RU2507306C1 - Sputtering unit of coatings onto precision parts of assemblies of gyroscopic instruments - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: sputtering target creates an annular zone of an evaporated material flow with average diameter D_m. Holders with attachment assemblies of sputtered parts are installed on stocks in the quantity of n. Stocks are rotated at angular speed w₁ in one direction, and a reduction unit is rotated at angular speed w₂ in another direction and the above stocks are arranged on it uniformly at equal distance of 1/2·D_m from its rotation axis. A plane in which centres of attachment assembles of parts lie is inclined to the symmetry axis of that flow at an angle for the purpose of more optimum orientation of working surfaces to the sputtered material flow. In order to provide constant movement conditions of parts in an evaporated material zone, holders in which parts are installed are made in the form of cantilever elements with displacement of a centre of the attachment assembly of each part relative to the stock axis. For one pair of opposite lying stocks located on a longer axis of an elliptical trajectory of their movement, displacement direction L is oriented to the ellipse centre, and for the second pair of opposite lying stocks located on a shorter axis of that trajectory displacement direction L is oriented to the side that is opposite to the centre of the above ellipse.

EFFECT: improving quality and functional characteristics of sputtered coatings.

3 dwg

Description

The invention relates to the technology of forming thin-film coatings by the method of magnetron sputtering and can be used in precision instrumentation in the development and manufacture of precision gas-dynamic bearings of float gyroscopes.

In a two-stage float gyroscope developed by the Concern TsNII Elektribribor OJSC, the main nodes are the rotor that performs the function of kinetic momentum, rigidly connected to the flanges of two inverted gas-dynamic bearings, which orient the rotor and set the input axis of the gyro sensitivity. The manufacturing technology of parts of a gas-dynamic bearing involves forming hemispherical wear-resistant coatings of titanium nitride TiN with a thickness of one micrometer on the finished hemispherical surfaces finally made with precision in tenths of a micrometer. The most effective coating method is magnetron sputtering.

The accuracy of the gyroscope and the stability of its technical characteristics directly depend on the geometry and quality of the working surfaces of the parts of gas-dynamic bearings, and strict requirements are imposed on the TiN coating in terms of tribological properties, structural uniformity, and also in geometry - in layer thickness and permissible deviations from its nominal value - the level of tenths and hundredths of a micrometer. Obviously, the possibility of obtaining the indicated level of accuracy is largely related to the design of the equipment used and the means of equipping the magnetron sputtering process. An important characteristic of the wear-resistant TiN coating is the identity of its dimensional parameters and properties on the working surfaces of the entire set of bearings and bearing flanges used in one product. This is achieved by creating the most equivalent spraying conditions for all parts of the kit, which is carried out by spraying this kit in one technological cycle, i.e. the design of the installation should include multi-position spraying. In addition, the same conditions are largely ensured by the strictly symmetrical arrangement of the parts relative to the flow of the sprayed material, as well as due to the rotation of both the cage (or reduction unit) on which the rods with parts are located, and the rods themselves. Rotation averages the possible difference in spraying conditions, since all parts are in equal time for all spraying zones.

A known installation for spraying coatings [Japanese application No. 63-65071], comprising a vacuum chamber, magnetron sputter targets, gas supply devices, a rotation drive of the substrate holders in one direction and a rotation drive of the device on which the substrates are mounted in the other direction. The disadvantage in this case is the impossibility of obtaining coatings with an accuracy of a tenth of a micrometer on hemispherical and curved surfaces, since different parts of the sprayed surface are oriented to the flow of material evaporated from the targets at different angles, which determines the heterogeneity of the coating in thickness and properties.

