaction in the CCVD process.) Note that some SiO2 particles become embedded in the metal layer due to the heat of the particles as combustion products. Also, the SiO2 particles that make up the SiO2 layer 102 can fall in any random pattern; this figure shows only one example of a pattern that the SiO2 particles can form.

[0022] Between the SiO2 particles there are several large through voids 111. These through voids 111 have holes that go all the way through the cross section of the hybrid insulating layer 102. There may also be other significant voids 112, but these do not go all the way through the cross section of the SiO2 layer 102 and may or may not be blocked depending on how they are formed.

[0023] FIG. 2 shows an electroless magnetic material layer plated on the hybrid insulating layer 102 and magnetic layer 101 (shown as NiFe) of FIG. 1. Thin layers can be seen formed on the exposed portions of the SiO2 surface and on top of the metal layer. The NiFe layer electrolessly plated on the initial NiFe layer is layer 120, and the NiFe layer electrolessly plated on the SiO2 layer is NiFe layer 121. Because electroless plating is not selective, plating occurs on all exposed surfaces, including the insulating layer. If the voids are not too large, the electroless layer will grow to a sufficient thickness during plating, causing the voids to close. This prevents these voids from receiving deposition. Thus, voids 111 and 112 may be blocked and unable to receive further deposition.

[0024] The voids that are filled by the electroless plating process contain some environmental substances, which can be controlled by controlling the plating or pre-plating environment.

[0025] The voids closed by electroless plating are not necessarily pure air gaps, as they contain some environmental substances, which can be controlled by controlling the environment during or before plating.

[0026] 3 focuses on an exemplary inter-particle void 311 that extends from top to bottom. The top of void 311 is closed by electroless plating before the volume below the void is filled, thus leaving a void in the hybrid insulating layer that is not filled.

[0027] 4 focuses on an exemplary void 411 that narrows from top to bottom, where electroless plating does not close the void 411, and the void 411 will be filled with metal 121 either by electroplating or electroless plating if the void is narrow enough.

[0028] However, not all voids have a uniform width. Figure 5 shows void 511 having a narrower plugged point 520 below the initial opening, and widening from plugged point 520 again to form lower region 521. Plugged point 520 of void 511 is closed with metal 121 by electroless plating, and only the space above the plugged point is plated with metal. When a void has a structure that has a portion narrow enough to be closed by the initial electroless plating and then widens from that portion, an insulating void of the present invention is formed.

[0029] This principle of controlling which voids are closed can be utilized in more controlled manufacturing processes, such as inkjet printing. In the inkjet printing method for forming a hybrid insulating layer, the hybrid insulating layer is formed by printing, and the voids are systematically designed and positioned. As shown in Figure 6, if void 611 is positioned so that opening 620 is narrower than the rest of the void, that portion will be closed by electroless plating if opening 620 is sufficiently narrow.

[0030]

[0013] Figure 7 shows the hybrid insulating layer of Figure 2 once a subsequent metal layer has been built on the insulating layer. The subsequent metal layer may be built by, but is not limited to, electroplating or electroless plating. The steps shown in Figures 1, 2, and 7 may be repeated until the desired component is built.

[0031] The particulate hybrid insulating layer of the present invention is incomplete, consisting of loosely dispersed particles embedded within the metal layer. That is, the hybrid insulating layer of the present invention is not a complete, monolithic insulating layer. Therefore, the hybrid insulating layer of the present invention is highly susceptible to subtractive manufacturing processes, including etching and drilling. In subtractive manufacturing processes, even if the particles are SiO2, they behave like dust. For example, in an etching process, silicon dioxide (SiO2) particles are washed away, and in a drilling process, the silicon dioxide does not provide a resistant barrier to the drill and is removed along with the metal.

[0032] Regarding acid etching, the occluded hybrid insulating layer may be in the form of particles with through-pores, allowing the etching acid to etch through the pores. This property allows any etching acid to be used, and it is useful for etching the metal around the insulator. Therefore, when etching, it is only necessary to use an etching acid suitable for etching the metal layer.

[0033] The non-grain hybrid insulating layer is not easily integrated with subtractive manufacturing methods because it is not grain morphology and is resistant to etching and puncturing.

