FIELD OF INVENTION
This application relates to the field of electronic components, and more specifically, inductors and methods for making inductors.
BACKGROUND
Inductors are, generally, passive two-terminal electrical components which resist changes in electric current passing through them. An inductor includes a conductor, such as a wire, wound into a coil. When a current flows through the coil, energy is stored temporarily in a magnetic field in the coil. When the current flowing through an inductor changes, the time-varying magnetic field induces a voltage in the conductor, according to Faraday's law of electromagnetic induction. As a result of operating based on magnetic fields, inductors are capable of producing electric and magnetic fields which may interfere with, disturb and/or decrease the performance of other electronic components. In addition, other electric fields, magnetic fields or electrostatic charges from electrical components on a circuit board can interfere with, disturb and/or decrease the performance of the inductor.
Some known inductors are generally formed having a core body of magnetic material, with a conductor positioned internally, at times with the conductor formed as a wound coil. Examples of known inductors include U.S. Pat. No. 6,198,375 (“Inductor coil structure”) and U.S. Pat. No. 6,204,744 (“High current, low profile inductor”), the entire contents of which are incorporated by reference herein. Attempts to improve designs and improve the economy of building inductors are commonplace. Thus, a need exists for a simple and cost effective way to produce consistent inductors, including those with inductance lower than 1 uH, while improving direct current resistance.
SUMMARY
An inductor and method for making the same is disclosed herein. An inductor may comprise a coil formed from a conductor. The coil may have two leads extending from opposite ends of the coil. A body surrounds the coil and portions of the first lead and the second lead. The leads may be wrapped around the body to create contact points, such as surface mount terminals, on an exterior surface of the inductor.
A method for making the inductor is also provided. A conductor, such as a metal plate or strip or wire, may be formed in the shape of a coil and two leads coming from opposite ends of the coil. The coil may be formed into a specific shape, such as a serpentine or meandering shape, and may preferably be formed having an “S” shape. The conductor may be stamped to form the shape of the coil and two leads. A body of the inductor surrounds the coil, and may be pressed around the coil, leaving the leads sticking out from the body. The leads may then be bent to wrap around the body to form contact points at one external surface of the body.
In one aspect, the present invention provides for a flat inductor coil having a shape with leads formed as a unitary piece by stamping a sheet of metal, such as copper. It is appreciated that other conductive materials as are known in the art, such as other materials used for coils in inductors, may also be used without departing from the teachings of the present invention. Insulation may also be used around or between parts of the coil and/or leads if needed for particular applications. The lead portions are aligned along a generally straight path and may have a certain width. The coil may include portions that extend outside of the width of the leads, preferably curved or positioned away from a center of the coil, with the portions connected by a connection portion that runs at an angle across the center of the coil. The coil and leads may initially lie in a plane during manufacturing, such as when formed from a flat piece of metal. The leads may ultimately be bent around and under an inductor body that surrounds the coil. All parts of the coil preferably may lie in a plane in an embodiment of a finished inductor. An inductor body is pressed around and houses the coil.
The coil extending between and connecting the leads has a shape. In a preferred embodiment, the coil joins the opposite leads (or lead portions), and generally comprises a first curved portion and a second curved portion. The curved portions preferably curve away from and/or around the center of the coil, and thus may be considered “outwardly” curving. Each curved portion of the coil may extend along a part of the circumference of a circular path curving around the center of the central portion. Each curved portion has a first end extending from one of the leads, and a second end opposite the first end. A central portion, or connection portion, extends at an angle between each second end of the first and second curved portions, traversing the center of the central portion. This creates a serpentine coil which may have an “S” shape when viewed from above or below.
Multiple coil layers may be provided. Insulation may be positioned between the multiple coil layers. A coil according to the invention may be formed as a flat, rounded, or oblong shaped piece of metal.
