Method for manufacturing a planar slow-wave structure
By growing polycrystalline diamond on a silicon substrate with a meander structure and additional features, the method addresses heat dissipation challenges in TWTs, enhancing output power and simplifying manufacturing, resulting in efficient short-wavelength TWTs with improved thermal performance.
Patent Information
- Authority / Receiving Office
- RU · RU
- Patent Type
- Patents
- Current Assignee / Owner
- AKTSIONERNOE OBSHCHESTVO NAUCHNO PROIZVODSTVENNOE PREDPRIYATIE ISTOK IMENI A I SHOKINA
- Filing Date
- 2026-03-10
- Publication Date
- 2026-07-09
AI Technical Summary
Existing methods for manufacturing shortwave traveling-wave tubes (TWTs) face challenges with efficient heat dissipation from the TS components, particularly due to the complexity and cost of thermal etching processes required for high surface finish precision, which is difficult to achieve.
A method involving the growth of polycrystalline diamond on a silicon substrate, forming a meander structure with additional through holes and roundings, applying a highly adhesive sublayer, and using a split housing design with low-temperature soldering to create a monolithic block, reducing dielectric material volume and improving thermal performance.
This approach enhances heat dissipation, increases output power, and improves electrodynamic characteristics, while simplifying the manufacturing process and reducing costs by eliminating thermal etching, thus enabling highly efficient short-wavelength TWTs.
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Abstract
Description
[0001] The invention relates to the production of vacuum tube devices, in particular the manufacture of planar-type slow-wave tubes (SWTs) for short-wavelength traveling-wave tubes (TWTs).
[0002] Limitations on the output power of shortwave TWTs are typically related to issues with efficient heat dissipation from the TS components. A key challenge in developing modern TWTs in this frequency range is the creation of promising technological solutions for the production of TS components with improved heat dissipation characteristics.
[0003] A fairly large number of methods for manufacturing shortwave TS are known from the prior art, for example, Russian Federation Patent No. 2340036, "Method for Manufacturing a Slow-Motion System for a Traveling Wave Tube," dated November 27, 2008, Bulletin No. 33, and others. However, these methods require the production of non-planar TS.
[0004] The method described in the paper "Monolithic slow-wave structure made of polycrystalline diamond for millimeter-wave TWTs" (Shcherbakov S.V., Fedorov Yu.Yu., Kulikov E.N. et al. / / Nano- and Microsystems Engineering, Vol. 21, No. 9, pp. 522-526) was selected as a prototype. A technology for creating a slow-wave structure for millimeter-wave TWTs has been developed. The slow-wave structure is made entirely of polycrystalline CVD diamond, formed in the form of a meander, with metallization of the order of the skin-layer thickness applied to all surfaces. This technology makes it possible to obtain a monolithic slow-wave structure with effective heat dissipation and high mechanical strength.
[0005] A disadvantage of the prototype is the formation of the ZS using thermal etching technology, which complicates and increases the cost of manufacturing. Furthermore, for the ZS in the millimeter-wavelength range, high surface finish precision (roughness class of at least 10) is required, which is difficult with thermal etching.
[0006] The proposed technical solution is aimed at eliminating the shortcomings of the prototype.
[0007] The technical result is to expand the possibility of manufacturing highly efficient slow-wave systems with good heat-dissipation capacity for the class of non-helical slow-wave systems of TWTs with increased output power in the short-wavelength range.
[0008] The technical result is achieved by the fact that during the manufacture of a planar meander slow-wave structure, which includes growing polycrystalline diamond on a silicon substrate, forming a diamond blank to the overall size of the slow-wave structure, forming conductors in the form of a meander, during the formation of conductors in the diamond blank, through rectangular holes with roundings are additionally made in the area of the short-circuited end of the meander; a highly adhesive sublayer is applied and the surfaces of the holes, located directly under the section of conductors in the form of a meander, are subsequently metallized; a detachable housing is manufactured, in two parts of which longitudinal ledges and grooves are formed; diamond blanks with a meander slow-wave structure are fixed on the ledges of each part and the parts of the housing are connected into a monolithic block using low-temperature soldering mode.
[0009] The essence of the technical solution is as follows. The creation of additional through rectangular holes with roundings in the area of the short-circuited end of the meander reduces volumetric losses by reducing the volume of the dielectric material (CVD diamond) and the reflection coefficient due to the rounding:
[0010] 1) the electrodynamic characteristics of the slow-wave structure are improved, in particular, the value of the coupling resistance of the slow-wave structure is increased, which makes it possible to increase the output power of the TWT;
[0011] 2) Improves the matching of the slow-wave system with the input / output of microwave energy in a wide frequency band.
[0012] Applying a highly adhesive sublayer ensures high adhesion strength of the metal film to the polycrystalline diamond and protects the metallization from overheating (the metal film has low thermal resistance) between the diamond and metal, as well as from mechanical damage. This improves the thermal performance and operational reliability of the short-wavelength TWT.
