Patent Publication Number: US-11657963-B2

Title: Transformer helix winding production

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of and priority to U.S. Provisional Application Ser. No. 63/078,893, filed Sep. 15, 2020, the entire content of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Field 
     Embodiments of the present disclosure generally relate to transformer windings and, in particular, to methods and apparatus for manufacturing flat helix windings. 
     Description of the Related Art 
     Planar transformers make use of ‘flat’ winding structures as opposed to conventional round transformer wires. There are predominantly three different technologies currently used to produce the flat winding structures used in planar transformers: printed circuit board (PCB), foil windings, and helix windings. 
     The PCB winding structure has two main advantages: the PCB that is used to form the transformer windings can be the same PCB that is used to connect the other electronic components that connect to the transformer, and the windings can be made very thin which is good for high frequency operation (typical PCB copper thickness is 35 μm). The main disadvantage, however, with PCB windings is that it is challenging to manufacture multi-layer windings. Exotic PCB manufacturing methods that are capable of supporting ‘blind vias’ and ‘buried vias’ can be used to enable multi-layer windings; however, these exotic PCB processes are expensive and even with blind and buried vias there are still many design compromises in using this technology. 
     Foil winding structures have the advantage that the foil can be very thin, which is beneficial for high frequency operation; however, this winding structure has disadvantages in regard to the design challenge (design compromises and cost) to fabricate multi-layer windings. 
     The helix winding structure uses a ‘rolling mill’ process to create ‘flat wire’ that is helix wound. This structure has the advantage that it can be made with any number of winding turns, with each turn being on an adjacent layer. The main disadvantage with this winding structure is that the rolling mill process is not able to produce thin (and wide) windings. The thinnest flat wire that can be produced is around 200 μm thick and only 4 mm wide resulting in a width-to-thickness ratio (winding aspect ratio) of 20:1. 
     Therefore, there is a need for a method and apparatus for efficiently producing helix windings with very high width-to-thickness aspect ratio. 
     SUMMARY 
     In accordance with at least some embodiments of the present disclosure, there is provided an apparatus for producing helix windings used for a transformer comprising an electrically conductive mandrel comprising an elongated body, a head comprising an eyelet detail, and a winding structure disposed along the elongated body. 
     In accordance with at least some embodiments of the present disclosure, there is provided a system for producing helix windings used for a transformer comprising a power supply, a container holding an electrolyte solution, an anode connected to a positive terminal of the power supply, disposed in the container, and surrounded by the electrolyte solution, and an electrically conductive mandrel comprising an elongated body, a head comprising an eyelet detail connected to a negative terminal of the power supply, and a winding structure disposed along the elongated body. 
     In accordance with at least some embodiments of the present disclosure, there is provided a method for producing helix windings used for a transformer comprising submerging an electrically conductive mandrel into an electrolyte solution, rotating the electrically conductive mandrel in the electrolyte solution while supplying power to the electrically conductive mandrel from a power supply, and removing copper that has been electroplated to a winding structure of the electrically conductive mandrel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a particular description of the disclosure, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
         FIG.  1    is a side view of a mandrel for producing helix windings, in accordance with at least some embodiments of the present disclosure. 
         FIG.  2    is a diagram of a system that uses the mandrel of  FIG.  1    for producing helix windings, in accordance with at least some embodiments of the present disclosure. 
         FIG.  3    is a flowchart of a method that uses the system of  FIG.  2    for producing helix windings, in accordance with at least some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure comprise methods and apparatus for producing single- or multi-turn, multi-layer helix windings that are both very thin (e.g., about 10 μm to about 100 μm) and wide with high winding aspect ratios (e.g., 1,000:1). In various embodiments, an electro-deposition (electro-plating) production process is employed to manufacture the helix windings using a mandrel comprising winding structures suitably sized and shaped to produce the desired windings. This process also benefits from being able to produce high purity copper windings, which is a desirable characteristic for transformer windings. 