In one aspect of the present invention, the coil and leads of the present invention are preferably formed, such as by stamping, as a flat, complete unitary piece. That is, no interruptions or breaks are formed in the coil from one lead to the opposite lead. The leads and coil are formed at the same time during the manufacturing process by stamping. The coil does not have to be joined, such as by welding, to the leads.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates an isometric view of an inductor in partial transparency according to the invention;
FIG. 2 illustrates an end view of the inductor of FIG. 1 shown from a lead end;
FIG. 3 illustrates an end view of the inductor of FIG. 1 shown from a non-lead end;
FIG. 4A illustrates a view of the inductor of FIG. 1 shown from the top in partial transparency;
FIG. 4B illustrates a side view of inductor of FIG. 1 viewed from the lead edge;
FIG. 4C illustrates a side view of inductor of FIG. 1 viewed from the non-lead edge;
FIG. 5 illustrates schematically a method of making an inductor according to an embodiment of the present invention;
FIG. 6 illustrates a leadframe formed at the stamping step in the method of FIG. 5;
FIG. 7 illustrates a top down perspective leadframe formed at the stamping step in the method of FIG. 5
FIG. 8 illustrates a part formed at the pressing step in the method of FIG. 5;
FIG. 9 illustrates a top down perspective of a part formed at the pressing step in the method of FIG. 5;
FIG. 10 illustrates a part formed at the pressing step in the method of FIG. 5;
FIG. 11A illustrates a top down perspective of a part formed at the pressing step in the method of FIG. 5;
FIG. 11B illustrates a side perspective of a part formed at the pressing step in the method of FIG. 5;
FIG. 12 illustrates a leadframe with embodiments of an inductor coil according to the invention;
FIG. 13 illustrates a top view of the leadframe and inductor coils of FIG. 12;
FIG. 14 illustrates a leadframe with embodiments of an inductor coil according to the invention;
FIG. 15 illustrates a top view of a leadframe with embodiments of an inductor coil according to the invention;
FIG. 16 illustrates another embodiment of a leadframe and coil according to the present invention;
FIG. 17 illustrates a perspective view of an assembled inductor according to an embodiment of the present invention;
FIGS. 18A and B illustrate an assembled inductor according to the present invention;
FIG. 19 illustrates inductor shown with second body in see-through and core and body removed;
FIG. 20 illustrates a top view of a coil from an assembled inductor with other parts of the inductor 3100 removed;
FIG. 21 illustrates a bottom view of a coil from an assembled inductor with other parts of the inductor 3100 removed;
FIGS. 22A-B illustrates a body from an assembled inductor with other parts of the inductor removed;
FIG. 23 illustrates connections of insulated coils via welding and/or soldering.
DETAILED DESCRIPTION
Certain terminology is used in the following description for convenience only and is not limiting. The words “right,” “left,” “top,” and “bottom” designate directions in the drawings to which reference is made. The words “a” and “one,” as used in the claims and in the corresponding portions of the specification, are defined as including one or more of the referenced item unless specifically stated otherwise. This terminology includes the words above specifically mentioned, derivatives thereof, and words of similar import. The phrase “at least one” followed by a list of two or more items, such as “A, B, or C,” means any individual one of A, B or C as well as any combination thereof. It may be noted that some Figures are shown with partial transparency for the purpose of explanation, illustration and demonstration purposes only, and is not intended to indicate that an element itself would be transparent in its final manufactured form.
FIG. 1 shows an example of an inductor 3100 according to an embodiment described herein, including a shaped coil 3150 formed from a conductor, such as a metal plate, sheet or strip. A shaped coil 3150 may be shaped in a unique configuration that provides for increased efficiency and performance in a small volume and that is simple to manufacture. The coil 3150 and leads 3140a and 3140b are preferably initially formed by stamping a conductive sheet, such as a copper sheet, which may be flat and will produce a flat coil, as shown for example in FIG. 6. It is appreciated that the surfaces of the coil 3150 may be somewhat or slightly rounded, bowed or curved based on the process used to form the coil 3150, and the side edges may be rounded or curved. Acceptable metals used for forming the coil and leads may be copper, aluminum, platinum, or other metals for use as inductor coils as are known in the art. As used herein, “flat” means “generally flat,” i.e., within normal manufacturing tolerances. It is appreciated that the flat surfaces of the coil 3150 may be somewhat or slightly rounded, bowed, curved or wavy based on the process used to form the coil 3150, and the side edges may be somewhat or slightly rounded, bowed, curved or wavy, while still being considered to be “flat.”
