DE10031064C2 - Microtrafo and circuit arrangement with it - Google Patents

Description

The invention relates to an integrable in an IC package Mirkotrafo, which is on a substrate made of a semiconductor mat rial is arranged and two having several turns Coils and a core magnetically coupling the coils summarizes.

Such an integrated in an IC housing, which can be integrated as an SMD component, for example on printed circuit boards, can be used for example for DC-DC voltage conversion or for the galvanically isolated power transmission to a component. Such a component can greatly contribute to further integration and miniaturization in many areas of electronics. Mikrotrafos are known in the prior art in different execution. In "A new hybrid technology for planar microtransformer fabrication" by O. Dezuari, SE Gilbert, E. Belloy, MA M Gijs, published in Sensors and Actuators A 71 ( 1998 ), 198-207, a toroidal transformer is described in which a Toroidal core made of magnetic material is wound by two or more coils having coils. These are next to each other in the coils: In the exemplary embodiment shown, the primary coil is wound around ¾ of the toroid, the secondary coil occupies the last quarter. In addition, "Load Characteristics of a Spiral Coil Type Thin Film Microtransformer" by K. Yamaguchi, E. Sugawara, O. Nakajima, H. Matsuki and K. Murakami, appeared in IEEE TRANSACTIONS ON MAGNETICS, VOL. 29, NO. November 6, 1993, page 3207-3209, a flat coil transformer is known, in which the first and second coils are each formed as in one plane, spiraling inward spiral-shaped conductor sections, which lie in two planes one above the other and are galvanically separated from one another, whereby the coils are surrounded on the top and bottom by a core made of magnetic material.

A disadvantage of the known embodiments is that for the individual coils require a relatively large amount of space, esp especially if the coils have a larger number of turns sen, which affects the overall size of the micro-transformer acts.

A micro transformer with the features mentioned above is also possible from US 4,975,671 A. His coils are with loop-like coil conductor sections formed in the We essential in perpendicular to the surface of a substrate standing levels and a magnetically coupling Enclose core. The connection of the individual loop arti gene coil conductor sections to form the turns of the Transformer takes place in one plane of the substrate surface. The result is a primary and a secondary coil of the Transformers, whose turns are mutually in one Essentially perpendicular to the substrate surface Enclose layer. So that is the extent of the transforma torsion perpendicular to the substrate surface relatively impressed.

Also in the case of a transformer which can be found in US Pat. No. 6,031,445 A. mator for integrated circuits which are enclosed Essentially turns of two coils in vertical to planes lying on a substrate surface. That is also here the expansion is perpendicular to the substrate surface big in size.

A flat-coil transformer is known from US 4,080,585 before whose turns are formed by two coils are that on both sides to a flat support element (board) arranged, strip-like coil conductor sections by Kon clocking holes connected in the carrier element are. The coil conductors belonging to the two coils cuts are arranged so that one inside the other nesting of the coils is obtained. A magnetic core is not provided here.  

From US 6,054,914 A is also a multilayer Transfor mator known. Each of its coils has several E planar windings that contact each other are. The alternate from level to level Windings of a primary coil and a secondary coil. The Contacting the turns in the individual levels is accordingly complex. A magneti is also missing here core.

A thin-film transformer is also known from US Pat. No. 5,420,558 with two thin film coils, each with at least two have spiral coil parts lying in one plane. The coil parts belonging to a coil are located in each case le on a common level. One can be between the coils magnetic core.

The object of the invention is to provide a micro-transformer admit that in general and especially when using Coils with a higher number of turns are built sufficiently small that can.

To solve this problem, a micro transformer is the input specified type, in which each coil is sourced from one on the substrate, lower and an upper coil part, each consisting of at least one coil conductor section hen and con to each other to form the respective coil are clocked, the upper and the lower ren coil parts of the two coils essentially in each lie on one level and are arranged so that the right sulting coils or the two coil parts themselves are twisted.

In the transformer according to the invention, the are particularly advantageous Coil conductors or the resulting coils themselves wound. This allows it to be relatively small within a available space also with relative coils  to integrate high numbers of turns and at the same time extremely cheap (efficient) coupling between the two Spu len. According to the invention, each coil consists of one upper and a lower coil part, the lower coil Parts of the primary and secondary coils essentially in egg a first (lower) level; The same applies for the two upper coil parts of the two coils in one second (upper) level, with the upper and lower coils parts lie directly one above the other. The coil parts depending on the design of the coil contacted. By appropriate training and arrangement of Coil parts are thus the coils wound into each other det, or are the two coil parts themselves into each other sore.  

