GB2635648A

GB2635648A - Radio frequency components and manufacturing of radio-frequency components

Info

Publication number: GB2635648A
Application number: GB2315859.5A
Authority: GB
Inventors: Robertson Grant; Panarello Tullio; Ducellier Thomas
Original assignee: Trak Microwave Ltd
Current assignee: Trak Microwave Ltd
Priority date: 2023-10-17
Filing date: 2023-10-17
Publication date: 2025-05-28
Also published as: WO2025083413A1; GB202315859D0

Abstract

Methods of making RF components are claimed where laser ablation is used to selectively remove at least a first coating deposited on a substrate. The coating preferably comprises one or more thick films deposited using an atmospheric process such as liquid phase printing, spin coating, knife-edge coating or direct writing and may comprise one or more metals with a desired conductive, resistive, ferroelectric or thermal property. The thick film may be fired and plated with a metal prior to ablation (fig 1). The ablation process may also be used to form components where the substrate has been ablated to have thinner regions. The components may be formed as a number of tiles with varying RF characteristics and may include circulators, isolator, filters operating between 1 and 170 GHz. The substrate may comprise ferrite, alumina, barium titanate and diamond. The substrates may double sided and link components on opposite sides by vias though the substrate. The methods may include forming multiple components using a design that may be adjusted across subsequent components in response to measuring a component’s RF characteristics.

Description

RADIO FREQUENCY COMPONENTS AND MANUFACTURING OF RADIO-FREQUENCY

COMPONENTS

Field of Invention

The present invention relates to methods and apparatus, and more particularly to radio-frequency (RF) components and their fabrication.

Background

Radio-frequency (RF) components are often fabricated using so-called "thin films" and "thin film techniques". Such RF components comprise RF filters, isolators/circulators, couplers, resistors and other board level components amongst others, and combinations thereof (also referred to as multi-functional assemblies).

The term 'thin film" is used in the art of RF fabrication to refer to a layer of material ranging from fractions of a nanometer (in the case of a monolayer) to several microns in thickness. Typically such layers are deposited in vacuo.

The act of applying a thin film to a surface is thin-film deposition. Thin film deposition may be done by either physical or chemical methods. Most deposition techniques control layer thickness within a few tens of nanometres. So called "sputtering" which is also known as physical vapor deposition, or PVD, is one 25 of the most straightforward approaches to obtain thin films. Other methods include molecular beam epitaxy, Chemical Vapor Deposition (CVD), the Langmuir-Blodgett method, atomic layer deposition and molecular layer deposition.

These methods have been thought to be the best way to manufacture high performance RF components because of their high precision and the high degree of uniformity which they offer.

The traditional way of fabricating thin film RF components comprises multiple steps. It involves first coating a substrate (typically a ceramic material) with a stack of functional layers (resistive, conductive materials, etc.) . This step is usually done with a combination of vacuum deposition (for example sputtering) followed by plating, or entirely through sputtering.

Then once the wafer is coated, a pattern needs to be inscribed to form whatever circuitry is to be provided by the component. For high performance, high frequency RF devices with small feature sizes, this is usually realized via photolithography. This process step itself consists of multiple sub-steps: * fabricating a custom photo mask according to the desired artwork * coating the wafer with a photo-sensitive resist * exposure of the photoresist through the photo mask * development and selective removal of the photoresist * and chemical etching of the deposited layer to realize the layer's desired artwork.

This process needs to be repeated for each patterned layer. Due to the requirement of fabrication of custom masks for each exposure/etching steps and the multiple substeps involved, the overall process duration can be quite lengthy but the cost has been thought to be unavoidable in high frequency RF components because of the need for very high spatial precision.

Magnetron sputtering has high power consumption demands, leading to increased greenhouse gases emissions. Electrodeposition processes have been used as a way to manufacture thin film whilst mitigating carbon emissions, but electrodeposition has other challenges including the use of hazardous chemicals in plating baths.

The use of a set lithographic mask and chemical etching is very well suited to replicating the same motif at large volume and is extensively used in the semi-conductor industry. In view of these established processes in the general field of electronics, there has been strong prejudice in the art to stick with known fabrication techniques.

