Abstract:
An electrical component is disclosed. The electrical component includes a current conducting coil having inside and outside surface and terminal ends that are configured for connection to an electrical circuit and compressed iron particles that form a body which completely contacts the inside and outside surfaces of the coil for magnetically shielding the coil and leaving the terminal ends exposed for connection to the electrical circuit.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 13/109,576, filed May 17, 2011, which is a continuation of U.S. application Ser. No. 12/535,757 filed Aug. 5, 2009, now U.S. Pat. No. 7,986,207; which is a divisional application of U.S. application Ser. No. 12/013,725 filed Jan. 14, 2008, now U.S. Pat. No. 7,921,546; which is a divisional application of U.S. application Ser. No. 11/782,020 filed Jul. 24, 2007, now U.S. Pat. No. 7,345,562; which is a divisional application of U.S. application Ser. No. 11/609,165 filed Dec. 11, 2006, now U.S. Pat. No. 7,263,761; which is a divisional application of U.S. application Ser. No. 11/409,651 filed Apr. 24, 2006, now U.S. Pat. No. 7,221,249; which is a divisional application of U.S. application Ser. No. 11/038,880 filed Jan. 20, 2005, now U.S. Pat. No. 7,034,645; which is a divisional application of U.S. application Ser. No. 10/244,777, filed Sep. 16, 2002, now U.S. Pat. No. 6,946,944; which is a continuation of U.S. application Ser. No. 09/546,859 filed Apr. 10, 2000, now U.S. Pat. No. 6,449,829; which is a divisional of U.S. application Ser. No. 09/271,748, filed Mar. 18, 1999, now U.S. Pat. No. 6,198,375. U.S. application Ser. No. 10/244,777, filed Sep. 16, 2002, now U.S. Pat. No. 6,946,944, is also a continuation of U.S. application Ser. No. 09/547,155, filed Apr. 11, 2000, now U.S. Pat. No. 6,460,244; which is a divisional of U.S. application Ser. No. 08/963,224, filed Nov. 3, 1997, now U.S. Pat. No. 6,204,744; which is a continuation of U.S. application Ser. No. 08/503,655 filed Jul. 18, 1995, now abandoned. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates to inductor coil structures and methods for making same. 
       BACKGROUND 
       [0003]    The coil structure of the present invention is preferably for use in a high current low profile inductor commonly referred to by the designation IHLP. However, the particular coil structure may be used in other types of inductors. 
         [0004]    Inductor coils have in the prior art been constructed from various shapes of materials formed into various helical shapes. However, there is a need for an improved inductor coil structure which is simple to manufacture and which provides an efficient and reliable inductance coil. 
         [0005]    Most prior art inductive components are comprised of a magnetic core having a C-shape, and E-shape, a toroidal shape, or other shapes and configurations. Conductive wire coils are then wound around the magnetic core components to create the inductor. These types of prior art inductors require numerous separate parts, including the core, the winding, and some sort of structure to hold the parts together. Also, these inductive coils often have a shell surrounding them. As a result there are many air spaces in the inductor which affect its operation and which prevents the maximization of space. 
         [0006]    Therefore, a primary object of the present invention is the provision of an improved inductor coil structure and method for making same. 
         [0007]    A further object of the present invention is the provision of an inductor coil structure which can be used in a high current low profile inductor having no air spaces in the inductor, and which includes a magnetic material completely surrounding the coil. 
         [0008]    A further object of the present invention is the provision of an inductor coil structure which includes a closed magnetic system which has self-shielding capability. 
         [0009]    A further object of the present invention is the provision of an inductor coil structure which maximizes the utilization of space needed for a given inductance performance so that the inductor can be of a minimum size. 
         [0010]    A further object of the present invention is the provision of an improved inductor coil structure which is smaller, less expensive to manufacture, and is capable of accepting more current without saturation than previous inductor coil structures. 
         [0011]    A further object of the present invention is the provision of an inductor coil structure which lowers the series resistance of the inductor. 
         [0012]    A further object of the present invention is the provision of a high current, low profile inductor which requires fewer turns of wire in the coil to achieve the same inductance achieved with larger prior art inductors, thus lowering the series resistance of the inductor. 