A known installation for spraying coatings [RF patent No. 2214477], including a vacuum chamber, target cathode sprays with anode blocks, gas supply control devices, substrate holders rotating in one direction, a device on which these holders are mounted rotating in another direction , and a device for rotating the device. At least two target sprays are positioned so that their centerlines form an angle of not more than 90 ° and are offset in height relative to each other. This allows you to improve the deposition conditions on the surface of complex shape, including spherical. However, to ensure the above, required for gas-dynamic bearings of the float gyroscope, the accuracy and uniformity of the coating presented by the installation does not allow. In addition, the disadvantage in this case is the complexity of the multi-position spraying process, which is important for a set of bearing parts, which includes two flanges and two bearings, which under simultaneous spraying conditions make it possible to obtain a coating that is identical in basic characteristics. In the installation of the above design, the complexity of the intracameral configuration (two magnetrons) leads to mutual screening of the sprayed parts, and the efficiency of simultaneous spraying is not realized.

As close technical solutions, we can cite RF patents No. 2098511 and No. 2411304, where the mutual movement of the evaporator and the substrates is used to increase the uniformity of the sprayed coatings, as well as Japanese patent No. 6099803, which also uses the rotation of the substrate holder. However, the above technical solutions do not solve the problem of ensuring uniformity and quality of the resulting coatings at the level required in gyroscopic devices.

According to the largest number of common essential features, the installation of magnetron sputtering was adopted as a prototype [S.N. Belyaev, A. Scherbak Means of equipping the processes of spraying coatings on gyrodevice assemblies having the form of bodies of revolution // Navigation and Motion Control: Materials of the 10th Anniversary Conference of Young Scientists. - State Research Center of the Russian Federation - FSUE TsNII Elektropribor, 2009, p. 68-73, ISBN 978-5-900780-88-7], containing a vacuum chamber, a gas supply device, a target atomizer, an ion source and a system of magnets that create annular flow zone of vaporized material with an average diameter of D _m , holders oriented in this annular zone with attachment points of sprayed parts, n-rods rotating at an angular speed w ₁ in one direction with n-holders fixed at their ends, reduction unit rotating with an angular velocity w ₂ in the other direction on which the decree These rods are placed with equal angular pitch and at the same distance 1/2 · D _w from its axis of rotation. To improve the spraying conditions of coatings on parts having the shape of a body of revolution, in particular hemispherical, the plane in which the centers of the attachment points of the parts and, accordingly, the parts themselves are inclined to the axis of symmetry of the flow of vaporized material at an angle α with the intersection of the axis of rotation of the specified reduction unit and axis of symmetry of the material flow at a point lying in this plane. In this case, an elliptical trajectory of the movement of the attachment points of the parts relative to the plane perpendicular to the axis of symmetry of the flow of evaporated material is formed. Obviously, this trajectory should be within the annular zone of the flow of material evaporated from the target.

However, the prototype installation has such disadvantages as limited technical capabilities and the difficulty of obtaining coatings that meet the requirements of precision instrumentation, which is determined by the following factors:

1. The low quality of the coatings, since the inclination of the plane in which the centers of the sprayed parts lie at an angle α to the axis of symmetry of the flow of material evaporated from the target leads to the fact that the formed elliptical trajectory of the movement of parts relative to the annular zone of this flow is located, at best, over the entire width this zone. And within this zone - from its inner part to the outer - there may be instability in the flow of material. Those. to increase the efficiency of the spraying process due to the orientation of the parts does not allow the concomitant uneven spraying conditions in different parts of the annular zone.

2. Limited installation and spraying capabilities, as the angle of inclination - angle α - is limited by the width of the annular zone of the flow of material evaporated from the target, on the basis that the exit of the trajectory of movement of parts outside this zone is extremely undesirable, introduces uncertainty into the coating spraying process in terms of its quality and repeatability of results. This is especially important for precision parts such as bearings and flanges of a gas-dynamic bearing of a float gyroscope, to which, including magnetron sputtering coatings, accuracy requirements are set at tenths and hundredths of a micrometer.

3. Possible heterogeneity of the functional characteristics of the coating, which is unacceptable for a wear-resistant coating of titanium nitride on the working hemispherical surfaces of the bearings and flanges of the gas-dynamic bearing. This is determined by the fact that during magnetron sputtering, the identity of the sputtering conditions is associated, inter alia, with the chemical reaction between nitrogen and titanium evaporated from the target with the formation of titanium nitride. A change in the concentration or flux density of the vaporized material can lead to deviations from the stoichiometry of the resulting coating and impair its properties and, as a result, the characteristics of the gas-dynamic bearing.