Summary

Aspects and embodiments of the disclosure are set out in the claims and aim to address at least some of the technical problems outlined 10 above, and other problems.

An aspect provides a method of manufacturing a radio frequency, RF, electrical component as set out in claim 1. Another aspect provides an RF electrical component as set out in claim 17.

The method may comprise providing a dielectric substrate, wherein a first surface of the dielectric substrate is coated with a first layer of material to cover a contiguous region of the surface into which an RF circuitry component is to be inscribed.

The coating is performed by an atmospheric pressure process and the layer may be a "thick film". As used herein, the term "thick film" may be thicker than thin films, and are typically many times thicker, but there is an overlapping range of thicknesses that can be deposited by either "thin film" or "thick film" processes. For example, thicknesses of "thick films" may be in the range of >1 micron to >100 micron. In addition, such films may be applied by atmospheric pressure liquid phase deposition technique, for example printing, spin coating, knife-edge coating, or direct writing.

The material of the film may be applied as a paste, which may subsequently be fired to form a thick film. The material may have an ability to perform an electronic function (e.g., the material may be a functional material and the film may be a functional thick film). Accordingly the thick film may have a selected conductive or resistive function and/or any other useful magnetic or thermal function.

The substrate may comprise a plurality of tiles, and each tile may be substantially covered by a continuous and complete layer. For example, the layer may cover substantially all of the tile (or tiles) provided by the substrate.

A laser, such as an ultrafast laser, is then operated to ablate material from the layer. The material is ablated from each tile to create a circuitry component on that tile. Examples of ultrafast lasers include sub-nano second lasers such as femtosecond lasers.

Typically, the circuitry component is adapted for radio frequency, RF, electrical signals. Generally these signals are in the frequency range >1014z.

Prior to ablation, the layer covers substantially all of the area occupied by the film (e.g. it may be continuous and free of any void or interruption within its outer boundary). After ablation, at least 40% of the area of the layer may be ablated to expose the substrate. Examples include at least 50% removal and at least 70% removal.

A circuitry component, such as an RF filter, an RF isolator, an RF circulator, an RF coupler or a multi-functional assembly may be provided entirely within the region which was covered by the layer prior to ablation. For example the circuitry component may be created by the ablation operation as opposed to a mere trimming of a pre-existing component.

Accordingly, an aspect of the present disclosure provides an RF electrical component comprising: a dielectric substrate having a first surface and the RF electrical component further comprising a thick film arranged to 5 provide RF circuitry; wherein a first surface of the substrate comprises: first regions, in which the substrate is covered by the conductive thick film and which are arranged in a pattern to provide RF circuitry of the RF electrical component, second regions, in which the bare substrate is exposed, wherein the first regions of the substrate are thicker than the second regions.

The thick film may comprise a functional material, which may be conductive. The first regions may be bounded by a step in the surface of the substrate. The second regions may comprise a plurality of grooves in the surface of the substrate. The grooves may be less than 5 micron in depth, for example between 3 micron and 5 micron.

The grooves may be aligned parallel with each other and may be straight. The grooves may follow a path parallel to a bounding edge of the second regions.

The methods described herein may provide digital manufacturing techniques. For example the method may comprise obtaining a digital representation of a circuitry component and operating a computer to read the digital representation and to control operation of the laser to ablate material from the layer. Such computer control can be performed without any mask. This may provide computer-controlled mask-less fabrication of any arbitrary artwork at no additional cost or time (a direct CAD-to-fab approach).

The method may comprise iteratively improving a design, such as a design to provide RF circuitry having a particular characteristic. For example such a method may comprise obtaining a first substrate, generating a circuitry component by ablation of the layer as described herein, and then testing the circuity component to assess its performance against the desired characteristic. The digital representation of the circuitry component may then be modified (e.g. based on the testing) and a second example of the circuitry component may be made by controlling the laser according to the modified digital representation. The second example may then be tested as previously and the digital representation of the circuitry component may then be modified again (e.g. based on the testing) to provide a further modified digital map of the component. This method may be repeated until a desired performance characteristic has been achieved. Such rapid fine-tuning of RF components has not been available in any prior art method.

