Method for manufacturing a polymer-based frequency component

Abstract

The disclosure relates to a method for manufacturing a polymer-based frequency component for a radio frequency device with through-holes. The method comprises: providing a first polymer foil with a pattern of blind holes at a topside of the first polymer foil; disposing and planarizing uncured polymer onto the topside, the uncured polymer infiltrating the blind holes and covering the topside; curing the planarized uncured polymer to obtain a second polymer foil comprising a cured polymer structure corresponding to the pattern of blind holes; removing excess polymer from the second polymer foil; placing a releasable structure on the topside of the first polymer foil, the releasable structure being configured to bond to the cured polymer structure and to release the cured polymer structure from the first polymer foil; metal coating the releasable structure to obtain a fully or partially metallized polymer membrane with a pattern of through holes; and releasing the metallized polymer membrane from the first polymer foil to obtain the polymer-based frequency component with the through-holes.

Description

[0001] METHOD FOR MANUFACTUR ING A POLYMER-BASED FREQUENCY COMPONENT

[0002] TECHNICAL FIELD

[0003] The disclosure relates to the field of microwave structures such as filters, antennas, beam forming networks and orthomode transducers, and methods for their production. The disclosure further relates to manufacturing and assembly of single- and multiple-layer trough-hole metal-coated membranes with replica molding (REM) process for radio frequency (RF) applications up to sub-THz frequencies.

[0004] BACKGROUND

[0005] The manufactory of mmW and sub-THz components for emerging applications in 5G and beyond 5G scenario is of primary importance. The higher the frequency of operation of RF components, the smaller the wavelength and the features size. Current processes are inaccurate or are too expensive to be involved in competitive mass production.

[0006] SUMMARY

[0007] This disclosure provides a solution for manufacture of frequency components for RF devices, in particular microwave structures, with extremely small features, through holes, high accuracy (few pm) and good reliability. The disclosure particularly presents a high accuracy process based on low-cost materials and a novel manufactory technique that ensures high yield and low production costs.

[0008] The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

[0009] Embodiments of the disclosure present techniques for the following: Manufacturing of macro structure (cm-size, e.g., BFN) with micrometric accuracy; Multiple-layer membranes with different features of variable size (in-plane sizes); Single-layer through-hole membrane with different features of variable size (in-plane sizes); Multiple-layer through-hole membrane with different features of variable size (out-of-plane thicknesses and in-plane sizes); Single- and double-layer through-hole membrane metal coating (full / partial); Multi-membranes structure alignment, stacking, and bonding without losing form factor; and Manufactory of structure with aspect ratio >1:10 (e.g. cavity wall of cavity or wedge of 447.6 um of length and 33.7 um width).

[0010] Embodiments of the disclosure present a new process for the manufactory of microwave structures (e.g., filters, antennas, Beam Forming Networks, Orthomode Transducer) for a single layer or multi-layer device with through-hole apertures for whatever frequency (including RF applications up to sub-THz frequencies).

[0011] This new process mimics a technology used for chemical and biological application and hence represents simple and reliable procedures. All the machine and technology employed in this process are standard thereby implementing a simple and standard process. All requirements in terms of surface roughness and feature accuracy can be satisfied, guaranteeing improved performance. Usage of PDMS (Polydimethylsiloxane) and other low-cost and easy-procurement polymers as sacrificial material allow to avoid usage of metal layer and Silicon Wafer which results in extremely low costs. Multiple usage of SU-8 Positive Master and PDMS negative mold to produce positive antenna slabs in PDMS allow to produce devices at reduced costs. The process disclosed herein guarantees very uniform electrical contact across the full slab surface thanks to slabs flexibility, low surface roughness obtained with replica molding process, and to bonding technique with low temperature metal nanoparticles ink. Usage of on-demand release tape allows to handle and release flexible slabs with fixed features shape.

[0012] Embodiments of the disclosure present a microwave passive device with either single slab or a stack of multiple slabs (where at least one is through-hole), realized with polymer suitable for Replica Molding, partially or completely metalized. A slab is a thin layer of material.

[0013] Embodiments of the disclosure present single or multiple through-hole flexible slabs obtained by dry etching. Embodiments of the disclosure present handling and selective or complete metallization of flexible slabs obtained with on-demand release tape and metal coating via sputtering. Embodiments of the disclosure present assembling of two or more slabs stacked into an ad- hoc frame with alignment structures and bonded one to the other through a conductive adhesive ink deposited onto the slab surface.

[0014] In order to describe the disclosure in detail, the following terms and notations will be used.

[0015] REM Replica Molding

[0016] RF Radio Frequency

[0017] PDMS Polydimethylsiloxane

[0018] RIE Reactive Ion Etching

[0019] PET Polyethylene terephthalate

[0020] UV ultraviolet

[0021] In this disclosure, replica molding is described. Replica Molding (REM) is a soft-lithography technique allowing single-step replication of three-dimensional micro and nano-topologies using pliable raw materials. This technique is usually used for biological and chemical applications. In this disclosure, a novel technique of sub-THz components totally manufactured with through-hole layers fabricated with the REM process and stacked together is presented.