After a first design of the invention, the microtrafo be designed as a toroidal transformer. He has a core in Shape of a toroid with arranged below and above Coil conductor sections, the being substantially straight linear conductor sections of each coil part star-shaped or run radially outwards and the conductor sections of the the two coil parts of one level alternately arranged are net, and being the inner and outer ends of the two Coil parts of a coil lying one above the other are connected. Due to the alternating arrangement of the lei ter sections of the two coil parts on one level (the star shaped coil parts interlock virtually) is on simple way of making the intertwined at the coils possible. Of course, the respective Spu parts arranged with respect to each other so that the inner and outer ends of the conductors to be contacted sections lie directly one above the other.

According to the invention, the ring core itself can be made up of several mutually isolated layers exist, what regarding Suppression of any eddy currents is an advantage. Wei terhin is the toroid against the coil and the coils insulation provided against each other, in which serving and corresponding to the through-contacting of the coil parts depending on the location of the lower and upper ends of the conductors vias positioned in sections are provided.

It is also expedient to apply one applied to the substrate Shielding layer made of magnetic material to be provided if necessary also a top-side shielding layer, this Layers also serve to return magnetic fields to the flux.

As an alternative to training as a toroidal transformer, the inventor micro transformer according to the invention also designed as a flat coil transformer  his. In this case, the coil parts are flat coils trained, the one-piece conductor sections from au eats twist inward, with the inner ends of the two each because a coil-forming, superimposed coil part le are contacted. Here too, the coil parts are made of led into each other. In contrast to the toroid leadership are much less here than in the pre seen, the core against the coils and the coils against each other vias designed for insulating insulation, namely only a total of two, which are the inner ends of the Connect conductor sections together. The ladder sections themselves can be spiral or as rectangular loops be trained.

The core covers the coil parts at least above and below sided, optionally a central core section be provided. It is useful if the core at least closed on one side, preferably on several sides is to largely close the magnetic circuit.

Even when training as a flat coil transformer you can due to the stacking of the coil sections with a significantly larger number of turns in a very small space be accommodated.

The micro-transformers on the substrate are preferably thin film technology applied. As a substrate is expedient a silicon substrate is used, which with known Be layering technologies can be processed well. OF INVENTION According to the microtrafo can be integrated in an IC package his. In this case, it alone forms a component that with others can be put together on a circuit board.

The invention further relates to a circuit arrangement send a micro formed on a semiconductor substrate transformer of the type described, white on the substrate then a circuit serving to control the micro-transformer  is provided, which is contacted with the micro-transformer. If silicon is used as the substrate material, be with special advantage possible, also on the same substrate to integrate the control circuit. All in all the result is a very small unit, which both the An control as well as the supply part contains. Naturally other semiconductor materials can also be used.

In addition, a microtrafo can also be used on the substrate to be supplied further circuit be formed by the Microtrafo is galvanically isolated. According to this invention The configuration is therefore the one to be supplied by the micro-transformer also arranged on the substrate, but as a result the conductive properties of the galva semiconductor material nically separated from the micro transformer. The entire unit consisting of control circuit, micro transformer and scarf to be supplied device can be integrated in a common IC package.

Alternatively, it can be provided that the over the Further circuit to be supplied by a micro-transformer ren semiconductor substrate is formed, and so by the microtrafo is galvanically isolated, both substrates in one ge common IC package are integrated.

Further advantages, features and details of the invention he result from the implementation described below play as well as based on the drawing. Show:

Fig. 1 is a schematic diagram for explaining the construction of a toroidal transformer according to the invention,

Fig. 2 is a sectional view as a schematic diagram through a toroidal transformer according to FIG. 1,

Fig. 3 is a schematic diagram showing the construction of a flat coil transformers according to the invention,

Fig. 4 is a sectional view as a schematic diagram through a toroidal transformer according to Fig. 3,

Fig. 5 is a schematic diagram of a circuit arrangement according to the invention of a first embodiment, and

Fig. 6 is a schematic diagram of a circuit arrangement according to the invention of a second embodiment.

