TW202533638A - Method and apparatus of conductive hybrid material layer stacks with magnetic material - Google Patents

Abstract

Presented herein is the apparatus and method of stacking magnetic materials with hybrid conductive materials. These methods and apparatus can be used in the formation of PCBs but are not limited to the formation of PCBs. The layer stacks presented within have a layer of conductive hybrid material and at least one layer of magnetic material. In at least one exemplary embodiment, these layers are adjacent in a layer stack, and the magnetic layer is a magnetic hybrid material.

Description

Method and apparatus for stacking conductive composite material layers with magnetic material

The present invention relates generally and particularly to a stack of layers of conductive and magnetic materials for use in building devices in the field of microelectronics.

The present invention generally and particularly relates to a stack of conductive and magnetic material layers used to construct components in the field of microelectronics. Including magnetic materials in the stack can be beneficial in a variety of situations, including, for example, improving inductance, shielding, filtering, and relays. Therefore, including magnetic materials can be beneficial in a variety of applications, from printed circuit boards (PCBs) to inductors and general circuits.

It is well known that high-frequency currents produce strong and dense eddies. As the frequency increases, the strength and density of the eddies increase, meaning they become stronger and more localized in a specific area.

Traditionally, to handle eddy currents generated in circuits requiring magnetic materials, materials that resist the generation of currents have been used, or layers of magnetic material have been insulated from each other. Using magnetic materials that resist currents typically requires ferrites, which impose very strict limits on component size. Ferrites are also incompatible with traditional semiconductor manufacturing processes, increasing integration complexity. In many cases, metals are used, but because metals cannot resist eddy currents, they must be separated by spacers or insulation.

Ferrites and metals both face limitations as the frequency of current increases. Metal insulation must be stronger, metal layers must be thinner, and ferrites require too much space in high-frequency circuits.

The formulation of low-cost conductive composites that are compatible with traditional semiconductor manufacturing processes has enabled more devices to become high-frequency capable. The lower cost and complexity of producing conductive composites has allowed these devices to be integrated into consumer applications on a large scale. This means that conductive composites are now being combined with traditional magnetic materials and novel composite magnetic materials in a variety of devices.

Combining conductive composites with traditional magnetic materials is crucial because it enables conductive composites to be used in a wide range of components. However, not all components that incorporate conductive composites need to be able to handle high frequencies.

One characteristic of conductive composites is that the same amount of material exhibits superior high-frequency performance compared to traditional materials due to their superior frequency performance per unit area. To achieve similar performance, it's sufficient to pass a current that the traditional material can handle. However, if the current is simply reduced, the conductive composite no longer needs to maintain the same dimensions as the traditional material. This means that using conductive composites can achieve smaller components than using traditional materials at the same frequency.

One example is PCB traces, which are typically about 17.5 microns thick, or 1/2 ounce, of copper, produced by electroplating or copper foil lamination. When using a conductive composite material, such as a copper composite, the thickness of each copper layer is only 0.1 to 2 microns (typically chosen to be 3 to 5 times thinner than the concentration depth of copper at the target frequency), and the porous insulating layer is about 30 to 200 nanometers thick. When these layers are stacked until the composite material is the same thickness as traditional traces, its performance is far superior to that of traditional traces. However, the layer formation can be stopped at the point where the performance is equivalent to that of traditional materials, allowing for even smaller traces.

The ability to integrate conductive materials with traditional magnetic materials is beneficial because it allows for smaller components without changing the magnetic material requirements of these systems. Not all microelectronic and semiconductor components need to reach cutting-edge performance. For example, the automotive industry has found that older systems are sufficient to meet its needs. Even so, these older systems can be manufactured more cheaply by saving space and material costs. Therefore, incorporating conductive composites into systems alongside traditionally used materials is beneficial.