[0034] Electroless plating therefore offers a simple way to create a base for components formed by subtractive manufacturing methods (including, but not limited to, chemical etching, laser drilling or cutting, or mechanical drilling or cutting). However, the additive manufacturing process is more complex, as a dry film must be removed after each electroless plating step. An exemplary embodiment of this process is shown in FIG.

[0035] Step 1 in FIG. 8 involves preparing a dry film for patterning. In step 2, the dry film is patterned. In step 3, an initial magnetic layer is deposited. In step 4, a CCVD process is performed to form an incomplete insulating layer. In step 5, electroless plating is performed. It will be appreciated that electroless plating forms a metal layer on all particles. Because the particles in step 4 are deposited on the dry film and on the edges of the dry film, it may be beneficial to replace the dry film before starting electroplating.

[0036] If an electroless process is immediately followed by an electroplating process, the electroless layer acts as a seed layer, allowing the electroplated layer to grow horizontally and vertically, preventing subsequent particle layers from forming as an edge-to-edge layer of the component. Therefore, before forming the magnetic layer by electroplating, the dry film is often replaced, as shown in step 6 of Figure 8, which adds a repetitive step. This dry film replacement requires replacing the dry film pattern, which destroys the smooth sidewalls that are characteristic of hybrid materials.

[0037] Therefore, it may be beneficial to fabricate a hybrid material with at least one conventional hybrid insulating layer and at least one electroless insulating layer. By arranging these two types of layers, it is possible to significantly increase the vertical resistivity compared to the bulk material and conventional hybrid material while minimizing edge misalignment. For example, a configuration with one closed hybrid insulating layer for every 100 conventional hybrid insulating layers is possible, or any other layer configuration is also possible. However, it should be noted that the need for a new dry film process does not necessarily mean that another surface treatment step is required for the formation of the next layer, and this process still involves fewer steps than conventional laminate material processes.

[0038] 9 shows an example process overview that can be incorporated into a plating workflow in which NiFe components are plated. The present invention can be applied to a variety of metals and electrical components. Using NiFe, nickel, or other electrolessly plateable elements and alloys, the device of the present invention can be formed according to a variety of plating methods that can integrate a CCVD process.

[0039] Step 1 shows the dry film on the electroless seed layer, and step 2 shows the result of patterning the dry film. Steps 1 and 2 may be replaced with any process that helps define the components to be plated.

[0040] Step 3 shows the electrolytic deposition of a NiFe layer onto the seed layer to form the initial core layer of the component. After this initial core layer is formed, an incomplete SiO2 layer is formed, as shown in step 4, and then a SiO2 layer is formed by CCVD. Following the formation of the incomplete SiO2 layer, step 5 is performed. Step 5 is the electroplating of the NiFe layer, which forms an incomplete silicon dioxide layer without voids. Steps 3 and 4 can be repeated until the desired number of layers is achieved, as shown in step 6. The desired number of layers is generally determined by the skin depth, since eddy current generation increases as the core becomes larger.

[0041] Once step 6 is complete, the entire device is coated with silicon dioxide particles, as shown in step 7. The dry film is then stripped and each layer is electrolessly plated with nickel-iron, as shown in step 8. This creates a very strong silicon dioxide insulating layer 110 with voids. These voids contain some other substance or element associated with the environment, rather than the plating material.

[0042] A second set of core layers can be built on the first set of core layers following steps 1-6 of the process. This second set of core layers will be thinner than the first set of core layers due to dry film tolerances. By targeting placement of the dry film on the first set of core layers, the situation where there is a space between the dry film and the first set of core layers along the edge of the layer set is minimized. This minimizes the possibility of core material without an insulating layer formed on it.

[0043] It will be appreciated that the blocked insulating layer increases the perpendicular resistivity of the hybrid material without requiring a change in the materials used or an increase in the thickness of the insulating layer itself. This allows the blocked hybrid material to maintain the same ease of packaging and use as conventional hybrid materials. The blocked hybrid material also maintains a similar small size as its conventional hybrid counterpart. In fact, the increased resistivity could, in theory, allow a blocked hybrid magnetic core (e.g., a blocked hybrid nickel-iron core) to actually be smaller than a conventional hybrid core for the same frequency application.

[0044] It also makes sense that if resistivity is increased, fewer insulating layers can be provided in the hybrid material. However, at high frequencies, eddy currents are generated at a higher density, and insulating layers need to be placed closer together regardless of their thickness, so reducing the number of layers is not a likely outcome (although in some cases using low frequencies, for example, reducing the number of insulating layers may be more cost-effective and practical). Therefore, instead of reducing the number of insulating layers, a closed hybrid core may be able to accommodate more and thinner insulating layers within the core for further performance improvement at high frequencies.

