Low profile inductive component

Abstract: A low profile inductive component in accordance with the invention comprises a low profile body having spread apart soldering pads for electrically and mechanically attaching the structure to a printed circuit board and defining an aperture between the pads. A magnetic core is disposed in the aperture. A wire is wound around the core having a first and second end connected to the pads. One end of the core is disposed in the aperture of the low profile body and its other end, which is larger than the aperture, is spaced from the body by spacers extending from the body.

Description: FIELD OF THE INVENTION This invention relates generally to electronic components, and more particularly concerns low profile surface mountable inductive components. BACKGROUND The electronics industry is continually called upon to make products smaller and more powerful. Applications such as mobile phones, portable computers, computer accessories, hand-held electronics, etc., create a large demand for smaller electrical components. These applications further drive technology to research new areas and ideas with respect to miniaturizing electronics. Often times, applications specifically require "low profile" components due to constraints in height and width. Unfortunately, the technology is often limited due to the inability to make certain components smaller, faster, or more powerful. Nowhere can this be seen more than in the struggle to manufacture smaller electrical circuits. Originally, components were mounted on a printed circuit board (PCB) by inserting the leads of the component through the PCB and soldering them to solder pads on the opposite side of the PCB, (called through-hole technology). This technique left half of the PCB unpopulated because one side had to be reserved for solder pads and solder. Therefore, in order to fit more components in a particular circuit, the PCBs were made larger, or additional PCBs were required. The solution to this problem came in the form of Surface-Mount Devices (SMD), or Surface-Mount Technology. SMDs allow electrical components to be mounted on one side of a PCB, (i.e., without having the leads inserted through-holes). An SMD device has small solder pads (or leads) connected to its body, which correspond to solder pads or lands placed on the surface of the PCB. Typically the PCB is run through a solder-paste machine (or screen printer), which puts a small amount of solder on the solder pads on the PCB. Next, a glue dot is inserted on the PCB where the component is to rest. Then, the component is placed on the PCB (held by the glue dot), and the PCB is sent through a re-flow oven to heat the solder paste and solder the component leads to the PCB solder pads. The primary advantage to this technique is that both sides of the PCB can now be populated by electronic components. Meaning one PCB today can hold an amount of electrical components equal to two PCBs in the past. As a result of this advancement in technology, the current electronic circuits are mainly limited by the size of components used on the PCB. Meaning, if the electronic components are made smaller, the circuits are smaller as well. Unfortunately, there are some electronic components that can simply not be produced any smaller than they currently are. Usually this is because the desired parameters for the component cannot be achieved when using smaller parts. A good example of this is inductive components. Inductive components are often used in stepper motors, transformers, servos, relays, inductors, antennas, etc. Typical applications requiring such components include radio frequency (RF), switching power supplies, converters, data communications, processor/controller circuits, signal conditioning circuits, biasing oscillators, DC-DC converters, DC-AC converters, chokes, IC inverters, filters, etc. Certain parameters of these components are affected by the size of parts used. For instance, in inductors, wire gauge determines both the DC resistance and the current carrying ability of the component. Several attempts have been made to compensate for components requiring a minimum amount of size in order to use them in smaller circuit applications. For example, U.S. Patent No. 5,760,669, issued June 2, 1998, to Dangler et al., discloses a low profile inductor/transformer component having a wire coil within a core set which is disposed at least partially within a recess in a header. To achieve its low profile status, Dangler uses a header with a plurality of projections extending from the header's side. A core set is disposed within the header and a pre-wound coil is inserted around the core set. At least one end of the pre-wound coil is wrapped around at least one of the header projections, thereby increasing the size of the coil without raising the height of the component. Unfortunately, this structure creates an awkward sized component with exposed conductive wires