       SUMMARY 
       [0013]    An electrical component is disclosed. The electrical component includes a current conducting coil having inside and outside surface and terminal ends that are configured for connection to an electrical circuit. According to an embodiment, the electrical component may include compressed iron particles that form a body which completely contacts the inside and outside surfaces of the coil for magnetically shielding the coil and leaving the terminal ends exposed for connection to the electrical circuit. According to an embodiment, the electrical component may include compressed iron particles that form a body which completely contacts the inside and outside surfaces of the coil that magnetically shields the coil and leaves the terminal ends exposed outside the body. According to an embodiment, the electrical component may include compressed iron particles that form a body which completely contacts the inside and outside surfaces of the coil, whereby the terminal ends are exposed outside of the body and the coil is magnetically shielded. According to an embodiment, the electrical component may include compressed iron particles that form a body which completely contacts the inside and outside surfaces of the coil and enhances induction and efficiency of the coil. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0014]      FIG. 1  is a perspective view of the inductor constructed in accordance with the present invention and mounted upon a circuit board. 
           [0015]      FIG. 2  is a pictorial view of the coil of the inductor before the molding process. 
           [0016]      FIG. 3  is a pictorial view of the inductor of the present invention after the molding process is complete, but before the leads have been formed. 
           [0017]      FIG. 4  is an end elevational view taken along line  4 - 4  of  FIG. 2 . 
           [0018]      FIG. 5  is an elevational view taken along lines  5 - 5  of  FIG. 4 . 
           [0019]      FIG. 6  is a perspective view of an elongated conductor blank from which the inductor coil is formed. 
           [0020]      FIG. 7  shows the blank of  FIG. 6  after the formation of slots extending inwardly from the opposite edges thereof. 
           [0021]      FIG. 8  is a view similar to  FIG. 7 , showing the first folding step in the formation of the inductor coil of the present invention. 
           [0022]      FIG. 9  is a side elevational view showing the same folding step shown in  FIG. 8 . 
           [0023]      FIG. 10  is a view similar to  8  and showing a second folding step in the process for making the inductor coil of the present invention. 
           [0024]      FIG. 11  is an inverted pictorial view of the inductor after it has been pressed, but before the leads have been formed. 
           [0025]      FIG. 12  is a view similar to  FIG. 11  showing the inductor after partial forming of the leads. 
           [0026]      FIG. 13  is a view similar to  FIGS. 11 and 12  showing the final forming of the leads. 
           [0027]      FIG. 14  is a pictorial view of an inductor constructed in accordance with the present invention and mounted upon a circuit board. 
           [0028]      FIG. 15  is a pictorial view of the coil of the inductor and the lead frame which is attached to the coil before the molding process. 
           [0029]      FIG. 16  is a pictorial view of the inductor of the present invention after the molding process is complete, but before the lead frame is severed from the leads. 
           [0030]      FIG. 17  is a flow diagram showing the method for constructing the inductor of the present invention. 
           [0031]      FIG. 18A  is a sectional view of the lead frame and coil mounted in a press. 
           [0032]      FIG. 18B  is a top plan view of  FIG. 18A . 
           [0033]      FIG. 18C  is a view similar to  FIG. 18A , but showing the powder surrounding the lead frame and coil before pressure is applied. 
           [0034]      FIG. 18D  is a view similar to  18 A, but showing the pressure being applied to the coil, lead frame, and powder. 
           [0035]      FIG. 18E  is a view similar to  18 A, but showing the ejection of the lead frame and the molded inductor from the mold. 
           [0036]      FIG. 19  is a perspective view of a modified form of the invention utilizing a coil of wire having a round cross section. 
           [0037]      FIG. 20  is an exploded perspective view of the lead frame and coil of the device of  FIG. 19  before assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]    Referring to the drawings the numeral  10  generally designates an inductor of the present invention which may be mounted upon a circuit board  12 . Inductor  10  includes an inductor body  14  having a first lead  16  and a second lead  18  extending therefrom and being folded over the opposite ends of body  14 . Leads  16 ,  18  are soldered or otherwise electrically connected on the circuit board  12 . 
         [0039]    Referring to  FIG. 2 , the inductor coil of the present invention is generally designated by the numeral  20 . Leads  16 ,  18  form the ends of coil  22 . Between leads  16 ,  18  are a plurality of L-shaped coil segments  26  each comprising a horizontal leg  28  and a vertical leg  30 . Vertical leg  30  terminates at a connecting segment  32  which is folded over at approximately 180° so as to create an accordion like configuration for inductor coil  20 . The L-shaped coil segments are connected together to form a helical coil having an open coil center  34  extending along a longitudinal coil axis  36 . 
         [0040]      FIGS. 6-10  show the process for making the coil  20 . Initially as shown in  FIG. 6  a blank flat conductor plate  50  formed of copper or other electrically conductive material includes: first and second ends  52 ,  54 ; a pair of opposite flat surfaces  56 ; and a pair of opposite side edges  58 ,  60 . 
