CZ30054U1 - Apparatus for producing flexible multimode optical planar waveguides - Google Patents

Description

Technical field

Flexible multimode optical waveguides solve the problem of light transmission over medium distances (up to 40 cm). With this solution, higher data rates and volumes can be achieved than with metallic or wireless data. These optical waveguides can be used in data centers for PCB, chip-to-chip, or rack-to-rack connections.

BACKGROUND OF THE INVENTION

Fiber optic waveguides are used in optical telecommunications technology for the distribution of optical signals over long distances using quartz optical single mode fibers having a core / sheath geometric dimension of 9/125 pm, or multi-mode optical fibers with geometric dimensions of 50 / 125 pm or 62.5 / 125 pm.

Less frequently, other types of multimode optical fibers with dimensions such as 200/230 pm, 730/750 pm, 980/1000 pm and others are also used for data transmission and for sensor systems with lower transmission capacity and for shorter distances.

Telecommunication optical systems in backbone networks use wavelengths of 1550 nm, the so-called third telecommunication window, where the quartz fibers have the lowest optical attenuation or wavelengths of 1310 nm, the so-called second telecommunication window, where the quartz fibers have the lowest dispersion.

In some cases, a wavelength of 850 nm is used, the so-called first telecommunications window. This wavelength is used for less demanding data transmission, both economically and technically, which takes place over shorter distances with less data.

In recent years, POF optical fibers, the Plastic Optical Fiber, with a large waveguide layer diameter of 980 µm, have also been used, which are mainly used for data transmission in the automotive industry, and these fibers most commonly use wavelengths of 650 nm.

With the massive development of the Internet and the ever-increasing demand for data rates, data transmission over short and medium distances, which has so far been exclusively carried out using a metallic or wireless connection, has been replaced by data transmission over optical lines. Recently, research and development has been focused on optical waveguides that allow optical communication for short distances up to 300 m (SR - Short Reach), very short distances up to 5 cm (ESR - Extra Short Reach) or even ultra short distances up to 1 m. cm (USR). In addition, the replacement of the metallic link, which has been used to transmit data using an electrical signal to date, and optical waveguide interconnections, which allow the transmission and processing of optical signal data, is also being tested, especially in data centers and super fast high-performance computers. New types of optical waveguides are being developed for this type of data transmission.

Optical planar waveguides are realized by applying the waveguide layer to the planar substrate or by diffusion directly into the substrate. The channel waveguide is the basis for realization of the photonic structure itself, where the waveguide structure is spatially limited.

Optical flame waveguides are made of semiconductor materials, optical glasses, special optical crystals and new possibilities of using new polymer materials are also tested. Optical waveguides in the case of semiconductor waveguides are manufactured using thin film technologies. In the case of waveguides made of optical glasses and optical crystals, they are most often produced by means of single-stage or two-stage ion exchange, or by electro-diffusion. These technological processes are well managed, but technologically demanding and therefore costly. This type of technological process also works with chemicals and materials that are heavily polluting the environment.

For the production of polymeric optical waveguides, it is sought to use technological processes that are compatible with technological processes for optical waveguides made of semiconductors. The optical waveguides produced in this way have geometrical dimensions such that they are of the micrometer size and the length of these waveguides is only

CZ 30054 UI a few millimeters maximum centimeters. These waveguides are operated at the usual telecommunication wavelengths of 1310 nm and 1550 nm. Multidimensional waveguides with a waveguide core dimensions of 50x50 μιη (width x height) and operating at a wavelength of 850 nm are used for optical interconnection using mid-range optical planar waveguides.

Until recently, copper-wire interconnection has been used exclusively for data transfer between the FR4 board-board or chip-chip, rack-rack, etc. At present, systems are being developed where metallic interconnection would be replaced by optical interconnection. Optical fiber interconnection was tested first and the possibilities of optical fiber waveguide interconnection are currently being studied. One of the important properties of these waveguides is their mechanical flexibility-flexibility. Therefore, for this type of planar optical waveguides, new polymer waveguides implemented on flexible substrates are tested.