capable of being damaged. In addition, the need for pre-wound coils, upper and lower core attachments (the core set), and a header having projections is costly and takes up valuable space on the PCB. Such a device does not answer the growing need for smaller components. Another attempt to produce low profile surface mount coil assemblies is disclosed in U.S. Patent No. 5,796,324, issued August 18, 1998, to Ross et al. Ross discloses a coil wound bobbin having posts that are capable of suspending the coil either above or alongside a PCB. The ends of the coil wire are wrapped on the posts to form wire terminations. These posts are the only part of the component that need to be soldered to the PCB. Unfortunately, suspending the coil above or alongside the PCB does not reduce the amount of space required for the circuit as a whole. Suspending the wire above the board simply raises the height of the circuit. Suspending the coil alongside the PCB raises the width requirement for the circuit. Relevant to potentability of the claims below is another coil component disclosed in U.S. Patent No. 5,307,041, issued April 26, 1994, to Kato et al. Kato discloses a coil component having a ring shaped housing (5) connected to a rectangular support (1) having terminals (2b) for connecting the component to a PCB. More specifically a body is disclosed which has separate legs extending from the body and defining an aperture extending through the body between the legs, as well as a core having an end portion disposed in the aperture and an opposite end portion extending from the body between the legs, and a wire wound around the core. The need for an additional base portion, such as rectangular support (1), increases the height of the component, and therefore, will not satisfy the growing need for smaller components. Accordingly, it has been determined that the need exists for an improved low profile inductive component which overcomes the aforementioned limitations and which further provides capabilities, features and functions, not available in current devices. SUMMARY OF THE INVENTION A low profile inductive component in accordance with the invention comprises the features as claimed in claim 1. In an embodiment, the body is constructed such that a lower flange of the core extends beyond the solder pads so that when mounted on a printed circuit board the lower flange extends into an aperture in the PCB. With such a construction, the height of the inductive component above the board will be lower than the height of the prior described embodiment. An advantage to using this component is that the wire wound around the core is not exposed and the inductive component takes on a slim wafer shape, making it ideal for low profile applications. A further advantage is that the component retains a traditional shape and has no awkward protruding members, thereby making it suitable for vacuum placement surface mount applications, for densely populated PCBs, and/or applications requiring components that use a minimal amount of space. BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which: Figure 1 is an exploded view of a low profile inductive component according to the invention; Figure 2 is a profile view, partially in a cross-section, of the component shown in Figure 1 mounted on a printed circuit board; Figure 3a is a profile view, partially in a cross-section, of another embodiment of a low profile inductive component according to the invention mounted on a printed circuit board; and Figure 3b is a profile view of the component shown in Figure 3a mounted on a printed circuit board. DETAILED DESCRIPTION OF THE INVENTION Turning first to Figs. 1 and 2, a low profile inductive component in accordance with the invention for mounting above the printed circuit board (PCB) is shown generally at reference numeral 10. For convenience, the inductive component is described as it would be positioned on the upper surface of a PCB. In Figs. 1 and 2, the low profile inductive component 10 includes a low profile body 12 made of an insulating material, such as a non-conductive plastic or ceramic. The body 12 has a polygonal shape, such as a hexagon, and is defined by a smooth planer top 14 and a bottom 16. The body 12 defines an aperture 15 passing directly through the center of the top 14 and the bottom 16, and having an inner wall 17. A pair of legs 18 extend downward from opposite ends of the body 12. Soldering pads are located at the bottom of the legs 18, which are made of a conductive material, such as metal, for electrically and mechanically attaching the low profile inductive component 10 to a PCB 20. As is depicted in Fig. 1, each soldering pad 19 is L-shaped and covers the bottom of the associated leg 18 and a part of its outer side. This configuration allows for the inductive component 10 to be removed with a standard soldering iron. The bottom 16 of the body also includes a pair of integrated spacers 22 extending