Fig. 1 shows a schematic diagram in the form of the basic structure of a micro-transformer 1 according to the invention in the form of a ring core transformers, as shown in sectional view in Fig. 2. The micro transformer 1 consists of two coils 2 , 3 which are wound into one another and which surround a toroidal core 4 . Each coil 2 , 3 consists of a lower coil part 5 , 6 , wherein each coil part 5 , 6 cut from substantially straight Spulenleiterab 7 , 8 . "Substantially rectilinear" is to be understood relatively in so far as, in the manufacture of the microtrafo, which is built up on the substrate 9 , preferably consisting of silicon, using thin-film technology, rectilinear and in-plane structures can be produced.

As can be seen in Fig. 1, the Spulenleiterab section 7 , 8 are star-shaped or radially outward. The coil conductor sections 7 and 8 , which, as described, each belong to the lower coil part of the coil 2 or the coil 3 , alternate with one another. As shown in FIG. 1, the conductor sections do not run directly towards the center point M, but at a certain angle with respect to what it is required to realize the coil structure winding around the toroidal core 4 . A first connection pad 10 for the first connection of the coil 2 is provided on a conductor section 7 , and a first connection pad 11 for the coil 3 is correspondingly formed on a conductor section 8 .

The two lower coil parts of the coils 2 , 3 shown on the left in FIG. 1 are covered with insulation, preferably SiO ₂ , and the core 4 is then brought onto this insulation. In the example shown, the core 4 is configured as a multi-layer core with mutually insulated layers. The inner and outer diameter of the core are chosen so that the inner and outer ends of the Leiterab sections 7 , 8 protrude slightly beyond the ring core 4 inside and outside. The core 4 is then also covered with insulation. In order to give the possibility to be able to contact the lower conductor sections 7 , 8 or the two coil parts 5 , 6 with the upper coil parts still to be formed, so-called vias are introduced into the insulation, which are holes that be etched into the insulating material and end directly at the inner and outer ends of the conductor sections 7 , 8 . In the middle representation shown in FIG. 1, these vias 12 are shown outside and inside the ring core 4 . Each via ends exactly on the respective conductor section 7 , 8 . The corre sponding adjustment and positioning can be done with known photo lithographic means and known etching technology.

After formation of the vias 12 , the upper coil parts 13 , 14 or their respective coil conductor sections 15 , 16 are now deposited on the insulation (not shown in any more detail), and during this deposition process the through-contacting of these coil conductor sections 15 , 16 through the vias 12 to the ones below Coil conductor sections 7 , 8 it follows. The coil parts 13 , 14 or their Spulenleiterab sections 15 , 16 also extend in a corresponding direction from the center M. Each conductor section 15 , 16 extends from an outer via to an inner via, which in turn leads to an underlying conductor section of the corresponding one below lying coil part leads, which in turn stretches outwards to an external via, which in turn contacts upwards, etc. In this way it is possible to form the coils 2 , 3 which are wound into one another.

As shown in the right-hand illustration in FIG. 1, two further connection pads 17 , 18 for the two coils 2 , 3 are provided on two coil conductor sections 15 , 16 of the upper coil parts 13 , 14 .

Fig. 2 shows a schematic diagram in the form of a sectional view through the toroidal transformer. 1 Optionally, a magnetic shielding layer 19 (which is only shown in dashed lines here) can be applied to the substrate 9 , which has a thickness of approximately 2-3 μm. Subsequently, a first layer of insulating material is deposited, the insulation being designated 20 overall in FIG. 2, since the individual insulation layers on the finished component can no longer be distinguished. After this insulation layer has been deposited, the two coil parts 5 , 6 are deposited, two coil conductor sections 7 , 8 being shown in FIG. 2. At closing, another insulating layer is deposited, on which the core 4 is then deposited from the magnetic material. Then an insulating material is applied again, which covers the core as a whole. After this, the vias 12 are formed, which, as said, are etched into the insulating material. In the next step, the two upper coil parts 13 , 14 are deposited, of which two coil conductor sections 15 , 16 are shown in the example shown. At the same time, conductive coil material is also introduced into the vias 12 during this deposition process, as a result of which the plated-through hole to the conductor sections below is achieved. Finally, an upper insulating layer is applied, onto which a second shielding layer 21 can optionally be deposited. The two layers 19 , 21 are only shown in dashed lines in Fig. 2 Darge. As described, the insulation here is designated as a whole by 20 and is formed by the area shown in dotted lines. Since the coils are wound around the toroid, they are shown broken off in FIG. 2.

