Multi-turn high density coil and fabrication method

A multi-turn electrical coil and fabrication method uses a plurality of identically constructed flat electrical conductors, alternating ones of which carry an electrically insulating material layer on one major surface. The bare conductors and the insulated conductors are alternatingly stacked about mounting posts in partially overlapped and partially laterally offset pairs of conductors, with each conductor in each conductor pair reoriented relative to the other conductor in the respective conductive pair, and alternating conductor pairs reoriented relative to adjacent conductor pairs, to form a spiral winding turn for the coil.

BACKGROUND

The present multi-turn high density coil and fabrication method relates to coils used in electrical and electronic equipment, such as inductors and transformers and, particularly, to coils in use for electrical and electronic devices formed of stacked layers of interconnected conductors.

Windings forming coils for an inductor or a transformer are used in electrical and electronic equipment. Such equipment usually has volume-restricted space requirements thereby requiring that such coils or windings have a low profile.

In order to achieve the low profile and minimal space requirements for such coils, the fill factor of the windings of the coils needs to be maximized so that the maximum amount of current carrying conductors completely a given space.

Planar magnetics i.e., inductors or transformers, has recently gained interest due to performance, space utilization and fabrication efficiency. For planar magnetics, there are three general methods of building coil windings. The first one is a conventional wire winding process, where edgewise winding can be used to make a planar coil. However, this process has limitations in shape or configuration of the end structure. It is further difficult to have tightly wound coils or wide flat coils, especially with edgewise winding, since the coils are processed from thick copper wire.

A second planar magnetic winding technique is to use PCB or semiconductor fabrication processes. The winding structure is built using a metal deposition or plating and etching processes. This fabrication method has a limitation in conductor fill factor which is important to maximize DC performance, since metal thickness is limited. In addition, inter-layer connection parts have to be prepared using additive metallization such as through hole or side metallization to form a coil with a large number of turns. Such additive processes are usually complicated and show poor conductivity.

The third winding fabrication method uses bus bars for single or several winding structures which are machined out of thick copper plate and built into a coil structure by welding or soldering. The problem of bus bar type construction is that it requires not only machining, but also bending, welding, or soldering.

SUMMARY

A coil for an electrical and/or electronic device includes a spiral wound electrical conductors coil formed by a plurality of vertically stacked conductors, each having a linear shape and arranged in pairs of conductors. Each pair of conductors includes a first bare conductor and a second conductor having an electrically insulating material layer on one major surface. The conductors are inverted relative to each other to form each pair of conductors with a bare exposed portion of the pair of conductors extending outward from each pair of conductors. Partially laterally offsetting and laterally overlapping alternating pairs of conductors, with the bare exposed outwardly extending portions of each pair of conductors contact a stacked bare conductor portion of an adjacent pair of conductors to complete a spiral turn in the coil.

The coil has two sets of non-conductive posts. The conductors mounted over the posts. Connectors are engageable with the posts for forcing the stacked arrangement of conductors into electrical contact to form at least one spiral turn of the coil.

In one aspect, each conductor may have long leg portion and angularly disposed short leg portion extending from an end portion of the long leg portion.

Each conductor may have an L-shape with a long leg portion and a short leg portion, the short leg portion extending perpendicularly from one end of the long leg portion.

Two pairs of stacked, partially overlapping and partially laterally offset pairs of conductors form a single spiral winding turn with a centrally disposed aperture between the stacked pairs of conductors.

Alternating conductors have an electrically insulating material layer on one major surface.

In one aspect, alternating conductors are reoriented relative to adjacent stacked conductors.

In another aspect, the plurality of flat conductors are arranged in stacked pairs of conductors, with each conductor in each pair of conductors inverted in orientation relative to the other conductor in each pair of conductors. Each pair of conductors are inverted in orientation relative to adjacent stacked pairs of conductors.

A method of forming a coil for an electrical/electronic device positioning includes:

providing two sets of posts, each set including three co-linear posts, the two sets of post spaced apart co-linearly in parallel;

providing a plurality of identically shaped flat electrical conductors, including one bare conductor, with alternating second conductors having an electrically insulating layer on one major surface;

mounting a first bare conductor about selected ones of sets of posts;

reorienting a second conductor carrying the electrically insulating surface relative to the first bare conductor and mounting the second conductor over the first conductor on the selected posts of the sets of mounting posts;

mounting a third bare conductor reoriented from the orientation of the first bare conductor in the first pair of conductors over selected posts of the sets of posts partially overlapping and partially laterally offset from the first pair of conductors;

mounting a fourth conductor carrying an electrically insulating material layer on one major surface over the third conductor, reoriented relative to the third conductor; and

urging exposed end portions of the first, second, third and fourth conductors into electrical contact to form a single spiral turn in the coil.