[0022] According to a first aspect, the disclosure relates to a method for manufacturing a polymer-based frequency component for a radio frequency device with through-holes, the method comprising: providing a first polymer foil having a topside and a backside opposite to the topside, the first polymer foil comprising a pattern of blind holes at the topside; disposing and planarizing uncured polymer onto the topside of the first polymer foil, the uncured polymer infiltrating the blind holes and covering the topside of the first polymer foil; curing the planarized uncured polymer to obtain a second polymer foil comprising a cured polymer structure corresponding to the pattern of blind holes; removing excess polymer from the second polymer foil down to the topside of the first polymer foil without removing polymer from the blind holes of the first polymer foil to obtain the first polymer foil with the cured polymer structure arranged in the blind holes; placing a releasable structure on the topside of the first polymer foil, the releasable structure being configured to bond to the cured polymer structure and to release the cured polymer structure from the first polymer foil; metal coating the releasable structure with the bonded cured polymer structure to obtain a fully or partially metallized polymer membrane with a pattern of through holes; and releasing the metallized polymer membrane from the first polymer foil to obtain the polymer-based frequency component with the through-holes.

[0023] Such a method can be used for manufacture of frequency components for RF devices, in particular microwave structures, with extremely small features, through holes, high accuracy down to a range of a few pm and good reliability. The method represents a high accuracy process based on low-cost materials and a novel manufactory technique that ensures high yield and low production costs. The polymer-based frequency component can be a component of any frequency, e.g., a radio frequency component, a sub-THz component or an optical component. Polymer-based means that a main body or structure of the frequency component may be formed of a polymer material.

[0024] The releasable structure can be a releasable tape or a releasable surface of any layer or any object, for example.

[0025] Metallized through holes include metallization of the walls of the holes which may be usually required for RF components.

[0026] In an exemplary implementation of the method, the releasable structure comprises a tape that is releasable by thermal activation or by UV activation.

[0027] Such a tape is releasable upon demand. Release of the tape can be easily activated by thermal activation such as applying heat or by applying UV radiation to the tape.

[0028] In an exemplary implementation of the method, the first polymer foil comprises a cured polymer, functionalized to obtain a hydrophobic surface.

[0029] By such hydrophobic surface, no liquids will remain at the surface when the first polymer foil is disposed with uncured polymer.

[0030] The cured polymer may be for example PDMS (Poly dimethylsiloxane). The functionalization of the cured polymer may be for example a functionalization with Trichloro (1H,1H,2H,2H perfluoro octyl) silane.

[0031] In an exemplary implementation of the method, the first polymer foil is manufactured via Replica Molding, REM, of a positive resist master, thereby obtaining a negative replica of the positive resist master.

[0032] This allows easy production of the first polymer foil.

[0033] The resist master may comprise an SU8 master for example. Other suitable materials for the resist master can be used as well.

[0034] In an exemplary implementation of the method, the uncured polymer comprises a prepolymer. The prepolymer may be, for example, PDMS (Poly dimethylsiloxane).

[0035] Prepolymers are the precursors of polymers. It is a molecule made up of several building blocks that is not yet the size of a polymer. The prepolymer is usually a collective term for reactive oligomers from which polymers are made. They are preliminary products that, in contrast to the end product, can still be soluble or meltable.

[0036] In an exemplary implementation of the method, planarizing the uncured polymer comprises: placing a functionalized PET foil over the uncured polymer; sandwiching the first polymer foil with the uncured polymer and the functionalized PET foil between two rigid plates; and applying pressure onto one or both of the two rigid plates.

[0037] This production method ensures optimal planarization with minimal roughness.

[0038] In an exemplary implementation of the method, removing the excess polymer from the second polymer foil comprises dry etching in a plasma of O2 : C E i. By such dry etching, a through-hole membrane can be obtained.

[0039] In an exemplary implementation of the method, metal coating the polymer membrane with the pattern of through holes comprises Al or Ag sputtering deposition by DC magnetron sputtering.

[0040] This kind of metal coating ensures uniform coating of all surfaces with a metal film without any deformation of the polymer membrane.

[0041] In an exemplary implementation of the method, the polymer-based frequency component comprises a topside opposite to the releasable structure and a backside facing the releasable structure; wherein the method comprises: placing a second releasable structure on the topside of the polymer-based frequency component; releasing the releasable structure from the backside of the polymer-based frequency component; and metal coating the polymer-based frequency component to obtain a fully metal coated polymer-based frequency component.

[0042] By applying such second releasable structure metallization of the whole frequency component can be easily achieved.

[0043] In an exemplary implementation of the method, the releasable structure and the second releasable structure are releasable by thermal activation or by UV activation; and wherein both structures have different thermal activation temperatures; or one of the two structures is releasable by thermal activation and the other one of the two structures is releasable by UV activation.