The objective of the present invention is to expand the technical capabilities of the installation, as well as improving the quality and functional characteristics of sprayed coatings.

According to the invention, this problem is solved in that the holders in which the sprayed parts are installed are made in the form of cantilever elements with a shift of the centers of the attachment points of the parts relative to the axis of the rod by the value L associated with the diameter D _{w by the} ratio D _w / L = 2 (1 + sinα ) / (1-sinα), the diameter D _w , on which the rods are placed, is given from the expression D _w · sinα <D _m <O _w , the number of rods n is selected as a multiple of four under the condition n <180 ° / arcsin (L / 2D _w ), and the ratio of the angular velocities w ₁ and w _{2 is} determined from the equality w ₁ = 1/2 · w ₂ . Moreover, for every four rods arranged in a circle with a diameter D _W with an angular pitch of 90 °, for one pair of opposing rods located on the major axis of the elliptical trajectory of their movement, the direction of displacement L is oriented to the center of the ellipse, and for the second pair of opposing rods located on the minor axis of this trajectory, the direction of displacement L is oriented in the direction opposite to the center of the specified ellipse.

The invention is illustrated by drawings, in which Fig. 1 shows the main structural intracameral elements of the installation for spraying and shows their layout and relative orientation, Fig. 2 shows the kinematics of movements of the positions of the sprayed parts in the annular zone of the material being sprayed from the target in a plane perpendicular to the axis of the flow of the sprayed material, and figure 3 is a diagram of the operation of the installation.

In Fig.1,2 and 3 are indicated:

1 - reduction unit rotating with an angular velocity w ₂ around its axis 0.02;

2 - rods of quantity n, rotating with an angular speed w ₁ in the direction opposite to the rotation of the reduction unit 1, and placed on this block with equal angular pitch at the same distance from its axis of rotation O ₁ O ₂ ;

3 - holders with attachment points for sprayed parts mounted on rods 2 and made in the form of cantilever elements with a shift of the center of each attachment point for parts relative to the axis of the rod by L;

4 - sprayed parts, rigidly fixed in the attachment points of the holders 3;

5 - target spray;

6 - flow of material evaporated (sprayed) from the target atomizer 5, forming an annular zone with an average diameter of D _m ;

7 - the plane in which the centers of the attachment points of the parts 4 on the cantilever elements of the holders 3 lie;

8 is an elliptical trajectory of the movement of the positions of the rods 2 at the attachment point of the holders 3 relative to a plane perpendicular to the axis of symmetry O3O4 of the flow of vaporized material 6 when the reduction unit 1 rotates about its axis O ₁ O ₂ ;

9 - circular path of movement of the sprayed parts 4 relative to the plane perpendicular to the axis of symmetry O ₃ O _{4 the} flow of sprayed material 6 when the reduction unit 1 rotates about its axis with a speed of w ₂ and the rods 2 rotate in the opposite direction with a speed of w ₁ at a ratio of the indicated speeds, defined by the expression w ₁ = 1/2 · w ₂ ;

D _W - the diameter on which the rods 2 are located on the reduction unit 1;

α is the angle of inclination of the plane 7, in which the centers of the attachment points of the parts 4 lie to the axis of symmetry O ₃ O _{4 of the} flow of the sprayed material 6;

D _m - the average diameter of the annular zone 6 of the stream of sprayed material;

O is the point of intersection of the axis of rotation O ₁ O ₂ of the reduction unit 1 and the axis of symmetry O ₃ O _{4 of the} flow of the sprayed material 6, lying in the plane 7;

α is the angle of inclination of the plane 7, in which the centers of the attachment points of the parts 4 lie to the axis of symmetry O ₃ O _{4 of the} flow of the sprayed material 6;

To _b and K _m - the position of the rods 2 on the major and minor axis of the elliptical trajectory 8;

D _b and D _m - the position of the parts 4 on the annular path 9 at points corresponding to the location of the rods 2 in the positions of K _b and K _m ;

K and D are the positions of the rod and the part when the reduction unit 1 rotates at a speed of w ₂ by an angle ψ and rotates, while the rod is in the opposite direction with a speed of w ₁ ;

2ψ is the angle of rotation of the cantilever element relative to the radius OK of the trajectory 9 when the reduction unit 1 is rotated by an angle ψ;

The process of spraying coatings on the installation of the presented design is as follows.