At the forefront of the industry, high-frequency performance is highly sought after. Traditional magnetic materials cannot handle the same frequencies in the form factors that conductive composites can, and therefore cannot meet the required parameters of consumer devices (for example, if ferrite were used to handle high frequencies, the size of a mobile phone would far exceed its intended use). Therefore, the ability to integrate conductive composites with magnetic composites to optimize performance is also crucial.

The need for integration is driven not only by performance but also by manufacturing complexity. For many high-frequency-capable materials, integrating them into a coherent system is complex and expensive, making this a common practice in consumer devices. For example, at the time of this writing, a single high-frequency, compact, and high-frequency-capable high-frequency laminated magnetic core can cost thousands of dollars. Putting 12 of these cores into a mobile phone could increase the price by more than tenfold.

Therefore, there is a need to fully introduce conductive composite materials into systems containing magnetic materials, both literally and figuratively.

The present invention combines conductive composite materials with magnetic materials, including composite magnetic materials. These layer stacks can be used to form electrical system components.

Therefore, the present invention provides a device and method for stacking composite magnetic materials and composite conductive materials. These methods and devices can be used to form electrical components, including but not limited to components used in PCBs, transmission lines, inductors, relays, motors, generators, shielding, memory storage, transformers, sensors, and solenoids.

These devices and methods address the complexity of integrating magnetic materials into components. Because the manufacturing process for composite materials (i.e., composite magnetic and composite conductive materials) involves electroplating of the insulating layer, many intermediate steps, including the formation of a solid insulating layer, can be eliminated. This reduces the cost and complexity of the layer stack. The performance of the composite magnetic material is well-matched with the thin, fine, porous insulating layer, optimizing the performance of both.

The device of the present invention is a layer stack of a composite magnetic material and a composite conductive layer. These layer stacks may include additional layers, but fundamentally, they consist of a magnetic material and a composite conductive material. By using a composite conductive material, the complexity of forming the magnetic material on the conductive layer is reduced. Even with simple magnetic materials, they can be used effectively.

One layer stack of the present invention comprises a composite conductive layer followed by a magnetic layer, such as a NiFe layer. Another layer stack of the present invention comprises a conductive composite material layer followed by a composite magnetic layer. These layers can be stacked directly on top of each other. These layer stacks can include further layers in the final stack, such as a series of composite conductive material, magnetic material, and composite conductive material layers.

Therefore, the present invention provides a layer stack comprising an initial layer of conductive magnetic material and at least one additional layer connected in series to the initial layer, wherein at least one additional layer is a magnetic material, and a method of forming the layer stack.

The conductive composite material of the initial layer of the stack can be a copper-based composite material. In one exemplary embodiment, at least one additional layer is a magnetic composite material. The magnetic composite material can be a nickel-iron (NiFe)-based composite layer, and the magnetic layer can be a NiFe layer.

The conductive material layer and the magnetic material layer can be adjacent to each other or separated by an insulator. However, when a porous insulator is placed between the layers, it is not considered a separating layer because the layers will be connected through the voids in the porous insulating layer.

At least one additional layer may be a conductive material, such as copper or a copper-based composite.

These layers may be formed, for example, during the PCB manufacturing process and thus integrated into the PCB, such as as traces or as primary layers of a multi-layer PCB. (It should be noted that stacks of these layers may also be formed on the PCB).

In at least one exemplary embodiment, at least two additional layers are formed, sequentially followed by a NiFE composite followed by a copper composite. This is an exemplary embodiment of a layer stack comprising, in sequence, a conductive composite, a magnetic composite, and a conductive composite.

In at least one exemplary embodiment, at least two additional layers are sequentially connected, following the order of the NiFe layer followed by the copper composite. This is an exemplary embodiment of a layer stack, wherein the layers sequentially include a conductive composite, a magnetic material, and a copper composite.