         [0041]      FIG. 7  shows the first step in forming the coil  20 . In this step a plurality of slots  62 ,  64  are cut in the opposite edges  58 ,  60  respectively of the blank flat plate  50 . Various cutting methods may be used such as stamping or actual cutting by laser or other cutting tools known in the art. 
         [0042]    Upon completion of the cutting operation, the blank  50  is transformed into an elongated sine shaped body formed from a plurality of cross segments  66  extending transversely to the longitudinal axis of plate  50  and a plurality of connecting segments  67  extending axially with respect to the longitudinal axis of plate  50 . The segments  66 ,  67  form a continuous sine shaped configuration as shown in  FIG. 7 . 
         [0043]      FIG. 8  shows the next step in forming the coil  20 . The end  52  is folded over at an angle of 180° to form the 180° angle bend  63  in the first connecting. segment  67 .  FIG. 10  shows a second bend  65  which is in the next connecting segment  67 . Bends  63 ,  65  are in opposite directions, and are repeated until an accordion like structure is provided similar to that shown in  FIG. 5 . 
         [0044]    In  FIG. 5  the coil  20  includes opposite ends  16 ,  18  which are formed from the opposite ends  52 ,  54  of blank  50 . The cross segments  66  of blank  50  form the first horizontal legs  28  of coil  20 , and the connecting segments  67  of blank  50  form the second vertical legs  30  and the connecting segments  32  of coil  20 . 
         [0045]    An example of a preferred material for coil  20  is a copper flat plate made from OFHC copper  102 , 99.95% pure. 
         [0046]    The magnetic molding material of body  14  is comprised of a powdered iron, a filler, a resin, and a lubricant. The. preferred powdered material is manufactured by BASF Corporation, 100 Cherryhill Road, Parsippany, N.J. under the trade designation Carbonyl Iron, Grade SQ. This SQ material is insulated with 0.875% mass fraction with 75% H 3 PO 4 . 
         [0047]    An epoxy resin is also added to the mixture, and the preferred resin for this purpose is manufactured by Morton International, Post Office Box 15240, Reading, Pa. under the trade designation Corvel Black, Number 10-7086. 
         [0048]    In addition a lubricant is added to the mixture. The lubricant is a zinc stearate manufactured by Witco Corporation, Box 45296, Houston Tex. under the product designation Lubrazinc W. 
         [0049]    Various combinations of the above ingredients may be mixed together, but the preferred mixture is as follows: 
         [0050]    1,000 grams of the powdered iron. 
         [0051]    3.3% by weight of the resin. 
         [0052]    0.3% by weight of the lubricant. 
         [0053]    The above materials (other than the lubricant) are mixed together and then acetone is added to wet the material to a mud-like consistency. The material is then permitted to dry and is screened to a particle size of −50 mesh. The lubricant is then added to complete the material  82 . The material  82  is then ready for pressure molding. 
         [0054]    The next step in the process involves compressing the material completely around the coil  20  so that it has a density produced by exposure to pressure of from  15  to  25  tons per square inch. This causes the powdered material  82  to be compressed and molded tightly completely around the coil so as to form the inductor body  14  shown in  FIG. 1  and in  FIGS. 11-13 . 
         [0055]    At this stage of the production the molded assembly is in the form which is shown in  FIG. 11 . After baking, the leads  16 ,  18  are formed or bent as shown in  FIGS. 12 and 13 . The molded assemblies are then baked at 325° F. for one hour and forty-five minutes to set the resin. 
         [0056]    When compared to other inductive components the IHLP inductor of the present invention has several unique attributes. The conductive coil, lead frame, magnetic core material, and protective enclosure are molded as a single integral low profile unitized body that has termination leads suitable for surface mounting. The construction allows for maximum utilization of available space for magnetic performance and is magnetically self-shielding. 
         [0057]    The unique configuration of the coil  20  reduces its cost of manufacture. Coil  20  may be used in various inductor configurations other than IHLP inductors. 
         [0058]    According to a second embodiment, inductor  10  is configured as shown in  FIG. 14  to be mounted on a circuit board  12 . IHLP  10  includes an inductor body  14  having a first lead  16  and a second lead  18  extending outwardly therefrom. The leads  16  and  18  are bent and folded under the bottom of the inductor body  14  and are shown soldered to a first pad and a second pad  21 ,  22  respectively. 