Known are known for producing the toroidal transformer of this type Deposition techniques as well as lithography and etching techniques Wundt. They are manufactured using thin-film technology.

The dimensioning of the toroidal transformer depends on the structuring options. The inner diameter of the core is determined by the number of turns n, which can be, for example, in the range between 50-100 turns, the number of turns of the two coils 2 , 3 being the same or different. Furthermore, the diameter also determines the grid in which the coil conductor sections can be produced, or the sum of the conductor widths and the distance between adjacent conductors. This distance must have a certain minimum size in order to achieve adequate insulation of the coils by means of the insulation 20 . Subsequent circuits to be controlled or supplied via the micro-transformer require a supply voltage of approx. 4 V, newer electronics also manage with lower voltages. The micro transformer must be dimensioned accordingly so that the required output voltage is delivered. A micro transformer that delivers an output voltage slightly greater than 4 V has an outer diameter of approx. 2.5 mm. In such cases, the maximum power is in the range of approx. 150 mW. Larger outputs can be achieved by enlarging the core, and changes can also be made to the win ratio to adapt the output parameters. It is expedient if such micro transformers can have powers between 40-400 mW, with maximum power seals of approximately 200 mW / mm ² . The micro transformer itself is operated with frequencies in the MHz range.

Fig. 3 shows in accordance with the schematic diagram of the structure of a flat coil transformers 22, as shown as a schematic diagram in Fig. 4. Here too, the flat coil transformer is built up on a substrate 23 made of silicon. A first layer of core 24 is first applied to this substrate. A first insulating layer is then deposited, the insulation here also being designated by a total of 25. The lower coil parts 26 , 27 of the two coils 28 , 29 are then deposited. Each coil part 26 , 27 consists of a one-piece coil conductor section 30 , 31 . In the example shown, the coil conductor sections are designed as rectangular loops that twist inwards, and they can also be helically wound inward. Then another insulating layer, which covers the coil parts 26 , 27 , is deposited. The two coil parts 32 , 33 , which also each consist of a one-piece conductor section 34 , 35 which winds inward like a rectangular loop, are deposited on this in turn. Here too, as in the embodiment of the micro-transformer 1, the coil parts 26 , 27 and 32 , 33 are essentially congruent one above the other.

As shown in FIG. 3, corresponding connection pads 36 , 37 (for the lower coil parts) and 38, 39 (for the upper coil parts) are provided on the outer ends of the coil conductor sections 30 , 31 and 34 , 35, respectively. The inner ends of the individual coil conductor sections are positioned such that the respective ends of the upper and lower coil parts belonging to a coil lie directly one above the other. That is, the inner end of the coil part 26 lies exactly below the inner end of the coil part 33 , and the same applies to the inner end of the coil part 27 and the coil part 32 . These inner ends are via, before the deposition of the upper coil parts 32 , 33 in the insulating material formed vias with each other, while contacting the deposition of the upper coil parts 32 , 33 . In this embodiment, only two vias are required for contacting the coil parts, the vias also being produced here using appropriate etching technology, etc.

The upper coil parts are then covered again with an insulating layer, after which magnetic core material is again applied. It should be noted that the insulation is removed to such an extent before the upper core material is applied that an edge of free "lower core material is exposed there. If the upper core material is now deposited, it automatically contacts the lower one so that overall a closed "cage bil det, from which only the connection pads 36-39 are led out.

Fig. 4 finally shows a sectional view through a Mik rotrafo 22nd The two coils 28 , 29 are shown by different lines. Obviously, the respective coil parts 26 , 27 and 32 , 33 are also essentially in one plane. Also shown is the central connection of the respective upper and lower coil parts, so that a total of two total coils 28 , 29 are formed, the upper and lower coil sections of which are wound into one another. Such a flat coil transformer can also be easily produced with external dimensions of 2 × 2 mm, and somewhat higher maximum outputs can be achieved with such a transformer.