[0045] In all cases of encapsulated hybrid insulation layers and components, it may be beneficial to shock the component or layer after it has been constructed. In at least one exemplary embodiment, the resulting component is subjected to a shocking process. The shock process may be a thermal shock process.

[0046] The results of this electroless plating method include higher performance hybrid materials that allow the hybrid materials to handle higher frequencies, contain more layers, and even be smaller—all while requiring the use of additional materials and maintaining the positive benefits of hybrid materials (e.g., ease of subtractive fabrication).

[0047] The drawings and figures show multiple embodiments and are intended to illustrate specific embodiments, but are not intended to limit the scope, number, or type of embodiments of the present invention. The present invention may incorporate numerous types and specific embodiments. All figures are prototypes and schematics, and the final product may be further refined by those skilled in the art. Nothing should be construed as essential or required unless expressly stated otherwise. Additionally, the articles "a" and "an" may be understood to mean "one or more," and when only one is intended, the term "one" or other similar expression is used. Additionally, terms such as "has," "have," and "having" are intended to be open-ended terms. The term "metal" is defined as a metal or an alloy thereof.

Claims

1. 1. A method for producing a closed-gap hybrid material for a magnetic component, comprising: Producing a layer of magnetic material; forming an incomplete insulating layer on the layer of magnetic material; forming a layer on a portion of the surface of the imperfect insulating layer by controlled autocatalytic deposition until at least one closed void is created; A method comprising:

2. The method of claim 1 , wherein the imperfect insulating layer is an imperfect grain insulating layer.

3. The method of claim 1 , wherein the fabrication of the magnetic material layer is performed on a substrate core, a carrier, a wafer, or a film.

4. The method of claim 3 , wherein the substrate core is one or more of an epoxy, fiberglass, Ajinomoto® build-up film, silicone, or polymer substrate core.

5. forming an intermediate partial insulating layer on a surface of the metal layer; forming an additional metal layer on a surface of the additional incomplete insulating layer, and forming an additional insulating layer on a surface of the additional metal layer, at least once in the order listed; The method of claim 1 further comprising:

6. The method of claim 1 , wherein the metal layer is nickel, iron, cobalt, or an alloy of any of these materials.

7. The method of claim 6 further comprising patterning the occluded hybrid material into a magnetic core.

8. 10. The method of claim 1, further comprising electroplating a metal layer onto surface portions of the incomplete insulating layer that have not been subjected to controlled autocatalytic deposition.

9. 2. The method of claim 1, wherein the incomplete insulating layer has a coverage of 90 to 99.99% and a thickness of 10 nm to 5 μm.

10. The method of claim 1 , wherein the partial insulating layer is formed by an inkjet printing process.

11. A closed pore type hybrid material, a magnetic material layer; at least one incomplete insulating layer of a closed-gap type having a set of voids embedded in a magnetic material, some of the voids being closed; A hybrid material comprising:

12. The apparatus of claim 11 , further comprising a substrate operatively connected to a bottom surface of the layer of magnetic material.

13. 13. The apparatus of claim 12, further comprising at least one metal layer having an additional closed-void incomplete insulating layer embedded therein and operably connected to a surface of the substrate opposite the closed-void hybrid material.

14. The device of claim 11 further comprising the closed-gap hybrid material integrated into a magnetic core.

15. The device of claim 11 , wherein the metal layer is nickel, iron, cobalt, or an alloy of these materials.

16. The apparatus of claim 11 further comprising the closed-void incomplete insulating layer having at least one void filled with metal.

17. The device of claim 11 , wherein the imperfect insulating layer is an imperfect grain insulating layer.

18. The apparatus of claim 11 , further comprising the hybrid material operably connected to a substrate, a core, a carrier, or a wafer.

19. 12. The device of claim 11, wherein the core is one or more of the group consisting of epoxy, fiberglass, Ajinomoto® build-up film, silicone, polymer, various films, and cores identical or similar to any core used in the printed circuit board, semiconductor package, semiconductor wafer, or lamination industries.

20. The device of claim 11, wherein the magnetic material is a nickel-iron alloy.

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