The present invention describes a layer stack comprising a layer of a conductive composite material and at least one layer of a magnetic material. In at least one exemplary embodiment, the conductive composite material and the magnetic layer are adjacent to each other in the stack. Thus, one possible layer stack is a series of layers comprising a conductive composite material, a magnetic material, and a conductive composite material, such as a copper composite material, a nickel iron (NiFe) composite, and a copper composite material. Another possible stack is a conductive composite material, a magnetic composite material, and a conductive composite material, such as a copper composite material, a NiFe composite, and a copper composite material. Such stacks are beneficial in the manufacture and use of electrical components.

These layer stacks are suitable for a variety of integration and design considerations. For example, transmission lines can incorporate magnetic shielding to prevent external electromagnetic interference and reduce crosstalk; generally, this enhances signal integrity and improves efficiency. These magnetic shields are often laminated, spaced, or shaped to reduce eddy current generation and shield against negative effects of ferromagnetic resonance (FMR).

The layer stacks described in the present invention can be integrated into these existing transmission lines in a variety of ways. It is worth exploring these methods to understand the adaptability of composite materials and the various uses of layer stacks containing composite materials.

The transmission line of the present invention can be composed of a layer of conductive material, such as a composite conductive material, and shielded with conventional magnetic materials. If the transmission line is intended to handle high frequencies, several options are available. One option is to pattern the magnetic material, as found in conventional transmission lines, which are patterned to reduce the effects of eddy currents and FMR. For example, the magnetic material can be separated by insulation or layered to reduce eddy currents and arranged in a specific pattern to reduce FMR. In essence, the composite conductive material of the transmission line is compatible with existing magnetic shielding practices.

However, magnetic composites can also be used as shielding. In this case, a layer of magnetic composite can simply be placed over the transmission line so that the magnetic composite covers the transmission line. By significantly reducing the intensity of the eddy currents, the magnetic composite can prevent the energy loss of the magnetic shield, thereby significantly improving the system even when FMR is not a consideration. However, because magnetic composites are compatible with most manufacturing processes, they can also be patterned to reduce FMR. Not only can they be patterned, but they can also be layered as traditional laminated metals can be. This means that magnetic composites can be used in the same pattern and with the same design considerations to reduce eddy currents and FMR as traditional materials. However, this approach can also have some disadvantages, which will be discussed in more depth below.

As you can understand, there's a balance between integrating composite materials with insulating laminations and using only composite magnetic materials without adding additional laminations. Lamination improves resistance to eddy currents, but it also impacts thickness, cost, complexity, and the ability to modify the magnetic shield after placement. Traditional laminations use solid, non-porous insulating layers that clearly separate the magnetic material into layers. As a result, each magnetic layer in a lamination magnetic shield has its own unique properties, such as its own skin depth. Lamination also increases the complexity of the manufacturing process because it requires additional steps to form the insulating lamination and bond the magnetic layers to it. Furthermore, the presence of these conventional insulating layers increases the complexity and cost of any patterned subtractive process, as the insulating layers are typically drill and etch resistant.

It's worth noting that, as mentioned above, at higher frequencies, the layers must be closer together to effectively reduce eddy currents. Once the frequency is high enough, the practicality of integrated lamination decreases because the spacing between the insulation layers must become increasingly thinner, increasing the complexity of shield manufacturing. Therefore, while it's possible to use traditional insulators to separate layers of magnetic composite (e.g., a magnetic composite: traditional insulator: magnetic composite pattern), this approach is generally not worthwhile.

Magnetic composites can be patterned with significantly less complexity than traditional magnetic layers or shields. They can be patterned using either additive or subtractive methods. Similar to traditional lamination, they can be patterned additively, layer by layer, during the build process. Because they eliminate the need for traditional lamination materials and additional process steps, they can be built more quickly. In contrast, with magnetic composites, the insulator is typically sprayed onto a backing layer, and the next layer is then electroplated directly onto the insulator, bonding it to the backing layer through the pores in the insulator. In many cases, patterns in magnetic composites can also be formed using subtractive methods. This is achieved when the insulating material in the magnetic composite is a porous insulating material consisting of a series of particles. These particles will be washed away during the etching of the substrate (for example, copper in a copper-based conductive composite) and will be discharged along with the chips by the drill or grinder.