The coil further includes an input terminal coupled to one of the plurality of conductor and an output terminal coupled to another one of the plurality of conductors.

The method also includes the step of forming a transformer by mounting the coil in magnetic relationship with a magnetic core.

DETAILED DESCRIPTION

Referring now toFIGS. 1-11, a coil20is illustrated which is useable in electrical/electronic devices as an inductor or a transformer.

The coil20is formed of a plurality of spiral turns of an electrical conductor, with the number of turns, as well as the size (length, width and thickness) of the electrical conductors being chosen to suit the particular current and voltage requirements of a particular electrical/electronic application.

The coil20is constructed of a spiral-stacked arrangement of a plurality of identical electrical conductors22and24, as shown in detail inFIGS. 2,3, and4. The conductors22and24are substantially identical in shape and size, with the only difference being that the conductor24has an electrical insulating material layer26applied to one major surface.

Although the conductors22and24will be described hereafter as being in the form of plates or bus bars, in one aspect, the conductors22and24are in the form of thin foil like strips formed of an electrically conductive material, such as copper, copper alloy, etc. The thin thickness of the conductors22and24enables selective bare ends of the individual conductors22and24, as described hereafter, to be urged together into electrical contact under the force of connectors.

The conductors22and24may also assume a variety of shapes with the L-shape conductors shown inFIGS. 2 and 3being understood to be an example of a number of possible shapes that the conductors22and24may take. The conductors22and24can be stamped, machined or otherwise formed in the illustrated L-shape.

Thus, in the aspect of the conductors22and24shown inFIGS. 1-8, each conductor22and24has a longer leg30and an integral short leg32which projects from one end of the longer leg at a generally perpendicular angle. An aperture34is formed at one end of the long leg30. A pair of apertures36and38is formed at the opposite end of the conductor22at one end of the longer leg30and the short leg32. The conductor22is bare, that is, both major surfaces, including the top surface40and the bottom surface42, are bare of electrical insulation.

The other conductor24is identically constructed with a longer leg50, and a shorter leg52extending from one end of the longer leg50at a generally perpendicular angle. A first aperture54is formed in one end of the longer leg50. A pair of apertures56and58is foliated at the other end of the conductor24, one aperture56in one end of the longer leg50and one aperture58in the shorter leg52.

As shown inFIG. 4, the conductor24includes an underlying bare conductor portion25, identical in shape, size, and thickness as the other bare conductor22, as well as a layer of electrical insulating material57, which is coated or adhesively joined to one major surface of the conductor24. The side edges of the conductor24do not have to be covered by the electrically insulating material layer applied to one surface of the bare conductor portion25of the conductor24.

The conductors22and24may take other shapes, such as a more rounded, C-shape, with one end being longer than the opposite end of the C-shaped conductor.

In order to create the stacked arrangements of spiral arranged, interleaved conductors22and24, two sets60and62of parallel, spaced, non-electrically conductive supports or posts are provided as shown inFIGS. 5A-7. The first set60of posts includes first, second and third posts64,66and68. The second set62of posts includes posts70,72and74. The posts64,66,68,70,72and74in the two sets60and62of posts are arranged in a spaced apart, generally in an in-line, spaced co-linear manner within each set60and62and aligned with one opposite post in the other set62or60. For example, post64in the first set60of posts is co-linear with post70in the second set62of posts. Similarly, the post66is co-linear with the post72and the post68is co-linear with the post74. The individual posts64,66, and68in the first set60of posts are co-linear with each other. Similarly, the posts70,72, and74in the second set62of posts are co-linear with each other.

The formation of a single spiral turn80of the coil20will now be described in conjunction withFIGS. 5A,6A,6B,6C and6D. In constructing the single spiral turn80of the coil20, a first conductor pair82including the first and second conductors22and24is used along with a second conductor pair84of like third and fourth conductors92and94. The first and second conductor pairs82and84, respectively, are identically constructed, and the first and second conductor pairs82and84are stacked, but with the second conductor pair84reoriented or reversed in orientation relative to the first conductor pair82to form a generally polygonal shaped, single turn spiral winding with a central aperture86, shown inFIGS. 1,6D and7.

As shown inFIGS. 6A-6D, the first step in forming the coil20is to mount the first conductor22of the first conductor pair82over the posts64,66, and70, with the short leg32of the conductor22oriented so that the apertures36and38are respectively mounted over the posts66and64as shown inFIG. 6A.

