Patent Application
20250062062
The present invention relates to magnetic components, their integration with printed circuit boards, and related methods.
Miniaturised power electronics are a key component in enabling high performance and miniaturised electronics. Printed circuit boards with embedded magnetic materials (i.e. with a high magnetic permeability) have been proposed in order to improve miniaturisation and reliability of magnetic devices (e.g. transformers, inductors) 1.
Inductor and transformer devices with magnetic material cores are in widespread use in electrical power converters, filters, and galvanic isolators.
Printed circuit boards with embedded magnetic core material are promising for providing high density and high performance inductors. Further improvements in this technology are desirable.
According to a first aspect of the invention, there is provided a device, comprising:
The term “conducting” means electrically conducting.
The through core via may be at least partially surrounded by the magnetic core layer.
The upper conducting layer may be a patterned upper conducting layer, and the lower conducting layer may be a patterned lower conducting layer. The patterned upper conducting layer, patterned lower conducting layer and the through core via may together define an inductor winding around an inductor core, the inductor core comprising at least a region of the magnetic core layer.
The inductor winding may comprise a plurality of turns around the inductor core, with a first portion of each of the plurality turns of defined by the patterned upper conducting layer and a second portion of each of the plurality of turns defined by the patterned lower conducting layer.
The patterned upper conducting layer may be one of a plurality of patterned upper conducting layers on an upper side of the magnetic core layer. Each of the plurality of upper conducting layers may define at least a part of the inductor winding. The patterned lower conducting layer may be one of a plurality of patterned lower conducting layers on a lower side of the magnetic core layer. Each of the plurality of lower conducting layers may define at least a part of the inductor winding.
A patterned upper conducting layer and a corresponding patterned lower conducting layer may define a winding layer.
Each of the patterned upper conducting layers may be connected to a corresponding patterned lower conducting layer by a through core via that defines a conducting path through the magnetic core material layer.
The upper conducting layer may be a first upper conducting layer and the device may comprise a second upper conducting layer. The lower conducting layer may be a first lower conducting layer, and the device may comprise a second lower conducting layer. The through core via may be a first through core via, connecting the first upper conducting layer to the first lower conducting layer. The device may comprise a second through core via, concentric with the first through core via. The second through core via may connect the second upper conducting layer to the second lower conducting layer.
The first through core via may surround the second through core via.
The device may comprise more than two upper conducting layers, and more than two lower conducting layers, each of the more than two upper conducting layers and the more than two lower conducting layers forming the inductor winding.
Through core vias may connect corresponding upper and lower patterned conducting layers.
The (or at least one, or each) through core via may be in contact with the magnetic core layer. The through core via may be in contact with a conformal insulating layer (i.e. that is conformally coated) configured to provide insulation between the through core via and the magnetic core layer. The conformal insulating layer may comprise polypyyrole, or a similar insulating material that can be electrodeposited, for example.
The through core via may be in contact with the magnetic core, even where the magnetic core is a conducting material (e.g. with a resistivity less than 0.1 ohm·mm). In such embodiments an isolation gap may be defined between the magnetic core and any other conductors of the device.
The magnetic core layer may be one of a plurality of magnetic core layers between the upper conducting layer and the lower conducting layer.
The device may further comprise an upper magnetic layer and a lower magnetic layer, wherein the upper conducting layer is disposed between the upper magnetic layer and the magnetic core layer, and the lower conducting layer is disposed between the lower magnetic layer and the magnetic core layer.
The inductor core may comprise at least a region of the plurality of magnetic core layers.
The magnetic core layer may be an electrical insulator (or may be a poor electrical conductor for example with an electrical resistivity of 0.1 ohm·mm or more, or 0.01 ohm·m or more). The magnetic core layer may comprise a sputter deposited material. For example, the magnetic core layer may comprise a sputtered Co—Zr—Ta—B material. The magnetic core layer may comprise a Co—Zr—Ta—B composite, in which the Co—Zr—Ta—B is co-sputtered with an insulating phase. The insulating phase may comprise a silicon oxide.
The thickness of the sputter coated magnetic core layer may be less than 50 microns, less than 20 microns, or less than 10 microns.
The magnetic core layer may comprise a non-metal (e.g. polymer) matrix with embedded metal particles. The particles may be any shape and size distribution—for example, spherical, flakes, rods, monodisperse, polydisperse.