As will be discussed in more detail below in the discussion of printed circuit boards, subtractive patterning allows for pattern editing or generation after manufacturing, such as by the customer.

Thus, components can utilize traditional magnetic materials and patterned composite materials. Components can also incorporate composite magnetic materials, where the composite magnetic materials are patterned and insulated like traditional magnetic materials. Components can also integrate composite magnetic materials without lamination or spacing, as is often required with traditional materials in high-frequency applications. In the latter case, composite magnetic materials offer a simpler medium to modify.

Integrating composite materials into layer stacks inherently enables more efficient use of magnetic materials in electrical component manufacturing, while reducing the complexity of component construction and the effort required to modify components after manufacturing. The insulation of the composite layers allows for low-cost manufacturing while also reducing the growth of eddy currents between layers. By using composite layers, these layers are drillable or etchable because the insulator (typically resistant to drilling or resist etching processes) is in particle form and can be washed away or easily removed by the etching or drilling process. This reduces the need for specialized drilling processes to replace the insulating layer.

The ability to integrate this invention into existing systems means there are numerous possible layer stacks. Conductive composite materials are also suitable for integration into systems using traditional, composite, or other advanced magnetic materials, making them suitable for a variety of use cases. Some of these scenarios are discussed below.

Figure 1 shows a layer stack 100 of the present invention, comprising a conductive composite material 101 and a magnetic material 110. This represents the simplest embodiment of the present invention. The conductive composite material can be, for example, a conductive composite material, and the magnetic material can be, for example, nickel iron (NiFe). The layer types can be a variety of materials, but generally, metals and metal alloys (as conductors and/or materials with high magnetic flux permeability, respectively) constitute preferred embodiments.

Figure 2 shows the layer stack of Figure 1, where the magnetic layer 110 is now a composite magnetic layer 111, which is a subtype of a magnetic layer. Composite magnetic layers generally provide better performance than non-composite magnetic layers.

It will be appreciated that only two layers are required to form a single-layer stack. A two-layer stack is a subset of a single-layer stack, comprising a conductive composite material and at least one additional layer connected in series to the initial layer, wherein at least one additional layer is a magnetic material. Here, only a single conductive composite material layer, a single magnetic layer, and a single layer other than a conductive composite material are required. Thus, in a two-layer stack, the single magnetic layer becomes the single additional layer connected to the single conductive composite layer. This stack forms a sequence of conductive composite and magnetic materials, and this sequence can be repeated as needed, with the final layer being either conductive composite, magnetic, or an additional material as a termination layer. (The termination layer may be helpful when the layer stack is integrated into a PCB.)

Notably, alternative layers can be incorporated into the layer stack, including for secondary purposes, such as controlling thermal expansion. The composite's insulating layer allows for the direct deposition of adjacent layers, provided the adjacent layers can be formed on the composite. In some cases, a void-free insulating layer can be included in the layer stack as desired. This may reduce some advantages associated with processing the final layer stack, such as the ability to quickly drill the layer stack, but may improve performance. There are many possible layer stacks, and several exemplary implementations are discussed below.

FIG3 shows a stack comprising multiple layers of conductive composite material 101 and multiple layers of magnetic material 110 .

The layer stack can also include additional layers that are non-composite or magnetic. FIG4 shows a layer stack having an additional layer 120 operatively connected to a magnetic layer 110 operatively connected to a conductive composite layer 101 . However, the additional layers mentioned herein can be conductive composite or magnetic materials, but in various embodiments, the layer types are not limited thereto. In FIG5 , the additional layer 120 is now a conductive composite layer 101 .