[0044] This allows different activation conditions for the two structures. They will not release at the same time. Handling of the device can be efficiently controlled by controlling the thermal or UV activation.

[0045] In an exemplary implementation of the method, the method comprises: assembling multiple of the polymer-based frequency components into a monolithic device by bonding each polymer-based frequency component to the other by using a conductive ink or eutectic solder paste.

[0046] This process allows easy production of a whole monolithic device from stacked frequency components.

[0047] In an exemplary implementation of the method, the method comprises: aligning each polymer-based frequency component to the successive one by placing the multiple polymer-based frequency components onto an alignment frame.

[0048] This allows exact dimensioning of the monolithic device resulting in accurate radiating performance of the device.

[0049] In an exemplary implementation of the method, the alignment frame comprises one or more pillars which are paired with dedicated through holes of the polymer-based frequency components.

[0050] By such pillars, stacking can be exactly performed without undesired irregularities.

[0051] In an exemplary implementation of the method, the method comprises: placing a cover frame onto the multiple polymer-based frequency components placed above each other to keep the multiple polymer-based frequency components in contact with one another during the bonding.

[0052] By such cover plane, bonding can be easily and exactly implemented. In an exemplary implementation of the method, the releasable structure is configured to release the cured polymer structure from the first polymer foil without any mechanical deformations; and wherein by releasing the metallized polymer membrane from the first polymer foil the metallized polymer membrane is obtained without any mechanical deformations.

[0053] The usage of a release structure such as a release tape enables to handle the polymer foil (with or without through holes) ensuring no mechanical deformation.

[0054] According to a second aspect, the disclosure relates to a polymer-based frequency component, obtainable by the method for manufacturing a polymer-based frequency component according to the first aspect.

[0055] The method as described above allows efficient production of such polymer-based frequency components. Frequency components for RF devices, in particular microwave structures, with extremely small features, through holes and high accuracy down to a range of a few pm and good reliability can be produced by such method. The polymer-based frequency components can be produced in a high accuracy process based on low-cost materials enabling high yield and low production costs.

[0056] According to a third aspect, the disclosure relates to a monolithic device, obtainable by the method for manufacturing a polymer-based frequency component according to the first aspect.

[0057] Monolithic devices with extremely small features, through holes, high accuracy and good reliability can be efficiently provided. The monolithic devices can have a high accuracy at low production costs.

[0058] In an exemplary implementation of the monolithic device, the monolithic device is forming a microwave antenna, a microwave filter, a beam forming network or an orthomode transducer.

[0059] A lot of different monolithic devices as listed above can be produced by such method as described above.

[0060] BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Further embodiments of the disclosure will be described with respect to the following figures, in which:

[0062] Figure 1 shows a schematic diagram of a method 100 for manufacturing a polymer-based frequency component 150 for a radio frequency device with through-holes according to the disclosure;

[0063] Figure 2 shows an exemplary workflow 200 for manufacturing positive through-hole membranes;

[0064] Figure 3 shows an exemplary workflow 300 for metal coating free-to-move through-hole membranes; and

[0065] Figure 4 shows an exemplary workflow 400 for assembling metal-coated PDMS through-hole membranes.

[0066] DETAILED DESCRIPTION OF EMBODIMENTS

[0067] In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific aspects in which the disclosure may be practiced. It is understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the disclosure is defined by the appended claims.

[0068] It is understood that comments made in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise.

[0069] Figure 1 shows a schematic diagram of a method 100 for manufacturing a polymer-based frequency component 150 for a radio frequency device with through-holes according to the disclosure.

[0070] Figure 1 also reports the workflow to produce devices based on single / multi-layer trough-hole metal-coated membranes. In this scheme the first steps 1 to 4, corresponding to blocks 11, 12, 13, 14 represent positive hard master manufacturing, including the following activities: providing I l a substrate; One or more photoresist spin coating (e.g. of an exemplary thickness of 235pm), levelling, and thermal baking 12; One or more photoresist photolithography 13; Photoresist developing 14 and photoresist surface functionalization (e.g., Ethanolamine + Trichloro(lH,lH,2H,2H-perfluoro-octyl) silane). For obtaining double SU-8 deposition 13f, the above blocks 12 and 13 corresponding to steps 2 and 3 can be repeated multiple times.

[0071] Positive hard masters can be manufactured, for example, with a single or double layer of SU-8 photoresist over a 3” silicon wafer, by one or two aligned photolithographies and a final developing step 14. After the fabrication, the positive masters can be functionalized with Trichloro(lH,lH,2H,2H-perfluoro-octyl) silane to obtain a hydrophobic SU-8 surface facilitating the subsequent replica molding process.

[0072] The next steps 5 and 6 corresponding to blocks 15 and 101 represent: negative soft master manufacturing, including the following activities: Drop casting at room temperature of PDMS prepolymer on positive hard master (an exemplary thickness of 2:5mm can be applied); Degassing, levelling, and thermal curing of PDMS prepolymer as shown in block 15; Dry peeling- off and resizing of cured PDMS; and Surface functionalization of PDMS negative soft master (i.e., O2 plasma + Trichloro(lH,lH,2H,2H-perfluoro-octyl)silane) as shown in block 101.