An important aspect in such microstructures is the loss that occurs during power transmission. There are four types of loss in the micro-transformers according to the invention which are relevant here:

• - resistive losses due to the conductor resistance
• - magnetic flux losses
• - eddy current losses
• - Magnetostriction and hysteresis losses

In order to minimize the resistive losses, the coils must resistances are kept as small as possible and the quality of the Coil, i.e. the ratio L / R should be as large as possible. Magnetic flux losses can be determined by the geometry of the Affect coil and core. To increase efficiency  the magnetic circuit should be closed as far as possible. Therefor it is also advantageous to have a core material with a high permeability to choose the magnetic flux as far as possible in the core narrow. A high permeability also increases the Inductance of the coils.

Eddy current losses can expediently be minimized by choosing the core material with the lowest possible product of the specific conductivity and permeability, which increases the depth of penetration of the fields. If this depth of penetration becomes too small, we can suppress the core currents by a layer system with thin layers, isolated from each other by insulation material, as shown with regard to the toroidal transformer 1 .

Magnetostriction and hysteresis losses are dependent of the corresponding properties of the core material and are made as small as possible by choosing a material Magnetostriction and coercivity minimized.

Core materials that can be used include:
Ni ₈₀ Fe ₂₀ , CoZiRe, Co-Nb-Zr, CoFe, Fe-Cr-Ta-N, Fe-Hf-C, Fe (sputtered), VAC Permenorm, VAC Vitrovac, NiZn-ferrite, although this list is not exhaustive ,

The advantages of the toroidal transformer are particularly its closed magnetic circuit with magnetization in the core plane and eddy currents outside the core plane. This is very favorable for the magnetic properties of the core, which has an advantageous effect on the losses in the core. In addition, possible eddy currents can flow through thin layers of insulation material, z. B. SiO ₂ , are suppressed in the core.

The construction of the flat coil transformer is advantageous, it requires especially does not have as many vias as the toroidal transformer,  moreover, there are fewer individual layers for its production required. The flat coils show particular advantages transformer also regarding the dimensioning, which is relative can be set free of requirements, what with the toroid transformer with regard to the extreme via concentration at the kernin nenrand sometimes causes problems with large numbers of turns. In addition, you get one with a flat coil transformer significantly higher power density.

Finally, FIG. 5 shows a circuit arrangement 40 according to the invention, comprising a micro-transformer 41 of one of the types described above, which is applied to a substrate 42 made of semiconductor material. A control circuit 43 is formed on the opposite side of the substrate, which can be implemented on the silicon substrate using simple circuitry means. The control can also be arranged on the same side of the substrate. Galvanic isolation only has to exist between the control and evaluation electronics and between the coils. The circuit arrangement 43 and the micro transformer 41 are in contact with one another, so that the micro transformer can be controlled via the circuit arrangement 43 . The entire circuit arrangement is in an IC housing (integrated circuit housing) 44 , on which corresponding contact feet 45 are provided, so that overall an SMD component is formed which can be installed on printed circuit boards in a known manner.

A further embodiment of a circuit arrangement 46 is shown in FIG. 6. There, on the one hand, a circuit arrangement 40 of the prescribed type is used, and on a further substrate 47 , preferably also made of silicon, a further circuit 48 , which is to be supplied via the micro-transformer 41 , is formed is electrically isolated from the circuit arrangement 40 , and is contacted with the microtrafo via a corresponding line connection 49 . Here, too, the entire circuit arrangement is integrated in an IC housing 50 with suitable connecting legs 51 . Furthermore, the control can also be arranged on the same side of the substrate. Electrical isolation only has to exist between the control and evaluation electronics and between the coils.