In addition to composite layers of magnetic layers, alternative layers may also be useful, such as insulating layers or substrate layers. Figure 6 shows a layer stack 200 of a conductive composite material 101 and a magnetic material 110, with an additional insulating layer 121 separating the stack.

These layer stacks can be integrated into or onto a variety of components, including wafers, semiconductor packages, flexible circuit boards, and PCBS. Their integration into PCBs will be discussed below. For example, Figure 7 shows a section of an integrated layer stack, comprising copper composite 101 and NiFe composite 111, on a layer of PCB substrate 122, with a solder mask termination layer 123. Here, the layer stack forms the PCB body.

Layer stacks can also be integrated into multi-layer PCBs. In at least one exemplary embodiment, a PCB substrate layer serves as at least one additional layer. Figure 8 shows an exemplary layer stack integrated into a PCB, comprising a repeated arrangement of a composite magnetic layer, a composite conductive layer, and a PCB substrate.

In a PCB, the magnetic layer and the conductive composite layer are not necessarily adjacent in all embodiments and may be separated by at least one additional layer, such as a PCB substrate layer; such a configuration is shown in FIG9 . Here, the magnetic composite layer 111 and the conductive composite layer 101 are separated by a PCB layer 122 .

Layer stacks can also be formed on the surface of a PCB. Layer stacks that combine composite and/or metal layers provide layers that can be shaped as needed without requiring extensive work. Figure 10 shows a layer stack of composite magnetic layer 111 and composite conductive layer 101 on a PCB 125.

These magnetic composite layers and composite conductive layers can be drilled like conventional metal layers, which is usually difficult to achieve in traditional laminate stacks. Figure 11 shows the drilling form of a layer stack on a PCB, where the drill hole 135 penetrates the conductive composite material layer 101 and the composite magnetic layer 111.

The ease of processing composite material layer stacks using subtractive processes is beneficial for patterning the layer stacks. Because of the ease of using subtractive processes, a layer stack can be manufactured by one company and patterned by another. For example, a customer might purchase a high-volume production PCB with a specific layer sequence, and then have the layers patterned according to their needs or desires.

However, additive processes can also be used for layer formation and patterning. Figures 12a and 12b illustrate an additive process for forming a layer stack on a flexible circuit substrate, such as one based on polyetheretherketone (PEEK). Compared to conventional flexible laminated magnetic component manufacturing, additive processes are a low-step process.

The process begins with a patterning process for the seed layer, the initial layer. The initial layer, in this case the conductive composite, is then formed. The conductive composite is deposited according to a pre-formed pattern (if any pattern is required). Once the layer is complete, the dry film is removed, and a substrate or carrier material is placed to support the next layer. Subsequent layers can be patterned as desired, and may (but need not) be patterned differently from the initial layer. This process is repeated for the entire layer stack.

The drawings show various embodiments and are intended to describe specific embodiments but are not intended to limit the scope, quantity, or pattern of the embodiments of the invention. The invention may incorporate various patterns and specific embodiments. All drawings are prototypes and rough drawings: the final product may be further refined by one skilled in the art to which the invention pertains. Nothing should be construed as critical or essential unless expressly described as such. Additionally, "a" and "an" may be understood to mean "one or more." If only a single item is intended, "one" or other similar language is used. Similarly, "has," "have," "having," or similar terms are open ended terms. The term "metal" is defined as a metal or its alloys.

100: Layer stack 101: Conductive composite material, conductive composite layer 110: Magnetic layer, magnetic material 111: Composite magnetic layer, composite material 120: Additional layer 121: Insulation layer 122: PCB substrate, PCB layer 123: Solder mask end layer 125: PCB board 135: Drilling 200: Layer stack