After stamping, leftover copper strips referred to as carrier strips or frame portions remain, with at least one of the strips having progressive holes at the opposite ends of the leads. The holes may be used for alignment in connection with manufacturing equipment. The stamped copper coil, leads and frame portions may be referred to collectively as a “leadframe.” Examples are shown in FIGS. 6-11. Initially, such as during manufacturing, the shaped coil and leads may lie in the same plane. Each lead 3140a and 3140b will ultimately be bent around the inductor body, with a lead contact portion 3130 bent underneath the bottom of the inductor body. The leads 3140a and 3140b and coil 3150 are preferably formed as a unitary piece, without a weld.
In an embodiment shown in FIGS. 1, 4A, 5 and 6, the coil 3150 comprises a serpentine or meandering coil provided as an “S” shaped coil or “S-coil,” when viewed from the top as oriented in the relevant Figures. The coil 3150 has a central portion 3151 crossing diagonally through the middle of the coil. A first curved portion C1 has a first end 3152 extending from one of the leads 3140b, and a second end 3153 curving around the center of the coil 3150. A second curved portion C2 has a first end 3155 extending from the other of the leads 3140a, and a second end 3154 curving around the center of the coil 3150 in an opposite direction from the first curved portion C1. Each curved portion forms an arc encircling part of the center of the coil 3150. The curved portions may each run along a circumferential path about the center.
The coil 3150 may have a central portion 3151 that may be formed as a flat, straight strip, running from the second end 3153 of the first curved portion C1 and across the center of the coil 3150 to the second end 3154 of the second curved portion C2. This central portion 3151 completes the “S” shape.
This S-coil or “S” shape is illustrative of a preferred embodiment. Other configurations are also contemplated, as will be discussed in part below, including arc, Z-coil or N-coil configurations. A coil configuration that extends along a meandering path between leads, with a portion of the coil crossing the mid-line or central portion of the coil or an inductor body, would be considered to be a “serpentine” coil. For example, and without limitation, an S-coil, Z-coil, N-coil, and other shaped coils having meandering paths traced from one lead to the other lead are considered to be “serpentine” coils. A serpentine coil may be distinguished from a “winding” coil formed from a wire that encircles a central portion of an inductor core, but does not have a portion crossing or traversing the central portion or a central line of an inductor core.
As shown in FIGS. 4A and 7, a serpentine coil 3150 of the invention may have a first path P1 extending toward a first direction from one side of the inductor toward the opposite side, such as extending from a side of the inductor including the lead 3140b toward an opposite side of the inductor including the lead 3140a. In a preferred embodiment, the first path P1 is a curved or arced path curving away from a central portion of the coil.
A second path P2 continues from the first path P1 and extends toward a second direction, crossing a central line LA of the coil. In a preferred embodiment, the second path P2 slopes diagonally across the center and central line LA of the coil from the side where the first path P1 ends back toward the side where the first path P1 began, such as extending from a side of the inductor including the lead 3140a back toward an opposite side of the inductor including the lead 3140b. The second path P2 may be a generally straight path along most of its length.
A third path P3 continues from the second path P2 and extends in a third direction from one side of the inductor toward the opposite side, such as extending from a side of the inductor including the lead 3140b toward an opposite side of the inductor including the lead 3140a. In a preferred embodiment, the third path P3 is a curved or arced path curving away from a central portion of the coil. In a preferred embodiment, the first and third directions are generally the same, while curving in opposite directions, and also both differ from the second direction. The combination of path P1, P2 and P3 is a preferably contiguous serpentine path, uninterrupted and formed from the same conductor.
The first and third path P1 and P3 may trace curved paths, straight paths or combinations of curved and straight paths. For example, as shown in an alternate embodiment in FIG. 16, an “N”-shaped coil may trace a first path P1 that is generally straight from a first side of the inductor to an opposite side, a second path P2 running diagonally across a center line LA back toward the first side, and a third path P3 that is generally straight from a first side of the inductor to an opposite side along most of the lengths of those paths.
In the arrangements of the coil having an “S”, “N” or “Z”-shape, spaces or gaps are provided between the various portions of the coil, such as between the curved portion C1 and the central portion 3151, and between the curved portion C2 and central portion 3151. In the embodiments having an “S”-shape, the spaces or gaps have a generally semi-circular shape, as shown in FIGS. 4A, 7 and 25 and 39. In the “N”-shaped embodiment as shown in FIG. 16, the spaces or gaps have a generally triangular shape. In a “Z”-shaped coil, the spaces or gaps would also have a generally triangular shape.