There are known solutions where these waveguides have been realized on flexible thin foil substrates, Pyralux, Kapton or FR4 substrates. The realized waveguides had geometrical dimensions 50x50 μιη (height x width) and were designed for working wavelengths 850 nm. These optical waveguides were manufactured using the rotary casting method, where the geometric dimensions were then realized by optical lithography and wet etching. The disadvantage of this solution is the high purchase cost of the photolithographic device. Another disadvantage of this process is the possibility to realize optical waveguides with a maximum length of 4.5 cm when using 2 optical lithography or a maximum of 9.5 cm using 4 optical lithography. Optical lithography with a maximum size of 8 '' (20 cm) is currently available. In this way it would be possible to realize waveguides up to a maximum size / length of 20 cm. The disadvantage of this method is also the inefficient application of individual layers and the necessity of a larger amount of material for the waveguide and cover layer. When applying polymers by the rotary casting method in order to homogeneously / uniformly apply the individual coatings of the functional layers, it is necessary to cover the entire substrate before centrifuging with the polymer, from which a large amount of polymer is then centrifuged and thus lost.

There is a known solution for the production of a polymer waveguide on a solid support such as Si (silicon support), FR4 (printed circuit board, FR4 is a designation for reinforced fiberglass laminates of epoxy fiberglass) or glass as described by N. Bamiedakis et al. al. entitled Cost-Effective Multimode Polymer Waveguides for High-Speed On-Board Optical Interconnects, published in the IEEE Journal of Quantum Electronics, vol. 45, no. No. 4, 2009, where the authors used a standard photolithographic process and created a waveguide in the form of a spiral of polymer materials developed by Dow Corning, where the siloxane polymer OE-4140 was used as the core of the waveguide and polymer OE-4141 was used as the lower interlayer and top cover.

The production of polymer waveguides on a solid support by laser lithography by A. Elmogi et al. in the article Comparison of epoxy- and siloxane-based single-mode optical waveguides defined by direct-write lithography, published in Optical Materials vol. 52, 2016 pp. 26-31, but this technology does not allow the simple production of long optical waveguides. Due to technological demands, commercial laser lithographs do not allow the illumination of larger areas than 15x15 cm, but usually these lithographs allow the illumination of the maximum area of less than 10x10 cm.

Also described was a process for making polymer waveguides by the flexible stamping method described by J. Kobayashi et al. in the article Low loss polymer optical waveguide replicated from a flexible film stamp made of polymeric material, published in Japanese Journal of Applied Physics 52 (2013) 072501. This method, however, again does not make waveguides longer than 10 cm, because they are not available for these applications presses with larger punch dimensions.

It is also known to produce optical multimode waveguides, where these waveguides were realized by the role-to-role method (the method of unwinding from a cylinder). On a film that is unwound from a roll and on which an intermediate layer is applied, which is heat treated and cured by UV light. Subsequently, a waveguide layer is applied, into which a ridge waveguide is formed by means of a punch, which is placed on another cylinder, wCZ 30054 U1. The wool-water layer is cured by UV light and at the end a protective cover layer is applied to the waveguide layer, which is of the same material as the optical interlayer applied to the film, which serves as a backing. The advantage of this method is that the flexible washer is unwound from the cylinder and thus very long planar optical waveguides (tens of centimeters to meters) can be produced. The disadvantage of this method is the high cost of purchasing this dedicated device.

The disadvantage of the above mentioned solutions is that they enable the realization of optical waveguides only with the help of special technological equipment, whose acquisition costs are very expensive. These solutions allow the implementation of optical waveguides of only limited dimensions (up to approx. 10 cm in exceptional cases 20 cm) and also deposition is poorly effective due to greater material loss in the application of rotary casting.

The essence of the technical solution

The above-mentioned drawbacks are overcome by the apparatus for producing flexible multi-mode optical planar waveguides according to the present invention.

The apparatus comprises at least one block for applying polymer layers and at least one block for illuminating these layers with UV radiation. These polymer layers comprise an intermediate layer, a waveguide layer and an upper cover layer. The essence of the new device is that each polymer coating block includes an automated motorized film applicator designed for color application testing equipped with a spiral stretcher. The helical winding ruler is either a cylindrical threaded rod or a wire wrapped around a cylindrical rod, the wound wire forming threads around the cylindrical rod, the depth of the threads determining the thickness of the deposited layer. The active film deposition area in the automated motorized film applicator has a width of at least 20 cm, typically 30 cm, and a length of at least 30 cm, typically 40 cm. Each UV illuminating block includes a large-area exposure unit intended to illuminate a printed circuit board, the exposure unit having an exposure area width of at least 40 cm, typically 1 m, and an exposure area length of at least 40 cm, typically 1 m.

In one preferred embodiment, the apparatus comprises exactly one block for applying polymer layers, wherein the automatic motorized film applicator included in the block is equipped with at least two interchangeable spiral stretch rulers.