       FIG.  1    is a side view of a mandrel  100  for producing helix windings in accordance with at least some embodiments of the present disclosure. The mandrel  100  (e.g., an electrically conductive mandrel) comprises a body  102  (e.g., an elongated body) extending from a head  104  that is positioned on one end of the mandrel  100 . The head  104  has an eyelet detail  106  having one or more suitable shapes, e.g., circular, rectangular, oval, etc. For example, in the illustrated embodiment, the eyelet detail  106  is shown having a circular shape. 
     The body  102  is formed from one or more suitable metals. For example, in at least some embodiments, the body  102  is formed from titanium and is suitably sized and shaped based on a desired shape for the fabricated windings. For example, the body  102  can have a tubular, rectangular, oval, etc. shape that produces the desired winding shape. In the illustrated embodiment, the body  102  has an elongated configuration with a generally tubular shape. Alternatively, the body  102  can have a rectangular shape that may be used to produce rectangular-shaped helix windings. Alternatively, the body  102  can have a noncontinuous shape, e.g., a portion that is generally tubular and a portion that is rectangular. The mandrel  100  can be of any desired length based on the number and size (i.e., number of turns) of the windings to be fabricated. 
     Wrapped around the body  102  in helix shapes are one or more winding structures. For example, in at least some embodiments, two three-turn winding structures  108   1  and  108   2  and a six-turn winding structure  108   3  (collectively referred to as winding structures  108 ) can be wrapped around the body  102 . The winding structures  108  may have any desired number of turns for the windings to be produced. The winding structures  108  may be part of the form factor of the mandrel  100 , or they may be separately fabricated and adhered to the body  102 . 
     In order to create the thin foil windings, the body  102  is placed into a suitable electrolyte solution for electro-deposition of high-purity copper (e.g., at least one of copper sulfate, copper cyanide, copper acetate, or the like) onto the winding structures  108 . Those surfaces of the mandrel  100  that are not to be electroplated are insulated using an epoxy paint or similar insulating material, area shown shaded in  FIG.  1   . As shown in  FIG.  1   , the body  102  and the head  104  are covered in an insulating material, while the eyelet detail  106  along with a top surface  109  and a bottom surface  111  (shown in phantom in  FIG.  1   ) of the winding structures  108  are not. In the illustrated embodiment, the two three-turn winding structures  108   1  and  108   2  each have three top surfaces  109  and three bottom surfaces  111 , and the six-turn winding structure  108   3  has have six top surfaces  109  and six bottom surfaces  111 . 
     Although the mandrel  100  conducts electricity and, therefore, can be electroplated, titanium is a highly incompatible base metal for electroplating copper (in some embodiments, base metals other than titanium that are highly incompatible for electroplating copper may also be used. As such, the electroplated copper is not inseparably adhered to the exposed surfaces (e.g., the top surface  109  and the bottom surface  111 ) of the mandrel  100  and the deposited thin copper foil can be easily peeled from the exposed surfaces of the winding structures  108  to produce the desired windings. Each of the winding structures  108  will produce two identical helix windings—one that is electroplated to the top surface  109  of the winding structures  108  and the other to the bottom surface  111  of the winding structures  108 . 
     In various embodiments, the eyelet detail  106  may be used to suspend the mandrel  100  in an electrolyte solution during an electro-deposition process and also facilitates a connection to the negative terminal of an electroplating power supply. The deposition process may be a batch process where multiple mandrels  100  are simultaneously emerged in the electrolyte solution. For example in some embodiments, a few hundred mandrels (or more) may be processed at the same time. 
       FIG.  2    is a diagram of a system  200  that uses the mandrel  100  of  FIG.  1    for producing helix windings, and  FIG.  3    is a flowchart of a method  300  for producing helix windings, in accordance with at least some embodiments of the present disclosure. 
     For example, at  302 , the method  300  comprises submerging an electrically conductive mandrel (e.g., the mandrel  100 ) into a container  201  holding an electrolyte solution  204 . For example, in at least some embodiments, a transfer device  207  can be configured to submerge the mandrel  100  into the electrolyte solution  204 . In at least some embodiments, the transfer device  207  can be coupled to a top surface of the container  201 , and a cable  209  (or other suitable device) of the transfer device  207  can attach to the eyelet detail  106  of the mandrel  100 . 