Embodiments of the disclosure provide a set of RF circuitry components and a corresponding plurality of digital representations 20 of said components, wherein each of the plurality of components matches a corresponding one of the plurality of designs.

The RF circuitry components described herein may be configured to operate in an average power range of at least lmW, for example less than lkW, for example less than 250W, for example more than 1W. In an embodiment the circuitry components may be configured for operation at between 20W and 70W, for example about 50W (e.g., they may have a thickness and/or a width and/or a composition selected for such operation). Such examples may use a duty cycle of between 10% and 30, for example about 20%. Such examples may be configured for a pulse width of between 1 microsecond and 200 microseconds, for example about 100 microseconds. A particular example provides circuitry components configured to operate at 50W peak power with a duty cycle of 20% and a pulse width of 100 microseconds.

Any feature of any one of the examples disclosed herein may be combined with any selected features of any of the other examples described herein. For example, features of methods may be implemented in suitably configured hardware, and the configuration of the specific hardware described herein may be employed in methods implemented using other hardware.

Brief Description of Drawings

Embodiments of the disclosure will now be described in detail with reference to the accompanying drawings, in which: Figure 1 shows a flow chart of a method of fabricating an RF circuitry component; Figure 2 illustrates a wafer comprising a plurality of tiles, each carrying an RF component, and a single RF component diced from that wafer, features of the wafer are also illustrated; Figure 3 shows a flow chart for a computer implemented method of fabricating an ensemble of similar RF components according to a 20 particular characteristic; Figure 4 shows an apparatus for performing a computer controlled fabrication method such as that illustrated in Figure 3 and an RF component manufactured according to that method; Figure 5 shows a plot of RF performance characteristics of a 25 circuitry component produced according to the present disclosure (an RF pass-band filter); and Figure 6 shows a further such plot (an RF circulator).

In the drawings like reference numerals are used to indicate like elements.

Specific Description

A method 10 according to the present disclosure is illustrated by the flow chart shown in Figure 1.

By way of general introduction, the methods which will be described herein relate to mask-less fabrication of RF circuits and components for RF circuits such as circulators, isolators, filters and other elements which typically are adapted to operate in the frequency range of 1 GHz to 170 GHz.

Such high frequency components demand high precision in the spatial configuration of the conductors which make up their circuitry. The embodiments which will be described below relate to the use of ferrite or alumina substrates, but other appropriate substrates may be used.

The method 10 of processing these substrates to create circuitry components is described with reference to Figure 1.

Initially 12 a wafer of substrate, such as ferrite or alumina, is provided such a substrate may be.635mm thick and typically has two major surfaces each of which are flat Typically, the substrates are 50.8 mm square or 76.2m square and a grid comprising a plurality of devices may be created from each individual substrate. Other sizes of substrate may be used.

One or more fiducial markers may be machined 12 into the wafer. Typically, the fiducial markers are machined into the wafer at its corners and may comprise a geometric shape configured to permit alignment. Examples of such fiducials include square shapes or crosses. These may be machined into the wafer by ablation using an ultra-fast laser, such as a sub-nanosecond laser. The same laser as is used for ablating the coating (see below) may be used for this purpose.

Next, a digital representation of the circuitry component is used to identify the location of points at which the circuitry component is to be connected to a ground plane. At these locations the ultra-fast laser is used to drill 14 through-holes through the wafer from one major surface to the other major surface.

The substrate is then coated 16 using an atmospheric pressure liquid-phase process to apply an ink or paste to both surfaces of 10 the substrate. Herein "atmospheric pressure" process means a process done at close to 1 bar (as opposed to processes requiring vacuum or low atmospheric pressure). The ink or paste is also coated into the through-holes so as to provide coated vias. Examples of liquid phase atmospheric pressure processes which can be used for this coating include knife-edge coating, screen printing, and direct writing. One particularly reliable method is to use screen printing. In this approach, the coating is applied in a continuous and substantially complete layer so as to entirely cover a contiguous region on the surface of the substrate. In screen printing this may be done by printing a null pattern, for example in which the entire surface is printed to a predefined thickness.