Among these interchangeable spiral winding rulers, there is at least one thread depth for applying a thickness of a bilaterally sealed interval of from 20 pm to 30 pm and at least one thread depth for applying a layer of a bilaterally sealed interval of from 45 pm to 55 pm.

In another preferred embodiment, the apparatus comprises more than one block for applying polymer layers and / or more than one block for illuminating with UV radiation. In this case, the spiral stretchers in the at least two blocks for applying the polymer layers have different thread depths with each other and at least one of the blocks for illuminating with UV radiation comprises a photolithographic mask.

Between the spiral stretchers included in the different polymer application blocks there is at least one with a depth of thread for applying a thickness of a bilaterally sealed interval of from 20 pm to 30 pm and at least one with a depth of threads for applying a layer of a bilaterally sealed interval of 45 pm to 55 pm.

It is preferred that all spiral winding rulers fitted with an automatic motorized film applicator or automatic motorized film applicators are stainless steel.

In a preferred embodiment, a laminator for papim lamination is located downstream of the blocks for applying polymeric layers of the planar optical waveguides and the blocks for illuminating these layers with UV radiation.

The advantage of this device is, in particular, that it makes it possible to produce flexible multi-mode optical planar waveguides of large dimensions, up to a length of 40 cm, using technologies not previously used for waveguide production and intended for completely different applications. These technologies

The CZ 30054 U1 are considerably cheaper than the technologies commonly used for the production of flexible multi-mode optical planar waveguides, which in addition made it possible to produce only shorter waveguides. Flexible multidimensional optical flame waveguides up to 40 cm long made in accordance with the new solution advantageously replace metallic or wireless connections between the FR4 board-board and chip-chip, rack-rack interconnections as they allow for higher data rates and data rates.

Clarification of the drawing

An exemplary embodiment of an optical flame multimode waveguide implemented by the above device is shown in Fig. 1.

Examples of technical solutions

A topological diagram of an exemplary optical flame multimode waveguide, which is made using a device using automatic motorized film applicators equipped with helical winding rulers, is shown in Fig. 1. Dimensional, temperature and time parameters are given by way of example, but also possible other embodiments of the invention with different parameters.

The waveguide consists of a flexible substrate 1 on which a polymer layer 2 is applied, which must have a thickness of at least 20 µm. Between the layer 2, the wool is an aqueous layer 3 with typical dimensions 50x50 µm (height x width) and a length of up to 40 cm on which the top layer 4 is applied, which is of the same material as the interlayer 2 and also has a minimum thickness of 20 µm. In some embodiments, lamination 5 can be used to provide lamination resistance for greater mechanical stress resistance.

The automatic motorized film applicator used in the present technical solution is intended for testing the application of paints and coatings, for the production of optical waveguides or photonic structures has not been used so far. The automatic motorized film applicator is equipped with a spiral stretching ruler or a set of these rulers. The spiral ruler either takes the form of a cylindrical bar with recessed threads or contains a wire wrapped around a cylindrical bar. In the latter case, the threads are formed by spirals of wire wrapped around the bar. The thread depth is then equal to the thickness of the wire used. In a preferred embodiment, all the threads on one helical stretcher have the same depth. In a preferred embodiment, the helical stretcher is made of stainless steel. The thickness of the applied polymer layer is determined by the parameters of the helical stretcher, i.e., in particular, by the depth and characteristics of the threads. then the rulers for applying additional layers replace, or each layer thickness is assigned its own automatic motorized film applicator with a dedicated ruler. Advantageously, for example, TQC automatic motorized film applicators or Elcometer 4340 automatic motorized film applicators can be used. One of their advantages is that these automatic motorized film applicators ensure a homogeneous coating due to a precisely defined spiral feed ruler.

The flexible support i may be of polymer flexible films (e.g., Melinex® ST726 from DuPont Teijin Films, HOSTAPHAN® GN2504600 from Mitsubishi Polyester Film GmbH or PLEXIGLAS® Film OF058 from Evonik Industries AG and others) or from Pyralux, Kapton or FR4. The intermediate layer 2 is applied to the support 1 by means of an automated motorized film applicator with a spiral stretcher whose depth and thread characteristics correspond to the thickness of the intermediate layer 2. The thickness between the layers 2 must be greater than or equal to 20 µm. In one embodiment, the intermediate layer 2 may be formed from a polymeric epoxy resin material EpoClad. The property of this intermediate layer 2 must be a lower refractive index than the waveguide layer 3. After the application of the intermediate layer 2 consisting of EpoClad, the layer is heated on a plate to heat the plates to 50 ° C for 10 minutes, then the temperature is 100 ° C. 1Π 7a minutes o / t zi / A ΟΠ OP * DtU