The sprayed parts 4 (hemispherical bearings and flanges of the gas-dynamic bearing of the float gyroscope) are rigidly fixed in the attachment points of the holders 3 mounted on the ends of the rods 2, which are placed with equal angular pitch and at the same distance 1/2 · D _w from the axis of rotation of the reduction unit 1, those. on a circle of diameter D _W , the center of which lies on the axis of rotation of this block. The reduction unit contains elements that specify the synchronous rotation of the rods 2 with the same speed w ₁ . All rods 3 are made of equal length, and the holders 3 are of the same (for the same type of parts) configuration, which determines the equal use of the terms “center of attachment parts” and “geometric center of the part”.

These centers lie in the same plane 7 and, as indicated, are equidistant from the axis of rotation O ₁ O ₂ of the reduction unit 1. Using rotary nodes (not shown in FIGS. 1, 2 and 3), plane 7 is oriented to the axis of symmetry O ₃ O ₄ the flow of the sprayed material 6 at an angle α, the value of which is determined by the specific requirements for the coating formed on the parts, and is fixed in this position (Fig. 1).

When rotated through an angle α in a projection onto a plane perpendicular to the axis of symmetry O ₃ O _{4 of the} stream of sprayed material 6, a circle with a diameter D _w transforms into an elliptical trajectory 8 of the positions of the rods 2 at the attachment point of the holders 3 (FIG. 2) . The parameters of this ellipse can be represented as follows: the major axis 2α will be equal to the diameter D _W (since the center of the circle with a diameter D _W lies on the axis O ₃ O ₄ ), and the small axis 2b is determined by the relation

2b = D _W · sinα.

To implement the adjustment of the trajectory of the movement of parts 4 so that it is a circle with a diameter of D _m in the projection onto the plane perpendicular to the axis of symmetry O ₃ O ₄ , it is necessary to fulfill the initial conditions associated with the choice of diameters D _m and D _w based on obvious ratios D _m <D _W and D _W · sinα <D _m or in general form (figure 2):

$$D_w\cdot \sin \alpha <D_m<D_w.(\mathrm{one})$$

It should be noted that in practice it is preferable to vary the value of D _W , taking a given value of D _m

Taking into account, as indicated above, the need to carry out the multi-position spraying process, it is most efficient and rational to choose the number of rods n multiple of four, which fully provides the condition for the simultaneous spraying of several sets of parts, for example, a gas-dynamic bearing. In this case, the number of rods n is limited by the design parameters of other elements — the value of the diameter D _w and the offset value L. Obviously, the chord connecting the points corresponding to two adjacent rods on a circle with a diameter D _w should be less than L, from which the expression

$$n<{180}^{\circ }/\arcsin \left(L/2D_w\right).(2)$$

Groups of four rods can be distinguished, in each of which the rods are 90 ° offset in angle. By arranging for such a group two opposing rods on the major axis 2a of the elliptical trajectory 8, and two other opposing rods on the minor axis 2b of this trajectory, it is possible to determine a pattern in which for the indicated positions of the rod rods the parts will be placed on a circle 9 corresponding to the average diameter D _m the flow of the sprayed material 6. This is realized by means of holders 3, in which the sprayed parts 4 are installed, in the form of cantilever elements with an offset of each center of the part fixing unit (and the part 4 itself) but the axis of the rod 2 by L. The rotation of the reduction unit 1 by 90 ° with the ratio of the angular velocities w ₁ and w _{2 of the} rotation of the rods 2 and the reduction unit 1, defined by the expression w ₁ = 1/2 · w ₂ , will cause the rod to move from position K _b to position K _m (figure 2), and the details from position D _b to position D _m . Moreover, if in position D _{b the} offset by the amount L is oriented to the center O of the ellipse, then in position D _{m the} holder 3 will rotate 180 ° and the direction of the part’s displacement will be directed to the side opposite to the center of the ellipse. In fact, when moving the rod 2 along an elliptical path, the part 4 will move along an annular path 9 that coincides with a circle with a diameter of D _m . Obviously, this requires certain conditions related, in addition to the ratio w ₁ = 1/2 · w ₂ , with dimensional parameters. These parameters are determined from the following expressions (figure 2):