Once the ink or paste has been applied by the liquid phase atmospheric pressure technique, the coated substrate is fired 18. This may convert the paste or ink to a glassy state. Examples of this firing process may apply a thirty-minute heating cycle and reach a peak of aL least 850nC for Len minutes of LhaL LhirLyminute cycle.

Once the coated substrate has been fired, one or more metal layers may be applied 20 over the coating. These layers may be applied by plating techniques, such as by electroplating. The plating may provide layers of silver, copper, and nickel. All three such -10 -materials may be applied in sequence and may comprise a non-cyanide silver plate of ASTM type II Grade A, which may have a thickness of between 0.1 thou and 2 thou. The silver may be provided over a copper sublayer of standard MIL-C-14550 of thickness 1 thou to 1.5 thou, which in turn may be provided over nickel of standard QQ-N290 and having thickness of 1 thou to 3 thou. As used herein the "thou" is a non-SI unit of length equal to 0.0254mm.

Other types of coating and other types of plating on that coating 10 may be used. Any appropriate functional material, such as material having a desired thermal, magnetic, or electrical performance may be used.

Once the substrate has been fired and coated the laser may be controlled 22 according to a digital representation of the circuitry component which is to be manufactured. Accordingly, the laser is controlled to direct laser energy to the surface of the substrate to ablate the coating layer and the metal layers to expose the substrate beneath. This may be done by applying ultra-fast pulses of laser energy -for example pulses faster than 1 nano second, for example as short as a few hundred femtoseconds. The ablation may be performed to remove material from the contiguous and continuous coating of the substrate so as to create, from that continuous layer, the circuitry elements which make up the RF component. There may be a plurality of such components which may include resistive, inductive and/or capacitive elements.

These respective circuitry components may be connected together to perform any combined function according to the design provided in the digital representation. Examples of such function include RF circulator and RF isolator functions, RF filter, RF power divider and combiner and similar functions. It will be appreciated in the context of the present disclosure that these characteristics may be achieved through the shaping of conductive tracks and conductive portions on the surface of the substrate. And by the connection, at selected locations, of these portions to a ground plane, which may be provided on the opposite surface of the substrate by the coating on the other side of the substrate. Typically, these connections are provided by the vias described above.

The computer-controlled ablation of the surface layers continues until the underlying dielectric substrate has been exposed by ablation of the layer structure. It has been found to be significant in these constructions that a degree of ablation of the underlying substrate is also provided so that the regions of the substrate which are covered by the layers are slightly thicker than those regions which have been exposed by ablation. This may help to ensure complete removal of any conductive or other functional material associated with the layers and to allow for small substrate planarity imperfections.

It has also been found that certain surface features result from this ablation action providing a ridged or grooved surface in the manor of a "ploughed field" components having these characteristics have been tested and found to achieve desirable circuitry performance as illustrated in Figure 4 and Figure 5. Such grooves may be microscopic and may not be visible to the naked eye. Typically, AFM or similar measurements may reveal their presence.

Once the desired form of the circuitry component has been achieved through ablation of the layer material by the ultra-fast laser, the substrate may be cut 24, or diced, into a plurality of tiles, each tile carrying a single one of the relevant components.

The amount of material removed in any one tile of the substrate may be at least 30, for example at least 604, for example at least 70%.

-12 -Figure 2 illustrates a circuitry component 100 manufactured according to the present disclosure. It can be seen that a single wafer 102 of substrate carries a lattice made up of a plurality of "tiles". Each tile of the lattice comprises one of the RF circuitry components fabricated according to the method described with reference to Figure 1.

This lattice of tiles may be positioned on the wafer 102 by reference to the fiducial markers which may be provided at the corners of the wafer. The inset shown in Figure 2 illustrates a single one of these tiles, in which the three ports, 102, 104, 106 of an RF circuitry component, e.g., a circulator, are shown. It can be seen that the body of the circulator 100 is made-up by a first region or land 108 of conductive material which links to each of three ports 102, 104, 106 provided at the edges of the tile.

The second inset in Figure 2 illustrates the cross section through the substrate and shows a via which has been plated as described above with reference to Figure 1 to provide a connection between the RF circuitry components shown in the tiles in Figure 2 and a ground plane which is provided by the coating/plating of the opposite surface.