The device may be a printed circuit board. The device may be a power converter (e.g. comprising a printed circuit board). The device may comprise a silicon substrate or a ceramic substrate.
The upper conductive layer, lower conductive layer and the through core via may comprise or consist of the same material.
The printed circuit board may comprise fibre-reinforced polymer composite layers.
The first and second conducting layers may comprise copper.
The layers (first and second conducting layers, magnetic core etc) may be disposed in offset parallel planes
According to a second aspect, there is provided a method of processing a printed circuit board, the printed circuit board comprising a conducting upper layer and a conducting lower layer, and a magnetic core layer between the conducting upper layer and the conducting lower layer.
The method comprises:
At least partially filling the through core hole may comprise electroplating a metal into the through core hole.
The method may comprise conformally coating an insulating material on an interior surface of the through core hole prior to at least partially filling the through core hole with a conductor. Conformally coating an insulating material on an interior surface of the through core hole may comprise electrodepositing the insulating material or vapour phase depositing the insulating material. The thickness of the insulating layer may be less than or equal to the thickness of either of the first conducting layer or the second conducting layer.
The method may further comprise patterning the upper conducting layer and/or the lower conducting layer.
Patterning the upper conducting layer or the lower conducting layer may comprise patterning a resist layer and etching a pattern defined by the resist layer in the upper or lower conducting layer.
The patterning may comprise forming an inductor from the conducting upper layer and the conducting lower layer.
The method may comprise forming a device according to the first aspect, including any optional features thereof.
According to a third aspect, there is provided a device comprising:
The core layer may be a magnetic core layer (but this is not essential to the third aspect).
The first via and the second via may comprise part of an inductor winding. The inductor winding may be configured such that current flowing in the inductor flows in the same direction through the first via and the second via. The inductor winding may comprise a plurality of pairs of concentric vias, each pair of concentric vias comprising a first via and a second via. When a current flows in the inductor, the current flow in the first via and second via in each pair may be in the same direction (different pairs of vias may have current flow in different directions).
At least one of the first upper conducting layer, second upper conducting layer, first lower conducting layer and second lower conducting layer may be patterned to form an inductor winding around an inductor core. In some embodiments the inductor core may comprise at least a region of the magnetic core layer (but this is also not essential).
The first via and the second via may be through core vias that are at least partially surrounded by the magnetic core layer.
The device may comprise more than two patterned upper conducting layers, and more than two patterned lower conducting layers, each of the more than two patterned upper conducting layers and the more than two patterned lower conducting layers forming the inductor winding.
According to a fourth aspect, there is provided a method of making a device according to the third aspect. The method may comprise:
forming a first through hole through the core layer:
According to a fifth aspect, there is provided a method of using the device according to the first or third aspect as at least part of an inductor, transformer or power converter.
Features of the device of the first aspect may be combined with features of the device of the third aspect, including optional features. Features of the device of the third aspect may be combined with features of the first aspect, including optional features. The method of the second aspect may be used to form a device according to the third aspect. Method steps from the fourth aspect may be used in the method of the second aspect,
Reference to “upper” and “lower” in this specification should be understood as relative terms, not implying a specific orientation of a device. Figures may have an exaggerated thickness scale, in order to more clearly illustrate features of the invention. Figures are not necessarily to scale. In each of the embodiments, conducting layers may be patterned to define conducting tracks (e.g. to form an inductor winding).
The layers of the device 100 may be arranged in parallel planes, offset from each other in the direction normal to the planes. Devices 100 in accordance with embodiments (of any aspect) may comprise a printed circuit board (rigid or flexible), a package or interposer comprising at least one ceramic layer, or a silicon substrate. The conducting layers (upper and lower) may comprise a metal conductor (e.g. copper), and the through core via 121 may comprise the same material as the conducting layers 101, 111.
In an embodiment, the device 100 may comprise a printed circuit board. Multi-layer printed circuit boards may comprise one or more core layers and one or more pre-preg layers. The core layers are pre-cured, and the pre-preg layers are not fully cured. Pre-preg layers may be combined with the core layers and the resulting stack cured to bond the stack together (with the pre-preg layers bonding to any adjacent core layers). Each of the pre-preg and core layers may comprise fibre reinforced composite (complying with FR4 or similar).
