FR2485247A1 - ADJUSTABLE INDUCTOR AND METHOD FOR MAKING SAME - Google Patents

Abstract

THE INVENTION CONCERNS AN ADJUSTABLE INDUCER AND ITS EMBODIMENT PROCESS. THE INDUCER INCLUDES A NON-ELECTRICAL CONDUCTIVE SUBSTRATE 10, AN ELECTRICAL INDUCER 12 PLACED ON A SURFACE OF THE SUBSTRATE, AND A LAYER 14 OF ELECTRICALLY CONDUCTING OR MAGNETIC MATERIAL ON THE SURFACE OF THE SUBSTRATE OPPOSING THE INDUCER AND OF WHICH THE REDUCTION IN THICKNESS OR AREA HAS THE EFFECT OF INCREASING OR REDUCING INDUCTANCE RESPECTIVELY. APPLICATION TO ADJUSTABLE INDUCERS FOR INTEGRATED CIRCUITS.

Description

1; 2485247-

  The present invention relates to electrical inductors and, more particularly, to adjustable inductors

thick and thin films.

  When inductors are used in tuned circuits, filters, etc., it is essential that

  the inductance can be adjusted to a desired value and

  held at this value. It is desirable to use cir-

  cooked in many applications to achieve

  miniature electronic equipment. A difficulty that

  lift such circuits is that the miniature components

  available are not adjustable, and it is difficult to

  cile to use them to adjust or align the circuit

because of their small size.

  To the knowledge of the Applicant, no attempt has been made to adjust the inductance of a thin or thick film inductor of the type described, for example in the patent

  of United States of America No. 3,785,046 without modifying

  the inductor itself or the circuit in which the inductor

  is used. It is difficult and impractical to establish an electrical connection at a point in the winding of

  the inductor other than the starting and ending terminals

  aunts. It is obvious that if one were to attempt to establish a connection at another location in the winding, it would be necessary to traverse the dielectric layers, thereby breaking the hermetic seal and exposing the winding to

  harmful elements of the surrounding environment.

  In addition, in this case, the adjustment range is

  limited by the length of the last turn of the inductive

  because only the last turn is accessible,

  without taking into account the rupture of the hermetic seal.

  However, in a spiral inductor, all turns of the inductor are accessible assuming that the latter is not sealed before adjustment. The socket can be moved until the desired inductance is achieved, and then the plug connection is made permanent by welding or gluing. However, in practice, this is a delicate and precise procedure, especially when the inductance is low. The position and length of the wire

  metal to the socket must be maintained d-siz i: .-

  as long as the adjustment is carried out until the firnal fixation

  and definitive. The modification of the pnhsi-

  such inducers is meticulous and 13n.

  which must be added to the duration and the manufacturing costs.

  According to its fundamental concept, the present

  The invention relates to the adjustment of thin and thick film inductors placed on a surface of a substrate by applying a layer of a highly conductive metal or a high resistivity magnetic material to the opposite surface of the substrate.

  The present invention therefore proposes to overcome

  the above-mentioned limitations and limitations of the

  previous setting dice thin and thick film inductors. The subject of the invention is also an inductor having a very stable regulated inductance, but which can

  be increased or reduced as needed by simply choosing

  the amount and type of coating applied to

  the surface of the substrate which is opposed to the inductor.

  The invention also relates to a method for adjusting the inductors of the type described, in which the sealing or the passivation of the inductor is not affected by the adjustment process. An adjustable inductor of the type

  described is of simplified construction allowing a manufacturer

  economic cation. The invention will be described in more detail with reference to the accompanying drawing by way of non-limiting examples and in which: FIG. 1 is a plan view of an adjustable inductor according to the present invention; FIG. 2 is a front view of the inductor

  and the substrate shown in Figure 1 showing the coating

  metal on the surface of said substrate which is opposed to the inductor;

  FIG. 3 is a plan view of a second

  embodiment of an adjustable inductor according to the invention.

  tion; and FIG. 4 is a front view of the inductor

  and the substrate of FIG. 3 showing the magnetic coating

  applied to the surface of the substrate that is opposed to the

  ducer. A non-electrically conductive substrate 10 is shown in the drawing and may be any suitable insulative material such as alumina (A1203). A surface of the substrate 10 provides a basis for a thin or thick film inductor 12. It is understood that it is possible to use any thin or thick film inductor placed on a non-conductive substrate of electricity, including spiral inductors made by a deposition process either

  in a thin layer, or in a thick layer. The winding of

  The duction shown is described in the US patent

No. 3,785,046, cited above.

  As can be seen in FIG. 2, the surface of the substrate 10 which is opposite the inductor 12 is coated with a layer 14 of metal such as aluminum, copper,

  gold or other metal highly conducive to electricity.