The shape of the coil 3150 is designed to optimize the path length to fit the space available within the inductor while minimizing resistance and maximizing inductance. The shape may be designed to increase the ratio of the space used compared to the space available in the inductor body. In an embodiment of the invention, coil 3150 is preferably flat and oriented essentially in a plane.
The “S” shape optimizes the inductance and resistance values compared to other non-coil conductor configurations. A 1212 package size (approximately 0.12″×0.12″×0.04″) with the S-coil may produce inductance values in the range of 0.05 uH at 2.2 mΩ. A 4040 package size (approximately 0.4″×0.4″×0.158″) with the S-coil may produce inductance values in the range of 0.15 uH at 0.55 mΩ. The 1616 package size with the S-coil may produce inductance values of 0.075 uH and the 6767 package size with the S-coil may produce inductance values of 0.22 uH.
According to the illustrative embodiment shown in FIGS. 1-4, showing the inductor body in partial transparency so as to view the interior, a finished inductor 3100 according to the invention includes an inductor body shown in partial transparency formed about, pressed over or otherwise housing the coils and at least parts of the leads, including a first body portion 3110 and a second body portion 3120. As illustrated in FIGS. 1-4C, a first body portion 3110 and a second body portion 3120 sandwich, are pressed around or otherwise house the shaped coil 3150 and parts of the leads 3140a and 3140b to form the finished inductor 3100. From the sides as shown in FIG. 2 and FIG. 3, inductor 3100 may be seen with the first body portion 3110 on the bottom and the second body portion 3120 on the top.
In the illustrated embodiment of FIG. 2 and FIG. 3, which are shown as partially transparent, first body portion 3110 and second body portion 3120 are shown as separate or discrete portions used to form the finished inductor 3100, although a single, unitary overall body may be used. In alternative implementations, any number of body portions may be used. The body may be formed of a ferrous material. The body may comprise, for example, iron, metal alloys, or ferrite, combinations of those, or other materials known in the art of inductors and used to form such bodies. First body 3110 and second body portion 3120 may comprise a powdered iron or similar materials, as will be further discussed. Other acceptable materials as are known in the art of inductors may be used to form the body or body portions, such as known magnetic materials. For example, a magnetic molding material may be used for the body, comprised of a powdered iron, a filler, a resin, and a lubricant, such as described in U.S. Pat. No. 6,198,375 (“Inductor coil structure”) and U.S. Pat. No. 6,204,744 (“High current, low profile inductor”). While it is contemplated that first body portion 3110 and second body portion 3120 are formed in similar fashion and of the same materials, first body portion 3110 and second body portion 3120 may be formed using different processes and from distinct materials, as are known in the art.
The first body portion 3110 and second body portion 3120 surround the coil and parts of the leads, and may be pressed or over-molded around the coil 3150, initially leaving exposed parts of the leads 3140a and 3140b until they are folded underneath first body portion 3110 as shown in their final state in the partially transparent examples of FIG. 4A-C. In a finished inductor or “part,” each lead 3140a and 3140b may run along sides of the first body portion 3110 as shown in FIG. 4B. Each lead 3140a and 3140b terminates with a contact portion 3130 bent underneath the first body portion 3110 as visible in FIG. 1.
As seen in FIG. 1, a shelf 3160, step or indentation may be formed by the portion of lead 3140a that bends along an outer side of the inductor body 3110. The shelf 3160 is formed adjacent where the lead meets the coil 3150, which can also be seen in FIG. 3. The shelf 3160 may transition to a diameter less than the other portions of the lead 3140. This shelf 3160 allows for the lead thickness exiting the body to be smaller to improve the ability to form the part. This shelf 3160 allows additional room for the coil inside the body. It is appreciated that this shelf 3160 is not required in all circumstances, and an inductor or coil or leads according to the invention could be formed without such a shelf.
As seen in FIG. 1, the configuration of coil 3150 may include a coil cutout 3170 adjacent an inner side of the coil where the shelf 3160 transitions to the curved portions C1, C2. Coil cutout 3170 allows separation (space) between the lead and coil.
FIG. 2 shows that the body of the inductor may include a first cutout 3180 or groove in the first body portion 3110 to provide access for placing the lead contact portion 3130 under and against the bottom 3111 of the outer surface of the first body portion 3110. FIG. 3 shows that a second cutout 3190 or groove may also be provided in the first body portion 3110 to provide further access for placing the lead contact portion 3130 under and against the bottom 3111 of the outer surface of the first body portion 3110.