[0073] Negative soft masters can be manufactured via REM of positive hard master using PDMS. PDMS prepolymer can be mixed, degassed, drop casted, levelled, thermally cured, and peeled-off to obtain a negative replica of the starting SU-8 masters. After the fabrication, the negative masters can be functionalized with Trichloro(lH,lH,2H,2H-perfluoro-octyl) silane to obtain an hydrophobic PDMS surface facilitating the successive replica molding process.

[0074] SU-8 photoresist is an epoxy-based negative photoresist. It has parts that crosslink when exposed to ultraviolet light and the remaining is soluble. The remaining portion can be washed away during the development process. SU-8 photoresist has good mechanical, dielectric, chemical resistant and thermal properties, and good biocompatibility. It can be used for fabrication of microfluidic chip for cell culture, molecular diagnostics etc. In this disclosure, it can be used for fabrication of frequency components for RF devices. SU-8 can be used as a mold for PDMS soft lithography frequency component fabrication as presented in this disclosure.

[0075] These steps 1 to 6 as described above can be represented by the following activity: providing 101 a first polymer foil 110 having a topside 110a and a backside 110b opposite to the topside 110a, the first polymer foil 110 comprising a pattern of blind holes 111 at the topside 110a. The steps 7 to 10 corresponding to blocks 102 to 105 represent positive through-hole membrane manufacturing including the following activities: PET foil surface functionalization (e.g., by O2 plasma + Trichloro(l H,1 H,2H,2H-perfluoro-octyl)silane); Drop casting at room temperature of PDMS prepolymer on negative soft master; Degassing, sandwiching with functionalized PET foil, and thermal curing of PDMS prepolymer as shown by block 102; Dry etching with CF4-O2 plasma, for example, of PDMS excess in through-hole features as shown by blocks 103 and 104; Peeling off and handling of PDMS membranes with tapes with on-demand release mechanism, as shown by block 105.

[0076] These steps 7 to 10 as described above can be represented by the following activities:

[0077] Disposing and planarizing 102 uncured polymer 121 onto the topside 110a of the first polymer foil 110, the uncured polymer 121 infiltrating the blind holes 111 and covering the topside 110a of the first polymer foil 110 as shown in block 102 corresponding to step 7;

[0078] Curing 102 the planarized uncured polymer 121 to obtain a second polymer foil 120 comprising a cured polymer structure 122 corresponding to the pattern of blind holes 111 as also shown in block 102 corresponding to step 7;

[0079] Removing 103 excess polymer from the second polymer foil 120 down to the topside 110a of the first polymer foil 110 without removing polymer from the blind holes 111 of the first polymer foil 110 to obtain the first polymer foil 110 with the cured polymer structure 122 arranged in the blind holes 111 as shown in block 103 corresponding to step 8;

[0080] Placing 104 a releasable structure 130 on the topside 110a of the first polymer foil 110, the releasable structure 130 being configured to bond to the cured polymer structure 122 and to release the cured polymer structure 122 from the first polymer foil 110 as shown in block 104 corresponding to step 9.

[0081] Step 11 corresponding to block 106 represents Through-hole membrane metal coating, including the following activities: Double-face conformal metal coating of through-hole PDMS membranes via double-step sputtering deposition using a handling tape with different on-demand release temperatures / mechanisms.

[0082] Step 11 can be represented by the following activity: metal coating 106 the releasable structure 130 with the bonded cured polymer structure to obtain a fully or partially metallized polymer membrane 140 with a pattern of through holes 141.

[0083] Step 12 corresponding to block 107 represents Multi-membrane stacking, aligning, and bonding, including the activity: Multimembrane stacking using an alignment frame and low temperature bonding through micro-contact printing of conductive ink between adjacent membranes. The slabs or polymer-based frequency components 150, respectively, can be stacked as schematically shown by block 106f.

[0084] Step 12 can be represented by the following activity: assembling multiple of the polymer-based frequency components 150 into a monolithic device 420 by bonding each polymer-based frequency component 150 to the other by using a conductive ink or eutectic solder paste.

[0085] Figure 1 thus represents a method 100 for manufacturing a polymer-based frequency component 150 for a radio frequency device with through-holes according to the disclosure.

[0086] The method 100 comprises: providing 101 a first polymer foil 110 having a topside 110a and a backside 110b opposite to the topside 110a, the first polymer foil 110 comprising a pattern of blind holes 111 at the topside 110a. This providing 101 may include the steps 1 to 6 as described above which may be applied to provide the first polymer foil 110 with the pattern of blind holes 111 at the topside 110a.

[0087] The method 100 comprises: disposing and planarizing 102 uncured polymer 121 onto the topside 110a of the first polymer foil 110, the uncured polymer 121 infiltrating the blind holes 111 and covering the topside 110a of the first polymer foil 110 as shown in block 102 corresponding to step 7.