  When an alternating current flows in the inductor 12, the variable magnetic field induces eddy currents in the metal layer 14 in a direction such that the magnetic field produced by the eddy currents is opposed to the magnetic field generated by the current in

  the inductor. As a result, the application of the metallic layer

  that decreases the inductance of the inductor. The degree of reduction

  depends on the diameter of the induction coil, the thickness of the substrate and the thickness or surface

of the metal layer.

  Removal of the metal layer 14, by grinding various amounts of its surface or thickness, has the effect of increasing the inductance until the entire metal layer is removed; it is desirable to use a highly conductive metal in the layer to minimize the reflected loss in the inductor circuit. Reflected loss decreases the factor

of merit of the inductor.

  For example, in an inductor presenting a

  winding having an outer diameter of 2.5 mm on a substrate

  With an alumina tread of 0.25 m-m thickness, the inductance is decreased by about 35% when a 25 micron thick copper layer is deposited on the lower surface of the substrate. Thus, we have a range of

35% setting.

  In the embodiment of FIGS. 3 and 4, a magnetic layer 16 of high resistivity is used.

  instead of the metal layer 14 described above.

  The inductance of the winding is increased because of the proximity

  mity of the magnetic layer. When the latter is partially removed, either at the surface or in thickness,

  the inductance decreases until the entire magnetic layer

  that has disappeared. The degree of increase of the inductance de-

  hangs from the permeability of the magnetic material used

  and the thickness or surface of the layer.

  For example, in an inductor having a winding having an outer diameter of 1.4 mm on a substrate

  made of 0.25 mm thick alumina, the inductance is a-c-

  about 17% when a fe-rrite magnetic layer

  alpha thickness of 50 microns is deposited on the surface.

  this opposite of the substrate. Therefore, the adjustment range

is about 17% in this case.

  It is therefore well understood that the function of the metal coating is to ensure an overall reduction

  inductance from the value determined by the

  driver proper. A setting consisting of increasing

  the inductance of various values consists in removing various amounts of the thickness or preferably the surface of the

  metal coating. The use of magnetic coating

  that increases the inductance from the value determined by the inductor itself. Adjustment of decreasing the inductance is accomplished by removing various amounts of the thickness or surface of the magnetic coating. In-consequence, the role of the magnetic coating

  is to ensure an overall increase in inductance.

  The process employing a magnetic coating

  gnetic is more advantageous since the increase

2485247

  of inductance and the much smaller thoughtful loss

  result in a greater merit factor of

ducer.

  However, in case of excessive adjustment, the coating

  metal can be easily replaced by brushing a conductive paint or an epoxy

replace the removed areas.

  The adjustment of the inductance can be accomplished by grinding off the metallic or magnetic coating of the substrate after it is inserted into a circuit while the coated surface is exposed. A laser trimming is

also possible.

  As a result, it is obvious to the specialists

  that the present invention relates to a thin or thick film inductor, which is adjusted without affecting the hermetic seal or modifying the physical characteristics of the

  the inductor or the circuit in which the latter is incorporated.

  It is also obvious that the inductor can be adjusted during manufacture or after incorporation into a

independent circuit.

  It goes without saying that many modifications can be made to the described inductor and process and

  shown without departing from the scope of the invention.

6 24-wt

Claims (10)

  1. An adjustable inductor characterized ce _ comprises a substrate (10) non-conductive élecur-i.it,   an electric inductor (12) placed on a surface at the zuos   trat (10), and a layer (14) of an electrically conductive or magnetic material placed on the surface of the substrate   which is opposed to the inductor (12).   2. An inductor according to claim 1, characterized   in that the layer (14) is made of a highly driver.   3. Inductor according to claim 1, characterized   in that the layer (14) is made of a magnetic material high resistivity.   4. Inductor according to claim 1, characterized   in that the thickness or the surface of the layer (14)   chosen to ensure a value inductance of determined.   5. Method of adjusting the inductance of a   Thin or thick film conductor placed on a surface of a substrate, characterized in that it consists in depositing a layer (14) 'of an electrically or magnetically conductive material on the surface of the substrate (10) which is opposite to the inductor (12).   6. Process according to claim 5, characterized   in that, when the layer is of highly conductive metal, it consists in reducing the thickness or the surface of the layer (14) to increase the inductance to a predetermined value.   7. Process according to claim 5, characterized   in that, when the layer is of high resistivity magnetic material, it consists in reducing the thickness or the surface of the layer to reduce the inductance to a predetermined value.   8. Method of producing a regulated inductor   thin film or thick film, characterized in that it comprises: placing a thick film or thin film inductor on a surface of a non-electrically conductive substrate (10), and   depositing a layer (14) of a conductive material   electrical or magnetic energy on the surface of the   trat (10) opposite the inductor (12)   9. The method of claim 8, characterized   in that the layer (14) is made of a highly conductor of electricity.   10. Process according to claim 8, characterized in that the layer (14) is made of a magnetic material of high resistivity.