D _m = D _W -2L - along the axis 2a of the ellipse and D _m = D _W · sinα + 2L · sinα - along the axis 2b of the ellipse,

whence D _w -2L = D _w · sinα + 2L · sinα or D _w (1-sinα) = 2L (1 + sinα), or the practical implementation of such a scheme should be expressed by the relation

$$D_w/L=2\left(\mathrm{one}+\sin \alpha \right)/\left(\mathrm{one}-\sin \alpha \right).(3)$$

The specified ratio meets the condition for the arrangement of parts 4 and rods 2 in the required positions for the major and minor axes of the ellipse. The formal proof that for any rotation angle ψ the rods 2 will be on an elliptical trajectory 8, and the details 4 on a circular path 9, is quite clear (Fig. 2): when the reduction unit 1 is rotated by an arbitrary angle ψ, the holder 3 rotates by an angle 2ψ (since w ₁ = 1/2 / w ₂ ). In this case, the coordinates of the position K are described using expressions, which, by definition, are the parametric equations of the ellipse -

$$K_x=\left(\mathrm{one}/2D_m+L\right)\cos \psi ,(\mathrm{four})$$

$$K_y=\left(\mathrm{one}/2D_m-L\cdot \sin \alpha \right)\sin \psi ,(5)$$

and since, taking into account the fact that, relative to the plane in which the trajectory 9 with diameter DM is located, the position D moves the rod K along an ellipse whose parameters are determined by the angle α, the projections of the CD segment on the x and y axes can be represented as expressions (by the construction of figure 2)

$$L_x=L\cos \psi ,(6)$$

$$L_y=L\sin \alpha \sin \psi ,(7)$$

then, determining the coordinates of the position D as

$$D_x=K_x-L_x,(8)$$

$$D_y=K_y-L_y(9)$$

and substituting formulas (4) and (6) into expression (8), and formulas ((5) and (7) into expression (9), we obtain finite dependences, which are circle equations

$$D_x={\mathrm{TO}}_x-L_x=\left(\mathrm{one}/2D_m+L\right)\cos \psi -L\cos \psi =\mathrm{one}/2D_m\cos \psi ,(\mathrm{eleven})$$

$$D_y={\mathrm{TO}}_y-L_y=\left(\mathrm{one}/2D_m+L\cdot \sin \alpha \right)\sin \psi -L\sin \alpha \sin \psi =\mathrm{one}/2D_m\sin \psi .(12)$$

Thus, for every four rods arranged in a circle with a diameter D _W with an angular pitch of 90 °, for one pair of opposing rods located on the major axis of the elliptical trajectory of their movement, the direction of displacement L is oriented to the center of the ellipse, and for the second pair of opposing cantilever elements, lying on the minor axis of this trajectory, the indicated direction is oriented in the direction opposite to the center of the specified ellipse. This orientation during the design of the spraying process, taking into account expressions (1-3) and the ratio w ₁ = 1/2 · w ₂ provides a given trajectory of movement of the sprayed parts, corresponding to the average flow diameter of the evaporated material.

Next, the chamber of the installation for spraying is evacuated, the parts are heated to the required temperature, which ensures sufficient adhesion, the rotation drives (not shown) of the reduction unit and rods are turned on, and then the spraying process is carried out according to the specified program.