downwards from the body 12 adjacent the aperture in a plane perpendicular to the planes containing the legs 18. The inner wall 17 of the aperture 15 includes a pair of opposed recesses 23, which are generally arched-shaped and extend perpendicular to the planes containing the legs 18. The bottom 16 of the body 12 extends down around the perimeter of each recess 23, thereby creating a recess-shaped spacer 24. The recesses 23 aid in the positioning of the inductive component 10 on the PCB. The low profile inductive component 10 further includes a core 25 of magnetic material, such as ferrites, having a cylindrical center section 26 with an upper flange 27 on the upper end of the center section 26 and a larger diameter lower flange 28 on the lower end of the center section 26. The core 25 is disposed in the aperture 15 with the upper flange 27 fitting snugly in the aperture 15 and with upper surface of the lower flange abutting the spacers 22 and 24. The core 25 may be affixed to the spacers 22 and 24 by a suitable glue. The spacers 22 and 24, and the core 25 are sized so that the top of the upper flange 27 is about even with the top surface 14 of the body 12 and the lower surface of the lower flange is in about the same plane as the solder pads 18. In other words, the core 25 fits completely within the body 12. The inductive component 10 also includes an insulated electric wire 32, such as 24 gage copper wire, wound around the center section of the core 14 and having ends 33 connected to the bottom of the soldering pads 19. The ends 33 and 56 are press fit against the soldering pads 19 to ensure that the ends will be soldered to the lands on the PCB 22. The height of the component 10, as indicated in Fig. 2 with the reference numeral 30, when mounted on the PCB is less than about 1.65 mm above the PCB. In Figs. 3a-b, a low profile inductive component for mounting partially in the PCB is shown generally at reference numeral 40. This component is similar to the component shown in Figs. 1 and 2, and the similar parts are identified with the same reference numeral with exponent " ' ". In this embodiment, the legs 18' of the body 12' are made shorter so that the lower flange 28' extends below the plane of the solder pads 19'. As shown in Fig. 3b, the printed circuit board 20 is provided with an aperture 42 that is larger than the diameter of the lower flange 28'. The aperture 42 is positioned between the lands on the PCB so that when the component 40 is mounted on the PCB, the lower flange 28' extends into the aperture. The height of the component when mounted in the PCB is less than the component of Figs.1 and 2. Its height 30' is less than about 1.19 mm. Thus, in accordance with the present invention, a low profile inductive component is provided that fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description.

Claims: An inductive component (10) for mounting on a printed circuit board (20) comprising: a low profile body (12) having spaced apart soldering pads (19) connected thereto for electrically and mechanically attaching said body (12) to lands on a printed circuit board (20), and defining an aperture (15) extending through said body (12) between said soldering pads (19); a core (25) having first and second ends and having at least a portion of the core (25) disposed in said aperture (15); and a wire (32) wound around said core (25) having first and second ends (33) electrically connected to respective soldering pads (19). An inductive component in accordance with claim 1, wherein said core (25) is comprised of a magnetic material. An inductive component in accordance with claim 1, wherein said first and second core ends comprise first and second flanged ends (27, 28), respectively, and said second flanged end (28) extends from said body (12) between said soldering pads (19). An inductive component in accordance with claim 1, wherein said first and second core ends comprise first and second flanged ends (27, 28), respectively, and said second flanged end (28) extends from said body (12) beyond said soldering pads (19). An inductive component in accordance with claim 1, wherein said first and second core ends comprise first and second flanged ends (27, 28), respectively, and said second flanged end (28) extends from said body (12) an amount no greater than the amount said solder pads (19) extend from said body (12). An inductive component in accordance with claim 1, wherein said first and second core ends comprise first and second flanged ends (27, 28), respectively, and said second flanged end (28) extends from said body (12) an amount greater than the amount said solder pads (19) extend from said body (12). An inductive component in accordance with claim 6, wherein said second flanged end (28) extends from said body (12) and into an aperture (42) in the printed circuit board (20) an amount no greater than the thickness of the printed circuit board (20). An inductive component in