[0088] The method 100 comprises: curing 102 the planarized uncured polymer 121 to obtain a second polymer foil 120 comprising a cured polymer structure 122 corresponding to the pattern of blind holes 111 as also shown in block 102 corresponding to step 7.

[0089] The method 100 comprises: removing 103 excess polymer from the second polymer foil 120 down to the topside 110a of the first polymer foil 110 without removing polymer from the blind holes 111 of the first polymer foil 110 to obtain the first polymer foil 110 with the cured polymer structure 122 arranged in the blind holes 111 as shown in block 103 corresponding to step 8.

[0090] The method 100 comprises: placing 104 a releasable structure 130 on the topside 110a of the first polymer foil 110, the releasable structure 130 being configured to bond to the cured polymer structure 122 and to release the cured polymer structure 122 from the first polymer foil 110 as shown in block 104 corresponding to step 9.

[0091] The method 100 comprises: metal coating 106 the releasable structure 130 with the bonded cured polymer structure to obtain a fully or partially metallized polymer membrane 140 with a pattern of through holes 141 as shown in block 106 corresponding to step 11.

[0092] The method 100 comprises: releasing 105 the metallized polymer membrane 140 from the first polymer foil 110 to obtain the polymer-based frequency component 150 with the through-holes as shown in block 105 corresponding to step 10.

[0093] Steps 7 to 10 corresponding to blocks 102 to 105 are further described below with respect to Figure 2. Step 11 is further described below with respect to Figure 3. Step 12 is further described below with respect to Figure 4.

[0094] The polymer-based frequency component as described above can be a component of any frequency, e.g., a radio frequency component, a sub-THz component or an optical component. Polymer-based means that a main body or structure of the frequency component may be formed of a polymer material.

[0095] The releasable structure can be a releasable tape or a releasable surface of any layer or any object, for example.

[0096] Metallized through holes include metallization of the walls of the holes which may be usually required for RF components.

[0097] The releasable structure 130 may comprise a tape that is releasable by thermal activation or by UV activation.

[0098] The first polymer foil 110 may comprise a cured polymer, functionalized to obtain a hydrophobic surface.

[0099] The cured polymer may be for example PDMS (Poly dimethylsiloxane). The functionalization of the cured polymer may be for example a functionalization with Trichloro (1H,1H,2H,2H perfluoro octyl) silane. The first polymer foil 110 can be manufactured via Replica Molding (REM) of a positive resist master, thereby obtaining a negative replica of the positive resist master.

[0100] The resist master may comprise an SU8 master for example. Other suitable materials for the resist master can be used as well.

[0101] The uncured polymer 121 may comprise a prepolymer, for example. The prepolymer may be, for example, PDMS (Poly dimethylsiloxane).

[0102] Planarizing 102b the uncured polymer 121 as described above may comprise: placing a functionalized PET foil 223 over the uncured polymer 121 as shown in Figure 2: sandwiching the first polymer foil 110 with the uncured polymer 121 and the functionalized PET foil 223 between two rigid plates 222, 223: and applying pressure 225 onto one or both of the two rigid plates 222, 223 as shown in Figure 2.

[0103] Removing 103 the excess polymer from the second polymer foil 120 may comprise dry etching in a plasma of O2:CF4, for example.

[0104] Metal coating 106 the polymer membrane 140 with the pattern of through holes 141 may comprise Al or Ag sputtering deposition by DC magnetron sputtering, for example.

[0105] The polymer-based frequency component 150 comprises a topside 150a opposite to the releasable structure 130 and a backside 150b facing the releasable structure 130 as shown in Figure 3.

[0106] The method 100 may further comprise: Placing a second releasable structure 131 on the topside 150a of the polymer-based frequency component 150; Releasing the releasable structure 130 from the backside 150b of the polymer-based frequency component 150; and Metal coating the polymer-based frequency component 150 to obtain a fully metal coated polymer-based frequency component as shown in Figure 3.

[0107] The releasable structure 130 and the second releasable structure 131 may be releasable by thermal activation or by UV activation. Both structures 130, 131 can have different thermal activation temperatures; or one of the two structures 130, 131 may be releasable by thermal activation and the other one of the two structures 130, 131 may be releasable by UV activation.

[0108] The method 100 may further comprise: assembling multiple of the polymer-based frequency components 150 into a monolithic device 420 by bonding each polymer-based frequency component 150 to the other by using a conductive ink or eutectic solder paste as shown in Figure 4, for example.

[0109] The method 100 may comprise: aligning each polymer-based frequency component 150 to the successive one by placing the multiple polymer-based frequency components 150 onto an alignment frame 410 as shown in Figure 4.

[0110] The alignment frame 410 may comprise one or more pillars 411 which are paired with dedicated through holes 412 of the polymer-based frequency components 150 as shown in Figure 4.