         [0059]    Referring to  FIG. 15  the inductor  10  is constructed by forming a wire coil  24  from a flat wire having a rectangular cross section. An example of a referred wire for coil  24  is an enameled copper flat wire manufactured by H. P. Reid Company, Inc., 1 Commerce Boulevard, P.O. Box 352 440, Palm Coast, Fla. 32135, the wire is made from OFHC Copper  102 , 99.95% pure. A polymide enamel, class 220, coats the wire for insulation. An adhesive, epoxy coat bound “E” is coated over the insulation. The wire is formed into a helical coil, and the epoxy adhesive is actuated by dropping acetone on the coil. Activation of the epoxy can also be done by heating the coil. Activation of the adhesive causes the coil to remain in its helical configuration without loosening or unwinding. 
         [0060]    Coil  24  includes a plurality of turns  31  and also includes an inner end  27  and an outer end  29 . 
         [0061]    A lead frame  33  formed of phosphor bronze, 510 alloy, which is one half hardened, includes first lead  16  which has one end  35  welded to the inner end  27  of coil  24 . Lead frame  33  also includes a second lead  18  which has one end  38  welded to the outer end  29  of coil  24 . Leads  16  and  18  include free ends  37 ,  40  which are shown to be attached to the lead frame  33  in  FIG. 15 . The welding of ends  35 ,  38  to the inner end  27  and the outer end  29  of coil  24  is preferably accomplished by a resistance welding, but other forms of soldering or welding may be used. 
         [0062]    Referring to  FIGS. 18A and 18B , a pressure molding machine  68  includes a platten  71  having a T-shaped lead frame holder  70  in communication with a rectangular die  72 . Platten  71  is slidably mounted for vertical sliding movement on slide posts  74  and is spring mounted on those posts  74  by means of springs  76 . A base  78  includes a stationary punch  80  which projects upwardly into the rectangular die  72  as shown in  FIG. 18A . 
         [0063]    The lead frame and coil assembly shown in  FIG. 15  is placed in the T-shaped lead frame holder  70  as shown in  FIGS. 18A and 18B . In this position the coil is spaced slightly above the upper end of stationary punch  80 . 
         [0064]    Referring to  FIG. 18C  a powdered molding material  82  is poured into the die  72  in such a manner as to completely surround the coil  24 . The leads  16 ,  18  extend outwardly from the powdered material  82  where they are connected to the lead frame  33 . 
         [0065]    The magnetic molding material is comprised of a first powdered iron, a second powdered iron, a filler, a resin, and a lubricant. The first and second powdered irons have differing electrical characteristics that allow the device to have a high inductance yet low core losses so as to maximize its efficiency. Examples of preferred powdered irons to use in this mixture are as follows: a powdered iron manufactured by Hoeganaes Company, River Road and Taylors Lane, Riverton, N.J., under the trade designation Ancorsteel 1000C. This 1000 C material is insulated with 0.48% mass fraction with 75% H 3 PO 4 . The second powdered material is manufactured by BASF Corporation, 100 Cherryhill Road, Parsippany, N.J. under the trade designation Carbonyl Iron, Grade SQ. This SQ material is insulated with 0.875% mass fraction with 75% H 3 PO 4 . 
         [0066]    The powdered magnetic material also includes a filler, and the preferred filler is manufactured by Cyprus Industrial Minerals Company, Box 3299, Ingelwood, Calif. 80155 under the trade designation Snowflake PE. This is a calcium carbonate powder. 
         [0067]    A polyester resin is also added to the mixture, and the preferred resin for this purpose is manufactured by Morton International, Post Office Box 15240, Reading, Pa. under the trade designation Corvel Flat Black, Number 21-7001. 
         [0068]    In addition a lubricant is added to the mixture. The lubricant is a zinc stearate manufactured by Witco Corporation, Box 45296, Huston, Tex. under the product designation Lubrazinc W. 
         [0069]    Various combinations of the above ingredients may be mixed together, but the preferred mixture is as follows: 1,000 grams of the first powdered iron. 1,000 grams of the second powdered iron. 36 grams of the filler. 74 grams of the resin. 0.3% by weight of the lubricant. 
         [0070]    The above materials (other than the lubricant) are mixed together and then acetone is added to wet the material to a mud-like consistency. The material is then permitted to dry and is screened to a particle size of −50 mesh. The lubricant is then added to complete the material  82 . The material  82  is then added to the die  72  as shown in  FIG. 18C . 