Considering the illustration in Figure 2 in more detail it can be 25 seen that the RF electrical component comprises a dielectric substrate having a first major surface, and a second major surface.

A conductive thick film, provided across the entirety of that surface, has been ablated by operation of an ultra-fast laser to 30 create, from that single continuous film, the elements of RF circuitry which make-up the RF electrical component.

The individual RF component 100 (one tile of the lattice) can be seen to comprise a first region 108, in which the substrate is -13 -covered by the conductive thick film. It can be seen in Figure 1 that this first region 108 is patterned to provide RF circuitry of the RF electrical component. In particular, it provides connections to each of three ports 102, 104, 106 of the component.

The first and third port 102, 104, are on one edge of the first surface of the tile of substrate whereas the second port 106 is on an opposite edge of the tile.

The first region 108 comprises a land of material surrounded by 10 exposed substrate 110, in which the material has been ablated by operation of the laser. In these second regions 110 the bare substrate is exposed.

The regions of the substrate beneath the thick film 108 are thicker 15 than the substrate in the exposed second regions 110. Although not visible in Figure 2, the first regions 108 are bounded by a step in the surface of the substrate. The edge of the step coincides with the edge of the conductive thick film.

The second regions 110 may also be marked with grooves, in the surface of the substrate, which have been ablated by the laser. These grooves may be microscopic and may follow straight lines across the surface of the second region. One or more of these straight lines may be aligned with a straight edge of the first region. In some embodiments, rather than being straight, these grooves may follow a path which is parallel to the edge of the second regions.

Typically, whether straight or not, these grooves extend across 30 the entirety of the second regions.

Figure 3 shows a flow chart indicating a computer implemented method for fabricating an ensemble of mutually similar RF electrical components according to the present disclosure. This -14 -method may be implemented by an apparatus such as that illustrated in Figure 4 which comprises a computer control, referred to herein as a controller and a fabrication apparatus comprising coating capability and laser ablation capability. Such capabilities may be provided by an ultra-fast femto-second laser such as an Optek MM2500, available from OPTEK Systems of Abingdon, Oxford, UK. It may also comprise a coating/plating capability for coating and plating substrate as described above. As an alternative, the fabrication capability may be provided with one or more 10 precoated/plated substrates upon which the methods of the present application are to be performed.

The method illustrated in Figure 3 proceeds as follows: First, a digital representation of an RF circuit component is obtained 312. This digital representation may provide a spatial map of the functional elements which are to make-up the RF circuit component and/or the regions of the coated layer which are to be ablated from the substrate. Typically, this digital representation of an RF circuit component is designed to provide a particular RF performance parameter such as insertion loss, an S parameter, a transfer function or similar but the types of RF circuitry performance parameters will be appreciated by the skilled addressee in the context of the present disclosure.

The computer then uses 314 the digital representation to control the laser to ablate the thick layer from the substrate. By this process of ablation, the computer uses the laser to replicate, on the physical substrate, the arrangement of circuitry components represented in the digital representation.

Once the coating has been ablated appropriately (and the wafer has been diced if necessary to isolate an individual circuit component from the lattice) the RF circuit component is tested 316 to -15 -determine whether it matches the RF performance characteristic for which the digital representation was designed.

The results of the testing 316 may then be used to adapt the digital 5 representation. For example, it may be used to change 318 the spatial configuration (as represented in the digital representation) of one or more elements of the conductive material in the first regions on the surface of the substrate of the component. For example, the digital representation may be changed 10 to trim or otherwise to adjust one or more circuitry components based on the testing data.

These adjustments may be based on computer simulations and/or other considerations associated with the relevant RF performance.

The computer then operates the laser to create 318 a further RF circuit component according to the revised digital representation. This new component is then diced from the wafer and tested 320 as described above to determine the relevant RF performance characteristics.

In the event that the component matches 322 the desired RF performance characteristic the method ends.

In the event that the RF performance characteristic does not match 322 the desired performance then the digital representation can be further adjusted 318, for example to change the configuration of conductors on the substrate.

A further new RF circuit component can then be manufactured 318 by operation of the laser by the computer and the process of testing, amending the digital representation, creating a new component, testing the component, and then further amending the digital representation, if necessary, can be repeated iteratively until -16 -the method converges upon a desired performance characteristic for the RF circuit component.