Next, the second conductor24of the first conductor pair82is mounted over the first conductor24by reversing or reorienting the position of the short leg32of the second conductor24so that the apertures56and58in the shorter leg32of the second conductor82are respectively mounted over the posts70and72, with the aperture54at the end of the longer leg50of the second conductor24mounted over the post64as shown inFIG. 6B. In this orientation, the electrical insulation layer57on the second conductor24faces upward away from the underlying first conductor22.

The inverting, reversing or reorienting the position of the conductors22and24of the first conductor pair82and the first and second conductors92and94of the second conductor pair84means that the second conductor24of the first conductor pair82is maintained in the same planar orientation as the first conductor22, but rotated 180° from the orientation from the first conductor22so that the short leg52of the second conductor24is longitudinally spaced from the short leg32of the first conductor22as shown inFIG. 6B. The same inverting, reversing or reorienting applies to the first and second conductors92and94of the second conductor pair84, as shown inFIGS. 6C and 6D.

It can be seen inFIG. 6Bthat, in this orientation, the longer legs30and50of the first and second conductors22and24overlay each other. The short leg32of the first conductor24extends laterally outward from one end of the stacked first conductor pair82and the short leg32of the second conductor24extends laterally outward from the opposite end of the stacked first conductor pair82.

Next, the second pair of conductors84, including a third conductor92, identical to the first conductor22and a fourth conductor94identical to the second conductor24and carrying an electrically insulating material layer57are individually stacked over the sets60and62of mounting posts as shown inFIG. 6C. It should be noted that, for clarity, the underlying first conductor pair82, which have been previously mounted on the posts64,66,70and72, shown inFIGS. 6A and 6B, is not depicted; but it will be understood to be underlying the second conductor pair84.

The third conductor92, which is bare, is oriented so that the aperture34in the longer leg30is positioned to engage the post68in the first set60of posts, so that the bare portion formed by the short leg32of the third conductor92is spaced from the bare portion formed by the short leg32of the bare first conductor22in the first pair of conductors82. The fourth conductor94is reoriented or reversed in position from the position of the third conductor92so that the apertures56and58in the short leg52are positioned to be mountable over the posts66and68in the first set62of posts. The aperture54at the end of the longer leg50of the fourth conductor94is mounted over the third post72in the second set62of posts.

The term “reversing, inverting or reorienting” the position of the third and fourth conductors92and94is the same as applied to the conductors22and24of the first conductor pair82. In addition, the second conductor pair84is also inverted, reversed or reoriented with respect to the first conductor pair82so that the short leg32of the third conductor92is longitudinally spaced from the short leg of the first conductor22. Similarly, the short leg52of the fourth conductor94is longitudinally spaced from the short leg52of the leg second conductor24.

It should be noted in comparingFIGS. 6A and 6B, that each half of a single spiral turn of the coil20has a bare exposed portion formed by the short leg32of the first or third conductors22or92at one end of the conductor pairs80and82. The bare exposed portions of the short legs32of the conductors22and92are positioned to engage the underlying bare surface of the second or fourth conductors24and94, respectively due to the axial arrangement of the short leg portions of the conductors over the second posts66and72of the two pairs60and62of mounting posts.

FIG. 6Ddepicts the complete single spiral turn80of the coil20where the two conductor pairs82and84are arranged in a stacked conductor pair arrangement, partially overlapping and partially laterally offset from each other on the sets60and62of mounting posts.

As shown inFIG. 5, an input terminal110, such as a thin foil strip or tab, can be formed on or joined to the bare underside of the short leg52of the second conductor24of the first conductor pair82by welding, soldering, electrically conductive adhesive, etc.

The dashed line denoted by reference number102inFIG. 5depicts the current flow path through the single spiral turn80of the coil20. Current applied to the input terminal110flows along the conductive portion of the short leg portion52of the second conductor24underlying the insulated layer57, through the contacting conducting portions of the longer legs30and50of the first and second conductors22and24to the short leg32of the first conductor22.

As the bare exposed portion of the short leg portion32of the first conductor24axially underlies and is overlapped by the conductive portion of the short leg portion52of the third conductor92, when the conductors22,24,92and94have been mounted on the sets60and62of posts as described hereafter and shown inFIGS. 1 and 7, the bare exposed portion32of the first conductor22contacts the conductive portion of the short leg52of the third conductor92thereby forming a current flow path between the first conductor pair82and the second conductor84. The current flow path then proceeds along the third conductor92, through the overlapped and contacting longer leg portions30and50of the third and fourth conductors92and94until it reaches the bare exposed portion of the second leg portion of the third conductor92. An output terminal can be connected to the bare exposed or short leg32of the third conductor92or the short leg32of the third conductor92can be used as a contact point to further stacked spiral turns of the coil20as shown inFIGS. 1 and 7.