[Figure 1] is a perspective view of a two-layer exemplary embodiment of a stack of conductive composite and magnetic material layers. [Figure 2] is a perspective view of a two-layer exemplary embodiment of a stack of conductive composite and magnetic composite layers. [Figure 3] is a perspective view of a stack of conductive composite and magnetic layers repeatedly stacked; as shown, it is a series of copper composite and NiFi layers. [Figure 4] is a perspective view of a stack of conductive composite layers, magnetic layers, and typical additional layers. [Figure 5] is a perspective view of a layer stack comprising repeated stacks of conductive composite layers and magnetic composite layers; as shown, it is a series of copper composite and NiFi composite layers. [Figure 6] is a perspective view of a layer stack comprising repeated stacks of conductive composite layers and magnetic composite layers, as shown, including an additional insulating layer. [Figure 7] is a perspective view of a layer stack in which conductive composite layers and magnetic composite layers are integrated into a printed circuit board. [Figure 8] is a perspective view of a layer stack in which conductive composite layers and magnetic composite layers are integrated into a multi-layer printed circuit board. [Figure 9] is a perspective view of a layer stack incorporating a conductive composite material layer and a magnetic composite material layer into a multi-layer printed circuit board, wherein the conductive composite material and the magnetic material are not adjacent to each other. [Figure 10] is a perspective view of a layer stack in which the conductive composite material layer and the magnetic composite material layer are located on both sides of the PCB. [Figure 11] is a perspective view of a layer stack in which the conductive composite material layer and the magnetic composite material layer are located on both sides of the PCB through drilled holes. [Figure 12a] is a flow chart of a method for fabricating the layer stack of the present invention. [Figure 12b] is a flow chart of a method for fabricating the layer stack of the present invention.

Claims (20)

A layer stack comprises: a conductive composite material layer; and at least one additional layer operatively connected to the conductive composite material layer in a stacked manner, wherein at least one of the additional layers is a magnetic material. The layer stack of claim 1, wherein the conductive composite material is a copper-based composite material. The layer stack of claim 1, wherein at least one of the additional layers is a magnetic composite material. The layer stack of claim 3, wherein the at least one additional layer of magnetic composite material is adjacent to the conductive composite material. The layer stack of claim 1, wherein at least one of the additional layers is a conductive composite material. The layer stack as described in claim 3, wherein the magnetic composite material is a NiFe-based composite magnetic material. The layer stack of claim 1, wherein the magnetic material is NiFe magnetic material. The layer stack of claim 1, further comprising the layer stack being operatively integrated into a printed circuit board. The layer stack of claim 1, wherein at least two additional layers are operatively connected in the order of NiFE composite material followed by copper composite material. The layer stack of claim 1, wherein at least two additional layers are operatively connected in sequence in the order of NiFe composite material followed by copper composite material. A method for forming a layer stack comprises: forming an initial layer of a conductive magnetic material; forming at least one additional layer, wherein at least one additional layer is a magnetic material and the additional layer is operatively coupled in series with the initial layer. The method for forming a layer stack as claimed in claim 11, wherein the conductive composite material used to form the initial layer is a copper-based composite material. The method of forming a layer stack as described in claim 11, wherein at least one of the additional layers formed is a magnetic composite material. The method of forming a layer stack as claimed in claim 13, wherein at least one layer of the magnetic composite material is formed adjacent to a conductive composite material. The method of forming a layer stack as claimed in claim 11, wherein at least one of the additional layers is a conductive composite material. The method for forming a layer stack as described in claim 13, wherein the magnetic composite material used to form at least one of the magnetic material layers is a NiFe-based composite magnetic material. The method for forming a layer stack as described in claim 11, wherein the magnetic material used to form at least one of the magnetic material layers is NiFe magnetic material. The method of forming a layer stack as described in claim 11 further includes operatively integrating the layer stack into a printed circuit board. A method of forming a layer stack as claimed in claim 11, wherein at least two additional layers are operatively connected in sequence in the order of NiFe composite material followed by copper composite material. A method of forming a layer stack as claimed in claim 11, wherein at least two additional layers are operatively connected in sequence in the order of NiFe followed by a copper composite material.