accordance with claim 1, wherein said first and second core ends comprise first and second flanged ends (27, 28), respectively, and said first flanged end (27) is disposed in said aperture (15) of said body (12) such that said first flanged end (27) and said body (12) create a generally planar top surface. An inductive component in accordance with claim 1, wherein said first and second core ends comprise first and second flanged ends (27, 28), respectively, and said second flanged end (28) extends from said body (12) to about the plane containing said soldering pad (19). An inductive component in accordance with claim 1, wherein said first and second core ends comprise first and second flanged ends (27, 28), respectively, and said first flanged end (27) is smaller in diameter than said second flanged end (28). An inductive component in accordance with claim 10, wherein said firs flanged end (27) is disposed in said aperture (15) above said second flanged end (28). An inductive component in accordance with claim 10, wherein said inductive component (10) is of a height of less than about 1.65 mm. An inductive component in accordance with claim 1, wherein said inductive component (10) is of a height of less than about 1.65 mm. An inductive component in accordance with claim 1, wherein the core (25) has a reduced diameter central section (26) on which the wire is wound and said first and second core ends comprise first and second flanged ends (27, 28), respectively, wherein the first flanged end (27) fits snugly in the aperture (15) and the second flanged end (28), of larger diameter than the first flanged end (27), is spaced from the surface of the body (12) by spacers (22) extending from the lower surface of said body (12). An inductive component in accordance with claim 12, wherein the spacers (22) are of a height to position the second flange (28) about even with the plane of the solder pads (19). An inductive component in accordance with claim 1, wherein said low profile body (12) has spaced apart legs (18) extending from said body about said aperture (15); and said soldering pads (19) are connected to said legs (18). An inductive component in accordance with claim 1, wherein said low profile body (12) has legs (18) extending from said body (12) to which said soldering pads (19) are connected. An inductive component in accordance with claim 17, wherein said low profile body (12) is polygonal in shape and has a height of less than about 1.65 mm. A method of making a low profile inductive component (10) to be placed on a printed circuit board (20), wherein the method comprises: providing a low profile body (12) having spaced apart soldering pads (19) connected thereto and defining an aperture (15) extending through said body (12); providing a core (25); wrapping a wire (32) around said core (25) so as to provide first and second ends (33); inserting at least a portion of said core (25) into said aperture (15); and electrically connecting said wire ends (33) to respective soldering pads (19) on said body (12). A method of making a low profile inductive component (10) in accordance with claim 19, wherein providing a low profile body (12) comprises providing a low profile body (12) having spaced apart legs (18) to which the soldering pads (19) are connected. A method of mounting a low profile inductive component (10) on a printed circuit board (20), comprising the steps of: providing a low profile body (12) having spaced apart soldering pads (19) extending from said body (12) and defining an aperture (15) extending through said body (12) between said soldering pads (19); providing a core (25) having first and second end portions (27, 28) and having at least a portion of the core disposed in said aperture (15); providing a wire (32) wound around said core (25) and having first and second ends (33) connected to respective soldering pads (19); inserting said low profile inductive component (10) on said printed circuit board (20) such that said soldering pads (19) abut lands on the printed circuit board (20); and soldering said low profile inductive component (10) to said lands to electrically and mechanically attach said component (10) to the printed circuit board (20). The method of claim 21, wherein one of said core ends (27, 28) extends from said body (12) between said soldering pads (19) and further comprises the step of inserting the extending core end (27, 28) into an aperture (42) in said printed circuit board (20). The method of claim 22, wherein inserting the extending core end (27, 28) into the aperture (42) comprises extending the core end (27, 28) into the aperture (42) an amount no greater than the thickness of the printed circuit board (20).

Inventors: BOYTOR JAMES G, GIRBACI CATALIN C, GOGNY HELEN O, BOYTOR, JAMES G., GIRBACI, CATALIN C., GOGNY, HELEN O.
Applicants: COILCRAFT INC, COILCRAFT, INC.
Application year: 2000
Main classification: H01F27
IPC codes: H01F27, H05K3, H01F17, H05K1