At step 205 a hole 122 is formed through the upper and lower conducting layers 101, 111 and the magnetic core layer 131, for example by drilling (e.g. using mechanical or laser drilling).
At step 206, a metal layer is deposited to form a through core via 121 that connects the upper conducting layer 101 to the lower conducting layer 111 through the magnetic core layer. The additional metal may increase the thickness of the upper and lower conducting layers, and may be electrodeposited. The through core via 121 may be entirely surrounded by the magnetic core layer 131, or only partially surrounded by the magnetic core layer 131.
Embodiments may provide enhanced flux coupling to the magnetic core layer 131 resulting from currents carried by the upper and lower conducting layers 101, 111. The closer that the current carrying conductors are to the magnetic core material, the better the coupling of flux to the magnetic core material. Embodiments of the invention therefore enable higher performance and/or more compact passive components, such as inductors, to be formed. Such devices may be integrated with printed circuit boards or other devices comprising magnetic core layers.
The conducting material of the through core via 121 may be in contact with the magnetic core layer 131. For example, the magnetic core layer 131 may be an electrical insulator, or have a very low electrical conductivity. Suitable magnetic core materials may comprise polymers loaded with metal (e.g. ferrite) particles or flakes, or polymeric magnetic materials.
In other embodiments, the hole patterned for the through core via 121 may first be coated with a layer of insulating material before a conducting layer is deposited to form the through core via 121. The insulating material may, for example, be electrodeposited (e.g. polypyrrole or another electrodepositable polymeric material), or vapour deposited (e.g. parylene or another material suitable for conformal vapour deposition). The thickness of the insulating material between the through core via 121 and the magnetic core layer 131 may be less than 50 microns, 20 microns, 10 microns, 5 microns, or less than 2 microns. A typical design rule spacing in PCB design is ˜250 microns or more.
In some embodiments, a conducting magnetic core material may be used, and the through core vias 121 may be in contact with the conducting magnetic material of the magnetic core layer 131.
A similar technique may be used to isolate regions of the magnetic core layer from any other conductors that should not be in contact with the magnetic core layer.
This embodiment is similar to those already described, except that there are pre-preg layers 135, 136 separating the upper conducting layer 101 and lower conducting layer 111 from the core layer 132 and the magnetic core layer 131. The upper conducting layer 101, lower conducting layer 111 may be patterned to define windings of an inductor (together with the through core vias 121). The inductor may be wound about a region of the magnetic core layer 131. Efficient magnetic flux coupling with the magnetic core layer 131 may be achieved as a result of the lack of spacing between the through core vias 121 and the magnetic core layer 131.
This embodiment is similar to the device of
In embodiments the upper magnetic layer 137 may be disposed between pre-preg layer 135 and the upper conducting layer 101 (rather than disposed in a cavity defined in the pre-preg layer 135. Similarly, the lower magnetic layer 138 may be disposed between pre-preg layer 136 and the lower conducting layer 111 (rather than disposed in a cavity defined in the pre-preg layer 138).
The inclusion of the upper and lower magnetic layers 137, 138 enhances the inductance of an inductor defined by the first upper conducting layer 101, first lower conducting layer 111 and the through core vias 121, by providing a material with high permeability in contact with the conductors defining the inductor. As already discussed, direct contact between the magnetic material and the conducting layers is possible where the magnetic material is non-conducting. A thin insulating layer (e.g. 20 microns or less, or microns or less, as already described with reference to the vias) may be used to isolate a magnetic material from the conducting layer (while still providing efficient flux coupling)
Other variations are possible—for example, different layer stacks of pre-preg and conducting foils are possible. Further core layers may also be employed.
In certain embodiments, the type of multilayer construction discussed with reference to
In the approach of
The first upper conducting layer 101 is disposed on an upper side of the magnetic core layer 131 (and may be, but does not have to be, in direct contact therewith). The first lower conducting layer 111 is disposed on lower side of the magnetic core layer 131 (and may be, but does not have to be, in direct contact therewith). The first upper conducting layer 101 and the first lower conducting layer 111 are connected by a first through core via 121. The second upper conducting layer 102 is disposed on an upper side of the first upper conducting layer 101, and the second lower conducting layer 112 is disposed on a lower side of the first lower conducting layer 111. An insulating layer 142 separates the first upper conducting layer 101 from the second upper conducting layer 102, and a similar insulating layer 142 separates the first lower conducting layer 111 from the second lower conducting layer 112. A second through core via 122 connects the second upper conducting layer 102 to the second lower conducting layer 112. The first through core via 121 is concentric with the second through core via 122. In this example the first through core via 121 is an outer via, with the second through core via 122 surrounded by the first through core via 121. The first through core via 121 is not spaced apart from the magnetic core layer (i.e. there is no design rule requiring spacing between the patterns defining the first through core via 121 and the magnetic core 131). The insulating layer 142 may, for example, be electrodeposited (e.g. polypyrrole or another electrodepositable polymeric material), or vapour deposited (e.g. parylene or another material suitable for conformal vapour deposition).