FIGS. 4A-C illustrate additional views of inductor 3100. FIG. 4A illustrates a partially transparent view of the inductor 3100, with the coil 3150 visible through the transparency. FIG. 4B illustrates a side view of inductor 3100 viewed from the lead 3140a edge. FIG. 4C illustrates a side view of inductor 3100 viewed from the non-lead edge. As illustrated coil 3150 may be shaped as an “S” or “Z,” depending on orientation. As used herein, the “S” or “Z” shaped may also comprise the mirror-image of such shapes when viewed from the top as shown in the Figures. For example, it is appreciated that the orientation of coil 3150 may be rotated 180 degrees to form the other of an “S” or “Z” configuration.
FIG. 5 depicts a method 3500 for making inductor 3100. At step 3510, the inductor is produced by stamping to produce features that become leads and a coil between the leads in a desired shape. The stamping may be performed on flat sheets of copper to produce features which make up electrical leads, one on one side of the part and one on the other side of the part, and a coil joining the two leads formed in an “S” shape. The stamped S-coil inductor is a simple and cost effective way to produce consistent inductors with inductance lower than 1 uH. The stamped S-coil inductor is a simple and cost effective way to produce consistent inductors with a direct current resistance up to 80% lower than current high current, lower profile production methods in some instances.
As seen in FIG. 6, the sheets of copper may have leftover copper strips with progressive holes for alignment into manufacturing equipment, which are referred to as carrier strips or frame portions. The stamped copper sheets may be referred to as “leadframe.”
Continuing with the method shown in FIG. 5, at step 3520, pressed powder, such as powdered iron, is poured into a die and pressed into a body about the coil with the leads extending therefrom. For example the body may be pressed to form a desired shape with a body similar to an IHLP inductor. The iron core and leadframe may now be referred to as a “part.”
At step 3530, the part is cured in an oven. This curing process binds the core together.
After curing at step 3540, the carrier strip is trimmed away from the leads on the leadframe.
The leads are folded around the body of the inductor to form the lead contact portions at step 3550.
The stamped coil and leads could also be assembled using other known core materials known to the art.
FIGS. 6-7 collectively illustrate a leadframe 3600 formed at the stamping step (step 510) in method 3500. FIG. 6 illustrates an isometric view of leadframe 3600 and FIG. 7 illustrates an overview of leadframe 3600. FIGS. 6-7 illustrate leadframe 3600 including a two coil 3150 structure as part of the leadframe. It is appreciated that any number of coils may be formed in the manufacturing process along a leadframe, and two coils are shown for ease of illustration and understanding only.
Leadframe 3600 includes a first frame portion 3620 and a second frame portion 3630 (also referred to as “carrier strips”) at the ends of the leads, and with the coil positioned centrally between the first frame portion 3620 and a second frame portion 3630. The inductor assembly includes leads 3140, and coil 3150. Adjacent to lead 3140a is a shelf 3160. The coil 3150 includes a coil cutout 3170. First frame portion 3620 includes an alignment hole pattern 3610. This pattern 3610 enables alignment as part of the manufacturing process. For example, during pressing.
FIGS. 8-11 illustrate a part 3800 of an inductor formed at the pressing step (step 3520) in the method discussed in FIG. 5. FIG. 8 illustrates an isometric view of part 3800 formed at the pressing step depicting only the inner core 3115 surrounding the coil. FIG. 9 illustrates an overview of part 3800 shown in FIG. 8. FIG. 10 illustrates an isometric view of part 3800 formed at the pressing step depicting one of the inductors with body 3110, 3120 included and another where the body 3110, 3120 is shown in partially transparent visual allowing the inner core 3115 and coil 3150 to be viewed. FIG. 11A illustrates part 3800 in an overview of part 3800 with the outer body 3125 in partial transparency to show positioning of inner core 3115 and coil 3150. FIG. 11B illustrates provides a partially transparent side view of part 3800 from FIG. 10.
Part 3800 includes leadframe 3600, which includes first frame portion 3620 and second frame portion 3630 on opposite ends of the leads 3140a and 3140b and coil 3150. Adjacent to lead 3140a is a shelf 3160, indentation or step. On coil 3150 is a coil cutout 3170. First frame portion 3620 includes an alignment hole pattern 3610. This pattern 3610 enables alignment within the manufacturing process.