CZ 30054 Ul Khan for 10 minutes. Then the sample is cooled to room temperature and cured by UV radiation for 2 minutes. UV light curing is performed using a PCB exposure unit that allows large format exposure. The advantage of this process is lower acquisition and operating costs than when using an optical lithograph, and for producing structures with dimensions of 50 µm and larger, this technology is sufficiently accurate and, unlike an optical lithograph, does not need additional vibration protection. In contrast to optical lithographs, it makes it possible to create structures up to 40 cm long, while the structures produced by lithographs allow the production of structures with a maximum possible length of 10 cm, exceptionally 20 cm. The plate is then heated again to 50 ° C for 10 minutes, then the temperature is again gradually increased at a rate of 10 ° C per minute to a temperature of 90 ° C when the sample is exposed to this temperature for 10 minutes.

This is followed by the application of an optical waveguide layer 3 consisting of epoxy resin EpoCore. The coating is again carried out by means of an automated motorized film applicator, where a type of spiral stretcher is used so that the thickness of the optical waveguide layer is 50 µm. After deposition with an automatic motorized film applicator, the optical wave aqueous layer 3 is heated to 50 ° C for 10 minutes, then the temperature is gradually increased at a rate of 10 ° C per minute to 90 ° C. The sample is left at this temperature for 10 minutes. Cooling of the sample to room temperature is followed by insertion of the sample into a large-area PCB imagesetter, where the sample is masked on a thin film with a dark field with a transparent 50 µm line motif. The sample is illuminated by UV radiation through this mask. The sample is then heated to 50 ° C for 10 minutes, then the temperature is gradually increased at a rate of 10 ° C per minute to 90 ° C. The sample is left at this temperature for 10 minutes. After cooling the sample to room temperature, the sample is placed in the OrmoDev developer. In this process step, the non-illuminated portion of the optical waveguide layer 3 is etched off. After removing the sample from the developer, the sample is washed in isopropyl alcohol and demineralized water. In this way, an optical multi-channel channel waveguide 3 is formed having a size of 50x50 µm (height x width) and an optical waveguide length of up to 40 cm.

This is followed by the application of the upper cover layer 4, which is composed of the same material as the intermediate layer 2, with epoxy resin EpoClad. The application of the topsheet 4 is again carried out by means of an automated motorized film applicator, again using a spiral stretcher of a type such that the thickness of the topsheet 4 is at least 20 µm. After the topcoat 4 has been applied, the sample is heated on a plate to 50 ° C for 10 minutes, then the temperature is gradually increased at a rate of 10 ° C per minute up to 90 ° C. The sample is left at this temperature for 10 minutes. Then, the sample is cooled to room temperature and cured by UV radiation for 2 minutes in the exposure unit for exposure of the printed circuit boards. Heating is continued at 50 ° C for 10 minutes, then the temperature is gradually raised at a rate of 10 ° C per minute to 90 ° C when the sample is exposed to this temperature for 10 minutes.

This is followed by lamination of the optical waveguide into the protective film 5 for greater resistance to mechanical damage. The lamination is preferably performed using a papim laminator. A suitable laminator for office purposes is NeptuneTM 2125 Lammator, using standard laminating foil with a thickness of 80 µm.

Then the optical waveguide is cut at both ends using a diamond circular saw, where a speed of 30,000 rpm is used to achieve the optical quality of the waveguide fronts with a feed rate of 1 mm / s.

Finally, an optical connector (eg, a standard MTO / MTP connector) not shown in the accompanying drawing may be attached to the optical waveguide to allow interconnection of commonly used optoelectronic modules.

In one preferred embodiment, the waveguide layer 3 is applied in the same automatic motorized film applicator as the intermediate layer 2 and the topsheet 4, wherein a spiral stretcher ruler is exchanged between the coating layers of different thicknesses in the automatic motorized film applicator. This design is more cost-effective. However, changing rulers causes time loss.

CZ 30054 Ul

In another preferred embodiment which allows faster waveguide production, the apparatus for producing the waveguides comprises two or three automatic motorized film applicators, each of the applicators being fitted with a spiral stretcher whose parameters correspond to the layer being deposited therein. In the case of two automatic motorized film applicators, the first one has a spiral stretcher with parameters for applying the interlayer 2 and the topsheet 4 and the second automatic motorized film applicator has a spiral stretcher with parameters for applying the waveguide layer 3. For three automatic motorized film applicators each has a spiral stretcher with parameters corresponding to the layer being applied, i.e. the first applicator has a spiral stretcher with parameters for the intermediate layer 2, a second applicator a spiral stretcher with parameters for the waveguide layer 3, and a third applicator a spiral stretcher with parameters for the topsheet 4.