[0013] Metalization of the inner surfaces of the holes located directly beneath the meander-shaped conductors creates a parallel high-frequency channel, allowing for an expanded bandwidth in the high-frequency region. Furthermore, it serves as an electron interceptor, preventing the dielectric substrate of the slow-wave structure from charging and causing electrical breakdown during electron flow through the device's slow-wave structure.
[0014] Thus, in this technical solution, the technological process eliminates thermal etching of the dielectric substrate made of polycrystalline diamond and simplifies the manufacturing technology.
[0015] The split housing design allows for high-precision shoulders and grooves in each section. The grooves in the housing reduce losses in the slow-wave structure, which also increases the TWT output power. The diamond-cut slow-wave blanks, shaped like a meander, are secured to the housing shoulders, facilitating the alignment of two similar slow-wave structures.
[0016] The body is assembled into a monolithic block using low-temperature soldering to prevent the formation of graphitized conductive layers on the surface of the diamond blanks.
[0017] The invention is illustrated by a drawing. Fig. 1 shows a general view of the design of a planar ZS, where:
[0018] 1 - polycrystalline diamond blank,
[0019] 2 - meander conductors,
[0020] 3 - through rectangular holes with roundings in the area of the short-circuited end of the meander,
[0021] 4 - metallization of the surface of holes,
[0022] 5 - detachable housing,
[0023] 6 - longitudinal ledges of the body,
[0024] 7 - longitudinal grooves of the body.
[0025] The method is implemented as follows. A diamond blank 1 is formed to the overall dimensions of the retarding system, for example, using a laser. Then, in the diamond blank 1, the topology of the meander conductors 2 is formed, for example, using precision laser cutting with a positioning accuracy of at least 1-2 µm.
[0026] Next, diamond workpiece 1 undergoes post-processing to clean the surface, including reducing surface roughness. Post-processing consists of chemical and laser grinding. After laser processing, the graphitized electrically conductive layers on diamond workpiece 1 are removed, for example, in a sulfuric acid etchant.
[0027] After cleaning the surface of the diamond workpiece 1, for example, through a stencil, a highly adhesive sublayer is sprayed to metallize the conductors 2 and the surface of the holes 4.
[0028] A split housing 5 is manufactured, in two parts of which longitudinal ledges 6 and grooves 7 are formed, for example, by milling. A diamond blank 1 is secured on the ledges 6 and all parts of the structure are connected, for example, by soldering, into a monolithic block.
[0029] This sequence of actions for manufacturing a planar slow-wave structure allows for metallization on polycrystalline diamond without transition graphitized layers and with low thermal resistance between the diamond and the metal, ensuring reliable operation of the TWT with high output power under the required thermal conditions.
[0030] An example of a method for manufacturing a delay system. The delay system elements, consisting of 140 periods of 190 µm each, have the following dimensions: width, length, and height of the diamond workpiece: 1 - 1.5 mm, 26.6 mm, and 0.2 mm.
[0031] When forming conductors in diamond blank 1, additional through rectangular holes 3 are made with roundings in the area of the short-circuited end of the meander. The width and height of hole 3 are 0.95 mm and 0.2 mm, respectively.
[0032] Applies a highly adhesive sublayer and subsequent metallization of the hole surfaces located directly beneath the meander-shaped conductor section. The metallization height and thickness of the hole surface are 3-0.2 mm and 3 µm; the height and thickness of the conductors are 2-5 µm and 250 µm.
[0033] A split housing is manufactured, in two parts of which longitudinal ledges and grooves are formed; the width and height of the housing 5 are 2 mm and 1.5 mm; the width of the longitudinal ledge 6 is 0.25 mm; the height and width of the longitudinal groove 7 are 0.5 mm and 1 mm.
[0034] The split body 5 is made of copper, the conductors 2 are made of gold, the high-adhesion sublayer consists of W-Ni with the thickness of each layer being 0.2 μm.
[0035] Diamond blanks with a meander retarding system are fixed on the ledges of each part and the parts of the body are connected into a monolithic block using thermal diffusion soldering at a temperature of 450°C.
[0036] Thus, using the proposed method, it is possible to manufacture planar-class slow-wave systems with good heat-dissipating capacity in the short-wavelength range.
Claims
A method for manufacturing a planar meander slow-wave structure comprising growing polycrystalline diamond on a silicon substrate, forming a diamond blank to the overall dimensions of the slow-wave structure, and forming conductors in the form of a meander, wherein, when forming the conductors in the diamond blank, additionally through rectangular holes with roundings are made in the region of the short-circuited end of the meander; applying a highly adhesive sublayer and subsequently metallizing the surfaces of the holes located directly under the section of conductors in the form of a meander; manufacturing a detachable housing in two parts of which longitudinal ledges and grooves are formed; securing diamond blanks with a meander slow-wave structure to the ledges of each part and joining the parts of the housing into a monolithic block using low-temperature soldering.