It will be appreciated in the context of the present disclosure that such rapid steps of fabrication, testing, redesign, remanufacture, and retesting are simply not possible in prior art thin film methods. The present disclosure therefore provides a rapid "CAD to FAB" technique by which RF components can be designed and optimised.

It will further be appreciated that the result of carrying out such a method is to create an ensemble 324 of mutually similar RF circuit components, each having a performance characteristic which approximates the desired performance characteristic, but which converge in a sequence upon the desired characteristic. This ensemble of RF circuit components 324 is illustrated in Figure 3.

It will be appreciated from the discussion above that the embodiments shown in the Figures are merely exemplary, and include features which may be generalised, removed or replaced as described herein and as set out in the claims. With reference to the drawings in general, it will be appreciated that schematic functional block diagrams are used to indicate functionality of systems and apparatus described herein. It will be appreciated however that the functionality need not be divided in this way, and should not be taken to imply any particular structure of hardware other than that described and claimed below. The function of one or more of the elements shown in the drawings may be further subdivided, and/or distributed throughout apparatus of the disclosure. In some embodiments the function of one or more elements shown in the drawings may be integrated into a single functional unit.

In some examples the functionality of the controller may be provided by a general purpose processor, which may be configured -17 -to perform a method according to any one of those described herein. In some examples the controller may comprise digital logic, such as field programmable gate arrays, FPGA, application specific integrated circuits, ASIC, a digital signal processor, DSP, or by any other appropriate hardware. In some examples, one or more memory elements can store data and/or program instructions used to implement the operations described herein. Embodiments of the disclosure provide tangible, non-transitory storage media comprising program instructions operable to program a processor to perform any one or more of the methods described and/or claimed herein and/or to provide data processing apparatus as described and/or claimed herein. The controller may comprise an analogue control circuit which provides at least a part of this control functionality. An embodiment provides an analogue control circuit configured to perform any one or more of the methods described herein.

The above embodiments are to be understood as illustrative examples. Further embodiments are envisaged. For example, the tiles of substrate have been shown and described as being square but other shapes may be used. In addition, particular sizes of substrate tiles have been mentioned but other sizes can be used. The methods of the present disclosure are particularly advantageous in the fabrication of RF components in high RF frequency ranges, such as more than 1 GHz. Particular benefits become apparent in the range of frequencies of about 3 GHz and above because of the high spatial precision that this method of manufacture offers combined with the ability to use functional thick film of any chosen characteristic. The method is also able to perform short runs at high accuracy for low cost and then to adapt and update the component design without any need for a mask.

It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other -18 -features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without 5 departing from the scope of the invention, which is defined in the accompanying claims.