Similarly, the apparatus for producing flexible multi-mode optical planar waveguides may include one or more large area imaging units designed to illuminate printed circuit boards. In one preferred embodiment, which provides lower input costs, the UV curing processes of the interlayer 2 and the topsheet 4 as well as the UV radiation of the waveguide layer 3 through the photolithographic mask, take place in the same large-area exposure unit intended for exposure of printed circuit boards. To save time, but some or all of these processes may take place in a variety of large-area exposure units designed to illuminate a printed circuit board.

The fastest production of flexible multimode optical waveguides will take place in a preferred embodiment of the device comprising the first automatic motorized fdmu applicator with a spiral stretcher with parameters for the application of the intermediate layer 2, followed by a large-area exposure unit intended for exposure of printed circuit boards. curing of the interlayer 2 by UV radiation. This is followed by a second automatic motorized film applicator with a spiral stretcher with parameters for applying the waveguide layer 3, followed by a second large-area exposure unit intended for the illumination of printed circuit boards in which the waveguide layer 3 is illuminated by UV radiation through a photolithographic mask. In addition, a third automatic motorized film applicator with a spiral stretcher with parameters for applying a topcoat 4 is provided, followed by a third large-area exposure unit intended to illuminate the printed circuit boards in which the topcoat 4 is UV cured. Between the just-mentioned automatic motorized film applicators and the large-area exposure units for the illumination of the printed circuit boards, there are also stations for wet processes and heat treatment as described above. At the outlet of the device is then included a laminator for paper lamination, on which the laminated waveguide is laminated into a protective film 5.

Industrial applicability

The present solution can be used for interconnection between FR4 board-board, chip-chip, rack-rack by optical signal. The advantage of this solution is the possibility of producing optical flexible waveguides up to 40 cm long.

PROTECTION REQUIREMENTS

Claims (7)

An apparatus for producing flexible multimode optical waveguides comprising polymer layers, the apparatus comprising at least one block for applying polymer layers and at least one block for illuminating these polymer layers by UV radiation, the polymer layers comprising an intermediate layer (2), a waveguide layer ( 3) and a topcoat (4), characterized in that each polymer coating block includes an automated motorized film applicator for testing paint application equipped with a spiral stretcher, either as a cylindrical threaded rod or as a wire wrapped around a cylindrical bar, wherein the wrapped wire forms threads around the cylindrical bar, the depth of the threads determining the thickness of the deposited layer and the thickness of the thread. In an automotive motorized film applicator, it has a width of at least 20 cm, typically 30 cm, and a length of at least 30 cm, typically 40 cm, and that each UV illuminating block includes a large-area exposure unit designed to illuminate printed circuit boards. the exposure unit has an exposure area width of at least 40 cm, typically 1 m, and an exposure area length of at least 40 cm, typically 2 m. Device according to claim 1, characterized in that it comprises exactly one block for the application of the polymer layers, the automatic motorized film applicator included in the block being equipped with at least two replaceable spiral stretchers. Device according to claim 2, characterized in that between the interchangeable spiral winding rulers there is at least one with a depth of threads for applying a layer of thickness from a mutually closed interval from 20 pm to 30 pm and at least one with a depth of threads for applying a layer of z thickness. bilaterally closed interval from 45 pm to 55 pm. Apparatus according to claim 1, characterized in that it comprises more than one polymer coating block and / or more than one UV illuminating block, the helical stretch rulers in at least two polymer coating blocks having different thread depths with each other and wherein at least one of the UV illuminating blocks comprises a photolithographic mask. 5. The apparatus of claim 4, wherein at least one of the spiral stretch rulers included in the various polymer coating application blocks has a thread depth for applying a layer having a thickness from a closed interval from 20 pm to 30 µm and at least one with a depth of threads for applying a layer having a thickness from a mutually closed interval of 45 µm to 55 µm. Device according to any one of claims 1 to 5, characterized in that all the spiral stretchers that are fitted with the automatic motorized film applicator or automatic motorized film applicators are of stainless steel. Apparatus according to any one of the claims 1 to 6, characterized in that a laminator for papim lamination is arranged in its end part behind the blocks for applying the polymer layers of the planar optical waveguides and the blocks for illuminating these layers by UV radiation.