In an embodiment of the invention, part 3800 includes body 3125 pressed over the coil 3150 and a portion of leads 3140, leaving exposed portions of the leads 3140a and 3140b and the first frame portion 3620 and second frame portion 3630. Body 3125 may include first body portion 3110 and second body portion 3120 as described. Body 3125 may be formed from pressing a ferrite material around the coil 3150. Body 3125 may be separate from an inner core 3115 or they may be formed together, such as a unitary part. The inner core can be formed in different ways: the material can be formed separately, typically from ferrite, and then laid on top of the coil and then the body can be pressed around it, or the inner core can be pressed around the coil separately, typically using some type of iron, and then the outer core can be pressed around the inner core using the same or different materials. The inner core could be used as the sole source of permeable material, or as the sole body of the device, without the outer core. When an inner core is used, the body 3125 may encase the inner core 3115. In addition, a body 3125 could be formed as a unitary piece or combination with an inner core 3115. In addition, the body may only be an inner core.
FIGS. 10 and 11A and B show the inductor body 3125, illustrating the body 3125 and inner core 3115, with the body 3125 shown in transparency. The inner core 3115 may or may not be a separate part of the body 3125, and is shown isolated for illustrative purposes in FIGS. 8 and 9. The inner core 3115 is generally cylindrical, and includes a channel shaped to receive the central portion 3151 of the coil 3150. The curved portions C1, C2 of the coil 3150 surround the inner core 3115, as shown ion FIG. 10. When the first body portion 3110 and second body portion 3120 are brought together, they may form or otherwise contain the inner core 3115.
In one embodiment, an inductor may have multiple stacked coils, as shown in the examples of FIGS. 12-14. FIG. 12 illustrates an isometric view of inductor 3100 with two coils. As depicted in FIG. 12 where coils are attached to a leadframe, a second coil 3150b is aligned and adhered to, such as laminated to, a first coil 3150a. In adhering the coils 3150a, 3150b together, solder may be used. This solder in addition to adhering and maintaining alignment provides an electrical connection between the first coil 3150a and the second coil 3150b. The multi-coil structure of FIG. 12 may be formed by aligning and attaching coils held by two leadframes, or by aligning and adhering a second coil that has already been separated by a leadframe and/or leads to a first coil. Once aligned and adhered, the leadframe for the second coil 3150b may be removed for subsequent processing steps exposing a singular lead 3140.
FIG. 13 illustrates a top view of the multi-coil, multi-layered embodiment of FIG. 12. From this view, only the second coil 3150b may be seen. The leadframe associated with the second coil 3150b has been removed exposing the lead 3140a from the first coil 3150a leadframe. If formed by aligning two leadframes, a boundary 3145b or edge may be formed where the leadframe of the second coil 3150b is removed. The coils may also be separated from each other within the body using insulation between each coil layer. This insulation may provide improved performance of the inductor in certain situations. The insulation may comprise Kapton™, Nylon™, or Teflon™, or other insulative materials as are known in the art. The coils may be connected on the ends using a method such as welding and/or soldering.
FIG. 14 illustrates an inductor 3100 with a plurality of coils, showing a three-coil design. As depicted a first coil 3150a is included in the leadframe and a second coil 3150b is aligned and adhered to a top of the first coil 3150a and a third coil 3150c is aligned and adhered to a bottom of the first coil 3150a. In adhering the coils 3150a, 3150b and 3150a, 3150c, a solder 3232 may be used as shown in FIG. 23. This solder in addition to adhering and maintaining alignment provides an electrical connection between the first coil 3150a and the second coil 3150b. Once aligned and adhered the leadframe for the second coil 3150b and the third coil 3150c may each be removed for subsequent processing steps exposing a singular lead 3140.
The leadframe associated with the second coil 3150b has been removed exposing the lead 3140a from the first coil 3150a leadframe. A boundary 3145b is formed from the removal of the leadframe of the second coil 3150b. The leadframe associated with the third coil 3150c has been removed exposing the lead 3140a from the first coil 3150a leadframe. A boundary 3145c is formed from the removal of the leadframe of the third coil 3150c. The first coil 3150a, second coil 3150b and third coil 3150c may or may not be separated by insulation 3231 as shown in FIG. 23.
