Inductor devices – Coil or coil turn supports or spacers – Printed circuit-type coil
Reexamination Certificate
1997-06-13
2001-06-26
Mai, Anh (Department: 2832)
Inductor devices
Coil or coil turn supports or spacers
Printed circuit-type coil
C336S192000, C336S232000
Reexamination Certificate
active
06252486
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to low profile magnetic components, and more particularly relates to such components including planar magnetic winding structures, such as inductors and transformers, in which the windings are composed of stacks of interconnected layers of conductor patterns.
The main use for such planar magnetic components is in electronic circuitry destined for use in a volume restricted space, ie, reduced height and/or reduced total volume.
Such structures consist of a stack of layers each containing part of the total winding structure, an insulating layer to prevent electrical contact between turns in adjacent layers, and a contacting structure that permits electrical contact between turns in adjacent layers. The winding structures are optimized with respect to winding losses, and usually are made by etching or stamping, and sometimes by folding. Contacts are usually made by soldering or using plated vias.
For example, the winding patterns may be formed by selectively etching a copper layer having a thickness of about 3 mils, from a PC board having a thickness of about 4 mils. The etched PC boards are then stacked to form the winding structure.
As such components are reduced in size to meet new miniaturized device requirements, the surface-to-volume ratio becomes smaller and the temperature due to heat dissipation quickly rises with the amount of dissipated heat. In present planar winding structures, such heat dissipation is hindered by the presence of voids between the layers and the windings of each layer, as well as by irregular outer surfaces of the structure, which prevents good thermal contact with surrounding structures. In addition, the layer-to-layer contacts become more difficult to achieve.
In DE 44 22 827 A1, to which U.S. Pat. No. 5,652,561 corresponds, the voids between winding layers of a planar magnetic winding structure are filled with glue, but the interconnections are achieved using vias. Such vias constitute a larger proportion of the total winding structure, which can contribute significantly to eddy current losses and other magnetic winding losses.
In U.S. Pat. No. 5,598,135, some of the interconnections between winding layers of a planar winding structure are achieved by brazing over connector portions of the windings which terminate in the outer surface of the stack. Such brazing is enabled by the use of a rigid ceramic composition as the insulating portion of the winding layers. However, vias must still be used to establish interconnections in the interior of the stack. Such a complex structure tends to be difficult and costly to manufacture.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a planar magnetic winding structure for a low profile magnetic component which is compact.
It is another object of the invention to provide such a the winding layers are readily interconnected.
It is another object of the invention to provide such a planar magnetic winding structure which can be readily connected to external circuitry.
It is yet another object of the invention to provide such a planar magnetic winding structure which is readily manufacturable, and does not deform during manufacturing.
It is yet another object of the invention to provide a low profile magnetic component incorporating such a planar winding structure.
According to the invention, there is provided a planar winding body for a low profile magnetic component, the winding body having upper and lower surfaces, an outer sidewall, and an inner sidewall defining an aperture the body comprising a stack of substantially planar layers of an electrically insulating material, each layer bearing a winding pattern formed by a continuous track of electrically conductive material, the input and output termini of the individual tracks revealed in sidewalls of the winding body, an electrically insulating binding material filling the spaces between turns of the tracks, and metal pattern on the side walls of the body, the metal providing interconnection of the input and output termini of the winding patterns as well as contacts for external electrical connections.
Preferably, the metal paterns are plated, most preferably, electroless plated. A typical and preferred winding material is copper, while the insulating material may be a dielectric polymer such as a polyimide, and a typical suitable filler/binder material is a dielectric thermosetting resin such as epoxy.
In order to maintain planarity of the device during manufacture and thereafter, pads of conductive material of the same thickness as the winding pattern are preferably positioned between the winding pattern and the edges of the layers. Such pads provide support during filling of the voids in the stack and thus prevent loss of filler due to deformation during pressing and curing of the stack to densify and rigidify the structure.
In accordance with another aspect of the invention, there is provided a low profile magnetic component comprising a core and the winding body of the invention.
Preferably, the core comprises two or more core components having mutually facing planar surfaces. In one embodiment, the core comprises a first lower core component having a planar portion and two or more spaced-apart upstanding portions having planar upper surfaces, the upstanding portions defining a space to accommodate the winding body, the core also comprising a second upper core component having a planar lower surface.
In an especially preferred embodiment of the invention, two opposite sides of the winding body have indented portions for accommodating the upstanding portions of the core, and for establishing a predetermined distance between the body and the core, thereby to insure a minimum distance between the contacts on the inner face of the winding body and the adjacent core surface, for electrical isolation purposes.
The planar winding structures of the invention are useful in a variety of applications, such as transformers, inductors, motor windings, planar engines, antennas and detectors.
REFERENCES:
patent: 3483499 (1969-12-01), Lugten
patent: 3848210 (1974-11-01), Felkner
patent: 4201965 (1980-05-01), Onyshkevych
patent: 4547961 (1985-10-01), Bokil et al.
patent: 5386206 (1995-01-01), Iwatani et al.
patent: 5521573 (1996-05-01), Inoh et al.
patent: 5598135 (1997-01-01), Maeda et al.
patent: 4422827 A1 (1995-01-01), None
patent: 5-36537 (1993-02-01), None
patent: 6-163266 (1994-06-01), None
Eason Leroy
Mai Anh
Philips Electronics North America Corp.
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