[0111] The method 100 may further comprise: placing a cover frame 413 onto the multiple polymer-based frequency components 150 placed above each other to keep the multiple polymer-based frequency components 150 in contact with one another during the bonding as shown in Figure 4. The releasable structure 130 may be configured to release the cured polymer structure 122 from the first polymer foil 110 without any mechanical deformations.

[0112] By releasing 105 the metallized polymer membrane 140 from the first polymer foil 110 the metallized polymer membrane 140 is obtained without any mechanical deformations.

[0113] The usage of a release structure such as a release tape enables to handle the polymer foil (with or without through holes) ensuring no mechanical deformation.

[0114] A polymer-based frequency component 150 as shown in Figure 1 can be obtained by the method 100 for manufacturing a polymer-based frequency component 150 as described above with respect to Figure 1.

[0115] A monolithic device 420 as shown in Figure 4, for example, can be obtained by the method 100 for manufacturing a polymer- based frequency component 150 as described above with respect to Figure 1.

[0116] Such a monolithic device 420 can form or implement a microwave antenna, a microwave filter, a beam forming network or an orthomode transducer or other suitable devices, for example.

[0117] Figure 2 shows an exemplary workflow 200 for manufacturing positive through-hole membranes.

[0118] The workflow 200 includes the following activities: 1. (201) PDMS negative master fabrication; 2. (202) Drop casting of uncured PDMS; 3. (203) Application of top PET foil; 4. (204) Sandwiching of the glass - PET foil -uncured PDMS - negative PDMS master structure; 5. (205) Application of a pressure and thermal curing; 6. (206) Unpackaging of the PDMS replica - PDMS master; 7. (207) Dry etching of parasitic PDMS film; 8. (208) Cleaning in EtOEI to remove PDMS dust; 9. (209) Positioning of the thermal release tape; and 10. (210) Peeling-off.

[0119] PET foils can be oxidized in plasma O? and functionalized with Trichloro(lEI,lEI,2EI,2EI-perfluoro-octyl) silane to obtain a hydrophobic surface. PDMS negative masters 110 (see activity 201) can be filled with PDMS prepolymer 121 (see activity 202), degassed to avoid formation of air bubbles, and sandwiched using functionalized PET foils 223, 224 in contact with liquid PDMS and two rigid plates 221, 222 to ensure optimal planarization with minimal roughness (see activities 203, 204, 205). The sandwich can be thermally cured to obtain PDMS polymerization (see activity 205). After cooling down, the PET foil can be peeled off obtaining a PDMS positive membrane encapsulated inside the negative PDMS soft master (see activity 206). To achieve a through-hole membrane, the top parasitic PDMS layer remaining on top of the PDMS membrane (below the PET foil) can be dry etched in a plasma of CUCF i (see activity 207). PDMS dust residues on the surface at the end of the etching process can be removed washing the sample in a low surface-tension liquid, then dried (see activity 208). A tape with on- demand release mechanism (e.g., thermal, UV, etc.) can be placed on top of the plasma-etched PDMS positive membrane encapsulated inside the negative PDMS soft master (see activity 209) and can be used to peel-off achieving the PDMS (though- hole) membrane from the master ensuring a free-from-deformation approach (see activity 210).

[0120] Planarizing 102b the uncured polymer 121 as described for the method 100 above with respect to Figure 1 may comprise: placing a functionalized PET foil 223 over the uncured polymer 121 as shown in Figure 2; sandwiching the first polymer foil 110 with the uncured polymer 121 and the functionalized PET foil 223 between two rigid plates 222, 223 ; and applying pressure 225 onto one or both of the two rigid plates 222, 223 as shown in Figure 2.

[0121] Figure 3 shows an exemplary workflow 300 for metal coating free-to-move through-hole membranes. The workflow 300 includes a first part 301 comprising: Conformal metal coating via DC magnetron sputtering; a second part 302 comprising: Transfer to another thermal release tape; a third part 303 comprising: Release from the lower temperature thermal release tape; and a fourth part 304 comprising: Conformal metal coating via DC magnetron sputtering.

[0122] The following description is referring to step 11 of the process (or method 100) as described above with respect to Figure 1.

[0123] Conformal metallization of PDMS (through-hole) membranes as shown in the first part 301 can be performed via Al or Ag sputtering deposition by DC magnetron sputtering. The PDMS though-hole membranes 140 attached to the on-demand release tape 130 used for peeling them off the PDMS master can then be subjected to a first conformal metal deposition that ensures coating of top and vertical surfaces with a metal film (see first part 301). In one example, the metal film can be an Al metal film having an exemplary thickness of about 500nm.

[0124] After this first metallization step 301, the membranes 150 can be transferred to another on-demand release tape 131 to enable the coating of the unexposed surface (formerly attached to the tape) with metal, while ensuring no mechanical deformation (see second part 302 and third part 303). Transferring can be achieved using two tapes 130, 131 with different release temperatures (e.g., 90°C and 120°C as shown in Figure 3), or two tapes 130, 131 with differentrelease-mechanisms (e.g., UV versus thermal). In Figure 3, use of tapes with different release temperatures / mechanisms is referred to, namely, “on-demand release tape # 1 , 130” and “on-demand release tape #2, 131”.