Claims

-19 -Claims 1. A method of manufacturing a radio frequency, RF, circuitry component, the method comprising: providing a dielectric substrate; coating a first surface of the dielectric substrate with a firsl layer of material Lo cover a contiguous region of Lhe surface into which the circuitry component is to be inscribed, wherein the coating is performed by an atmospheric pressure process; operating a laser to ablate material from the layer within the region to create the circuitry component, wherein the circuitry component is adapted for radio frequency, RF, electrical signals.
2. The method of claim 1 wherein the laser is an ultrafast laser, such as a laser emitting light pulses each shorter than 1 nanosecond.
3. The method of claim 1 wherein the layer is a thick film.
4. The method of any preceding claim wherein, prior to ablation, the layer covers substantially all of the region and, after ablation, at least 30% of the region has been removed, for example at least 50%, for example at least 70%.
5. The method of any preceding claim wherein the circuitry component is provided entirely within the region.
6. The method of any preceding claim wherein coating the first surface comprises an atmospheric pressure liquid phase deposition 30 technique, for example printing, spin coating, knife-edge coating, or direct writing.
7. The method of any preceding claim wherein the circuitry component is adapted for radio frequency, RF, electrical signals -20 -having a frequency greater than 1 GHz, for example at least 2 GHz, for example less than 170 GHz.
R. The method of any preceding claim wherein the circuitry component is configured to operate in an average power range of at least lmW, for example less than lkW.
9. The method of any preceding claim wherein the substrate comprises at least one through-hole and the method comprises 10 coating the through-hole to provide a coated via.
10. The method of claim 9 wherein the method further comprises ablating the substate using the laser to provide the through-hole.
11. The method of claim 9 or 10 wherein the substrate comprises a second surface, opposite the first surface and the method comprises coating the second surface to provide a second layer.
12. The method of claim 11 wherein the first layer is connected 20 to the second layer by the via.
13. The method of any preceding claim wherein the coating comprises a functional material having at least one function selected from the list comprising electrical conductivity, electrical resistivity a ferroelectric property and a thermal conductivity.
14. The method of any preceding claim wherein the material comprises at least one of gold and silver.
15. The method of any preceding claim wherein the material comprises palladium and silver.
-21 - 16. The method of any preceding claim wherein the substrate comprises at least one of ferrite, alumina, barium titanate, and diamond.
17. An RF electrical component comprising: a dielectric substrate having a first surface and the RF electrical component further comprising a thick film arranged to provide RF circuitry; wherein a first surface of the substrate comprises: first regions, in which the substrate is covered by the conductive thick film and which are arranged in a pattern to provide RF circuitry of the RF electrical component, second regions, in which the bare substrate is exposed, wherein the first regions of the substrate are thicker than the second regions.
18. The RF electrical component of claim 17 wherein the first regions are bounded by a step in the surface of the substrate.
19. The RF electrical component of claim 17 or 18 wherein the second regions comprise a plurality of grooves in the surface of the substrate.
20. The RF electrical component of claim 19 wherein the grooves 25 are aligned parallel with each other.
21. The RF electrical component of claim 20 wherein the grooves are straight.
22. The RF electrical component of claim 20 wherein the grooves follow a path parallel to a bounding edge of the second regions.
23. The RF electrical component of claim 20, 21 or 22 wherein the grooves extend across an entire length of the second regions.
-22 - 24. The RF electrical component of any of claims 17 to 23 wherein the substrate comprises at least one of ferrite, alumina, barium titanate, and diamond.
25. The RF electrical component of any of claims 17 to 24 wherein the RF circuitry is adapted for radio frequency, RF, electrical signals having a frequency greater than 1 GHz, for example at least 2 GHz, for example less than 170 GHz.
26. The RF electrical component of any of claims 17 to 25 wherein the RF circuitry is configured to operate in an average power range of at least lmW, for example less than lkW.
27. The RF electrical component of any of claims 17 to 26 wherein the substrate comprises at least one through-hole coated with a material of the thick film to provide a coated via.
28. The RF electrical component of any of claims 17 to 27 wherein 20 the substrate comprises a second surface, opposite the first surface and the method comprises coating the second surface to provide a second layer.
29. The RF electrical component of claim 28 wherein the first 25 layer is connected to the second layer by the via.
30. An ensemble of RF electrical components comprising a plurality of RF electrical components according to any of claims 17 to 29, wherein each of the RF electrical components have the same 30 input and output connections and are each arranged to provide the same function, and the function has a particular characteristic, wherein the characteristic of each of the RF electrical components is different from all of the others such that the ensemble together provides a -23 -set of RF electrical components in which characteristic of the members of the set each approximate a desired RF characteristic of the circuitry component.
31. A computer-controlled fabrication apparatus comprising: an ultrafast laser for ablating the thick film; a laser ablation control element for controlling the delivery of laser energy to a surface of a substrate at a selected location for the ablation of the thick film from the substrate at that 10 location; and a controller, coupled to the laser ablation control element, and configured to: (i) obtain a first digital representation of a circuitry component; (ii) operate the laser, based on the digital representation to ablate material from the thick film of a first substrate to create a circuitry component on the first substrate; (iii) obtain, based on the first digital representation and test data indicating an RF characteristic of the created circuitry component, a revised digital representation; (iv) operate the laser, based on the revised digital representation to ablate material from the thick film of a second substrate to create a revised circuitry component on the second substrate; and (v) to repeat steps (iii) and (iv) until the test data indicates that the created circuitry component matches a desired RF characteristic of the circuitry component.