Thus, the proposed design allows the process of magnetron sputtering of thin-film coatings on precision parts due to the formation of the required configuration and layout of the elements placed inside the chamber of the spraying module in series:

- setting the angle of inclination α of the sprayed parts with respect to the flow of material evaporated from the target, which is the primary factor of the process and is due to the configuration of the sprayed surface and the requirements for the sprayed coating;

- determining the range of values for the diameter D _W on which the rods are placed using the expression (1) D _W · sinα <D _m <D _W , taking into account that the value of D _m is given;

- specifying the value of D _{W the} coordinated choice of the quantities n, D _W and L, together considering expressions (2) and (3):

n <180 ° / arcsin (L / 2D _W ) and D _W / L = 2 (1 + sinα) / (1-sinα);

- orienting for one pair of opposing rods located on the major axis of the elliptical trajectory of their movement, for each group of four rods located in a circle with a diameter D _w with an angular pitch of 90 °, the direction of displacement L to the center of the ellipse, and for the second pair of opposing rods, located on the minor axis of this trajectory - in the direction opposite to the center of the specified ellipse;

- setting the ratio of the rotational speeds of the reduction unit on which the rods are located, and the rods themselves from the condition w ₁ = 1/2-w ₂ .

Ultimately, the required conditions for the movement of the sprayed parts around a circle with a diameter of D _{m are} provided, which is confirmed by expressions (11) and (12), and which corresponds to the most effective scheme of the coating spraying process on precision parts.

The installation design under consideration is intended primarily for spraying coatings on precision parts of precision instrumentation products, in particular gyroscopic devices. The proposed installation was tested in the manufacture of bearings and flanges of a gas-dynamic bearing of a two-stage float gyro to form a thin-film wear-resistant coating of titanium nitride on their hemispherical working surfaces. On four sets of parts (8 spraying positions, i.e., the number of rods n = 8), a coating with a thickness of 1.2 to 2.4 μm was obtained with both a permissible thickness deviation of 0.05 μm and a given monotonously varying thickness within the thickness range of 0.1-0.4 microns. At the same time, tests showed the complete identity of the tribological properties and structural characteristics of the coating on all parts sprayed in one cycle.

Feasibility of the invention is to improve the quality and functional characteristics of sprayed coatings. In addition, expanding technical capabilities for the assembly of parts and assemblies of precision instrumentation products, which can improve the operational parameters of these products.

Claims (1)

Installation for spraying coatings on precision parts of gyro device assemblies, including a vacuum chamber, a spray target for creating an annular zone of flow of vaporized material with an average diameter of D _m , holders with fasteners for spraying parts mounted on n rods rotating with an angular speed w ₁ in one direction , the reduction unit rotates with an angular velocity w ₂ in the other direction in which said rods are arranged with an equal angular pitch and at the same distance 1/2 · D _m from its axis of rotation, wherein the glossiness in which the centers of the attachment points of the parts lie is inclined to the axis of symmetry of the flow of the sprayed material at an angle α with the intersection of the axis of rotation of the specified reduction unit and the axis of symmetry of the flow of sprayed material at a point lying in this plane, with the formation of an elliptical trajectory of the rods relative to the plane, perpendicular to the axis of symmetry of the flow of the sprayed material, characterized in that the holders in which the sprayed parts are installed are made in the form of cantilever elements with a displacement of centers the attachment points of the parts relative to the axis of the rod by the amount L associated with the diameter D _{W by the} ratio D _W / L = 2 (1 + sinα) / (1-sinα), the diameter D _W , on which the rods are placed, is given from the expression D _W · sinα <D _m <D _w , the number of rods n is a multiple of four under the condition n <180 ° / arcsin (L / 2D _w ), and the ratio of the angular velocities w ₁ and w _{2 is} determined from the equality w ₁ = 1/2 · w ₂ , for this is for every four rods located around a circle with a diameter D _w with an angular pitch of 90 °, for one pair of opposing rods located on the major axis of the elliptical trajectory of their movement, the direction of of the joint L is oriented towards the center of the ellipse, and for the second pair of opposing rods located on the minor axis of this trajectory, the direction of the displacement L is oriented to the side opposite to the center of the specified ellipse.

Images