[0125] The flipped membrane (once transferred to the tape #2, 131) is subjected to a second metal deposition step achieving the complete and conformal coating of the entire 3D structure (see fourth part 304). At the end of the metal coating step, the metal coated-PDMS through-hole membranes 150 are mechanically robust, so they can be released from the tape 131 and manipulated without the need of a support substrate.

[0126] The polymer-based frequency component 150 as described for the method 100 above with respect to Figure 1, comprises a topside 150a opposite to the releasable structure 130 and a backside 150b facing the releasable structure 130 as shown in Figure 3.

[0127] The method 100 as described above with respect to Figure 1 may further comprise: Placing a second releasable structure 131 on the topside 150a of the polymer-based frequency component 150; Releasing the releasable structure 130 from the backside 150b of the polymer-based frequency component 150; and Metal coating the polymer-based frequency component 150 to obtain a fully metal coated polymer-based frequency component as shown in Figure 3.

[0128] The releasable structure 130 and the second releasable structure 131 may be releasable by thermal activation or by UV activation. Both structures 130, 131 can have different thermal activation temperatures; or one of the two structures 130, 131 may be releasable by thermal activation and the other one of the two structures 130, 131 may be releasable by UV activation.

[0129] Figure 4 shows an exemplary workflow 400 for assembling metal-coated PDMS through-hole membranes.

[0130] The workflow 400 includes a first part 401 comprising: Microcontact printing; a second part 402 comprising: Stabs alignment; a third part 403 comprising: Slabs contacting and Ag NPs sintering; a fourth part 404 comprising: Successive alignment, contacting, and bonding of successive slabs; and a fifth part 405 comprising: Bonded antenna.

[0131] The following description is referring to step 12 of the process (or method 100) described above with respect to Figure 1. Multiple through-hole membranes 150 can be assembled into a monolithic device 420 (e.g., an antenna) by bonding each membrane 150 to the other using a conductive ink. A service frame 411 featuring out-of-plane pillars pairing with dedicated through-holes 412 of the metal-coated membrane 150 can be used to align each membrane 150 to the successive one during the assembly. An embodiment of the assembling procedure is shown here in Figure 4 and can be exemplarily demonstrated with a 3D-printed service frame and using a dispersion of low-temperature sintering silver (Ag) nanoparticles (NPs) as conductive ink for the bonding.

[0132] A film of the Ag-NPs dispersion can be deposited onto the top surface of the sputter-coated PDMS membranes 150 by microcontact printing as shown in the first part 401. First, the Ag-NPs dispersion can be spin coated on a flat surface of a donor substrate. Then, each membrane 150 can be brought in contact with the donor and a thin film of the Ag-NPs ink can be transferred to the top surface of the membrane 150 (see first part 401).

[0133] The membranes 150 can then be sequentially inserted into the alignment frame 411 and thermally bonded one to the other upon sintering of the silver nanoparticles (see second part 402).

[0134] A 3D-printed cover 413 can be used to keep adjacent membranes 150 in intimate contact during the bonding step and ensure uniform metal bonding. The procedure can be repeated for another membrane 150, until a stack 420 with the desired number of membranes 150 is assembled. At the end of the whole assembling procedure, the membrane stack 420 can be removed from the service frame 411 (see fourth and fifth parts 404, 405).

[0135] With respect to the description of Figure 1, the method 100 may further comprise: assembling multiple of the polymer-based frequency components 150 into a monolithic device 420 by bonding each polymer-based frequency component 150 to the other by using a conductive ink or eutectic solder paste as shown in the first part 401 of Figure 4, for example.

[0136] The method 100 may comprise: aligning each polymer-based frequency component 150 to the successive one by placing the multiple polymer-based frequency components 150 onto an alignment frame 410 as shown in the second part 402 of Figure 4, for example.

[0137] The alignment frame 410 may comprise one or more pillars 411 which are paired with dedicated through holes 412 of the polymer-based frequency components 150 as shown in second and third parts 402, 403 of Figure 4, for example.

[0138] The stack 420 can form or implement a monolithic device 420 that can be obtained by the method 100 described above with respect to Figures 1 to 4. The monolithic device 420 may function as a micro wave antenna, a micro wave filter, a beam forming network or an orthomode transducer, for example.

[0139] While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms "include", "have", "with", or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise". Also, the terms "exemplary", "for example" and "e.g." are merely meant as an example, rather than the best or optimal. The terms “coupled” and “connected”, along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other. Although specific aspects have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein.

[0140] Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence. Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the disclosure beyond those described herein. While the disclosure has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the disclosure. It is therefore to be understood that within the scope of the appended claims and their equivalents, the disclosure may be practiced otherwise than as specifically described herein.