As shown inFIG. 7, a plurality of interconnected spiral turns80are provided for the coil20, with three spiral turns80being shown by way of example. Each spiral turn includes an axial stacked arrangement of partially overlapped and partially laterally offset conductor pairs82and84.

InFIG. 7, connectors120, such as nuts, are mounted on threaded end portions of both ends of the posts64,66,68,70,72, and74. When the connectors120are tightened, the exposed portions of the conductor pairs82and84are urged into electrical contact to form electrical contact surfaces between the layers of each spiral turn80and between each of a plurality of spiral turns80.

FIG. 5Bdepicts an alternate aspect of the conductors22,24,92and94. In this aspect, the conductors22and92, which were previously described as being bare or lacking electrical insulation on either major surface, can be provided with a layer27of insulation, identical to the insulator layer57provided on the conductors24and94, on one major surface as shown for conductors22′ and92′. This makes all of the conductors22′,24,92′ and94identical thereby simplifying manufacturing and reducing manufacturing costs, As shown inFIG. 5B, the orientation of the conductors22′,24′,92′, and94in the same manner as that described above for the conductors22and92, places the layer of insulation27on the conductors92′ in contact with the insulation layer57on the adjacent conductor24.

The coil20shown inFIGS. 1-7can be employed in an electrical/electronic device as an inductor. Alternately, as shown inFIGS. 8A and 8B, two coils20and20′ may be employed as part of a transformer140, shown inFIGS. 8A and 8B, which includes a core142. The core142may be formed in any configuration, with an E-core142formed of a stacked arrangement of E-shaped plates144and end linear plates146shown by example. Separate input and output terminals or tabs110and112are attached to select portions of the spiral turns80of the coils20and20′ in two pairs to form the primary and secondary windings of the transformer140. The spiral turns80of the primary winding are insulated from the spiral turns80of the secondary winding in the transformer140.

One coil20can act as a primary winding for the transformer140; while the adjacent coil20′ can act as a secondary winding for the transformer140. The space between the coils20and20′ can be filled with additional electrical insulation material layer141which extends between the facing surfaces of the coils20and20′ and also, between the opposed surfaces of the input and output terminals110and112of the coils20and20′.

It should be noted that the transformer140configuration as shown inFIGS. 8A and 8Bhas the input and output terminals110and112for the primary and secondary windings or coils20and20′, respectively, arranged to extend outward from the coils20and20′ along the same side of the coils20and20′.

FIG. 9depicts an alternate arrangement of the coils20and20′ for the transformer140. In this configuration, one of the coils20and20′, such as the lower most coil20, is rotated 180° from the orientation of the adjacent coil20′. This allows the input and output terminals110and112of each of the coils20and20′ to project outward from opposite sides of the transformer140.

FIGS. 10A and 10Bdepict an alternate coil construction for the transformer140where the input and output terminals110and112project outwardly from opposite sides or ends of the coils20and20′. This can be achieved by removing two conductors22and24which constitute a half turn of the coil winding. This exposes a bare portion of the lower most pair of conductors22and24to allow the input terminal110to be attached to the coil20and extend outward from the opposite side or end of the coil20then the output terminal112.

FIG. 11depicts yet another aspect of the transformer140where both coils20and20′ have one of the input and output terminals, such as the input terminal110for example, extending out of the opposite end of the coils20and20′ then the respective output terminal112. As described previously, this can be achieved by removing a half turn from the bottom coil20and the top of coil20and attaching the input terminal110to the exposed bare portion of conductors in each coil20or20′. An insulation layer may be provided between the adjacent input terminals110to isolate the primary20winding coil from the secondary winding coil20′.

It will be understood that the fabrication method for constructing a single spiral turn of the coil20, as described above and shown inFIGS. 6A-6D, is by way of example. The individual conductors22,24,92and94may also be stacked to form a single spiral winding turn80of the coil20in an opposite orientation where the first conductor22is reoriented from the orientation shown inFIG. 6Aso that the apertures64and66are mounted over the posts72and74of the second set62of posts.FIG. 10Aalso depicts an alternate interleaving or stacking sequence of the conductors22and24. In this alternate stacking method, the first or lower most conductor22is orientated 180° from the position of the lowermost conductor22shown inFIG. 5. The remaining conductors24and22forming the coil20are also reoriented 180° in the same sequence as described above for the coil20.

FIG. 10Aalso depicts an alternate interleaving or stacking sequence of the conductors22and24. In this alternate stacking method, the first or lower most conductor22is oriented 180′ from the position of the lowermost conductor22shown inFIG. 5. The remaining conductors24and22forming the coil20are also reoriented 180′ in the same sequence as described above for the coil20.