FIG. 15 illustrates a formation of the coil with a reduced leadframe having only one carrier strip 3621. In FIG. 15, a stamped “S” shaped coil 3150 may have the same elements as described in FIG. 1. The “S” shaped coil 3150 includes a first lead 3140a connected to the carrier strip 3621, and a second lead 3140b extending from an opposite side of the coil 3150.
FIG. 16 illustrates an alternate shape for an inductor coil. In FIG. 16, an “N” shaped coil 3159 (where the “N” is standing up relative to the length of the carrier strip 3561), is provided. The “N” shaped coil 3159 includes a first portion N1 that connects with a second lead 3140b, and a second portion N1 that connects to a first lead 3140a that connects to the carrier strip 3621. The two portions N1 and N2 are connected by a central portion N3 of the coil 3159. The two portions N1 and N2 of FIG. 16 are generally straight compared to the curved portions C1 and C2 of FIG. 1. The outer corners of the portions N1 and N2, where the portions bend of meet the leads 3140a, 3140b, curved away from the central portion N3 of the coil.
FIG. 17 illustrates a depiction of an assembled inductor 3100 according to the present invention. Inductor 3100 includes a first body 3110 and second body 3120. Also shown is lead 3140, including a step adjacent where the lead exits the body.
FIGS. 18A and B illustrate an assembled inductor 3100 according to the present invention.
FIG. 19 illustrates an inductor shown with the second body 3120 in partial transparency, and cut-away from the top. Coil 3150 is shown connecting leads 3140a and 3140b. Coil 3150 includes regions C1, C2 with a cross-member 3151.
FIG. 20-21 illustrate coil 3150 from an assembled inductor 3100 (e.g., with the leads bent) with other parts of the inductor 3100 removed. FIG. 20 depicts an isometric view of coil 3150 from above and FIG. 21 depicts an isometric view of coil 3150 from below. Coil 3150 is shown connecting leads 3140. Coil 3150 includes curved or arced regions or portions C1 and C2 with a cross-member or central portion 3151.
FIGS. 22A and B illustrate, in transparency, embodiments of a first body 3110 (FIG. 22B) and a second body 3120 (FIG. 22A) from an assembled inductor 3100 with other parts of the inductor 3100 removed. First body 3110 and second body 3120 includes an inner core recess 3221 and a channel recess 3222 for receiving or accommodating a separate inner core and a channel for the coil as described above. First body 3110 and second body 3120 could also form the inner core and include a channel for the coil as described above. In one example, the top of first body 3110 meets the bottom of second body 3120 to create the inner core 3221 recess and the channel recess 3222.
An inductor according to any of the embodiments discussed herein may be utilized in electronics applications, such as DC/DC converters, to achieve one or more of the following: low direct current resistance; tight tolerances on inductance and or direct current resistance; inductance below 1 uH; low profiles and high current; efficiency in circuits and/or in situations where similar products cannot meet electric current requirements. In particular, an inductor may be useful in DC/DC converters operating at 1 Mhz and above.
The present invention provides for an inductor provided with a high current serpentine coil, such as an “S” shaped coil, with low direct current resistance. The design simplifies manufacturing by eliminating a welding process. The design reduces direct current resistance by eliminating a high resistance weld between the coil and the leads. This allows for inductors with inductance ratings below 1 uH to be produced consistently. The “S” shape for the coil optimizes inductance and resistance values compared to a similar stamped coil configuration and other non-coil configurations.
The formed serpentine coil inductor, such as a coil in the S-shape described herein, provides a simple and cost-effective way to produce consistent inductors and to produce inductors with direct current resistance up to 80% lower than comparable known inductors such as IHLP inductors.
It will be appreciated that the foregoing is presented by way of illustration only and not by way of any limitation. It is contemplated that various alternatives and modifications may be made to the described embodiments without departing from the spirit and scope of the invention. Having thus described the present invention in detail, it is to be appreciated and will be apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description of the invention, could be made without altering the inventive concepts and principles embodied therein. It is also to be appreciated that numerous embodiments incorporating only part of the preferred embodiment are possible which do not alter, with respect to those parts, the inventive concepts and principles embodied therein. The present embodiment and optional configurations are therefore to be considered in all respects as exemplary and/or illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all alternate embodiments and changes to this embodiment which come within the meaning and range of equivalency of said claims are therefore to be embraced therein.
Patent Application
20200035413