Claims

CLAIMS1. A method (100) for manufacturing a polymer-based frequency component (150) for a radio frequency device with through-holes, the method comprising: providing (101) a first polymer foil (110) having a topside (110a) and a backside (110b) opposite to the topside (110a), the first polymer foil (110) comprising a pattern of blind holes ( 111 ) at the topside (110a); disposing and planarizing (102) uncured polymer (121) onto the topside (110a) of the first polymer foil (110), the uncured polymer (121) infiltrating the blind holes (111) and covering the topside (110a) of the first polymer foil (110); curing (102) the planarized uncured polymer (121) to obtain a second polymer foil (120) comprising a cured polymer structure (122) corresponding to the pattern of blind holes (111); removing (103) excess polymer from the second polymer foil (120) down to the topside (110a) of the first polymer foil (110) without removing polymer from the blind holes (111) of the first polymer foil (110) to obtain the first polymer foil (110) with the cured polymer structure (122) arranged in the blind holes (111); placing (104) a releasable structure (130) on the topside (110a) of the first polymer foil (110), the releasable structure (130) being configured to bond to the cured polymer structure (122) and to release the cured polymer structure (122) from the first polymer foil (110); metal coating (106) the releasable structure (130) with the bonded cured polymer structure to obtain a fully or partially metallized polymer membrane (140) with a pattern of through holes (141); and releasing (105) the metallized polymer membrane (140) from the first polymer foil (110) to obtain the polymer-based frequency component (150) with the through-holes.

2. The method (100) of claim 1, wherein the releasable structure (130) comprises a tape that is releasable by thermal activation or by UV activation.

3. The method (100) of claim 1 or 2, wherein the first polymer foil (110) comprises a cured polymer, functionalized to obtain a hydrophobic surface.

4. The method (100) of any of the preceding claims, wherein the first polymer foil (110) is manufactured via Replica Molding, REM, of a positive resist master, thereby obtaining a negative replica of the positive resist master.

5. The method (100) of any of the preceding claims, wherein the uncured polymer (121) comprises a prepolymer.

6. The method (100) of any of the preceding claims, wherein planarizing (102b) the uncured polymer (121) comprises: placing a functionalized PET foil (223) over the uncured polymer (121);sandwiching the first polymer foil (110) with the uncured polymer (121 ) and the functionalized PET foil (223) between two rigid plates (222, 223); and applying pressure (225) onto one or both of the two rigid plates (222, 223).

7. The method (100) of any of the preceding claims, wherein removing (103) the excess polymer from the second polymer foil (120) comprises dry etching in a plasma of O2:CF .

8. The method (100) of any of the preceding claims, wherein metal coating (106) the polymer membrane (140) with the pattern of through holes (141) comprises Al or Ag sputtering deposition by DC magnetron sputtering.

9. The method (100) of any of the preceding claims, wherein the polymer-based frequency component (150) comprises a topside (150a) opposite to the releasable structure (130) and a backside (150b) facing the releasable structure (130); wherein the method (100) comprises: placing a second releasable structure (131) on the topside (150a) of the polymer-based frequency component (150); releasing the releasable structure (130) from the backside (150b) of the polymer-based frequency component (150); and metal coating the polymer-based frequency component (150) to obtain a fully metal coated polymer-based frequency component.

10. The method (100) of claim 9, wherein the releasable structure (130) and the second releasable structure (131) are releasable by thermal activation or by UV activation; and wherein both structures (130, 131) have different thermal activation temperatures; or wherein one of the two structures (130, 131) is releasable by thermal activation and the other one of the two structures (130, 131) is releasable by UV activation.

11. The method (100) of any of the preceding claims, comprising: assembling multiple of the polymer-based frequency components (150) into a monolithic device (420) by bonding each polymer-based frequency component (150) to the other by using a conductive ink or eutectic solder paste.

12. The method (100) of claim 11, comprising: aligning each polymer-based frequency component (150) to the successive one by placing the multiple polymer-based frequency components (150) onto an alignment frame (410).

13. The method (100) of claim 12, wherein the alignment frame (410) comprises one or more pillars (411) which are paired with dedicated through holes (412) of the polymer-based frequency components (150).

14. The method (100) of claim 12 or 13, comprising: placing a cover frame (413) onto the multiple polymer-based frequency components (150) placed above each other to keep the multiple polymer-based frequency components (150) in contact with one another during the bonding.

15. The method ( 100) of any of the preceding claims, wherein the releasable structure (130) is configured to release the cured polymer structure (122) from the first polymer foil (110) without any mechanical deformations; and wherein by releasing (105) the metallized polymer membrane (140) from the first polymer foil (110) the metallized polymer membrane (140) is obtained without any mechanical deformations.

16. A polymer-based frequency component (150), obtainable by the method (100) for manufacturing a polymer-based frequency component (150) according to any one of the preceding claims.

17. A monolithic device (420), obtainable by the method (100) for manufacturing a polymer-based frequency component (150) according to any one of claims 11 to 14.

18. The monolithic device (420) of claim 17, forming a microwave antenna, a microwave filter, a beam forming network or an orthomode transducer.

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