This concentric via arrangement may advantageously reduce the footprint of a device. An inductor comprising concentric through hole vias 121, 122 may have higher inductance for a given footprint, and/or higher power density. This concentric via arrangement may also be applicable more widely, to devices that do not comprise a magnetic layer.
The first through core via 121 connects the first upper conducting layer 101 to the first lower conducting layer 111. The second through core via 122 connects the second upper conducting layer 102 to the second lower conducting layer 112, and the second through core via 122 is surrounded by the first through core via 121. The third through core via 123 connects the third upper conducting layer 103 to the third lower conducting layer 113, and the third through core via 123 is surrounded by the second through core via 121. Thin insulating layers (as already described) are used to isolate the first, second and third through core vias 121, 122, 123.
The conductor layers 101, 102, 103, 111, 112, 113 and vias 121, 122, 123 together define an inductor winding around the magnetic core, comprising three turns. The first turn comprises the first layers 101, 111, connected by the first through core via 121. A via 128 (between the first and second lower conductive layers 111, 112) connects the first turn to the second turn. The second turn is defined by second layers 102, 112, connected by the second through core via 122. A via 129 (between the second and third lower conductive layers 112, 113) connects the second turn to the third turn. The third turn is defined by the third layers 103, 113, connected by the third through core via 123.
This embodiment includes the features of the first and second aspects. In the depicted embodiment, there is no spacing between the first through core via 121 and the magnetic core layers 131a-d. This is not essential. In certain embodiments according to the second aspect, there may be a minimum design rule spacing between a pattern defining the first through core via 121 and the magnetic core layers 131a-d (e.g. of at least 20 microns, at least 50 microns, or at least 100 microns).
The material core layer may be deposited using a range of different methods, for example by sputter deposition, or paste deposition. In some embodiments an entire PCB core may be formed from magnetic material (rather than placing a magnetic layer within a cavity in an existing core layer).
Devices according to embodiments may be used in a range of functions such as: filtering: for energy store and release; and in switch mode power converters. Devices according to embodiments may be used in signal or power transformers, used to achieve functions such as galvanic isolation, voltage or impedance transformation.
Embodiments are applicable to any magnetic device utilizing magnetic material for magnetic flux enhancement.
Certain embodiments comprise a non-isolated point of load DC-DC converter, which is commonly used to generate a well-regulated voltage rail for use by an integrated circuit. The input voltage to the converter might be a battery voltage which might be at a nominal level such as 3.7 V (depending on the electrochemistry used). As the battery discharges, the converter may use closed loop control to maintain an output voltage tightly regulated at a desired level for the “load” circuitry such as 1.8 V. This tight regulation level should be maintained in the presence of input voltage or load variations or disturbances. An example of this type of DC-DC converter/regulator is the MicroSiP™ power module from Texas Instruments. Embodiments may comprise similar regulators with the features described herein.
Although example processes have been described for forming devices in accordance with an embodiment, a range of processes may be used. The steps described by way of example are merely illustrative and not exhaustive. Additional steps may be used, for example to planarize the magnetic core layer (or an adhesive fill holding the magnetic core layer in place).
Although example embodiments have been described in which the magnetic core layer is disposed in a cavity formed in a core layer, this is not essential. In some embodiments the magnetic core layer may be deposited on a core layer (e.g. sputter coated as a thin layer), or on any other substrate layer (e.g. ceramic, silicon etc).
Embodiments have the potential to provide higher density inductors, which may enable future advances in compact electronic or electrical devices.
The scope of the present invention is not intended to be limited by the example embodiments, but should be determined with reference to the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2119005.3 | Dec 2021 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/087537 | 12/22/2022 | WO |