         [0071]    The next step in the process involves the forcing of a movable ram  87  downwardly onto the removable punch  84  so as to force the punch  84  into the die  72 . The force exerted by the removable punch  84  should be approximately 15 tons per square inch to 20 tons per square inch. This causes the powdered material  82  to be compressed and molded tightly completely around the coil so as to form the inductor body  14  shown in  FIG. 14  and in  FIG. 18E . 
         [0072]    Referring to  FIG. 18E  an ejection ram  86  is lowered on to platten  71  so as to force platten  71  downwardly against the bias of springs  76 . This causes the stationary ram  80  to eject the molded assembly from the die  72 . At this stage of the production the molded assembly is in the form which is shown in  FIG. 16 . The molded assemblies are then baked at 325° F. for one hour and forty-five minutes to set the polyester resin. 
         [0073]    The next step in the manufacturing process is to severe the lead frame  33  from the leads  16 ,  18  along the cut lines  42 ,  44 . The leads  16 ,  18  are then bent downwardly and inwardly so as to be folded against the bottom surface of the inductor body  14 . 
         [0074]    The various steps for forming the inductor are shown in block diagram in  FIG. 17 . Initially one of the wire ends  27 ,  29  is welded to its corresponding end  35 ,  37  of leads  16 ,  18  as represented by block  145 . Next the coil is wound into a helix as shown by block  146 . Block  150  represents the step of welding the other end  27 ,  29  to its corresponding lead  16 ,  18 . The coil wire includes an epoxy coat of bonding material described above. A bonding step  149  is achieved by applying the acetone  148  or heat to cause the bonding material to bind or adhere the various turns  31  of coil  24  together. 
         [0075]    Next, at step  152  the powdered magnetic material is mixed together adding ingredients  154 ,  156 ,  158 ,  160 , and  162 . 
         [0076]    The pressure molding step  64  involves the application of pressure as shown in  FIGS. 18A through 18E . The parts are then heated to cure the resin as shown in box  165 . 
         [0077]    Finally after the curing is complete the bending and cutting step involves cutting off the lead frame  25  and folding the leads  16 ,  18  against the bottom surface of the inductor body  14 . 
         [0078]    Then compared to other inductive components the IHLP inductor of the present invention has several unique attributes. The conductive winding, lead frame, magnetic core material, and protective enclosure are molded as a single integral low profile unitized body that has termination leads suitable for surface mounting. The construction allows for maximum utilization of available space for magnetic performance and is magnetically self shielding. 
         [0079]    The unitary construction eliminates the need for two core halves as was the case with prior art E cores or other core shapes, and also eliminates the associated assembly labor. 
         [0080]    The unique conductor winding of the present invention allows for high current operation and also optimizes magnetic parameters within the inductor&#39;s footprint. 
         [0081]    The manufacturing processes of the embodiments provide a low cost, high performance package without the dependence on expensive, tight tolerance core materials and special winding techniques. 
         [0082]    The magnetic core material has high resistivity (exceeding 3 mega ohms) that enables the inductor as it is manufactured to perform without a conductive path between the surface mount leads. The magnetic material also allows efficient operation up to 1 MHz. The inductor package performance yields a low DC resistance to inductance ratio of two milliohms per microHenry. A ratio of 5 or below is considered very good. 
         [0083]    Referring to  FIGS. 19 and 20  a modified form of the invention is designated by the numeral  88 . Inductor  88  is formed from a coil  90  of wire having round cross section. The coil  90  includes a first coil end  92  and a second coil end  94 . A lead frame  96  includes a first lead  98  and a second lead  100  having first and second lead ends  102 ,  104 . 
         [0084]    The method of assembly of device  90  is different from the device  10  shown in  FIGS. 14-18 . With device  90 , the coil is wound first and is heat bonded during winding. Then the coil ends  92 ,  94  are welded to the lead ends  102 ,  104  respectively. The mixed powdered material is then applied and the pressure molding process is accomplished in the same fashion as described before. Finally the leads  98 ,  100  are cut off and bent downwardly under the bottom of the device  10 . 
         [0085]    The position of the leads  98 ,  100  can be varied without detracting from the invention. Also, it is possible to put more than one coil within a molded part. For example, it would be possible to put two or more coils  24  within the molded body  10  or two or more coils  90  within the molded body  89 . 
         [0086]    In the drawings and specification there has been set forth a preferred embodiment of the invention, and although specific terms are employed these are used in a generic and descriptive sense only and not for purposes of limitation. Changes in the form and the proportion of parts as well as in the substitution of equivalents are contemplated as circumstances may suggest or render expedient without departing from the spirit or scope of the invention as further defined in the following claims.