Claims (18)

1. A micro-transformer that can be integrated into an IC housing, is arranged on a substrate ( 9 , 23 ) made of a semiconductor material and has at least two coils ( 2 , 3 , 28 , 29 ) having a plurality of turns and a core ( 4 , magnetically coupling the coils) 24 ), each coil consisting of a lower and an upper coil part ( 5 , 6 , 26 , 27 and 13 , 14 , 32 , 33 ) relative to the substrate, each of which consists of at least one coil conductor section ( 6 , 7 , 15 , 16 , 30 , 31 , 34 , 35 ) are available and which are in contact with each other to form the respective coil ( 2 , 3 , 28 , 29 ), the upper and lower coil parts of the two coils being essentially each lie in one plane and are arranged in such a way that the resulting coils ( 2 , 3 ) or those of the coil parts ( 26 , 27 , 32 , 33 ) are themselves wound into one another. 2. Microtrafo according to claim 1, characterized in that a core in the form of a toroidal core ( 4 ) with sections arranged above and below ( 5 , 6 , 13 , 14 ) is formed, the essentially straight conductor sections ( 7 , 8 , 15 , 16 ) of each coil part run substantially radially outwards and the conductor sections ( 7 , 8 , 15 , 16 ) of the two coil parts of a plane are arranged alternately with one another, and where the inner and outer ends of the two lie one above the other Coil parts ( 5 , 14 , 6 , 13 ) of a coil ( 2 , 3 ) are connected to each other. 3. Microtrafo according to claim 2, characterized in that the toroidal core ( 4 ) consists of several mutually insulated layers. 4. Microtrafo according to claim 2 or 3, characterized in that a the ring core ( 4 ) against the coils ( 2 , 3 ) and the coils ( 2 , 3 ) against each other isolating insulation ( 20 ) is provided, in which the plated-through hole of the coil parts ( 5 , 6 , 13 , 14 ) serving and according to the position of the lower and upper ends of the conductor sections ( 7 , 8 , 15 , 16 ) positioned vias ( 12 ) are seen before. 5. Microtrafo according to one of claims 2 to 4, characterized in that a shielding layer ( 19 ) provided on the substrate ( 9 ) is provided made of magnetic material. 6. Microtrafo according to one of claims 2 to 5, characterized in that an upper-side shielding layer ( 21 ) made of magnetic material is provided. 7. Microtrafo according to claim 1, characterized in that the coil parts ( 26 , 27 , 32 , 33 ) are designed as flat coils, the one-piece conductor sections ( 30 , 31 , 34 , 35 ) winding from the outside inwards, the inner ones Ends of the two coil parts ( 26 , 33 and 27 , 32 ), one above the other, forming a coil ( 28 , 29 ) are contacted. 8. Microtrafo according to claim 7, characterized in that the conductor sections ( 30 , 31 , 34 , 35 ) spiral inwards, or are designed as essentially rectangular loops. 9. Microtrafo according to claim 7 or 8, characterized in that the core ( 24 ) covers the coil parts ( 26 , 27 , 32 , 33 ) at least above and below. 10. Microtrafo according to claim 9, characterized in that the core ( 24 ) is closed at least on one side, preferably on several sides. 11. Micro transformer according to one of claims 8 to 10, there characterized by that the core a core section arranged between the coil parts having. 12. Microtrafo according to one of claims 7 to 11, characterized in that a core ( 24 ) against the coils ( 28 , 29 ) and the coils ( 28 , 29 ) against each other insulating ( 25 ) is provided, where in the insulation ( 25 ) and optionally the central core section of the plated-through hole of the coil parts ( 26 , 27 , 32 , 33 ) serving and positioned according to the position of the inner ends of the conductor sections ( 30 , 31 , 34 , 35 ) are seen before. 13. Micro transformer according to one of the preceding claims, characterized in that the substrate ( 9 , 23 ) is a silicon substrate. 14. Microtrafo according to one of the preceding claims, characterized in that he is integrated in an IC package. 15. A circuit arrangement comprising a semiconductor substrate formed on a semiconductor substrate according to one of claims 1 to 13, wherein on the substrate ( 42 ) further one of the control of the micro-transformer ( 41 ) serving circuit ( 43 ) is provided, which with the micro-transformer ( 41 ) is contacted. 16. Circuit arrangement according to claim 14, characterized characterized that further on the substrate a further circuit to be supplied via the micro transformer is formed, which is galvanically isolated from the micro-transformer. 17. Circuit arrangement according to claim 14 or 15, characterized in that it is integrated in an IC housing ( 44 ). 18. Circuit arrangement according to claim 14, characterized in that on a further semiconductor substrate ( 47 ) is formed via the microtrafo ( 41 ) to be provided further circuit ( 48 ), which is galvanically separated from the microtrafo ( 41 ), both substrates ( 42 , 47 ) are integrated in a common IC housing ( 50 ).