     In at least some embodiments, the deposition processing generally includes a mechanism for agitating the electrolyte solution  204  (e.g., at least one copper sulfate, copper cyanide, and/or copper acetate) in which the mandrel  100  (or mandrels) can be submerged, such as a pumping action in the electrolyte solution, a stirring action in the electrolyte solution, rotating the mandrel  100  in the electrolyte solution, dipping the mandrel  100  in the electrolyte solution, and the like. For example, next, at  304 , the method  300  comprises rotating the electrically conductive mandrel in the electrolyte solution while supplying power to the electrically conductive mandrel from a power supply. For example, the mandrel  100  can be rotated using one or more suitable rotation devices (e.g., one or more of a spinner, motor, axle, bearings, gears, wheels, etc.) coupled to the cable  209 . For example, in at least some embodiments, the transfer device  207  can include a motor (not shown) that is connected to the cable  209  which rotates the mandrel  100  once the mandrel  100  has been submerged in the electrolyte solution  204 . While the mandrel  100  is being rotated, a power supply  203  can be configured to provide power to the mandrel  100  to facilitate the electroplating procedure. For example, in at least some embodiments, the eyelet detail  106  of the mandrel  100  can be connected to a negative terminal of the power supply  203  and an anode  205  that is disposed in the container can be connected to the positive terminal of the power supply  203 , thus forming an electrical circuit that can be used for the electro-deposition of high-purity copper onto the top surface  109  and the bottom surface  111  of the winding structures  108 . In at least some embodiments, the power supply  203  can supply about 0.5 volts to about 6 volts. In at least some embodiments, the power supply  203  can be configured to provide power to the mandrel  100  prior to or after the mandrel  100  has been rotated. 
     A thickness of electro-deposited copper  206  can be determined by controlling a length of time the mandrel  100  is electroplated—the longer the electroplating time, the greater a copper thickness. For example, in at least some embodiments, the time the mandrel  100  is electroplated can be calculated to provide a thickness of about 10 μm to about 100 μm. 
     Next, in at least some embodiments, at  306 , the method  300  comprises removing copper that has been electroplated to a winding structure of the electrically conductive mandrel. For example, once a desired thickness of copper has been electro-deposited, the mandrel  100  can be removed from the electrolyte solution and, in at least some embodiments, prior to removing copper that has been electroplated to the winding structure (e.g., electro-deposited copper helix windings), the method  300  comprises removing residual electrolyte from the winding structures  108  of the mandrel  100 . For example, the mandrel  100  may be washed (e.g., in water) or etched to remove any residue electrolyte. Thereafter, the electro-deposited copper helix windings can simply be peeled/scrapped from the winding structures  108  and the mandrel  100  can be reused to fabricate additional windings. For example, in at least some embodiments, the transfer device  207  can be configured to transfer the mandrel  107  to a removal device  211 . In at least some embodiments, the removal device  211  can comprise a sharp blade which can be in the form of a knife or chisel (e.g., disposed on a peeling/scrapping wheel or other suitable device) that is configured to remove the electro-deposited copper helix windings from the top surface  109  and the bottom surface  111  of the winding structures  108 . The removal device  211  can be a component of the system  200  or a stand-alone component configured to operate in conjunction with the system  200 . 
     In accordance with the disclosed herein methods, high purity copper helix windings that are both very thin (e.g., on the order of 10 μm-100 μm) and wide with high winding aspect ratios (e.g., 1,000:1) can be produced in relatively quick and cost-efficient manner. 
     In various embodiments, the fabricated windings may be further processed to provide an insulation layer over the copper, for example using established industry processes. 
     In one or more alternative embodiments, the techniques described herein may be used to produce 3-D copper parts for other applications. For example, the utility of the methods described herein can be based on the ability to make parts with extreme aspect ratios (e.g., very thin while being very wide/long), compound curved surfaces (e.g., non-developable surfaces), complex 2-D surfaces containing overlapping surfaces, and other electroplated parts in a shape that allows the electroplated parts to be peeled of a mandrel described herein. 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof.